Rubius Therapeutics (RUBY) 10-Q 9 Nov 20 2020 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Oct. 30, 2020
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Sep. 30, 2020
Entity File Number	001-38586
Entity Registrant Name	RUBIUS THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-2688109
Entity Address, Address Line One	399 Binney Street
Entity Address, Address Line Two	Suite 300
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02139
City Area Code	617
Local Phone Number	679-9600
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	RUBY
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		80,923,945
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001709401
Amendment Flag	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 75,174	$ 91,898
Investments	132,730	191,389
Prepaid expenses and other current assets	6,458	5,979
Total current assets	214,362	289,266
Operating lease, right-of-use-asset	41,483	46,559
Property, plant and equipment, net	54,635	56,924
Restricted cash	1,573	1,735
Other assets	311	357
Total assets	312,364	394,841
Current liabilities:
Accounts payable	9,135	7,178
Accrued expenses and other current liabilities	11,143	16,042
Operating lease liabilities	9,719	10,540
Total current liabilities	29,997	33,760
Long-term debt, net of discount	74,828	49,596
Other long-term liabilities	884	405
Operating lease liabilities, net of current portion	33,540	36,867
Total liabilities	139,249	120,628
Commitments and contingencies (see Note 9)
Stockholders' equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized at September 30, 2020 and December 31, 2019; no shares issued or outstanding at September 30, 2020 and December 31, 2019
Common stock, $0.001 par value; 150,000,000 shares authorized at September 30, 2020 and December 31, 2019; 80,923,820 and 80,016,245 shares issued and outstanding at September 30, 2020 and December 31, 2019, respectively	81	80
Additional paid-in capital	612,934	586,798
Accumulated other comprehensive income	32	75
Accumulated deficit	(439,932)	(312,740)
Total stockholders' equity	173,115	274,213
Total liabilities and stockholders' equity	$ 312,364	$ 394,841

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2020	Dec. 31, 2019
CONDENSED CONSOLIDATED BALANCE SHEETS
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, share authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, share authorized (in shares)	150,000,000	150,000,000
Common stock, shares issued (in shares)	80,923,820	80,016,245
Common stock, shares outstanding (in shares)	80,923,820	80,016,245

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Revenue
Operating expenses:
Research and development	28,209	33,530	90,491	81,919
General and administrative	11,976	14,952	36,241	42,254
Total operating expenses	40,185	48,482	126,732	124,173
Loss from operations	(40,185)	(48,482)	(126,732)	(124,173)
Other income (expense):
Interest income	223	2,002	1,682	6,492
Interest expense	(1,174)	(835)	(2,987)	(1,957)
Other income, net	284	300	845	652
Total other income (expense), net	(667)	1,467	(460)	5,187
Net loss	$ (40,852)	$ (47,015)	$ (127,192)	$ (118,986)
Net loss per share, basic and diluted	$ (0.51)	$ (0.59)	$ (1.58)	$ (1.52)
Weighted average common shares outstanding, basic and diluted	80,778,042	79,115,305	80,511,543	78,357,791
Comprehensive loss:
Net loss	$ (40,852)	$ (47,015)	$ (127,192)	$ (118,986)
Other comprehensive income (loss):
Unrealized gains (losses) on investments, net of tax of $0	(162)	(124)	(43)	195
Comprehensive loss	$ (41,014)	$ (47,139)	$ (127,235)	$ (118,791)

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Unrealized gains (losses) on investments, tax	$ 0	$ 0	$ 0	$ 0

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net loss	$ (127,192)	$ (118,986)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	24,725	30,440
Depreciation and amortization expense	5,176	2,294
Amortization (accretion) of premium (discount) on investments	186	(1,939)
Loss on disposal of property and equipment		119
Non-cash interest expense	232	201
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(1,318)	(2,129)
Operating lease, right-of-use-asset	4,184	3,336
Other assets	(5)	(293)
Accounts payable	2,095	3,184
Accrued expenses and other current liabilities	(2,425)	3,330
Other long-term liabilities	580	395
Operating lease liabilities	(3,338)	(1,411)
Net cash used in operating activities	(97,100)	(81,459)
Cash flows from investing activities:
Purchases of property, plant and equipment	(4,467)	(27,381)
Purchases of investments	(122,671)	(259,231)
Sales and maturities of investments	181,102	143,275
Net cash provided by (used in) investing activities	53,964	(143,337)
Cash flows from financing activities:
Proceeds from borrowings under loan and security agreement	25,000	25,000
Repurchase of unvested restricted common stock		(122)
Proceeds from issuance of common stock upon exercise of stock options	1,412	1,843
Net cash provided by financing activities	26,412	26,721
Net decrease in cash, cash equivalents and restricted cash	(16,724)	(198,075)
Cash, cash equivalents and restricted cash at beginning of period	93,633	309,421
Cash, cash equivalents and restricted cash at end of period	76,909	111,346
Supplemental cash flow information:
Cash paid for interest, net of interest capitalized	2,740	1,706
Cash paid for leases	5,822	3,194
Lease assets obtained in exchange for new operating lease liabilities	90	49,496
Lease asset derecognized upon lease cancellation	982
Supplemental disclosure of non-cash investing and financing information:
Purchases of property, plant and equipment included in accounts payable or accrued expenses	$ 564	6,073
Deferred offering costs and issuance costs included in accounts payable or accrued expenses		$ 11

