QuickLinks -- Click here to rapidly navigate through this document

Filed Pursuant to Rule 424(b)(3)
File No. 333-89596

The information in this prospectus supplement is not complete and may be changed. This prospectus supplement is not an offer to sell these securities and is not soliciting offers to buy these securities in any state where such offer or sale is not permitted.

PRELIMINARY PROSPECTUS SUPPLEMENT Subject to completion September 24, 2002

(To Prospectus dated July 12, 2002)

5,000,000 Shares

Common Stock

We are offering all of the 5,000,000 shares of common stock offered by this prospectus supplement.

Our common stock is traded on the Nasdaq National Market under the symbol "TELK." On September 23, 2002, the last reported sale price of our common stock on the Nasdaq National Market was $11.65 per share.

Investing in our common stock involves a high degree of risk. Before buying any shares you should read the discussion of material risks of investing in our common stock in "Risk factors" beginning on page S-7 of this prospectus supplement.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities, or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

	Per share	Total
Public offering price	$	$
Underwriting discounts and commissions	$	$
Proceeds, before expenses, to us	$	$

The underwriters may also purchase from us up to an additional 750,000 shares of our common stock at the public offering price, less the underwriting discounts and commissions, to cover over-allotments, if any, within 30 days of the date of this prospectus supplement.

The underwriters are offering the shares of our common stock as described in "Underwriting." Delivery of the shares will be made on or about                          , 2002.

UBS Warburg
	Wachovia Securities
		Legg Mason Wood Walker                   Incorporated
			Needham & Company, Inc.

You should rely only on the information contained or incorporated by reference in this prospectus supplement and the accompanying prospectus. We have not authorized anyone to provide information different from that contained or incorporated by reference in this prospectus supplement or the accompanying prospectus. Neither the delivery of this prospectus supplement nor the sale of common stock means that information contained or incorporated by reference in this prospectus supplement or the accompanying prospectus is correct after the date of this prospectus supplement. These documents are not an offer to sell or solicitation of an offer to buy these shares of common stock in any circumstance under which the offer or solicitation is unlawful.

TABLE OF CONTENTS

Prospectus supplement
Prospectus supplement summary	S-1
Risk factors	S-7
Use of proceeds	S-16
Price range of common stock	S-17
Dividend policy	S-17
Capitalization	S-18
Dilution	S-19
Underwriting	S-20
Legal matters	S-22
Base prospectus
About this prospectus	1
Telik	2
The securities we may offer	2
Forward-looking information	4
Ratio of earnings to fixed charges	4
Use of proceeds	5
Description of capital stock	5
Description of debt securities	9
Description of warrants	15
Legal ownership of securities	17
Plan of distribution	21
Legal matters	23
Experts	23
Where you can find more information	23

Telik, Telik Logo and TRAP are trademarks of Telik, Inc. This prospectus supplement also refers to trademarks and tradenames of other companies.

Prospectus supplement summary

This summary does not contain all of the information that you should consider before investing in our common stock. You should read this entire prospectus supplement and the accompanying prospectus carefully, including the "Risk factors," the financial statements and other information incorporated by reference in this prospectus supplement and the accompanying prospectus, before making an investment decision.

BUSINESS OVERVIEW

We are a biopharmaceutical company working to discover, develop and commercialize innovative small molecule drugs to treat serious diseases, including cancer and diabetes. Our most advanced product development programs include TLK286, which we expect to enter a pivotal phase 3 trial beginning in the first quarter 2003; TLK199, which is in a phase 1-2a trial; and TLK19781, which is in preclinical safety studies prior to clinical testing.

TLK286, our lead product candidate, is a small molecule tumor-activated cancer drug designed to treat cancers that are resistant to standard chemotherapy drugs. TLK286 works by binding to glutathione S-transferase P1-1, or GST P1-1, a protein that is elevated in many human cancers, including ovarian and non-small cell lung cancer. GST P1-1 levels are often further elevated following treatment with many standard chemotherapeutic drugs and this elevation is associated with the development of resistance to these drugs. When TLK286 binds to GST P1-1 inside a cancer cell, a chemical reaction occurs, releasing a fragment of TLK286 that causes programmed cancer cell death, or apoptosis. We initiated phase 2 clinical trials in colorectal cancer in March 2001, in ovarian cancer in May 2001, in non-small cell lung cancer in June 2001 and in breast cancer in March 2002. Interim results of the ovarian and non-small cell lung cancer trials were presented at the American Society of Clinical Oncology annual meeting in May 2002, and we plan to present the final results for these trials, and for the phase 2 colorectal trial, in November 2002. As a result of our recent pre-phase 3 meeting with the FDA in September 2002, we plan to initiate pivotal phase 3 clinical trials of TLK286 for the treatment of ovarian and non-small cell lung cancer. We have retained worldwide commercialization rights for TLK286.

TLK199, our second product candidate, is a small molecule bone marrow stimulant being developed for the treatment of blood disorders associated with low white blood cell levels, or neutropenia. Neutropenia is associated with myelodysplastic syndrome, or MDS, a form of pre-leukemia for which there is no approved therapy. Neutropenia is also a toxic side effect of cancer chemotherapy. TLK199 activates the same signaling pathway that is activated by granulocyte-colony stimulating factor, or G-CSF, known as Neupogen, which is marketed for the treatment of neutropenia associated with cancer chemotherapy. TLK199 inhibits the activity of GST P1-1. In preclinical tests, the inhibition of GST P1-1 by TLK199 has been shown to stimulate white blood cell production, similar to the results observed following treatment with G-CSF. This effect may provide the basis for more effective treatment of MDS and other conditions associated with neutropenia. We filed an Investigational New Drug, or IND, application for TLK199 in December 2001 and initiated a phase 1-2a clinical trial in MDS in April 2002. We have retained worldwide commercialization rights for TLK199.

In July 2002, we selected TLK19781 as our next product candidate to be advanced into clinical development. TLK19781 is a proprietary, orally active small molecule insulin receptor activator for the potential treatment of Type 2 diabetes and other conditions related to insulin resistance. In preclinical studies, including those presented at the June 2002 American Diabetes Association meeting, orally administered TLK19781 has been shown to activate the insulin receptor, leading to enhanced glucose transport into muscle and liver cells and lowering of blood sugar levels in several animal models of diabetes. We expect to file an IND application with the FDA for TLK19781 in 2003. We have retained worldwide commercialization rights for TLK19781, except in Japan and certain other Asian countries.

We discovered all of our product candidates using our proprietary technology, Target-Related Affinity Profiling, or TRAP, which enables the rapid and efficient discovery of small molecule product candidates. TRAP exploits a fundamental property of all drugs, which is their selective interaction with proteins. By developing a profile of how small molecule chemicals interact with a reference panel of proteins, we are able to identify compounds active against disease-related protein targets much faster than with alternative technologies.

S-1

PRODUCT PIPELINE SUMMARY

Our efforts are concentrated in three therapeutic areas: cancer, diabetes and inflammatory diseases. We periodically reevaluate and prioritize our research programs. The following table summarizes key information about our current product pipeline:

Product candidate	Clinical indication (dosage)	Development status	Commercialization rights
Cancer
TLK286 Targeted chemotherapeutic drug	Ovarian cancer (3 weekly) Non-small cell lung cancer (3 weekly)	Phase 3—planning Phase 3—planning	Worldwide
	Ovarian cancer (3 weekly)	Phase 2—enrollment completed
	Non-small cell lung cancer (3 weekly)	Phase 2—enrollment completed
	Colorectal cancer (3 weekly)	Phase 2—enrollment completed
	Ovarian cancer (weekly)	Phase 2—ongoing
	Non-small cell lung cancer (weekly)	Phase 2—ongoing
	Breast cancer (weekly)	Phase 2—ongoing
	Advanced cancers (weekly)	Phase 1—completed
	Advanced cancers (3 weekly)	Phase 1—completed
TLK199 Bone marrow stimulant	MDS Neutropenia associated with cancer chemotherapy	Phase 1-2a—ongoing Phase 1-2a—planning	Worldwide
GST inhibitor	Cancer	Small molecule inhibitors discovered	Worldwide
IGF-1 inhibitor	Cancer	Small molecule inhibitors discovered	Worldwide
Raf kinase inhibitor	Cancer	Small molecule inhibitors discovered	Worldwide
DNA methyl transferase inhibitor	Cancer	Small molecule inhibitors discovered	Worldwide
Diabetes
TLK19781 Insulin receptor activator	Type 2 diabetes	Orally active in diabetes animal models Preclinical and safety assessment ongoing	Worldwide except Japan and certain other Asian countries
Inflammatory disease
MCP-1 antagonist	Rheumatoid arthritis, asthma, atherosclerosis, multiple sclerosis, cancer	Small molecule inhibitors optimized Orally active in arthritis models	North and South America and jointly in Europe

S-2

RECENT DEVELOPMENTS

TLK286—tumor activated cancer drug

TLK286 has been evaluated as a single agent in more than 270 cancer patients in eight clinical trials. Results from these trials indicate that TLK286 is generally well-tolerated, with mostly mild to moderate side effects, particularly when compared to the side effects and toxicities of standard chemotherapeutic drugs. This tolerability profile may be an important clinical advantage for TLK286. Since combination drug regimens are commonly used in cancer treatment, the tolerability profile of TLK286 and its lack of overlapping toxicities with standard chemotherapeutic drugs suggest TLK286 may be well suited for inclusion into combination chemotherapy regimens.

In May 2002, at the American Society of Clinical Oncology annual meeting, we announced positive interim results from the multicenter phase 2 trials of TLK286 in ovarian and non-small cell lung cancer. In the ovarian cancer trial, TLK286 demonstrated significant single agent antitumor activity, including multiple objective tumor responses and prolongation of expected survival in patients who were unresponsive to standard treatments. In the non-small cell lung cancer trial, TLK286 treatment was associated with disease stabilization and an improvement in expected survival.

Based on favorable safety results and evidence of clinical activity observed in our phase 1 trial using TLK286 administered on a weekly dose schedule, we initiated three additional phase 2 trials using the weekly dosing schedule. In March 2002, we initiated a phase 2 trial of TLK286 in patients with locally advanced or metastatic breast cancer, and in June 2002, we initiated phase 2 trials in ovarian cancer and non-small cell lung cancer using the weekly dosing schedule. In addition, in the fourth quarter 2002, we plan to initiate combination phase 1-2a trials using TLK286 with standard chemotherapeutic drugs.

As a result of our recent pre-phase 3 meeting with the FDA in September 2002, we plan to initiate our first phase 3 pivotal trial with TLK286 in chemotherapy resistant ovarian cancer in the first quarter 2003. We expect to initiate additional pivotal phase 3 trials in ovarian cancer and non-small cell lung cancer.

TLK199—bone marrow stimulant

The phase 1-2a clinical trial in patients with MDS is ongoing and is anticipated to enroll 35 patients in a dose escalating safety study and to measure markers of clinical activity. We expect to initiate an additional phase 1-2a trial in neutropenia associated with cancer chemotherapy.

TLK19781—insulin receptor activator

In July 2002, we selected TLK19781 as our next product candidate to be advanced into clinical development. Assuming successful completion of preclinical safety studies, we plan to file an IND application in 2003 to initiate clinical trials of TLK19781 in Type 2 diabetes.

OUR STRATEGY

Our goal is to become a leading pharmaceutical company focused on discovering, developing and commercializing innovative small molecule drugs to treat serious diseases including cancer, diabetes and inflammatory diseases. We intend to achieve this goal by pursuing the following strategies:

Develop small molecule drugs for major disease areas

We intend to discover and develop small molecule drugs in cancer, diabetes and inflammatory diseases. Current treatments for these diseases have limited efficacy, and the number of patients with these diseases has been increasing due primarily to the aging population. The advantages of small molecule drugs include relative ease of manufacturing and administration, the potential for oral dosing and applicability to a wider range of disease targets, including those inside the cell.

Retain commercial rights to our product candidates

We will seek to retain significant commercial rights to our product candidates by conducting clinical development activities at least through initial proof of efficacy in humans. Since the development process for cancer drugs is relatively efficient and well defined, the cost and time required to bring new drugs to market is significantly less than that required for other therapeutic categories, permitting us to retain commercialization rights through completion of clinical trials. In disease areas that require larger and longer clinical trials, such as diabetes, we will share the risks and costs of development by partnering these programs before completion of pivotal trials, which we expect may require granting commercialization

S-3

rights to our collaborators. Our goal is to develop and commercialize our cancer product candidates in North America. As appropriate, we will establish collaborations with multinational pharmaceutical companies to assist in the commercialization of our product candidates.

Use TRAP technology to sustain a pipeline of drug candidates

Our proprietary TRAP drug discovery platform allows us to rapidly and efficiently identify small molecules active against potential disease targets. We have used and will continue to use this platform to provide a pipeline of future product development candidates generated internally or through collaborations. For example, through a collaboration with the University of Arizona Cancer Center, we are applying TRAP to identify novel compounds active against a wide range of potential cancer targets. We plan to secure additional academic partners for the use of TRAP technology. We also have entered into corporate collaborations to assist our partners in identifying product candidates for promising therapeutic targets.

