FWP

Issuer Free Writing Prospectus
Filed Pursuant to Rule 433
Dated January 5, 2023
Relating to Preliminary Prospectus Supplement, dated January 4, 2023
Registration Statement No. 333-269111

This free writing prospectus relates only to the public offering of shares of common stock and pre-funded warrants to purchase shares of common stock of Geron Corporation and should be read together with the preliminary prospectus supplement, dated January 4, 2023, or the Preliminary Prospectus Supplement, and the accompanying prospectus, in each case, including the documents incorporated by reference therein. The information in this free writing prospectus updates and, to the extent inconsistent, supersedes the information in the Preliminary Prospectus Supplement. This free writing prospectus supplements the Preliminary Prospectus Supplement primarily to reflect the addition of certain pre-funded warrants, and the shares of common stock issuable upon the exercise of such pre-funded warrants, to the securities being offered by Geron Corporation. Except as otherwise indicated, all information in this free writing prospectus and the Preliminary Prospectus Supplement assumes no exercise by the underwriters of their option to purchase additional shares of common stock and no exercise of the pre-funded warrants included in this offering.

This free writing prospectus is qualified in its entirety by reference to the Preliminary Prospectus Supplement and the accompanying prospectus, in each case, including the documents incorporated by reference therein. Financial information and other information presented in the Preliminary Prospectus Supplement or incorporated by reference therein is deemed to have changed to the extent affected by the changes described herein. This free writing prospectus should be read together with the Preliminary Prospectus Supplement and the accompanying prospectus, in each case, including the documents incorporated by reference therein, before making a decision in connection with an investment in the securities. Capitalized terms used in this free writing prospectus but not defined have the meanings given to them in the Preliminary Prospectus Supplement.

If you purchase securities in this offering, you will experience immediate dilution in your investment. You will experience further dilution if we issue additional equity securities in future fundraising transactions.

Purchasers of our securities in this offering will pay a price per share of common stock (or pre-funded warrant at the public offering price less $0.001) that exceeds the net tangible book value per share of our common stock. After giving effect to this offering at the public offering price of $ per share of common stock (or pre-funded warrant at the public offering price less $0.001) and, and after deducting the underwriting discounts and commissions and estimated offering expenses payable by us (but excluding the shares of common stock to be issued and the proceeds received, if any, from exercises of the pre-funded warrants being offered in this offering), you will experience immediate dilution of $ per share, representing the difference between our as adjusted net tangible book value per share as of September 30, 2022 after giving effect to this offering (but without giving effect to the exercise of the pre-funded warrants being offered in this offering) and the public offering price. Furthermore, if the underwriters exercise their option to purchase additional shares, you will experience further dilution. See the section entitled “Dilution” below for a more detailed illustration of the dilution you would incur if you purchase our securities in this offering.

If we issue additional common stock, or securities convertible into or exchangeable or exercisable for common stock, including shares issuable upon the potential exercise of currently outstanding warrants, our stockholders, including investors who purchase our securities in this offering, will experience additional dilution, and any such issuances may cause the price of our common stock to decrease. We also cannot assure you that we will be able to sell shares or other securities in any other offering at a price per share that is equal to or greater than either the price per share of common stock (or pre-funded warrant) paid by investors in this offering, and investors purchasing shares or other securities in the future could have rights superior to investors in this offering.

There is no public market for the pre-funded warrants being offered by us in this offering.

There is no established public trading market for the pre-funded warrants being sold in this offering, and we do not expect a market to develop. In addition, we do not intend to apply to list the pre-funded warrants on any securities exchange or recognized trading system. Without an active market, the liquidity of the pre-funded warrants will be limited.

Holders of the pre-funded warrants will have no rights as common stockholders until they acquire our common stock.

Until you acquire shares of our common stock upon exercise of the pre-funded warrants, you will have no rights with respect to our common stock issuable upon exercise of the pre-funded warrants, including the right to receive dividend payments, vote or respond to tender offers. Upon exercise of your pre-funded warrants, you will be entitled to exercise the rights of a common stockholder only as to matters for which the record date occurs after the exercise date.

