Infinity Pharmaceuticals (INFIQ) 10-Q 13 May 21 2021 Q1 Quarterly report Financial data

Cover

Cover - shares	3 Months Ended
	Mar. 31, 2021	May 06, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
Document Transition Report	false
Entity File Number	000-31141
Entity Registrant Name	INFINITY PHARMACEUTICALS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	33-0655706
Entity Address, Address Line One	1100 Massachusetts Avenue
Entity Address, Address Line Two	Floor 4
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02138
City Area Code	617
Local Phone Number	453-1000
Title of 12(b) Security	Common Stock, $0.001 par value
Trading Symbol	INFI
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		88,647,241
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001113148
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 106,756	$ 28,593
Available-for-sale securities	0	5,515
Prepaid expenses and other current assets	2,549	1,912
Total current assets	109,305	36,020
Property and equipment, net	1,591	1,710
Restricted cash, less current portion	165	165
Operating lease right-of-use assets	1,336	1,419
Other assets	1	5
Total assets	112,398	39,319
Current liabilities:
Accounts payable	1,205	2,982
Accrued expenses and other current liabilities	8,253	8,065
Total current liabilities	9,458	11,047
Liabilities related to sale of future royalties, net, less current portion (note 9)	49,331	28,021
Liability related to sale of future royalties to a related party, net (note 9)	0	21,559
Operating lease liability, less current portion	1,313	1,436
Other liabilities	250	245
Total liabilities	60,352	62,308
Commitments and contingencies
Stockholders’ equity (deficit):
Preferred Stock, $0.001 par value; 1,000,000 shares authorized, no shares issued and outstanding at March 31, 2021 and December 31, 2020	0	0
Common Stock, $0.001 par value; 200,000,000 shares authorized; 88,647,241 and 64,320,244 shares issued and outstanding at March 31, 2021 and December 31, 2020, respectively	89	64
Additional paid-in capital	829,907	743,269
Accumulated deficit	(777,950)	(766,321)
Accumulated other comprehensive income	0	(1)
Total stockholders’ equity (deficit)	52,046	(22,989)
Total liabilities and stockholders’ equity	$ 112,398	$ 39,319

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	88,647,241	64,320,244
Common stock, shares outstanding (in shares)	88,647,241	64,320,244

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenues:
Revenue, Product and Service	us-gaap:RoyaltyMember	us-gaap:RoyaltyMember
Total revenues	$ 467	$ 428
Operating expenses:
Research and development	8,201	7,346
General and administrative	3,566	3,324
Royalty expense (note 11)	282	258
Total operating expenses	12,049	10,928
Loss from operations	(11,582)	(10,500)
Other income (expense):
Investment and other income (expense)	(2)	186
Non-cash interest expense (note 9)	(45)	(38)
Non-cash related party interest expense (note 9)	0	(534)
Total other expense	(47)	(386)
Net loss	$ (11,629)	$ (10,886)
Basic and diluted loss per common share (in dollars per share)	$ (0.15)	$ (0.19)
Basic and diluted weighted average number of common shares outstanding (in shares)	75,728,176	57,343,608
Other comprehensive loss:
Net unrealized holding gains on available-for-sale securities arising during the period	$ 1	$ 104
Comprehensive loss	$ (11,628)	$ (10,782)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating activities
Net loss	$ (11,629)	$ (10,886)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	119	120
Stock-based compensation	530	360
Non-cash royalty revenue	(247)	(226)
Non-cash interest expense	45	38
Non-cash related party interest expense	0	534
Other, net	23	(24)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(634)	(341)
Operating lease right-of-use assets	83	56
Accounts payable, accrued expenses and other liabilities	(1,646)	(1,275)
Operating lease liability	(114)	(133)
Net cash used in operating activities	(13,470)	(11,777)
Investing activities
Purchases of property and equipment	0	(18)
Purchases of available-for-sale securities	0	(19,732)
Proceeds from maturities of available-for-sale securities	5,500	20,180
Net cash provided by investing activities	5,500	430
Financing activities
Proceeds from public offering, net	85,838	0
Proceeds from sale of future royalties to a related party, net	0	19,572
Proceeds from issuances of common stock, net	295	0
Net cash provided by financing activities	86,133	19,572
Net increase in cash, cash equivalents and restricted cash	78,163	8,225
Cash, cash equivalents and restricted cash at beginning of period	28,908	22,575
Cash, cash equivalents and restricted cash at end of period	107,071	30,800
Reconciliation of cash, cash equivalents, and restricted cash to the condensed consolidated balance sheets
Total cash, cash equivalents and restricted cash	107,071	30,800
Supplemental schedule of noncash activities
Deferred offering costs included in accounts payable	276	0
Issuance of common stock for compensation	$ 0	$ 444

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity (Deficit) (unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income
Beginning Balance (in shares) at Dec. 31, 2019		57,077,550
Beginning Balance at Dec. 31, 2019	$ 7,726	$ 57	$ 733,486	$ (725,829)	$ 12
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	360		360
Unrealized gain on marketable securities	104				104
Net loss	(10,886)			(10,886)
Issuance of common stock, net (in shares)		356,048
Issuance of common stock, net	444		444
Ending Balance (in shares) at Mar. 31, 2020		57,433,598
Ending Balance at Mar. 31, 2020	(2,252)	$ 57	734,290	(736,715)	116
Beginning Balance (in shares) at Dec. 31, 2020		64,320,244
Beginning Balance at Dec. 31, 2020	(22,989)	$ 64	743,269	(766,321)	(1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		176,997
Exercise of stock options	295	$ 1	294
Stock-based compensation expense	530		530
Issuance of common stock related to public offering, net of issuance costs (in shares)		24,150,000
Issuance of common stock related to public offering, net of issuance costs	85,838	$ 24	85,814
Unrealized gain on marketable securities	1				1
Net loss	(11,629)			(11,629)
Ending Balance (in shares) at Mar. 31, 2021		88,647,241
Ending Balance at Mar. 31, 2021	$ 52,046	$ 89	$ 829,907	$ (777,950)	$ 0

Organization

Organization	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	1. Organization Infinity Pharmaceuticals, Inc., is a clinical-stage innovative biopharmaceutical company dedicated to developing novel medicines for people with cancer. As used throughout these unaudited, condensed consolidated financial statements, the terms “Infinity,” “we,” “us,” and “our” refer to the business of Infinity Pharmaceuticals, Inc., and its wholly-owned subsidiaries.