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common stock	Additional paid-in capital	Accumulated other comprehensive income (loss)	Accumulated deficit	Total
Balances at Beginning of period (in shares) at Dec. 31, 2018	79,234,853
Balances at Beginning of period at Dec. 31, 2018	$ 79	$ 543,040	$ (29)	$ (150,082)	$ 393,008
Issuance of common stock upon exercise of stock options (in shares)	619,342
Issuance of common stock upon exercise of stock options	$ 1	798			799
Stock-based compensation expense		9,478			9,478
Vesting of restricted common stock		22			22
Unrealized gains (losses) on investments			110		110
Net loss				(32,581)	(32,581)
Balances at End of period (in shares) at Mar. 31, 2019	79,854,195
Balances at End of period at Mar. 31, 2019	$ 80	553,338	81	(181,863)	371,636
Balances at Beginning of period (in shares) at Dec. 31, 2018	79,234,853
Balances at Beginning of period at Dec. 31, 2018	$ 79	543,040	(29)	(150,082)	393,008
Net loss					(118,986)
Balances at End of period (in shares) at Sep. 30, 2019	79,777,733
Balances at End of period at Sep. 30, 2019	$ 80	575,365	166	(268,268)	307,343
Balances at Beginning of period (in shares) at Dec. 31, 2018	79,234,853
Balances at Beginning of period at Dec. 31, 2018	$ 79	543,040	(29)	(150,082)	393,008
Net loss					(163,500)
Balances at End of period (in shares) at Dec. 31, 2019	80,016,245
Balances at End of period at Dec. 31, 2019	$ 80	586,798	75	(312,740)	274,213
Cumulative effect adjustment for adoption of ASC 842				800	800
Balances at Beginning of period (in shares) at Mar. 31, 2019	79,854,195
Balances at Beginning of period at Mar. 31, 2019	$ 80	553,338	81	(181,863)	371,636
Issuance of common stock upon exercise of stock options (in shares)	223,484
Issuance of common stock upon exercise of stock options		572			572
Stock-based compensation expense		10,604			10,604
Vesting of restricted common stock		13			13
Unrealized gains (losses) on investments			209		209
Net loss				(39,390)	(39,390)
Balances at End of period (in shares) at Jun. 30, 2019	80,077,679
Balances at End of period at Jun. 30, 2019	$ 80	564,527	290	(221,253)	343,644
Issuance of common stock upon exercise of stock options (in shares)	367,971
Issuance of common stock upon exercise of stock options	$ 1	471			472
Stock-based compensation expense		10,358			10,358
Repurchase of unvested restricted common stock (in shares)	(667,917)
Repurchase of unvested restricted common stock	$ (1)				(1)
Vesting of restricted common stock		9			9
Unrealized gains (losses) on investments			(124)		(124)
Net loss				(47,015)	(47,015)
Balances at End of period (in shares) at Sep. 30, 2019	79,777,733
Balances at End of period at Sep. 30, 2019	$ 80	575,365	166	(268,268)	307,343
Balances at Beginning of period (in shares) at Dec. 31, 2019	80,016,245
Balances at Beginning of period at Dec. 31, 2019	$ 80	586,798	75	(312,740)	274,213
Issuance of common stock upon exercise of stock options (in shares)	413,721
Issuance of common stock upon exercise of stock options		486			486
Stock-based compensation expense		8,488			8,488
Unrealized gains (losses) on investments			456		456
Net loss				(48,486)	(48,486)
Balances at End of period (in shares) at Mar. 31, 2020	80,429,966
Balances at End of period at Mar. 31, 2020	$ 80	595,772	531	(361,226)	235,157
Balances at Beginning of period (in shares) at Dec. 31, 2019	80,016,245
Balances at Beginning of period at Dec. 31, 2019	$ 80	586,798	75	(312,740)	274,213
Net loss					(127,192)
Balances at End of period (in shares) at Sep. 30, 2020	80,923,820
Balances at End of period at Sep. 30, 2020	$ 81	612,934	32	(439,932)	173,115
Balances at Beginning of period (in shares) at Mar. 31, 2020	80,429,966
Balances at Beginning of period at Mar. 31, 2020	$ 80	595,772	531	(361,226)	235,157
Issuance of common stock upon exercise of stock options (in shares)	115,553
Issuance of common stock upon exercise of stock options		256			256
Stock-based compensation expense		8,252			8,252
Unrealized gains (losses) on investments			(337)		(337)
Net loss				(37,854)	(37,854)
Balances at End of period (in shares) at Jun. 30, 2020	80,545,519
Balances at End of period at Jun. 30, 2020	$ 80	604,280	194	(399,080)	205,474
Issuance of common stock upon exercise of stock options (in shares)	378,301
Issuance of common stock upon exercise of stock options	$ 1	669			670
Stock-based compensation expense		7,985			7,985
Unrealized gains (losses) on investments			(162)		(162)
Net loss				(40,852)	(40,852)
Balances at End of period (in shares) at Sep. 30, 2020	80,923,820
Balances at End of period at Sep. 30, 2020	$ 81	$ 612,934	$ 32	$ (439,932)	$ 173,115

