Aceragen (ACGN) 10-Q 14 Nov 22 2022 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2022	Nov. 14, 2022
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Sep. 30, 2022
Entity File Number	001-31918
Entity Registrant Name	IDERA PHARMACEUTICALS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-3072298
Entity Address, Address Line One	505 Eagleview Blvd., Suite 212
Entity Address, City or Town	Exton
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19341
City Area Code	484
Local Phone Number	348-1600
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	IDRA
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		62,355,434
Entity Central Index Key	0000861838
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Amendment Flag	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands		Sep. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents		$ 26,795	$ 32,545	[1]
Accounts receivable		1,964
Prepaid expenses and other current assets		1,311	1,493	[1]
Total current assets		30,070	34,038	[1]
Property and equipment, net		11	22	[1]
Intangible assets		63,067
Goodwill		9,934
Operating lease right-of-use assets		600	734	[1]
Other assets	[1]		70
Total assets		103,682	34,864	[1]
Current liabilities:
Accounts payable		6,761	565	[1]
Accrued expenses		10,691	4,088	[1]
Acquisition obligation, net		1,534
Operating lease liability		245	209	[1]
Total current liabilities		19,231	4,862	[1]
Acquisition obligation, net		5,942
Series X preferred stock liability		20,400
Operating lease liability		380	549	[1]
Deferred tax liability		3,895
Warrant liabilities		3,750
Other liabilities		141
Total liabilities		53,739	5,411	[1]
Commitments and contingencies				[1]
Stockholders' equity:
Common stock, $0.001 par value, Authorized - 140,000 shares; Issued and outstanding - 59,018 and 52,818 at September 30, 2022 and December 31, 2021, respectively		59	53	[1]
Additional paid-in capital		768,754	764,861	[1]
Accumulated deficit		(748,045)	(735,461)	[1]
Total stockholders' equity		20,768	29,453	[1]
Total liabilities, convertible redeemable preferred stock, and stockholders' equity		103,682	34,864	[1]
Series A convertible preferred stock
Stockholders' equity:
Preferred stock, $0.01 par value, Authorized - 5,000 shares: Series A convertible preferred stock; Designated - 1,500 shares, Issued and outstanding - 1 share				[1]
Series Z convertible preferred stock
Current liabilities:
Series Z convertible redeemable preferred stock, $0.01 par value, Authorized - 150 shares: Issued and outstanding - 81 shares at September 30, 2022		$ 29,175
[1] The condensed consolidated balance sheet at December 31, 2021 has been derived from the audited financial statements at that date.

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2022	Dec. 31, 2021
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	140,000,000	140,000,000
Common stock, shares issued	59,018,000	52,818,000
Common stock, shares outstanding	59,018,000	52,818,000
Series A convertible preferred stock
Preferred stock, shares designated	1,500,000	1,500,000
Preferred stock, shares issued	1,000	1,000
Preferred stock, shares outstanding	1,000	1,000
Series Z convertible preferred stock
Temporary equity, preferred stock, par value	$ 0.01
Temporary Equity, preferred stock, shares authorized	150,000
Temporary Equity, preferred stock, shares issued	81,000
Temporary Equity, preferred stock, shares outstanding	81,000

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Government contracts revenue	$ 49		$ 49
Operating expenses:
Research and development	1,470	$ 3,507	5,960	$ 14,271
General and administrative	2,268	2,331	7,325	7,959
Acquisition-related costs	2,836		2,836
Restructuring and other costs	2,802	130	2,802	1,322
Total operating expenses	9,376	5,968	18,923	23,552
Loss from operations	(9,327)	(5,968)	(18,874)	(23,552)
Other income (expense):
Interest income	111	2	156	7
Interest expense				(7)
Warrant revaluation gain	116		116	6,983
Future tranche right revaluation gain				118,803
Foreign currency exchange and other gain (loss)	(38)	1	(21)	(24)
(Loss) income before income tax benefit	(9,138)	(5,965)	(18,623)	102,210
Income tax benefit	6,039		6,039
Net (loss) income	(3,099)	(5,965)	(12,584)	102,210
Net (loss) income applicable to common stockholders (Note 15)
- Basic	(3,099)	(5,965)	(12,584)	100,574
- Diluted	$ (3,099)	$ (5,965)	$ (12,584)	$ (23,576)
Net (loss) income per share applicable to common stockholders (Note 15)
- Basic	$ (0.06)	$ (0.11)	$ (0.24)	$ 2.10
- Diluted	$ (0.06)	$ (0.11)	$ (0.24)	$ (0.46)
Weighted-average number of common shares used in computing net (loss) income per share applicable to common stockholders
- Basic	53,286	52,740	53,052	47,990
- Diluted	53,286	52,740	53,052	51,613

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Cash Flows from Operating Activities:
Net (loss) income	$ (12,584)	$ 102,210
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Stock-based compensation	1,518	1,990
Warrant liability revaluation gain	(116)	(6,983)
Future tranche right liability revaluation gain		(118,803)
Issuance of common stock for services rendered	66	130
Accretion of discounts on short-term investments		(1)
Depreciation and amortization expense	11	17
Deferred tax benefit	(6,039)
Changes in operating assets and liabilities, net of effects from Acquisition:
Accounts receivable	(49)
Prepaid expenses and other assets	806	1,930
Accounts payable, accrued expenses, and other liabilities	4,954	(1,040)
Other	142	5
Net cash used in operating activities	(11,291)	(20,545)
Cash Flows from Investing Activities:
Cash acquired in acquisition of Aceragen	5,482
Proceeds from maturity of available-for-sale securities		4,500
Net cash provided by investing activities	5,482	4,500
Cash Flows from Financing Activities:
Proceeds from common stock financings, net		19,534
Proceeds from employee stock purchases	43	48
Proceeds from exercise of common stock options and warrants	16	271
Payments on seller-financed purchases		(435)
Net cash provided by financing activities	59	19,418
Net (decrease) increase in cash and cash equivalents	(5,750)	3,373
Cash and cash equivalent, beginning of period	32,545	33,229
Cash and cash equivalents, end of period	26,795	36,602
Supplemental disclosure of cash flow information:
Cash paid for interest		$ 5
Supplemental disclosure of non-cash financing and investing activities:
Offering costs in accounts payable and accrued expenses	$ 15

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF REDEEMABLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) shares in Thousands, $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Series B1 Preferred	Series Z preferred stock	Total
Temporary equity, Beginning balance (in shares) at Dec. 31, 2020				24
Temporary equity, Ending balance (in shares) at Mar. 31, 2021				10
Increase (Decrease) in Temporary Equity
Conversion of Series B1 preferred stock (in shares)				(14)
Beginning balance at Dec. 31, 2020	$ 38	$ 742,342	$ (833,552)			$ (91,172)
Beginning balance (in shares) at Dec. 31, 2020	38,291
Ending balance (in shares) at Mar. 31, 2021	46,537
Increase (Decrease) in Stockholders' Equity
Conversion of Series B1 preferred stock	$ 1	(1)
Conversion of Series B1 preferred stock (in shares)	1,415
Sale of common stock, net of issuance costs	$ 3	16,258				16,261
Sale of common stock, net of issuance costs (in shares)	3,195
Issuance of common stock under employee stock purchase plan		28				28
Issuance of common stock under employee stock purchase plan (in shares)	8
Issuance of common stock under equity incentive plan (vesting of restricted stock units) (in shares)	237
Issuance of common stock upon exercise of common stock options and warrants	$ 4	267				271
Issuance of common stock upon exercise of common stock options and warrants (in shares)	3,375
Issuance of common stock for services rendered		67				67
Issuance of common stock for services rendered (in shares)	16
Stock-based compensation expense		1,111				1,111
Net (loss) income			115,738			115,738
Ending balance at Mar. 31, 2021	$ 46	760,072	(717,814)			42,304
Temporary equity, Beginning balance (in shares) at Dec. 31, 2020				24
Beginning balance at Dec. 31, 2020	$ 38	742,342	(833,552)			(91,172)
Beginning balance (in shares) at Dec. 31, 2020	38,291
Ending balance (in shares) at Sep. 30, 2021	52,777
Increase (Decrease) in Stockholders' Equity
Net (loss) income						102,210
Ending balance at Sep. 30, 2021	$ 53	764,300	(731,342)			33,011
Temporary equity, Beginning balance (in shares) at Mar. 31, 2021				10
Increase (Decrease) in Temporary Equity
Conversion of Series B1 preferred stock (in shares)				(10)
Beginning balance at Mar. 31, 2021	$ 46	760,072	(717,814)			42,304
Beginning balance (in shares) at Mar. 31, 2021	46,537
Ending balance (in shares) at Jun. 30, 2021	52,115
Increase (Decrease) in Stockholders' Equity
Conversion of Series B1 preferred stock	$ 1	(1)
Conversion of Series B1 preferred stock (in shares)	953
Sale of common stock, net of issuance costs	$ 2	2,510				2,512
Sale of common stock, net of issuance costs (in shares)	2,076
Issuance of common stock under employee stock purchase plan		6				6
Issuance of common stock under employee stock purchase plan (in shares)	6
Issuance of common stock upon exercise of common stock options and warrants	$ 3	(3)
Issuance of common stock upon exercise of common stock options and warrants (in shares)	2,496
Issuance of common stock for services rendered		63				63
Issuance of common stock for services rendered (in shares)	47
Stock-based compensation expense		404				404
Net (loss) income			(7,563)			(7,563)
Ending balance at Jun. 30, 2021	$ 52	763,051	(725,377)			37,726
Ending balance (in shares) at Sep. 30, 2021	52,777
Increase (Decrease) in Stockholders' Equity
Sale of common stock and prefunded warrants, net of issuance costs	$ 1	760				761
Sale of common stock and prefunded warrants, net of issuance costs (in shares)	647
Issuance of common stock under employee stock purchase plan		14				14
Issuance of common stock under employee stock purchase plan (in shares)	15
Stock-based compensation expense		475				475
Net (loss) income			(5,965)			(5,965)
Ending balance at Sep. 30, 2021	$ 53	764,300	(731,342)			33,011
Beginning balance at Dec. 31, 2021	$ 53	764,861	(735,461)			$ 29,453	[1]
Beginning balance (in shares) at Dec. 31, 2021	52,818					52,818
Ending balance (in shares) at Mar. 31, 2022	52,924
Increase (Decrease) in Stockholders' Equity
Sale of common stock, net of issuance costs		(15)				$ (15)
Issuance of common stock under employee stock purchase plan		16				16
Issuance of common stock under employee stock purchase plan (in shares)	42
Issuance of common stock under equity incentive plan (vesting of restricted stock units) (in shares)	27
Issuance of common stock for services rendered		22				22
Issuance of common stock for services rendered (in shares)	37
Stock-based compensation expense		545				545
Net (loss) income			(4,178)			(4,178)
Ending balance at Mar. 31, 2022	$ 53	765,429	(739,639)			25,843
Temporary equity, Ending balance (in shares) at Sep. 30, 2022					81
Temporary equity, Ending balance at Sep. 30, 2022					$ 29,175
Beginning balance at Dec. 31, 2021	$ 53	764,861	(735,461)			$ 29,453	[1]
Beginning balance (in shares) at Dec. 31, 2021	52,818					52,818
Ending balance (in shares) at Sep. 30, 2022	59,018					59,018
Increase (Decrease) in Stockholders' Equity
Net (loss) income						$ (12,584)
Ending balance at Sep. 30, 2022	$ 59	768,754	(748,045)			20,768
Beginning balance at Mar. 31, 2022	$ 53	765,429	(739,639)			25,843
Beginning balance (in shares) at Mar. 31, 2022	52,924
Ending balance (in shares) at Jun. 30, 2022	52,999
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under employee stock purchase plan		12				12
Issuance of common stock under employee stock purchase plan (in shares)	34
Issuance of common stock for services rendered		22				22
Issuance of common stock for services rendered (in shares)	41
Stock-based compensation expense		562				562
Net (loss) income			(5,307)			(5,307)
Ending balance at Jun. 30, 2022	$ 53	766,025	(744,946)			$ 21,132
Temporary equity, Ending balance (in shares) at Sep. 30, 2022					81
Increase (Decrease) in Temporary Equity
Issuance of preferred stock upon Acquisition of Aceragen					$ 29,175
Issuance of preferred stock upon Acquisition of Aceragen (in shares)					81
Temporary equity, Ending balance at Sep. 30, 2022					$ 29,175
Ending balance (in shares) at Sep. 30, 2022	59,018					59,018
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under employee stock purchase plan		15				$ 15
Issuance of common stock under employee stock purchase plan (in shares)	36
Issuance of common stock upon exercise of common stock options and warrants	$ 2	14				16
Issuance of common stock upon exercise of common stock options and warrants (in shares)	1,533
Issuance of common stock for services rendered		22				22
Issuance of common stock for services rendered (in shares)	50
Stock-based compensation expense		411				411
Issuance of common stock upon Acquisition of Aceragen	$ 4	2,267				2,271
Issuance of common stock upon Acquisition of Aceragen (in shares)	4,399
Net (loss) income			(3,099)			(3,099)
Ending balance at Sep. 30, 2022	$ 59	$ 768,754	$ (748,045)			$ 20,768
[1] The condensed consolidated balance sheet at December 31, 2021 has been derived from the audited financial statements at that date.