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	2. Basis of Presentation These condensed consolidated financial statements include the accounts of Infinity and its wholly-owned subsidiaries. We have eliminated all significant intercompany accounts and transactions in consolidation. The accompanying condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments, consisting of normal recurring accruals and revisions of estimates, considered necessary for a fair presentation of the accompanying condensed consolidated financial statements have been included. Interim results for the three months ended March 31, 2021 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2021. The information presented in the condensed consolidated financial statements and related footnotes at March 31, 2021, and for the three months ended March 31, 2021 and 2020, is unaudited, and the condensed consolidated balance sheet amounts and related footnotes at December 31, 2020 have been derived from our audited financial statements. For further information, please refer to the consolidated financial statements and accompanying footnotes included in our Annual Report on Form 10-K for the fiscal year ended December 31, 2020 filed with the U.S. Securities and Exchange Commission, or SEC, on March 16, 2021, which we refer to as our 2020 Annual Report on Form 10-K. Liquidity As of March 31, 2021, we had cash and cash equivalents of $106.8 million. We have primarily incurred operating losses since inception and have relied on our ability to fund our operations through collaboration and license arrangements or other strategic arrangements, as well as through the sale of stock. We expect to continue to spend significant resources to fund the development and potential commercialization of eganelisib, also known as IPI-549, an orally administered, clinical-stage, immuno-oncology product candidate that reprograms macrophages through selective inhibition of the enzyme phosphoinositide-3-kinase-gamma, or PI3K-gamma, and to incur significant operating losses for the foreseeable future. We believe that our existing cash, cash equivalents and available-for-sale securities at March 31, 2021 will be adequate to satisfy our forecasted operating needs for at least the next twelve months from the issuance date of these financial statements.

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Significant Accounting Policies	3. Significant Accounting Policies Our significant accounting policies are described in Note 2, “Summary of Significant Accounting Policies,” in our 2020 Annual Report on Form 10-K. Segment Information We operate in one business segment, which focuses on drug development. We make operating decisions based upon the performance of the enterprise as a whole and utilize our consolidated financial statements for decision making. Basic and Diluted Net Loss per Common Share Basic net loss per share is based upon the weighted average number of common shares outstanding during the period. Diluted net loss per share is based upon the weighted average number of common shares outstanding during the period plus the effect of additional weighted average common equivalent shares outstanding during the period when the effect of adding such shares is dilutive. Common equivalent shares result from the assumed exercise of outstanding stock options and the exercise of outstanding warrants (the proceeds of which are then assumed to have been used to repurchase outstanding stock using the treasury stock method). In addition, the assumed proceeds under the treasury stock method include the average unrecognized compensation expense of stock options that are in-the-money. This results in the “assumed” buyback of additional shares, thereby reducing the dilutive impact of stock options. The two-class method is used for outstanding warrants as such warrants are considered to be participating securities, and this method is more dilutive than the treasury stock method. The following outstanding shares of common stock equivalents were excluded from the computation of net loss per share attributable to common stockholders for the periods presented because including them would have been antidilutive: At March 31, 2021 2020 Stock options 12,404,270 11,175,463 Warrants (excluded from treasury stock method) — 1,000,000 New Accounting Pronouncements In June 2016, the Financial Accounting Standards Board, or FASB, issued Accounting Standard Update, or ASU, No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Statements, or ASU No. 2016-13, which requires that credit losses be reported using an expected losses model rather than the incurred losses model that is currently used, and it establishes additional disclosure requirements related to credit risks. For available-for-sale debt securities with expected credit losses, this standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. In November 2019, the FASB subsequently issued ASU 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates, whereby the effective date of this standard for smaller reporting companies was deferred to annual reporting periods beginning after December 15, 2022, including interim periods within those annual reporting periods, and early adoption is still permitted. We are currently evaluating the impact of ASU No. 2016-13 on our consolidated financial statements and related disclosures. In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity, or ASU No. 2020-06, which simplifies the guidance on an issuer’s accounting for convertible instruments and contracts in its own equity. The provisions of ASU No. 2020-06 are applicable for fiscal years beginning after December 15, 2023, with early adoption permitted no earlier than fiscal years beginning after December 15, 2020. We are currently evaluating the impact of ASU No. 2020-06 on our consolidated financial statements.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	4. Stock-Based Compensation Total stock-based compensation expense related to all equity awards for the three months ended March 31, 2021 and 2020 was composed of the following: Three Months Ended March 31, 2021 2020 (in thousands) Research and development $ 151 $ 80 General and administrative 379 280 Total stock-based compensation expense $ 530 $ 360 As of March 31, 2021, we had approximately $5.0 million of total unrecognized compensation cost related to unvested common stock options and awards under our Employee Stock Purchase Plan, which is expected to be recognized over a weighted-average period of 3.1 years. Stock Options During the three months ended March 31, 2021, we granted options to purchase 60,040 shares of our common stock at a weighted average fair value of $2.90 per share and a weighted average exercise price of $3.64 per share. During the three months ended March 31, 2020, we granted options to purchase 2,524,786 shares of our common stock at a weighted average fair value of $0.96 per share and a weighted average exercise price of $1.23 per share. For the three months ended March 31, 2021 and 2020, the fair values were estimated using the Black-Scholes valuation model using the following weighted-average assumptions: Three Months Ended March 31, 2021 2020 Risk-free interest rate 1.1 % 1.6 % Expected annual dividend yield — — Expected stock price volatility 101.9 % 97.3 % Expected term of options 6.1 years 6.0 years

Cash, Cash Equivalents and Avai

Cash, Cash Equivalents and Available-for-Sale Securities	3 Months Ended
	Mar. 31, 2021
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents and Available-for-Sale Securities	5. Cash, Cash Equivalents and Available-for-Sale Securities The following is a summary of cash, cash equivalents and available-for-sale securities: March 31, 2021 Cost Gross Gross Estimated (in thousands) Cash and cash equivalents $ 106,756 $ — $ — $ 106,756 Total cash, cash equivalents and available-for-sale securities $ 106,756 $ — $ — $ 106,756 December 31, 2020 Cost Gross Gross Estimated (in thousands) Cash and cash equivalents $ 28,593 $ — $ — $ 28,593 Available-for-sale securities: U.S. Treasury securities due in one year or less 5,516 — (1) 5,515 Total available-for-sale securities 5,516 — (1) 5,515 Total cash, cash equivalents and available-for-sale securities $ 34,109 $ — $ (1) $ 34,108 We evaluated our securities for other-than-temporary impairments based on quantitative and qualitative factors. We did not hold any debt securities at March 31, 2021 that were in an unrealized loss position. As of March 31, 2021, we held no securities in foreign financial institutions. We had no material realized gains or losses on our available-for-sale securities for the three months ended March 31, 2021 and 2020. There were no other-than-temporary impairments recognized for the three months ended March 31, 2021 and 2020.