We will not receive any meaningful amount of additional funds upon the exercise of the pre-funded warrants.

Each pre-funded warrant will be exercisable until it is fully exercised and by means of payment of the nominal cash purchase price upon exercise or by means of a “cashless exercise” according to a formula set forth in the pre-funded warrant. Accordingly, we will not receive any meaningful additional funds upon the exercise of the pre-funded warrants.

Significant holders or beneficial holders of shares of our common stock may not be permitted to exercise the pre-funded warrants that they hold.

A holder (together with its affiliates and other attribution parties) may not exercise any portion of a pre-funded warrant to the extent that immediately prior to or after giving effect to such exercise the holder would own more

than 9.99% of our outstanding common stock immediately after exercise, which percentage may be changed at the holder's election to a higher or lower percentage not in excess of 19.99% (if exceeding such percentage would result in a change of control under Nasdaq Listing Rule 5635(b) or any successor rule) upon 61 days' notice to us subject to the terms of the pre-funded warrants. As a result, you may not be able to exercise your pre-funded warrants for shares of our common stock at a time when it would be financially beneficial for you to do so. In such a circumstance, you could seek to sell your pre-funded warrants to realize value, but you may be unable to do so in the absence of an established trading market and due to applicable transfer restrictions.

We estimate that the net proceeds to us from the sale of the shares of common stock and pre-funded warrants to purchase shares of common stock that we are offering, excluding the proceeds, if any, from the exercise of the pre-funded warrants offered hereby, will be approximately $ , or $ if the underwriters exercise their option to purchase additional shares in full, based on the public offering price of $ per share of common stock (or pre-funded warrants at the public offering price less $0.001), and after deducting the underwriting discounts and commissions and estimated offering expenses payable by us.

We may not sell any pre-funded warrants in this offering. If we sell any pre-funded warrants, we will receive only $0.001 per share upon exercise thereof.

Our net tangible book value as of September 30, 2022 was approximately $108.2 million, or $0.28 per share. We calculate net tangible book value per share by dividing the net tangible book value, which is tangible assets less total liabilities, by the number of outstanding shares of our common stock as of September 30, 2022.

Dilution in net tangible book value per share represents the difference between the amount per share paid by purchasers of securities in this offering, and the as adjusted net tangible book value per share of our common stock immediately after completion of this offering.

After giving effect to the sale by us of (i) shares of our common stock in this public offering at the public offering price of $ per share and (ii) pre-funded warrants to purchase shares of our common stock in this public offering at the public offering price minus $0.001 (excluding, in each case, the shares of common stock to be issued and the proceeds received, if any, from exercises of the pre-funded warrants), and after deducting the underwriting discounts and commissions and estimated offering expenses payable by us, our as adjusted net tangible book value as of September 30, 2022 would have been approximately $ million, or $ per share. This represents an immediate increase in the net tangible book value of $ per share to existing stockholders and immediate dilution in net tangible book value of $ per share to investors purchasing securities in this offering. The following table illustrates this dilution on a per share basis:

If the underwriters exercise in full their option to purchase additional shares of common stock, the as adjusted net tangible book value after this offering would be $ per share of our common stock, representing an increase of as adjusted net tangible book value of $ per share to our existing stockholders and an immediate dilution of $ per share to investors purchasing shares in this offering.

Investors who purchase common stock upon the exercise of the pre-funded warrants offered hereby may experience dilution depending on our net tangible book value at the time of exercise.

The foregoing tables and calculations (other than historical net tangible book value) are based on 381,214,326 shares of common stock outstanding as of September 30, 2022. This number excludes the shares of common stock issuable upon exercise of the pre-funded warrants offered hereby, and also excludes, as of September 30, 2022, the following:

In addition, stock options to purchase 2,347,280 shares at a weighted-average exercise price of $2.18 per share and stock awards of 2,970 shares have been granted between September 30, 2022 and the date of the prospectus supplement.

The number of shares of common stock to be outstanding immediately following this offering does not include up to approximately $79.1 million of our common stock that remained available for sale as of September 30, 2022 under the at market issuance sales agreement we entered into with B. Riley Securities, Inc., dated as of September 4, 2020, or the Sales Agreement. Since December 31, 2021, we have not sold any shares under the Sales Agreement.