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2020
Nature of the Business and Basis of Presentation
Nature of the Business and Basis of Presentation	1. Nature of the Business and Basis of Presentation Rubius Therapeutics, Inc. (“Rubius” or the “Company”) is a therapeutics company focused on using its platform to develop red cell therapeutics for the treatment of patients with severe diseases. Rubius was incorporated in April 2013 as VL26, Inc. under the laws of the State of Delaware. In January 2015, the Company changed its name to Rubius Therapeutics, Inc. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations, the ability to establish clinical- and commercial-scale manufacturing processes and the ability to secure additional capital to fund operations. In addition, the Company is subject to uncertainty regarding the performance and safety of red cell therapeutics in humans. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s drug development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. T he Company is monitoring the potential impact of the novel coronavirus (“COVID-19”), if any, on the carrying value of certain assets. To date, the Company has not experienced material business disruption, nor has it incurred impairment of any assets as a result of COVID-19. The extent to which these events may impact the Company’s business will depend on future developments, which are highly uncertain and cannot be predicted at this time. The duration and intensity of these impacts and resulting disruption to the Company’s operations is uncertain and the Company will continue to assess the financial impact. On July 20, 2018, the Company completed its initial public offering (“IPO”), pursuant to which it issued and sold 12,055,450 shares of common stock, inclusive of 1,572,450 shares sold by the Company pursuant to the full exercise of the underwriters’ option to purchase additional shares. The aggregate net proceeds received by the Company from the IPO were $254.3 million, after deducting underwriting discounts and commissions and other offering costs. Upon the closing of the IPO, all of the shares of the Company’s outstanding convertible preferred stock then outstanding automatically converted into 51,845,438 shares of common stock. The accompanying condensed consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. The Company has incurred recurring losses since inception, including net losses of $127.2 million for the nine months ended September 30, 2020 and $163.5 million for the year ended December 31, 2019. As of September 30, 2020, the Company had an accumulated deficit of $439.9 million. The Company expects to continue to generate operating losses in the foreseeable future. As of November 9, 2020, the issuance date of the interim condensed consolidated financial statements, the Company expects that its cash, cash equivalents and investments will be sufficient to fund its operating expenses and capital expenditure requirements for at least 12 months from the issuance date of the interim condensed consolidated financial statements. The Company will seek additional funding through private or public equity financings, debt financings, collaborations, strategic alliances and marketing, distribution or licensing arrangements. The Company may not be able to obtain financing on acceptable terms, or at all, and the Company may not be able to enter into collaborations or other arrangements. The terms of any financing may adversely affect the holdings or the rights of the Company's stockholders. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects. Although management continues to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all. The Company’s condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary. All intercompany accounts and transactions have been eliminated in consolidation. Certain prior period amounts have been reclassified to conform to the current year presentation.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2020
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Unaudited Interim Financial Information The condensed consolidated balance sheet at December 31, 2019 was derived from audited financial statements but does not include all disclosures required by GAAP. The accompanying unaudited condensed consolidated financial statements as of September 30, 2020 and for the three and nine months ended September 30, 2020 and 2019 have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) for interim financial statements. Certain information and footnote disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. These condensed consolidated financial statements should be read in conjunction with the Company’s audited condensed consolidated financial statements and the notes thereto for the year ended December 31, 2019 included in the Company’s Annual Report on Form 10-K for the year-ended December 31, 2019, on file with the SEC. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair statement of the Company’s condensed consolidated financial position as of September 30, 2020 and condensed consolidated results of operations for the three and nine months ended September 30, 2020 and 2019 and the condensed consolidated cash flows for the nine months ended September 30, 2020 and 2019 have been made. The Company’s condensed consolidated results of operations for the three and nine months ended September 30, 2020 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2020. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, the accrual of research and development expenses, the valuation of common stock prior to the IPO and the valuation of stock-based awards. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates as there are changes in circumstances, facts and experience. ​ The full extent to which the COVID-19 pandemic will directly or indirectly impact our business, results of operations and financial condition, including clinical trials, research and development costs and employee-related amounts, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain it or treat COVID-19. ​ Concentrations of Credit Risk and of Significant Suppliers Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and investments. The Company’s cash, cash equivalents and investments, as of September 30, 2020, consisted of U.S. government money market funds, U.S. government treasury bills and U.S. government treasury notes. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. The Company relies, and expects to continue to rely, on a small number of vendors to manufacture supplies and raw materials for its development programs. These programs could be adversely affected by a significant interruption in these manufacturing services or the availability of raw materials. Cash Equivalents The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents. Restricted Cash As of both September 30, 2020 and December 31, 2019, the Company maintained letters of credit totaling $1.7 million for the benefit of the landlords of its leased properties. The Company was required to maintain separate cash balances of these amounts to secure the letters of credit. Related to these separate cash balances, the Company included $0.1 million in prepaid Cash, cash equivalents and restricted cash presented in the accompanying condensed consolidated statement of cash flows was $76.9 million and $111.3 million for the nine months ended September 30, 2020 and 2019, respectively, of which $1.7 million and $1.7 million was restricted cash, respectively. Fair Value Measurements Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: ● Level 1—Quoted prices in active markets for identical assets or liabilities. ● Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. ● Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. The Company’s cash equivalents and investments are carried at fair value, determined according to the fair value hierarchy described above (see Note 3). The carrying values of the Company’s accounts payable and accrued expenses approximate their fair values due to the short-term nature of these liabilities. The carrying value of the Company’s long-term debt approximates its fair value due to its variable interest rate, which approximates a market interest rate. Investments The Company’s investments are classified as available-for-sale and are carried at fair value. Realized gains and losses and declines in value are based on the specific identification method and are included as a component of other income (expense), net in the condensed consolidated statements of operations and comprehensive loss. The Company classifies its investments with maturities beyond one year as short-term, based on their highly liquid nature and because such investments are available for current operations. In June 2016, issued 2016-13, Financial Instruments - Credit Losses (Topic 326), Measurement of Credit Losses , which changes the impairment model for most financial assets, including the Company’s investments. The Company adopted the standard effective January 1, 2020 using a prospective transition method. The Company evaluates its investments with unrealized losses for impairment. When assessing investments for unrealized declines in value, the Company considers whether the decline in value is related to a credit loss or non-credit loss. For credit losses, the Company reduces the investment to fair value through an allowance for credit losses recorded to the balance sheet and corresponding charge to the statement of operations. The allowance for credit losses and corresponding impairment charge is adjusted each period for changes in fair value. For non-credit losses, the Company reduces the investment to fair value through a charge to the statement of comprehensive loss, reported as a component of accumulated other comprehensive income (loss) in stockholders’ equity. No such adjustments were necessary during the periods presented. Leases At the inception of an arrangement as lessee or lessor, the Company determines whether the arrangement is or contains a lease. Operating lease cost is recognized over the lease term on a straight-line basis. Variable lease cost and short-term leases (lease terms less than 12 months) are recognized as incurred. For both lessee and lessor arrangements, variable lease payments are the amounts owed by the Company to a lessor that are not fixed, such as reimbursement for common area maintenance and utilities costs, and are expensed when incurred. When determining the lease term, the Company includes options to extend or terminate the lease when it is reasonably certain that it will exercise that option. For lessee arrangements, operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected lease term. The interest rate implicit in lease contracts is typically not readily determinable. As such, the Company utilizes its incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. Certain adjustments to the right-of-use asset may be required for items such as initial direct costs paid or incentives received. Operating leases are recognized on the balance sheet as right-of-use assets, operating lease liabilities current and operating lease liabilities non-current. The Company has elected the following lease policies at the inception of a lease: (1) for lessee and lessor arrangements within all asset classes, combine lease and non-lease components as a single component, with the lease expense recognized over the expected term on a straight-line basis and (2) for lessee arrangements, apply short-term lease exemption for all leases that qualify, where a right-of-use asset or lease liability will not be recognized for leases with terms of one year or less. ​ Recently Adopted Accounting Pronouncements ASU No. 2016-02, Leases In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) ASU 2016-02 initially required adoption using a modified retrospective approach, under which all years presented in the financial statements would be prepared under the revised guidance. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842) The Company adopted ASC 842 using the modified retrospective approach with an effective date of January 1, 2019 for leases that existed on that date. Prior period results continue to be presented under ASC 840 based on the accounting standards originally in effect for such periods. This standard provides a number of optional practical expedients in transition. The Company applied the package of practical expedients to leases that commenced prior to the effective date, whereby it elected not to reassess the following: (i) whether any expired or existing contracts contain leases; (ii) the lease classification for any expired or existing leases; and (iii) initial direct costs for any existing leases. The Company elected the short-term lease recognition exemption for all leases that qualify, where a right-of-use asset or lease liability will not be recognized for short term leases that have terms of one year or less. The most significant effects of adoption were the recognition of material new right-of-use assets and corresponding liabilities on its condensed consolidated balance sheet related to its existing facility operating leases. In addition, the Company has a material lease where the Company was deemed the owner during the construction period and for which the construction was not complete as of January 1, 2019. The Company took control of the leased space during the first quarter of 2019 at which time the lease commenced. Under ASC 842, as the commencement date of this material lease had not occurred, the new right-of-use assets and corresponding liabilities related to this lease were not recognized on the condensed consolidated balance sheet as of date of adoption, January 1, 2019, however, were recognized upon the commencement date of January 28, 2019. The adoption of this standard has had a material impact on the Company’s financial position but did not significantly affect the Company’s results of operations. ASU No. 2018-15, Intangibles–Goodwill and Other–Internal-Use Software In August 2018, the FASB issued ASU No. 2018-15, Intangibles–Goodwill and Other–Internal-Use Software (Topic 350): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract. ASU No. 2016-13, Financial Instruments—Credit Losses In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments. The standard amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses for most financial assets and certain other instruments that aren’t measured at fair value through net income. For available-for-sale debt securities, entities are required to recognize an allowance for credit losses rather than a reduction in carrying value of the asset. Entities are no longer permitted to consider the length of time that fair value has been less than amortized cost when evaluating when credit losses should be recognized. ASU No. 2018-13, Fair Value Measurement In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement 2020 on a prospective basis. The adoption did not have an impact on the Company’s condensed consolidated financial statements. ASU No. 2020-04, Reference Rate Reform In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting ​ Recently Issued Accounting Pronouncements ASU No. 2019-12, Simplifying the Accounting for Income Taxes In December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for Income Taxes (ASC 740).

