Karyopharm Therapeutics (KPTI) 10-Q 5 May 22 2022 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2022	Apr. 29, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Registrant Name	Karyopharm Therapeutics Inc.
Trading Symbol	KPTI
Entity Central Index Key	0001503802
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		79,418,349
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity File Number	001-36167
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-3931704
Entity Address, Address Line One	85 Wells Avenue, 2nd Floor
Entity Address, City or Town	Newton
Entity Address, Postal Zip Code	02459
City Area Code	617
Local Phone Number	658-0600
Document Quarterly Report	true
Document Transition Report	false
Entity Shell Company	false
Entity Address, State or Province	MA
Title of 12(b) Security	Common Stock
Security Exchange Name	NASDAQ

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 153,256	$ 190,459
Short-term investments	52,055	38,156
Accounts receivable, net	24,992	22,497
Inventory	3,874	4,106
Prepaid expenses	12,207	12,511
Other current assets	29,135	1,528
Restricted cash	1,014	6,349
Total current assets	276,533	275,606
Property and equipment, net	1,544	1,642
Operating lease right-of-use assets	7,518	7,915
Other assets	7,802	19,505
Restricted cash	636	637
Total assets	294,033	305,305
Current liabilities:
Accounts payable	3,440	1,603
Accrued expenses	58,371	69,121
Operating lease liabilities	2,463	2,316
Other current liabilities	2,063	678
Total current liabilities	66,337	73,718
Convertible senior notes	169,491	169,293
Deferred royalty obligation	132,998	132,998
Operating lease liabilities, net of current portion	8,286	8,969
Total liabilities	377,112	384,978
Stockholders' (deficit) equity:
Preferred stock, $0.0001 par value; 5,000 shares authorized; none issued and outstanding
Common stock, $0.0001 par value; 200,000 shares authorized; 79,419 and 75,746 shares issued and outstanding at March 31, 2022 and December 31, 2021, respectively	8	8
Additional paid-in capital	1,136,873	1,098,776
Accumulated other comprehensive income	87	191
Accumulated deficit	(1,220,047)	(1,178,648)
Total stockholders' deficit	(83,079)	(79,673)
Total liabilities and stockholders' (deficit) equity	$ 294,033	$ 305,305

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	79,419,000	75,746,000
Common stock, shares outstanding	79,419,000	75,746,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Revenues:
Total revenues	$ 47,670	$ 23,260
Operating expenses:
Cost of sales	1,426	933
Research and development	42,062	37,050
Selling, general and administrative	38,768	37,650
Total operating expenses	82,256	75,633
Loss from operations	(34,586)	(52,373)
Other income (expense):
Interest income	74	264
Interest expense	(6,684)	(5,095)
Other expense, net	(73)	(61)
Total other expense, net	(6,683)	(4,892)
Loss before income taxes	(41,269)	(57,265)
Income tax provision	(130)	(149)
Net loss	$ (41,399)	$ (57,414)
Net loss per share—basic and diluted	$ (0.53)	$ (0.77)
Weighted-average number of common shares outstanding used to compute net loss per share-basic and diluted	77,570	74,517
Product revenue
Revenues:
Total revenues	$ 28,300	$ 21,731
License and other revenue
Revenues:
Total revenues	$ 19,370	$ 1,529

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Statement of Comprehensive Income [Abstract]
Net loss	$ (41,399)	$ (57,414)
Comprehensive income (loss):
Unrealized loss on investments	(14)	(132)
Foreign currency translation adjustments	(90)	(85)
Comprehensive loss	$ (41,503)	$ (57,631)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating activities
Net loss	$ (41,399)	$ (57,414)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	177	235
Net amortization of premiums and discounts on investments	45	664
Amortization of debt discount and issuance costs	198	191
Stock-based compensation expense	7,336	7,359
Realized and unrealized gain on marketable equity securities	(2)	(14)
Inventory obsolescence charge	0	82
Changes in operating assets and liabilities:
Accounts receivable	(2,495)	(4,962)
Inventory	232	(552)
Prepaid expenses and other current assets	(27,303)	(89)
Operating lease right-of-use assets	397	343
Other noncurrent assets	11,703	0
Accounts payable	1,837	(1,410)
Accrued expenses and other liabilities	(9,387)	3,432
Deferred revenue	0	(297)
Operating lease liabilities	(536)	(456)
Net cash used in operating activities	(59,197)	(52,888)
Investing activities
Purchases of property and equipment	(79)	0
Proceeds from sales and maturities of investments	21,584	68,950
Purchases of investments	(35,540)	(25,764)
Net cash (used in) provided by investing activities	(14,035)	43,186
Financing activities
Proceeds from issuance of common stock, net of issuance costs	29,316	9,903
Proceeds from the exercise of stock options and shares issued under employee stock purchase plan	1,467	773
Net cash provided by financing activities	30,783	10,676
Effect of exchange rate on cash, cash equivalents and restricted cash	(90)	(91)
Net (decrease) increase in cash, cash equivalents and restricted cash	(42,539)	883
Cash, cash equivalents and restricted cash at beginning of period	197,445	89,121
Cash, cash equivalents and restricted cash at end of period	154,906	90,004
Reconciliation of cash, cash equivalents and restricted cash reported within the consolidated balance sheets
Cash and cash equivalents	153,256	88,471
Short-term restricted cash	1,014	815
Long-term restricted cash	636	718
Total cash, cash equivalents and restricted cash	154,906	90,004
Supplemental disclosures:
Deferred financing costs in accrued expenses	22	0
Cash paid for amounts included in the measurement of operating lease liabilities	841	815
Cash paid for interest on deferred royalty obligation	$ 15,784	$ 2,457

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive (loss) Income [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2020	$ 50,546	$ 7	$ 1,119,632	$ 518	$ (1,069,611)
Beginning balance,Shares at Dec. 31, 2020		73,923,000
Vesting of restricted stock (in shares)		409,000
Exercise of stock options and shares issued under the employee stock purchase plan	773		773
Exercise of stock options and shares issued under the employee stock purchase plan, (shares)		92,000
Stock-based compensation expense	7,359		7,359
Issuance of common stock, net of issuance costs	9,903	$ 1	9,902
Issuance of common stock, net of issuance costs (in Shares)		638,000
Cumulative effect adjustment for adoption of new accounting guidance	(50,590)		(65,641)		15,051
Unrealized loss on investments	(132)			(132)
Foreign currency translation adjustment	(85)			(85)
Net loss	(57,414)				(57,414)
Ending balance at Mar. 31, 2021	(39,640)	$ 8	1,072,025	301	(1,111,974)
Ending balance,Shares at Mar. 31, 2021		75,062,000
Beginning balance at Dec. 31, 2021	(79,673)	$ 8	1,098,776	191	(1,178,648)
Beginning balance,Shares at Dec. 31, 2021		75,746,000
Vesting of restricted stock (in shares)		565,000
Exercise of stock options and shares issued under the employee stock purchase plan	1,467		1,467
Exercise of stock options and shares issued under the employee stock purchase plan, (shares)		167,000
Stock-based compensation expense	7,336		7,336
Issuance of common stock, net of issuance costs	29,294		29,294
Issuance of common stock, net of issuance costs (in Shares)		2,941,000
Unrealized loss on investments	(14)			(14)
Foreign currency translation adjustment	(90)			(90)
Net loss	(41,399)				(41,399)
Ending balance at Mar. 31, 2022	$ (83,079)	$ 8	$ 1,136,873	$ 87	$ (1,220,047)
Ending balance,Shares at Mar. 31, 2022		79,419,000