We have not yet determined whether the pre-funded warrants will be classified and accounted for as liabilities or as stockholders’ equity.

To the extent that options or the warrants outstanding as of September 30, 2022 have been or are exercised, or other shares are issued, investors purchasing our securities in this offering will experience further dilution. In addition, we may choose to raise additional capital, including pursuant to the Sales Agreement, due to market conditions or strategic considerations even if we believe we have sufficient funds for our current or future operating plans. To the extent that additional capital is raised through the sale of equity or convertible debt securities, the issuance of these securities could result in further dilution to our stockholders.

We are offering shares of our common stock, or for certain investors that so choose, in lieu of shares of common stock and pre-funded warrants to purchase shares of our common stock, or the pre-funded warrants. The common stock and the pre-funded warrants will be sold at the same time. The shares of common stock and the pre-funded warrants are immediately separable and will be issued separately. The shares of common stock issuable from time to time upon exercise of the pre-funded warrants, if any, are also being offered pursuant to the prospectus supplement and the accompanying prospectus.

As of the date of the prospectus supplement, our restated certificate of incorporation, as amended, authorizes us to issue 675,000,000 shares of common stock, par value $0.001 per share, and 3,000,000 shares of preferred stock, par value $0.001 per share. 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. Subject to preferences that may be applicable to any outstanding shares of the 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 legally available funds. Upon our liquidation, dissolution or winding up, 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 legally available for distribution to stockholders. 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 the common stock. The rights, preferences and privileges of the holders of common stock are subject to, and may be adversely affected by, the rights of the holders of shares of any series of preferred stock which we may designate in the future. For more information, see “Description of Capital Stock” in Exhibit 4.1 to our Annual Report on Form 10-K for the year ended December 31, 2021, which Exhibit 4.1 is incorporated by reference into the prospectus supplement and the accompanying prospectus.

Our common stock is listed on The Nasdaq Global Select Market under the symbol “GERN.” The transfer agent and registrar for our common stock is Computershare Trust Company, N.A.

The material terms and provisions of the pre-funded warrants being issued in this offering are summarized below. The following description is subject to, and qualified in its entirety by, the form of pre-funded warrant which will be filed as an exhibit to a Current Report on Form 8-K to be filed by us with the SEC in connection with this offering. You should review the form of pre-funded warrant for a complete description of the terms and conditions applicable to the pre-funded warrants.

Exercisability. The pre-funded warrants will be immediately exercisable, at the option of each holder, in whole or in part by delivering to us a duly executed exercise notice and by payment in full in immediately available funds for the number of shares of common stock purchased upon such exercise. The holder may also exercise the pre-funded warrant through a “cashless exercise,” in which case, the holder would receive upon such exercise, the net number of shares of common stock determined according to the formula set forth in the pre-funded warrant. The exercise price must be paid by the holder in cash in immediately available funds.

Exercise Limitations. A holder (together with its affiliates and other attribution parties) may not exercise any portion of a pre-funded warrant to the extent that immediately prior to or after giving effect to such exercise the holder would own more than 9.99% of our outstanding common stock immediately after exercise, which percentage may be changed at the holder's election to a higher or lower percentage not in excess of 19.99% (if exceeding such percentage would result in a change of control under Nasdaq Listing Rule 5635(b) or any successor rule) upon 61 days' notice to us subject to the terms of the pre-funded warrants.

Exercise Price. Each pre-funded warrant offered hereby has an initial exercise price per share equal to $0.001. The pre-funded warrants are immediately exercisable and may be exercised at any time until the pre-funded

warrants are exercised in full. The exercise price and number of shares of common stock issuable upon exercise is subject to adjustment in the event of stock dividends and distributions, stock splits, stock combinations, reclassifications or similar events affecting our common stock.

Transferability. Subject to compliance with any applicable securities laws, the pre-funded warrants are separately tradeable immediately after issuance at the option of the holders and may be transferred at the option of the holders.