Investments and Fair Value of F

Investments and Fair Value of Financial Assets and Liabilities	9 Months Ended
	Sep. 30, 2020
Investments and Fair Value of Financial Assets and Liabilities
Investments and Fair Value of Financial Assets and Liabilities	3. Investments and Fair Value of Financial Assets and Liabilities Investments by security type consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ ​ Amortized Cost ​ Gross ​ Gross ​ Credit Losses ​ Fair Value U.S. treasury bills and notes (due within one year) $ 132,698 $ 43 $ (11) ​ $ — ​ $ 132,730 ​ ​ $ 132,698 ​ $ 43 ​ $ (11) ​ $ — ​ $ 132,730 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 ​ ​ Amortized Cost ​ Gross ​ Gross ​ Fair Value U.S. treasury bills and notes (due within one year) $ 189,816 $ 91 $ (20) ​ $ 189,887 U.S. government agency bonds (due within one year) ​ 1,498 ​ 4 ​ — ​ 1,502 ​ ​ $ 191,314 ​ $ 95 ​ $ (20) ​ $ 191,389 ​ The following tables present the Company’s fair value hierarchy for its assets and liabilities, which are measured at fair value on a recurring basis (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurements at September 30, 2020 using: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Level 1 Level 2 Level 3 Total Assets: ​ ​ ​ ​ ​ Cash equivalents: ​ ​ ​ ​ ​ Money market funds $ 68,916 $ — $ — ​ $ 68,916 Investments: ​ ​ ​ ​ ​ ​ ​ U.S. treasury bills and notes ​ — ​ 132,730 ​ — ​ 132,730 ​ ​ $ 68,916 ​ $ 132,730 ​ $ — ​ $ 201,646 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurements at December 31, 2019 using: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Level 1 Level 2 Level 3 Total Assets: ​ ​ ​ ​ ​ Cash equivalents: ​ ​ ​ ​ ​ Money market funds $ 91,898 $ — $ — ​ $ 91,898 Investments: ​ ​ ​ ​ U.S. government agency bonds ​ — ​ 1,502 ​ — ​ 1,502 U.S. treasury bills and notes ​ — ​ 189,887 ​ — ​ 189,887 ​ ​ $ 91,898 ​ $ 191,389 ​ $ — ​ $ 283,287 ​ U.S. government money market funds were valued by the Company based on quoted market prices, which represent a Level 1 measurement within the fair value hierarchy. U.S. treasury notes and U.S. government agency bonds were valued by the Company using quoted prices in active markets for similar securities, which represent a Level 2 measurement within the fair value hierarchy. There have been no changes to the valuation methods during the nine months ended September 30, 2020. The Company evaluates transfers between levels at the end of each reporting period. There were no transfers between Level 1, Level 2 or Level 3 during the nine months ended September 30, 2020.

Property, Plant and Equipment,

Property, Plant and Equipment, Net	9 Months Ended
	Sep. 30, 2020
Property, Plant and Equipment, Net.
Property, Plant and Equipment, Net	4. Property, Plant and Equipment, Net Property, plant and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 December 31, 2019 Manufacturing facility ​ $ 30,539 ​ $ — Manufacturing equipment ​ ​ 8,685 ​ ​ — Land ​ ​ 1,300 ​ ​ 1,300 Laboratory equipment ​ 16,210 ​ ​ 16,079 Computer equipment 2,028 ​ 1,051 Furniture and fixtures ​ ​ 1,228 ​ ​ 1,228 Leasehold improvements 445 ​ 445 Construction-in-progress 2,866 ​ 41,262 ​ 63,301 ​ 61,365 Less: Accumulated depreciation and amortization (8,666) ​ (4,441) ​ ​ $ 54,635 ​ $ 56,924 ​ Manufacturing Facility On July 31, 2018, the Company completed its purchase of a 135,000 square foot manufacturing facility located in Smithfield, Rhode Island for a purchase price of $8.0 million. In August 2018, the Company began renovations to customize this facility to manufacture clinical supply of its product candidates. Of the total purchase price, $1.3 million was allocated to the value of land acquired based on the value of comparable assets, and $6.7 million was allocated to construction in progress, as the building was not ready for its intended use. During the years ended December 31, 2019 and 2018, the Company capitalized, as construction-in-progress, the design, demolition, construction and interest costs related to the renovation project, as well as costs for manufacturing equipment to be used in the facility. In January 2020, after achieving the regulatory qualifications required to bring it to its intended use, the Company placed the manufacturing facility and manufacturing equipment into service. In connection with placing the manufacturing facility into service, $30.5 million and $7.8 million of c onstruction progress

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	9 Months Ended
	Sep. 30, 2020
Accrued Expenses and Other Current Liabilities
Accrued Expenses and Other Current Liabilities	5. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 December 31, 2019 Accrued employee compensation and benefits $ 5,511 ​ $ 5,045 Accrued external research and development expenses 3,686 ​ 6,715 Accrued manufacturing facility expenses 369 ​ 2,824 Accrued general and administrative expenses ​ ​ 1,462 ​ ​ 1,136 Other 115 ​ 322 ​ ​ $ 11,143 ​ $ 16,042 ​

Debt

Debt	9 Months Ended
	Sep. 30, 2020
Debt
Debt	6. Debt On December 21, 2018 (the “Closing Date”), the Company entered into a loan and security agreement (the “Loan Agreement”) with Solar Capital Ltd. as collateral agent for the lenders party thereto for an aggregate principal amount of $75.0 million. The aggregate principal amount will be funded in three tranches of term loans of $25.0 million each. On the Closing Date, the Company made an initial borrowing of $25.0 million. In June 2019, the Company made a second borrowing of $25.0 million. In June 2020, the Company made a third and final borrowing of $25.0 million. Interest on the outstanding loan balance will accrue at a rate of the one-month U.S. LIBOR rate plus 5.50%. Monthly principal payments will commence 36 months after the Closing Date and will be amortized over the following 24 months. Certain backend fees are due to the lender at the time of final repayment based on the total funded term loans. The Company accrues the backend fees that will be due at final repayment to outstanding debt by charges to interest expense over the term of the loans using the effective-interest method. The term loans are subject to a prepayment fee of 1.00% in the first year, 0.50% in the second year and 0.25% in the third year. In conjunction with 2018 Credit Facility, the Company incurred issuance costs of $0.8 million. The Loan Agreement contains financial covenants that require the Company to maintain either a certain minimum cash balance or a minimum market capitalization threshold. The Company was in compliance with all such covenants as of September 30, 2020. The Loan Agreement contains customary representations, warranties and covenants and also includes customary events of default, including payment defaults, breaches of covenants, change of control and a material adverse change default. Upon the occurrence of an event of default, a default interest rate of an additional 4.00% per annum may be applied to the outstanding loan balances, and the lenders may declare all outstanding obligations immediately due and payable. Borrowings under the Loan Agreement are collateralized by substantially all of the Company’s assets, other than its intellectual property. ​ ​ ​ ​ As of September 30, 2020, the estimated future principal payments due were as follows (in thousands): ​ ​ ​ ​ Year ending December 31, ​ 2020 (three months ending December 31) ​ $ — 2021 ​ — 2022 ​ ​ 37,500 2023 ​ ​ 37,500 2024 and thereafter ​ ​ — ​ ​ $ 75,000 ​