Business and Organization

Business and Organization	9 Months Ended
	Sep. 30, 2022
Business and Organization
Business and Organization	Note 1. Business and Organization ​ Business Overview ​ Idera Pharmaceuticals, Inc. (“Idera” or the “Company”), a Delaware corporation, is a biopharmaceutical company with a business strategy focused on the clinical development, and ultimately the commercialization, of drug candidates for rare disease indications characterized by small, well-defined patient populations with significant unmet medical needs. The Company’s strategic focus has been to identify and acquire rights to novel development and commercial stage rare disease programs through business development opportunities, including additional strategic alternatives. In these notes, the terms “we,” “our,” “our company” and “us” may refer, as the context requires, to Idera or collectively to Idera and its subsidiaries. ​ On September 28, 2022, the Company acquired Aceragen, Inc. (“Aceragen”), a Delaware corporation and its wholly owned subsidiaries. Aceragen is a privately-held biotechnology company addressing severe, rare, and orphan pulmonary and rheumatic diseases for which there are limited or no available treatments. The Company acquired Aceragen as a strategic extension of its rare disease business and focus with the primary objective of further developing Aceragen’s portfolio of rare disease product candidates. Specifically, as a result of the Acquisition (as defined below), the Company will focus on developing ACG-701 to treat pulmonary exacerbations associated with cystic fibrosis and melioidosis, a severe, life-threatening infection, and ACG-801 to treat a rare lysosomal storage disorder known as Farber disease. For additional information on the Acquisition of Aceragen, see Note 4. ​ Tilsotolimod Update ​ Until December 2021, the Company was developing tilsotolimod, via intratumoral injection, for the treatment of solid tumors in combination with nivolumab, an anti-PD1 antibody marketed as Opdivo® by Bristol Myers Squibb Company (“BMS”), and/or ipilimumab, an anti-CTLA4 antibody marketed as Yervoy® by BMS. Due to Phase 3 results in anti-PD-1 refractory advanced melanoma, reported in March 2021, which showed the study failed to meet its primary endpoint, as well as a decision in December 2021 to discontinue enrollment in ILLUMINATE-206, the Company’s Phase 2 study in solid tumors, Company-sponsored development of tilsotolimod has been discontinued. ​ Although clinical trials with tilsotolimod have not yet translated into a new treatment alternative for patients, the Company believes that data supporting tilsotolimod’s mechanism of action and encouraging safety profile from across the array of pre-clinical and clinical work to date, together with its intellectual property protection, are noteworthy. As a result, in December 2021, the Company announced it would consider, and continues to consider, additional development opportunities for the compound in alignment with the Company’s rare disease business and/or out-licensing arrangements such that tilsotolimod’s full potential might continue to be explored on behalf of patients. ​ Nasdaq Compliance ​ As previously disclosed in the Current Report on Form 8-K filed with the SEC on December 1, 2021, on November 26, 2021, Idera received a deficiency letter from the Nasdaq Listing Qualifications Department (the “Staff”) of The Nasdaq Stock Market, LLC (“Nasdaq”), notifying the Company that it is not in compliance with Nasdaq Listing Rule 5550(a)(2), which requires the Company to maintain a minimum bid price of at least $1 per share for continued listing on The Nasdaq Capital Market (the “Minimum Bid Requirement”). ​ On May 26, 2022, the Company received notice (the “Nasdaq Notice”) from the Staff indicating that, while the Company has not regained compliance with the Minimum Bid Requirement, the Staff has determined that the Company is eligible for an additional 180-day period, or until November 21, 2022, to regain compliance. If at any time during this second 180-day compliance period, the closing bid price of the Company’s common stock is at least $1 per share for a minimum of ten consecutive business days, the Staff will provide the Company with written confirmation of compliance. If compliance cannot be demonstrated by November 21, 2022, the Staff will provide written notification that the Company’s common stock will be subject to delisting. The Company would then be entitled to appeal the Staff’s determination to a Nasdaq hearings panel. The Company intends to monitor the closing bid price of its common stock and consider implementing available options to regain compliance with the Minimum Bid Requirement. ​ Liquidity, Financial Condition and Consideration as a Going Concern ​ The Company has incurred substantial losses and negative cash flows from operations since its inception and has an accumulated deficit of   The Company anticipates incurring additional losses until such time, if ever, that it can generate significant sales of its product candidates currently in development. Substantial additional financing will be needed by the Company to fund its operations and to commercially develop its product candidates. Management is currently evaluating different strategies to obtain the required funding for future operations. These strategies may include, but are not limited to: private placements of equity and/or debt, payments from potential strategic research and development, licensing and/or marketing arrangements with pharmaceutical companies, and public offerings of equity and/or debt securities. There can be no assurance that these future funding efforts will be successful.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2022
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	Note 2. Summary of Significant Accounting Policies ​ Basis of Presentation ​ The unaudited interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All material intercompany balances and transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) for interim financial information and the instructions to Form 10-Q. Accordingly, certain information and footnote disclosures normally included in consolidated financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. In the opinion of management, all adjustments, consisting of normal recurring adjustments, and disclosures considered necessary for a fair presentation of interim period results have been included. Interim results for the nine months ended September 30, 2022 are not necessarily indicative of results that may be expected for the year ending December 31, 2022. For further information, refer to the consolidated financial statements and footnotes thereto included in the Company’s 2021 Form 10-K. ​ Use of Estimates ​ The preparation of the Company’s unaudited condensed consolidated financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the unaudited condensed consolidated financial statements and reported amounts of revenues and expenses during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances and are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from these estimates. ​ Cash and Cash Equivalents ​ The Company considers all highly liquid investments with maturities of 90 days or less when purchased to be cash equivalents. Cash and cash equivalents at September 30, 2022 and December 31, 2021 consisted of cash and money market funds. ​ Financial Instruments ​ At September 30, 2022 and December 31, 2021, the Company’s financial instruments included accounts payable, accrued expenses, stockholder notes and debt. The carrying amount of cash and cash equivalents, accounts receivable, accounts payable and accrued expenses approximates fair value due to the short-term maturities of these instruments. Each of the carrying values of the preferred stock warrant liabilities and Series X preferred stock liability issued to Aceragen stockholders and the acquisition obligation assumed in connection with the Acquisition of Aceragen are recorded at their estimated fair values. As of September 30, 2022, the Company did not have any derivatives, hedging instruments or other similar financial instruments. ​ Accounts Receivable ​ Accounts receivables are recorded net of an estimated expected credit losses. The Company’s measurement of expected credit losses is based on relevant information about past events, including historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. To date, there have been no expected credit losses as the Company’s customer is the U.S. government. Unbilled accounts receivable at September 30, 2022 which is included in accounts receivables is $1.1 million and relates to revenue recognized for work that has been performed but the invoicing has not yet occurred. ​ Foreign Currency ​ Upon completion of the Acquisition of Aceragen in September 2022, the Company has a wholly-owned subsidiary in Switzerland and the functional currency is the Swiss Franc. The results of the Company’s non-US dollar based functional currency operations are translated to US dollars at the average exchange rates during the period. Assets and liabilities are translated at the exchange rate prevailing at the balance sheet date. Equity is translated at the prevailing exchange rate at the date of the equity transaction. Translation adjustments are included in stockholders' equity, as a component of accumulated other comprehensive income. ​ The Company realizes foreign currency transaction gains (losses) in the normal course of business based on movements in the applicable exchange rates. These gains (losses) are included as a component of other (expense) income, net. ​ Business Combinations ​ The Company evaluates acquisitions of assets and other similar transactions to assess whether or not the transaction should be accounted for as a business combination or asset acquisition by first applying a screen to determine if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets. If the screen is met, the transaction is accounted for as an asset acquisition. If the screen is not met, further determination is required as to whether or not the Company has acquired inputs and processes that have the ability to create outputs, which would meet the requirements of a business. If determined to be a business combination, the Company accounts for the transaction under the acquisition method of accounting as indicated in Accounting Standard Update (“ASU”) 2017-01, Business Combinations ​ Goodwill ​ Goodwill represents the amount of consideration paid in excess of the fair value of net assets acquired as a result of the Company’s business acquisitions accounted for using the acquisition method of accounting. The intangible assets acquired represented the fair value of in-process research and development (IPR&D) which has been recorded on the accompanying condensed consolidated balance sheet as indefinite-lived intangible assets. A deferred tax liability was recorded for the difference between the fair value of the acquired IPR&D and its tax basis which was recognized as goodwill in applying the purchase method of accounting. Goodwill is not amortized and is subject to impairment testing at a reporting unit level on an annual basis or when a triggering event occurs that may indicate the carrying value of the goodwill is impaired. An entity is permitted to first assess qualitative factors to determine if a quantitative impairment test is necessary. Further testing is only required if the entity determines, based on the qualitative assessment, that it is more likely than not that the fair value of the reporting unit is less than its carrying amount. ​ We evaluate goodwill for impairment at least annually on October 1 and whenever facts and circumstances indicate that their carrying amounts may not be recoverable. For the nine months ended September 30, 2022, the Company determined that there was no impairment to goodwill. ​ Indefinite-Lived Intangible Assets ​ Indefinite-lived intangible assets consist of In-Process Research and Development(“IPR&D”). The fair values of IPR&D project assets acquired in business combinations are capitalized. The Company generally utilizes the Multi-Period Excess Earning Method to determine the estimated fair value of the IPR&D assets acquired in a business combination. The projections used in this valuation approach are based on many factors, such as relevant market size and share, probabilities of success, anticipated patent protection, and expected pricing. The estimated future net cash flows are then discounted to the present value using an appropriate discount rate. These assets are treated as indefinite-lived intangible assets until completion or abandonment of the projects, at which time the assets are amortized over the remaining useful life or written off, as appropriate. ​ Intangible assets with indefinite lives, including IPR&D, are tested for impairment if impairment indicators arise and, at a minimum, annually. However, an entity is permitted to first assess qualitative factors to determine if a quantitative impairment test is necessary. Further testing is only required if the entity determines, based on the qualitative assessment, that it is more likely than not that an indefinite-lived intangible asset’s fair value is less than its carrying amount. Otherwise, no further impairment testing is required. The indefinite-lived intangible asset impairment test consists of a one-step analysis that compares the fair value of the intangible asset with its carrying amount. If the carrying amount of an intangible asset exceeds its fair value, an impairment loss is recognized in an amount equal to that excess. We consider many factors in evaluating whether the value of our intangible assets with indefinite lives may not be recoverable, including, but not limited to, expected growth rates, the cost of equity and debt capital, general economic conditions, our outlook and market performance of our industry and recent and forecasted financial performance. ​ We evaluate indefinite-lived intangible assets for impairment at least annually on October 1 and whenever facts and circumstances indicate that their carrying amounts may not be recoverable. For the nine months ended September 30, 2022, the Company determined that there was no impairment to IPR&D . ​ Concentration of Credit Risk ​ Financial instruments that subject the Company to credit risk primarily consist of cash and cash equivalents. The Company’s credit risk is managed by investing in highly rated money market instruments, U.S. treasury bills, corporate bonds, commercial paper and/or other debt securities. Due to these factors, no significant additional credit risk is believed by management to be inherent in the Company’s assets. As of September 30, 2022, all the Company’s cash and cash equivalents were held at five high credit-quality financial institutions. ​ Operating Lease Right-of-Use Assets and Lease Liability ​ The Company accounts for leases under ASC 842, Leases. Operating leases are included in “Operating lease right-of-use assets” within the Company’s consolidated balance sheets and represent the Company’s right to use an underlying asset for the lease term. The Company’s related obligation to make lease payments are included in “Operating lease liability” and “Operating lease liability, net of current portion” within the Company’s consolidated balance sheets. Operating lease right-of-use (“ROU”) assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rates, which are the rates incurred to borrow on a collateralized basis over a similar term, an amount equal to the lease payments in a similar economic environment. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The ROU assets are tested for impairment according to ASC 360, Property, Plant, and Equipmen ​ As of September 30, 2022 and December 31, 2021, the Company’s operating lease ROU assets and corresponding short-term and long-term lease liabilities primarily relate to its existing Exton, PA facility operating lease which expires on May 31, 2025. In connection with the Aceragen Acquisition, as defined and described in Note 4, the Company acquired an operating lease for an office in Basel, Switzerland which expires on March 31, 2023. ​ Acquisition-Related Costs ​ Acquisition-related costs include direct expenses incurred in connection with the Acquisition of Aceragen as well as integration-related professional fees and other incremental costs directly associated to the acquisition. ​ Restructuring and Other Charges ​ The Company accounts for exit or disposal activities in accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 420, Exit or Disposal Cost Obligations (“ASC 420”). A business restructuring is defined as an exit or disposal activity that includes, but is not limited to, a program that is planned and controlled by management and materially changes either the scope of a business or the manner in which that business is conducted. Business restructuring charges include (i) one-time termination benefits related to employee separations (i.e. severance costs), (ii) contract termination costs, and (iii) other related costs associated with exit or disposal activities. In the third quarter of 2022, the Company implemented a restructuring plan to streamline the organization, reduce costs, and direct resources to advance the Company’s primary operating goals. ​ The Company recognizes and measures a liability for one-time termination benefits, for which no future service is required, once the plan of termination meets all of the following criteria for an established communication date: (i) management commits to a plan of termination, (ii) the plan identifies the number of employees to be terminated and their job classifications or functions, locations and the expected completion date, (iii) the plan establishes the terms of the benefit arrangement, and (iv) it is unlikely that significant changes to the plan will be made or the plan will be withdrawn. For one-time termination benefits for which future service is required, a liability is measured at the communication date based on its value as of the termination date and recognized ratably over the future service period. The Company recognizes and measures a liability for other related costs in the period in which the liability is incurred. ​ Series X Preferred Stock Liability ​ In conjunction with the Acquisition of Aceragen, the Company evaluated the newly issued Series X preferred stock and determined its revised terms represents a sale of future revenues and is classified as a liability under ASC 470, Debt and the Company has elected to account for the Series X preferred stock liability under the fair value option. The fair value of the Series X preferred stock liability represents the present value of estimated future payments, including royalty payments, as well as estimated payments that are contingent upon the achievement of specified milestones. The fair value of the Series X preferred stock liability is based on the cumulative probability of the various estimated payments. The fair value measurement is based on significant Level 3 unobservable inputs such as the probability of achieving the milestones, anticipated timelines, probability and timing of an early redemption of all obligations under Series X preferred liability and the discount rate. Any changes in the fair value of the liability in each reporting period are recognized in the consolidated statement of operations until it is settled. ​ Warrant Liability ​ In connection with the Aceragen Acquisition, a portion of the consideration paid to Aceragen warrant holders was in the form of warrants to purchase shares of Series Z (the “Series Z warrants”). The Series Z warrants were classified as a liability on the condensed consolidated balance sheet at September 30, 2022 because the underlying Series Z are contingently redeemable. The fair value of the Series Z warrants on the date of issuance was recorded as a component to the carrying value of the shares Series Z and as a long-term liability in the condensed consolidated balance sheet. The warrants are remeasured to fair value at each balance sheet date until the warrants are exercised, reclassified, expire or otherwise settled. Changes in the fair values of the Series Z warrants are recognized as other income or expense in the consolidated statements of operations and comprehensive loss. ​ The Company used the Black-Scholes option pricing model, which incorporated assumptions and estimates, to value the Series Z warrants. Estimates and assumptions impacting the fair value measurement of the Series Z warrants included the remaining contractual term of the warrants, risk-free interest rate, expected dividend yield and expected volatility of the price of the underlying shares of Series Z. The estimated the expected stock volatility based on the Company’s historical volatility for a term equal to the remaining contractual term of the warrants at the time of issuance and again at the remeasurement date. The risk-free interest rate was determined by reference to the US Treasury yield curve for time periods approximately equal to the remaining contractual term of the warrants. Expected dividend yield was determined based on the fact that the Company had never paid cash dividends and did not expect to pay any cash dividends in the foreseeable future. ​ R edeemable Preferred Stock ​ The Company applies ASC 480 when determining the classification and measurement of its preferred stock. Preferred shares subject to mandatory redemption are classified as liability instruments and are measured at fair value. Conditionally redeemable preferred shares (including preferred shares that feature redemption rights that are either within the control of the holder or subject to redemption upon the occurrence of uncertain events not solely within the Company’s control) are classified as temporary equity. At all other times, preferred shares are classified as stockholders’ equity. ​ The carrying value of the shares of Series Z is accreted to redemption value using the estimated fair value of the redemption value at each reporting period until the redeemable convertible preferred stock cease to be outstanding or the redemption right has expired. ​ The accretion for the three and nine months ended September 30, 2022 was immaterial. ​ Revenue Recognition ​ The Company recognizes revenue when the Company's customers obtain control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services by analyzing the following five steps: (i) identify the contract with a customer(s); (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. ​ Revenues from reimbursable contracts are recognized as costs are incurred, generally based on allowable direct costs incurred during the period, plus allocable overheads together with any recognizable earned fee. The Company uses this input method to measure progress as the customer has access to the development research under these projects and benefits incrementally as R&D activities occur. ​ Income Taxes ​ In accordance with ASC 270, Interim Reporting Income Taxes ​ ​ New Accounting Pronouncements ​ From time to time, new accounting pronouncements are issued by the FASB and rules are issued by the SEC that the Company has or will adopt as of a specified date. Unless otherwise noted, management does not believe that any other recently issued accounting pronouncements issued by the FASB or guidance issued by the SEC had, or is expected to have, a material impact on the Company’s present or future consolidated financial statements. ​ Recently Adopted Accounting Pronouncements 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 (“ASU 2020-06”), which simplifies the guidance on an issuer’s accounting for convertible instruments and contracts in its own equity. The Company adopted ASU 2020-06 in the first quarter of 2021. The adoption of ASU 2020-06 did not have a material effect on the Company’s consolidated financial statements.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2022
Fair Value Measurements
Fair Value Measurements	Note 3. Fair Value Measurements ​ Assets and Liabilities Measured at Fair Value on a Recurring Basis ​ The Company applies the guidance in ASC 820, Fair Value Measurement ​ ​ ​ The Company uses a fair value hierarchy, which distinguishes between assumptions based on market data (observable inputs) and an entity's own assumptions (unobservable inputs). The guidance requires that fair value measurements be classified and disclosed in one of the following three categories: ● Level 1: Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities; ● Level 2: Quoted prices in markets that are not active or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability; or ● Level 3: Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). ​ Determining which category an asset or liability falls within the hierarchy requires significant judgment. The Company evaluates its hierarchy disclosures each reporting period. There were no transfers between Level 1 , 2 , and 3 during the nine months ended September 30, 2022. ​ The table below presents the assets and liabilities measured and recorded in the condensed consolidated financial statements at fair value on a recurring basis at September 30, 2022 and December 31, 2021 categorized by the level of inputs used in the valuation of each asset and liability. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2022 (In thousands) ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 4,680 ​ $ 4,680 ​ $ — ​ $ — ​ Cash equivalents – money market funds ​ ​ 22,115 ​ ​ 22,115 ​ ​ — ​ ​ — ​ Total assets ​ $ 26,795 ​ $ 26,795 ​ $ — ​ $ — ​ Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Warrant liability ​ $ 3,750 ​ $ — ​ $ — ​ $ 3,750 ​ Series X preferred stock liability ​ ​ 20,400 ​ ​ — ​ ​ — ​ ​ 20,400 ​ Total liabilities ​ $ 24,150 ​ $ — ​ $ — ​ $ 24,150 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2021 ​ (In thousands) ​ Total ​ Level 1 ​ Level 2 ​ Level 3 ​ Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 250 ​ $ 250 ​ $ — ​ $ — ​ Cash equivalents – money market funds ​ ​ 32,295 ​ ​ 32,295 ​ ​ — ​ ​ — ​ Total assets ​ $ 32,545 ​ $ 32,545 ​ $ — ​ $ — ​ ​ The Level 1 assets consist of money market funds, which are actively traded daily. ​ There was no significant change in the fair value of the Series X preferred stock liability from the date of issuance on September 28,2022 to September 30, 2022. A reconciliation of the change in the fair value of the warrant liability for the three and nine months ended September 30, 2022 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (In thousands) ​ ​ Balance, December 31, 2021 $ — Issuance in connection with Acquisition of Aceragen ​ ​ 3,866 Change in fair value ​ ​ (116) Balance, September 30, 2022 $ 3,750 ​ ​ The fair value of the Series X preferred stock represents the present value of estimated future payments, including royalty payments, as well as estimated payments that are contingent upon the achievement of specified milestones. The fair value of the Series X preferred stock liability is based on the cumulative probability of the various estimated payments. The fair value measurement is based on significant Level 3 unobservable inputs such as the probability of achieving the milestones, anticipated timelines, probability and timing of an early redemption of all obligations under the agreement and discount rate. Any changes in the fair value of the liability are recognized in the consolidated statement of operations until it is settled.