No Listing. There is no established public trading market for the pre-funded warrants and we do not expect a market to develop. In addition, we do not intend to apply for listing of the pre-funded warrants on any securities exchange or recognized trading system, including Nasdaq. Without an active market, the liquidity of the pre-funded warrants will be limited.

Fundamental Transactions. In the event of a fundamental transaction, as described in the pre-funded warrants and generally including any reorganization, recapitalization or reclassification of our common stock, the sale, transfer or other disposition of all or substantially all of our properties or assets, our consolidation or merger with or into another person, the acquisition of more than 50% of our outstanding common stock, or any person or group becoming the beneficial owner of more than 50% of the voting power represented by our outstanding common stock, the holders of the pre-funded warrants will be entitled to receive upon exercise of the pre-funded warrants the kind and amount of securities, cash or other property that the holders would have received had they exercised the pre-funded warrants immediately prior to such fundamental transaction.

Rights as a Stockholder. Except for the right to participate in certain dividends and distributions and as otherwise provided in the pre-funded warrant or by virtue of a holder's ownership of shares of our common stock, the holders of the pre-funded warrants do not have the rights or privileges of holders of our common stock, including any voting rights, until they exercise their pre-funded warrants.

The following is a general discussion of the material U.S. federal income tax considerations of the purchase, ownership and disposition of shares of our common stock issued pursuant to this offering, or the shares, and the purchase, ownership and disposition of pre-funded warrants to purchase shares of our common stock issued pursuant to this offering, or the pre-funded warrants. The shares and the pre-funded warrants are collectively referred to herein as our “securities.” All prospective holders of our securities should consult their tax advisors with respect to the U.S. federal, state, local and non-U.S. tax consequences of the purchase, ownership and disposition of our securities.

This discussion is not a complete analysis of all potential U.S. federal income tax consequences relating to the purchase, ownership and disposition of our securities. This discussion is based on current provisions of the U.S. Internal Revenue Code of 1986, as amended, which we refer to as the Code, existing U.S. Treasury Regulations promulgated thereunder, published administrative pronouncements and rulings of the U.S. Internal Revenue Service, or the IRS, and judicial decisions, all as in effect as of the date of the prospectus supplement. These authorities are subject to change and to differing interpretation, possibly with retroactive effect. Any change or differing interpretation could alter the tax consequences to holders described in this discussion. There can be no assurance that a court or the IRS will not challenge one or more of the tax consequences described herein, and we have not obtained, nor do we intend to obtain, a ruling with respect to the U.S. federal income tax consequences to a holder of the purchase, ownership or disposition of our securities.

We assume in this discussion that a holder holds our securities as a “capital asset” within the meaning of Section 1221 of the Code (generally, property held for investment). This discussion does not address all aspects of U.S. federal income taxation that may be relevant to a particular holder in light of that holder’s individual circumstances, nor does it address any alternative minimum, Medicare contribution, estate or gift tax consequences, or any aspects of U.S. state, local or non-U.S. taxes or any other U.S. federal tax laws. This discussion also does not address consequences relevant to holders subject to special tax rules, such as holders that own, or are deemed to own, more than 5% of our capital stock (except to the extent specifically set forth below), corporations that accumulate earnings to avoid U.S. federal income tax, tax-exempt organizations, governmental organizations, banks, financial institutions, investment funds, insurance companies, brokers, dealers or traders in securities, commodities or currencies, regulated investment companies or real estate investment trusts, persons that have a “functional currency” other than the U.S. dollar, tax-qualified retirement plans, holders who hold or receive our securities pursuant to the exercise of employee stock options or otherwise as compensation, holders holding our securities as part of a hedge, straddle or other risk reduction strategy, conversion transaction or other integrated investment, holders deemed to sell our securities under the constructive sale provisions of the Code, holders subject to special tax accounting rules under Section 451(b) of the Code, controlled foreign corporations, passive foreign investment companies and certain former U.S. citizens or long-term residents.