Equity

Equity	9 Months Ended
	Sep. 30, 2020
Equity
Equity	7. Equity On July 20, 2018, the Company filed a restated certificate of incorporation in the State of Delaware, which, among other things, restated the number of shares of all classes of stock that the Company has authority to issue to 160,000,000 shares, consisting of (i) 150,000,000 shares of common stock, $0.001 par value per share, and (ii) 10,000,000 shares of preferred stock, $0.001 par value per share. The preferred stock will have such rights, preferences, privileges and restrictions, including voting rights, dividend rights, conversion rights, redemption privileges and liquidation preferences, as shall be determined by the Company’s board of directors upon issuance. The shares of preferred stock are currently undesignated. Also on July 20, 2018, the Company completed its IPO, pursuant to which it issued and sold 12,055,450 shares of common stock, inclusive of 1,572,450 shares sold by the Company pursuant to the full exercise of the underwriters’ option to purchase additional shares. The aggregate net proceeds received by the Company from the IPO were $254.3 million, after deducting underwriting discounts and commissions and other offering costs. Upon the closing of the IPO, all of the shares of the Company’s outstanding convertible preferred stock then outstanding automatically converted into 51,845,438 shares of common stock. On August 1, 2019, the Company entered into a Distribution Agreement (the “Distribution Agreement”) with J.P. Morgan Securities LLC, Jefferies LLC and SVB Leerink LLC (the “Sales Agents”), pursuant to which the Company may issue and sell, from time to time, shares of its common stock having an aggregate offering price of up to $100.0 million through the Sales Agents. The Company’s registration statement on Form S-3 filed on August 1, 2019 was declared effective on August 21, 2019. The Sales Agents may sell common stock by any method permitted by law deemed to be an “at the market offering” as defined in Rule 415(a)(4) of the Securities Act of 1933, as amended, including sales made directly on or through the Nasdaq Global Select Market or any other existing trade market for the common stock, in negotiated transactions at market prices prevailing at the time of sale or at prices related to prevailing market prices, or any other method permitted by law. The Sales Agents will be entitled to receive 3.0% of the gross sales price per share of common stock sold pursuant to the Distribution Agreement. As of September 30, 2020, no shares of common stock have been issued and sold pursuant to the Distribution Agreement.

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2020
Stock-Based Compensation
Stock-Based Compensation	8. Stock-Based Compensation Service-Based Stock Options During the nine months ended September 30, 2020, the Company granted options with service-based vesting conditions for the purchase of 3,738,221 shares of common stock with a weighted average exercise price of $7.44 per share and a weighted average grant-date fair value of $4.62 per share. Stock-Based Compensation The Company recorded stock-based compensation expense in the following expense categories of its condensed consolidated statements of operations and comprehensive loss (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2020 2019 2020 2019 Research and development expenses ​ $ 1,996 ​ $ 2,195 $ 6,165 ​ $ 6,798 General and administrative expenses ​ 5,989 ​ 8,163 ​ 18,560 ​ 23,642 ​ ​ $ 7,985 ​ $ 10,358 ​ $ 24,725 ​ $ 30,440 ​ As of September 30, 2020, total unrecognized compensation cost related to the unvested stock-based awards was $52.5 million, which is expected to be recognized over a weighted average period of 1.9 years.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies
Commitments and Contingencies	9. Commitments and Contingencies License Agreement with the Whitehead Institute for Biomedical Research The Company has a license agreement with the Whitehead Institute for Biomedical Research (“WIBR”), as amended, under which the Company has been granted an exclusive, sublicensable, nontransferable license under certain patent families related to the development of the Company’s red cell therapies (the “WIBR License”). The Company is obligated to pay WIBR annual license maintenance fees of less than $0.1 million, as well as patent-related costs, including legal fees, and low single-digit royalties based on annual net sales of licensed products and licensed services by the Company and its sublicensees. Based on the progress the Company makes in the advancement of products covered by the licensed patent rights, the Company is required to make aggregate milestone payments of up to $1.6 million upon the achievement of specified preclinical, clinical and regulatory milestones. In addition, the Company is required to pay to WIBR a percentage of the non-royalty payments that it receives from sublicensees of the patent rights licensed by WIBR. This percentage varies from low single-digit to low double-digit percentages and will be based upon the clinical stage of the product that is the subject of the sublicense. Royalties shall be paid by the Company on a licensed product-by-licensed product and country-by-country basis, beginning on the first commercial sale of such licensed product in such country until expiration of the last valid patent claim covering such licensed product in such country. The Company has the right to terminate the WIBR License in its entirety, on a patent-by-patent or country-by-country basis, at will upon three months’ notice to WIBR. WIBR may terminate the agreement upon breach of contract or in the event of the Company’s bankruptcy, liquidation, insolvency or cessation of business related to the license. 401(k) Plan In January 2018, the Company established a defined-contribution plan under Section 401(k) of the Internal Revenue Code (the “401(k) Plan”). The 401(k) Plan covers all employees who meet defined minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre-tax basis. The Company will make matching contributions at a rate of 50% of each employee’s contribution up to a maximum employee contribution of 6% of eligible plan compensation. For the three and nine months ended September 30, 2020, the Company made matching contributions of $0.2 million and $0.6 million, respectively. Indemnification Agreements In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, contract research organizations, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and executive officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. The Company has not incurred any material costs as a result of such indemnifications and is not currently aware of any indemnification claims. Legal Proceedings The Company is not currently party to any material legal proceedings. At each reporting date, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses as incurred the costs related to such legal proceedings.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2020
Net Loss Per Share
Net Loss Per Share	10. Net Loss per Share Basic and diluted net loss per share was calculated as follows (in thousands, except share and per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2020 2019 2020 2019 Numerator: ​ ​ ​ ​ Net loss ​ $ (40,852) ​ $ (47,015) ​ $ (127,192) ​ $ (118,986) ​ ​ ​ ​ ​ ​ Denominator: ​ ​ ​ ​ Weighted average common shares outstanding, basic and diluted ​ 80,778,042 ​ 79,115,305 ​ 80,511,543 ​ 78,357,791 Net loss per share, basic and diluted ​ $ (0.51) ​ $ (0.59) ​ $ (1.58) ​ $ (1.52) ​ The Company’s potential dilutive securities have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted average number of common shares outstanding used to calculate both basic and diluted net loss per share is the same. The Company excluded the following potential common shares from the periods in the table above, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect: ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ 2020 2019 Unvested restricted common stock 252,000 397,252 Stock options to purchase common stock 16,541,112 15,849,584 ​ 16,793,112 16,246,836 ​