Business Acquisition

Business Acquisition	9 Months Ended
	Sep. 30, 2022
Business Acquisition
Business Acquisition	Note 4. Business Acquisition On September 28, 2022, in accordance with the terms of an Agreement and Plan of Merger (the “Merger Agreement”), the Company acquired 100% of the outstanding security interests of Aceragen in a “stock-for-stock” transaction whereby all Aceragen outstanding equity interests were exchanged for a combination of shares of Idera common stock, shares of Series Z, and shares of the newly designated Series X non-voting preferred stock, par value $0.01 per share (the “Series X) (such acquisition, the “Aceragen Acquisition”, “of the Acquisition”). Under the terms of the Merger Agreement, Aceragen stockholders received (i) 4,398,762 shares of the Company’s common stock, (ii) 80,656 shares of Series Z and (iii) five shares of Series X. In addition, all outstanding restricted shares subject to repurchase, options and warrants to purchase Aceragen common stock were converted into restricted shares, stock options and warrants to purchase shares of the Company’s common stock and Series Z on terms substantially identical to those in effect prior to the Aceragen Acquisition, except for adjustments to the underlying number of shares and the exercise price based on the Merger Agreement exchange ratio. Subject to stockholder approval of the conversion and an increase in authorized shares and certain beneficial ownership limitations set by each holder, each share of Series Z will automatically convert into 1,000 shares of common stock. Holders of shares of Series X are entitled to receive distributions on shares of Series X. The Acquisition was unanimously approved by the Board of Directors of the Company and the Board of Directors of Aceragen. The closing of the transaction was not subject to the approval of the Company’s stockholders. Pursuant to the Merger Agreement, the Company has agreed to hold a stockholders’ meeting (the “Special Meeting”) to submit certain matters to its stockholders for their consideration, including: (i) the approval of the conversion of the Series Z preferred stock into shares of common stock in accordance with Nasdaq Listing Rule 5635(a) (the “Conversion Proposal”) and (ii) the approval to effect a reverse stock split of all of the Company’s issued and outstanding shares of common stock (the “Reverse Stock Split Proposal” and, together with the Conversion Proposal, the “Merger Agreement Meeting Proposals”). In accordance with the Term Sheet (as defined below), the Company will also ask its stockholders at the Special Meeting to consider approving the issuance of common stock in connection with certain Convertible Notes (as defined below) that the Company expects to issue to certain former stockholders of Arrevus, Inc. In connection with these matters, the Company intends to file with the SEC a proxy statement and other relevant materials. The Company’s transaction costs of $2.8 million were expensed as incurred and included in the “Acquisition-related costs” financial statement line item in the Company’s condensed consolidated statement of operations. The transaction was accounted for under the acquisition method of accounting. Under the acquisition method, the total purchase price of the acquisition is allocated to the net tangible and identifiable intangible assets acquired and liabilities assumed based on the fair values as of the date of the acquisition. The preliminary fair value of the consideration totaled approximately $55.7 million, summarized as follows: ​ ​ ​ ​ ​ (In thousands) ​ Common stock issued to Aceragen stockholders ​ $ 1,672 Series Z issued to Aceragen stockholders (Note 9) ​ 26,971 Series X liability in connection with Aceragen Acquisition (Note 8) ​ ​ 20,400 Stock options, restricted stock and warrants allocated to consideration paid ​ 6,670 Total Consideration paid ​ $ 55,713 ​ The Company recorded the assets acquired and liabilities assumed as of the date of the acquisition based on the information available at that date. The following table presents the preliminary allocation of the purchase price to the estimated fair values of the assets acquired and liabilities assumed as of the acquisition date: ​ ​ ​ ​ ​ (In thousands) ​ ​ ​ Assets acquired: ​ ​ ​ Cash, cash equivalents and restricted cash ​ $ 5,482 Receivables ​ 1,914 Prepaid expenses and other assets ​ ​ 575 In-process research and development assets ​ 63,067 Goodwill ​ 9,934 ​ ​ $ 80,972 Liabilities assumed: ​ ​ ​ Accounts Payable and accrued expenses ​ $ 7,827 Acquisition Obligation (Note 7) ​ 7,476 Operating lease liabilities ​ ​ 22 Deferred tax liabilities ​ ​ 9,934 ​ ​ $ 25,259 ​ ​ ​ ​ Net assets acquired ​ $ 55,713 ​ The above allocation of the purchase price is based upon certain preliminary valuations and other analyses that have not been completed as of the date of this filing. Any changes in the estimated fair values of the net assets recorded for this business combination upon the finalization of more detailed analyses of the facts and circumstances that existed at the date of the transaction will change the allocation of the purchase price. As such, the purchase price allocations for the Acquisition are preliminary estimates, which are subject to change within the measurement period. The fair value of IPR&D was capitalized as of the Acquisition date and accounted for as indefinite-lived intangible assets until completion or disposition of the assets or abandonment of the associated research and development efforts. Upon successful completion of the development efforts, the useful lives of the IPR&D assets will be determined based on the anticipated period of regulatory exclusivity and will be amortized within operating expenses. Until that time, the IPR&D assets will be subject to impairment testing and will not be amortized. The goodwill recorded related to the acquisition is the excess of the fair value of the consideration transferred by the acquirer over the fair value of the net identifiable assets acquired and liabilities assumed at the date of acquisition. The goodwill recorded is not deductible for tax purposes. ​ Pro Forma Financial Information The following unaudited pro forma financial information reflects the consolidated results of operations of the Company as if the Acquisition of Aceragen had taken place on January 1, 2021. The pro forma financial information is not necessarily indicative of the results of operations as they would have been had the transactions been effected on the assumed date. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ Nine Months Ended (In thousands) ​ September 30, ​ ​ September 30, ​ 2022 ​ 2021 ​ 2022 ​ 2021 Net revenues ​ $ 3,865 ​ $ 79 ​ $ 13,334 ​ $ 79 Net (loss) income ​ $ (10,229) ​ $ (2,982) ​ $ (27,646) ​ $ 100,723 ​ ​ Nonrecurring pro forma transaction costs directly attributable to the acquisition were $7.8 million and $0 for the three and nine months ended September 30, 2022 and 2021, respectively, have been deducted from the net loss presented above. The costs deducted included a success fee of $3.4 million to be paid to a financial advisor following the closing of the Acquisition. Additionally, the Company incurred $0.8 million in retention costs as a result of stay bonuses to employees immediately following the closing of the Acquisition. The Company also incurred $2.8 million restructuring costs related to the 2022 reduction-in-workforce. These costs are excluded from the pro forma financial information for the three and nine months ended September 30, 2022. In addition, the Company recognized the $6.0 million income tax benefit for the three and nine months ended September 30, 2021 as if the transaction was completed on January 1, 2021.

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2022
Property and Equipment
Property and Equipment	Note 5. Property and Equipment ​ At September 30, 2022 and December 31, 2021, property and equipment, net, consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ (In thousands) 2022 2021 Leasehold improvements ​ $ 107 ​ $ 107 ​ Equipment and other ​ 712 ​ 712 ​ Total property and equipment, at cost ​ $ 819 ​ $ 819 ​ Less: Accumulated depreciation and amortization ​ 808 ​ 797 ​ Property and equipment, net ​ $ 11 ​ $ 22 ​ ​ ​ Depreciation and amortization expense on property and equipment was less than $0.1 million for each of the three and nine months ended September 30, 2022 and 2021. Additionally, there were

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2022
Accrued Expenses
Accrued Expenses	Note 6. Accrued Expenses ​ At September 30, 2022 and December 31, 2021, accrued expenses consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, (In thousands) ​ 2022 2021 Payroll and related costs ​ $ 1,467 ​ $ 477 ​ Clinical and nonclinical trial expenses ​ 2,289 ​ 2,909 ​ Professional and consulting fees ​ 1,216 ​ 591 ​ Restructuring and other costs (Note 12) ​ 2,660 ​ — ​ Acquisition-related costs ​ ​ 2,826 ​ ​ — ​ Other ​ 233 ​ 111 ​ Total accrued expenses ​ $ 10,691 ​ $ 4,088 ​ ​

Acquisition Obligation

Acquisition Obligation	9 Months Ended
	Sep. 30, 2022
Acquisition Obligation
Acquisition Obligation	Note 7 . Acquisition Obligation ​ As a result of the Aceragen Acquisition, the Company assumed an obligation pursuant to the Arrevus Merger Agreement (as defined below), Aceragen is obligated to make an aggregate future payment of $7.5 million to the former stockholders Arrevus, Inc., $6.0 million and $1.5 million of which was originally due in October 2022 and January 2023, respectively. The estimated fair value of the acquisition obligation at the Aceragen acquisition date was $7.5 million. The Company imputes interest expense using the effective interest method and based on the difference between the estimated fair value and the notional value. Interest expense for the three and nine months ended September 30, 2022 was immaterial. ​ In connection with the closing of the Acquisition of Aceragen, Aceragen entered into a binding term sheet (the “Term Sheet”) with the representative of certain former stockholders of Arrevus, Inc. (the “Former Stockholders”), pursuant to which Aceragen and the Former Stockholders agreed to defer certain payments owed by Aceragen to the Former Stockholders under that certain Agreement and Plan of Merger, dated October 18, 2021, by and among Aceragen, Arrevus, Inc., and their respective affiliates (the “Arrevus Merger Agreement”), in an aggregate amount of $6.0 million (the “Deferred Payments”) until October 24, 2023. The Deferred Payments will bear annual interest at 12%, paid quarterly beginning on April 1, 2023. Aceragen may prepay the Deferred Payments at any time, subject to payment in full in cash of the Deferred Payments, plus accrued interest up until the date of such prepayment. Any prepayment of the Deferred Payments must be made on a pro-rata basis among the holders of the Convertible Notes (as defined below) in proportion to their respective shares of the Deferred Payments; provided that prior to any such prepayment, the holder of each Convertible Note shall be given written notice thereof and the option to convert the principal balance into shares of common stock pursuant to the terms of the Convertible Note. ​ The Term Sheet provides that the Deferred Payments will be memorialized in an unsecured promissory note to be issued by the Company, pursuant to which each Former Stockholder will have the right to convert such Former Stockholder’s portion of its right to receive the Deferred Payments into shares of common stock (the “Convertible Notes”), provided that issuance of any common stock in a subsequent conversion is expressly contingent on approval by the Company’s stockholders of the issuance of the common stock underlying the Convertible Notes, which shall be contingent on approval of the Charter Amendment Proposal and the Reverse Stock Split Proposal by the Company’s stockholders at the Special Meeting. The Term Sheet further provides that the Company will provide customary registration rights for such converted common stock. Aceragen, the Company, and the Former Stockholder expect to enter into definitive agreements with respect to the Convertible Notes as soon as practicable, which definitive agreements are expected to replace and supersede the Term Sheet ​ Future principal payments as of September 30, 2022 are as follows: ​ ​ ​ ​ ​ (In thousands) Amounts 2022 ​ $ 1,534 2023 ​ ​ 5,942 Total ​ $ 7,476 ​

Series X Preferred Stock Liabil

Series X Preferred Stock Liability	9 Months Ended
	Sep. 30, 2022
Series X Preferred Stock Liability
Series X Preferred Stock Liability	Note 8. Series X Preferred Stock Liability ​ In connection with the Acquisition of Aceragen, the Company issued five shares of its Series X. The Series X shares are non-convertible and non-voting and are entitled to discrete development and commercial milestone payments as well as royalty payments on net product sales of ACG-801 for Farber disease. The royalty rates range between low single digits to low double digits and expire, unless terminated earlier, upon the later of the expiration of the last valid claim in the licensed patent rights in such country covering such product and the expiration of data exclusivity in such country for such product. In addition, the payments due to the holders of the Series X shares are secured by substantially all of the assets related to ACG-801. the underlying products related to ACG-801. ​ The Company concluded the Series X shares do not represent a residual interest in the Company and are accounted for as debt. The liabilities associated with the Series X shares require the Company to make certain estimates and assumptions, particularly about the achievement of future development and regulatory milestones and future product sales. Such estimates and assumptions are utilized in determining the expected repayment term, accretion of interest expense and classification between current and long-term portions of amounts outstanding. The Company elected to carry the Series X preferred stock liability at fair value, and the debt instrument is outside the scope of ASC 480, Distinguishing Liabilities from Equity, and thus will be classified as a liability under ASC 470, Debt, in the Company’s condensed consolidated financial statements. The fair value of the Series X represents the present value of estimated future payments, including royalty payments, as well as estimated payments that are contingent upon the achievement of specified milestones. The fair value of the Series X Preferred Stock Liability is based on the cumulative probability of the various estimated payments. The fair value measurement is based on significant Level 3 unobservable inputs such as the probability of achieving the milestones, anticipated timelines, probability and timing of an early redemption of all obligations under the agreement and discount rate. Any changes in the fair value of the liability are recognized in the consolidated statement of operations until it is settled. ​