In addition, this discussion does not address the tax treatment of partnerships (or entities or arrangements that are treated as partnerships or disregarded entities for U.S. federal income tax purposes) or persons that hold our securities through such partnerships. If a partnership, including any entity or arrangement treated as a partnership for U.S. federal income tax purposes, holds our securities, the U.S. federal income tax treatment of a partner in such partnership generally will depend upon the status of the partner, and the activities of the partnership and certain determinations made at the partner level. Such partners and partnerships should consult their tax advisors regarding the tax consequences of the purchase, ownership and disposition of our securities.

Although it is not entirely free from doubt, we believe a pre-funded warrant should be treated as a share for U.S. federal income tax purposes and a holder of pre-funded warrants should generally be taxed in the same manner as a holder of shares, as described below. Accordingly, no gain or loss should be recognized upon the exercise of a pre-funded warrant and, upon exercise, the holding period of a pre-funded warrant should carry over to the share received. Similarly, the tax basis of the pre-funded warrant should carry over to the shares received upon exercise, increased by the exercise price of $0.001 per share. However, our characterization is not binding on the IRS, and the IRS may treat the pre-funded warrants as warrants to acquire our shares. If so, the amount and character of your gain

or loss with respect to an investment in our pre-funded warrants could change. Accordingly, each holder should consult his, her or its own tax advisor regarding the risks associated with the acquisition of pre-funded warrants pursuant to this offering (including potential alternative characterizations). The balance of this discussion generally assumes that the characterization described above is respected for U.S. federal income tax purposes.

In general, a “U.S. holder” means a beneficial owner of our securities (other than a partnership or an entity or arrangement treated as a partnership for U.S. federal income tax purposes) that is, for U.S. federal income tax purposes:

We do not anticipate declaring or paying any future distributions. However, if we do make distributions on our securities, such distributions will constitute dividends to the extent paid from our current or accumulated earnings and profits, as determined under U.S. federal income tax principles, and will be includible in your income as ordinary income when received. However, with respect to dividends received by individuals, such dividends are generally taxed at the lower applicable long-term capital gains rates, provided certain holding period and other requirements are satisfied. If a distribution exceeds our current and accumulated earnings and profits, the excess will be treated as a tax-free return of the U.S. holder’s investment, up to such U.S. holder’s adjusted tax basis in our securities. Any remaining excess will be treated as capital gain from the sale or exchange of such securities, subject to the tax treatment described below in “—Sale or Other Taxable Disposition of the Shares or Pre-Funded Warrants.”

Upon the sale, exchange or other taxable disposition of our securities, a U.S. holder generally will recognize capital gain or loss equal to the difference between the amount of cash and the fair market value of any property received upon the sale, exchange or other taxable disposition and such U.S. holder's adjusted tax basis in our securities. This capital gain or loss will be long-term capital gain or loss if the U.S. holder's holding period in such securities is more than one year at the time of the sale, exchange or other taxable disposition. Long-term capital gains recognized by certain non-corporate U.S. holders, including individuals, generally will be subject to reduced rates of U.S. federal income tax. The deductibility of capital losses is subject to certain limitations.

A U.S. holder may be subject to information reporting and backup withholding when such holder receives payments on our securities (including constructive dividends) or receives proceeds from the sale or other taxable disposition of our securities. Certain U.S. holders are exempt from backup withholding, including C corporations and certain tax-exempt organizations. A U.S. holder will be subject to backup withholding if such holder is not otherwise exempt and such holder:

Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules may be allowed as a refund or a credit against a U.S. holder’s U.S. federal income tax liability, provided the required information is timely furnished to the IRS. U.S. holders should consult their tax advisors regarding their qualification for an exemption from backup withholding and the procedures for obtaining such an exemption.

For purposes of this discussion, a “non-U.S. holder” is a beneficial owner of our securities that is neither a U.S. holder nor a partnership or an entity or arrangement treated as a partnership for U.S. federal income tax purposes.

If we make distributions on our securities such distributions will constitute dividends to the extent paid from our current or accumulated earnings and profits, as determined under U.S. federal income tax principles. If a distribution exceeds our current and accumulated earnings and profits, the excess will be treated as a tax-free return of the non-U.S. holder’s investment, up to such non-U.S. holder’s adjusted tax basis in our securities. Any remaining excess will be treated as capital gain from the sale or exchange of such securities, subject to the tax treatment described below in “—Gain on Sale, Exchange or Other Taxable Disposition of Our Shares or Pre-Funded Warrants.”