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2020
Summary of Significant Accounting Policies
Unaudited Interim Financial Information	Unaudited Interim Financial Information The condensed consolidated balance sheet at December 31, 2019 was derived from audited financial statements but does not include all disclosures required by GAAP. The accompanying unaudited condensed consolidated financial statements as of September 30, 2020 and for the three and nine months ended September 30, 2020 and 2019 have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) for interim financial statements. Certain information and footnote disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. These condensed consolidated financial statements should be read in conjunction with the Company’s audited condensed consolidated financial statements and the notes thereto for the year ended December 31, 2019 included in the Company’s Annual Report on Form 10-K for the year-ended December 31, 2019, on file with the SEC. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair statement of the Company’s condensed consolidated financial position as of September 30, 2020 and condensed consolidated results of operations for the three and nine months ended September 30, 2020 and 2019 and the condensed consolidated cash flows for the nine months ended September 30, 2020 and 2019 have been made. The Company’s condensed consolidated results of operations for the three and nine months ended September 30, 2020 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2020.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, the accrual of research and development expenses, the valuation of common stock prior to the IPO and the valuation of stock-based awards. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates as there are changes in circumstances, facts and experience. ​ The full extent to which the COVID-19 pandemic will directly or indirectly impact our business, results of operations and financial condition, including clinical trials, research and development costs and employee-related amounts, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain it or treat COVID-19. ​
Concentrations of Credit Risk and of Significant Suppliers	Concentrations of Credit Risk and of Significant Suppliers Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and investments. The Company’s cash, cash equivalents and investments, as of September 30, 2020, consisted of U.S. government money market funds, U.S. government treasury bills and U.S. government treasury notes. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. The Company relies, and expects to continue to rely, on a small number of vendors to manufacture supplies and raw materials for its development programs. These programs could be adversely affected by a significant interruption in these manufacturing services or the availability of raw materials.
Cash Equivalents	Cash Equivalents The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents.
Restricted Cash	Restricted Cash As of both September 30, 2020 and December 31, 2019, the Company maintained letters of credit totaling $1.7 million for the benefit of the landlords of its leased properties. The Company was required to maintain separate cash balances of these amounts to secure the letters of credit. Related to these separate cash balances, the Company included $0.1 million in prepaid Cash, cash equivalents and restricted cash presented in the accompanying condensed consolidated statement of cash flows was $76.9 million and $111.3 million for the nine months ended September 30, 2020 and 2019, respectively, of which $1.7 million and $1.7 million was restricted cash, respectively.
Fair Value Measurements	Fair Value Measurements Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: ● Level 1—Quoted prices in active markets for identical assets or liabilities. ● Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. ● Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. The Company’s cash equivalents and investments are carried at fair value, determined according to the fair value hierarchy described above (see Note 3). The carrying values of the Company’s accounts payable and accrued expenses approximate their fair values due to the short-term nature of these liabilities. The carrying value of the Company’s long-term debt approximates its fair value due to its variable interest rate, which approximates a market interest rate.
Investments	Investments The Company’s investments are classified as available-for-sale and are carried at fair value. Realized gains and losses and declines in value are based on the specific identification method and are included as a component of other income (expense), net in the condensed consolidated statements of operations and comprehensive loss. The Company classifies its investments with maturities beyond one year as short-term, based on their highly liquid nature and because such investments are available for current operations. In June 2016, issued 2016-13, Financial Instruments - Credit Losses (Topic 326), Measurement of Credit Losses , which changes the impairment model for most financial assets, including the Company’s investments. The Company adopted the standard effective January 1, 2020 using a prospective transition method. The Company evaluates its investments with unrealized losses for impairment. When assessing investments for unrealized declines in value, the Company considers whether the decline in value is related to a credit loss or non-credit loss. For credit losses, the Company reduces the investment to fair value through an allowance for credit losses recorded to the balance sheet and corresponding charge to the statement of operations. The allowance for credit losses and corresponding impairment charge is adjusted each period for changes in fair value. For non-credit losses, the Company reduces the investment to fair value through a charge to the statement of comprehensive loss, reported as a component of accumulated other comprehensive income (loss) in stockholders’ equity. No such adjustments were necessary during the periods presented.
Leases	Leases At the inception of an arrangement as lessee or lessor, the Company determines whether the arrangement is or contains a lease. Operating lease cost is recognized over the lease term on a straight-line basis. Variable lease cost and short-term leases (lease terms less than 12 months) are recognized as incurred. For both lessee and lessor arrangements, variable lease payments are the amounts owed by the Company to a lessor that are not fixed, such as reimbursement for common area maintenance and utilities costs, and are expensed when incurred. When determining the lease term, the Company includes options to extend or terminate the lease when it is reasonably certain that it will exercise that option. For lessee arrangements, operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected lease term. The interest rate implicit in lease contracts is typically not readily determinable. As such, the Company utilizes its incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. Certain adjustments to the right-of-use asset may be required for items such as initial direct costs paid or incentives received. Operating leases are recognized on the balance sheet as right-of-use assets, operating lease liabilities current and operating lease liabilities non-current. The Company has elected the following lease policies at the inception of a lease: (1) for lessee and lessor arrangements within all asset classes, combine lease and non-lease components as a single component, with the lease expense recognized over the expected term on a straight-line basis and (2) for lessee arrangements, apply short-term lease exemption for all leases that qualify, where a right-of-use asset or lease liability will not be recognized for leases with terms of one year or less.
Recently Adopted Accounting Pronouncements and Recently Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements ASU No. 2016-02, Leases In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) ASU 2016-02 initially required adoption using a modified retrospective approach, under which all years presented in the financial statements would be prepared under the revised guidance. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842) The Company adopted ASC 842 using the modified retrospective approach with an effective date of January 1, 2019 for leases that existed on that date. Prior period results continue to be presented under ASC 840 based on the accounting standards originally in effect for such periods. This standard provides a number of optional practical expedients in transition. The Company applied the package of practical expedients to leases that commenced prior to the effective date, whereby it elected not to reassess the following: (i) whether any expired or existing contracts contain leases; (ii) the lease classification for any expired or existing leases; and (iii) initial direct costs for any existing leases. The Company elected the short-term lease recognition exemption for all leases that qualify, where a right-of-use asset or lease liability will not be recognized for short term leases that have terms of one year or less. The most significant effects of adoption were the recognition of material new right-of-use assets and corresponding liabilities on its condensed consolidated balance sheet related to its existing facility operating leases. In addition, the Company has a material lease where the Company was deemed the owner during the construction period and for which the construction was not complete as of January 1, 2019. The Company took control of the leased space during the first quarter of 2019 at which time the lease commenced. Under ASC 842, as the commencement date of this material lease had not occurred, the new right-of-use assets and corresponding liabilities related to this lease were not recognized on the condensed consolidated balance sheet as of date of adoption, January 1, 2019, however, were recognized upon the commencement date of January 28, 2019. The adoption of this standard has had a material impact on the Company’s financial position but did not significantly affect the Company’s results of operations. ASU No. 2018-15, Intangibles–Goodwill and Other–Internal-Use Software In August 2018, the FASB issued ASU No. 2018-15, Intangibles–Goodwill and Other–Internal-Use Software (Topic 350): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract. ASU No. 2016-13, Financial Instruments—Credit Losses In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments. The standard amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses for most financial assets and certain other instruments that aren’t measured at fair value through net income. For available-for-sale debt securities, entities are required to recognize an allowance for credit losses rather than a reduction in carrying value of the asset. Entities are no longer permitted to consider the length of time that fair value has been less than amortized cost when evaluating when credit losses should be recognized. ASU No. 2018-13, Fair Value Measurement In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement 2020 on a prospective basis. The adoption did not have an impact on the Company’s condensed consolidated financial statements. ASU No. 2020-04, Reference Rate Reform In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting ​ Recently Issued Accounting Pronouncements ASU No. 2019-12, Simplifying the Accounting for Income Taxes In December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for Income Taxes (ASC 740).