S-4

The offering

Common stock offered	5,000,000 shares
Common stock to be outstanding after the offering	32,983,105 shares
Nasdaq National Market Symbol	TELK
Use of proceeds	We intend to use the net proceeds of this offering to fund clinical trials of our lead product candidates, TLK286 and TLK199, to fund the advancement of TLK19781 into clinical development and for other research and development and general corporate purposes.

The number of shares of common stock to be outstanding after the offering is based on the number of shares outstanding as of August 31, 2002 and excludes:

•

4,558,267 shares of common stock underlying options outstanding as of August 31, 2002 at a weighted average exercise price of $6.74 per share; and

•

1,450,158 shares available for issuance or future grant under our 2000 Equity Incentive Plan, 418,223 shares available for issuance under our 2000 Employee Stock Purchase Plan and 181,459 shares available for issuance or future grant under our 2000 Non-Employee Directors' Stock Option Plan, as of August 31, 2002.

Unless otherwise stated, all information contained in this prospectus supplement and the accompanying prospectus assumes that the underwriters do not exercise their over-allotment option.

S-5

Summary financial data

The table below presents summary statement of operations and balance sheet data. The summary financial data for the years ended December 31, 1999 through December 31, 2001 are derived from our audited financial statements for those periods. We derived the summary financial data as of June 30, 2002 and for the six months ended June 30, 2001 and 2002 from our unaudited financial statements. The unaudited financial statement data includes, in our opinion, all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair presentation of our financial position and results of operations for these periods. Operating results for the six months ended June 30, 2002 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2002. This information is only a summary. You should read it in conjunction with our historical financial statements and related notes contained in our annual reports, quarterly reports and other information on file with the SEC. For more details on how you can obtain our SEC reports and other information, you should read the section of the accompanying prospectus entitled "Where you can find more information" beginning on page 23. The pro forma net loss per share amounts and shares used in computing pro forma net loss per share amounts are calculated as if all of our shares of convertible preferred stock were converted into shares of common stock on the date of their issuance. The as adjusted balance sheet data gives effect to the sale of 5,000,000 shares of our common stock in this offering at an assumed public offering price of $14.12 per share, after deducting the underwriting discounts and estimated offering expenses.

	Year ended December 31,						Six months ended June 30,
Statement of operations data	1999		2000		2001		2001		2002
	(In thousands, except per share data)
Contract revenue from collaborations	$4,237		$2,721		$1,788		$861		$745
Other revenues	—		75		83		33		42
Total operating expenses	11,699		16,790		22,452		9,917		15,588
Net loss	(7,064	)	(12,557	)	(18,566	)	(7,878	)	(14,324	)
Deemed dividend to preferred stockholders	—		(4,667	)	—		—		—
Net loss allocable to common stockholders	$(7,064	)	$(17,224	)	$(18,566	)	$(7,878	)	$(14,324	)
Net loss per common share, basic and diluted	$(3.21	)	$(1.70	)	$(0.81	)	$(0.35	)	$(0.52	)
Weighted average shares used in computing net loss per common share, basic and diluted	2,204		10,128		22,840		22,708		27,766
Pro forma net loss per common share, basic and diluted	$(0.47	)	$(0.94	)
Weighted average shares used in computing pro forma net loss per common share, basic and diluted	14,879		18,254

	June 30, 2002
Balance sheet data	Actual		As adjusted
	(In thousands)
Cash, cash equivalents and investments	$42,175		$108,139
Working capital	34,635		100,599
Total assets	44,724		110,688
Long-term liabilities	29		29
Accumulated deficit	(96,831	)	(96,831	)
Total stockholders' equity	$37,782		$103,746

S-6

Risk factors

Investing in our common stock involves a high degree of risk. In addition to the other information in this prospectus supplement, you should carefully consider the risks described below before purchasing our common stock. If any of the following risks actually occur, our business could be materially harmed, and our financial condition and results of operations could be materially and adversely affected. As a result, the trading price of our common stock could decline, and you might lose all or part of your investment.

We have a history of net losses, which we expect to continue for at least several years. We will never be profitable unless we develop, and obtain regulatory approval and market acceptance of, our product candidates.

Due to the significant research and development expenditures required to develop our TRAP technology and identify new product candidates, and the lack of any products to generate revenue, we have not been profitable and have generated operating losses since we were incorporated in 1988. As of June 30, 2002, we had an accumulated deficit of $96.8 million. We expect to incur losses for at least the next several years and expect that these losses will actually increase as we expand our research and development activities and incur significant clinical testing costs. These losses, among other things, may cause our stockholders' equity and working capital to decrease in the future. To date, we have derived substantially all of our revenues, which have not been significant, from project initiation fees and research reimbursement paid pursuant to existing collaborative agreements with third parties and achievement of milestones under current collaborations. We expect that this trend will continue until we develop, and obtain regulatory approval and market acceptance of, our product candidates. We cannot assure you when, if ever, we will receive product revenue, if any, sufficient to become profitable.

All of our product candidates are in research and development. If clinical trials of TLK286 and TLK199 are delayed or unsuccessful or if we are unable to complete the preclinical development of our diabetes or other preclinical product candidates, our business may be adversely affected.

Preclinical testing and clinical trials are long, expensive and uncertain processes. It may take us or our collaborators several years to complete this testing, and failure can occur at any stage of the process. Success in preclinical testing and early clinical trials does not ensure that later clinical trials will be successful. A number of companies in the pharmaceutical industry, including biotechnology companies, have suffered significant setbacks in advanced clinical trials, even after promising results in earlier trials.

In July 2002, we selected TLK19781, one of a family of orally active small molecule insulin receptor activators that we are developing for potential treatment of diabetes, for advancement into IND-stage development. In April 2002, we initiated a phase 1-2a clinical trial for TLK199. Our success depends, in part, on our ability to complete preclinical development of our diabetes or other preclinical product candidates, and take them through early clinical trials.

TLK286 has to date been evaluated in phase 1 and phase 2 clinical trials. It has not been tested in the larger, controlled phase 3 trials that are generally required prior to regulatory approval. As a result of our recent pre-phase 3 meeting with the FDA, we expect to initiate pivotal phase 3 trials of TLK286 in ovarian and non-small cell lung cancers. These trials would test TLK286 against a control arm consisting of currently established standard drug treatments for these cancers. Changes in standards of care during our phase 3 trials may cause us to, or the FDA may require us to, perform additional

S-7

clinical testing of TLK286 against a different control arm prior to filing a New Drug Application for marketing approval.

Any clinical trial may fail to produce results satisfactory to the FDA. Preclinical and clinical data can be interpreted in different ways, which could delay, limit or prevent regulatory approval. Negative or inconclusive results or adverse medical events during a clinical trial could cause a clinical trial to be repeated or a program to be terminated. We typically rely on third-party clinical investigators to conduct our clinical trials and, as a result, we may face additional delays outside our control. We plan to engage a contract research organization, or CRO, to facilitate the administration of our phase 3 trials of TLK286. Dependence on a CRO will subject us to a number of risks. Delays in identifying and engaging a CRO may result in delays in the initiation of our phase 3 trials. We may not be able to control the amount and timing of resources the CRO may devote to our trials. Should the CRO fail to administer our phase 3 trials properly, regulatory approval, development and commercialization of TLK286 will be delayed.

We do not know whether planned clinical trials will begin on time or whether any of our ongoing clinical trials will be completed on schedule, or at all. We do not know whether any clinical trials will result in marketable products. Typically, there is a high rate of attrition for product candidates in preclinical and clinical trials. We do not anticipate that any of our products will reach the market for at least several years.

We believe that our ability to compete depends, in part, on our ability to use our proprietary TRAP technology to discover, develop and commercialize new pharmaceutical products. We may not be competitive if we are unable to utilize our TRAP technology or if the technology proves ineffective.

TRAP, our proprietary drug discovery technology, is a relatively new drug discovery method that uses a protein panel of approximately 20 proteins selected for their distinct patterns of interacting with small molecules. This panel may lack essential types of interactions that we have not yet identified, which may result in our inability to identify active compounds that have the potential to be developed into commercially viable drugs.

If we are unable to continue to identify new product candidates using TRAP technology, we may not be able to maintain our product pipeline and develop commercially viable drugs.

If we are unable to raise adequate funds in the future, we will not be able to continue to fund our operations, research programs, preclinical testing and clinical trials to develop our products.

The process of carrying out the development of our own unpartnered products to later stages of development and developing other research programs to the stage that they may be partnered will require significant additional expenditures, including the expenses associated with preclinical testing, clinical trials and obtaining regulatory approval. As a result, we will require additional financing to fund our operations. We have recently obtained a credit line to finance some of our equipment and leasehold improvements, if any, under which we may borrow up to approximately $2.5 million. We do not know whether additional financing will be available when needed, or that, if available, we will obtain financing on terms favorable to our stockholders. We have expended substantial amounts of cash to date and expect capital outlays and operating expenditures to increase over the next several years as we expand our clinical, research and development activities.

S-8

If our competitors develop and market products that are more effective than ours, or obtain marketing approval before we do, our commercial opportunity will be reduced or eliminated.

The biotechnology and pharmaceutical industries are intensely competitive and subject to rapid and significant technological change. Some of the drugs that we are attempting to develop, for example TLK199, will have to compete with existing therapies. In addition, a number of companies are pursuing the development of pharmaceuticals that target the same diseases and conditions that we are targeting. We face competition from pharmaceutical and biotechnology companies in the United States and abroad. Our competitors may develop new screening technologies and may utilize discovery techniques or partner with collaborators in order to develop products more rapidly or successfully than we, or our collaborators, are able to do. Many of our competitors, particularly large pharmaceutical companies, have substantially greater financial, technical and human resources than we do. In addition, academic institutions, government agencies and other public and private organizations conducting research may seek patent protection with respect to potentially competing products or technologies and may establish exclusive collaborative or licensing relationships with our competitors.

Our competitors may succeed in developing technologies and drugs that are more effective or less costly than any which are being developed by us or which would render our technology and potential drugs obsolete and noncompetitive. In addition, our competitors may succeed in obtaining FDA or other regulatory approvals for product candidates more rapidly than we, or our collaborators. We cannot assure you that drugs resulting from our research and development efforts, or from our joint efforts with our existing or future collaborative partners, will be able to compete successfully with our competitors' existing products or products under development or that they will obtain regulatory approval in the United States or elsewhere.

If we do not obtain regulatory approval to market products in the United States and foreign countries, we or our collaborators will not be permitted to commercialize our product candidates.

Even if we are able to achieve success in our preclinical testing, we, or our collaborators, must provide the FDA and foreign regulatory authorities with clinical data that demonstrate the safety and efficacy of our products in humans before they can be approved for commercial sale. Failure to obtain regulatory approval will prevent commercialization of our products.

The pharmaceutical industry is subject to stringent regulation by a wide range of authorities. We cannot predict whether regulatory clearance will be obtained for any product that we are developing or hope to develop. A pharmaceutical product cannot be marketed in the United States until it has completed rigorous preclinical testing and clinical trials and an extensive regulatory clearance process implemented by the FDA. Satisfaction of regulatory requirements typically takes many years, is dependent upon the type, complexity and novelty of the product and requires the expenditure of substantial resources. Of particular significance are the requirements covering research and development, testing, manufacturing, quality control, labeling and promotion of drugs for human use.

Before commencing clinical trials in humans, we, or our collaborators, must submit and receive approval from the FDA of an IND application. We must comply with FDA "Good Laboratory Practices" regulations in our preclinical studies. Clinical trials are subject to oversight by institutional review boards and the FDA and:

•

must be conducted in conformance with the FDA's IND regulations;

•

must meet requirements for informed consent;

•

must meet requirements for Good Clinical Practices;

S-9

•

may require large numbers of participants; and

•

may be suspended by us, our collaborators or the FDA at any time if it is believed that the subjects participating in these trials are being exposed to unacceptable health risks or if the FDA finds deficiencies in the IND application or the conduct of these trials.

Before receiving FDA clearance to market a product, we or our collaborators must demonstrate that the product is safe and effective in the patient population that will be treated. Negative or inconclusive results or adverse medical events during a clinical trial could cause a clinical trial to be repeated, a program to be terminated and could delay approval. We typically rely on third party clinical investigators to conduct our clinical trials and other third party organizations to perform data collection and analysis and, as a result, we may face additional delaying factors outside our control. In addition, delays or rejections may be encountered based upon additional government regulation from future legislation or administrative action or changes in FDA policy or interpretation during the period of product development, clinical trials and FDA regulatory review. Failure to comply with applicable FDA or other applicable regulatory requirements may result in criminal prosecution, civil penalties, recall or seizure of products, total or partial suspension of production or injunction, as well as other regulatory action. We have limited experience in conducting and managing the clinical trials necessary to obtain regulatory approval.