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	9 Months Ended
	Sep. 30, 2022
Redeemable Convertible Preferred Stock
Redeemable Convertible Preferred Stock	Note 9. Redeemable Convertible Preferred Stock ​ December 2019 Private Placement ​ On December 23, 2019, the Company entered into the December 2019 Securities Purchase Agreement, under which the Company sold 23,684 shares of Series B1 convertible preferred stock (“Series B1 Preferred Stock”) and warrants to purchase 2,368,400 shares of the Company’s common stock at an exercise price of $1.52 per share (or, if the holder elected to exercise the warrants for shares of Series B1 Preferred Stock, 23,684 shares of Series B1 Preferred Stock at an exercise price of $152 per share) for aggregate gross proceeds of $3.9 million (the “Initial Closing”). In addition, the Company agreed to sell to the purchasers, at their option and subject to certain conditions, (i) 98,685 shares of Series B2 convertible preferred stock (“Series B2 Preferred Stock”) and 9,868,500 warrants to purchase common stock at an exercise price of $1.52 per share (or, at the election of the holder, 98,685 shares of Series B2 Preferred Stock at an price of $152 per share), for aggregate gross proceeds of $15 million (the “Series B2 Tranche”), (ii) 82,418 shares of Series B3 convertible preferred stock (“Series B3 Preferred Stock”) and 6,593,440 warrants to purchase common stock at an exercise price of $1.82 per share (or, at the election of the holder, 65,934 shares of Series B3 Preferred Stock at a price of $182 per share), for aggregate gross proceeds of $15 million (the “Series B3 Tranche”), and (iii) 82,418 shares of Series B4 convertible preferred stock (“Series B4 Preferred Stock”) and 6,593,440 warrants to purchase common stock at an exercise price of $1.82 per share (or, at the election of the holder, 65,934 shares of Series B3 Preferred Stock at a price of $182 per share), for aggregate gross proceeds of $15 million (the “Series B4 Tranche”) over a period of up to 21 months following the Company’s 2020 Annual Meeting of Stockholders held on May 12, 2020, where stockholders of the Company voted to approve an amendment to the Company’s Restated Certificate of Incorporation to increase the authorized number of shares of the Company’s common stock to 140,000,000 . As consideration for the future tranche rights, the Company received aggregate gross proceeds of $6.2 million in December 2019. ​ The purchase and sale of the securities issuable under the Series B2, B3, and B4 tranches described above were subject to three separate closings, each to be conducted at the purchasers’ discretion. The right of the purchasers to purchase Series B2, Series B3, and Series B4 Preferred Stock was set to expire on the 10th business day following the Company’s ORR Data Announcement (as defined in the for its ILLUMINATE-301 study. ​ Accounting Considerations ​ The Company determined that the Series B1 Preferred Stock, the accompanying Series B1 warrants, and each of the future tranche rights represent freestanding financial instruments. The Series B1 warrants and the future tranche rights were classified as liabilities until their termination in March 2021 as the underlying shares were potentially redeemable and such redemption was deemed to be outside of the Company’s control. ​ Due to the redeemable nature of the Series B1 Preferred Stock, the Series B1 Preferred Stock was classified as temporary equity and the carrying value was being accreted to its redemption value as of December 31, 2020 and while the Series B1 Preferred Stock was outstanding during 2021. During the nine months ended September 30, 2021, all the Company’s 23,684 shares of Series B1 Preferred Stock outstanding were converted into shares of the Company’s common stock. See Note 10 for details. For the three and nine months ended September 30, 2022 and 2021, accretion was de minimis. ​ Series Z Redeemable Preferred Stock ​ In connection with the Acquisition of Aceragen, the Company issued 80,656 shares of Series Z. Series Z shares are not entitled to vote except for specific corporate matters including (i) changes to the rights and preferences of the Series Z shares, (ii) issuance of additional Series Z shares, and (iii) enter into a fundamental transaction such as a sale of the Company. Certain provisions of the outstanding Series Z are as follows: ​ ● Conversion: Upon obtaining stockholder approval, each share of Series Z will automatically convert into 1,000 shares of common stock, subject to beneficial ownership limitations. ● Dividends: Series Z participates in any dividends with common stockholders on an as-converted basis. ● Liquidation: In the event of the liquidation, dissolution, or winding up of the affairs of the Company (a “Liquidity Event”), the holders of Series Z are entitled to receive a liquidation preference prior to any payment to the holders of common stock. ● Redemption: In the event the Company is unable to obtain an affirmative stockholder vote to permit conversion, each holder of Series Z may elect, at the holder’s option, to have the shares of Series Z be redeemed by the Company and equal to the estimated fair value of the Series Z share at the time of redemption. Due to this redemption feature, the Series Z has been classified within temporary equity on the consolidated balance sheet at September 30, 2022.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2022
Stockholders' Equity
Stockholders' Equity	Note 10. Stockholders’ Equity ​ Equity Financings ​ Common Stock Purchase Agreement ​ On March 4, 2019, the Company entered into a Purchase Agreement with Lincoln Park Capital Fund, LLC (“Lincoln Park”), which was amended on September 2, 2020 (as amended to date, the “LPC Purchase Agreement”), pursuant to which, upon the terms and subject to the conditions and limitations set forth therein, Lincoln Park committed to purchase an aggregate of $35.0 million of shares of Company common stock from time to time at the Company’s sole discretion over a 36-month period (the “Purchase Period”). As consideration for entering into the LPC Purchase Agreement, the Company issued 269,749 shares of its common stock to Lincoln Park as a commitment fee (the “Commitment Shares”). The closing price of the Company’s common stock on March 4, 2019 was $2.84 and the Company did not receive any cash proceeds from the issuance of the Commitment Shares. ​ During the nine months ended September 30, 2022, the Company did not sell any shares under the LPC Purchase Agreement. The Purchase Period expired on March 4, 2022. Accordingly, the Company no longer has access to additional capital under the LPC Purchase Agreement. ​ During the nine months ended September 30, 2021, the Company sold 800,000 shares of common stock, pursuant to the LPC Purchase Agreement, resulting in net proceeds of $4.2 million. ​ "At-The-Market" Equity Program ​ In November 2018, the Company entered into an Equity Distribution Agreement (the “ATM Agreement”) with JMP Securities LLC (“JMP”) pursuant to which the Company may issue and sell shares of its common stock having an aggregate offering price of up to $50.0 million (the “Shares”) through JMP as its agent. Subject to the terms and conditions of the ATM Agreement, JMP will use commercially reasonable efforts to sell the Shares from time to time, based upon the Company’s instructions, 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, or if specified by the Company, by any other method permitted by law, including but not limited to in negotiated transactions. The Company has no obligation to sell any of the Shares, and the Company or JMP may at any time suspend sales under the ATM Agreement or terminate the ATM Agreement. JMP is entitled to a fixed commission of 3.0% of the gross proceeds from Shares sold. ​ During the nine months ended September 30, 2022, the Company sold no Shares pursuant to the ATM Agreement. ​ During the nine months ended September 30, 2021, the Company sold 5,117,357 Shares pursuant to the ATM Agreement, resulting in net proceeds, after deduction of commissions and other offering expenses, of $15.3 million. As of September 30, 2022, the Company may sell up to an additional $19.5 million of Shares under the ATM Agreement, subject to applicable securities laws and related rules and regulations. ​ April 2020 Private Placement ​ On April 7, 2020, the Company entered into a Securities Purchase Agreement with Pillar Partners (as defined below), a related party as more fully described in Note 14, which was amended on December 11, 2020 (as amended to date, the “April 2020 Securities Purchase Agreement”), under which the Company sold 3,039,514 shares of common stock and accompanying warrants to purchase 3,039,514 shares of the Company’s common stock with an exercise price of $2.28 per share, for aggregate gross proceeds of $5.0 million. Each share and the accompanying warrant had a combined purchase price of $1.645, which included $0.125 for each share of common stock underlying each warrant. The April 2020 Securities Purchase Agreement also provided for the option for Pillar Partners to purchase 2,747,252 shares of the Company’s common stock (or pre-funded warrants to purchase shares of the Company’s common stock at an exercise price of $0.01 in lieu of certain shares to the extent that purchasing such shares will cause Pillar Investment Entities (as defined below) to beneficially own in excess of 19.99% of the total number of shares of common stock outstanding post-transaction) and warrants to purchase up to 1,373,626 shares of the Company’s common stock (with an exercise price of $2.71), for aggregate gross proceeds of $5.0 million (the “April 2020 Private Placement Second Closing”). Subsequently, in December 2020, the April 2020 Private Placement Second Closing was consummated. Total net proceeds received pursuant to the April 2020 Securities Purchase Agreement, after deduction of offering expenses, was $9.8 million. ​ July 2020 Private Placement On July 13, 2020, the Company entered into a Securities Purchase Agreement (the “July 2020 Securities Purchase Agreement”) with Pillar Partners Foundation, L.P. (“Pillar Partners”), Pillar Pharmaceuticals 6, L.P. (“Pillar 6”), and Pillar Pharmaceuticals 7 L.P. (“Pillar 7”) (collectively, the “July 2020 Purchasers”), each a related party as more fully described in Note 10, pursuant to which, among other things, provided the July Purchasers the option to purchase, at their sole discretion, pre-funded warrants to purchase up to 784,615 shares of the Company’s common stock, at an exercise price of $0.01 per share, and warrants to purchase up to 274,615 shares of the Company’s common stock, at an exercise price of $9.75, for aggregate gross proceeds of $5.1 million (the “July 2020 Private Placement Second Closing”). During the three months ended March 31, 2021, the option to purchase securities in the July 2020 Private Placement Second Closing terminated. As a result, the Company is no longer eligible to receive additional proceeds from the sale of additional securities pursuant to the July 2020 Securities Purchase Agreement. However, the July 2020 Purchasers still hold outstanding warrants previously issued under the July 2020 Securities Purchase Agreement, as detailed below under the heading “Common Stock Warrants”. ​ Warrants ​ In connection with various financing transactions, the Company has issued warrants to purchase shares of the Company’s common stock and preferred stock. The Company accounts for common and preferred stock warrants as equity instruments or liabilities, depending on the specific terms of the warrant agreement. ​ In connection with the Acquisition of Aceragen, the Company issued warrants to former Aceragen warrant holders to purchase shares of its common stock and Series Z. Series Z warrants are liability classified and remeasured at each reporting period. ​ The following table summarizes outstanding warrants to purchase shares of the Company’s common stock and/or preferred stock as of September 30, 2022 and December 31, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number of Shares ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ Weighted-Average ​ ​ ​ Description ​ 2022 ​ 2021 ​ Exercise Price ​ Expiration Date ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity-classified warrants ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ May 2013 warrants 15,437 ​ 15,437 ​ ​ $ 0.08 ​ None ​ September 2013 warrants 4,096 ​ 4,096 ​ ​ $ 0.08 ​ None ​ February 2014 warrants 2,171 ​ 2,171 ​ ​ $ 0.08 ​ None ​ April 2020 Private Placement first closing warrants ​ 3,039,514 ​ 3,039,514 ​ ​ $ 2.28 ​ Apr 2023 ​ April 2020 Private Placement second closing warrants ​ 1,373,626 ​ 1,373,626 ​ ​ $ 2.71 ​ Dec 2023 ​ April 2020 Private Placement second closing warrants ​ — ​ 1,143,428 ​ ​ $ 0.01 ​ None ​ July 2020 Private Placement first closing warrants ​ — ​ 389,731 ​ ​ $ 0.01 ​ None ​ July 2020 Private Placement first closing warrants ​ 2,764,227 ​ 2,764,227 ​ ​ $ 2.58 ​ Jul 2023 ​ ​ ​ 7,199,071 ​ 8,732,230 ​ ​ ​ ​ ​ ​ Liability-classified warrants ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Aceragen Acquisition warrants: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Convertible to common stocks ​ 1,353,143 ​ — ​ ​ $ 0.46 ​ 3/23/2031 ​ Convertible to preferred stocks ​ 14,215 ​ — ​ ​ $ 460.00 ​ 3/23/2031 ​ ​ ​ 1,367,358 ​ — ​ ​ ​ ​ ​ ​ Total outstanding 8,566,429 ​ 8,732,230 ​ ​ ​ ​ ​ ​ ​

Collaboration and License Agree

Collaboration and License Agreements	9 Months Ended
	Sep. 30, 2022
Collaboration and License Agreements
Collaboration and License Agreements	Note 11. Collaboration and License Agreements ​ Scriptr Collaboration and Option Agreement ​ In February 2021, the Company entered into a collaboration and option agreement with Scriptr Global, Inc. (“Scriptr”), pursuant to which (i) the Company and Scriptr conduct a research collaboration utilizing Scriptr Platform Technology (“SPT”) to identify, research and develop gene therapy candidates (each, a “Collaboration Candidate”) for the treatment, palliation, diagnosis or prevention of (a) myotonic dystrophy type 1 (“DM1 Field”) and (b) Friedreich’s Ataxia (“FA Field”) on a Research Program-by-Research Program (as defined below) basis, as applicable, and (ii) the Company was granted an exclusive option, in its sole discretion, to make effective the Scriptr License Agreement, as defined below, for a given Research Program, as defined below, to make use of Collaboration Candidates and related intellectual property (collectively, the “Scriptr Agreement”). ​ Pursuant to the Scriptr Agreement, Scriptr will use commercially reasonable efforts to carry out research activities set forth in accordance with the applicable DM1 Field and FA Field research plans, including certain pre-clinical proof of concept studies, to identify research Collaboration Candidates utilizing SPT (each, a “Research Program”). Following the completion of activities under a given Research Program, Scriptr will prepare and submit to the Company a comprehensive data package (each, a “Data Package”) that summarizes, on a Research Program-by-Research Program basis, any Collaboration Candidates researched under the Research Program, including any data and results. Upon receipt of a Data Package, the Company has, in its sole discretion, up to two-hundred seventy ( 270 ) calendar days to make effective the exclusive license agreement entered into by and between the Company and Scriptr, pursuant to which, among other things, Scriptr grants the Company exclusive rights and licenses with respect to the development, manufacture and commercialization of licensed candidates and products, subject to certain conditions and limitations (the “Scriptr License Agreement”), for a given Research Program (each licensed Research Program, a “Licensed Program”). The Scriptr License Agreement provides for customary development milestones on candidates developed under a Licensed Program and royalties on licensed products, if any. ​ In partial consideration of the rights granted by Scriptr to the Company under the Scriptr Agreement, the Company made a one-time, non-creditable and non-refundable payment to Scriptr during the first quarter of 2021. The Company reimburses Scriptr for costs incurred by or on behalf of Scriptr in connection with the conduct of each Research Program during the research term in accordance with the applicable Research Program budget and payment schedule. The Company incurred approximately

Restructuring and Other Costs

Restructuring and Other Costs	9 Months Ended
	Sep. 30, 2022
Restructuring and Other Costs
Restructuring and Other Costs	​ Note 12. Restructuring and Other Costs ​ On September 28, 2022, in connection with the Aceragen Acquisition, the Company determined to restructure its operations and reduce the workforce (the “2022 reduction-in-workforce”). In connection with the 2022 reduction-in-workforce, five positions were eliminated, representing approximately 38% of the Company’s pre-merger employees. All five of the positions were eliminated on or before September 30, 2022. ​ Restructuring-related charges for both the three and nine months ended September 30, 2022 totaled approximately $2.8 million and were comprised of the one-time termination costs in connection with the 2022 reduction-in-workforce, including severance, benefits and related costs. ​ As of September 30, 2022, the short-term portion of the accrued restructuring balance, or $2.7 million, is included in “Accrued expenses” in the accompanying condensed consolidated balance sheets. The long-term portion of $0.1 million is included within “Other liabilities” in the accompanying condensed consolidated balance sheets. ​ In the second quarter of 2021, following the announcement that the Company’s ILLUMINATE-301 trial did not meet its primary endpoint of objective response rate (“ORR”), the Company implemented a reduction in force which affected approximately 50% of its workforce (the “2021 reduction-in-workforce”). In total, sixteen positions were eliminated, primarily in the area of research and development. The 2021 reduction-in-force was undertaken in order to align the Company’s workforce with its needs in light of the outcome of ILLUMINATE-301’s ORR endpoint and other business development activities focused on identifying new portfolio opportunities. ​ In connection with these actions, the Company incurred and paid one-time termination costs for the 2021 reduction-in-workforce, which includes severance, benefits and related costs, of approximately $0.1 million during third quarter of 2021. ​