Investments and Fair Value of_2

Investments and Fair Value of Financial Assets and Liabilities (Tables)	9 Months Ended
	Sep. 30, 2020
Investments and Fair Value of Financial Assets and Liabilities
Schedule of investments by security type	Investments by security type consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ ​ Amortized Cost ​ Gross ​ Gross ​ Credit Losses ​ Fair Value U.S. treasury bills and notes (due within one year) $ 132,698 $ 43 $ (11) ​ $ — ​ $ 132,730 ​ ​ $ 132,698 ​ $ 43 ​ $ (11) ​ $ — ​ $ 132,730 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 ​ ​ Amortized Cost ​ Gross ​ Gross ​ Fair Value U.S. treasury bills and notes (due within one year) $ 189,816 $ 91 $ (20) ​ $ 189,887 U.S. government agency bonds (due within one year) ​ 1,498 ​ 4 ​ — ​ 1,502 ​ ​ $ 191,314 ​ $ 95 ​ $ (20) ​ $ 191,389
Schedule of financial assets and liabilities measured at fair value on a recurring basis	The following tables present the Company’s fair value hierarchy for its assets and liabilities, which are measured at fair value on a recurring basis (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurements at September 30, 2020 using: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Level 1 Level 2 Level 3 Total Assets: ​ ​ ​ ​ ​ Cash equivalents: ​ ​ ​ ​ ​ Money market funds $ 68,916 $ — $ — ​ $ 68,916 Investments: ​ ​ ​ ​ ​ ​ ​ U.S. treasury bills and notes ​ — ​ 132,730 ​ — ​ 132,730 ​ ​ $ 68,916 ​ $ 132,730 ​ $ — ​ $ 201,646 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurements at December 31, 2019 using: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Level 1 Level 2 Level 3 Total Assets: ​ ​ ​ ​ ​ Cash equivalents: ​ ​ ​ ​ ​ Money market funds $ 91,898 $ — $ — ​ $ 91,898 Investments: ​ ​ ​ ​ U.S. government agency bonds ​ — ​ 1,502 ​ — ​ 1,502 U.S. treasury bills and notes ​ — ​ 189,887 ​ — ​ 189,887 ​ ​ $ 91,898 ​ $ 191,389 ​ $ — ​ $ 283,287

Property, Plant and Equipment_2

Property, Plant and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2020
Property, Plant and Equipment, Net.
Schedule of property, plant and equipment, Net	Property, plant and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 December 31, 2019 Manufacturing facility ​ $ 30,539 ​ $ — Manufacturing equipment ​ ​ 8,685 ​ ​ — Land ​ ​ 1,300 ​ ​ 1,300 Laboratory equipment ​ 16,210 ​ ​ 16,079 Computer equipment 2,028 ​ 1,051 Furniture and fixtures ​ ​ 1,228 ​ ​ 1,228 Leasehold improvements 445 ​ 445 Construction-in-progress 2,866 ​ 41,262 ​ 63,301 ​ 61,365 Less: Accumulated depreciation and amortization (8,666) ​ (4,441) ​ ​ $ 54,635 ​ $ 56,924

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	9 Months Ended
	Sep. 30, 2020
Accrued Expenses and Other Current Liabilities
Schedule of accrued expenses and other current liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 December 31, 2019 Accrued employee compensation and benefits $ 5,511 ​ $ 5,045 Accrued external research and development expenses 3,686 ​ 6,715 Accrued manufacturing facility expenses 369 ​ 2,824 Accrued general and administrative expenses ​ ​ 1,462 ​ ​ 1,136 Other 115 ​ 322 ​ ​ $ 11,143 ​ $ 16,042

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2020
Debt
Schedule of estimated future principal payments due	​ ​ ​ ​ As of September 30, 2020, the estimated future principal payments due were as follows (in thousands): ​ ​ ​ ​ Year ending December 31, ​ 2020 (three months ending December 31) ​ $ — 2021 ​ — 2022 ​ ​ 37,500 2023 ​ ​ 37,500 2024 and thereafter ​ ​ — ​ ​ $ 75,000

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2020
Stock-Based Compensation
Schedule of allocation of share based compensation	The Company recorded stock-based compensation expense in the following expense categories of its condensed consolidated statements of operations and comprehensive loss (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2020 2019 2020 2019 Research and development expenses ​ $ 1,996 ​ $ 2,195 $ 6,165 ​ $ 6,798 General and administrative expenses ​ 5,989 ​ 8,163 ​ 18,560 ​ 23,642 ​ ​ $ 7,985 ​ $ 10,358 ​ $ 24,725 ​ $ 30,440

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2020
Net Loss Per Share
Schedule of calculation of basic and diluted net loss per share attributable to common stockholders	Basic and diluted net loss per share was calculated as follows (in thousands, except share and per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2020 2019 2020 2019 Numerator: ​ ​ ​ ​ Net loss ​ $ (40,852) ​ $ (47,015) ​ $ (127,192) ​ $ (118,986) ​ ​ ​ ​ ​ ​ Denominator: ​ ​ ​ ​ Weighted average common shares outstanding, basic and diluted ​ 80,778,042 ​ 79,115,305 ​ 80,511,543 ​ 78,357,791 Net loss per share, basic and diluted ​ $ (0.51) ​ $ (0.59) ​ $ (1.58) ​ $ (1.52)
Schedule of dilutive securities excluded from computations of diluted weighted average shares outstanding	​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ 2020 2019 Unvested restricted common stock 252,000 397,252 Stock options to purchase common stock 16,541,112 15,849,584 ​ 16,793,112 16,246,836

Nature of the Business and Ba_2

Nature of the Business and Basis of Presentation (Details) - USD ($) $ in Thousands	Jul. 20, 2018	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Sale of Equity
Net loss		$ (40,852)	$ (37,854)	$ (48,486)	$ (47,015)	$ (39,390)	$ (32,581)	$ (127,192)	$ (118,986)	$ (163,500)
Accumulated deficit		(439,932)						$ (439,932)		$ (312,740)
Common stock
Sale of Equity
Conversion of redeemable convertible preferred stock to common stock (in shares)	51,845,438
Net loss
IPO
Sale of Equity
Net proceeds after deducting underwriting discounts and commissions and other offering costs	$ 254,300
IPO | Common stock
Sale of Equity
Shares issued (in shares)	12,055,450
Overallotment
Sale of Equity
Shares issued (in shares)	1,572,450

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Summary of Significant Accounting Policies
Restricted cash for the benefit of its leased properties	$ 1,700	$ 1,700
Restricted cash (current)	$ 100	0
Current restricted cash included in prepaid expense and other current assets	ruby:PrepaidExpenseAndOtherCurrent
Restricted cash (non-current)	$ 1,573	1,735
Cash, cash equivalents and restricted cash	76,909	$ 93,633	$ 111,346	$ 309,421
Restricted cash	$ 1,700		$ 1,700

Investments and Fair Value of_3

Investments and Fair Value of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Marketable securities
Amortized Cost	$ 132,698	$ 191,314
Gross Unrealized Gains	43	95
Gross Unrealized Losses	(11)	(20)
Fair Value	132,730	191,389
Assets:
Investments	132,730	191,389
Transfers between Level 1, Level 2 or Level 3
Transfers between Level 1, Level 2 and Level 3	0
U.S. treasury bills and notes
Marketable securities
Amortized Cost	132,698	189,816
Gross Unrealized Gains	43	91
Gross Unrealized Losses	(11)	(20)
Fair Value	132,730	189,887
Assets:
Investments	132,730	189,887
U.S. government agency bonds
Marketable securities
Amortized Cost		1,498
Gross Unrealized Gains		4
Gross Unrealized Losses
Fair Value		1,502
Assets:
Investments		1,502
Recurring
Assets:
Assets	201,646	283,287
Recurring | Money market funds
Assets:
Cash equivalents	68,916	91,898
Recurring | U.S. treasury bills and notes
Marketable securities
Fair Value	132,730	189,887
Assets:
Investments	132,730	189,887
Recurring | U.S. government agency bonds
Marketable securities
Fair Value		1,502
Assets:
Investments		1,502
Recurring | Level 1
Assets:
Assets	68,916	91,898
Recurring | Level 1 | Money market funds
Assets:
Cash equivalents	68,916	91,898
Recurring | Level 2
Assets:
Assets	132,730	191,389
Recurring | Level 2 | U.S. treasury bills and notes
Marketable securities
Fair Value	132,730	189,887
Assets:
Investments	$ 132,730	189,887
Recurring | Level 2 | U.S. government agency bonds
Marketable securities
Fair Value		1,502
Assets:
Investments		$ 1,502