If regulatory clearance of a product is granted, this clearance will be limited to those disease states and conditions for which the product is demonstrated through clinical trials to be safe and efficacious. We cannot ensure that any compound developed by us, alone or with others, will prove to be safe and efficacious in clinical trials and will meet all of the applicable regulatory requirements needed to receive marketing clearance.

Outside the United States, the ability to market a product is contingent upon receiving a marketing authorization from the appropriate regulatory authorities. This foreign regulatory approval process typically includes all of the risks associated with FDA clearance described above and may include additional risks.

As our product programs advance, we will need to hire additional scientific and management personnel. Our research and development efforts will be seriously jeopardized if we are unable to attract and retain key personnel.

Our success depends on the continued contributions of our principal management and scientific personnel and on our ability to develop and maintain important relationships with leading academic institutions, scientists and companies in the face of intense competition for such personnel. As we progress to advanced clinical trials, including phase 2 and phase 3, we will also need to expand our clinical development personnel. In addition, our research programs depend on our ability to attract and retain highly skilled chemists and other scientists. We do not have employment contracts with our key employees. If we lose the services of Dr. Michael Wick or any of our other key personnel, our research and development efforts could be seriously and adversely affected. There is currently a shortage of skilled executives and employees with technical expertise in the biotechnology industry, and this shortage is likely to continue. As a result, competition among numerous companies, academic and other research institutions for skilled personnel and experienced scientists is intense and turnover rates are high. In recent years, the cost of living in the San Francisco Bay Area has increased significantly, which we expect will adversely affect our ability to compete for qualified personnel and will increase costs. Because of this competitive environment, we may encounter increasing difficulty in attracting qualified personnel as our operations expand and the demand for these professionals increases, and this difficulty could significantly impede the achievement of our research and development objectives.

S-10

If physicians and patients do not accept our products, our ability to generate product revenue in the future will be adversely affected.

Our product candidates may not gain market acceptance among physicians, patients and the medical community. We believe that market acceptance will depend on our ability to provide acceptable evidence of safety, efficacy, convenience and ease of administration and cost effectiveness. In addition, we believe market acceptance will depend on the effectiveness of our marketing strategy and the pricing of our products. Physicians may elect not to recommend our products even if we meet the above criteria. If any of our product candidates fails to achieve market acceptance, we may not be able to successfully market and sell the product, which would limit our ability to generate revenue and adversely affect our operations.

If we or our licensees cannot obtain and defend our respective intellectual property rights, or if our products or technologies are found to infringe patents of third parties, we could become involved in lengthy and costly legal proceedings that could adversely affect our business.

Our success will depend in a large part on our own and our licensees' ability to obtain and defend patents for each party's respective technologies and the compounds and other products, if any, resulting from the application of these technologies. The patent positions of pharmaceutical and biotechnology companies can be highly uncertain and involve complex legal and factual questions. As a result, the degree of future protection for our proprietary rights is uncertain and we cannot assure you that:

•

we were the first to make the inventions covered by each of our pending patent applications;

•

we were the first to file patent applications for these inventions;

•

others will not independently develop similar or alternative technologies or duplicate any of our technologies;

•

any of our pending patent applications will result in issued patents;

•

any patents issued to us or our collaborators will provide a basis for commercially viable products, will provide us with any competitive advantages or will not be challenged by third parties;

•

any of our issued patents will be valid or enforceable; or

•

we will develop additional proprietary technologies that are patentable.

Accordingly, we cannot predict the breadth of claims allowed in our or other companies' patents.

Our success will also depend, in part, on our ability to operate without infringing the intellectual property rights of others. We cannot assure you that our activities will not infringe patents owned by others. If our products or technologies are found to infringe patents issued to third parties, the manufacture, use and sale of our products could be enjoined, and we could be required to pay substantial damages. In addition, we may be required to obtain licenses to patents or other proprietary rights of third parties. No assurance can be given that any licenses required under any such patents or proprietary rights would be made available on terms acceptable to us, if at all. Failure to obtain such licenses could negatively affect our business.

Others may have filed and in the future may file patent applications covering small molecules or therapeutic products that are similar to ours. We cannot assure you that any patent application filed by someone else will not have priority over patent applications filed by us. Any legal action against us or our collaborators claiming damages and seeking to enjoin commercial activities relating to the affected products and processes could, in addition to subjecting us to potential liability for damages,

S-11

require us or our collaborators to obtain a license to continue to manufacture or market the affected products and processes. We cannot predict whether we, or our collaborators, would prevail in any of these actions or that any license required under any of these patents would be made available on commercially acceptable terms, if at all. We believe that there may be significant litigation in the industry regarding patent and other intellectual property rights. If we become involved in litigation, it could consume a substantial portion of our managerial and financial resources and we may not be successful in any such litigation.

In addition, we could incur substantial costs and use of our key employees' time and efforts in litigation if we are required to defend against patent suits brought by third parties or if we initiate these suits, and we cannot predict whether we would be able to prevail in any such suit.

Futhermore, some of our patents and intellectual property rights are owned jointly by us and our collaborators. We cannot assure you that these joint owners will not use these patents and other intellectual property in ways that may negatively affect our business. We will not be able to prevent such use.

We also rely on trade secrets to protect technology, including our TRAP technology, where we believe patent protection is not appropriate or obtainable. However, trade secrets are difficult to protect. While we require employees, academic collaborators and consultants to enter into confidentiality agreements, we may not be able to adequately protect our trade secrets or other proprietary information in the event of any unauthorized use or disclosure or the lawful development by others of such information. If the identity of specific proteins or other elements of our technology become known, our competitive advantage in drug discovery could be reduced.

We will be dependent upon collaborative arrangements to complete the development and commercialization of some of our product candidates. These collaborative arrangements may place the development of our product candidates outside of our control, may require us to relinquish important rights or may otherwise not be on terms favorable to us.

We expect to enter into collaborative arrangements with third parties for clinical trials, development, manufacturing, regulatory approvals or commercialization of some of our products, particularly outside North America, or in disease areas requiring larger and longer clinical trials, such as diabetes. Dependence on collaborative arrangements will subject us to a number of risks. We may not be able to control the amount and timing of resources our collaborative partners may devote to the product candidates. Our collaborative partners may experience financial difficulties. Should a collaborative partner fail to develop or commercialize a compound or product to which it has rights from us, we may not receive any future milestone payments and will not receive any royalties for this compound or product. Business combinations or significant changes in a collaborative partner's business strategy may also adversely affect a partner's willingness or ability to complete its obligations under the arrangement. If we fail to enter into additional collaborative agreements on favorable terms, our business, financial condition and results of operations could be materially adversely affected.

Under our existing collaboration agreements, we are entitled to payments upon future product sales or the achievement of milestones. For example, under our collaboration agreement(s) with Sanwa, we may be entitled to payments of up to $10.0 million. However, there can be no assurance that any product will be successful under these collaborations or that we will receive any of these payments.

Some of our collaborations are for early-stage programs and allow partners significant discretion in electing whether to pursue any of the planned activities. We do not anticipate significant revenues to result from these relationships until the collaborator has advanced products into clinical trials, which will not occur for several years, if at all. Such arrangements are subject to numerous risks, including

S-12

the right of the collaboration partner to control the timing of the research and development efforts, and discretion to advance lead candidates to clinical trials and commercialization of the product. In addition, a collaborative partner could independently move forward with a competing lead candidate developed either independently or in collaboration with others, including our competitors.

If we are unable to contract with third parties to manufacture our products in sufficient quantities and at an acceptable cost, we may be unable to meet demand for our products and lose potential revenue.

We do not currently operate manufacturing facilities for clinical or commercial production of our products under development. We expect to continue to rely on third parties for the manufacture of our product. We currently lack the resources or capability to manufacture any of our products on a clinical or commercial scale. As a result, we will be dependent on corporate partners, licensees or other third parties for the manufacturing of clinical and commercial scale quantities of our products. Our products may be in competition with other products for access to these facilities. For this and other reasons, our collaborators or third parties may not be able to manufacture these products in a cost effective or timely manner. If not performed in a timely manner, the clinical trial development of our product candidates or their submission for regulatory approval could be delayed, and our ability to deliver products on a timely basis could be impaired or precluded. We are currently dependent upon two sources of supply for clinical quantities of TLK286 and a sole source of supply for clinical quantities of TLK199. If our suppliers fail to perform, our clinical trials or commercialization of TLK286 and TLK199 would be delayed. We may not be able to enter into any necessary third-party manufacturing arrangements on acceptable terms, if at all. Our current dependence upon others for the manufacture of our products may adversely affect our future profit margins and our ability to commercialize products on a timely and competitive basis.

If we are unable to create sales, marketing and distribution capabilities or enter into agreements with third parties to perform these functions, we will not be able to commercialize products.

We currently have no sales, marketing or distribution capabilities. In order to commercialize any products, we must internally develop sales, marketing and distribution capabilities, or establish collaborations or other arrangements with third parties to perform these services. We intend to market some products directly in North America and rely on relationships with one or more pharmaceutical companies with established distribution systems and direct sales forces to market other products and address other markets. We may not be able to establish in-house sales and distribution capabilities or relationships with third parties. To the extent that we enter into co-promotion or other licensing arrangements, our product revenues are likely to be lower than if we directly marketed and sold our products, and any revenues we receive will depend upon the efforts of third parties, whose efforts may not be successful.

If product liability lawsuits are successfully brought against us, we may incur substantial liabilities and may be required to limit commercialization of our products.

The testing and marketing of medical products entail an inherent risk of product liability. If we cannot successfully defend ourselves against product liability claims, we may incur substantial liabilities or be required to limit commercialization of our products. If we are unable to obtain sufficient product liability insurance at an acceptable cost, potential product liability claims could prevent or inhibit the commercialization of pharmaceutical products we develop, alone or with corporate collaborators.

S-13

If we use biological and hazardous materials in a manner that causes injury, we may be liable for damages.

Our research and development activities involve the controlled use of potentially harmful biological materials, hazardous materials, chemicals and various radioactive compounds, and are subject to federal, state and local laws and regulations governing the use, storage, handling and disposal of these materials and specified waste products. We cannot completely eliminate the risk of accidental contamination or injury from the use, storage, handling or disposal of these materials. In the event of contamination or injury, we could be held liable for damages that result, and any liability could exceed our resources.

We have implemented anti-takeover provisions which could discourage or prevent a takeover, even if an acquisition would be beneficial to our stockholders.

Provisions of our amended and restated certificate of incorporation and bylaws, as well as provisions of Delaware law, could make it more difficult for a third party to acquire us, even if doing so would be beneficial to our stockholders. These provisions include:

•

establishing a classified Board of Directors requiring that members of the Board be elected in different years lengthening the time needed to elect a new majority of the Board;

•

authorizing the issuance of "blank check" preferred stock that could be issued by our Board of Directors to increase the number of outstanding shares or change the balance of voting control and thwart a takeover attempt;

•

prohibiting cumulative voting in the election of directors, which would otherwise allow for less than a majority of stockholders to elect director candidates;

•

limiting the ability of stockholders to call special meetings of the stockholders;

•

prohibiting stockholder action by written consent and requiring all stockholder actions to be taken at a meeting of our stockholders; and

•

establishing advance notice requirements for nominations for election to the Board of Directors and for proposing matters that can be acted upon by stockholders at stockholder meetings.

In addition, in November 2001, we adopted a stockholder rights plan that may discourage, delay or prevent a merger that a stockholder may consider favorable.

Substantial future sales of our common stock by us or by our existing stockholders could cause our stock price to fall.

Additional equity financings or other share issuances by us, including shares issued in connection with strategic alliances, could adversely affect the market price of our common stock. Sales by existing stockholders of a large number of shares of our common stock in the public market or the perception that additional sales could occur could cause the market price of our common stock to drop.

If we do not progress in our programs as anticipated, our stock price could decrease.

For planning purposes, we estimate the timing of a variety of clinical, regulatory and other milestones, such as when a certain product candidate will enter clinical development, when a clinical trial will be completed or when an application for regulatory approval will be filed. Some of our estimates are included in this prospectus supplement. Our estimates are based on present facts and a variety of assumptions. Many of the underlying assumptions are outside of our control. If milestones are not

S-14

achieved when we expect them to be, investors could be disappointed, and our stock price may decrease.

Our stock price may be volatile, and you may not be able to resell your shares at or above your purchase price.

Our stock prices and the market prices for securities of biotechnology companies in general have been highly volatile, with recent significant price and volume fluctuations, and may continue to be highly volatile in the future. You may not be able to sell your shares quickly or at the market price if trading in our stock is not active or the volume is low. The following factors, in addition to other risk factors described in this section, may have a significant impact on the market price of our common stock:

•

developments regarding, or the results of, our clinical trials, including TLK286 clinical trials;

•

announcements of technological innovations or new commercial products by our competitors or us;

•

developments concerning proprietary rights, including patents;

•

developments concerning our collaborations;

•

publicity regarding actual or potential medical results relating to products under development by our competitors or us;

•

regulatory developments in the United States and foreign countries;

•

litigation;

•

economic and other external factors or other disaster or crisis; or

•

period-to-period fluctuations in our financial results.

