Nature of the Business and Basis of Presentation	6 Months Ended
Jun. 30, 2020
Accounting Policies [Abstract]
Nature of the Business and Basis of Presentation	1. Nature of the Business and Basis of Presentation Aileron Therapeutics, Inc. (“Aileron” or the “Company”) is focused on transforming the experience of chemotherapy for cancer patients, enabling them to fight cancer without the fear or burden of chemotherapy-induced side effects. The Company is advancing ALRN-6924, its first-in-class dual MDM2/MDMX inhibitor currently in clinical development, to provide a single medicine to protect multiple healthy cell types throughout the body from chemotherapy while ensuring chemotherapy continues to destroy cancer cells. In addition to potentially reducing or eliminating multiple side effects, ALRN-6924 may also improve patients’ quality of life and help them better tolerate chemotherapy, potentially allowing patients to complete their treatment without dose reductions or delays. The Company’s long-term vision is to provide chemoprotection for patients with p53-mutated cancers, which represents approximately 50% of cancer patients, regardless of cancer type or chemotherapeutic drug. The Company is subject to risks common to companies in the biotechnology industry, including but not limited to, new technological innovations, protection of proprietary technology, dependence on key personnel, compliance with government regulations, uncertainties in the clinical development of product candidates and the need to obtain additional financing. ALRN-6924 will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure and extensive compliance-reporting capabilities. ALRN-6924, the Company’s product candidate, is in clinical development. There can be no assurance that the Company’s development of ALRN-6924 will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained, that ALRN-6924 will obtain necessary governmental regulatory approval or, if approved, will be commercially viable. Even if the Company’s drug development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from other pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its key employees and consultants. The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Liquidity In accordance with Accounting Standards Update (“ASU”) No. 2014-15, Disclosures of Uncertainties about an Entity’s Ability to Continue as a Going Concern (Subtopic 205-40), management must evaluate whether there are conditions or events, considered in the aggregate, that raise substantial doubt about the company’s ability to continue as a going concern within one year after the date that the financial statements are issued. This evaluation initially does not take into consideration the potential mitigating effect of management’s plans that have not been fully implemented as of the date the financial statements are issued. When substantial doubt exists under this methodology, management evaluates whether the mitigating effect of its plans sufficiently alleviates substantial doubt about the company’s ability to continue as a going concern. The mitigating effect of management’s plans, however, is only considered if both (1) it is probable that the plans will be effectively implemented within one year after the date that the financial statements are issued, and (2) it is probable that the plans, when implemented, will mitigate the relevant conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern within one year after the date that the financial statements are issued. Generally, to be considered probable of being effectively implemented, the plans must have been approved before the date that the financial statements are issued. In June 2020, the Company issued and sold in an underwritten public offering an aggregate of 10,162,059 shares of common stock, including an additional 1,071,149 shares of common stock upon the partial exercise of an option of the underwriters to purchase additional shares, for a purchase price to the public of $1.10 per share. The Company received aggregate gross proceeds from the public offering of approximately $11,178 before deducting underwriting discounts and commissions and offering expenses of $932. In July 2019, the Company entered into a Capital on Demand^SM Sales Agreement (the “Sales Agreement”) with JonesTrading Institutional Services LLC (“JonesTrading”), under which the Company may issue and sell shares of common stock, from time to time, having an aggregate offering price of up to $13,265. Sales of common stock through JonesTrading may be made by any method that is deemed an “at the market” offering as defined in Rule 415(a)(4) under the Securities Act of 1933, as amended. The Company is not obligated to make any sales of its common stock under the Sales Agreement. The Company began selling shares of common stock under the Sales Agreement in April 2020. During the six months ended June 30, 2020, the Company issued and sold an aggregate of 1,263,059 shares of common stock for gross proceeds of $762, before deducting commissions and fees of $24. In June 2020, the Company terminated the offering and sale of shares of common stock under