Property, Plant and Equipment_3

Property, Plant and Equipment, Net (Details) $ in Thousands	Jul. 31, 2018USD ($)ft²	Jan. 31, 2020USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2019USD ($)
Property, Plant and Equipment, Net
Property, Plant and Equipment, Gross			$ 63,301	$ 61,365
Less: Accumulated depreciation and amortization			(8,666)	(4,441)
Property, plant and equipment, net			54,635	56,924
Manufacturing facility
Property, Plant and Equipment, Net
Property, Plant and Equipment, Gross			30,539
Square footing of facility acquired | ft²	135,000
Purchases and additions	$ 8,000
Property, Plant and Equipment, Transfers and Changes			30,500
Manufacturing equipment
Property, Plant and Equipment, Net
Property, Plant and Equipment, Gross			8,685
Property, Plant and Equipment, Transfers and Changes		$ (7,800)	7,800
Land
Property, Plant and Equipment, Net
Property, Plant and Equipment, Gross			1,300	1,300
Purchases and additions	1,300
Laboratory equipment
Property, Plant and Equipment, Net
Property, Plant and Equipment, Gross			16,210	16,079
Computer equipment
Property, Plant and Equipment, Net
Property, Plant and Equipment, Gross			2,028	1,051
Furniture and fixtures
Property, Plant and Equipment, Net
Property, Plant and Equipment, Gross			1,228	1,228
Leasehold improvements
Property, Plant and Equipment, Net
Property, Plant and Equipment, Gross			445	445
Construction-in-progress
Property, Plant and Equipment, Net
Property, Plant and Equipment, Gross			$ 2,866	$ 41,262
Purchases and additions	$ 6,700
Property, Plant and Equipment, Transfers and Changes		$ (30,500)

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accrued Expenses and Other Current Liabilities
Accrued employee compensation and benefits	$ 5,511	$ 5,045
Accrued external research and development expenses	3,686	6,715
Accrued manufacturing facility expenses	369	2,824
Accrued general and administrative expenses	1,462	1,136
Other	115	322
Accrued expenses and other current liabilities	$ 11,143	$ 16,042

Debt (Details)

Debt (Details) $ in Thousands	Dec. 21, 2018USD ($)tranche	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Sep. 30, 2020USD ($)
Estimated future principal payments due
2022				$ 37,500
2023				37,500
Total debt				$ 75,000
2018 Credit Facility
Debt
Maximum amount outstanding	$ 75,000
Number of tranche | tranche	3
Borrowing	$ 25,000	$ 25,000	$ 25,000
Period for commencing monthly principal payments	36 months
Amortization period	24 months
Prepayment fee in first year	1.00%
Prepayment fee in second year	0.50%
Prepayment fee in third year	0.25%
Issuance costs	$ 800
Debt default interest rate addition (as a percent)	4
2018 Credit Facility | One-month U.S. LIBOR
Debt
Variable interest rate	5.50%
2018 Credit Facility | Term loan
Debt
Borrowing	$ 25,000

Equity (Details)

Equity (Details) - USD ($) $ / shares in Units, $ in Millions	Jul. 20, 2018	Sep. 30, 2020	Dec. 31, 2019	Aug. 01, 2019
Equity
Common stock, authorized (in shares)	150,000,000	150,000,000	150,000,000
Shares authorized	160,000,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001	$ 0.001
Preferred stock, share authorized (in shares)	10,000,000	10,000,000	10,000,000
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001	$ 0.001
Common stock
Equity
Conversion of redeemable convertible preferred stock to common stock (in shares)	51,845,438
IPO
Equity
Net proceeds after deducting underwriting discounts and commissions and other offering costs	$ 254.3
IPO | Common stock
Equity
Shares issued (in shares)	12,055,450
Overallotment
Equity
Shares issued (in shares)	1,572,450
At the market offering
Equity
Shares issued (in shares)		0
Percentage of commission				3.00%
Aggregate offering price				$ 100

Stock-Based Compensation - Perf

Stock-Based Compensation - Performance based stock options (Details) - Service Based Stock Options - Vesting based on service period	9 Months Ended
	Sep. 30, 2020$ / sharesshares
Stock-Based Compensation
Options granted | shares	3,738,221
Options exercise price	$ 7.44
Weighted average grant-date fair value (per share)	$ 4.62

Stock-Based Compensation - Comp

Stock-Based Compensation - Compensation expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Stock-based compensation expense
Stock-based compensation expense	$ 7,985	$ 10,358	$ 24,725	$ 30,440
Unrecognized compensation cost	52,500		$ 52,500
Unrecognized compensation cost expected to be recognized over a weighted average period			1 year 10 months 24 days
Research and development expenses
Stock-based compensation expense
Stock-based compensation expense	1,996	2,195	$ 6,165	6,798
General and administrative expenses
Stock-based compensation expense
Stock-based compensation expense	$ 5,989	$ 8,163	$ 18,560	$ 23,642

Commitments and Contingencies -

Commitments and Contingencies - Collaborative Arrangements and Non-collaborative Arrangement (Details) - WIBR $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)
Collaborative Arrangements and Non-collaborative Arrangement
Aggregate milestone payments	$ 1.6
Maximum | License maintenance fees
Collaborative Arrangements and Non-collaborative Arrangement
License costs	$ 0.1

Commitments and Contingencies_2

Commitments and Contingencies - Defined Contribution Plan (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	9 Months Ended
	Jan. 31, 2018	Sep. 30, 2020	Sep. 30, 2020
Commitments and Contingencies
Employer matching contribution (as a percent)	50.00%
Company matching contribution		$ 0.2	$ 0.6
Maximum
Commitments and Contingencies
Maximum employee contribution	6.00%

Net Loss Per Share - Weighted A

Net Loss Per Share - Weighted Average Shares (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended		12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Numerator:
Net Loss	$ (40,852)	$ (37,854)	$ (48,486)	$ (47,015)	$ (39,390)	$ (32,581)	$ (127,192)	$ (118,986)	$ (163,500)
Denominator:
Weighted average common shares outstanding, basic and diluted	80,778,042			79,115,305			80,511,543	78,357,791
Net loss per share, basic and diluted	$ (0.51)			$ (0.59)			$ (1.58)	$ (1.52)

Net Loss Per Share - Antidiluti

Net Loss Per Share - Antidilutive Securities (Details) - shares	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Diluted net loss per share attributable to common stockholders
Antidilutive securities excluded from computation of of diluted weighted average shares outstanding	16,793,112	16,246,836
Unvested restricted common stock
Diluted net loss per share attributable to common stockholders
Antidilutive securities excluded from computation of of diluted weighted average shares outstanding	252,000	397,252
Stock options to purchase common stock
Diluted net loss per share attributable to common stockholders
Antidilutive securities excluded from computation of of diluted weighted average shares outstanding	16,541,112	15,849,584