If materials distributed at an investor conference were determined by a court to have been distributed in connection with this offering and in violation of securities laws, purchasers in this offering would have the right to seek refunds or damages.

Certain materials about us were distributed in connection with an investor conference sponsored by a broker dealer. This broker dealer regularly publishes reports, opinions and recommendations regarding our common stock and was proposed to be an underwriter in this offering. The materials distributed included a one-page fact sheet containing publicly available information about us and a compilation of interviews relating to conference participants, including an interview of a financial analyst employed by the broker dealer. In this interview, the analyst focused on three companies, including us, summarized TLK286 and made some forward-looking statements about us. An abbreviated version of this interview was issued as a press release. We have been advised that the materials were prepared in connection with the conference and not in anticipation of or in connection with this offering. This broker dealer is not participating in this offering as an underwriter or selling group member.

We urge all prospective investors to read, and base their investment decision only on, the information contained in this prospectus. If one or more of these materials were deemed attributable to us or to an underwriter participating in the offering, and deemed to constitute a prospectus that does not meet the requirements of the Securities Act of 1933, persons who purchased our common stock in this offering may have the right, for a period of one year from the date of the violation, to obtain recovery of the consideration paid in connection with their purchase of our common stock or, if they had already sold the stock, to recover any losses resulting from their purchase of common stock.

S-15

Use of proceeds

The net proceeds to us from the sale of the 5,000,000 shares of common stock in the offering are estimated to be $66.0 million ($75.9 million if the underwriters' over-allotment option is exercised in full), based on an assumed public offering price of $14.12 per share and after deducting the underwriting discounts and commissions and estimated offering expenses payable by us.

We anticipate using the net proceeds from the sale of the common stock offered by this prospectus supplement to fund the clinical development of TLK286 and TLK199, the advancement of TLK19781 into clinical development, research and development, and for working capital and general corporate purposes. The amounts and timing of the expenditures will depend on numerous factors, such as the timing and progress of our clinical trials and research and development efforts, technological advances and the competitive environment for our products candidates. As of the date of this prospectus supplement, we cannot specify with certainty all of the particular uses for the net proceeds we will have upon completion of the offering, accordingly, we will retain broad discretion over the use of these proceeds.

Pending the use of the net proceeds, we intend to invest the net proceeds in short-term, interest-bearing, investment-grade securities.

S-16

Price range of common stock

Our common stock commenced trading publicly on the Nasdaq National Market on August 11, 2000 and is traded under the symbol "TELK." The following table sets forth, for the periods indicated, the high and low bid prices of our common stock as reported on the Nasdaq National Market:

Year ended December 31, 2000	High	Low
Third quarter (from August 11)	$14.50	$6.00
Fourth quarter	$10.56	$5.63

Year ended December 31, 2001	High	Low
First quarter	$8.59	$3.63
Second quarter	$9.84	$4.94
Third quarter	$11.12	$6.31
Fourth quarter	$14.49	$6.02

Year ended December 31, 2002	High	Low
First quarter	$14.46	$9.00
Second quarter	$13.30	$8.00
Third quarter (through September 10)	$15.32	$10.25

As of September 10, 2002, there were 138 holders of record of our common stock. On September 10, 2002, the last sale price reported on the Nasdaq National Market for our common stock was $14.12 per share.

Dividend policy

We have never paid our stockholders dividends, and we do not anticipate paying any cash dividends in the foreseeable future as we intend to retain any earnings for use in our business.

S-17

Capitalization

The following table shows our unaudited capitalization as of June 30, 2002:

•

on an actual basis; and

•

as adjusted to give effect to the sale of 5,000,000 shares of our common stock in this offering at an assumed public offering price of $14.12 per share, after deducting the underwriting discounts and commissions and estimated offering expenses payable by us.

This table should be read with "Management's discussion and analysis of financial condition and results of operations" and our financial statements and notes thereto incorporated by reference in this prospectus supplement and the accompanying prospectus.

			As of June 30, 2002
			Actual		As adjusted
			(In thousands, except share data)
Cash, cash equivalents and investments			$42,175		$108,139
Long-term liabilities			$29		$29
Stockholders' equity:
	Preferred stock, $0.01 par value; 5,000,000 shares authorized; no shares issued and outstanding, actual and as adjusted		—		—
	Common stock, $0.01 par value; 100,000,000 shares authorized; 27,859,799 shares issued and outstanding, actual; 32,859,799 shares issued and outstanding, as adjusted		279		329
	Additional paid-in capital		135,268		201,182
	Deferred stock compensation		(890	)	(890	)
	Note receivable from employee		(48	)	(48	)
	Accumulated other comprehensive income		4		4
	Accumulated deficit		(96,831	)	(96,831	)
		Total stockholders' equity	37,782		103,746
		Total capitalization	$37,811		$103,775

The number of shares of common stock outstanding is based on the number of shares outstanding as of June 30, 2002 and excludes:

•

4,680,830 shares of common stock underlying options outstanding as of June 30, 2002 at a weighted average exercise price of $6.57 per share; and

•

1,429,778 shares available for issuance or future grant under our 2000 Equity Incentive Plan, 460,883 shares available for issuance under our 2000 Employee Stock Purchase Plan and 162,500 shares available for issuance or future grant under our 2000 Non-Employee Directors' Stock Option Plan, as of June 30, 2002.

S-18

Dilution

The net tangible book value of our common stock on June 30, 2002 was approximately $37.8 million, or $1.36 per share. Net tangible book value per share is equal to the amount of our total tangible assets, less total liabilities, divided by the number of shares of common stock outstanding. Dilution in net tangible book value per share represents the difference between the amount per share paid by purchasers of shares of common stock in this offering and the net tangible book value per share of our common stock immediately afterwards. After giving effect to the sale of 5,000,000 shares of common stock offered by this prospectus supplement at an assumed public offering price of $14.12 per share, and after deducting the underwriting discounts and commissions and estimated offering expenses, our net tangible book value at June 30, 2002 would have been approximately $103.7 million, or $3.16 per share. This represents an immediate increase in net tangible book value of $1.80 per share to existing stockholders and an immediate dilution of $10.96 per share to new investors purchasing shares of common stock in this offering. The following table illustrates this dilution:

Assumed public offering price per share			$14.12
	Net tangible book value per share as of June 30, 2002	$1.36
	Increase per share attributable to new investors	1.80
Net tangible book value per share after this offering			3.16
Dilution per share to new investors			$10.96

The foregoing table does not take into effect further dilution to new investors that could occur upon the exercise of outstanding options having a per share exercise price less than the offering price per share in this offering. As of June 30, 2002, there were:

•

4,680,830 shares of common stock underlying options outstanding at a weighted average exercise price of $6.57 per share; and

•

1,429,778 shares available for issuance or future grant under our 2000 Equity Incentive Plan, 460,883 shares available for issuance under our 2000 Employee Stock Purchase Plan and 162,500 shares available for issuance or future grant under our 2000 Non-Employee Directors' Stock Option Plan.

S-19

Underwriting

We and the underwriters for this offering named below have entered into an underwriting agreement concerning the shares being offered. Subject to conditions, each underwriter has severally agreed to purchase the number of shares indicated in the following table. UBS Warburg LLC, Wachovia Securities, Inc., Legg Mason Wood Walker, Inc. and Needham & Company, Inc. are the representatives of the underwriters. UBS Warburg LLC is the sole book-running manager of this offering.

		Number of shares
Underwriters
UBS Warburg LLC
Wachovia Securities, Inc.
Legg Mason Wood Walker, Inc.
Needham & Company, Inc.
	Total	5,000,000

If the underwriters sell more shares than the total number set forth in the table above, the underwriters have a 30-day option to buy up to an additional 750,000 shares from us at the public offering price less the underwriting discounts and commissions to cover these sales. If any shares are purchased under this option, the underwriters will severally purchase shares in approximately the same proportion as set forth in the table above.

The following table shows the per share and total underwriting discounts and commissions we will pay to the underwriters. These amounts are shown assuming both no exercise and full exercise of the underwriters' option to purchase up to an additional 750,000 shares.

	No exercise	Full exercise
Per share	$	$
Total	$	$

We estimate that the total expenses of the offering payable by us, excluding underwriting discounts and commissions, will be approximately $400,000.

Shares sold by the underwriters to the public will initially be offered at the public offering price set forth on the cover of this prospectus supplement. Any shares sold by the underwriters to securities dealers may be sold at a discount of up to $            per share from the public offering price. Any of these securities dealers may resell any shares purchased from the underwriters to other brokers or dealers at a discount of up to $    per share from the public offering price. If all the shares are not sold at the public offering price, the representatives may change the offering price and the other selling terms.

We and each of our directors and executive officers have agreed with the underwriters not to offer, sell, contract to sell, hedge or otherwise dispose of, directly or indirectly, any of our common stock or securities convertible into or exchangeable for shares of common stock during the period from the date of this prospectus supplement continuing through the date 90 days after the date of this prospectus supplement, subject to certain permitted exceptions, without the prior written consent of UBS Warburg LLC.

In connection with this offering, the underwriters may purchase and sell shares of our common stock in the open market. These transactions may include stabilizing transactions, short sales and purchases to cover positions created by short sales. Stabilizing transactions consist of bids or purchases made for the purpose of preventing or retarding a decline in the market price of our common stock while this

S-20

offering is in progress. Short sales involve the sale by the underwriters of a greater number of shares than they are required to purchase in this offering. Short sales may be either "covered short sales" or "naked short sales." Covered short sales are sales made in an amount not greater than the underwriters' over-allotment option to purchase additional shares in this offering. The underwriters may close out any covered short position by either exercising their over-allotment option or purchasing shares in the open market. In determining the source of shares to close out the covered short position, the underwriters will consider, among other things, the price of shares available for purchase in the open market as compared to the price at which they may purchase shares through the over-allotment option. Naked short sales are sales in excess of the over-allotment option. The underwriters must close out any naked short position by purchasing shares in the open market. A naked short position is more likely to be created if the underwriters are concerned there may be downward pressure on the price of shares in the open market after pricing that could adversely affect investors who purchase in this offering.

The underwriters also may impose a penalty bid. This occurs when a particular underwriter repays to the underwriters a portion of the underwriting discount received by it because the representatives have repurchased shares sold by or for the account of that underwriter in stabilizing or short covering transactions.

These activities by the underwriters may stabilize, maintain or otherwise affect the market price of our common stock. As a result, the price of our common stock may be higher than the price that otherwise might exist in the open market. If these activities are commenced, they may be discontinued by the underwriters at any time. These transactions may be effected on the Nasdaq National Market or otherwise.

In addition, in connection with this offering, certain of the underwriters (and selling group members) may engage in passive market making transactions in the common stock on the Nasdaq National Market prior to the pricing and completion of the offering. Passive market making consists of displaying bids on the Nasdaq National Market no higher than the bid prices of independent market makers and making purchases at prices no higher than these independent bids and effected in response to order flow. Net purchases by a passive market maker on each day are limited to a specified percentage of the passive market maker's average daily trading volume in the common stock during a specified period and must be discontinued when such limit is reached. Passive market making may cause the price of the common stock to be higher than the price that otherwise would exist in the open market in the absence of such transactions. If passive market making is commenced, it may be discontinued at any time.

We have agreed to indemnify the several underwriters against some liabilities, including liabilities under the Securities Act of 1933, as amended, and to contribute to payments that the underwriters may be required to make in respect thereof.

Legg Mason Wood Walker, Inc. has in the past provided and may in the future provide financial advisory services to us. For these services, we have paid them, or will pay them, customary compensation.

S-21

Legal matters

Cooley Godward LLP, San Francisco, California will pass upon the validity of the issuance of the common stock offered by this prospectus supplement. As of the date of this prospectus supplement, certain partners and associates of Cooley Godward LLP own an aggregate of 28,276 shares of our common stock through investment partnerships. Deborah A. Marshall, a partner at Cooley Godward LLP, is our Secretary. Dewey Ballantine LLP, New York, New York, is counsel for the underwriters in connection with this offering.

S-22

PROSPECTUS

$100,000,000

Common Stock
Preferred Stock
Debt Securities
Warrants

From time to time, we may sell common stock, preferred stock, debt securities and/or warrants.

We will provide the specific terms of these securities in one or more supplements to this prospectus. You should read this prospectus and any prospectus supplement carefully before you invest.

Our common stock is traded on The Nasdaq National Market under the trading symbol "TELK." The applicable prospectus supplement will contain information, where applicable, as to any other listing (if any) on The Nasdaq Stock Market's National Market or any securities exchange of the securities covered by the prospectus supplement.