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2022
Stock-Based Compensation
Stock-Based Compensation	Note 13. Stock-Based Compensation ​ As of September 30, 2022, the equity compensation plans under which the Company may currently issue new awards are the Company’s 2013 Stock Incentive Plan (as amended to date, the “2013 Plan”), 2017 Employee Stock Purchase Plan (as amended to date, the “2017 ESPP”), and the Aceragen, Inc. 2021 Stock Incentive Plan (the “Aceragen Plan”), which was assumed by the Company in connection with the Acquisition, each as more fully described below. ​ Equity Incentive and Employee Stock Purchase Plans ​ Stock options issued in connection with Aceragen Acquisition (Assumed Aceragen, Inc. 2021 Stock Incentive Plan) ​ In connection with the Aceragen Acquisition, all options existing under the pre-acquisition Aceragen Plan and held by Continuing Employees (as defined in the Merger Agreement) were assumed by the Company and converted into options to purchase shares of common stock and Series Z on the same terms and conditions as applied to such options and warrants immediately prior to the Aceragen Acquisition. ​ The Aceragen Plan provides for the grant of incentive stock options, non-incentive stock options, restricted stock, restricted stock units and other stock-based awards to eligible recipients. Eligible recipients include employees, officers, directors, and individual consultants and advisors. The maximum term of options granted under the Aceragen Plan is ten years . Historically, option grants under the Aceragen Plan to employees have vested 25% on the first anniversary of grant date, with the balance vesting proportionally for a duration of three years thereafter, and grants to non-employee option holders have vested in quarterly increments over two years . The vesting schedule applicable to options granted under the Aceragen Plan and assumed in the Acquisition was unaffected by the Acquisition and such assumed options shall continue to vest according to the applicable vesting schedule. The Company does not plan to issue any additional awards under this plan. ​ As of September 30, 2022, there was $4.7 million of total unrecognized compensation cost related to unvested time vesting awards under the Aceragen Plan, which is expected to be recognized over the remaining period up to 3.75 years. ​ In addition, the Company issued 3,278,859 shares of its common stock to Aceragen stockholders that are subject to forfeiture if future services are not provided. Shares subject to forfeiture are recognized as outstanding when vested and no longer subject to forfeiture or repurchase. As of September 30, 2022, there was $0.7 million of total unrecognized compensation cost related to these unvested, time vesting restricted shares which is expected to be recognized over the remaining 2 years . ​ 2013 Stock Incentive Plan ​ The 2013 Plan allows for the issuance of incentive stock options intended to qualify under the amended Section 422 of the Code, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock units (“RSUs”), other stock-based awards and performance awards. ​ At the 2022 Annual Meeting of stockholders of the Company held on June 23, 2022 (the “Annual Meeting”), the Company’s stockholders approved an amendment (the “2022 Stock Plan Amendment”) to the Company’s 2013 Plan to increase the number of shares reserved for issuance under the 2013 Plan by 4,600,000 shares of the Company’s common stock. Accordingly, the total authorized shares of common stock under the 2013 Plan increased to 10,253,057 shares of the Company’s common stock, plus such additional number of shares of common stock (up to 155,968 shares) as is equal to the number of shares of common stock subject to awards granted under the Company’s 2008 Stock Incentive Plan (the “2008 Plan”), to the extent such awards expire, terminate or are otherwise surrendered, canceled, forfeited or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right. ​ As of September 30, 2022, options to purchase a total of 5,312,800 shares of common stock and 831,698 RSUs were outstanding and up to 3,806,601 shares of common stock remained available for grant under the 2013 Plan. ​ Other Awards and Inducement Grants ​ The Company has not made any awards pursuant to other equity incentive plans, including the 2008 Plan, since the Company’s stockholders approved the 2013 Plan. As of September 30, 2022, options to purchase a total of 145,968 shares of common stock were outstanding under the 2008 Plan. In addition, as of September 30, 2022, non-statutory stock options to purchase an aggregate of 325,000 shares of common stock were outstanding that were issued outside of the 2013 Plan to certain employees in 2015 and 2014 pursuant to the Nasdaq inducement grant exception as a material component of new hires’ employment compensation. ​ 2017 Employee Stock Purchase Plan ​ The 2017 ESPP is intended to qualify as an "employee stock purchase plan" as defined in Section 423 of the Code, ​ At the Annual Meeting, the Company’s stockholders approved an amendment (the “2022 ESPP Amendment”) to the Company’s 2017 ESPP to increase the number of shares authorized for issuance under the 2017 ESPP by 600,000 shares of common stock. Accordingly, the total authorized shares of common stock under the 2017 ESPP increased to 1,012,500 shares of common stock, subject to adjustment as described in the 2017 ESPP. As of September 30, 2022, 683,788 shares remained available for issuance under the 2017 ESPP. ​ For the nine months ended September 30, 2022 and 2021, the Company issued 112,437 and 29,016 shares of common stock, respectively, under the 2017 ESPP and received proceeds of less than $0.1 million during each period, as a result of employee stock purchases. ​ Accounting for Stock-based Compensation ​ The Company recognizes non-cash compensation expense for stock-based awards under the Company’s equity incentive plans and employee stock purchases under the Company’s 2017 ESPP as follows: ● Stock Options : Compensation cost is recognized over an award’s requisite service period, or vesting period, using the straight-line attribution method, based on the grant date fair value determined using the Black-Scholes option-pricing model. ● RSUs : Compensation cost for time-based RSUs, which vest over time based only on continued service, is recognized on a straight-line basis over the requisite service period based on the fair value of the Company’s common stock on the date of grant. Compensation cost for awards that are subject to market considerations is recognized on a straight-line basis over the implied requisite service period, based on the grant date fair value estimated using a Monte Carlo simulation. Compensation cost for awards that are subject to performance conditions is recognized over the period of time commencing when the performance condition is deemed probable of achievement based on the fair value of the Company’s common stock on the date of grant. ● Employee Stock Purchases : Compensation cost is recognized over each plan period based on the fair value of the look-back provision, calculated using the Black-Scholes option-pricing model, considering the 15% discount on shares purchased. ​ ​ Total stock-based compensation expense attributable to stock-based awards made to employees and directors and employee stock purchases included in operating expenses in the Company's condensed consolidated statements of operations for the three and nine months ended September 30, 2022 and 2021 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ September 30, ​ September 30, (in thousands) ​ 2022 2021 ​ 2022 2021 Stock-based compensation: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Research and development ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee Stock Purchase Plan ​ $ 6 $ 7 ​ $ 21 $ 22 Equity Incentive Plan ​ ​ 53 ​ 51 ​ ​ 194 ​ 469 ​ ​ $ 59 $ 58 ​ $ 215 $ 491 General and administrative ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee Stock Purchase Plan ​ $ 2 $ — ​ $ 5 $ 3 Equity Incentive Plan ​ ​ 350 ​ 417 ​ ​ 1,298 ​ 1,496 ​ ​ $ 352 $ 417 ​ $ 1,303 $ 1,499 Total stock-based compensation expense ​ $ 411 $ 475 ​ $ 1,518 $ 1,990 ​ During the nine months ended September 30, 2022 and 2021, the weighted average fair market value of stock options granted was $0.35 and $1.54, respectively. ​ The following weighted average assumptions apply to the options to purchase 1,169,800 and 1,356,700 shares of common stock granted to employees and directors during the three and nine months ended September 30, 2022 and 2021, respectively: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2022 2021 Average risk-free interest rate ​ 2.6% ​ ​ 0.4% ​ Expected dividend yield ​ ​ — ​ ​ — ​ Expected lives (years) ​ 3.8 ​ ​ 3.6 ​ Expected volatility ​ 104% ​ ​ 94% ​ Weighted average exercise price (per share) ​ $ 0.49 ​ $ 2.68 ​ ​ All options granted during the nine months ended September 30, 2022 and 2021 were granted at exercise prices equal to the fair market value of the Company’s common stock on the dates of grant . ​ Stock Option Activity ​ The following table summarizes stock option activity for the nine months ended September 30, 2022: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ($ in thousands, except per share data) ​ Common Stock Options ​ Weighted-Average Exercise Price ​ Weighted-Average Remaining Contractual Life (in years) ​ Aggregate Intrinsic Value Outstanding at December 31, 2021 5,202,006 ​ $ 8.06 5.9 ​ $ 2,949 ​ Granted 1,169,800 ​ ​ 0.49 ​ ​ ​ ​ ​ ​ Exercised — ​ ​ — ​ ​ ​ ​ ​ ​ Forfeited — ​ ​ — ​ ​ ​ ​ ​ ​ Expired (588,038) ​ ​ 2.87 ​ ​ ​ ​ ​ ​ Options assumed in connection with Aceragen Acquisition ​ 1,887,860 ​ ​ 4.15 ​ 9.3 ​ ​ ​ ​ Outstanding at September 30, 2022 7,671,628 ​ $ 6.34 ​ 7.3 ​ $ — ​ Exercisable at September 30, 2022 4,218,823 ​ $ 9.29 ​ 5.7 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Preferred Stock Options ​ Weighted-Average Exercise Price ​ Weighted-Average Remaining Contractual Life (in years) ​ ​ Aggregate Intrinsic Value Outstanding at December 31, 2021 — ​ $ — ​ — ​ ​ — ​ Options assumed in connection with Aceragen Acquisition ​ 19,826 ​ ​ 394.82 ​ 9.3 ​ ​ ​ ​ Outstanding at September 30, 2022 19,826 ​ $ 394.82 ​ 9.3 ​ $ — ​ Exercisable at September 30, 2022 2,187 ​ $ 142.05 ​ 8.9 ​ $ — ​ ​ As of September 30, 2022, there was $1.0 million of unrecognized compensation cost related to unvested options, which the Company expects to recognize over a weighted average period of 2.4 years. During the three months ended March 31, 2021, the Company accelerated the vesting of 1,535,578 options, which were previously granted during 2019 through 2021 (the “2021 Option Acceleration”). The modification resulted in an incremental stock-based compensation charge that was not significant. In January 2022, for members of the Company’s Leadership team, the Compensation Committee of the Board of Directors implemented a post-exercise holding period prohibiting the sale of shares associated with the 2021 Option Acceleration on any schedule more favorable than the original vesting schedule (i.e., 6.25% of the total option grant every quarter and 25% of the total RSU grant every year). This post-exercise holding period has no financial statement impact. ​ Restricted Stock Activity ​ The following table summarizes restricted stock activity for the nine months ended September 30, 2022: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Time-based Awards ​ Market/Performance-based Awards ($ in thousands, except per share data) ​ Number of Shares ​ Weighted-Average Grant Date Fair Value ​ Number of Shares ​ Weighted-Average Grant Date Fair Value Nonvested shares at December 31, 2021 68,675 ​ $ 2.30 ​ 507,028 ​ $ 1.54 Granted 283,207 ​ 0.40 ​ — ​ — Cancelled — ​ — ​ — ​ — Vested (27,212) ​ 2.43 ​ — ​ — Nonvested shares at September 30, 2022 324,670 ​ $ 0.63 ​ 507,028 ​ $ 1.54 ​ Time-based Restricted Stock Units ​ During the three months ended March 31, 2021, the Company accelerated the vesting of 137,872 unvested time-based RSUs which were previously granted during 2019 and 2020. The modification resulted in an incremental stock-based compensation charge that was not significant. During the nine months ended September 30, 2022, the Company recognized $0.1 million of compensation expense related to these awards. As of September 30, 2022, there was $0.2 million of unrecognized compensation expense related to the Company’s time-based RSUs, which is expected to be recognized over a weighted-average period of one year . ​ Market/Performance-based Restricted Stock Units ​ In July 2020, the Company granted RSUs to certain employees, including executive officers, under the 2013 Plan, with vesting that may occur upon a combination of specific performance and/or market conditions. Accordingly, the Company views these RSUs as two separate awards: (i) an award that vests if the market condition is achieved, and (ii) an award that vests whether or not the market condition is achieved, so long as the performance condition is achieved. The Company is currently recognizing compensation expense for these awards over the estimated requisite service period of 2.36 years based on the estimated fair value when considering the market condition of the award, which was determined using a Monte Carlo simulation. ​ During the nine months ended September 30, 2022, the Company recognized $0.1 million of compensation expense related to these awards. As of September 30, 2022, the remaining unrecognized compensation cost for the market-based component of these awards, which is expected to be recognized over a weighted-average period of 0.2 years, was $0.1 million. In addition, should the performance condition be achieved, the Company would recognize an additional $0.3 million of compensation expense.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2022
Related Party Transactions
Related Party Transactions	Note 14. Related Party Transactions ​ Pillar Investment Entities ​ Youssef El Zein, a member of the Company’s Board of Directors until his resignation in October 2017, is a director and controlling stockholder of Pillar Invest Corporation (“Pillar Invest”), which is the general partner of Pillar Pharmaceuticals I, L.P., Pillar Pharmaceuticals II, L.P., Pillar Pharmaceuticals III, L.P., Pillar Pharmaceuticals IV, L.P., Pillar Pharmaceuticals V, L.P., Pillar 6, Pillar 7, and Pillar Partners (collectively, the “Pillar Investment Entities”). As of September 30, 2022, the Pillar Investment Entities owned approximately 16% of the Company's common stock and beneficially owned approximately 19.99% of the Company's common stock. ​ As of September 30, 2022, the Pillar Investment Entities held (i) warrants to purchase up to 3,039,514 shares of the Company’s common stock at an exercise price of $2.28 per share, (ii) warrants to purchase up to 2,764,227 shares of the Company’s common stock at an exercise price of $2.58 per share, and (iii) warrants to purchase up to 1,373,626 shares of the Company’s common stock at an exercise price of $2.71 per share. ​ During the , certain of the Pillar Investment Entities exercised warrants to purchase 1,533,159 shares of the Company’s common stock at an exercise price of $0.01 per share for a total exercise price of less than $0.1 million. ​ During the , certain of the Pillar Investment Entities exercised warrants to purchase 3,158,386 shares of the Company’s common stock at an exercise price of $0.01 per share for a total exercise price of less than $0.1 million. 19,052 shares were used to fund the exercise costs. ​ Board Fees Paid in Stock ​ Pursuant to the Company’s director compensation program, in lieu of director board and committee fees of $0.1 million during each of the nine months ended September 30, 2022 and 2021, the Company issued 149,757 and 68,699 shares of common stock, respectively, to certain of its directors. Director board and committee fees are paid in arrears and the number of shares issued was calculated based on the market closing price of the Company’s common stock on the issuance date.

Net Income (Loss) per Common Sh

Net Income (Loss) per Common Share	9 Months Ended
	Sep. 30, 2022
Net Income (Loss) per Common Share
Net Income (Loss) per Common Share	Note 15. Net Income (Loss) per Common Share ​ During periods the Company realizes net income, it uses the two-class method to compute net income per common share and has securities outstanding (redeemable convertible preferred stock) that entitle the holder to participate in dividends and earnings of the Company. In addition, the Company analyzes the potential dilutive effect of outstanding redeemable convertible preferred stock under the "if-converted" method when calculating diluted earnings per share and reports the more dilutive of the approaches (two class or "if-converted"). The two-class method is not applicable during periods with a net loss, as the holders of the redeemable convertible preferred stock have no obligation to fund losses. ​ The Company also analyzes the potential dilutive effect of stock options, restricted stock units, warrants and shares underlying future tranche rights under the treasury stock method (as applicable), during periods of income, or during periods in which income is recognized related to changes in fair value of its liability-classified securities. ​ For the nine months ended September 30, 2021, the Company used the two-class method to compute net income per common share. Under this method, net income is reduced by the amount of any dividends earned and the accretion of redeemable convertible preferred stock to its redemption value, if any, during the period. The remaining earnings (undistributed earnings) are allocated to common stock and each series of redeemable convertible preferred stock to the extent that each preferred security may share in earnings as if all the earnings for the period had been distributed. The total earnings allocated to common stock is then divided by the number of outstanding shares to which the earnings are allocated to determine the earnings per share. ​ However, during periods the Company realizes net loss, basic and diluted net loss per common share applicable to common stockholders is calculated by dividing net loss applicable to common stockholders by the weighted-average number of shares of common stock outstanding during the period, without consideration of common stock equivalents. The Company’s potentially dilutive shares, which include outstanding stock option awards, common stock warrants and convertible preferred stock, are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. ​ For the three and nine months ended September 30, 2022, diluted net loss per common share applicable to common stockholders was the same as basic net loss per common share applicable to common stockholders as the effects of the Company’s potential common stock equivalents were antidilutive. ​ ​ Details in the computation of basic and diluted net income (loss) per common share were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ($ in thousands except per share data) ​ ​ 2022 ​ ​ 2021 ​ ​ 2022 ​ ​ 2021 Net (loss) income per share — Basic: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net (loss) income ​ $ (3,099) ​ $ (5,965) ​ $ (12,584) ​ $ 102,210 Less: Undistributed earnings to preferred stockholders ​ ​ — ​ ​ — ​ ​ ​ ​ ​ (1,636) Net (loss) income applicable to common stockholders - basic ​ $ (3,099) ​ $ (5,965) ​ $ (12,584) ​ $ 100,574 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Numerator for basic net (loss) income applicable to common stockholders ​ $ (3,099) ​ $ (5,965) ​ $ (12,584) ​ $ 100,574 Denominator for basic net (loss) income applicable to common stockholders ​ ​ 53,286 ​ ​ 52,740 ​ ​ 53,052 ​ ​ 47,990 Net (loss) income applicable to common stockholders - basic ​ $ (0.06) ​ $ (0.11) ​ $ (0.24) ​ $ 2.10 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net (loss) income per share — Diluted: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net (loss) income ​ $ (3,099) ​ $ (5,965) ​ $ (12,584) ​ $ 102,210 Less: Warrant revaluation gain applicable to dilutive liability-classified warrants ​ ​ — ​ ​ — ​ ​ — ​ ​ (6,983) Less: Future tranche right revaluation gain applicable to dilutive liability-classified future tranche rights ​ ​ — ​ ​ — ​ ​ — ​ ​ (118,803) Numerator for diluted net (loss) income applicable to common stockholders ​ $ (3,099) ​ $ (5,965) ​ $ (12,584) ​ $ (23,576) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator for basic net (loss) income applicable to common stockholders ​ ​ 53,286 ​ ​ 52,740 ​ ​ 53,052 ​ ​ 47,990 Plus: Incremental shares underlying “in the money” liability-classified warrants outstanding ​ ​ — ​ ​ — ​ ​ — ​ ​ 223 Plus: Incremental shares underlying “in the money” liability-classified future tranche rights outstanding ​ ​ — ​ ​ — ​ ​ — ​ ​ 3,400 Denominator for diluted net income (loss) applicable to common stockholders ​ ​ 53,286 ​ ​ 52,740 ​ ​ 53,052 ​ ​ 51,613 Net (loss) income applicable to common stockholders - diluted ​ $ (0.06) ​ $ (0.11) ​ $ (0.24) ​ $ (0.46) ​ Total antidilutive securities excluded from the calculation of diluted net loss per share for the three and nine months ended September 30, 2022 and 2021 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, (in thousands) ​ ​ 2022 ​ ​ 2021 ​ ​ 2022 ​ ​ 2021 Stock options ​ ​ 5,783 ​ ​ 5,329 ​ ​ 5,783 ​ ​ 5,329 Restricted stock units ​ ​ 832 ​ ​ 576 ​ ​ 832 ​ ​ 576 Common stock warrants ​ ​ 8,566 ​ ​ 8,732 ​ ​ 8,566 ​ ​ 8,732 Total ​ ​ 15,181 ​ ​ 14,637 ​ ​ 15,181 ​ ​ 14,637 ​

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2022
Subsequent Events
Subsequent Events	Note 1 6 . Subsequent Events ​ The Company has evaluated all subsequent events through November 14, 2022, the date the condensed consolidated financial statements were available to be issued and determined that there were no subsequent events or transactions that required recognition or disclosure in the condensed consolidated financial statements. ​ ​