Nature of Business and Basis of

Nature of Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Nature of Business and Basis of Presentation	1. Nature of Business and Basis of Presentation Nature of Business Karyopharm Therapeutics Inc., a Delaware corporation (collectively with its subsidiaries, the “Company,” “we,” “us,” or “our”), is a commercial-stage pharmaceutical company pioneering novel cancer therapies and dedicated to the discovery, development and commercialization of first-in-class drugs directed against nuclear export for the treatment of cancer and other diseases. We were incorporated in Delaware on December 22, 2008 and have a principal place of business in Newton, Massachusetts. Our scientific expertise is based upon an understanding of the regulation of intracellular communication between the nucleus and the cytoplasm. Our S elective I nhibitor of N uclear E xport (“SINE”) compounds function by binding with and inhibiting the nuclear export protein exportin 1 (“XPO1”). Our primary focus is on marketing XPOVIO ® (selinexor) in its currently approved indications as well as developing and seeking the regulatory approval of selinexor as an oral agent in multiple myeloma, endometrial cancer, and myelofibrosis, eltanexor in myelodysplastic syndromes and selinexor and eltanexor in additional cancer indications with significant unmet medical need. Our lead asset, XPOVIO, received its initial U.S. approval from the U.S. Food and Drug Administration (“FDA”) in July 2019 and is currently approved and marketed for the following indications: (i) in combination with bortezomib and dexamethasone for the treatment of adult patients with multiple myeloma who have received at least one prior therapy; (ii) in combination with dexamethasone for the treatment of adult patients with relapsed or refractory multiple myeloma who have received at least four prior therapies and whose disease is refractory to at least two proteasome inhibitors, at least two immunomodulatory agents, and an anti-CD38 monoclonal antibody; and (iii) for the treatment of adult patients with relapsed or refractory diffuse large B-cell lymphoma (“DLBCL”), not otherwise specified, including DLBCL arising from follicular lymphoma, after at least two lines of systemic therapy. In addition, in March 2021 and May 2021, the European Commission and the United Kingdom’s Medicines & Healthcare Products Regulatory Agency granted conditional approval, respectively, of NEXPOVIO ® (selinexor), the brand name for selinexor in Europe and the United Kingdom, in combination with dexamethasone, to treat adult patients with multiple myeloma who have received at least four prior therapies and whose disease is refractory to at least two proteasome inhibitors, two immunomodulatory agents, and an anti-CD38 monoclonal antibody, and who have demonstrated disease progression on the last therapy. XPOVIO has also received regulatory approval in various indications in Australia, Singapore, Mainland China, South Korea and Israel. Basis of Presentation The accompanying unaudited condensed consolidated financial statements of the Company have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial reporting and as required by Regulation S-X, Rule 10-01. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (including those which are normal and recurring) considered necessary for a fair presentation of the interim financial information have been included. When preparing financial statements in conformity with GAAP, we must make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, expenses and related disclosures at the date of the financial statements. Actual results could differ from those estimates. Additionally, operating results for the three months ended March 31, 2022 are not necessarily indicative of the results that may be expected for any other interim period or for the fiscal year ending December 31, 2022. For further information, refer to the financial statements and footnotes included in our Annual Report on Form 10-K for the year ended December 31, 2021 as filed with the Securities and Exchange Commission (“SEC”) on March 1, 2022 (“Annual Report”). Basis of Consolidation The condensed consolidated financial statements at March 31, 2022 include the accounts of Karyopharm Therapeutics Inc. and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The significant accounting policies used in preparation of these condensed consolidated financial statements in this Form 10-Q are consistent with those discussed in Note 2, “ Summary of Significant Accounting Policies ,” in our Annual Report.

Product Revenue

Product Revenue	3 Months Ended
	Mar. 31, 2022
Product Revenue [Member]
Product Revenue	2. Product Revenue To date, our only source of product revenue has been from the U.S. sales of XPOVIO. Net product revenue, including provisions primarily consisting of distribution fees and cash discounts, as well as reserves for chargebacks, rebates and returns, were as follows (in thousands): For the Three Months 2022 2021 Gross product revenue $ 34,910 $ 27,544 Provisions for product revenue ( 6,610 ) ( 5,813 ) Total product revenue, net $ 28,300 $ 21,731 As of March 31, 2022 and December 31, 2021, net product revenue of $ 21.6 million and $ 20.0 million, respectively, were included in accounts receivable. To date, we have had no bad debt write-offs and we do not currently have credit issues with any customers. There were no credit losses associated with our accounts receivables as of March 31, 2022 and December 31, 2021 .

Inventory

Inventory	3 Months Ended
	Mar. 31, 2022
Inventory Disclosure [Abstract]
Inventory	3. Inventory The following table presents our inventory of XPOVIO (in thousands): March 31, December 31, Raw materials $ 2,563 $ 1,797 Work in process 926 1,895 Finished goods 385 414 Total inventory $ 3,874 $ 4,106 As of March 31, 2022 and December 31, 2021, all of our inventory was related to XPOVIO, which was initially approved by the FDA in July 2019 and at which time we began to capitalize costs to manufacture XPOVIO. Prior to FDA approval of XPOVIO, all costs related to the manufacturing of XPOVIO and related material were charged to research and development expense in the period incurred.