THIS PROSPECTUS MAY NOT BE USED TO OFFER OR SELL ANY SECURITIES UNLESS ACCOMPANIED BY A PROSPECTUS SUPPLEMENT.

The securities may be sold directly by us to investors, through agents designated from time to time or to or through underwriters or dealers. For additional information on the methods of sale, you should refer to the section entitled "Plan of Distribution." If any underwriters are involved in the sale of any securities with respect to which this prospectus is being delivered, the names of such underwriters and any applicable commissions or discounts will be set forth in a prospectus supplement. The net proceeds we expect to receive from such sale will also be set forth in a prospectus supplement.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED THESE SECURITIES OR DETERMINED IF THIS PROSPECTUS IS TRUTHFUL OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

July 12, 2002

TABLE OF CONTENTS

	Page
About this prospectus	1
Telik	2
The securities we may offer	2
Forward-looking information	4
Ratio of earnings to fixed charges	4
Use of proceeds	5
Description of capital stock	5
Description of debt securities	9
Description of warrants	15
Legal ownership of securities	17
Plan of distribution	21
Legal matters	23
Experts	23
Where you can find more information	23

This prospectus is part of a registration statement we filed with the Securities and Exchange Commission. You should rely only on the information we have provided or incorporated by reference in this prospectus or any prospectus supplement. We have not authorized anyone to provide you with information different from that contained in this prospectus. No dealer, salesperson or other person is authorized to give any information or to represent anything not contained in this prospectus. You must not rely on any unauthorized information or representation. This prospectus is an offer to sell only the securities offered hereby, but only under circumstances and in jurisdictions where it is lawful to do so. You should assume that the information in this prospectus or any prospectus supplement is accurate only as of the date on the front of the document and that any information we have incorporated by reference is accurate only as of the date of the document incorporated by reference, regardless of the time of delivery of this prospectus or any sale of a security.

About this prospectus

This prospectus is part of a registration statement that we filed with the SEC using a "shelf" registration process. Under this shelf registration process, we may sell common stock, preferred stock, debt securities and/or warrants in one or more offerings up to a total dollar amount of $100,000,000. This prospectus provides you with a general description of the securities we may offer. Each time we sell common stock, preferred stock, debt securities and/or warrants, we will provide a prospectus supplement that will contain more specific information, as set forth below under "The Securities We May Offer." We may also add, update or change in the prospectus supplement any of the information contained in this prospectus. This prospectus, together with applicable prospectus supplements, includes all material information relating to this offering. Please carefully read both this prospectus and any prospectus supplement together with the additional information described below under "Where You Can Find More Information."

Telik

Telik, Inc. is a biopharmaceutical company working to discover, develop and commercialize small molecule drugs to treat serious diseases for which there is significant demand for new therapies. Our most advanced drug development programs include: TLK286, a tumor activated drug candidate for the treatment of major cancers, which is currently in phase 2 clinical trials in colorectal, ovarian, non-small cell lung and breast cancer; TLK199, a candidate for the treatment of myelodysplastic syndrome, or MDS, a form of pre-leukemia, and for increasing white blood cell levels depleted by chemotherapy, which is currently in phase 1-2a clinical trial for MDS; and a family of orally active insulin receptor activators for Type 2 diabetes. Our product candidates were discovered using our proprietary technology, TRAP, which enables the rapid and efficient discovery of small molecule drug candidates.

We were incorporated in Delaware in September 1988. Our executive offices are currently located at 750 Gateway Boulevard, South San Francisco, California 94080. Our telephone number is (650) 244-9303. Our website is http://www.telik.com. We have not incorporated by reference into this prospectus the information on our website, and you should not consider it to be a part of this document. Our web site address is included in this document as an inactive textual reference only.

"Telik" and the Telik logo are trademarks of Telik, Inc. All other brand names or trademarks appearing in this prospectus are the property of their respective holders.

The securities we may offer

We may offer shares of our common stock and preferred stock, various series of debt securities and/or warrants to purchase any of such securities with a total value of up to $100 million from time to time under this prospectus at prices and on terms to be determined by market conditions at the time of offering. This prospectus provides you with a general description of the securities we may offer. Each time we offer a type or series of securities, we will provide a prospectus supplement that will describe the specific amounts, prices and other important terms of the securities, including, to the extent applicable:

•

designation or classification;

•

aggregate principal amount or aggregate offering price;

•

maturity, if applicable;

•

rates and times of payment of interest or dividends, if any;

•

redemption, conversion or sinking fund terms, if any;

•

voting or other rights, if any;

•

conversion prices, if any; and

•

important federal income tax considerations.

The prospectus supplement also may add, update or change information contained in this prospectus or in documents we have incorporated by reference.

THIS PROSPECTUS MAY NOT BE USED TO CONSUMMATE A SALE OF SECURITIES UNLESS IT IS ACCOMPANIED BY A PROSPECTUS SUPPLEMENT.

We may sell the securities directly to or through agents, underwriters or dealers. We, and our agents or underwriters, reserve the right to accept or reject all or part of any proposed purchase of securities. If

2

we do offer securities through agents or underwriters, we will include in the applicable prospectus supplement:

•

the names of those agents or underwriters;

•

applicable fees, discounts and commissions to be paid to them; and

•

the net proceeds to us.

Common Stock.    We may issue shares of our common stock from time to time. Holders of common stock are entitled to one vote per share on all matters submitted to a vote of stockholders. Subject to any preferences of outstanding shares of preferred stock, holders of common stock are entitled to dividends when and if declared by the board of directors.

Preferred Stock.    We may issue shares of our preferred stock from time to time, in one or more series. Our board of directors shall determine the rights, preferences, privileges and restrictions of the preferred stock, including dividend rights, conversion rights, voting rights, terms of redemption, liquidation preferences, sinking fund terms and the number of shares constituting any series or the designation of any series. Convertible preferred stock will be convertible into our common stock. Conversion may be mandatory or at your option and would be at prescribed conversion rates.

Debt Securities.    We may offer debt securities from time to time, in one or more series, as either senior or subordinated debt or as senior or subordinated convertible debt. The senior debt securities will rank equally with any other unsecured and unsubordinated debt. The subordinated debt securities will be subordinate and junior in right of payment, to the extent and in the manner described in the instrument governing the debt, to all of our senior indebtedness. Convertible debt securities will be convertible into or exchangeable for our common stock or other securities of ours. Conversion may be mandatory or at your option and would be at prescribed conversion rates.

The debt securities will be issued under one or more documents called indentures, which are contracts between us and a national banking association, as trustee. In this prospectus, we have summarized certain general features of the debt securities. We urge you, however, to read the prospectus supplements related to the series of debt securities being offered, as well as the complete indentures that contain the terms of the debt securities. Indentures have been filed as exhibits to the registration statement of which this prospectus is a part, and supplemental indentures and forms of debt securities containing the terms of debt securities being offered will be filed as exhibits to the registration statement of which this prospectus is a part or will be incorporated by reference from reports we file with the SEC.

Warrants.    We may issue warrants for the purchase of common stock, preferred stock and/or debt securities in one or more series. We may issue warrants independently or together with common stock, preferred stock and/or debt securities, and the warrants may be attached to or separate from these securities. In this prospectus, we have summarized certain general features of the warrants. We urge you, however, to read the prospectus supplements related to the series of warrants being offered, as well as the warrant agreement that contains the terms of the warrants. The warrant agreement and form of warrant containing the terms of the warrants being offered will be filed as exhibits to the registration statement of which this prospectus is a part or will be incorporated by reference from reports we file with the SEC.

We will evidence each series of warrants by warrant certificates that we will issue under a separate agreement. We will enter into the warrant agreement with a warrant agent. Each warrant agent will be a bank that we select which has its principal office in the United States and a combined capital and surplus of at least $50,000,000. We will indicate the name and address of the warrant agent in the applicable prospectus supplement relating to a particular series of warrants.

3

Forward-looking information

This prospectus, including the documents that we incorporate by reference, contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and within the meaning of Section 21E of the Securities Exchange Act of 1934, as amended, that are subject to the "safe harbor" created by those sections. Any statements about our expectations, beliefs, plans, objectives, assumptions or future events or performance are not historical facts and may be forward-looking. These statements are often, but not always, made through the use of words or phrases such as "anticipate," "estimate," "plan," "project," "continuing," "ongoing," "expect," "believe," "intend," "predict," "potential" and similar words or phrases or the negatives of these words or phrases. Accordingly, these statements involve estimates, assumptions and uncertainties which could cause actual results to differ materially from those expressed in these statements. Any forward-looking statements are qualified in their entirety by reference to the factors discussed throughout this prospectus. Examples of these statements include, but are not limited to, statements regarding the following: the extent to which our issued and pending patents may protect our products and technology, our ability to identify new product candidates using our proprietary TRAP technology, the potential of such product candidates to lead to the development of safer or more-effective therapies, our ability to develop the technology derived from our collaborations, our anticipated timing for filing an Investigational New Drug with the FDA or for the initiation or completion of phase 1, phase 2 or phase 3 clinical trials for any of our product candidates, our future operating expenses, our future losses, and our future expenditures for research and development.

Because the risk factors referred to above, as well as the risk factors incorporated by reference, could cause actual results or outcomes to differ materially from those expressed in any forward-looking statements made by us or on our behalf, you should not place undue reliance on any forward-looking statements. Further, any forward-looking statement speaks only as of the date on which it is made, and we undertake no obligation to update any forward-looking statement to reflect events or circumstances after the date on which the statement is made or to reflect the occurrence of unanticipated events. New factors emerge from time to time, and it is not possible for us to predict which factors will arise. In addition, we cannot assess the impact of each factor on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements.

Ratio of earnings to fixed charges

Our earnings were insufficient to cover fixed charges in each of the years in the five-year period ended December 31, 2001 and in the three-month period ended March 31, 2002. "Earnings" consist of income (loss) from continuing operations before income taxes, extraordinary items, cumulative effect of accounting changes, equity in net losses of affiliates and fixed charges. "Fixed charges" consist of interest expense and the portion of operating lease expense that represents interest. The extent to which earnings were insufficient to cover fixed charges is as follows:

	Year Ended December 31,
											Three Months Ended March 31, 2002
	1997		1998		1999		2000		2001
	(in thousands)
Deficiency of earnings available to cover fixed charges	$(8,618	)	$(6,579	)	$(7,064	)	$(17,224	)	$(18,566	)	$(5,245	)

4

Use of proceeds

Except as described in any prospectus supplement, we currently intend to use the net proceeds from the sale of our securities for research and development and general corporate purposes. We may also use a portion of the net proceeds to acquire or invest in businesses, products and technologies that are complementary to our own, although we currently are not planning or negotiating any such transactions. Pending these uses, the net proceeds will be invested in investment-grade, interest-bearing securities.

Description of capital stock

Our authorized capital stock consists of 100 million shares of common stock, $.01 par value, and 5 million shares of preferred stock, $.01 par value of which 1 million shares of preferred stock have been designated Series A junior participating preferred stock. As of April 30, 2002, there were 27,838,970 shares of common stock outstanding and no shares of preferred stock outstanding.

Common Stock

The holders of common stock are entitled to one vote for each share held of record on all matters submitted to a vote of the stockholders and do not have cumulative voting rights. Accordingly, holders of a majority of the shares of common stock entitled to vote in any election of directors may elect all of the directors standing for election. Subject to preferences that may be applicable to any outstanding shares of preferred stock, the holders of common stock are entitled to receive ratably such dividends as may be declared by the board of directors out of funds legally available therefor. Upon the liquidation, dissolution or winding up of Telik, holders of our common stock are entitled to share ratably in all assets remaining after payment of liabilities and the liquidation preferences of any outstanding shares of preferred stock. Holders of common stock have no preemptive rights and no right to convert their common stock into any other securities. There are no redemption or sinking fund provisions applicable to our common stock. All outstanding shares of common stock are, and all shares of common stock that may be issued under this prospectus will be, fully paid and non-assessable.

Preferred Stock

Pursuant to our amended and restated certificate of incorporation, our board of directors has the authority, without further action by the stockholders, to issue up to 5 million shares of preferred stock, in one or more series. One million shares of preferred stock have been designated as Series A junior participating preferred stock. Our board shall determine the rights, preferences, privileges and restrictions of the remaining preferred stock, including dividend rights, conversion rights, voting rights, terms of redemption, liquidation preferences, sinking fund terms and the number of shares constituting any series or the designation of any series.