the Sales Agreement with JonesTrading. On April 2, 2019, the Company issued and sold in a private placement an aggregate of (i) 11,838,582 units, consisting of 11,838,582 shares of its common stock and associated warrants (the “common warrants”) to purchase an aggregate of 11,838,582 shares of common stock, for a combined price of $2.01 per unit and (ii) 1,096,741 units, consisting of (a) pre-funded warrants to purchase 1,096,741 shares of the Company’s common stock and (b) associated common warrants to purchase 1,096,741 shares of common stock, for a combined price of $2.01 per unit. The pre-funded warrants had an exercise price of $0.01 per share and had no expiration. The common warrants are exercisable at an exercise price of $2.00 per share and expire five years from the date of issuance. The securities were sold pursuant to a securities purchase agreement entered into with accredited investors on March 28, 2019. The Company received aggregate gross proceeds from the private placement of approximately $26,000, before deducting placement agent fees and offering expenses of $2,175 and excluding the exercise of any warrants. In July 2019, all outstanding pre-funded warrants were exercised for 1,096,741 shares of common stock. The Company’s interim financial statements have been prepared on a going concern basis, which contemplates the continuity of operations, realization of assets and the satisfaction of liabilities in the ordinary course of business. Through June 30, 2020, the Company has funded its operations primarily through sales of common stock in its initial public offering and a follow-on public offering, sales of common stock and warrants in a private placement, sales of preferred stock prior to the Company’s initial public offering and payments received under a collaboration agreement. As of June 30, 2020, the Company had cash, cash equivalents and investments of $18,880. The Company has incurred losses and negative cash flows from operations and had an accumulated deficit of $209,273 as of June 30, 2020. The Company expects to continue to generate losses for the foreseeable future. As of August 5, 2020, the date of issuance of these unaudited interim condensed financial statements, the Company expects that its cash, cash equivalents and investments as of June 30, 2020, will be sufficient to fund its current business plan including related operating expenses and capital expenditure requirements into the fourth quarter of 2021. However, after considering various risks and uncertainties as prescribed by ASU No. 2014-15 (subtopic 205-40), “ASU No. 2014-15,” there is substantial doubt about the Company’s ability to continue as a going concern as of the date of issuance of these interim financial statements without additional capital. The Company plans to address this condition by raising additional capital to finance its operations. The future viability of the Company is dependent on its ability to raise additional capital to finance its operations. Although the Company has been successful in raising capital in the past, there is no assurance that it will be successful in obtaining such additional financing on terms acceptable to the Company, if at all. Therefore, it is not considered probable, as defined in ASU No. 2014-15, that the Company’s plans to raise additional capital will alleviate the substantial doubt regarding its ability to continue as a going concern. On July 12, 2019, the Company received a deficiency letter from the Listing Qualifications Department of the Nasdaq Stock Market notifying the Company that, for the last 30 consecutive business days, the bid price for the Company’s common stock had closed below the minimum $1.00 per share requirement for continued inclusion on the Nasdaq Global Market (the “Bid Price Rule”). On December 20, 2019, the Company applied to transfer the listing of its stock from the Nasdaq Global Market to the Nasdaq Capital Market. On December 27, 2019, Nasdaq approved the Company’s transfer application. This transfer became effective at the opening of business on December 30, 2019. On June 11, 2020, after the Company’s common stock had a closing price bid of at least $1.00 for 10 consecutive trading days, Nasdaq provided written notification to the Company that it had regained compliance with the Bid Price Rule and that Nasdaq considered the matter closed. To execute its business plans, the Company will need substantial funding to support its continuing operations and pursue its growth strategy. Until such time as the Company can generate significant revenue from product sales, if ever, the Company expects to finance its operations through the sale of common stock in public offerings and/or private placements, debt financings or other capital sources, including collaborations with other companies or other strategic transactions. The Company may not be able to obtain financing when needed, on acceptable terms or at all. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate some or all of its clinical programs, product portfolio expansion plans or commercialization efforts, which could adversely affect its business prospects.