Dividends paid to a non-U.S. holder will generally be subject to withholding of U.S. federal income tax at a 30% rate of the gross amount of the dividend or such lower rate as may be specified by an applicable income tax treaty between the United States and such non-U.S. holder's country of residence for purposes of such treaty.

Dividends that are treated as effectively connected with a trade or business conducted by a non-U.S. holder within the United States and, if an applicable income tax treaty so provides, that are attributable to a permanent establishment or a fixed base maintained by the non-U.S. holder within the United States, are generally exempt from the 30% withholding tax if the non-U.S. holder satisfies applicable certification and disclosure requirements. However, such U.S. effectively connected income, net of specified deductions and credits, is taxed at the same U.S. federal income tax rates applicable to U.S. persons (as defined in the Code). Any U.S. effectively connected income received by a non-U.S. holder that is a corporation may also, under certain circumstances, be subject to an additional “branch profits tax” at a 30% rate or such lower rate as may be specified by an applicable income tax treaty between the United States and such non-U.S. holder's country of residence for purposes of such treaty.

To claim a reduction or exemption from withholding, a non-U.S. holder generally will be required to provide (a) a properly executed IRS Form W-8BEN or IRS Form W-8BEN-E (or successor form) and satisfy applicable certification and other requirements to claim the benefit of an applicable income tax treaty between the United States and such non-U.S. holder's country of residence, or (b) a properly executed IRS Form W-8ECI stating that dividends are not subject to withholding because they are effectively connected with such non-U.S. holder's conduct of a trade or business within the United States. Non-U.S. holders are urged to consult their tax advisors regarding their entitlement to benefits under a relevant income tax treaty.

A non-U.S. holder that is eligible for a reduced rate of U.S. withholding tax under an income tax treaty may obtain a refund or credit of any excess amounts withheld by timely filing an appropriate claim for refund with the IRS.

Distributions will also be subject to the discussion below under the headings “—Backup Withholding and Information Reporting” and “—Foreign Accounts.”

Gain on Sale, Exchange or Other Taxable Disposition of Our Shares or Pre-Funded Warrants

Subject to the discussion below under the headings “—Backup Withholding and Information Reporting” and “—Foreign Accounts,” in general, a non-U.S. holder will not be subject to any U.S. federal income tax on any gain realized upon such non-U.S. holder's sale, exchange or other taxable disposition of our securities unless:

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the gain is effectively connected with a U.S. trade or business of the non-U.S. holder and, if an applicable income tax treaty so provides, is attributable to a permanent establishment or a fixed base maintained in the United States by such non-U.S. holder, in which case the non-U.S. holder generally will be taxed at the U.S. federal income tax rates applicable to U.S. persons (as defined in the Code) and, if the non-U.S. holder is a foreign corporation, the branch profits tax described above in “—Distributions on the Shares and Pre-Funded Warrants” also may apply;

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the non-U.S. holder is a nonresident alien individual who is present in the United States for 183 days or more in the taxable year of the disposition and certain other conditions are met, in which case the non-U.S. holder will be subject to a 30% U.S. federal income tax (or such lower rate as may be specified by an applicable income tax treaty) on the net gain derived from the disposition, which may be offset by U.S. source capital losses of the non-U.S. holder, if any (even though the individual is not considered a resident of the United States); or

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we are, or have been, at any time during the five-year period preceding such disposition (or the non-U.S. holder's holding period, if shorter) a “U.S. real property holding corporation” in which case such non-U.S. holder generally will be taxed on its net gain derived from the disposition as effectively connected income taxable at the U.S. federal income tax rates applicable to U.S. persons (as defined in the Code); however, the branch profits tax described above will not apply to a U.S. holder that is a foreign corporation. Generally, a corporation is a U.S. real property holding corporation if the fair market value of its U.S. real property interests equals or exceeds 50% of the sum of the fair market value of its worldwide real property interests plus its other assets used or held for use in a trade or business. Although there can be no assurance, we do not believe that we are, or have been, a U.S. real property holding corporation, or that we are likely to become one in the future. Even if we are or become a U.S. real property holding corporation, provided that our common stock is regularly traded, as defined by applicable U.S. Treasury Regulations, on an established securities market, our securities will be treated as a U.S. real property interest only with respect to a non-U.S. holder that holds more than 5% of our securities (as determined under U.S. federal income tax principles), directly or indirectly, actually or constructively, during the shorter of the 5-year period ending on the date of the disposition or the period that the non-U.S. holder held our securities. There can be no assurance that our common stock will continue to qualify as regularly traded on an established securities market.