License and Asset Purchase Agre

License and Asset Purchase Agreements	3 Months Ended
	Mar. 31, 2022
License and Asset Purchase Agreements [Member]
License and Asset Purchase Agreements	4. License and Asset Purchase Agreements In prior periods, we entered into out-licensing and asset purchase agreements with Berlin-Chemie AG, an affiliate of the Menarini Group (“Menarini”), Anivive Lifesciences, Inc. (“Anivive”), Biogen MA Inc. (“Biogen”), Antengene Therapeutics Limited (“Antengene”), and FORUS Therapeutics Inc. (“FORUS”), all of which are accounted for within the scope of Accounting Standards Codification 606, Revenue from Contracts with Customers (“ASC 606”). For further details on the terms and accounting treatment considerations for these contracts, please refer to Note 10, “ License and Asset Purchase Agreements ,” to our consolidated financial statements contained in Item 8 of our Annual Report. D uring the three months ended March 31, 2022, we recognized $ 8.6 million in milestone-related revenue from our partners and $ 7.1 million related to reimbursement of development related expenses from Menarini. With respect to the $ 8.6 million in milestone-related revenue, we recognized $ 7.8 million, net of tax, pursuant to our license agreement with Antengene and $ 0.8 million pursuant to our distribution agreement with Promedico Ltd. during the three months ended March 31, 2022. We recognized $ 0.8 million in license and other revenue pursuant to our license agreements with Antengene and others, for the three months ended March 31, 2021.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2022
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	5. Fair Value of Financial Instruments Financial instruments, including cash, restricted cash, prepaid expenses and other current assets, accounts payable and accrued expenses, are presented at amounts that approximate fair value at March 31, 2022 and December 31, 2021. We are required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. The fair value hierarchy prioritizes valuation inputs based on the observable nature of those inputs. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The hierarchy defines three levels of valuation inputs: Level 1 inputs - Quoted prices in active markets for identical assets or liabilities Level 2 inputs - Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly Level 3 inputs - Unobservable inputs that reflect our own assumptions about the assumptions market participants would use in pricing the asset or liability Our cash equivalents are comprised of money market funds, U.S. government and agency securities and commercial paper as presented in the tables below. We measure these investments at fair value. The fair value of cash equivalents is determined based on “Level 1” or “Level 2” inputs. Items classified as Level 2 within the valuation hierarchy consist of corporate debt securities, commercial paper and U.S. government and agency securities. We estimate the fair values of these marketable securities by taking into consideration valuations obtained from third-party pricing sources. These pricing sources utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include market pricing based on real-time trade data for the same or similar securities, issuer credit spreads, benchmark yields, and other observable inputs. We validate the prices provided by our third-party pricing sources by understanding the models used, obtaining market values from other pricing sources and analyzing pricing data in certain instances. In certain cases where there is limited activity or less transparency around inputs to valuation, the related assets or liabilities are classified as Level 3. The embedded derivative liability associated with our deferred royalty obligation, as discussed further in Note 10, “ Long-Term Obligations ”, is measured at fair value using an option pricing Monte Carlo simulation model and is included as a component of the deferred royalty obligation. The embedded derivative liability is subject to remeasurement at the end of each reporting period, with changes in fair value recognized as a component of other expense, net. The assumptions used in the option pricing Monte Carlo simulation model include: (1) our estimates of the probability and timing of related events; (2) the probability-weighted net sales of XPOVIO and any of our other future products, including worldwide net product sales, upfront payments, milestones and royalties; (3) our risk-adjusted discount rate that includes a company specific risk premium; (4) our cost of debt; (5) volatility; and (6) the probability of a change in control occurring during the term of the instrument. Our embedded derivative liability, as well as the estimated fair value of the deferred royalty obligation, is described in Note 2, “ Summary of Significant Accounting Policies ,” and Note 16, “ Long-Term Obligations ” to our consolidated financial statements contained in Item 8 of our Annual Report. The following tables present information about our financial assets and liability that have been measured at fair value and indicate the fair value hierarchy of the valuation inputs utilized to determine such fair value (in thousands): Description As of March 31, 2022 Quoted Significant Significant Financial assets Cash equivalents: Money market funds $ 45,209 $ 45,209 $ — $ — U.S. government and agency securities 28,994 28,994 — — Commercial paper 23,985 — 23,985 — Investments: Short-term: Corporate debt securities 11,127 — 11,127 — Commercial paper 11,984 — 11,984 — U.S. government and agency securities 28,944 — 28,944 — $ 150,243 $ 74,203 $ 76,040 $ — Financial liability Embedded derivative liability $ 3,080 $ — $ 3,080 Description As of December 31, 2021 Quoted Significant Significant Financial assets Cash equivalents: Money market funds $ 32,947 $ 32,947 $ — $ — U.S. government and agency securities 12,000 12,000 — — Commercial paper 11,998 — 11,998 — Investments: Short-term: Corporate debt securities 24,269 — 24,269 — Commercial paper 12,995 — 12,995 — U.S. government and agency securities 892 — 892 — $ 95,101 $ 44,947 $ 50,154 $ — Financial liability Embedded derivative liability $ 3,080 $ — $ 3,080

Investments

Investments	3 Months Ended
	Mar. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Investments	6. Investments The following tables summarize our investments in debt securities, classified as available-for-sale (in thousands): As of March 31, 2022 Amortized Total Total Aggregate Fair Value Short-term: Corporate debt securities $ 11,131 $ 3 $ ( 7 ) $ 11,127 Commercial paper 11,990 — ( 6 ) 11,984 U.S. government and agency securities 28,950 2 ( 8 ) 28,944 $ 52,071 $ 5 $ ( 21 ) $ 52,055 As of December 31, 2021 Amortized Total Total Aggregate Fair Value Short-term: Corporate debt securities $ 24,272 $ 3 $ ( 6 ) $ 24,269 Commercial paper 12,998 — ( 3 ) 12,995 U.S. government and agency securities 891 1 — 892 $ 38,161 $ 4 $ ( 9 ) $ 38,156 We determine the appropriate classification of our investments in debt securities at the time of purchase. All of our securities are classified as available-for-sale and are reported as short-term investments or long-term investments based on maturity dates and whether such assets are reasonably expected to be realized in cash or sold or consumed during the normal cycle of business. Available-for-sale investments are recorded at fair value. Short-term and long-term investments are composed of corporate debt securities, commercial paper and U.S. government and agency securities. We review investments whenever the fair value of an investment is less than the amortized cost and evidence indicates that an investment’s carrying amount is not recoverable within a reasonable period of time. We evaluate whether the decline in fair value has resulted from credit losses or other factors. In making this assessment, we consider the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency, and adverse conditions specifically related to the security, among other factors. If this assessment indicates that a credit loss exists, the present value of cash flows expected to be collected from the security is compared to the amortized cost basis of the security. If the present value of cash flows expected to be collected is less than the amortized cost basis, a credit loss exists and an allowance for credit losses is recorded on our condensed consolidated balance sheet, limited by the amount that the fair value is less than the amortized cost basis. Any impairment that is no t related to a credit loss is recognized in other comprehensive income. Changes in the allowance for credit losses are recorded as a provision for (or reversal of) credit loss expense. Losses are charged against the allowance when we believe the uncollectability of an available-for-sale security is confirmed or when either of the criteria regarding intent or requirement to sell is met. The unrealized losses at March 31, 2022 and December 31, 2021 were attributable to changes in interest rates, and we do not believe any unrealized losses represent credit losses. We held 16 and 37 commercial paper and corporate debt securities at March 31, 2022 and December 31, 2021, respectively, that were in an unrealized loss position. We do not intend to sell the investments before recovery of their amortized cost bases, which may be at maturity. The following tables summarize our available-for-sale securities in an unrealized loss position for which an allowance for credit losses has not been recorded, aggregated by major security type and length of time in a continuous unrealized loss position (in thousands): As of March 31, 2022 Less than 12 Months 12 Months or Longer Total Aggregate Related Fair Value Unrealized Aggregate Related Fair Value Unrealized Aggregate Related Fair Value Unrealized Corporate debt securities $ 8,123 $ ( 7 ) $ — $ — $ 8,123 $ ( 7 ) Commercial paper 11,984 ( 6 ) — — 11,984 ( 6 ) U.S. government and agency securities 21,949 ( 8 ) — — 21,949 ( 8 ) Total $ 42,056 $ ( 21 ) $ — $ — $ 42,056 $ ( 21 ) As of December 31, 2021 Less than 12 Months 12 Months or Longer Total Aggregate Related Fair Value Unrealized Aggregate Related Fair Value Unrealized Aggregate Related Fair Value Unrealized Corporate debt securities $ 16,655 $ ( 6 ) $ — $ — $ 16,655 $ ( 6 ) Commercial paper 9,995 ( 3 ) — — 9,995 ( 3 ) Total $ 26,650 $ ( 9 ) $ — $ — $ 26,650 $ ( 9 )