Nature of the Business and Basis of Presentation

6 Months Ended

Jun. 30, 2020

Nature of the Business and Basis of Presentation

1. Nature of the Business and Basis of Presentation

Aileron Therapeutics, Inc. (“Aileron” or the “Company”) is focused on transforming the experience of chemotherapy for cancer patients, enabling them to fight cancer without the fear or burden of chemotherapy-induced side effects. The Company is advancing ALRN-6924, its first-in-class dual MDM2/MDMX inhibitor currently in clinical development, to provide a single medicine to protect multiple healthy cell types throughout the body from chemotherapy while ensuring chemotherapy continues to destroy cancer cells.

In addition to potentially reducing or eliminating multiple side effects, ALRN-6924 may also improve patients’ quality of life and help them better tolerate chemotherapy, potentially allowing patients to complete their treatment without dose reductions or delays. The Company’s long-term vision is to provide chemoprotection for patients with p53-mutated cancers, which represents approximately 50% of cancer patients, regardless of cancer type or chemotherapeutic drug.

The Company is subject to risks common to companies in the biotechnology industry, including but not limited to, new technological innovations, protection of proprietary technology, dependence on key personnel, compliance with government regulations, uncertainties in the clinical development of product candidates and the need to obtain additional financing. ALRN-6924 will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure and extensive compliance-reporting capabilities.

ALRN-6924, the Company’s product candidate, is in clinical development. There can be no assurance that the Company’s development of ALRN-6924 will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained, that ALRN-6924 will obtain necessary governmental regulatory approval or, if approved, will be commercially viable. Even if the Company’s drug development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from other pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its key employees and consultants.

The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”).

Liquidity

In accordance with Accounting Standards Update (“ASU”) No. 2014-15, Disclosures of Uncertainties about an Entity’s Ability to Continue as a Going Concern (Subtopic 205-40), management must evaluate whether there are conditions or events, considered in the aggregate, that raise substantial doubt about the company’s ability to continue as a going concern within one year after the date that the financial statements are issued. This evaluation initially does not take into consideration the potential mitigating effect of management’s plans that have not been fully implemented as of the date the financial statements are issued. When substantial doubt exists under this methodology, management evaluates whether the mitigating effect of its plans sufficiently alleviates substantial doubt about the company’s ability to continue as a going concern. The mitigating effect of management’s plans, however, is only considered if both (1) it is probable that the plans will be effectively implemented within one year after the date that the financial statements are issued, and (2) it is probable that the plans, when implemented, will mitigate the relevant conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern within one year after the date that the financial statements are issued. Generally, to be considered probable of being effectively implemented, the plans must have been approved before the date that the financial statements are issued.

In June 2020, the Company issued and sold in an underwritten public offering an aggregate of 10,162,059 shares of common stock, including an additional 1,071,149 shares of common stock upon the partial exercise of an option of the underwriters to purchase additional shares, for a purchase price to the public of $1.10 per share. The Company received aggregate gross proceeds from the public offering of approximately $11,178 before deducting underwriting discounts and commissions and offering expenses of $932.

In July 2019, the Company entered into a Capital on Demand^SM Sales Agreement (the “Sales Agreement”) with JonesTrading Institutional Services LLC (“JonesTrading”), under which the Company may issue and sell shares of common stock, from time to time, having an aggregate offering price of up to $13,265. Sales of common stock through JonesTrading may be made by any method that is deemed an “at the market” offering as defined in Rule 415(a)(4) under the Securities Act of 1933, as amended. The Company is not obligated to make any sales of its common stock under the Sales Agreement. The Company began selling shares of common stock under the Sales Agreement in April 2020. During the six months ended June 30, 2020, the Company issued and sold an aggregate of 1,263,059 shares of common stock for gross proceeds of $762, before deducting commissions and fees of $24. In June 2020, the Company terminated the offering and sale of shares of common stock under the Sales Agreement with JonesTrading.