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2022
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation ​ The unaudited interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All material intercompany balances and transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) for interim financial information and the instructions to Form 10-Q. Accordingly, certain information and footnote disclosures normally included in consolidated financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. In the opinion of management, all adjustments, consisting of normal recurring adjustments, and disclosures considered necessary for a fair presentation of interim period results have been included. Interim results for the nine months ended September 30, 2022 are not necessarily indicative of results that may be expected for the year ending December 31, 2022. For further information, refer to the consolidated financial statements and footnotes thereto included in the Company’s 2021 Form 10-K.
Use of Estimates	Use of Estimates ​ The preparation of the Company’s unaudited condensed consolidated financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the unaudited condensed consolidated financial statements and reported amounts of revenues and expenses during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances and are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from these estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents ​ The Company considers all highly liquid investments with maturities of 90 days or less when purchased to be cash equivalents. Cash and cash equivalents at September 30, 2022 and December 31, 2021 consisted of cash and money market funds.
Financial Instruments	Financial Instruments ​ At September 30, 2022 and December 31, 2021, the Company’s financial instruments included accounts payable, accrued expenses, stockholder notes and debt. The carrying amount of cash and cash equivalents, accounts receivable, accounts payable and accrued expenses approximates fair value due to the short-term maturities of these instruments. Each of the carrying values of the preferred stock warrant liabilities and Series X preferred stock liability issued to Aceragen stockholders and the acquisition obligation assumed in connection with the Acquisition of Aceragen are recorded at their estimated fair values. As of September 30, 2022, the Company did not have any derivatives, hedging instruments or other similar financial instruments.
Government Receivables - Billed and Unbilled	Accounts Receivable ​ Accounts receivables are recorded net of an estimated expected credit losses. The Company’s measurement of expected credit losses is based on relevant information about past events, including historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. To date, there have been no expected credit losses as the Company’s customer is the U.S. government. Unbilled accounts receivable at September 30, 2022 which is included in accounts receivables is $1.1 million and relates to revenue recognized for work that has been performed but the invoicing has not yet occurred.
Foreign Currency	Foreign Currency ​ Upon completion of the Acquisition of Aceragen in September 2022, the Company has a wholly-owned subsidiary in Switzerland and the functional currency is the Swiss Franc. The results of the Company’s non-US dollar based functional currency operations are translated to US dollars at the average exchange rates during the period. Assets and liabilities are translated at the exchange rate prevailing at the balance sheet date. Equity is translated at the prevailing exchange rate at the date of the equity transaction. Translation adjustments are included in stockholders' equity, as a component of accumulated other comprehensive income. ​ The Company realizes foreign currency transaction gains (losses) in the normal course of business based on movements in the applicable exchange rates. These gains (losses) are included as a component of other (expense) income, net.
Business Combinations	Business Combinations ​ The Company evaluates acquisitions of assets and other similar transactions to assess whether or not the transaction should be accounted for as a business combination or asset acquisition by first applying a screen to determine if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets. If the screen is met, the transaction is accounted for as an asset acquisition. If the screen is not met, further determination is required as to whether or not the Company has acquired inputs and processes that have the ability to create outputs, which would meet the requirements of a business. If determined to be a business combination, the Company accounts for the transaction under the acquisition method of accounting as indicated in Accounting Standard Update (“ASU”) 2017-01, Business Combinations
Goodwill	Goodwill ​ Goodwill represents the amount of consideration paid in excess of the fair value of net assets acquired as a result of the Company’s business acquisitions accounted for using the acquisition method of accounting. The intangible assets acquired represented the fair value of in-process research and development (IPR&D) which has been recorded on the accompanying condensed consolidated balance sheet as indefinite-lived intangible assets. A deferred tax liability was recorded for the difference between the fair value of the acquired IPR&D and its tax basis which was recognized as goodwill in applying the purchase method of accounting. Goodwill is not amortized and is subject to impairment testing at a reporting unit level on an annual basis or when a triggering event occurs that may indicate the carrying value of the goodwill is impaired. An entity is permitted to first assess qualitative factors to determine if a quantitative impairment test is necessary. Further testing is only required if the entity determines, based on the qualitative assessment, that it is more likely than not that the fair value of the reporting unit is less than its carrying amount. ​ We evaluate goodwill for impairment at least annually on October 1 and whenever facts and circumstances indicate that their carrying amounts may not be recoverable. For the nine months ended September 30, 2022, the Company determined that there was no impairment to goodwill.
Indefinite-Lived Intangible Assets	Indefinite-Lived Intangible Assets ​ Indefinite-lived intangible assets consist of In-Process Research and Development(“IPR&D”). The fair values of IPR&D project assets acquired in business combinations are capitalized. The Company generally utilizes the Multi-Period Excess Earning Method to determine the estimated fair value of the IPR&D assets acquired in a business combination. The projections used in this valuation approach are based on many factors, such as relevant market size and share, probabilities of success, anticipated patent protection, and expected pricing. The estimated future net cash flows are then discounted to the present value using an appropriate discount rate. These assets are treated as indefinite-lived intangible assets until completion or abandonment of the projects, at which time the assets are amortized over the remaining useful life or written off, as appropriate. ​ Intangible assets with indefinite lives, including IPR&D, are tested for impairment if impairment indicators arise and, at a minimum, annually. However, an entity is permitted to first assess qualitative factors to determine if a quantitative impairment test is necessary. Further testing is only required if the entity determines, based on the qualitative assessment, that it is more likely than not that an indefinite-lived intangible asset’s fair value is less than its carrying amount. Otherwise, no further impairment testing is required. The indefinite-lived intangible asset impairment test consists of a one-step analysis that compares the fair value of the intangible asset with its carrying amount. If the carrying amount of an intangible asset exceeds its fair value, an impairment loss is recognized in an amount equal to that excess. We consider many factors in evaluating whether the value of our intangible assets with indefinite lives may not be recoverable, including, but not limited to, expected growth rates, the cost of equity and debt capital, general economic conditions, our outlook and market performance of our industry and recent and forecasted financial performance. ​ We evaluate indefinite-lived intangible assets for impairment at least annually on October 1 and whenever facts and circumstances indicate that their carrying amounts may not be recoverable. For the nine months ended September 30, 2022, the Company determined that there was no impairment to IPR&D .
Concentration of Credit Risk	Concentration of Credit Risk ​ Financial instruments that subject the Company to credit risk primarily consist of cash and cash equivalents. The Company’s credit risk is managed by investing in highly rated money market instruments, U.S. treasury bills, corporate bonds, commercial paper and/or other debt securities. Due to these factors, no significant additional credit risk is believed by management to be inherent in the Company’s assets. As of September 30, 2022, all the Company’s cash and cash equivalents were held at five high credit-quality financial institutions.
Operating Lease Right-of-Use Asset and Lease Liability	Operating Lease Right-of-Use Assets and Lease Liability ​ The Company accounts for leases under ASC 842, Leases. Operating leases are included in “Operating lease right-of-use assets” within the Company’s consolidated balance sheets and represent the Company’s right to use an underlying asset for the lease term. The Company’s related obligation to make lease payments are included in “Operating lease liability” and “Operating lease liability, net of current portion” within the Company’s consolidated balance sheets. Operating lease right-of-use (“ROU”) assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rates, which are the rates incurred to borrow on a collateralized basis over a similar term, an amount equal to the lease payments in a similar economic environment. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The ROU assets are tested for impairment according to ASC 360, Property, Plant, and Equipmen ​ As of September 30, 2022 and December 31, 2021, the Company’s operating lease ROU assets and corresponding short-term and long-term lease liabilities primarily relate to its existing Exton, PA facility operating lease which expires on May 31, 2025. In connection with the Aceragen Acquisition, as defined and described in Note 4, the Company acquired an operating lease for an office in Basel, Switzerland which expires on March 31, 2023.
Acquisition-Related Costs	Acquisition-Related Costs ​ Acquisition-related costs include direct expenses incurred in connection with the Acquisition of Aceragen as well as integration-related professional fees and other incremental costs directly associated to the acquisition.
Restructuring and Other Charges	Restructuring and Other Charges ​ The Company accounts for exit or disposal activities in accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 420, Exit or Disposal Cost Obligations (“ASC 420”). A business restructuring is defined as an exit or disposal activity that includes, but is not limited to, a program that is planned and controlled by management and materially changes either the scope of a business or the manner in which that business is conducted. Business restructuring charges include (i) one-time termination benefits related to employee separations (i.e. severance costs), (ii) contract termination costs, and (iii) other related costs associated with exit or disposal activities. In the third quarter of 2022, the Company implemented a restructuring plan to streamline the organization, reduce costs, and direct resources to advance the Company’s primary operating goals. ​ The Company recognizes and measures a liability for one-time termination benefits, for which no future service is required, once the plan of termination meets all of the following criteria for an established communication date: (i) management commits to a plan of termination, (ii) the plan identifies the number of employees to be terminated and their job classifications or functions, locations and the expected completion date, (iii) the plan establishes the terms of the benefit arrangement, and (iv) it is unlikely that significant changes to the plan will be made or the plan will be withdrawn. For one-time termination benefits for which future service is required, a liability is measured at the communication date based on its value as of the termination date and recognized ratably over the future service period. The Company recognizes and measures a liability for other related costs in the period in which the liability is incurred.
Series X Preferred Stock Liability	Series X Preferred Stock Liability ​ In conjunction with the Acquisition of Aceragen, the Company evaluated the newly issued Series X preferred stock and determined its revised terms represents a sale of future revenues and is classified as a liability under ASC 470, Debt and the Company has elected to account for the Series X preferred stock liability under the fair value option. The fair value of the Series X preferred stock liability represents the present value of estimated future payments, including royalty payments, as well as estimated payments that are contingent upon the achievement of specified milestones. The fair value of the Series X preferred stock liability is based on the cumulative probability of the various estimated payments. The fair value measurement is based on significant Level 3 unobservable inputs such as the probability of achieving the milestones, anticipated timelines, probability and timing of an early redemption of all obligations under Series X preferred liability and the discount rate. Any changes in the fair value of the liability in each reporting period are recognized in the consolidated statement of operations until it is settled.
Warrant Liability	Warrant Liability ​ In connection with the Aceragen Acquisition, a portion of the consideration paid to Aceragen warrant holders was in the form of warrants to purchase shares of Series Z (the “Series Z warrants”). The Series Z warrants were classified as a liability on the condensed consolidated balance sheet at September 30, 2022 because the underlying Series Z are contingently redeemable. The fair value of the Series Z warrants on the date of issuance was recorded as a component to the carrying value of the shares Series Z and as a long-term liability in the condensed consolidated balance sheet. The warrants are remeasured to fair value at each balance sheet date until the warrants are exercised, reclassified, expire or otherwise settled. Changes in the fair values of the Series Z warrants are recognized as other income or expense in the consolidated statements of operations and comprehensive loss. ​ The Company used the Black-Scholes option pricing model, which incorporated assumptions and estimates, to value the Series Z warrants. Estimates and assumptions impacting the fair value measurement of the Series Z warrants included the remaining contractual term of the warrants, risk-free interest rate, expected dividend yield and expected volatility of the price of the underlying shares of Series Z. The estimated the expected stock volatility based on the Company’s historical volatility for a term equal to the remaining contractual term of the warrants at the time of issuance and again at the remeasurement date. The risk-free interest rate was determined by reference to the US Treasury yield curve for time periods approximately equal to the remaining contractual term of the warrants. Expected dividend yield was determined based on the fact that the Company had never paid cash dividends and did not expect to pay any cash dividends in the foreseeable future.
Redeemable Preferred Stock	R edeemable Preferred Stock ​ The Company applies ASC 480 when determining the classification and measurement of its preferred stock. Preferred shares subject to mandatory redemption are classified as liability instruments and are measured at fair value. Conditionally redeemable preferred shares (including preferred shares that feature redemption rights that are either within the control of the holder or subject to redemption upon the occurrence of uncertain events not solely within the Company’s control) are classified as temporary equity. At all other times, preferred shares are classified as stockholders’ equity. ​ The carrying value of the shares of Series Z is accreted to redemption value using the estimated fair value of the redemption value at each reporting period until the redeemable convertible preferred stock cease to be outstanding or the redemption right has expired. ​ The accretion for the three and nine months ended September 30, 2022 was immaterial.
Revenue Recognition	Revenue Recognition ​ The Company recognizes revenue when the Company's customers obtain control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services by analyzing the following five steps: (i) identify the contract with a customer(s); (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. ​ Revenues from reimbursable contracts are recognized as costs are incurred, generally based on allowable direct costs incurred during the period, plus allocable overheads together with any recognizable earned fee. The Company uses this input method to measure progress as the customer has access to the development research under these projects and benefits incrementally as R&D activities occur.
Income Taxes	Income Taxes ​ In accordance with ASC 270, Interim Reporting Income Taxes ​
New Accounting Pronouncements	New Accounting Pronouncements ​ From time to time, new accounting pronouncements are issued by the FASB and rules are issued by the SEC that the Company has or will adopt as of a specified date. Unless otherwise noted, management does not believe that any other recently issued accounting pronouncements issued by the FASB or guidance issued by the SEC had, or is expected to have, a material impact on the Company’s present or future consolidated financial statements. ​ Recently Adopted Accounting Pronouncements 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 (“ASU 2020-06”), which simplifies the guidance on an issuer’s accounting for convertible instruments and contracts in its own equity. The Company adopted ASU 2020-06 in the first quarter of 2021. The adoption of ASU 2020-06 did not have a material effect on the Company’s consolidated financial statements.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2022
Fair Value Measurements
Schedule of assets and liabilities measured and recorded in financial statements at fair value on a recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2022 (In thousands) ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 4,680 ​ $ 4,680 ​ $ — ​ $ — ​ Cash equivalents – money market funds ​ ​ 22,115 ​ ​ 22,115 ​ ​ — ​ ​ — ​ Total assets ​ $ 26,795 ​ $ 26,795 ​ $ — ​ $ — ​ Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Warrant liability ​ $ 3,750 ​ $ — ​ $ — ​ $ 3,750 ​ Series X preferred stock liability ​ ​ 20,400 ​ ​ — ​ ​ — ​ ​ 20,400 ​ Total liabilities ​ $ 24,150 ​ $ — ​ $ — ​ $ 24,150 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2021 ​ (In thousands) ​ Total ​ Level 1 ​ Level 2 ​ Level 3 ​ Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 250 ​ $ 250 ​ $ — ​ $ — ​ Cash equivalents – money market funds ​ ​ 32,295 ​ ​ 32,295 ​ ​ — ​ ​ — ​ Total assets ​ $ 32,545 ​ $ 32,545 ​ $ — ​ $ — ​
Schedule of reconciliation measured at fair value on a recurring basis using unobservable inputs	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (In thousands) ​ ​ Balance, December 31, 2021 $ — Issuance in connection with Acquisition of Aceragen ​ ​ 3,866 Change in fair value ​ ​ (116) Balance, September 30, 2022 $ 3,750

Business Acquisition (Tables)

Business Acquisition (Tables)	9 Months Ended
	Sep. 30, 2022
Business Acquisition
Schedule of purchase price consideration	​ ​ ​ ​ ​ (In thousands) ​ Common stock issued to Aceragen stockholders ​ $ 1,672 Series Z issued to Aceragen stockholders (Note 9) ​ 26,971 Series X liability in connection with Aceragen Acquisition (Note 8) ​ ​ 20,400 Stock options, restricted stock and warrants allocated to consideration paid ​ 6,670 Total Consideration paid ​ $ 55,713
Summary of preliminary allocation of the purchase price to the assets acquired and liabilities assumed	​ ​ ​ ​ ​ (In thousands) ​ ​ ​ Assets acquired: ​ ​ ​ Cash, cash equivalents and restricted cash ​ $ 5,482 Receivables ​ 1,914 Prepaid expenses and other assets ​ ​ 575 In-process research and development assets ​ 63,067 Goodwill ​ 9,934 ​ ​ $ 80,972 Liabilities assumed: ​ ​ ​ Accounts Payable and accrued expenses ​ $ 7,827 Acquisition Obligation (Note 7) ​ 7,476 Operating lease liabilities ​ ​ 22 Deferred tax liabilities ​ ​ 9,934 ​ ​ $ 25,259 ​ ​ ​ ​ Net assets acquired ​ $ 55,713
Schedule of pro forma financial information	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ Nine Months Ended (In thousands) ​ September 30, ​ ​ September 30, ​ 2022 ​ 2021 ​ 2022 ​ 2021 Net revenues ​ $ 3,865 ​ $ 79 ​ $ 13,334 ​ $ 79 Net (loss) income ​ $ (10,229) ​ $ (2,982) ​ $ (27,646) ​ $ 100,723

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2022
Property and Equipment
Schedule of net property and equipment at cost	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ (In thousands) 2022 2021 Leasehold improvements ​ $ 107 ​ $ 107 ​ Equipment and other ​ 712 ​ 712 ​ Total property and equipment, at cost ​ $ 819 ​ $ 819 ​ Less: Accumulated depreciation and amortization ​ 808 ​ 797 ​ Property and equipment, net ​ $ 11 ​ $ 22 ​ ​ ​

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2022
Accrued Expenses
Schedule of accrued expenses	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, (In thousands) ​ 2022 2021 Payroll and related costs ​ $ 1,467 ​ $ 477 ​ Clinical and nonclinical trial expenses ​ 2,289 ​ 2,909 ​ Professional and consulting fees ​ 1,216 ​ 591 ​ Restructuring and other costs (Note 12) ​ 2,660 ​ — ​ Acquisition-related costs ​ ​ 2,826 ​ ​ — ​ Other ​ 233 ​ 111 ​ Total accrued expenses ​ $ 10,691 ​ $ 4,088 ​

Acquisition Obligation (Tables)

Acquisition Obligation (Tables)	9 Months Ended
	Sep. 30, 2022
Acquisition Obligation
Schedule of acquisition obligation	​ ​ ​ ​ ​ (In thousands) Amounts 2022 ​ $ 1,534 2023 ​ ​ 5,942 Total ​ $ 7,476

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2022
Stockholders' Equity
Schedule of warrants outstanding and exercisable for purchase of common stock	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number of Shares ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ Weighted-Average ​ ​ ​ Description ​ 2022 ​ 2021 ​ Exercise Price ​ Expiration Date ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity-classified warrants ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ May 2013 warrants 15,437 ​ 15,437 ​ ​ $ 0.08 ​ None ​ September 2013 warrants 4,096 ​ 4,096 ​ ​ $ 0.08 ​ None ​ February 2014 warrants 2,171 ​ 2,171 ​ ​ $ 0.08 ​ None ​ April 2020 Private Placement first closing warrants ​ 3,039,514 ​ 3,039,514 ​ ​ $ 2.28 ​ Apr 2023 ​ April 2020 Private Placement second closing warrants ​ 1,373,626 ​ 1,373,626 ​ ​ $ 2.71 ​ Dec 2023 ​ April 2020 Private Placement second closing warrants ​ — ​ 1,143,428 ​ ​ $ 0.01 ​ None ​ July 2020 Private Placement first closing warrants ​ — ​ 389,731 ​ ​ $ 0.01 ​ None ​ July 2020 Private Placement first closing warrants ​ 2,764,227 ​ 2,764,227 ​ ​ $ 2.58 ​ Jul 2023 ​ ​ ​ 7,199,071 ​ 8,732,230 ​ ​ ​ ​ ​ ​ Liability-classified warrants ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Aceragen Acquisition warrants: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Convertible to common stocks ​ 1,353,143 ​ — ​ ​ $ 0.46 ​ 3/23/2031 ​ Convertible to preferred stocks ​ 14,215 ​ — ​ ​ $ 460.00 ​ 3/23/2031 ​ ​ ​ 1,367,358 ​ — ​ ​ ​ ​ ​ ​ Total outstanding 8,566,429 ​ 8,732,230 ​ ​ ​ ​ ​ ​