We will fix the rights, preferences, privileges and restrictions of the preferred stock of each series in the certificate of designation relating to that series. We will incorporate by reference as an exhibit to the registration statement that includes this prospectus or as an exhibit to a current report on Form 8-K, the form of any certificate of designation that describes the terms of the series of preferred stock we are offering before the issuance of the related series of preferred stock. This description will include:

•

the title and stated value;

•

the number of shares we are offering;

•

the liquidation preference per share;

5

•

the purchase price;

•

the dividend rate, period and payment date and method of calculation for dividends;

•

whether dividends will be cumulative or non-cumulative and, if cumulative, the date from which dividends will accumulate;

•

the procedures for any auction and remarketing, if any;

•

the provisions for a sinking fund, if any;

•

the provisions for redemption or repurchase, if applicable, and any restrictions on our ability to exercise those redemption and repurchase rights;

•

any listing of the preferred stock on any securities exchange or market;

•

whether the preferred stock will be convertible into our common stock, and, if applicable, the conversion price, or how it will be calculated, and the conversion period;

•

whether the preferred stock will be exchangeable into debt securities, and, if applicable, the exchange price, or how it will be calculated, and the exchange period;

•

voting rights, if any, of the preferred stock;

•

preemption rights, if any;

•

restrictions on transfer, sale or other assignment, if any;

•

whether interests in the preferred stock will be represented by depositary shares;

•

a discussion of any material or special United States federal income tax considerations applicable to the preferred stock;

•

the relative ranking and preferences of the preferred stock as to dividend rights and rights if we liquidate, dissolve or wind up our affairs;

•

any limitations on issuance of any class or series of preferred stock ranking senior to or on a parity with the series of preferred stock as to dividend rights and rights if we liquidate, dissolve or wind up our affairs; and

•

any other specific terms, preferences, rights or limitations of, or restrictions on, the preferred stock.

If we issue shares of preferred stock under this prospectus, the shares will be fully paid and nonassessable and will not have, or be subject to, any preemptive or similar rights.

The General Corporation Law of Delaware provides that the holders of preferred stock will have the right to vote separately as a class on any proposal involving fundamental changes in the rights of holders of that preferred stock. This right is in addition to any voting rights that may be provided for in the applicable certificate of designation.

The issuance of preferred stock could adversely affect the voting power, conversion or other rights of holders of common stock. Preferred stock could be issued quickly with terms calculated to delay or prevent a change in control of our company or make removal of management more difficult. Additionally, the issuance of preferred stock may have the effect of decreasing the market price of common stock.

6

Registration Rights

As of the date hereof, holders of approximately 4.8 million shares of common stock, are entitled to certain rights with respect to registration of those shares under the Securities Act. If we propose to register any of our securities under the Securities Act, either for our own account or for the account of others, the holders of these shares are entitled to notice of the registration and are entitled to include, at our expense, their shares of common stock in the registration and any related underwriting, provided, among other conditions, that the underwriters may limit the number of shares to be included in the registration. In addition, the holders of these shares may require us, at our expense, on not more than two occasions and subject to certain limitations, to file a registration statement under the Securities Act with respect to their shares of common stock, and we will be required to use our best efforts to effect the registration.

Anti-Takeover Effects of Provisions of Delaware Law and Our Charter Documents.

Delaware Takeover Statute.    We are subject to the provisions of Section 203 of the Delaware General Corporation Law. In general, the statute prohibits a publicly held Delaware corporation from engaging in a business combination with an interested stockholder for a period of three years after the date of the transaction in which the person became an interested stockholder, unless the business combination is approved in a prescribed manner. For purposes of Section 203, a business combination includes a merger, asset sale or other transaction resulting in a financial benefit to the interested stockholder, and an interested stockholder is a person who, together with affiliates and associates, owns (or within three years prior, did own) 15% or more of the corporation's voting stock.

Charter Documents.    Our amended and restated certificate of incorporation requires that any action required or permitted to be taken by our stockholders must be effected at a duly called annual or special meeting of stockholders and may not be effected by a consent in writing. Additionally, our amended and restated certificate of incorporation:

•

substantially limits the use of cumulative voting in the election of directors;

•

provides for a board of directors, classified into three classes of directors;

•

provides that the authorized number of directors may be changed only by resolution of our board of directors; and

•

authorizes our board of directors to issue blank check preferred stock to increase the amount of outstanding shares.

Our amended and restated bylaws provide that candidates for director may be nominated only by our board of directors or by a stockholder who gives written notice to us no later than 60 days prior nor earlier than 90 days prior to the first anniversary of the last annual meeting of stockholders. The authorized number of directors is fixed in accordance with our amended and restated certificate of incorporation. Our board of directors may appoint new directors to fill vacancies or newly created directorships. Our amended and restated bylaws also limit who may call a special meeting of stockholders.

Delaware law and these charter provisions may have the effect of deterring hostile takeovers or delaying changes in control of our management, which could depress the market price of our common stock.

Rights Plan

In October 2001, our board of directors adopted a Stockholder Rights Plan, pursuant to which all stockholders of record as of November 14, 2001 received rights to purchase shares of a newly created

7

series of preferred stock. Each right entitles the registered holder to purchase from us one one-hundredth of a share of Series A junior participating preferred stock at an exercise price of $90 per right, subject to adjustment. The rights will become exercisable when a person or group acquires 20% or more of our outstanding common stock or ten business days after commencement or announcement of a tender or exchange offer for 20% or more of our outstanding common stock. If a person or group acquires 20% or more of our outstanding common stock, all right holders except such buyer will be entitled to acquire our common stock at a discount. In the event that Telik is acquired in a merger or other business combination transaction or 50% or more of its consolidated assets or earning power are sold to a person or group who has acquired 20% or more of our outstanding common stock, proper provision will be made so that each such holder of a right will thereafter have the right to receive, upon the exercise of the right, shares of common stock of the acquiring company which at the time of such transaction will have a market value of two times the exercise price of the right.

Our board of directors may terminate the Stockholder Rights Plan at any time, amend the rights plan without the approval of any holders of the rights or redeem the rights prior to the time a person or group acquires 20% or more of our common stock. Each preferred share will be entitled to a minimum preferential quarterly dividend payment of $1.00 but will be entitled to an aggregate dividend of 100 times the dividend declared per share of common stock. In the event of liquidation, the holders of the preferred shares would be entitled to receive a minimum preferential liquidation payment of $100 per share of common stock but will be entitled to an aggregate payment of 100 times the payment made per share of common stock. Each preferred share will have 100 votes, voting together with the shares of common stock. The rights are protected by customary anti-dilution provisions. The preferred shares rank junior to any other series of our preferred stock. These rights will expire on November 14, 2011.

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is Wells Fargo Bank Minnesota, N. A. Its address is 161 North Concord Exchange, South St. Paul, MN 55075-1139 and its telephone number is (800) 468-9716.

8

Description of debt securities

The following description, together with the additional information we include in any applicable prospectus supplements, summarizes the material terms and provisions of the debt securities that we may offer under this prospectus. While the terms we have summarized below will apply generally to any future debt securities we may offer, we will describe the particular terms of any debt securities that we may offer in more detail in the applicable prospectus supplement. The terms of any debt securities we offer under a prospectus supplement may differ from the terms we describe below.

We will issue the senior notes under the senior indenture which we will enter into with the trustee named in the senior indenture. We will issue the subordinated notes under the subordinated indenture which we will enter into with the trustee named in the subordinated indenture. We have filed forms of these documents as exhibits to the registration statement which includes this prospectus. We use the term "indentures" to refer to both the senior indenture and the subordinated indenture.

The indentures will be qualified under the Trust Indenture Act of 1939. We use the term "debenture trustee" to refer to either the senior trustee or the subordinated trustee, as applicable.

The following summaries of material provisions of the senior notes, the subordinated notes and the indentures are subject to, and qualified in their entirety by reference to, all the provisions of the indenture applicable to a particular series of debt securities. Except as we may otherwise indicate, the terms of the senior indenture and the subordinated indenture are identical.

General

We will describe in each prospectus supplement the following terms relating to a series of notes:

•

the title;

•

the principal amount being offered, and if a series, the total amount authorized and the total amount outstanding;

•

any limit on the amount that may be issued;

•

whether or not we will issue the series of notes in global form, the terms and who the depository will be;

•

the maturity date;

•

whether and under what circumstances, if any, we will pay additional amounts on any debt securities held by a person who is not a United States person for tax purposes, and whether we can redeem the debt securities if we have to pay such additional amounts;

•

the annual interest rate, which may be fixed or variable, or the method for determining the rate and the date interest will begin to accrue, the dates interest will be payable and the regular record dates for interest payment dates or the method for determining such dates;

•

whether or not the notes will be secured or unsecured, and the terms of any secured debt;

•

the terms of the subordination of any series of subordinated debt;

•

the place where payments will be payable;

•

our right, if any, to defer payment of interest and the maximum length of any such deferral period;

9

•

the date, if any, after which, and the price at which, we may, at our option, redeem the series of notes pursuant to any optional or provisional redemption provisions and the terms of those redemptions provisions;

•

the date, if any, on which, and the price at which we are obligated, pursuant to any mandatory sinking fund or analogous fund provisions or otherwise, to redeem, or at the holder's option to purchase, the series of notes and the currency or currency unit in which the debt securities are payable;

•

whether the indenture will restrict our ability to pay dividends, or will require us to maintain any asset ratios or reserves;

•

whether we will be restricted from incurring any additional indebtedness or issuing additional securities;

•

a discussion of any material or special United States federal income tax considerations applicable to the notes;

•

information describing any book-entry features;

•

provisions for a sinking fund purchase or other analogous fund, if any;

•

any provisions for payment of additional amounts for taxes and any provision for redemption, if we must pay such additional amount with respect to any debt security;

•

whether the debt securities are to be offered at a price such that they will be deemed to be offered at an "original issue discount" as defined in paragraph (a) of Section 1273 of the Internal Revenue Code;

•

the denominations in which we will issue the series of notes, if other than denominations of $1,000 and any integral multiple thereof; and

•

any other specific terms, preferences, rights or limitations of, or restrictions on, the debt securities, including any additional events of default or covenants provided with respect to the debt securities, and any terms which may be required by us or advisable under applicable laws or regulations.

Conversion or Exchange Rights

We will set forth in the prospectus supplement the terms on which a series of notes may be convertible into or exchangeable for common stock or other securities of ours. We will include provisions as to whether conversion or exchange is mandatory, at the option of the holder or at our option. We may include provisions pursuant to which the number of shares of common stock or other securities of ours that the holders of the series of notes receive would be subject to adjustment.

Consolidation, Merger or Sale

The indentures do not contain any covenant which restricts our ability to merge or consolidate, or sell, convey, transfer or otherwise dispose of all or substantially all of our assets. However, any successor to or acquirer of such assets must assume all of our obligations under the indentures or the notes, as appropriate.

If the debt securities are convertible for our other securities or securities of other entities, the person with whom we consolidate or merge or to whom we sell all of our property must make provisions for the conversion of the debt securities into securities which the holders of the debt securities would have received if they had converted the debt securities before the consolidation, merger or sale.

10

Events of Default Under the Indenture

The following are events of default under the indentures with respect to any series of notes that we may issue:

•

if we fail to pay interest when due and payable and our failure continues for 90 days and the time for payment has not been extended or deferred;

•

if we fail to pay the principal, or premium, if any, when due and payable and the time for payment has not been extended or delayed;

•

if we fail to observe or perform any other covenant contained in the notes or the indentures, other than a covenant specifically relating to another series of notes, and our failure continues for 90 days after we receive notice from the debenture trustee or holders of at least 25% in aggregate principal amount of the outstanding notes of the applicable series; and

•

if specified events of bankruptcy, insolvency or reorganization occur.

If an event of default with respect to notes of any series occurs and is continuing, other than an event of default specified in the last bullet point above, the debenture trustee or the holders of at least 25% in aggregate principal amount of the outstanding notes of that series, by notice to us in writing, and to the debenture trustee if notice is given by such holders, may declare the unpaid principal of, premium, if any, and accrued interest, if any, due and payable immediately. If an event of default specified in the last bullet point above occurs with respect to us, the principal amount of and accrued interest, if any, of each issue of debt securities then outstanding shall be due and payable without any notice or other action on the part of the debenture trustee or any holder.

The holders of a majority in principal amount of the outstanding notes of an affected series may waive any default or event of default with respect to the series and its consequences, except defaults or events of default regarding payment of principal, premium, if any, or interest, unless we have cured the default or event of default in accordance with the indenture. Any waiver shall cure the default or event of default.

Subject to the terms of the indentures, if an event of default under an indenture shall occur and be continuing, the debenture trustee will be under no obligation to exercise any of its rights or powers under such indenture at the request or direction of any of the holders of the applicable series of notes, unless such holders have offered the debenture trustee reasonable indemnity. The holders of a majority in principal amount of the outstanding notes of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the debenture trustee, or exercising any trust or power conferred on the debenture trustee, with respect to the notes of that series, provided that:

•

the direction so given by the holder is not in conflict with any law or the applicable indenture; and

•

subject to its duties under the Trust Indenture Act of 1939, the debenture trustee need not take any action that might involve it in personal liability or might be unduly prejudicial to the holders not involved in the proceeding.