On April 2, 2019, the Company issued and sold in a private placement an aggregate of (i) 11,838,582 units, consisting of 11,838,582 shares of its common stock and associated warrants (the “common warrants”) to purchase an aggregate of 11,838,582 shares of common stock, for a combined price of $2.01 per unit and (ii) 1,096,741 units, consisting of (a) pre-funded warrants to purchase 1,096,741 shares of the Company’s common stock and (b) associated common warrants to purchase 1,096,741 shares of common stock, for a combined price of $2.01 per unit. The pre-funded warrants had an exercise price of $0.01 per share and had no expiration. The common warrants are exercisable at an exercise price of $2.00 per share and expire five years from the date of issuance. The securities were sold pursuant to a securities purchase agreement entered into with accredited investors on March 28, 2019. The Company received aggregate gross proceeds from the private placement of approximately $26,000, before deducting placement agent fees and offering expenses of $2,175 and excluding the exercise of any warrants. In July 2019, all outstanding pre-funded warrants were exercised for 1,096,741 shares of common stock.

The Company’s interim financial statements have been prepared on a going concern basis, which contemplates the continuity of operations, realization of assets and the satisfaction of liabilities in the ordinary course of business. Through June 30, 2020, the Company has funded its operations primarily through sales of common stock in its initial public offering and a follow-on public offering, sales of common stock and warrants in a private placement, sales of preferred stock prior to the Company’s initial public offering and payments received under a collaboration agreement. As of June 30, 2020, the Company had cash, cash equivalents and investments of $18,880. The Company has incurred losses and negative cash flows from operations and had an accumulated deficit of $209,273 as of June 30, 2020. The Company expects to continue to generate losses for the foreseeable future.

As of August 5, 2020, the date of issuance of these unaudited interim condensed financial statements, the Company expects that its cash, cash equivalents and investments as of June 30, 2020, will be sufficient to fund its current business plan including related operating expenses and capital expenditure requirements into the fourth quarter of 2021. However, after considering various risks and uncertainties as prescribed by ASU No. 2014-15 (subtopic 205-40), “ASU No. 2014-15,” there is substantial doubt about the Company’s ability to continue as a going concern as of the date of issuance of these interim financial statements without additional capital. The Company plans to address this condition by raising additional capital to finance its operations. The future viability of the Company is dependent on its ability to raise additional capital to finance its operations. Although the Company has been successful in raising capital in the past, there is no assurance that it will be successful in obtaining such additional financing on terms acceptable to the Company, if at all. Therefore, it is not considered probable, as defined in ASU No. 2014-15, that the Company’s plans to raise additional capital will alleviate the substantial doubt regarding its ability to continue as a going concern.

On July 12, 2019, the Company received a deficiency letter from the Listing Qualifications Department of the Nasdaq Stock Market notifying the Company that, for the last 30 consecutive business days, the bid price for the Company’s common stock had closed below the minimum $1.00 per share requirement for continued inclusion on the Nasdaq Global Market (the “Bid Price Rule”). On December 20, 2019, the Company applied to transfer the listing of its stock from the Nasdaq Global Market to the Nasdaq Capital Market.

On December 27, 2019, Nasdaq approved the Company’s transfer application. This transfer became effective at the opening of business on December 30, 2019. On June 11, 2020, after the Company’s common stock had a closing price bid of at least $1.00 for 10 consecutive trading days, Nasdaq provided written notification to the Company that it had regained compliance with the Bid Price Rule and that Nasdaq considered the matter closed.

To execute its business plans, the Company will need substantial funding to support its continuing operations and pursue its growth strategy. Until such time as the Company can generate significant revenue from product sales, if ever, the Company expects to finance its operations through the sale of common stock in public offerings and/or private placements, debt financings or other capital sources, including collaborations with other companies or other strategic transactions. The Company may not be able to obtain financing when needed, on acceptable terms or at all. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate some or all of its clinical programs, product portfolio expansion plans or commercialization efforts, which could adversely affect its business prospects.