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2022
Earnings Per Share [Abstract]
Net Loss Per Share	7. Net Loss Per Share Basic and diluted net loss per common share is calculated by dividing net loss by the weighted-average number of common shares outstanding for the period. Diluted net loss per share is computed by dividing the diluted net loss by the weighted average number of common shares, including potential dilutive common shares assuming the dilutive effect of outstanding stock options and unvested restricted common stock. For periods in which the Company has reported net losses, diluted net loss per common share is the same as basic net loss per share, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. The following potentially dilutive securities were excluded from the calculation of diluted net loss per share due to their anti-dilutive effect (in thousands): As of March 31, 2022 2021 Outstanding stock options 13,477 12,900 Unvested restricted stock units 3,798 2,517 We have the option to settle the conversion obligation for our 3.00 % convertible senior notes due 2025 (the “Notes”) in cash, shares or any combination of the two. Based on our net loss position, there was no impact on the calculation of dilutive loss per share during the three months ended March 31, 2022 and 2021 .

Stock-based Compensation Expens

Stock-based Compensation Expense	3 Months Ended
	Mar. 31, 2022
Share-based Payment Arrangement [Abstract]
Stock-based Compensation Expense	8. Stock-based Compensation Expense The following table summarizes stock-based compensation expense included in operating expenses (in thousands): For the Three Months 2022 2021 Cost of sales $ 55 $ 44 Research and development 2,968 2,932 Selling, general and administrative 4,313 4,383 Total $ 7,336 $ 7,359

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2022
Equity [Abstract]
Stockholders' Equity	9. Stockholders’ Equity Open Market Sale Agreement On August 17, 2018, we entered into an Open Market Sale Agreement (the “Open Market Sale Agreement”) with Jefferies LLC, as agent (“Jefferies”), pursuant to which we may issue and sell shares of our common stock having an aggregate offering price of up to $ 75.0 million from time to time through Jefferies (the “Open Market Offering”). On May 5, 2020, we entered into Amendment No. 1 to the Open Market Sale Agreement, pursuant to which we increased the maximum aggregate offering price of shares of our common stock that we may issue and sell from time to time through Jefferies, by $ 100.0 million, from $ 75.0 million to up to $ 175.0 million (the “Open Market Shares”). Under the Open Market Sale Agreement, Jefferies may sell the Open Market Shares by methods deemed to be an “at the market offering” as defined in Rule 415(a)(4) promulgated under the Securities Act of 1933, as amended (the “Securities Act”). We may sell the Open Market Shares in amounts and at times to be determined by us from time to time subject to the terms and conditions of the Open Market Sale Agreement, but we have no obligation to sell any of the Open Market Shares in an Open Market Offering. We or Jefferies may suspend or terminate the offering of Open Market Shares upon notice to the other party and subject to other conditions. We have agreed to pay Jefferies commissions for its services in acting as agent in the sale of the Open Market Shares in the amount of up to 3.0 % of gross proceeds from the sale of the Open Market Shares pursuant to the Open Market Sale Agreement. We have also agreed to provide Jefferies with customary indemnification and contribution rights. We sold an aggregate of 2,941,517 Open Market Shares under the Open Market Sale Agreement, for net proceeds of approximately $ 29.3 million, during the three months ended March 31, 2022. We sold an aggregate of 638,341 Open Market Shares under the Open Market Sale Agreement, for net proceeds of approximately $ 9.9 million, during the three months ended March 31, 2021. As of March 31, 2022, $ 70.7 million of Open Market Shares may be issued and sold under the Open Market Sale Agreement.