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2022
Stock-Based Compensation
Schedule of stock-based compensation expense attributable to share-based payments made to employees and directors and included in operating expenses	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ September 30, ​ September 30, (in thousands) ​ 2022 2021 ​ 2022 2021 Stock-based compensation: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Research and development ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee Stock Purchase Plan ​ $ 6 $ 7 ​ $ 21 $ 22 Equity Incentive Plan ​ ​ 53 ​ 51 ​ ​ 194 ​ 469 ​ ​ $ 59 $ 58 ​ $ 215 $ 491 General and administrative ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee Stock Purchase Plan ​ $ 2 $ — ​ $ 5 $ 3 Equity Incentive Plan ​ ​ 350 ​ 417 ​ ​ 1,298 ​ 1,496 ​ ​ $ 352 $ 417 ​ $ 1,303 $ 1,499 Total stock-based compensation expense ​ $ 411 $ 475 ​ $ 1,518 $ 1,990
Schedule of weighted average assumptions applied to options	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2022 2021 Average risk-free interest rate ​ 2.6% ​ ​ 0.4% ​ Expected dividend yield ​ ​ — ​ ​ — ​ Expected lives (years) ​ 3.8 ​ ​ 3.6 ​ Expected volatility ​ 104% ​ ​ 94% ​ Weighted average exercise price (per share) ​ $ 0.49 ​ $ 2.68 ​
Schedule of information related to outstanding and exercisable options	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ($ in thousands, except per share data) ​ Common Stock Options ​ Weighted-Average Exercise Price ​ Weighted-Average Remaining Contractual Life (in years) ​ Aggregate Intrinsic Value Outstanding at December 31, 2021 5,202,006 ​ $ 8.06 5.9 ​ $ 2,949 ​ Granted 1,169,800 ​ ​ 0.49 ​ ​ ​ ​ ​ ​ Exercised — ​ ​ — ​ ​ ​ ​ ​ ​ Forfeited — ​ ​ — ​ ​ ​ ​ ​ ​ Expired (588,038) ​ ​ 2.87 ​ ​ ​ ​ ​ ​ Options assumed in connection with Aceragen Acquisition ​ 1,887,860 ​ ​ 4.15 ​ 9.3 ​ ​ ​ ​ Outstanding at September 30, 2022 7,671,628 ​ $ 6.34 ​ 7.3 ​ $ — ​ Exercisable at September 30, 2022 4,218,823 ​ $ 9.29 ​ 5.7 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Preferred Stock Options ​ Weighted-Average Exercise Price ​ Weighted-Average Remaining Contractual Life (in years) ​ ​ Aggregate Intrinsic Value Outstanding at December 31, 2021 — ​ $ — ​ — ​ ​ — ​ Options assumed in connection with Aceragen Acquisition ​ 19,826 ​ ​ 394.82 ​ 9.3 ​ ​ ​ ​ Outstanding at September 30, 2022 19,826 ​ $ 394.82 ​ 9.3 ​ $ — ​ Exercisable at September 30, 2022 2,187 ​ $ 142.05 ​ 8.9 ​ $ — ​
Schedule of information related to restricted stock activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Time-based Awards ​ Market/Performance-based Awards ($ in thousands, except per share data) ​ Number of Shares ​ Weighted-Average Grant Date Fair Value ​ Number of Shares ​ Weighted-Average Grant Date Fair Value Nonvested shares at December 31, 2021 68,675 ​ $ 2.30 ​ 507,028 ​ $ 1.54 Granted 283,207 ​ 0.40 ​ — ​ — Cancelled — ​ — ​ — ​ — Vested (27,212) ​ 2.43 ​ — ​ — Nonvested shares at September 30, 2022 324,670 ​ $ 0.63 ​ 507,028 ​ $ 1.54

Net Income (Loss) per Common _2

Net Income (Loss) per Common Share (Tables)	9 Months Ended
	Sep. 30, 2022
Net Income (Loss) per Common Share
Computation of basic and diluted net income (loss) per share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ($ in thousands except per share data) ​ ​ 2022 ​ ​ 2021 ​ ​ 2022 ​ ​ 2021 Net (loss) income per share — Basic: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net (loss) income ​ $ (3,099) ​ $ (5,965) ​ $ (12,584) ​ $ 102,210 Less: Undistributed earnings to preferred stockholders ​ ​ — ​ ​ — ​ ​ ​ ​ ​ (1,636) Net (loss) income applicable to common stockholders - basic ​ $ (3,099) ​ $ (5,965) ​ $ (12,584) ​ $ 100,574 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Numerator for basic net (loss) income applicable to common stockholders ​ $ (3,099) ​ $ (5,965) ​ $ (12,584) ​ $ 100,574 Denominator for basic net (loss) income applicable to common stockholders ​ ​ 53,286 ​ ​ 52,740 ​ ​ 53,052 ​ ​ 47,990 Net (loss) income applicable to common stockholders - basic ​ $ (0.06) ​ $ (0.11) ​ $ (0.24) ​ $ 2.10 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net (loss) income per share — Diluted: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net (loss) income ​ $ (3,099) ​ $ (5,965) ​ $ (12,584) ​ $ 102,210 Less: Warrant revaluation gain applicable to dilutive liability-classified warrants ​ ​ — ​ ​ — ​ ​ — ​ ​ (6,983) Less: Future tranche right revaluation gain applicable to dilutive liability-classified future tranche rights ​ ​ — ​ ​ — ​ ​ — ​ ​ (118,803) Numerator for diluted net (loss) income applicable to common stockholders ​ $ (3,099) ​ $ (5,965) ​ $ (12,584) ​ $ (23,576) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator for basic net (loss) income applicable to common stockholders ​ ​ 53,286 ​ ​ 52,740 ​ ​ 53,052 ​ ​ 47,990 Plus: Incremental shares underlying “in the money” liability-classified warrants outstanding ​ ​ — ​ ​ — ​ ​ — ​ ​ 223 Plus: Incremental shares underlying “in the money” liability-classified future tranche rights outstanding ​ ​ — ​ ​ — ​ ​ — ​ ​ 3,400 Denominator for diluted net income (loss) applicable to common stockholders ​ ​ 53,286 ​ ​ 52,740 ​ ​ 53,052 ​ ​ 51,613 Net (loss) income applicable to common stockholders - diluted ​ $ (0.06) ​ $ (0.11) ​ $ (0.24) ​ $ (0.46)
Schedule of potentially dilutive securities excluded from diluted net income (loss) per common share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, (in thousands) ​ ​ 2022 ​ ​ 2021 ​ ​ 2022 ​ ​ 2021 Stock options ​ ​ 5,783 ​ ​ 5,329 ​ ​ 5,783 ​ ​ 5,329 Restricted stock units ​ ​ 832 ​ ​ 576 ​ ​ 832 ​ ​ 576 Common stock warrants ​ ​ 8,566 ​ ​ 8,732 ​ ​ 8,566 ​ ​ 8,732 Total ​ ​ 15,181 ​ ​ 14,637 ​ ​ 15,181 ​ ​ 14,637

Business and Organization (Deta

Business and Organization (Details) - USD ($) $ / shares in Units, $ in Thousands	May 26, 2022	Sep. 30, 2022	Dec. 31, 2021	[1]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Accumulated deficit		$ 748,045	$ 735,461
Cash, cash equivalents and investments		26,800
Debt obligation initial payment		6,000
Additional compliance period	180 days
Number of consecutive business days considered for minimum closing bid price	10 days
Goodwill or other intangible assets		$ 9,934
Series Z convertible preferred stock
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Temporary equity, preferred stock, par value		$ 0.01
[1] The condensed consolidated balance sheet at December 31, 2021 has been derived from the audited financial statements at that date.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2022 USD ($) Institution	Dec. 31, 2021 USD ($)
Summary of Significant Accounting Policies
Unbilled accounts receivable	$ 1,100	$ 1,100
Number of financial institutions | Institution		5
Tax expense (benefit)	(6,039)	$ (6,039)
Uncertain tax positions	$ 0	0	$ 0
Change in deferred tax valuation allowance		6,000
IPR&D
Summary of Significant Accounting Policies
Impairment of intangible assets		$ 0

Fair Value Measurements - Trans

Fair Value Measurements - Transfers Between Levels (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2022 USD ($)
Fair Value Measurements
Fair value of assets transfers from level 1 to level 2	$ 0
Fair value of assets transfers from level 2 to level 1	0
Fair value of liabilities transfers from level 1 to level 2	0
Fair value of liabilities transfers from level 2 to level 1	0
Fair value of assets transfers into level 3	0
Fair value of assets transfers out of level 3	0
Fair value of liabilities transfers into level 3	0
Fair value of liabilities transfers out of level 3	$ 0

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Assets	$ 26,795	$ 32,545
Total Liabilities	24,150
Warrant liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Liabilities	3,750
Issuance in connection with Acqusition of Aceragen, Inc.	3,866
Series X preferred stock liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Liabilities	20,400
Cash
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents - money market funds	4,680	250
Money market funds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents - money market funds	22,115	32,295
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Assets	26,795	32,545
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Cash
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents - money market funds	4,680	250
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Money market funds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents - money market funds	22,115	$ 32,295
Significant Unobservable Inputs (Level 3)
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Liabilities	24,150
Significant Unobservable Inputs (Level 3) | Warrant liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Liabilities	3,750
Significant Unobservable Inputs (Level 3) | Series X preferred stock liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Liabilities	$ 20,400

Fair Value Measurements - Ass_2

Fair Value Measurements - Assets and Liabilities at Fair Value Changes in Level 3 Liabilities (Details) - Fair Value, Measurements, Recurring - Warrant liability $ in Thousands	9 Months Ended
	Sep. 30, 2022 USD ($)
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Issuance in connection with Acqusition of Aceragen, Inc.	$ 3,866
Change in the fair value of liability (1)	(116)
Ending balance	$ 3,750

Business Acquisition - Addition

Business Acquisition - Additional Information (Details) - USD ($)		3 Months Ended		9 Months Ended
	Sep. 28, 2022	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Business Acquisition [Line Items]
Preferred stock, par value		$ 0.01		$ 0.01		$ 0.01
Acquisition-related costs		$ 2,836,000		$ 2,836,000
Nonrecurring pro forma transaction costs		7,800,000	$ 0	7,800,000	$ 0
Payment of success fee				3,400,000
Severance costs				800,000
Restructuring costs		2,802,000	$ 130,000	2,802,000	$ 1,322,000
Tax expense (benefit)		$ (6,039,000)		$ (6,039,000)
Series X preferred stock
Business Acquisition [Line Items]
Preferred stock, par value	$ 0.01
Aceragen
Business Acquisition [Line Items]
Acquisition-related costs	$ 2,800,000
Fair value of total consideration	$ 55,700,000
Aceragen | Merger Agreement
Business Acquisition [Line Items]
Outstanding security interests percentage	100%
Number of share acquisitions	4,398,762
Aceragen | Series Z convertible preferred stock | Merger Agreement
Business Acquisition [Line Items]
Shares issued during the acquisitions	$ 80,656
Conversion of common stock	1,000
Aceragen | Series X preferred stock | Merger Agreement
Business Acquisition [Line Items]
Number of share acquisitions	5

Business Acquisition - Purchase

Business Acquisition - Purchase price consideration (Details) - USD ($) $ in Thousands		9 Months Ended
	Sep. 28, 2022	Sep. 30, 2022
Stock options, restricted stock and warrants
Business Acquisition
Stock issued		$ 6,670
Total Consideration paid		55,713
Series Z convertible preferred stock | Stock options, restricted stock and warrants
Business Acquisition
Stock issued		26,971
Series X preferred stock | Stock options, restricted stock and warrants
Business Acquisition
Stock issued		20,400
Aceragen
Business Acquisition
Total Consideration paid	$ 55,700
Aceragen | Stock options, restricted stock and warrants
Business Acquisition
Stock issued		$ 1,672

Business Acquisition - Allocati

Business Acquisition - Allocation of the purchase price to the assets acquired and liabilities assumed (Details) $ in Thousands	Sep. 30, 2022 USD ($)
Assets acquired:
Goodwill	$ 9,934
Aceragen
Assets acquired:
Cash, cash equivalents and restricted cash	5,482
Receivables	1,914
Prepaid expenses and other assets	575
In-process research and development assets	63,067
Goodwill	9,934
Total assets acquired	80,972
Liabilities assumed:
Accounts Payable and accrued expenses	7,827
Acquisition Obligation (Note 7)	7,476
Operating lease liabilities	22
Deferred tax liabilities	9,934
Total liabilities assumed	25,259
Net assets acquired	$ 55,713

Business Acquisition - Pro Form

Business Acquisition - Pro Forma Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Business Acquisition
Net revenues	$ 3,865	$ 79	$ 13,334	$ 79
Net (loss) income	$ (10,229)	$ (2,982)	$ (27,646)	$ 100,723

Property and Equipment - Net Pr

Property and Equipment - Net Property and Equipment at Cost (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Property, Plant and Equipment
Total property and equipment, at cost	$ 819	$ 819
Less: Accumulated depreciation and amortization	808	797
Property and equipment, net	11	22	[1]
Leasehold improvements
Property, Plant and Equipment
Total property and equipment, at cost	107	107
Equipment and other
Property, Plant and Equipment
Total property and equipment, at cost	$ 712	$ 712
[1] The condensed consolidated balance sheet at December 31, 2021 has been derived from the audited financial statements at that date.

Property and Equipment - Deprec

Property and Equipment - Depreciation and Amortization Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Property, Plant and Equipment
Non-cash property additions	$ 0	$ 0	$ 0	$ 0
Maximum
Property, Plant and Equipment
Depreciation and amortization expense on property and equipment	$ 100	$ 100	$ 100	$ 100

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Accrued Expenses
Payroll and related costs	$ 1,467	$ 477
Clinical and nonclinical trial expenses	2,289	2,909
Professional and consulting fees	1,216	591
Restructuring and other costs (Note 12)	2,660
Acquisition-related costs	2,826
Other	233	111
Total accrued expenses	$ 10,691	$ 4,088	[1]
[1] The condensed consolidated balance sheet at December 31, 2021 has been derived from the audited financial statements at that date.

Acquisition Obligation (Details

Acquisition Obligation (Details) $ in Thousands	Sep. 30, 2022 USD ($)
Business Acquisition
Aggregate future payment	$ 7,476
Acquisition obligation, net	1,534
Acquisition obligation, net	5,942
Aceragen
Business Acquisition
Aggregate future payment	7,500
Acquisition obligation, net	6,000
Acquisition obligation, net	1,500
Fair value of acquisition obligation	7,500
Deferred acquisition obligation	$ 6,000
Annual interest rate	12%

Acquisition Obligation - Debt (

Acquisition Obligation - Debt (Details) $ in Thousands	Sep. 30, 2022 USD ($)
Debt obligation
2022	$ 1,534
2023	5,942
Total	$ 7,476

Series X Preferred Stock Liab_2

Series X Preferred Stock Liability (Details)	9 Months Ended
	Sep. 30, 2022 shares
Series X preferred stock | Aceragen
Stock issued (in shares)	5

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock (Details) - USD ($)		1 Months Ended	9 Months Ended
	Dec. 23, 2019	Dec. 31, 2019	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Redeemable Convertible Preferred Stock
Aggregate gross proceeds	$ 3,900,000
Shares authorized (in shares)		140,000,000	140,000,000		140,000,000
Gross proceeds		$ 6,200,000
Series B1 convertible preferred stock
Redeemable Convertible Preferred Stock
Sale of redeemable convertible preferred stock	23,684			23,684
Series B1 convertible preferred stock | Common stock warrants
Redeemable Convertible Preferred Stock
Warrant to purchase stock	2,368,400
Warrant exercised price (per share)	$ 1.52
Series B1 convertible preferred stock | Preferred Stock Warrant
Redeemable Convertible Preferred Stock
Warrant to purchase stock	23,684
Warrant exercised price (per share)	$ 152
Series B2 convertible preferred stock
Redeemable Convertible Preferred Stock
Aggregate gross proceeds	$ 15,000,000
Preferred shares	98,685
Series B2 convertible preferred stock | Common stock warrants
Redeemable Convertible Preferred Stock
Warrant to purchase stock	9,868,500
Warrant exercised price (per share)	$ 1.52
Series B2 convertible preferred stock | Preferred Stock Warrant
Redeemable Convertible Preferred Stock
Warrant to purchase stock	98,685
Warrant exercised price (per share)	$ 152
Series B3 convertible preferred stock
Redeemable Convertible Preferred Stock
Aggregate gross proceeds	$ 15,000,000
Preferred shares	82,418
Series B3 convertible preferred stock | Common stock warrants
Redeemable Convertible Preferred Stock
Warrant to purchase stock	6,593,440
Warrant exercised price (per share)	$ 1.82
Series B3 convertible preferred stock | Preferred Stock Warrant
Redeemable Convertible Preferred Stock
Warrant to purchase stock	65,934
Warrant exercised price (per share)	$ 182
Series B4 convertible preferred stock
Redeemable Convertible Preferred Stock
Aggregate gross proceeds	$ 15,000,000
Preferred shares	82,418
Expiration period	21 months
Series B4 convertible preferred stock | Common stock warrants
Redeemable Convertible Preferred Stock
Warrant to purchase stock	6,593,440
Warrant exercised price (per share)	$ 1.82
Series B4 convertible preferred stock | Preferred Stock Warrant
Redeemable Convertible Preferred Stock
Warrant to purchase stock	65,934
Warrant exercised price (per share)	$ 182
Series Z Redeemable Convertible Preferred Stock
Redeemable Convertible Preferred Stock
Conversion of common stock			1,000
Series Z Redeemable Convertible Preferred Stock | Aceragen
Redeemable Convertible Preferred Stock
Shares issued during the acquisitions			$ 80,656