A holder of the notes of any series will only have the right to institute a proceeding under the indentures or to appoint a receiver or trustee, or to seek other remedies if:

•

the holder has given written notice to the debenture trustee of a continuing event of default with respect to that series;

11

•

the holders of at least 25% in aggregate principal amount of the outstanding notes of that series have made written request, and such holders have offered reasonable indemnity to the debenture trustee to institute the proceeding as trustee; and

•

the debenture trustee does not institute the proceeding, and does not receive from the holders of a majority in aggregate principal amount of the outstanding notes of that series other conflicting directions within 90 days after the notice, request and offer.

These limitations do not apply to a suit instituted by a holder of notes if we default in the payment of the principal, premium, if any, or interest on, the notes.

We will periodically file statements with the debenture trustee regarding our compliance with specified covenants in the indentures.

Modification of Indenture; Waiver

We and the debenture trustee may change an indenture without the consent of any holders with respect to specific matters, including:

•

to fix any ambiguity, defect or inconsistency in the indenture;

•

to comply with the provisions described above under "Consolidation, Merger or Sale";

•

to comply with any requirements of the SEC in connection with the qualification of any indenture under the Trust Indenture Act of 1939;

•

to evidence and provide for the acceptance of appointment hereunder by a successor trustee;

•

to provide for uncertificated debt securities and to make all appropriate changes for such purpose;

•

to add to our covenants such new covenants, restrictions, conditions or provisions for the protection of the holders, and to make the occurrence, or the occurrence and the continuance, of a default in any such additional covenants, restrictions, conditions or provisions an event of default; or

•

to change anything that does not materially adversely affect the interests of any holder of notes of any series.

In addition, under the indentures, the rights of holders of a series of notes may be changed by us and the debenture trustee with the written consent of the holders of at least a majority in aggregate principal amount of the outstanding notes of each series that is affected. However, we and the debenture trustee may only make the following changes with the consent of each holder of any outstanding notes affected:

•

extending the fixed maturity of the series of notes;

•

reducing the principal amount, reducing the rate of or extending the time of payment of interest, or reducing any premium payable upon the redemption of any notes; or

•

reducing the percentage of notes, the holders of which are required to consent to any amendment, supplement, modification or waiver.

Discharge

Each indenture provides that we can elect to be discharged from our obligations with respect to one or more series of debt securities, except for obligations to:

•

register the transfer or exchange of debt securities of the series;

•

replace stolen, lost or mutilated debt securities of the series;

12

•

maintain paying agencies;

•

hold monies for payment in trust;

•

recover excess money held by the debenture trustee;

•

compensate and indemnify the debenture trustee; and

•

appoint any successor trustee.

In order to exercise our rights to be discharged, we must deposit with the debenture trustee money or government obligations sufficient to pay all the principal of, any premium, if any, and interest on, the debt securities of the series on the dates payments are due.

Form, Exchange and Transfer

We will issue the notes of each series only in fully registered form without coupons and, unless we otherwise specify in the applicable prospectus supplement, in denominations of $1,000 and any integral multiple thereof. The indentures provide that we may issue notes of a series in temporary or permanent global form and as book-entry securities that will be deposited with, or on behalf of, The Depository Trust Company or another depository named by us and identified in a prospectus supplement with respect to that series. See "Legal Ownership of Securities" for a further description of the terms relating to any book-entry securities.

At the option of the holder, subject to the terms of the indentures and the limitations applicable to global securities described in the applicable prospectus supplement, the holder of the notes of any series can exchange the notes for other notes of the same series, in any authorized denomination and of like tenor and aggregate principal amount.

Subject to the terms of the indentures and the limitations applicable to global securities set forth in the applicable prospectus supplement, holders of the notes may present the notes for exchange or for registration of transfer, duly endorsed or with the form of transfer endorsed thereon duly executed if so required by us or the security registrar, at the office of the security registrar or at the office of any transfer agent designated by us for this purpose. Unless otherwise provided in the notes that the holder presents for transfer or exchange, we will make no service charge for any registration of transfer or exchange, but we may require payment of any taxes or other governmental charges.

We will name in the applicable prospectus supplement the security registrar, and any transfer agent in addition to the security registrar, that we initially designate for any notes. We may at any time designate additional transfer agents or rescind the designation of any transfer agent or approve a change in the office through which any transfer agent acts, except that we will be required to maintain a transfer agent in each place of payment for the notes of each series.

If we elect to redeem the notes of any series, we will not be required to:

•

issue, register the transfer of, or exchange any notes of that series during a period beginning at the opening of business 15 days before the day of mailing of a notice of redemption of any notes that may be selected for redemption and ending at the close of business on the day of the mailing; or

•

register the transfer of or exchange any notes so selected for redemption, in whole or in part, except the unredeemed portion of any notes we are redeeming in part.

Information Concerning the Debenture Trustee

The debenture trustee, other than during the occurrence and continuance of an event of default under an indenture, undertakes to perform only those duties as are specifically set forth in the applicable

13

indenture. Upon an event of default under an indenture, the debenture trustee must use the same degree of care as a prudent person would exercise or use in the conduct of his or her own affairs. Subject to this provision, the debenture trustee is under no obligation to exercise any of the powers given it by the indentures at the request of any holder of notes unless it is offered reasonable security and indemnity against the costs, expenses and liabilities that it might incur.

Payment and Paying Agents

Unless we otherwise indicate in the applicable prospectus supplement, we will make payment of the interest on any notes on any interest payment date to the person in whose name the notes, or one or more predecessor securities, are registered at the close of business on the regular record date for the interest.

We will pay principal of and any premium and interest on the notes of a particular series at the office of the paying agents designated by us, except that unless we otherwise indicate in the applicable prospectus supplement, we will make interest payments by check which we will mail to the holder or by wire transfer to certain holders. Unless we otherwise indicate in a prospectus supplement, we will designate the corporate trust office of the debenture trustee in the City of New York as our sole paying agent for payments with respect to notes of each series. We will name in the applicable prospectus supplement any other paying agents that we initially designate for the notes of a particular series. We will maintain a paying agent in each place of payment for the notes of a particular series.

All money we pay to a paying agent or the debenture trustee for the payment of the principal of or any premium or interest on any notes which remains unclaimed at the end of two years after such principal, premium or interest has become due and payable will be repaid to us, and the holder of the security thereafter may look only to us for payment thereof.

Governing Law

The indentures and the notes will be governed by and construed in accordance with the laws of the State of New York, except to the extent that the Trust Indenture Act of 1939 is applicable.

Subordination of Subordinated Notes

The subordinated notes will be unsecured and will be subordinate and junior in priority of payment to certain of our other indebtedness to the extent described in a prospectus supplement. The subordinated indenture does not limit the amount of subordinated notes which we may issue. It also does not limit us from issuing any other secured or unsecured debt.

14

Description of warrants

The following description, together with the additional information we may include in any applicable prospectus supplements, summarizes the material terms and provisions of the warrants that we may offer under this prospectus and the related warrant agreements and warrant certificates. While the terms summarized below will apply generally to any warrants that we may offer, we will describe the particular terms of any series of warrants in more detail in the applicable prospectus supplement. If we indicate in the prospectus supplement, the terms of any warrants offered under that prospectus supplement may differ from the terms described below. Specific warrant agreements will contain additional important terms and provisions and will be incorporated by reference as an exhibit to the registration statement that includes this prospectus or as an exhibit to a current report on Form 8-K.

General

We will describe in the applicable prospectus supplement the terms of the series of warrants, including:

•

the offering price and aggregate number of warrants offered;

•

the currency for which the warrants may be purchased;

•

if applicable, the designation and terms of the securities with which the warrants are issued and the number of warrants issued with each such security or each principal amount of such security;

•

if applicable, the date on and after which the warrants and the related securities will be separately transferable;

•

in the case of warrants to purchase debt securities, the principal amount of debt securities purchasable upon exercise of one warrant and the price at, and currency in which, this principal amount of debt securities may be purchased upon such exercise;

•

in the case of warrants to purchase common stock or preferred stock, the number of shares of common stock or preferred stock, as the case may be, purchasable upon the exercise of one warrant and the price at which these shares may be purchased upon such exercise;

•

the effect of any merger, consolidation, sale or other disposition of our business on the warrant agreement and the warrants;

•

the terms of any rights to redeem or call the warrants;

•

any provisions for changes to or adjustments in the exercise price or number of securities issuable upon exercise of the warrants;

•

the dates on which the right to exercise the warrants will commence and expire;

•

the manner in which the warrant agreement and warrants may be modified;

•

federal income tax consequences of holding or exercising the warrants;

•

the terms of the securities issuable upon exercise of the warrants; and

•

any other specific terms, preferences, rights or limitations of or restrictions on the warrants.

Before exercising their warrants, holders of warrants will not have any of the rights of holders of the securities purchasable upon such exercise, including:

•

in the case of warrants to purchase debt securities, the right to receive payments of principal of, or premium, if any, or interest on, the debt securities purchasable upon exercise or to enforce covenants in the applicable indenture; or

15

•

in the case of warrants to purchase common stock or preferred stock, the right to receive dividends, if any, or, payments upon our liquidation, dissolution or winding up or to exercise voting rights, if any.

Exercise of Warrants

Each warrant will entitle the holder to purchase the securities that we specify in the applicable prospectus supplement at the exercise price that we describe in the applicable prospectus supplement. Unless we otherwise specify in the applicable prospectus supplement, holders of the warrants may exercise the warrants at any time up to 5:00 P.M. New York time on the expiration date that we set forth in the applicable prospectus supplement. After the close of business on the expiration date, unexercised warrants will become void.

Holders of the warrants may exercise the warrants by delivering the warrant certificate representing the warrants to be exercised together with specified information, and paying the required amount to the warrant agent in immediately available funds, as provided in the applicable prospectus supplement. We will set forth on the reverse side of the warrant certificate and in the applicable prospectus supplement the information that the holder of the warrant will be required to deliver to the warrant agent.

Upon receipt of the required payment and the warrant certificate properly completed and duly executed at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement, we will issue and deliver the securities purchasable upon such exercise. If fewer than all of the warrants represented by the warrant certificate are exercised, then we will issue a new warrant certificate for the remaining amount of warrants. If we so indicate in the applicable prospectus supplement, holders of the warrants may surrender securities as all or part of the exercise price for warrants.

Enforceability of Rights by Holders of Warrants

Each warrant agent will act solely as our agent under the applicable warrant agreement and will not assume any obligation or relationship of agency or trust with any holder of any warrant. A single bank or trust company may act as warrant agent for more than one issue of warrants. A warrant agent will have no duty or responsibility in case of any default by us under the applicable warrant agreement or warrant, including any duty or responsibility to initiate any proceedings at law or otherwise, or to make any demand upon us. Any holder of a warrant may, without the consent of the related warrant agent or the holder of any other warrant, enforce by appropriate legal action its right to exercise, and receive the securities purchasable upon exercise of, its warrants.

16

Legal ownership of securities

We can issue securities in registered form or in the form of one or more global securities. We describe global securities in greater detail below. We refer to those persons who have securities registered in their own names on the books that we or any applicable trustee maintain for this purpose as the "holders" of those securities. These persons are the legal holders of the securities. We refer to those persons who, indirectly through others, own beneficial interests in securities that are not registered in their own names, as "indirect holders" of those securities. As we discuss below, indirect holders are not legal holders, and investors in securities issued in book-entry form or in street name will be indirect holders.

Book-Entry Holders

We may issue securities in book-entry form only, as we will specify in the applicable prospectus supplement. This means securities may be represented by one or more global securities registered in the name of a financial institution that holds them as depositary on behalf of other financial institutions that participate in the depositary's book-entry system. These participating institutions, which are referred to as participants, in turn, hold beneficial interests in the securities on behalf of themselves or their customers.

Only the person in whose name a security is registered is recognized as the holder of that security. Securities issued in global form will be registered in the name of the depositary or its participants. Consequently, for securities issued in global form, we will recognize only the depositary as the holder of the securities, and we will make all payments on the securities to the depositary. The depositary passes along the payments it receives to its participants, which in turn pass the payments along to their customers who are the beneficial owners. The depositary and its participants do so under agreements they have made with one another or with their customers; they are not obligated to do so under the terms of the securities.

As a result, investors in a book-entry security will not own securities directly. Instead, they will own beneficial interests in a global security, through a bank, broker or other financial institution that participates in the depositary's book-entry system or holds an interest through a participant. As long as the securities are issued in global form, investors will be indirect holders, and not holders, of the securities.

Street Name Holders

We may terminate a global security or issue securities in non-global form. In these cases, investors may choose to hold their securities in their own names or in "street name." Securities held by an investor in street name would be registered in the name of a bank, broker or other financial institution that the investor chooses, and the investor would hold only a beneficial interest in those securities through an account he or she maintains at that institution.