Fair Value

Fair Value	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value	6. Fair Value The following table presents the assets and liabilities carried at fair value measured on a recurring basis as of March 31, 2021 and December 31, 2020: March 31, 2021 Level 1 Level 2 Level 3 (in thousands) Assets: Cash and cash equivalents $ 106,756 $ — $ — Total assets $ 106,756 $ — $ — Liabilities: Warrant liability $ — $ — $ 205 Total liabilities $ — $ — $ 205 December 31, 2020 Level 1 Level 2 Level 3 (in thousands) Assets: Cash and cash equivalents $ 28,593 $ — $ — U.S. Treasury securities — 5,515 — Total assets $ 28,593 $ 5,515 $ — Liabilities: Warrant liability $ — $ — $ 198 Total liabilities $ — $ — $ 198 The fair value of the available-for-sale securities and cash and cash equivalents is based on the following inputs for both U.S. Treasury securities and U.S. government-sponsored enterprise obligations: benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers and reference data including TRACE ® reported trades. There have been no changes to our valuation methods of available-for-sale securities during the three months ended March 31, 2021. We had no available-for-sale securities that were classified as Level 3 at any point during the three months ended March 31, 2021 or during the year ended December 31, 2020. Warrant liability relates to potential future warrants that may be issued. The fair value of the warrant liability on the date of the commitment and on each re-measurement date for those warrants classified as liabilities was estimated using the Monte Carlo simulation model, which involves a series of simulated future stock price paths over the remaining life of the commitment. The fair value is estimated by taking the average of the fair values under each of many Monte Carlo simulations. The fair value estimate is affected by our stock price, as well as estimated future financing needs, including timing and sources of the financing and subjective variables including expected stock price volatility over the remaining life of the commitment and risk-free interest rate. Due to the nature of these inputs, the valuation of the warrants is considered a Level 3 measurement. The fair value of the warrant liability as of March 31, 2021and December 31, 2020 has been included in other liabilities on our condensed consolidated balance sheet. See Note 9 for further discussions of the accounting for the warrants. The carrying amounts reflected in the condensed consolidated balance sheets for prepaid expenses and other current assets, other assets, accounts payable and accrued expenses approximate their fair value due to their short-term maturities.

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	3 Months Ended
	Mar. 31, 2021
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid Expenses and Other Current Assets	7. Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consisted of the following: March 31, 2021 December 31, 2020 (in thousands) Prepaid expenses $ 2,202 $ 1,528 Restricted cash, current portion 150 150 Other current assets 197 234 Total prepaid expenses and other current assets $ 2,549 $ 1,912

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	3 Months Ended
	Mar. 31, 2021
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	8. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following: March 31, 2021 December 31, 2020 (in thousands) Accrued clinical and development $ 4,667 $ 3,511 Accrued compensation and benefits 1,221 2,385 Liability related to sale of future royalties, net, current portion 895 848 Operating lease liability, current portion 498 489 Other 972 832 Total accrued expenses $ 8,253 $ 8,065