Long-Term Obligations

Long-Term Obligations	3 Months Ended
	Mar. 31, 2022
Long-Term Obligations	10. Long-Term Obligation s 3.00% Convertible Senior Notes due 2025 On October 16, 2018, we completed an offering of $ 150.0 million aggregate principal amount of the Notes. In addition, on October 26, 2018, we issued an additional $ 22.5 million aggregate principal amount of the Notes pursuant to the full exercise of the option to purchase additional Notes granted to the initial purchasers in the offering. The Notes were sold in a private offering to qualified institutional buyers in reliance on Rule 144A under the Securities Act. In connection with the issuance of the Notes, we incurred approximately $ 5.6 million of debt issuance costs, which primarily consisted of underwriting, legal and other professional fees. Debt issuance costs are being amortized to interest expense using the effective interest method over seven years . The Notes are senior unsecured obligations and bear interest at a rate of 3.00 % per year payable semiannually in arrears on April 15 and October 15 of each year, beginning on April 15, 2019. Upon conversion, the Notes will be converted into cash, shares of our common stock, or a combination of cash and shares of our common stock, at our election. The Notes will be subject to redemption at our option, on or after October 15, 2022, in whole or in part, if the conditions described below are satisfied. The Notes will mature on October 15, 2025 , unless earlier converted, redeemed or repurchased in accordance with their terms. Subject to satisfaction of certain conditions and during the periods described below, the Notes may be converted at an initial conversion rate of 63.0731 shares of common stock per $ 1 principal amount of the Notes (equivalent to an initial conversion price of approximately $ 15.85 per share of common stock). Holders of the Notes may convert all or any portion of their Notes, in multiples of $ 1 principal amount, at their option at any time prior to the close of business on the business day immediately preceding June 15, 2025 only under the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on December 31, 2018 (and only during such calendar quarter), if the last reported sale price of our common stock for at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to 130 % of the conversion price for the Notes on each applicable trading day; (2) during the five business day period immediately after any five consecutive trading day period (the “Measurement Period”) in which the trading price per $ 1,000 principal amount of Notes for each trading day of the Measurement Period was less than 98 % of the product of the last reported sale price of our common stock and the conversion rate on each such trading day; (3) if we call the Notes for redemption, until the close of business on the business day immediately preceding the redemption date; or (4) upon the occurrence of specified corporate events as described within the indenture governing the Notes. As of March 31, 2022, none of the above circumstances had occurred and as such, the Notes could not have been converted. We may not redeem the Notes prior to October 15, 2022. On or after October 15, 2022, we may redeem for cash all or part of the Notes at our option if the last reported sale price of our common stock equals or exceeds 130 % of the conversion price then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period ending within five trading days prior to the date on which we send any notice of redemption. The redemption price will be 100 % of the principal amount of the Notes to be redeemed, plus accrued and unpaid interest, if any. In addition, calling any convertible note for redemption will constitute a make-whole fundamental change with respect to that convertible note, in which case the conversion rate applicable to the conversion of that convertible note, if it is converted in connection with the redemption, will be increased in certain circumstances. The outstanding balances of the Notes consisted of the following (in thousands): March 31, December 31, Principal $ 172,500 $ 172,500 Less: debt issuance costs ( 3,009 ) ( 3,207 ) Net carrying amount $ 169,491 $ 169,293 We determined the expected life of the Notes was equal to its seven-year term. The effective interest rate on the Notes was 11.85 %. As of March 31, 2022, the “if-converted value” did not exceed the remaining principal amount of the Notes. The fair value of the Notes was determined based on data points other than quoted prices that are observable, either directly or indirectly, and has been classified as Level 2 within the fair value hierarchy. The fair value of the Notes, which differs from their carrying value, is influenced by market interest rates, our stock price and stock price volatility. The estimated fair value of the Notes as of March 31, 2022 and December 31, 2021 was approximately $ 141.9 million and $ 139.2 million, respectively. The following table sets forth total interest expense recognized related to the Notes for the periods indicated (in thousands): For the Three Months 2022 2021 Contractual interest expense $ 1,294 $ 1,294 Amortization of debt issuance costs 198 191 Total $ 1,492 $ 1,485 Future minimum payments on the Notes as of March 31, 2022 were as follows (in thousands): Years ended December 31, Future Minimum 2022 $ 5,175 2023 5,175 2024 5,175 2025 177,675 Total minimum payments $ 193,200 Less: interest and issuance costs ( 23,709 ) Convertible senior notes $ 169,491 Deferred Royalty Obligation In September 2019, we entered into a Revenue Interest Financing Agreement (“the Revenue Interest Agreement”) with HealthCare Royalty Partners III, L.P. and HealthCare Royalty Partners IV, L.P. (“HCR”). In June 2021, we, and certain of our subsidiaries, entered into an amendment of the Revenue Interest Agreement (the “Amended Revenue Interest Agreement”) with, among others, HCR. We received $ 75.0 million, less certain transaction expenses, upon closing of the Revenue Interest Agreement (the “First Investment Amount”) and $ 60.0 million upon closing of the Amended Revenue Interest Agreement (the “Second Investment Amount” and together with the First Investment Amount, the “deferred royalty obligation”). In exchange for the above payments, HCR receives payments from us at a tiered percentage (the “Applicable Tiered Percentage”) of net revenues of selinexor and any of our other future products, including worldwide net product sales and upfront payments, milestones, and royalties. The Applicable Tiered Percentage is subject to reduction in the future if a target based on cumulative U.S. net sales of selinexor is met. Total payments to HCR are capped at 185 % of the Investment Amount. If HCR has not received 65 % of the First Investment Amount by December 31, 2022, 100 % of the First Investment Amount and 65 % of the Second Investment amount by December 31, 2024, or 100 % of both the First Investment Amount and the Second Investment Amount by September 30, 2026, we must make a cash payment sufficient to gross up the payments to such minimum amounts. As the repayment of the funded amount is contingent upon worldwide net product sales and upfront payments, milestones, and royalties, the repayment term may be shortened or extended depending on actual worldwide net product sales and upfront payments, milestones, and royalties. The repayment period commenced on October 1, 2019 for the First Investment Amount and on July 1, 2021 for the Second Investment Amount, and expires on the earlier of (i) the date in which HCR has received cash payments totaling an aggregate of 185 % of the Investment Amount or (ii) the legal maturity date of October 1, 2031. If HCR has not received payments equal to 185 % of the Investment Amount by the twelve-year anniversary of the initial closing date, we will be required to pay an amount equal to the Investment Amount plus a specific annual rate of return less payments previously received by HCR. In the event of a change of control, we are obligated to pay HCR an amount equal to 185 % of the Investment Amount less payments previously received by HCR. In addition, upon the occurrence of an event of default, including, among others, our failure to pay any amounts due to HCR under the deferred royalty obligation, insolvency, our failure to pay indebtedness when due, the revocation of regulatory approval of XPOVIO in the U.S. or our breach of any covenant contained in the Amended Revenue Interest Agreement and our failure to cure the breach within the prescribed time frame, we are obligated to pay HCR an amount equal to 185 % of the Investment Amount less payments previously received by HCR. In addition, upon an event of default, HCR may exercise all other rights and remedies available under the Amended Revenue Interest Agreement, including foreclosing on the collateral that was pledged to HCR, which consists of all of our present and future assets relating to XPOVIO. As of March 31, 2022 , we have made $ 32.2 million in payments to HCR. We have evaluated the terms of the deferred royalty obligation and concluded that the features of both the First Investment Amount and Second Investment Amount are similar to those of a debt instrument. Accordingly, we have accounted for the transaction as long-term debt and presented it as a deferred royalty obligation on our condensed consolidated balance sheet. We have further evaluated the terms of the debt and determined that the repayment of 185 % of the Investment Amount, less any payments made to date, upon a change of control is an embedded derivative that requires bifurcation from the debt instrument and fair value recognition. We determined the fair value of the derivative using an option pricing Monte Carlo simulation model taking into account the probability of change of control occurring and potential repayment amounts and timing of such payments that would result under various scenarios, as further described in Note 5, “ Fair Value of Financial Instruments” to our condensed consolidated financial statements. The aggregate fair value of the embedded derivative liability was $ 3.1 million as of both March 31, 2022 and December 31, 2021. We remeasure the embedded derivative to fair value each reporting period until the time the features lapse and/or termination of the deferred royalty obligation. The effective interest rate as of March 31, 2022 was approximately 16.5 %. In connection with the First Investment Amount, we incurred debt issuance costs totaling $ 1.4 million. Debt issuance costs have been netted against the debt and are being amortized over the estimated term of the debt using the effective interest method, adjusted on a prospective basis for changes in the underlying assumptions and inputs. The assumptions used in determining the expected repayment term of the debt and amortization period of the issuance costs requires that we make estimates that could impact the short and long-term classification of these costs, as well as the period over which these costs will be amortized. The carrying value of the deferred royalty obligation at both March 31, 2022 and December 31, 2021 was $ 129.9 million based on $ 135.0 million of proceeds, net of the fair value of the bifurcated embedded derivative liability upon execution of the Revenue Interest Agreement and the Amended Revenue Interest Agreement, and debt issuance costs incurred. The carrying value of the deferred royalty obligation approximated fair value at March 31, 2022 and December 31, 2021 and was measured using Level 3 inputs. The estimated fair market value was calculated using an option pricing Monte Carlo simulation model with inputs consistent with those used in determining the embedded derivative values as described in Note 5, “ Fair Value of Financial Instruments” to our condensed consolidated financial statements.

