Allena Pharmaceuticals (ALNAQ) 10-Q 7 Aug 19 2019 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Jul. 26, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Trading Symbol	ALNA
Entity Registrant Name	ALLENA PHARMACEUTICALS, INC.
Entity Central Index Key	0001624658
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		23,465,665
Entity File Number	001-38268
Entity Tax Identification Number	452729920
Entity Address, Address Line One	One Newton Executive Park
Entity Address, Address Line Two	Suite 202
Entity Address, City or Town	Newton
Entity Address, State or Province	Massachusetts
Entity Address, Postal Zip Code	02462
City Area Code	617
Local Phone Number	467-4577

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 48,523	$ 61,643
Prepaid expenses and other current assets	3,726	2,826
Total current assets	52,249	64,469
Property and equipment, net	465	514
Operating lease assets	745
Other assets	123	246
Total assets	53,582	65,229
Current liabilities:
Accounts payable	2,283	2,138
Loan payable, net of discount	1,992
Operating lease liabilities	522
Accrued expenses and other current liabilities	2,887	3,625
Total current liabilities	7,684	5,763
Loan payable, net of current portion and discount	7,984	9,980
Operating lease liabilities, net of current portion	233
Other liabilities	8	30
Total liabilities	15,909	15,773
Commitments and contingencies (Note 6)
Stockholders’ equity:
Undesignated preferred stock, $0.001 par value; 5,000,000 shares authorized; no shares authorized, issued or outstanding
Common stock, $0.001 par value; 125,000,000 shares authorized; 23,462,165 and 20,809,025 shares issued and outstanding at June 30, 2019 and December 31, 2018, respectively	23	21
Additional paid-in capital	177,947	167,040
Accumulated deficit	(140,297)	(117,605)
Total stockholders’ equity	37,673	49,456
Total liabilities and stockholders’ equity	$ 53,582	$ 65,229

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) (unaudited) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Undesignated preferred stock, par value	$ 0.001	$ 0.001
Undesignated preferred stock, shares authorized	5,000,000	5,000,000
Undesignated preferred stock, shares issued	0	0
Undesignated preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares issued	23,462,165	20,809,025
Common stock, shares outstanding	23,462,165	20,809,025

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating expenses:
Research and development	$ 8,589	$ 5,860	$ 17,717	$ 11,791
General and administrative	2,746	2,275	5,177	4,317
Total operating expenses	11,335	8,135	22,894	16,108
Loss from operations	(11,335)	(8,135)	(22,894)	(16,108)
Other income (expense):
Interest income, net	78	118	229	218
Other expense, net	(16)	(13)	(27)	(20)
Loss on extinguishment of debt		(617)		(617)
Other income (expense), net	62	(512)	202	(419)
Net loss	$ (11,273)	$ (8,647)	$ (22,692)	$ (16,527)
Net loss per share attributable to common stockholders—basic and diluted	$ (0.54)	$ (0.42)	$ (1.09)	$ (0.80)
Weighted-average common shares outstanding—basic and diluted	20,903,298	20,733,043	20,859,251	20,714,319
Net loss	$ (11,273)	$ (8,647)	$ (22,692)	$ (16,527)
Comprehensive loss	$ (11,273)	$ (8,647)	$ (22,692)	$ (16,527)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders' Equity (unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Balance at Dec. 31, 2017	$ 82,870	$ 20	$ 164,807	$ (81,957)
Balance, Shares at Dec. 31, 2017		20,694,658
Exercise of common stock options	81	$ 1	80
Exercise of common stock options, shares		57,509
Stock-based compensation	917		917
Issuance costs related to initial public offering	13		13
Net loss	(16,527)			(16,527)
Balance at Jun. 30, 2018	67,354	$ 21	165,817	(98,484)
Balance, Shares at Jun. 30, 2018		20,752,167
Balance at Mar. 31, 2018	75,408	$ 20	165,225	(89,837)
Balance, Shares at Mar. 31, 2018		20,695,556
Exercise of common stock options	81	$ 1	80
Exercise of common stock options, shares		56,611
Stock-based compensation	512		512
Net loss	(8,647)			(8,647)
Balance at Jun. 30, 2018	67,354	$ 21	165,817	(98,484)
Balance, Shares at Jun. 30, 2018		20,752,167
Balance at Dec. 31, 2018	$ 49,456	$ 21	167,040	(117,605)
Balance, Shares at Dec. 31, 2018	20,809,025	20,809,025
Issuance of common stock, net of issuance costs	$ 9,446	$ 2	9,444
Issuance of common stock, net of issuance costs, shares		2,632,092
Exercise of common stock options	13		13
Exercise of common stock options, shares		7,039
Issuance of common stock through employee stock purchase plan ("ESPP")	49		49
Issuance of common stock through employee stock purchase plan ("ESPP"), shares		14,009
Stock-based compensation	1,401		1,401
Net loss	(22,692)			(22,692)
Balance at Jun. 30, 2019	$ 37,673	$ 23	177,947	(140,297)
Balance, Shares at Jun. 30, 2019	23,462,165	23,462,165
Balance at Mar. 31, 2019	$ 38,679	$ 21	167,682	(129,024)
Balance, Shares at Mar. 31, 2019		20,816,064
Issuance of common stock, net of issuance costs	9,446	$ 2	9,444
Issuance of common stock, net of issuance costs, shares		2,632,092
Issuance of common stock through employee stock purchase plan ("ESPP")	49		49
Issuance of common stock through employee stock purchase plan ("ESPP"), shares		14,009
Stock-based compensation	772		772
Net loss	(11,273)			(11,273)
Balance at Jun. 30, 2019	$ 37,673	$ 23	$ 177,947	$ (140,297)
Balance, Shares at Jun. 30, 2019	23,462,165	23,462,165