Liabilities Related to Sale of

Liabilities Related to Sale of Future Royalties	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Liabilities Related to Sale of Future Royalties	9. Liabilities Related to Sale of Future Royalties HCR Agreement In 2016, we and Verastem Inc., or Verastem, entered into an amended and restated license agreement, or the Verastem Agreement, under which we granted to Verastem an exclusive worldwide license in oncology indications for the research, development, commercialization, and manufacture of duvelisib, or Copiktra ® , an oral, dual inhibitor of PI3K delta and gamma, and products containing duvelisib, which we refer to as Licensed Products. In September 2020, Verastem completed a disposition of its rights, title, and interest in and to duvelisib to Secura Bio, Inc., or Secura Bio, wherein Secura Bio assumed all liabilities and obligations under the Verastem Agreement. We now refer to the Verastem Agreement as the Secura Bio Agreement. Secura Bio is obligated to pay us royalties on worldwide net sales of Licensed Products ranging from the mid-single digits to the high-single digits, a portion of which we are obligated to share with Takeda Pharmaceuticals Company Limited, or Takeda, as described in Note 11. In March 2019, we entered into a royalty purchase agreement, or the HCR Agreement, with HealthCare Royalty Partners III, L.P., or HCR, providing for the acquisition by HCR of our interest in certain royalty payments based on worldwide annual net sales of Licensed Products under the Secura Bio Agreement for gross proceeds of $30.0 million, which is non-refundable. Under the HCR Agreement, HCR obtained the right to receive the royalty payments up to an agreed upon thresholds of royalties, the amount of which depends on when the aggregate royalties received by HCR reach specified thresholds. If the specified threshold has been met through royalty payments from Secura Bio or if we elect to make a payment to meet the threshold amount, the HCR Agreement will automatically terminate and all rights to the royalty stream under the HCR Agreement will revert back to us. If the specified threshold has not been achieved by June 30, 2025, the HCR Agreement will continue through the term of the Secura Bio Agreement. We recognized the receipt of the $30.0 million payment from HCR, net of debt discount and issuance costs of approximately $2.4 million, as a liability. As the basis for our determination, we considered, in accordance with the relevant accounting guidance, the potential for the royalty stream to revert back to us if specified royalty thresholds has been met and our right to terminate the HCR Agreement by making a payment to achieve the threshold. We are not obligated to repay the proceeds received under the HCR Agreement. In order to determine the amortization of the liability, we are required to estimate the total amount of future net royalty payments to be made to HCR over the term of the HCR Agreement. The total threshold of net royalties to be paid, less the net proceeds received, will be recorded as interest expense over the life of the liability. We impute interest on the unamortized portion of the liability using the effective interest method. Interest and debt discount amortization expense is reflected as non-cash interest expense in the condensed consolidated statements of operations. Over the course of the HCR Agreement, the actual interest rate will be affected by the amount and timing of royalty revenue recognized and changes in forecasted royalty revenue. On a quarterly basis, we reassess the effective interest rate and adjust the rate prospectively as needed. The following table shows the activity within the liability account for the three months ended March 31, 2021: March 31, 2021 (in thousands) Liability related to sale of future royalties, net - beginning balance $ 28,869 Non-cash royalty revenue (247) Non-cash interest expense recognized 38 Liability related to sale of future royalties, net - ending balance 28,660 Less: current portion (895) Liability related to sale of future royalties, net, less current portion $ 27,765 As royalties are due to HCR by Secura Bio, the balance of the recognized liability will be effectively repaid over the life of the HCR Agreement. There are a number of factors that could materially affect the amount and timing of royalty payments from Secura Bio, none of which are within our control. BVF Agreement On January 8, 2020, or the BVF Closing Date, we entered into a funding agreement, or the BVF Funding Agreement, with BVF Partners, L.P., or BVF, and Royalty Security, LLC, a wholly-owned subsidiary of BVF, or the Buyer. BVF was subsequently replaced as a party to the BVF Funding Agreement with Royalty Security Holdings, LLC. The BVF Funding Agreement provides for the acquisition by the Buyer of our interest in all royalty payments based on worldwide annual net sales of patidegib, part of the hedgehog inhibitor program we licensed to PellePharm Inc., or PellePharm, in 2013, or the BVF Licensed Product, excluding relevant Trailing Mundipharma Royalties, as defined in Note 11, related to patidegib. We refer to all BVF Licensed Product royalties owed to us less Trailing Mundipharma Royalties as the Royalty or Royalties. Such Royalties are owed to us pursuant to the PellePharm Agreement, as defined in Note 11, entered into by and between us and PellePharm. The Buyer and BVF are affiliates of Biotechnology Value Fund, L.P., which beneficially owned approximately 30% of our common stock at the time of the transaction. Effective February 17, 2021, Biotechnology Value Fund, L.P. is no longer considered our related party. Pursuant to the BVF Funding Agreement, we received a non-refundable payment of $20.0 million, or the Upfront Purchase Price, less certain transaction expenses. We transferred to the Buyer (i) the Royalty, (ii) the PellePharm Agreement (subject to our rights to milestone payments and rights to equity in PellePharm under the PellePharm Agreement), and (iii) certain patent rights established in the BVF Funding Agreement, with (i), (ii), and (iii) together referred to as Transferred Assets. We preserved our rights under the PellePharm Agreement to receive potential regulatory, commercial, and success-based milestone payments. We have the option to terminate the BVF Funding Agreement by purchasing 100% of the outstanding equity interests of the Buyer under specified terms for a specified amount under the BVF Funding Agreement through January 8, 2023. In addition, the BVF Funding Agreement may be terminated by mutual written agreement of us and the Buyer. We recognized the proceeds received under the BVF Funding Agreement as a related party liability that will be amortized using the effective interest method over the life of the arrangement. We recorded the receipt of the $20.0 million Upfront Purchase Price as a liability, net of debt issuance costs of approximately $0.4 million and warrant liability of $0.3 million. The liability has been reclassified to liabilities related to sale of future royalties since Biotechnology Value Fund, L.P. is no longer considered our related party. We are not obligated to repay the proceeds received under the BVF Funding Agreement. In order to determine the amortization of the liability, we are required to estimate the total amount of potential future net royalty payments to be made by PellePharm to the Buyer over the term of the BVF Funding Agreement. The total estimated net royalties to be paid, less the net proceeds received, will be recorded as interest expense over the life of the liability. Interest and debt discount amortization expense is reflected as non-cash related party interest expense as of December 31, 2020 and non-cash interest expense as of March 31, 2021 in our condensed consolidated statements of operations. Over the course of the BVF Funding Agreement, the actual interest rate will be affected by the amount and timing of royalty revenue recognized, if any, and changes in forecasted royalty revenue. There are a number of factors that could materially affect the amount and timing of royalty payments from PellePharm, none of which are within our control. On a quarterly basis, we will reassess the effective interest rate and adjust the rate prospectively as needed. The following table shows the activity within the liability account for the three months ended March 31, 2021: March 31, 2021 (in thousands) Liability related to sale of future royalties, net - beginning balance $ 21,559 Non-cash interest expense recognized 7 Liability related to sale of future royalties, net - ending balance $ 21,566 For so long as we have not exercised an option to repurchase the Buyer’s equity interest under the BVF Funding Agreement, (a) if, during the 36-month period following the BVF Closing Date, we issue a specified number of shares of our common stock, which we refer to as the Warrant Threshold, and (b) any shares in excess of the Warrant Threshold are issued for consideration to us of less than $3.75 per share (as adjusted for any stock splits, reverse stock splits or other similar recapitalization events), or the Threshold Price, then we are obligated to issue to BVF warrants to purchase a number of shares of our common stock. Such warrants would equal 50% of the number of qualifying shares at an exercise price equal to 1.5 times the price per share of such qualifying shares issued. The requirement to issue warrants to BVF does not apply to certain issuances of our common stock. As of March 31, 2021, the Warrant Threshold has been met and any future qualifying shares of our common stock issued below the Price Threshold will result in warrants to purchase our common stock to be issued to BVF. No warrants have been issued as of March 31, 2021. We determined that the commitment to issue warrants represents a freestanding financial instrument and accounted for it as a liability as of the BVF Closing Date. The fair value of the warrant liability was estimated using the Monte Carlo simulation model. The fair value of the warrant liability as of March 31, 2021 has been included in other liabilities on our condensed consolidated balance sheet. We will re-measure the warrant liability at each reporting date. Changes in fair value of the warrant liability is included in investment and other income (expense) on our condensed consolidated statement of operations and comprehensive loss. See Note 6 for further discussions of the fair value of the warrants.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2021
Leases [Abstract]
Commitments and Contingencies	10. Commitments and Contingencies On April 5, 2019, we entered into a lease agreement, or the Lease, with Sun Life Assurance Company of Canada, or the Landlord, effective April 3, 2019, or the Commencement Date, for the lease of approximately 10,097 square feet of office space at 1100 Massachusetts Avenue, Cambridge, Massachusetts, or the Leased Premises. The term of the Lease commenced on the Commencement Date and expires on August 1, 2024, or the Expiration Date, approximately five years after the Rent Commencement Date as described below. Beginning August 1, 2019, or the Rent Commencement Date, the total base rent of the Lease will be $47,961 per month and will increase by approximately 3% on each anniversary of the Rent Commencement Date until the Expiration Date. In addition to the base rent, we are also responsible for our share of the operating expenses, insurance, real estate taxes and certain capital costs, and we are responsible for utilities in our premises, all in accordance with the terms of the Lease. Pursuant to the terms of the Lease, we provided a security deposit in the form of a letter of credit in the initial amount $300,000, which may be reduced to $150,000 over time in accordance with the terms of the Lease. The current portion of the security deposit is included on our condensed consolidated balance sheet as prepaid expenses and other current assets. The remaining portion plus the associated bank fee of $15,000 is included on our condensed consolidated balance sheet as restricted cash, less current portion as of March 31, 2021. The Landlord provided a lease incentive allowance of $0.6 million to fund certain improvements to be made by us to the Leased Premises.