Nature of Business and Basis _2

Nature of Business and Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements of the Company have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial reporting and as required by Regulation S-X, Rule 10-01. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (including those which are normal and recurring) considered necessary for a fair presentation of the interim financial information have been included. When preparing financial statements in conformity with GAAP, we must make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, expenses and related disclosures at the date of the financial statements. Actual results could differ from those estimates. Additionally, operating results for the three months ended March 31, 2022 are not necessarily indicative of the results that may be expected for any other interim period or for the fiscal year ending December 31, 2022. For further information, refer to the financial statements and footnotes included in our Annual Report on Form 10-K for the year ended December 31, 2021 as filed with the Securities and Exchange Commission (“SEC”) on March 1, 2022 (“Annual Report”).
Basis of Consolidation	Basis of Consolidation The condensed consolidated financial statements at March 31, 2022 include the accounts of Karyopharm Therapeutics Inc. and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The significant accounting policies used in preparation of these condensed consolidated financial statements in this Form 10-Q are consistent with those discussed in Note 2, “ Summary of Significant Accounting Policies ,” in our Annual Report.

Product Revenue (Tables)

Product Revenue (Tables)	3 Months Ended
	Mar. 31, 2022
XPOVIO [Member]
Summary of Product Revenue	To date, our only source of product revenue has been from the U.S. sales of XPOVIO. Net product revenue, including provisions primarily consisting of distribution fees and cash discounts, as well as reserves for chargebacks, rebates and returns, were as follows (in thousands): For the Three Months 2022 2021 Gross product revenue $ 34,910 $ 27,544 Provisions for product revenue ( 6,610 ) ( 5,813 ) Total product revenue, net $ 28,300 $ 21,731

Inventory (Tables)

Inventory (Tables)	3 Months Ended
	Mar. 31, 2022
Inventory Disclosure [Abstract]
Schedule of Inventory, Current	The following table presents our inventory of XPOVIO (in thousands): March 31, December 31, Raw materials $ 2,563 $ 1,797 Work in process 926 1,895 Finished goods 385 414 Total inventory $ 3,874 $ 4,106

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2022
Fair Value Disclosures [Abstract]
Schedule of Financial Assets That Have Been Measured at Fair Value	The following tables present information about our financial assets and liability that have been measured at fair value and indicate the fair value hierarchy of the valuation inputs utilized to determine such fair value (in thousands): Description As of March 31, 2022 Quoted Significant Significant Financial assets Cash equivalents: Money market funds $ 45,209 $ 45,209 $ — $ — U.S. government and agency securities 28,994 28,994 — — Commercial paper 23,985 — 23,985 — Investments: Short-term: Corporate debt securities 11,127 — 11,127 — Commercial paper 11,984 — 11,984 — U.S. government and agency securities 28,944 — 28,944 — $ 150,243 $ 74,203 $ 76,040 $ — Financial liability Embedded derivative liability $ 3,080 $ — $ 3,080 Description As of December 31, 2021 Quoted Significant Significant Financial assets Cash equivalents: Money market funds $ 32,947 $ 32,947 $ — $ — U.S. government and agency securities 12,000 12,000 — — Commercial paper 11,998 — 11,998 — Investments: Short-term: Corporate debt securities 24,269 — 24,269 — Commercial paper 12,995 — 12,995 — U.S. government and agency securities 892 — 892 — $ 95,101 $ 44,947 $ 50,154 $ — Financial liability Embedded derivative liability $ 3,080 $ — $ 3,080

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Summary of Investments, Classified as Available-for-Sale	The following tables summarize our investments in debt securities, classified as available-for-sale (in thousands): As of March 31, 2022 Amortized Total Total Aggregate Fair Value Short-term: Corporate debt securities $ 11,131 $ 3 $ ( 7 ) $ 11,127 Commercial paper 11,990 — ( 6 ) 11,984 U.S. government and agency securities 28,950 2 ( 8 ) 28,944 $ 52,071 $ 5 $ ( 21 ) $ 52,055 As of December 31, 2021 Amortized Total Total Aggregate Fair Value Short-term: Corporate debt securities $ 24,272 $ 3 $ ( 6 ) $ 24,269 Commercial paper 12,998 — ( 3 ) 12,995 U.S. government and agency securities 891 1 — 892 $ 38,161 $ 4 $ ( 9 ) $ 38,156
Debt Securities Available-For-Sale	The following tables summarize our available-for-sale securities in an unrealized loss position for which an allowance for credit losses has not been recorded, aggregated by major security type and length of time in a continuous unrealized loss position (in thousands): As of March 31, 2022 Less than 12 Months 12 Months or Longer Total Aggregate Related Fair Value Unrealized Aggregate Related Fair Value Unrealized Aggregate Related Fair Value Unrealized Corporate debt securities $ 8,123 $ ( 7 ) $ — $ — $ 8,123 $ ( 7 ) Commercial paper 11,984 ( 6 ) — — 11,984 ( 6 ) U.S. government and agency securities 21,949 ( 8 ) — — 21,949 ( 8 ) Total $ 42,056 $ ( 21 ) $ — $ — $ 42,056 $ ( 21 ) As of December 31, 2021 Less than 12 Months 12 Months or Longer Total Aggregate Related Fair Value Unrealized Aggregate Related Fair Value Unrealized Aggregate Related Fair Value Unrealized Corporate debt securities $ 16,655 $ ( 6 ) $ — $ — $ 16,655 $ ( 6 ) Commercial paper 9,995 ( 3 ) — — 9,995 ( 3 ) Total $ 26,650 $ ( 9 ) $ — $ — $ 26,650 $ ( 9 )