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock (Details) - USD ($) $ / shares in Units, $ in Millions				1 Months Ended	9 Months Ended		30 Months Ended
	Jul. 13, 2020	Apr. 07, 2020	Mar. 04, 2019	Nov. 30, 2018	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022
April 2020 Private Placement Second Closing
Class of Stock
Ownership percentage		19.99%
"At-The-Market" Equity Program
Class of Stock
Stock issued (in shares)					0	5,117,357
Percentage of fixed commission expense of gross proceeds of shares sold in ATM agreement				3%
Net proceeds from offering of common stock				$ 50		$ 15.3
Maximum value of shares that are permitted to be sold, subject to certain limitations					$ 19.5
Lincoln Park Capital Fund, LLC ("Investor")
Class of Stock
Value of shares which may be sold			$ 35
Duration over which common stock purchase agreement may be sold			36 months
Stock issued (in shares)			269,749			800,000
Stock issued (per share)			$ 2.84
Net proceeds from offering of common stock						$ 4.2
April 2020 Private Placement
Class of Stock
Stock issued (in shares)		3,039,514
Warrant exercised price (per share)		$ 2.28
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any		$ 5
Combined purchase price (per share)		$ 1.645
Stock price underlying warrants (per share)		$ 0.125
Shares of common stock that may be purchased upon exercise of warrants		3,039,514
April 2020 Private Placement Second Closing
Class of Stock
Stock issued (in shares)		2,747,252
Warrant exercised price (per share)		$ 2.71
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any		$ 5
Stock price (in dollars per share)		$ 0.01
Shares of common stock that may be purchased upon exercise of warrants		1,373,626
April 2020 Private Placement and April 2020 Private Placement Second Closing in Aggregate
Class of Stock
Net proceeds from offering of common stock							$ 9.8
July 2020 Private Placement Second Closing
Class of Stock
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	$ 5.1
July 2020 Private Placement Second Closing | Pre-funded Warrants
Class of Stock
Stock issued (in shares)	784,615
Stock price (in dollars per share)	$ 0.01
July 2020 Private Placement Second Closing | Warrants
Class of Stock
Warrant exercised price (per share)	$ 9.75
Shares of common stock that may be purchased upon exercise of warrants	274,615

Stockholders' Equity - Common_2

Stockholders' Equity - Common Stock Warrants (Details) - $ / shares	Sep. 30, 2022	Dec. 31, 2021
Class of Warrant or Right
Number of Shares	8,566,429	8,732,230
Liability Classified Warrants
Class of Warrant or Right
Number of Shares	1,367,358
Aceragen Acquisition Closing Warrants: Convertible to common stocks
Class of Warrant or Right
Number of Shares	1,353,143
Weighted-Average Exercise Price	$ 0.46
Aceragen Acquisition Closing Warrants: Convertible to preferred stocks
Class of Warrant or Right
Number of Shares	14,215
Weighted-Average Exercise Price	$ 460
Equity Classified Warrants
Class of Warrant or Right
Number of Shares	7,199,071	8,732,230
May 2013 Warrants
Class of Warrant or Right
Number of Shares	15,437	15,437
Weighted-Average Exercise Price	$ 0.08
September 2013 Warrants
Class of Warrant or Right
Number of Shares	4,096	4,096
Weighted-Average Exercise Price	$ 0.08
February 2014 Warrants
Class of Warrant or Right
Number of Shares	2,171	2,171
Weighted-Average Exercise Price	$ 0.08
April 2020 Private Placement first closing warrants
Class of Warrant or Right
Number of Shares	3,039,514	3,039,514
Weighted-Average Exercise Price	$ 2.28
April 2020 Private Placement second closing warrants
Class of Warrant or Right
Number of Shares	1,373,626	1,373,626
Weighted-Average Exercise Price	$ 2.71
April 2020 Private Placement second closing warrants
Class of Warrant or Right
Number of Shares		1,143,428
Weighted-Average Exercise Price	0.01
July 2020 Private Placement first closing warrants
Class of Warrant or Right
Number of Shares		389,731
Weighted-Average Exercise Price	$ 0.01
July 2020 Private Placement first closing warrants
Class of Warrant or Right
Number of Shares	2,764,227	2,764,227
Weighted-Average Exercise Price	$ 2.58

Collaboration and License Agr_2

Collaboration and License Agreements (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Feb. 28, 2021	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Research and development		$ 1,470	$ 3,507	$ 5,960	$ 14,271
Scriptr Global, Inc. | Research and Development Plans and Designation of Development Candidates
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Research and development		$ 100	$ 400	$ 500	$ 1,700
Scriptr Global, Inc. | Maximum | Research and Development Plans and Designation of Development Candidates
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Research period	270 days
Deferred revenue recognition period	270 days

Restructuring and Other Costs (

Restructuring and Other Costs (Details) $ in Thousands		3 Months Ended			9 Months Ended
	Sep. 28, 2022 position	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 position	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)
Restructuring costs
Restructuring costs		$ 2,802	$ 130		$ 2,802	$ 1,322
Restructuring and other costs (Note 12)		2,660			2,660
Employee Severance and Benefits
Restructuring costs
Restructuring costs		2,800	$ 100		2,800
Employee Severance and Benefits | 2022 reduction-in-workforce
Restructuring costs
Number of positions eliminated | position	5
Percentage of positions eliminated	38%
Employee Severance and Benefits | 2021 reduction-in-workforce
Restructuring costs
Number of positions eliminated | position				16
Percentage of positions eliminated				50%
Employee Severance and Benefits | Accrued Liabilities
Restructuring costs
Restructuring and other costs (Note 12)		2,700			2,700
Employee Severance and Benefits | Other liabilities
Restructuring costs
Long-term portion of the accrued restructuring balance		$ 100			$ 100

Stock-Based Compensation - Equi

Stock-Based Compensation - Equity Incentive and Employee Stock Purchase Plans (Details) $ in Millions	9 Months Ended
	Sep. 30, 2022 USD ($) shares
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average remaining period over which unrecognized compensation expense will be recognized	2 years 4 months 24 days
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average remaining period over which unrecognized compensation expense will be recognized	1 year
Stock-based compensation expense	$ 0.1
Assumed Aceragen Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum term of options granted	10 years
Unrecognized compensation expense	$ 4.7
Weighted average remaining period over which unrecognized compensation expense will be recognized	3 years 9 months
Forfeited | shares	3,278,859
Assumed Aceragen Stock Incentive Plan | Stock options | Employee option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee option vesting percentage	25%
Vesting period	3 years
Assumed Aceragen Stock Incentive Plan | Stock options | Non-employee Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	2 years
Assumed Aceragen Stock Incentive Plan | Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average remaining period over which unrecognized compensation expense will be recognized	2 years
Unrecognized compensation expense related to the restricted stock units	$ 0.7

Stock-Based Compensation - Eq_2

Stock-Based Compensation - Equity Incentive Plans (Details) - shares		9 Months Ended
	Jun. 23, 2022	Sep. 30, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding under earlier plans		145,968
Grant of inducement stock option		325,000
2013 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional number of shares reserved for issuance	4,600,000
Common stock, shares reserved for future issuance	10,253,057
Common shares available for grant		3,806,601
Common stock options outstanding		5,312,800
Restricted stock units outstanding		831,698
Maximum number of additional common shares	155,968

Stock-Based Compensation - Empl

Stock-Based Compensation - Employee Stock Purchase Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from employee stock purchases	$ 43	$ 48
Percentage of share-based compensation expense	15%
Weighted average grant date fair value of options granted during the period (per share)	$ 0.35	$ 1.54
2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of additional common shares	600,000
Common stock shares authorized for issuance under stock purchase plan	1,012,500
Common shares available for grant	683,788
Common stock share issued	112,437	29,016
Maximum | 2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from employee stock purchases	$ 100	$ 100

Stock-Based Compensation - Acco

Stock-Based Compensation - Accounting for Stock-based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	$ 411	$ 475	$ 1,518	$ 1,990
Research and development
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	59	58	215	491
Research and development | Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	6	7	21	22
Research and development | Equity Incentive Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	53	51	194	469
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	352	417	1,303	1,499
General and administrative | Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	2		5	3
General and administrative | Equity Incentive Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	$ 350	$ 417	$ 1,298	$ 1,496

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions Used in Determining Fair Value of Stock Options (Details) - $ / shares	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Stock-Based Compensation
Options to purchase common stock granted to employees and directors	1,169,800	1,356,700
Average risk free interest rate	2.60%	0.40%
Dividend rate	0%	0%
Expected lives (years)	3 years 9 months 18 days	3 years 7 months 6 days
Expected volatility	104%	94%
Weighted average exercise price (per share)	$ 0.49	$ 2.68

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended		12 Months Ended
	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award
Granted, Weighted Average Exercise Price		$ 0.49	$ 2.68
Share based compensation arrangement by share based payment award options, annual accelerate percentage of options vested		6.25%
Share based compensation arrangement by share based payment award options, percentage of options vested every year		25%
Stock options
Share-based Compensation Arrangement by Share-based Payment Award
Accelerated vesting, number of shares	1,535,578
Unrecognized compensation cost related to nonvested stock-based compensation		$ 1,000
Weighted average remaining period over which unrecognized compensation expense will be recognized		2 years 4 months 24 days
Common Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Options, Outstanding, Beginning Balance		5,202,006
Granted		1,169,800
Expired		(588,038)
Options assumed in connection with Aceragen Acquisition		1,887,860
Options, Outstanding, Ending Balance		7,671,628		5,202,006
Exercisable, Ending Balance		4,218,823
Weighted Average Exercise Price, Beginning Balance		$ 8.06
Granted, Weighted Average Exercise Price		0.49
Expired, Weighted Average Exercise Price		2.87
Options assumed in connection with Aceragen Acquisition, Weighted Average Exercise Price		4.15
Weighted Average Exercise Price, Ending Balance		6.34		$ 8.06
Exercisable, Weighted Average Exercise Price		$ 9.29
Options assumed in connection with Aceragen acquisition, Weighted Average Remaining Contractual Term		9 years 3 months 18 days
Outstanding, Ending balance, Weighted Average Remaining Contractual Term		7 years 3 months 18 days		5 years 10 months 24 days
Exercisable Ending Balance, Weighted Average Remaining Contractual Term		5 years 8 months 12 days
Outstanding, Intrinsic Value, Ending Balance				$ 2,949
Preferred Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Options assumed in connection with Aceragen Acquisition		19,826
Options, Outstanding, Ending Balance		19,826
Exercisable, Ending Balance		2,187
Options assumed in connection with Aceragen Acquisition, Weighted Average Exercise Price		$ 394.82
Weighted Average Exercise Price, Ending Balance		394.82
Exercisable, Weighted Average Exercise Price		$ 142.05
Options assumed in connection with Aceragen acquisition, Weighted Average Remaining Contractual Term		9 years 3 months 18 days
Outstanding, Ending balance, Weighted Average Remaining Contractual Term		9 years 3 months 18 days
Exercisable Ending Balance, Weighted Average Remaining Contractual Term		8 years 10 months 24 days

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended			9 Months Ended
	Jul. 31, 2020	Sep. 30, 2022	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Restricted Stock Activity, Weighted-Average Grant Date Fair Value
Share-based compensation		$ 411	$ 475		$ 1,518	$ 1,990
2013 Stock Incentive Plan
Restricted Stock Activity, Number of Shares
Nonvested shares, Ending Balance		831,698			831,698
Restricted Stock Activity, Weighted-Average Grant Date Fair Value
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant		3,806,601			3,806,601
Restricted stock units
Restricted Stock Activity, Number of Shares
Nonvested shares, Beginning Balance					68,675
Granted					283,207
Vested					(27,212)
Nonvested shares, Ending Balance		324,670			324,670
Restricted Stock Activity, Weighted-Average Grant Date Fair Value
Nonvested shares, Weighted Average Grant Date Fair Value, Beginning Balance					$ 2.30
Granted, Weighted-Average Grant Date Fair Value					0.40
Vested, Weighted-Average Grant Date Fair Value					2.43
Nonvested shares, Weighted Average Grant Date Fair Value, Ending Balance		$ 0.63			$ 0.63
Accelerated vesting, number of shares				137,872
Recognized compensation expense					$ 100
Unrecognized compensation expense		$ 200			$ 200
Weighted average remaining period over which unrecognized compensation expense will be recognized					1 year
Market/Performance-based Awards
Restricted Stock Activity, Number of Shares
Nonvested shares, Beginning Balance					507,028
Nonvested shares, Ending Balance		507,028			507,028
Restricted Stock Activity, Weighted-Average Grant Date Fair Value
Nonvested shares, Weighted Average Grant Date Fair Value, Beginning Balance					$ 1.54
Nonvested shares, Weighted Average Grant Date Fair Value, Ending Balance		$ 1.54			$ 1.54
Weighted average remaining period over which unrecognized compensation expense will be recognized					2 months 12 days
Requisite service period (in years)	2 years 4 months 9 days
Share-based compensation					$ 100
Unrecognized compensation expense related to the restricted stock units		$ 100			100
Additional compensation expense as a result of meeting certain achievements					$ 300

Related Party Transactions - Ov

Related Party Transactions - Overview of Related Parties (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Related Party Transactions
Board fees paid in stock in lieu of director board and committee fees	$ 0.1	$ 0.1
Common stock issued in lieu of board fees	149,757	68,699
Pillar Investment Entities
Related Party Transactions
Ownership percentage of new company	19.99%
Pillar Investment Entities
Related Party Transactions
Equity method investment beneficial ownership percentage	16%
Exercise price of warrants	$ 0.01	$ 0.01
Issuance of common stock upon exercise of warrants (in shares)	1,533,159	3,158,386
Cashless shares		19,052
Pillar Investment Entities | Maximum
Related Party Transactions
Proceeds from exercise of warrants	$ 0.1	$ 0.1
Pillar Investment Entities | Warrant, Tranche One
Related Party Transactions
Number of Shares	3,039,514
Exercise price of warrants	$ 2.28
Pillar Investment Entities | Warrant, Tranche Two
Related Party Transactions
Number of Shares	2,764,227
Exercise price of warrants	$ 2.58
Pillar Investment Entities | Warrant, Tranche Three
Related Party Transactions
Number of Shares	1,373,626
Exercise price of warrants	$ 2.71

Net Income (Loss) per Common _3

Net Income (Loss) per Common Share -Computation of basic and diluted net income per common share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Net (loss) income per share - Basic:
Net (loss) income	$ (3,099)	$ (5,307)	$ (4,178)	$ (5,965)	$ (7,563)	$ 115,738	$ (12,584)	$ 102,210
Less: Undistributed earnings to preferred stockholders								(1,636)
Net (loss) income applicable to common stockholders - basic	(3,099)			(5,965)			(12,584)	100,574
Numerator for basic net (loss) income applicable to common stockholders	$ (3,099)			$ (5,965)			$ (12,584)	$ 100,574
Denominator for basic net (loss) income applicable to common stockholders	53,286			52,740			53,052	47,990
Net (loss) income applicable to common stockholders - basic	$ (0.06)			$ (0.11)			$ (0.24)	$ 2.10
Net (loss) income per share - Diluted:
Less: Warrant revaluation gain applicable to dilutive liability-classified warrants								$ (6,983)
Less: Future tranche right revaluation gain applicable to dilutive liability-classified future tranche rights								(118,803)
Numerator for diluted net (loss) income applicable to common stockholders	$ (3,099)			$ (5,965)			$ (12,584)	$ (23,576)
Denominator for basic net (loss) income applicable to common stockholders	53,286			52,740			53,052	47,990
Plus: Incremental shares underlying "in the money" liability-classified warrants outstanding								223
Plus: Incremental shares underlying "in the money" liability-classified future tranche rights outstanding								3,400
Denominator for diluted net income (loss) applicable to common stockholders	53,286			52,740			53,052	51,613
Net (loss) income applicable to common stockholders - diluted	$ (0.06)			$ (0.11)			$ (0.24)	$ (0.46)

Net Income (Loss) per Common _4

Net Income (Loss) per Common Share - Antidilutive securities (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Antidilutive securities
Total antidilutive securities	15,181	14,637	15,181	14,637
Stock options
Antidilutive securities
Total antidilutive securities	5,783	5,329	5,783	5,329
Restricted stock units
Antidilutive securities
Total antidilutive securities	832	576	832	576
Common stock warrants
Antidilutive securities
Total antidilutive securities	8,566	8,732	8,566	8,732