Strategic Agreements

Strategic Agreements	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Strategic Agreements	11. Strategic Agreements We have worldwide development and commercialization rights to eganelisib, subject to certain obligations to our licensor, Takeda Pharmaceutical Company Limited, or Takeda, as described in more detail below. Additionally, we are obligated to pay Mundipharma International Corporation Limited, or Mundipharma, and Purdue Pharmaceutical Products L.P., or Purdue, a 4% royalty in the aggregate on worldwide net sales of products that were previously subject to our strategic alliance with Mundipharma and Purdue that was terminated in 2012. Such products include eganelisib; duvelisib, the PI3K delta,gamma inhibitor we licensed to Verastem, in 2016, and Verastem sold its interest in these rights to Secura Bio in 2020; and IPI-926, or patidegib, part of the hedgehog inhibitor program we licensed to PellePharm in 2013. We refer to such royalties as Trailing Mundipharma Royalties. After Mundipharma and Purdue have recovered approximately $260.0 million in royalty payments from all products that were previously subject to the strategic alliance, which represents the funding paid to us for research and development services performed by us under this strategic alliance, the Trailing Mundipharma Royalties will be reduced to a 1% royalty on net sales in the United States of such products. PellePharm In June 2013, we entered into a license agreement with PellePharm, under which we granted PellePharm exclusive global development and commercialization rights to our hedgehog inhibitor program, including patidegib, a clinical-stage product candidate. We refer to our license agreement with PellePharm as the PellePharm Agreement and products covered by the PellePharm Agreement as Hedgehog Products. We assessed this arrangement in accordance with Accounting Standard Codification 606 and concluded that at the date of contract inception there was only one performance obligation, consisting of the license, which was satisfied at contract inception. Under the PellePharm Agreement, PellePharm is obligated to pay us up to $9.0 million in remaining regulatory and commercial-based milestone payments through the first commercial sale of a Hedgehog Product. PellePharm is also obligated to pay us up to $37.5 million in success-based milestone payments upon the achievement of certain annual net sales thresholds, as well as a share of certain revenue received by PellePharm in the event that PellePharm sublicenses its rights under the PellePharm Agreement and tiered royalties on annual net sales of Hedgehog Products subject to specified conditions. The remaining milestones have not been recognized as they represent variable consideration that is constrained. In making this assessment, we considered numerous factors, including the fact that achievement of the milestones is outside of our control and contingent upon the future success of clinical trials, PellePharm’s actions, and the receipt of regulatory approval. As the single performance obligation was previously satisfied, all regulatory and commercial-based milestones will be recognized as revenue in full in the period in which the constraint is removed. Any consideration related to sales-based milestone payments, including royalties, will be recognized when the related sales occur as these amounts have been determined to relate predominantly to the license granted to PellePharm and therefore are recognized at the later of when the performance obligation is satisfied or the related sales occur. PellePharm is also obligated to pay us tiered royalties on annual net sales of Hedgehog Products, which are subject to reduction after a certain aggregate funding threshold has been achieved. On January 8, 2020, we entered into the BVF Funding Agreement, as further described in Note 9, pursuant to which we sold our interest in all royalty payments based on worldwide annual net sales of the BVF Licensed Product excluding Trailing Mundipharma Royalties related to patidegib. Takeda In July 2010, we entered into a development and license agreement with Intellikine, Inc., or Intellikine, under which we obtained rights to discover, develop and commercialize pharmaceutical products targeting the gamma and/or delta isoforms of PI3K, including eganelisib and duvelisib. In January 2012, Intellikine was acquired by Takeda. In December 2012, we amended and restated our development and license agreement with Takeda and further amended the agreement in July 2014, September 2016, July 2017, and March 2019. We refer to the amended and restated development and license agreement, as amended, as the Takeda Agreement. Duvelisib Pursuant to the Takeda Agreement, prior to March 4, 2019, we were obligated to share equally with Takeda all revenue arising from certain qualifying transactions for duvelisib, including the Secura Bio Agreement, subject to certain exceptions including revenue we receive as reimbursement for duvelisib research and development expenses. By entry into a fourth amendment on March 4, 2019, or the Takeda Amendment, Takeda consented to the sale of certain royalty payments based on worldwide annual net sales of Licensed Products under the Secura Bio Agreement to HCR and agreed to forego its rights to an equal share of the royalties due from Secura Bio during the term of the HCR Agreement, and agreed not to seek any payment from HCR with respect to the royalties owed to Takeda. In exchange, we paid Takeda $6.7 million representing 25% of the $30.0 million in gross proceeds we received from the closing of the HCR Agreement, net of 25% of the expenses incurred by us in connection with the HCR Agreement. In addition, we agreed to pay Takeda 25% of the royalties that would have been payable to us by Secura Bio but for the consummation of the HCR Agreement, which we refer to as the Interim Obligation. During the three months ended March 31, 2021 and 2020, we recognized $0.1 million during both periods, in Interim Obligation amounts owed to Takeda as royalty expense. We have the right to extinguish the Interim Obligation by payment to Takeda of an amount equal to (i) the $6.7 million payment multiplied by a specified multiple corresponding to the time period in which such extinguishing payment is made, minus (ii) any payments made to Takeda pursuant to the Interim Obligation. The Interim Obligation shall expire upon the termination of the HCR Agreement and the reversion of related royalties to us , at which time our obligations to share equally with Takeda the royalties payable under the Secura Bio Agreement shall be reinstated. Eganelisib Pursuant to the Takeda Agreement, we are obligated to pay Takeda up to $3.0 million in remaining success-based development milestone payments and up to $165.0 million in remaining regulatory and commercial-based milestone payments for one product candidate other than duvelisib, which could be eganelisib.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Stockholders' Equity	12. Stockholders’ Equity Public Offering On February 11, 2021, we entered into a purchase agreement with Piper Sandler & Co., as representative of the underwriters named therein, pursuant to which we issued and sold to the underwriters in an underwritten public offering an aggregate of 24,150,000 shares of our common stock, including 3,150,000 shares of common stock sold in connection with the exercise in full of a 15% over-allotment option by the underwriters. The public offering price was $3.80 per share. The gross proceeds to us from this offering were approximately $91.8 million. After underwriting discounts and commissions and estimated offering expenses, we received net proceeds from the offering of approximately $85.8 million. Common Stock Sales Facility