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2022
Earnings Per Share [Abstract]
Schedule of Potentially Dilutive Securities Were Excluded From The Calculation of Diluted Net Loss Per Share Due to Their Anti-Dilutive Effect	The following potentially dilutive securities were excluded from the calculation of diluted net loss per share due to their anti-dilutive effect (in thousands): As of March 31, 2022 2021 Outstanding stock options 13,477 12,900 Unvested restricted stock units 3,798 2,517

Stock-based Compensation (Table

Stock-based Compensation (Tables)	3 Months Ended
	Mar. 31, 2022
Share-based Payment Arrangement [Abstract]
Schedule of Total Stock-based Compensation Expense Recognized in Connection with All Share-based Payment Awards	The following table summarizes stock-based compensation expense included in operating expenses (in thousands): For the Three Months 2022 2021 Cost of sales $ 55 $ 44 Research and development 2,968 2,932 Selling, general and administrative 4,313 4,383 Total $ 7,336 $ 7,359

Long-Term Obligations (Tables)

Long-Term Obligations (Tables) - 3% Convertible Senior Notes Due 2025 [Member]	3 Months Ended
	Mar. 31, 2022
Summary of Outstanding Balances of Convertible Notes	The outstanding balances of the Notes consisted of the following (in thousands): March 31, December 31, Principal $ 172,500 $ 172,500 Less: debt issuance costs ( 3,009 ) ( 3,207 ) Net carrying amount $ 169,491 $ 169,293
Schedule of Interest Expense Recognized Related to Convertible Notes	The following table sets forth total interest expense recognized related to the Notes for the periods indicated (in thousands): For the Three Months 2022 2021 Contractual interest expense $ 1,294 $ 1,294 Amortization of debt issuance costs 198 191 Total $ 1,492 $ 1,485
Summary of Future Minimum Payments on Convertible Notes	Future minimum payments on the Notes as of March 31, 2022 were as follows (in thousands): Years ended December 31, Future Minimum 2022 $ 5,175 2023 5,175 2024 5,175 2025 177,675 Total minimum payments $ 193,200 Less: interest and issuance costs ( 23,709 ) Convertible senior notes $ 169,491

Product Revenue - Summary of Pr

Product Revenue - Summary of Product Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Total product revenue, net	$ 47,670	$ 23,260
Product revenue
Gross product revenue	34,910	27,544
Provisions for product revenue	(6,610)	(5,813)
Total product revenue, net	$ 28,300	$ 21,731

Product Revenue - Additional In

Product Revenue - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Accounts receivable	$ 24,992,000	$ 22,497,000
Bad debt write-offs	0
Credit losses	0	0
Product Revenue [Member]
Disaggregation of Revenue [Line Items]
Accounts receivable	$ 21,600,000	$ 20,000,000

Inventory - Schedule of Invento

Inventory - Schedule of Inventory Current (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Inventory Disclosure [Abstract]
Raw materials	$ 2,563	$ 1,797
Work in process	926	1,895
Finished goods	385	414
Total inventory	$ 3,874	$ 4,106

License and Asset Purchase Ag_2

License and Asset Purchase Agreements - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payments receivable	$ 8.6
Reimbursement of development related expenses	7.1
Milestone method revenue recognized	8.6
Antengene [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payments receivable	7.8	$ 0.8
Promedico Ltd [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payments receivable	$ 0.8

Asset Acquisition - Additional

Asset Acquisition - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development	$ 42,062	$ 37,050

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Schedule of Financial Assets That Have Been Measured at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	$ 52,055	$ 38,156
Total	150,243	95,101
Financial liability
Embedded derivative liability	3,080	3,080
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	74,203	44,947
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	76,040	50,154
Level 3 [Member]
Financial liability
Embedded derivative liability	3,080	3,080
Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	23,985	11,998
Commercial Paper [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	23,985	11,998
U.S. government and agency securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	28,994	12,000
U.S. government and agency securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	28,994	12,000
Short-term [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	11,127	24,269
Short-term [Member] | Corporate Debt Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	11,127	24,269
Short-term [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	11,984	12,995
Short-term [Member] | Commercial Paper [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	11,984	12,995
Short-term [Member] | U.S. government and agency securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	28,944	892
Short-term [Member] | U.S. government and agency securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	28,944	892
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	45,209	32,947
Money Market Funds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 45,209	$ 32,947

Investments - Summary of Invest

Investments - Summary of Investments, Classified as Available-for-Sale (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 52,071	$ 38,161
Gross Unrealized Gains	5	4
Total Unrealized Loss	(21)	(9)
Aggregate Fair Value	52,055	38,156
Short-term [Member] | Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	11,131	24,272
Gross Unrealized Gains	3	3
Total Unrealized Loss	(7)	(6)
Aggregate Fair Value	11,127	24,269
Short-term [Member] | Commercial Paper [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	11,990	12,998
Gross Unrealized Gains		0
Total Unrealized Loss	(6)	(3)
Aggregate Fair Value	11,984	12,995
Short-term [Member] | U.S. government and agency securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	28,950	891
Gross Unrealized Gains	2	1
Total Unrealized Loss	(8)	0
Aggregate Fair Value	$ 28,944	$ 892

Investments - Additional Inform

Investments - Additional Information (Detail)	Mar. 31, 2022USD ($)Security	Dec. 31, 2021Security
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year | Security	16	37
Unrealized losses, other-than-temporary impairments | $	$ 0

Investments - Debt Securities A

Investments - Debt Securities Available-For-Sale (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Unrealized Losses, Less than 12 Months	$ (21)	$ (9)
Fair Value, Less than 12 Months	42,056	26,650
Unrealized Losses	(21)	(9)
Fair Value	42,056	26,650
Corporate Debt Securities [Member]
Unrealized Losses, Less than 12 Months	(7)	(6)
Fair Value, Less than 12 Months	8,123	16,655
Unrealized Losses	(7)	(6)
Fair Value	8,123	16,655
Commercial Paper [Member]
Unrealized Losses, Less than 12 Months	(6)	(3)
Fair Value, Less than 12 Months	11,984	9,995
Unrealized Losses	(6)	(3)
Fair Value	11,984	$ 9,995
U.S. government and agency securities [Member]
Unrealized Losses, Less than 12 Months	(8)
Fair Value, Less than 12 Months	21,949
Unrealized Losses	(8)
Fair Value	$ 21,949

Net Loss Per Share (Additional

Net Loss Per Share (Additional Information) (Details)	3 Months Ended
	Mar. 31, 2022
3% Convertible Senior Notes Due 2025 [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Notes, interest rate	3.00%