We must report annually to the IRS and to each non-U.S. holder the gross amount of the dividends on our securities paid to such non-U.S. holder and the tax withheld, if any, with respect to such dividends. Non-U.S. holders will have to comply with specific certification procedures to establish that the holder is not a U.S. person (as defined in the Code) in order to avoid backup withholding at the applicable rate with respect to any dividends on our securities. A non-U.S. holder generally will not be subject to U.S. backup withholding with respect to payments of dividends on our securities if it certifies its non-U.S. status by providing a valid IRS Form W-8BEN or IRS Form W-8BEN-E (or successor form) or IRS Form W-8ECI, or otherwise establishes an exemption; provided we do not

have actual knowledge or reason to know such non-U.S. holder is a U.S. person, as defined in the Code. Dividends paid to non-U.S. holders subject to the U.S. withholding tax, as described above in “—Distributions on the Shares and Pre-Funded Warrants” generally will be exempt from U.S. backup withholding.

Information reporting and backup withholding generally will apply to the proceeds of a disposition of our securities by a non-U.S. holder effected by or through the U.S. office of any broker, U.S. or foreign, unless the holder certifies its status as a non-U.S. holder and satisfies certain other requirements, or otherwise establishes an exemption. Generally, information reporting and backup withholding will not apply to a payment of disposition proceeds to a non-U.S. holder where the transaction is effected outside the United States through a non-U.S. office of a broker. However, for information reporting purposes, dispositions effected through a non-U.S. office of a broker with substantial U.S. ownership or operations generally will be treated in a manner similar to dispositions effected through a U.S. office of a broker. Non-U.S. holders should consult their tax advisors regarding the application of the information reporting and backup withholding rules to them.

Copies of information returns may be made available to the tax authorities of the country in which the non-U.S. holder resides or is established under the provisions of a specific treaty or agreement.

Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules from a payment to a non-U.S. holder may be allowed as a credit against the non-U.S. holder's U.S. federal income tax liability, if any, and may entitle such holder to a refund, provided that the required information is timely furnished to the IRS.

The Code generally imposes a U.S. federal withholding tax of 30% on dividends and, subject to the discussion below regarding proposed regulations issued by the U.S. Treasury Department, the gross proceeds of a disposition of our securities paid to a “foreign financial institution” (as defined in the Code), unless such institution enters into an agreement with the U.S. government to, among other things, withhold on certain payments and to collect and provide to the U.S. tax authorities substantial information regarding accounts held by certain “specific United States persons” or “United States owned foreign entities” (each as defined in the Code), or otherwise qualifies for an exemption from these rules. A U.S. federal withholding tax of 30% also applies to dividends and, subject to the discussion below regarding proposed regulations issued by the U.S. Treasury Department, will apply to the gross proceeds of a disposition of our securities paid to a “non-financial foreign entity” (as defined in the Code), unless such entity provides the withholding agent with either a certification that it does not have any “substantial United States owners” (as defined in the Code), provides information regarding each substantial United States owners of the entity, or otherwise qualifies for an exemption from these rules. Under certain circumstances, a non-U.S. holder might be eligible for refunds or credits of such taxes. An intergovernmental agreement between the United States and an applicable foreign country may modify the requirements described in this paragraph.

The withholding provisions described above currently apply to dividends paid on our securities. The U.S. Treasury Department released proposed regulations which, if finalized in their present form, would eliminate the U.S. federal withholding tax of 30% applicable to the gross proceeds of a sale or other disposition of our securities. In its preamble to such proposed regulations, the U.S. Treasury Department stated that taxpayers may generally rely on the proposed regulations until final regulations are issued.