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	2. Basis of Presentation These condensed consolidated financial statements include the accounts of Infinity and its wholly-owned subsidiaries. We have eliminated all significant intercompany accounts and transactions in consolidation. The accompanying condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments, consisting of normal recurring accruals and revisions of estimates, considered necessary for a fair presentation of the accompanying condensed consolidated financial statements have been included. Interim results for the three months ended March 31, 2021 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2021. The information presented in the condensed consolidated financial statements and related footnotes at March 31, 2021, and for the three months ended March 31, 2021 and 2020, is unaudited, and the condensed consolidated balance sheet amounts and related footnotes at December 31, 2020 have been derived from our audited financial statements. For further information, please refer to the consolidated financial statements and accompanying footnotes included in our Annual Report on Form 10-K for the fiscal year ended December 31, 2020 filed with the U.S. Securities and Exchange Commission, or SEC, on March 16, 2021, which we refer to as our 2020 Annual Report on Form 10-K.
Liquidity	Liquidity As of March 31, 2021, we had cash and cash equivalents of $106.8 million. We have primarily incurred operating losses since inception and have relied on our ability to fund our operations through collaboration and license arrangements or other strategic arrangements, as well as through the sale of stock. We expect to continue to spend significant resources to fund the development and potential commercialization of eganelisib, also known as IPI-549, an orally administered, clinical-stage, immuno-oncology product candidate that reprograms macrophages through selective inhibition of the enzyme phosphoinositide-3-kinase-gamma, or PI3K-gamma, and to incur significant operating losses for the foreseeable future. We believe that our existing cash, cash equivalents and available-for-sale securities at March 31, 2021 will be adequate to satisfy our forecasted operating needs for at least the next twelve months from the issuance date of these financial statements.
Segment Information	Segment Information We operate in one business segment, which focuses on drug development. We make operating decisions based upon the performance of the enterprise as a whole and utilize our consolidated financial statements for decision making.
Basic and Diluted Net Income (Loss) per Common Share	Basic and Diluted Net Loss per Common ShareBasic net loss per share is based upon the weighted average number of common shares outstanding during the period. Diluted net loss per share is based upon the weighted average number of common shares outstanding during the period plus the effect of additional weighted average common equivalent shares outstanding during the period when the effect of adding such shares is dilutive. Common equivalent shares result from the assumed exercise of outstanding stock options and the exercise of outstanding warrants (the proceeds of which are then assumed to have been used to repurchase outstanding stock using the treasury stock method). In addition, the assumed proceeds under the treasury stock method include the average unrecognized compensation expense of stock options that are in-the-money. This results in the “assumed” buyback of additional shares, thereby reducing the dilutive impact of stock options. The two-class method is used for outstanding warrants as such warrants are considered to be participating securities, and this method is more dilutive than the treasury stock method.
New Accounting Pronouncements	New Accounting Pronouncements In June 2016, the Financial Accounting Standards Board, or FASB, issued Accounting Standard Update, or ASU, No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Statements, or ASU No. 2016-13, which requires that credit losses be reported using an expected losses model rather than the incurred losses model that is currently used, and it establishes additional disclosure requirements related to credit risks. For available-for-sale debt securities with expected credit losses, this standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. In November 2019, the FASB subsequently issued ASU 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates, whereby the effective date of this standard for smaller reporting companies was deferred to annual reporting periods beginning after December 15, 2022, including interim periods within those annual reporting periods, and early adoption is still permitted. We are currently evaluating the impact of ASU No. 2016-13 on our consolidated financial statements and related disclosures. In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity, or ASU No. 2020-06, which simplifies the guidance on an issuer’s accounting for convertible instruments and contracts in its own equity. The provisions of ASU No. 2020-06 are applicable for fiscal years beginning after December 15, 2023, with early adoption permitted no earlier than fiscal years beginning after December 15, 2020. We are currently evaluating the impact of ASU No. 2020-06 on our consolidated financial statements.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Schedule of Antidilutive Securities Excluded from Computation of Net Loss Per Share	The following outstanding shares of common stock equivalents were excluded from the computation of net loss per share attributable to common stockholders for the periods presented because including them would have been antidilutive: At March 31, 2021 2020 Stock options 12,404,270 11,175,463 Warrants (excluded from treasury stock method) — 1,000,000

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation Expense, Related to All Equity Awards	Total stock-based compensation expense related to all equity awards for the three months ended March 31, 2021 and 2020 was composed of the following: Three Months Ended March 31, 2021 2020 (in thousands) Research and development $ 151 $ 80 General and administrative 379 280 Total stock-based compensation expense $ 530 $ 360
Black-Scholes Valuation Model, Weighted-Average Assumptions for Stock Options	For the three months ended March 31, 2021 and 2020, the fair values were estimated using the Black-Scholes valuation model using the following weighted-average assumptions: Three Months Ended March 31, 2021 2020 Risk-free interest rate 1.1 % 1.6 % Expected annual dividend yield — — Expected stock price volatility 101.9 % 97.3 % Expected term of options 6.1 years 6.0 years