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Potentially Dilutive Securities Were Excluded From The Calculation of Diluted Net Loss Per Share Due to Their Anti-Dilutive Effect (Detail) - shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Outstanding Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities excluded from the calculation of diluted net loss per share due to anti-dilutive effect (in shares)	13,477,000	12,900,000
Unvested Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities excluded from the calculation of diluted net loss per share due to anti-dilutive effect (in shares)	3,798,000	2,517,000

Stock-based Compensation - Sche

Stock-based Compensation - Schedule of Total Stock-based Compensation Expense Recognized in Connection with All Share-based Payment Awards (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 7,336	$ 7,359
Cost of Sales [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	55	44
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	2,968	2,932
Selling,General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 4,313	$ 4,383

Stockholders' Equity - Open Mar

Stockholders' Equity - Open Market Sale Agreement - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	May 05, 2020	May 04, 2020	Aug. 17, 2018
Common Stock [Member]
Equity Offering [Line Items]
Number of shares of common stock sold in public offering	2,941,000	638,000
Jefferies LLC [Member] | Open Market Sale Agreement [Member] | Common Stock [Member]
Equity Offering [Line Items]
Number of shares of common stock sold in public offering	2,941,517	638,341
Stock Issued During Period, Value, Stock Dividend	$ 70.7
Net proceeds from sale of common stock	$ 29.3	$ 9.9
Maximum [Member] | Jefferies LLC [Member] | Open Market Sale Agreement [Member]
Equity Offering [Line Items]
Aggregate offering price			$ 175	$ 75	$ 75
Percentage of commission of gross proceeds from the sale of Shares	3.00%
Additional aggregate offering price			$ 100

Long-Term Obligations - Additio

Long-Term Obligations - Additional Information (Detail)	Oct. 15, 2022d	Sep. 30, 2019USD ($)	Mar. 31, 2022USD ($)d$ / sharesshares	Dec. 31, 2021USD ($)	Oct. 26, 2018USD ($)	Oct. 16, 2018USD ($)
Subsequent Event [Line Items]
Debt instrument convertible threshold consecutive trading days | d			5
Description of debt instrument convertible period			during the five business day period immediately after any five consecutive trading day period
Principal amount of notes used in conversion rate			$ 1,000
Debt instrument convertible threshold maximum percentage of product of last reported sale price of common stock			98.00%
Fair Value of embeded derivative liability			$ 3,080,000	$ 3,080,000
Level 3 [Member]
Subsequent Event [Line Items]
Fair Value of embeded derivative liability			3,080,000	3,080,000
Deferred Royalty Obligation [Member] | Level 3 [Member]
Subsequent Event [Line Items]
Deferred royalty obligation at fair value			129,900,000
Revenue Interest Financing Agreement [Member]
Subsequent Event [Line Items]
Debt issuance costs			$ 1,400,000
First investment amount		$ 75,000,000
Revenue Interest Financing Agreement [Member] | HealthCare Royalty Partners IV LP [Member] | Royalty Due On December 31, 2022 [Member]
Subsequent Event [Line Items]
Royalty Payable Percentage on First Investment Amount			65.00%
Revenue Interest Financing Agreement [Member] | HealthCare Royalty Partners IV LP [Member] | Royalty Due On December 31, 2024 [Member]
Subsequent Event [Line Items]
Royalty Payable Percentage on First Investment Amount			100.00%
Revenue Interest Financing Agreement [Member] | HealthCare Royalty Partners IV LP [Member] | Royalty Due On September 30, 2026 [Member]
Subsequent Event [Line Items]
Royalty Payable Percentage on First Investment Amount			100.00%
Amended Revenue Interest Agreement [Member]
Subsequent Event [Line Items]
Second investment amount			$ 60,000,000
Amended Revenue Interest Agreement [Member] | HealthCare Royalty Partners IV LP [Member] | Royalty Due On December 31, 2024 [Member]
Subsequent Event [Line Items]
Royalty Payable Percentage on Second Investment Amount			65.00%
Revenue Interest Agreement And Amended Revenue Interest Agreement [Member]
Subsequent Event [Line Items]
First investment amount			$ 135,000,000
Debt Instrument Interest Rate			16.50%
Revenue Interest Agreement And Amended Revenue Interest Agreement [Member] | HealthCare Royalty Partners IV LP [Member]
Subsequent Event [Line Items]
Aggregate Royalties Percentage			185.00%
Royalty Expense			$ 32,200
Convertible Note Offering [Member]
Subsequent Event [Line Items]
Notes converted in to common stock, amount | shares			63.0731
Notes converted in to common stock, shares			$ 1
Notes, conversion price per share | $ / shares			$ 15.85
3% Convertible Senior Notes Due 2025 [Member]
Subsequent Event [Line Items]
Aggregate principal amount					$ 22,500,000	$ 150,000,000
Debt issuance costs			$ 5,600,000
Debt discount and issuance costs amortized to interest expense, amortization period			7 years
Notes, interest rate			3.00%
Notes, maturity date			Oct. 15, 2025
Principal amount of notes used in conversion rate			$ 1
Debt instrument, convertible latest date			Jun. 15, 2025
Notes conversion price, percentage			130.00%
Notes instrument, trading days | d			20
Debt instrument convertible threshold consecutive trading days | d			30
Estimated fair value of convertible notes			$ 141,900,000	$ 139,200,000
Expected life of convertible notes			7 years
Debt Instrument Interest Rate			11.85%
3% Convertible Senior Notes Due 2025 [Member] | Scenario, Forecast [Member]
Subsequent Event [Line Items]
Notes conversion price, percentage	130.00%
Notes instrument, trading days | d	20
Debt instrument convertible threshold consecutive trading days | d	30
Notes, repurchase price	100.00%

Long-Term Obligations - Summary

Long-Term Obligations - Summary of Outstanding Balances of Convertible Notes (Detail) - 3% Convertible Senior Notes Due 2025 [Member] - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Liability component:
Principal	$ 172,500	$ 172,500
Less: debt discount costs	(3,009)	(3,207)
Net carrying amount	$ 169,491	$ 169,293

Long-Term Obligations - Schedul

Long-Term Obligations - Schedule of Interest Expense Recognized Related to Convertible Notes (Detail) - 3% Convertible Senior Notes Due 2025 [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Debt Instrument [Line Items]
Contractual interest expense	$ 1,294	$ 1,294
Amortization of debt issuance costs	198	191
Total	$ 1,492	$ 1,485

Long-Term Obligations - Summa_2

Long-Term Obligations - Summary of Future Minimum Payments on Convertible Notes (Detail) - 3% Convertible Senior Notes Due 2025 [Member] $ in Thousands	Mar. 31, 2022USD ($)
Debt Instrument [Line Items]
2022	$ 5,175
2023	5,175
2024	5,175
2024	177,675
Total minimum payments	193,200
Less: interest and issuance costs	(23,709)
Convertible senior notes	$ 169,491