For securities held in street name, we will recognize only the intermediary banks, brokers and other financial institutions in whose names the securities are registered as the holders of those securities, and we will make all payments on those securities to them. These institutions pass along the payments they receive to their customers who are the beneficial owners, but only because they agree to do so in their customer agreements or because they are legally required to do so. Investors who hold securities in street name will be indirect holders, not holders, of those securities.

17

Legal Holders

Our obligations, as well as the obligations of any applicable trustee and of any third parties employed by us or a trustee, run only to the legal holders of the securities. We do not have obligations to investors who hold beneficial interests in global securities, in street name or by any other indirect means. This will be the case whether an investor chooses to be an indirect holder of a security or has no choice because we are issuing the securities only in global form.

For example, once we make a payment or give a notice to the holder, we have no further responsibility for the payment or notice even if that holder is required, under agreements with depositary participants or customers or by law, to pass it along to the indirect holders but does not do so. Similarly, we may want to obtain the approval of the holders to amend an indenture, to relieve us of the consequences of a default or of our obligation to comply with a particular provision of the indenture or for other purposes. In such an event, we would seek approval only from the holders, and not the indirect holders, of the securities. Whether and how the holders contact the indirect holders is up to the holders.

Special Considerations For Indirect Holders

If you hold securities through a bank, broker or other financial institution, either in book-entry form or in street name, you should check with your own institution to find out:

•

how it handles securities payments and notices;

•

whether it imposes fees or charges;

•

how it would handle a request for the holders' consent, if ever required;

•

whether and how you can instruct it to send you securities registered in your own name so you can be a holder, if that is permitted in the future;

•

how it would exercise rights under the securities if there were a default or other event triggering the need for holders to act to protect their interests; and

•

if the securities are in book-entry form, how the depositary's rules and procedures will affect these matters.

Global Securities

A global security is a security which represents one or any other number of individual securities held by a depositary. Generally, all securities represented by the same global securities will have the same terms.

Each security issued in book-entry form will be represented by a global security that we deposit with and register in the name of a financial institution or its nominee that we select. The financial institution that we select for this purpose is called the depositary. Unless we specify otherwise in the applicable prospectus supplement, The Depository Trust Company, New York, New York, known as DTC, will be the depositary for all securities issued in book-entry form.

A global security may not be transferred to or registered in the name of anyone other than the depositary, its nominee or a successor depositary, unless special termination situations arise. We describe those situations below under "Special Situations When a Global Security Will Be Terminated." As a result of these arrangements, the depositary, or its nominee, will be the sole registered owner and holder of all securities represented by a global security, and investors will be permitted to own only beneficial interests in a global security. Beneficial interests must be held by means of an account with a broker, bank or other financial institution that in turn has an account with the depositary or with

18

another institution that does. Thus, an investor whose security is represented by a global security will not be a holder of the security, but only an indirect holder of a beneficial interest in the global security.

If the prospectus supplement for a particular security indicates that the security will be issued in global form only, then the security will be represented by a global security at all times unless and until the global security is terminated. If termination occurs, we may issue the securities through another book-entry clearing system or decide that the securities may no longer be held through any book-entry clearing system.

Special Considerations For Global Securities

As an indirect holder, an investor's rights relating to a global security will be governed by the account rules of the investor's financial institution and of the depositary, as well as general laws relating to securities transfers. We do not recognize an indirect holder as a holder of securities and instead deal only with the depositary that holds the global security.

If securities are issued only in the form of a global security, an investor should be aware of the following:

•

An investor cannot cause the securities to be registered in his or her name, and cannot obtain non-global certificates for his or her interest in the securities, except in the special situations we describe below;

•

An investor will be an indirect holder and must look to his or her own bank or broker for payments on the securities and protection of his or her legal rights relating to the securities, as we describe above;

•

An investor may not be able to sell interests in the securities to some insurance companies and to other institutions that are required by law to own their securities in non-book-entry form;

•

An investor may not be able to pledge his or her interest in a global security in circumstances where certificates representing the securities must be delivered to the lender or other beneficiary of the pledge in order for the pledge to be effective;

•

The depositary's policies, which may change from time to time, will govern payments, transfers, exchanges and other matters relating to an investor's interest in a global security. We and any applicable trustee have no responsibility for any aspect of the depositary's actions or for its records of ownership interests in a global security. We and the trustee also do not supervise the depositary in any way;

•

The depositary may, and we understand that DTC will, require that those who purchase and sell interests in a global security within its book-entry system use immediately available funds, and your broker or bank may require you to do so as well; and

•

Financial institutions that participate in the depositary's book-entry system, and through which an investor holds its interest in a global security, may also have their own policies affecting payments, notices and other matters relating to the securities. There may be more than one financial intermediary in the chain of ownership for an investor. We do not monitor and are not responsible for the actions of any of those intermediaries.

Special Situations When A Global Security Will Be Terminated

In a few special situations described below, the global security will terminate and interests in it will be exchanged for physical certificates representing those interests. After that exchange, the choice of whether to hold securities directly or in street name will be up to the investor. Investors must consult

19

their own banks or brokers to find out how to have their interests in securities transferred to their own name, so that they will be direct holders. We have described the rights of holders and street name investors above.

The global security will terminate when the following special situations occur:

•

if the depositary notifies us that it is unwilling, unable or no longer qualified to continue as depositary for that global security and we do not appoint another institution to act as depositary within 90 days;

•

if we notify any applicable trustee that we wish to terminate that global security; or

•

if an event of default has occurred with regard to securities represented by that global security and has not been cured or waived.

The prospectus supplement may also list additional situations for terminating a global security that would apply only to the particular series of securities covered by the prospectus supplement. When a global security terminates, the depositary, and not we or any applicable trustee, is responsible for deciding the names of the institutions that will be the initial direct holders.

20

Plan of distribution

We may sell the securities through underwriters or dealers, through agents, or directly to one or more purchasers. The prospectus supplement will describe the terms of the offering of the securities, including:

•

the name or names of any underwriters, if any;

•

the purchase price of the securities and the proceeds we will receive from the sale;

•

any over-allotment options under which underwriters may purchase additional securities from us;

•

any agency fees or underwriting discounts and other items constituting agents' or underwriters' compensation;

•

any initial public offering price;

•

any discounts or concessions allowed or reallowed or paid to dealers; and

•

any securities exchange or market on which the securities may be listed.

Only underwriters named in the prospectus supplement are underwriters of the securities offered by the prospectus supplement.

If underwriters are used in the sale, they will acquire the securities for their own account and may resell them from time to time in one or more transactions at a fixed public offering price or at varying prices determined at the time of sale. The obligations of the underwriters to purchase the securities will be subject to the conditions set forth in the applicable underwriting agreement. We may offer the securities to the public through underwriting syndicates represented by managing underwriters or by underwriters without a syndicate. Subject to certain conditions, the underwriters will be obligated to purchase all the securities of the series offered by the prospectus supplement. Any public offering price and any discounts or concessions allowed or reallowed or paid to dealers may change from time to time. We may use underwriters with whom we have a material relationship. We will describe in the prospectus supplement, naming the underwriter, the nature of any such relationship.

We may sell securities directly or through agents we designate from time to time. We will name any agent involved in the offering and sale of securities and we will describe any commissions we will pay the agent in the prospectus supplement.

Unless the prospectus supplement states otherwise, our agent will act on a best-efforts basis for the period of its appointment.

We may authorize agents or underwriters to solicit offers by certain types of institutional investors to purchase securities from us at the public offering price set forth in the prospectus supplement pursuant to delayed delivery contracts providing for payment and delivery on a specified date in the future. We will describe the conditions to these contracts and the commissions we must pay for solicitation of these contracts in the prospectus supplement.

We may provide agents and underwriters with indemnification against certain civil liabilities, including liabilities under the Securities Act, or contribution with respect to payments that the agents or underwriters may make with respect to such liabilities. Agents and underwriters may engage in transactions with, or perform services for, us in the ordinary course of business.

All securities we offer, other than common stock, will be new issues of securities with no established trading market. Any underwriters may make a market in these securities, but will not be obligated to

21

do so and may discontinue any market making at any time without notice. We cannot guarantee the liquidity of the trading markets for any securities.

Any underwriter may engage in overallotment, stabilizing transactions, short covering transactions and penalty bids in accordance with Regulation M under the Exchange Act. Overallotment involves sales in excess of the offering size, which create a short position. Stabilizing transactions permit bids to purchase the underlying security so long as the stabilizing bids do not exceed a specified maximum. Short covering transactions involve purchases of the securities in the open market after the distribution is completed to cover short positions. Penalty bids permit the underwriters to reclaim a selling concession from a dealer when the securities originally sold by the dealer are purchased in a covering transaction to cover short positions. Those activities may cause the price of the securities to be higher than it would otherwise be. If commenced, the underwriters may discontinue any of the activities at any time.

Any underwriters who are qualified market makers on the Nasdaq National Market may engage in passive market making transactions in the securities on the Nasdaq National Market in accordance with Rule 103 of Regulation M, during the business day prior to the pricing of the offering, before the commencement of offers or sales of the securities. Passive market makers must comply with applicable volume and price limitations and must be identified as passive market makers. In general, a passive market maker must display its bid at a price not in excess of the highest independent bid for such security; if all independent bids are lowered below the passive market maker's bid, however, the passive market maker's bid must then be lowered when certain purchase limits are exceeded.

In compliance with NASD guidelines, the maximum consideration or discount to be received by any NASD member or independent broker dealer may not exceed 8% of the aggregate amount of the securities offered pursuant to this prospectus and any applicable prospectus supplement.

22

Legal matters

The validity of the securities being offered hereby will be passed upon by Cooley Godward LLP, San Francisco, California. As of the date of this prospectus, certain partners and associates of Cooley Godward LLP own an aggregate of 28,276 shares of our common stock through investment partnerships. Deborah A. Marshall, a partner at Cooley Godward LLP, is our Secretary.

Experts

Ernst & Young LLP, independent auditors, have audited our financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2001, as set forth in their report, which is incorporated by reference in this prospectus and elsewhere in the registration statement. Our financial statements are incorporated by reference in reliance on Ernst & Young LLP's report, given on their authority as experts in accounting and auditing.

Where you can find more information

We are a reporting company and file annual, quarterly and current reports, proxy statements and other information with the SEC. We have filed with the SEC a registration statement on Form S-3 under the Securities Act with respect to the shares of common stock and preferred stock, debt securities and/or warrants we are offering under this prospectus. This prospectus does not contain all of the information set forth in the registration statement and the exhibits to the registration statement. For further information with respect to us and the securities we are offering under this prospectus, we refer you to the registration statement and the exhibits and schedules filed as a part of the registration statement. You may read and copy the registration statement, as well as our reports, proxy statements and other information, at the SEC's public reference rooms at Room 1024, 450 Fifth Street, N.W., Washington, D.C. 20549, as well as at the SEC's regional offices at 500 West Madison Street, Suite 1400, Chicago, IL 60661 and at 233 Broadway, New York, NY 10279. You can request copies of these documents by writing to the SEC and paying a fee for the copying cost. Please call the SEC at 1-800-SEC-0330 for more information about the operation of the public reference rooms. Our SEC filings are also available at the SEC's web site at "http://www.sec.gov." In addition, you can read and copy our SEC filings at the office of the National Association of Securities Dealers, Inc. at 1735 K Street, N.W., Washington, D.C. 20006.

The SEC allows us to "incorporate by reference" information that we file with it, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is an important part of this prospectus. Information in this prospectus supersedes information incorporated by reference that we filed with the SEC prior to the date of this prospectus, while information that we file later with the SEC will automatically update and supersede this information. We incorporate by reference into this registration statement and prospectus the documents listed below and any future filings we will make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act after the date of the initial registration statement but prior to effectiveness of the registration statement and after the date of this prospectus but prior to the termination of the offering of the securities covered by this prospectus.

The following documents filed with the SEC are incorporated by reference in this prospectus:

1.

Our annual report on Form 10-K, for the year ended December 31, 2001;

2.

Our quarterly report on Form 10-Q for the quarter ended March 31, 2002; and

23

3.

The description of our common stock set forth in our registration statement on Form 8-A, filed with the SEC on August 7, 2000, including any amendments or reports filed for the purposes of updating this description.

We will furnish without charge to you, on written or oral request, a copy of any or all of the documents incorporated by reference, including exhibits to these documents. You should direct any requests for documents to Telik, Inc., Attention: Investor Relations, Telik, Inc., 750 Gateway Boulevard, South San Francisco, CA 94080, telephone: (650) 244-9303.

24

QuickLinks

TABLE OF CONTENTS
Prospectus supplement summary
The offering
Summary financial data
Risk factors
Use of proceeds
Price range of common stock
Dividend policy
Capitalization
Dilution
Underwriting
Legal matters
TABLE OF CONTENTS
About this prospectus
Telik
The securities we may offer
Forward-looking information
Ratio of earnings to fixed charges
Use of proceeds
Description of capital stock
Description of debt securities
Description of warrants
Legal ownership of securities
Plan of distribution
Legal matters
Experts
Where you can find more information