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net loss	$ (22,692)	$ (16,527)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	1,401	917
Depreciation expense	79	27
Non-cash interest expense	4	157
Loss on extinguishment of debt		617
Changes in assets and liabilities:
Prepaid expenses and other current assets	(900)	628
Operating lease assets	246
Other assets	123	(7)
Accounts payable	216	(726)
Accrued expenses	(868)	(12)
Operating lease liabilities	(244)
Other liabilities	(1)	7
Net cash used in operating activities	(22,636)	(14,919)
Cash flows from investing activities:
Purchases of property and equipment	(101)	(115)
Net cash used in investing activities	(101)	(115)
Cash flows from financing activities:
Proceeds from (payments of issuance costs) the issuance of common stock, net of issuance costs	9,569	(186)
Proceeds from exercise of stock options	13	81
Proceeds from issuance of stock through ESPP	49
Proceeds from loan payable		10,000
Repayment of loan payable		(10,492)
Debt issuance costs paid		(10)
Other	(14)
Net cash provided by (used in) financing activities	9,617	(607)
Net decrease in cash and cash equivalents	(13,120)	(15,641)
Cash and cash equivalents, beginning of period	61,643	94,494
Cash and cash equivalents, end of period	48,523	$ 78,853
Supplemental disclosures:
Cash paid in connection with operating lease liabilities	265
Right-of-use assets obtained in exchange of operating lease obligations	992
Issuance costs included in accrued expenses	$ 123