Cash, Cash Equivalents and Av_2

Cash, Cash Equivalents and Available-for-Sale Securities (Tables)	3 Months Ended
	Mar. 31, 2021
Cash and Cash Equivalents [Abstract]
Summary of Cash, Cash Equivalents and Available-for-sale Securities	The following is a summary of cash, cash equivalents and available-for-sale securities: March 31, 2021 Cost Gross Gross Estimated (in thousands) Cash and cash equivalents $ 106,756 $ — $ — $ 106,756 Total cash, cash equivalents and available-for-sale securities $ 106,756 $ — $ — $ 106,756 December 31, 2020 Cost Gross Gross Estimated (in thousands) Cash and cash equivalents $ 28,593 $ — $ — $ 28,593 Available-for-sale securities: U.S. Treasury securities due in one year or less 5,516 — (1) 5,515 Total available-for-sale securities 5,516 — (1) 5,515 Total cash, cash equivalents and available-for-sale securities $ 34,109 $ — $ (1) $ 34,108

Fair Value (Tables)

Fair Value (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value, Assets Measured on Recurring Basis	The following table presents the assets and liabilities carried at fair value measured on a recurring basis as of March 31, 2021 and December 31, 2020: March 31, 2021 Level 1 Level 2 Level 3 (in thousands) Assets: Cash and cash equivalents $ 106,756 $ — $ — Total assets $ 106,756 $ — $ — Liabilities: Warrant liability $ — $ — $ 205 Total liabilities $ — $ — $ 205 December 31, 2020 Level 1 Level 2 Level 3 (in thousands) Assets: Cash and cash equivalents $ 28,593 $ — $ — U.S. Treasury securities — 5,515 — Total assets $ 28,593 $ 5,515 $ — Liabilities: Warrant liability $ — $ — $ 198 Total liabilities $ — $ — $ 198

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	3 Months Ended
	Mar. 31, 2021
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consisted of the following: March 31, 2021 December 31, 2020 (in thousands) Prepaid expenses $ 2,202 $ 1,528 Restricted cash, current portion 150 150 Other current assets 197 234 Total prepaid expenses and other current assets $ 2,549 $ 1,912

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	3 Months Ended
	Mar. 31, 2021
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses and other current liabilities consisted of the following: March 31, 2021 December 31, 2020 (in thousands) Accrued clinical and development $ 4,667 $ 3,511 Accrued compensation and benefits 1,221 2,385 Liability related to sale of future royalties, net, current portion 895 848 Operating lease liability, current portion 498 489 Other 972 832 Total accrued expenses $ 8,253 $ 8,065

Liabilities Related to Sale o_2

Liabilities Related to Sale of Future Royalties (Tables)	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Schedule of Liability Related to Future Sale of Royalties	The following table shows the activity within the liability account for the three months ended March 31, 2021: March 31, 2021 (in thousands) Liability related to sale of future royalties, net - beginning balance $ 28,869 Non-cash royalty revenue (247) Non-cash interest expense recognized 38 Liability related to sale of future royalties, net - ending balance 28,660 Less: current portion (895) Liability related to sale of future royalties, net, less current portion $ 27,765 The following table shows the activity within the liability account for the three months ended March 31, 2021: March 31, 2021 (in thousands) Liability related to sale of future royalties, net - beginning balance $ 21,559 Non-cash interest expense recognized 7 Liability related to sale of future royalties, net - ending balance $ 21,566

Basis of Presentation (Details)

Basis of Presentation (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash, cash equivalents, and available-for-sale securities	$ 106,756	$ 34,108

Significant Accounting Polici_4

Significant Accounting Policies - Additional Information (Details)	3 Months Ended
	Mar. 31, 2021segment
Accounting Policies [Abstract]
Number of operating segments	1

Significant Accounting Polici_5

Significant Accounting Policies - Antidilutive Securities Excluded From Computation of Earnings Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	12,404,270	11,175,463
Warrants (excluded from treasury stock method)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	1,000,000

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 530	$ 360
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	151	80
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 379	$ 280

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Unrecognized compensation cost, net of estimated forfeitures, related to unvested stock options	$ 5
Unrecognized compensation cost, weighted-average recognition period, stock options	3 years 1 month 6 days
Stock options granted (in shares)	60,040	2,524,786
Stock options granted, weighted average fair value (in dollars per share)	$ 2.90	$ 0.96
Stock options granted, weighted average exercise price (in dollars per share)	$ 3.64	$ 1.23

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Options (Details) - Stock options	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.10%	1.60%
Expected annual dividend yield	0.00%	0.00%
Expected stock price volatility	101.90%	97.30%
Expected term of options	6 years 1 month 6 days	6 years

Cash, Cash Equivalents and Av_3

Cash, Cash Equivalents and Available-for-Sale Securities - Summary of Cash, Cash Equivalents and Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, cost	$ 106,756	$ 28,593	$ 30,485
Cash and cash equivalents, gross unrealized gains	0	0
Cash and cash equivalents, gross unrealized losses	0	0
Cash and cash equivalents, estimated fair value	106,756	28,593
Total available-for-sale securities		5,516
Total available-for-sale securities, gross unrealized gains		0
Total available-for-sale securities, gross unrealized losses		(1)
Total available-for-sale securities, estimated fair value		5,515
Total cash and cash equivalents and available-for-sale securities, at cost	106,756	34,109
Total cash, cash equivalents and available-for-sale securities, gross unrealized gains	0	0
Total cash, cash equivalents and available-for-sale securities, gross unrealized losses	0	(1)
Total cash, cash equivalents and available-for-sale securities, estimated fair value	$ 106,756	34,108
U.S. Treasury securities due in one year or less
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities		5,516
Available-for-sale securities, gross unrealized gains		0
Available-for-sale securities, gross unrealized losses		(1)
Available-for-sale securities, estimated fair value		$ 5,515

Cash, Cash Equivalents and Av_4

Cash, Cash Equivalents and Available-for-Sale Securities - Additional Information (Details)	3 Months Ended
	Mar. 31, 2021USD ($)security	Mar. 31, 2020USD ($)
Cash and Cash Equivalents [Abstract]
Debt securities, unrealized loss position, number | security	0
Available-for-sale securities, material realized gains or losses	$ 0	$ 0
Available-for-sale securities, other-than-temporary impairments	$ 0	$ 0