EACH PROSPECTIVE INVESTOR SHOULD CONSULT ITS TAX ADVISOR REGARDING THE PARTICULAR U.S. FEDERAL, STATE AND LOCAL AND NON-U.S. TAX CONSEQUENCES OF PURCHASING, HOLDING AND DISPOSING OF OUR SECURITIES, INCLUDING THE CONSEQUENCES OF ANY PROPOSED CHANGE IN APPLICABLE LAWS.

The underwriters will purchase the pre-funded warrants pursuant to the underwriting agreement described in the Preliminary Prospectus Supplement on terms generally consistent with those applicable to the shares of common stock being sold in the offering. The per share underwriting discounts and commissions for the pre-funded warrants will be equal to the per share underwriting discounts and commissions on the shares of our common stock sold in the offering.

Additional conforming changes are hereby made to the Preliminary Prospectus Supplement to reflect the changes described in this free writing prospectus. All terms of the Preliminary Prospectus Supplement applicable to our shares of common stock will be applicable to the shares of common stock underlying the pre-funded warrants upon issuance.

Geron Corporation has filed an automatically effective registration statement (including a preliminary prospectus supplement, dated January 4, 2023 and the accompanying prospectus) with the SEC for the offering to which this communication relates. Before you invest, you should read the preliminary prospectus supplement and the accompanying prospectus and other documents Geron Corporation has filed with the SEC for more complete information about Geron Corporation and the offering. You may get these documents for free by visiting EDGAR on the SEC website at www.sec.gov. Alternatively, copies may be obtained from: Goldman Sachs & Co. LLC, Attention: Prospectus Department, 200 West Street, New York, New York 10282, by telephone at 1-866-471-2526 or by email at prospectus-ny@ny.email.gs.com; and Stifel, Nicolaus & Company, Incorporated, Attention: Syndicate, One Montgomery Street, Suite 3700, San Francisco, California 94104, by telephone at 415-364-2720 or by email at syndprospectus@stifel.com.


	The lock-up restrictions described in the Preliminary Prospectus Supplement under “Underwriting” will not apply to the issuance of shares of common stock upon the exercise of the pre-funded warrants during the 75-day period following the date of the final prospectus supplement to be filed in connection with this offering.
Option to purchase additional shares	We have granted the underwriters an option, exercisable for 30 days from the date of the final prospectus supplement, to purchase additional shares equal to 15% of the number of shares offered hereby from us.
Nasdaq listing for our common stock	Our common stock is listed on The Nasdaq Global Select Market under the symbol “GERN.” There is no established public trading market for the pre-funded warrants and we do not expect a market to develop. In addition, we do not intend to apply for listing of the pre-funded warrants on any securities exchange or recognized trading system. See the section titled “Description of Securities We Are Offering—Pre-Funded Warrants.”


Public offering price per share of common stock (or pre-funded warrant at the public offering price less $0.001)		$
Historical net tangible book value per share as of September 30, 2022	$0.28
Increase in net tangible book value per share attributable to this offering	$
As adjusted net tangible book value per share as of September 30, 2022, after giving effect to this offering		$
Dilution in net tangible book value per share to investors purchasing securities in this offering		$


Issuer	Geron Corporation.
Common stock offered by us	shares
Pre-funded warrants offered by us	We are also offering, in lieu of shares of common stock to certain investors that so choose, pre-funded warrants to purchase shares of common stock. Each pre-funded warrant will have an initial exercise price per share of $0.001, subject to certain adjustments. The purchase price of each pre-funded warrant is equal to the price at which the share of common stock is being sold to the public in this offering, minus $0.001. The pre-funded warrants are exercisable immediately and may be exercised at any time until all of the pre-funded warrants are exercised in full. For more information, see the section titled “Description of Securities We Are Offering—Pre-Funded Warrants.” This free writing prospectus and the Preliminary Prospectus Supplement also relate to the offering of the shares of common stock issuable upon the exercise of such pre-funded warrants.