Fair Value - Schedule of Assets

Fair Value - Schedule of Assets Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 106,756	$ 28,593
U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury securities		5,515
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	106,756	28,593
Total assets	106,756	28,593
Warrant liability	0	0
Total liabilities	0	0
Fair Value, Measurements, Recurring | Level 1 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury securities		0
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Total assets	0	5,515
Warrant liability	0	0
Total liabilities	0	0
Fair Value, Measurements, Recurring | Level 2 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury securities		5,515
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Total assets	0	0
Warrant liability	205	198
Total liabilities	$ 205	198
Fair Value, Measurements, Recurring | Level 3 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury securities		$ 0

Fair Value - Additional Informa

Fair Value - Additional Information (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities		$ 5,515,000
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale securities	$ 0	$ 0

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses	$ 2,202	$ 1,528
Restricted cash, current portion	150	150	$ 0
Other current assets	197	234
Total prepaid expenses and other current assets	$ 2,549	$ 1,912

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued clinical and development	$ 4,667	$ 3,511
Accrued compensation and benefits	1,221	2,385
Liability related to sale of future royalties, net, current portion	895	848
Operating lease liability, current portion	498	489
Other	972	832
Total accrued expenses	$ 8,253	$ 8,065

Liabilities Related to Sale o_3

Liabilities Related to Sale of Future Royalties - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 08, 2020	Mar. 11, 2019	Mar. 31, 2021
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of warrants issued (in shares)			0
BVF Funding Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Warrant threshold, price per share (in dollars per share)	$ 3.75
Infinity Pharmaceuticals | Biotechnology Value Fund, L.P.
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Ownership percentage, noncontrolling interest	30.00%
Holdco | Infinity Pharmaceuticals | BVF Funding Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Option to purchase, percentage of outstanding equity interests	100.00%
HealthCare Royalty Partners III, L.P.
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Closing day payment		$ 30
Deferred transaction costs amortized		$ 2.4
BVF And Royalty Security, LLC | BVF Funding Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred transaction costs amortized	$ 0.4
Upfront purchase price	20
Warrant liability	$ 0.3
Period after closing date	36 months
Percentage of common stock called by warrant	50.00%
Exercise price of warrant, percentage of price per share	150.00%

Liabilities Related to Sale o_4

Liabilities Related to Sale of Future Royalties - Liability Activity (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Liability Related To Future Sale Of Royalties [Roll Forward]
Non-cash royalty revenue	$ (247)	$ (226)
Non-cash interest expense recognized	45	$ 38
Less: current portion	(895)		$ (848)
Liability related to sale of future royalties, net, less current portion	49,331		$ 28,021
HCR Agreement
Liability Related To Future Sale Of Royalties [Roll Forward]
Liability related to sale of future royalties, net - beginning balance	28,869
Non-cash royalty revenue	(247)
Non-cash interest expense recognized	38
Liability related to sale of future royalties, net, less current portion	28,660
Less: current portion	(895)
Liability related to sale of future royalties, net, less current portion	$ 27,765

Liabilities Related to Sale o_5

Liabilities Related to Sale of Future Royalties - Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Debt Instrument [Line Items]
Non-cash related party interest expense	$ 0	$ 534
BVF Funding Agreement
Debt Instrument [Line Items]
Liability related to sale of future royalties, net - beginning balance	21,559
Non-cash related party interest expense	7
Liability related to sale of future royalties, net - ending balance	$ 21,566

Commitments and Contingencies (

Commitments and Contingencies (Details)	12 Months Ended	48 Months Ended
	Jul. 31, 2020USD ($)	Aug. 01, 2024	Mar. 31, 2021USD ($)	Apr. 03, 2019USD ($)ft²
Leases Of Lessee Disclosure [Line Items]
Total future minimum lease payments			$ 2,100,000
1100 Massachusetts Avenue, Cambridge, Massachusetts
Leases Of Lessee Disclosure [Line Items]
Area of premises leased under lease agreement | ft²				10,097
Lease term				5 years
Monthly base rent expense	$ 47,961
Restricted cash, bank fee			$ 15,000
Leasehold improvements				$ 600,000
1100 Massachusetts Avenue, Cambridge, Massachusetts | Forecast
Leases Of Lessee Disclosure [Line Items]
Annual percentage increase of rent expense		3.00%
Letter of Credit | 1100 Massachusetts Avenue, Cambridge, Massachusetts
Leases Of Lessee Disclosure [Line Items]
Security deposit				300,000
Security deposit, reduced amount under lease term				$ 150,000

Strategic Agreements - Addition

Strategic Agreements - Additional Information (Details) $ in Thousands	Mar. 11, 2019USD ($)	Mar. 04, 2019USD ($)	Jun. 30, 2013USD ($)	Mar. 31, 2021USD ($)product	Mar. 31, 2020USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Royalty expense (note 11)				$ 282	$ 258
Number of distinct product candidates | product				1
Trailing Mundipharma
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Royalty percentage on sales. reimbursement of research and development, percentage				4.00%
Royalty payments, reimbursement of research and development upon completion				$ 260,000
Royalty percentage on sales, reimbursement of research and development upon completion, percentage				1.00%
PellePharm Agreement | Hedgehog Products
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaborative agreement, total remaining milestone payment amount			$ 9,000
Collaborative agreement, additional milestone payments amount, if circumstances met			$ 37,500
Takeda | Takeda Agreement, Fourth Amendment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Investment amount to be paid		$ 6,700
Percentage of investment amount		25.00%
Percentage of net expenses incurred		25.00%
Percentage of royalty payments		25.00%
Royalty expense (note 11)				$ 100	$ 100
HealthCare Royalty Partners III, L.P.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Closing day payment	$ 30,000
Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Additional success-based milestone payments to be paid				165,000
Maximum | Current
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Success-based remaining milestone payments				$ 3,000

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	Feb. 11, 2021	Jul. 29, 2019	Mar. 31, 2021	Mar. 31, 2020
Subsequent Event [Line Items]
Number of shares sold in transaction (in shares)	24,150,000		0	0
Shares sold, price per share (in dollars per share)	$ 3.80
Sale of stock, over-allotment option	15.00%
Gross proceeds from shares sold	$ 91.8
Net proceeds from shares sold	$ 85.8
Sales agreement, aggregate offering price (up to)		$ 20
Sales agreement, commission percentage		3.00%
Over-Allotment Option
Subsequent Event [Line Items]
Number of shares sold in transaction (in shares)	3,150,000