Nature of Business

Nature of Business	6 Months Ended
	Jun. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of Business	1. Nature of Business Allena Pharmaceuticals, Inc. (the “Company”) is a late-stage clinical biopharmaceutical company dedicated to developing and commercializing first-in-class, oral enzyme therapeutics to treat patients with rare and severe metabolic and kidney disorders. The Company is focused on metabolic disorders that result in excess accumulation of certain metabolites that can cause kidney stones, damage the kidney, and potentially lead to chronic kidney disease (“CKD”), and end-stage renal disease. The Company’s lead product candidate, reloxaliase (formerly known as ALLN-177), is a first-in-class, oral enzyme therapeutic that it is developing for the treatment of hyperoxaluria, a metabolic disorder commonly associated with kidney stones, CKD and other serious kidney diseases. The Company was incorporated under the laws of the State of Delaware on June 24, 2011 and is located in Newton, Massachusetts. On June 28, 2019, the Company completed a registered direct offering in which the Company issued and sold 2,632,092 shares of its common stock, at a purchase price of $3.80 per share, for gross proceeds of $10.0 million through a securities purchase agreement with the investors. The shares of common stock sold in this offering were being offered pursuant to the Company’s shelf registration statement on Form S-3 filed with the Securities and Exchange Commission, which was declared effective on December 26, 2018. As a result of the registered direct offering, the Company received approximately $9.6 million after deducting offering costs. The Company is subject to risks common to companies in the biotechnology industry, including but not limited to, risks of failure of preclinical studies and clinical trials, the need to obtain marketing approval for any drug product candidate that it may identify and develop, the need to successfully commercialize and gain market acceptance of its product candidates, dependence on key personnel, protection of proprietary technology, compliance with government regulations, development by competitors of technological innovations, reliance on third party manufacturers, ability to transition from pilot-scale manufacturing to large-scale production of products and the need to obtain adequate additional financing to fund the development of its product candidates. The Company had an accumulated deficit of $140.3 million at June 30, 2019, and will require substantial additional capital to fund operations. The future success of the Company is dependent on its ability to identify and develop its product candidates and ultimately upon its ability to attain profitable operations. At June 30, 2019, the Company had $48.5 million of cash and cash equivalents. The Company believes that its cash and cash equivalents as of June 30, 2019 will be sufficient to fund the Company’s operating expenses and capital expenditure requirements into the fourth quarter of 2020.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The Company’s unaudited interim condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (ASU) of the Financial Accounting Standards Board (“FASB”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2018 and notes thereto, included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 filed with the SEC on March 7, 2019. The unaudited interim consolidated financial statements have been prepared on the same basis as the audited financial statements with the exception of the 2019 adoption of the new leasing standard as discussed below. In the opinion of the Company’s management, the accompanying unaudited interim condensed consolidated financial statements contain all adjustments which are necessary to present fairly the Company’s financial position as of June 30, 2019, the results of its operations for the three and six months ended June 30, 2019 and June 30, 2018 and cash flows for the six months ended June 30, 2019 and June 30, 2018. Such adjustments are of a normal and recurring nature. The results for the three months ended June 30, 2019 are not necessarily indicative of the results for the year ending December 31, 2019, or for any future period. Principles of Consolidation The consolidated financial statements include the accounts of Allena Pharmaceuticals, Inc. and its wholly owned subsidiaries Allena Pharmaceuticals Security Corporation (“Security Corporation”), which was incorporated in December 2014, and Allena Pharmaceuticals Ireland Limited, which was incorporated in March 2017. All intercompany transactions and balances have been eliminated. Fair Value of Financial Instruments Fair value is defined as the price that would be received upon sale of an asset or paid to transfer a liability between market participants at measurement dates. ASC Topic 820, Fair Value Measurement Level 1 inputs: Quoted prices in active markets for identical assets or liabilities. Level 2 inputs: Inputs other than quoted prices included within Level 1 that are either directly or indirectly observable, such as quoted market prices, interest rates and yield curves. Level 3 inputs: Unobservable inputs developed using estimates or assumptions developed by the Company, which reflect those that a market participant would use in pricing the asset or liability. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Leases The Company adopted ASU No. 2016-02, Leases (Topic 842) A lease qualifies as a finance lease if any of the following criteria are met at the inception of the lease: (i) there is a transfer of ownership of the leased asset to the Company by the end of the lease term, (ii) the Company holds an option to purchase the leased asset that it is reasonably certain to exercise, (iii) the lease term is for a major part of the remaining economic life of the leased asset, (iv) the present value of the sum of lease payments equals or exceeds substantially all of the fair value of the leased asset, (v) the nature of the leased asset is specialized to the point that it is expected to provide the lessor no alternative use at the end of the lease term. All other leases are recorded as operating leases. Finance and operating lease assets and liabilities are recognized at the lease commencement date based on the present value of the lease payments over the lease term using the discount rate implicit in the lease. If the rate implicit is not readily determinable, the Company’s utilizes its incremental borrowing rate at the lease commencement date. Operating lease assets are further adjusted for prepaid or accrued lease payments. Operating lease payments are expensed using the straight-line method as an operating expense over the lease term. Finance lease assets are amortized to depreciation expense using the straight-line method over the shorter of the useful life of the related asset or the lease term. Finance lease payments are bifurcated into (i) a portion that is recorded as imputed interest expense and (ii) a portion that reduces the finance liability associated with the lease. The Company separates lease and non-lease components when determining which lease payments to include in the calculation of its lease assets and liabilities. Variable lease payments are expensed as incurred. If a lease includes an option to extend or terminate the lease, the Company reflects the option in the lease term if it is reasonably certain it will exercise the option. Operating leases are recorded in “Operating lease assets,” “Operating lease liabilities” and “Operating lease liabilities, net of current portion” on the Company’s condensed consolidated balance sheet. The Company did not have any finance leases recorded on its condensed consolidated balance sheet as of June 30, 2019. The remainder of the Company’s significant accounting policies are described in the Annual Report filed on Form 10-K for the year ended December 31, 2018 that was filed with the United States Securities and Exchange Commission on March 7, 2019. Recently Adopted Accounting Pronouncements In 2016, the FASB issued ASC 842, which amends a number of aspects of lease accounting and requires entities to recognize right-of-use assets and liabilities on the balance sheet. ASC 842 was effective on January 1, 2019. In July 2018, the FASB issued ASU No. 2018-11, Leases (Topic 842): Targeted Improvements The Company elected the package of transition practical expedients for leases that commenced prior to January 1, 2019, allowing it not to reassess (i) whether any expired or existing contracts contain leases, (ii) the lease classification for any expired or existing leases and (iii) the initial indirect costs for any existing leases. The Company recorded, upon adoption of ASC 842 on January 1, 2019, right-of-use assets of $1.0 million and corresponding liabilities of $1.0 million related to its operating leases. The Company did not have any leases at January 1, 2019 that would qualify as finance leases. These adjustments had no impact on the Company’s consolidated statement of operations and had no impact on the Company’s accumulated deficit. Refer to Note 6, “Commitments and Contingencies,” for further information regarding the Company’s leases as well as certain disclosures required by ASC 842. In June 2018, the FASB issued ASU No. 2018-07, Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting Recently Issued Accounting Pronouncements In 2018, the FASB issued ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract In 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement In 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments

Net Loss per Share

Net Loss per Share	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Net Loss per Share	3. Net Loss per Share Basic net loss per share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding for the period, without consideration for potentially dilutive securities. The Company has computed diluted net loss per common share after giving consideration to all potentially dilutive common shares, including options to purchase common stock, restricted common stock, convertible preferred stock and warrants to purchase convertible preferred stock, outstanding during the period determined using the treasury-stock and if-converted methods, except where the effect of including such securities would be antidilutive. Because the Company has reported net losses since inception, these potential common shares have been anti-dilutive and basic and diluted loss per share have been the same. Basic and diluted net loss per share attributable to common stockholders was calculated as follows (in thousands, except share and per share data): Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Numerator: Net loss $ (11,273 ) $ (8,647 ) $ (22,692 ) $ (16,527 ) Net loss attributable to common stockholders $ (11,273 ) $ (8,647 ) $ (22,692 ) $ (16,527 ) Denominator: Weighted-average common shares—basic and diluted 20,903,298 20,733,043 20,859,251 20,714,319 Net loss per share attributable to common stockholders—basic and diluted $ (0.54 ) $ (0.42 ) $ (1.09 ) $ (0.80 ) The following table sets forth the potentially dilutive securities that have been excluded from the calculation of diluted net loss per share because to include them would be anti-dilutive (in common stock equivalent shares): Six Months Ended June 30, 2019 2018 Warrants 9,040 9,040 Stock options 3,142,132 2,097,652 Total 3,151,172 2,106,692

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. Fair Value Measurements The following tables present information about the Company’s financial assets and liabilities that have been measured at fair value at June 30, 2019 and December 31, 2018, and indicates the fair value hierarchy of the valuation inputs utilized to determine such fair value (in thousands): Description June 30, 2019 Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Money market funds, included in cash and cash equivalents $ 48,115 $ 48,115 $ — $ — Total assets $ 48,115 $ 48,115 $ — $ — Description December 31, 2018 Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Money market funds, included in cash and cash equivalents $ 61,415 $ 61,415 $ — $ — Total assets $ 61,415 $ 61,415 $ — $ — At June 30, 2019 and December 31, 2018, all of the Company’s cash equivalents were comprised of money market funds. There were no changes to the valuation methods during the three and six months ended June 30, 2019 and the year ended December 31, 2018. There were no transfers within the fair value hierarchy during the three and six months ended June 30, 2019 and the year ended December 31, 2018. The carrying amounts reflected in the consolidated balance sheets for cash and cash equivalents, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their carrying values. The Company believes the terms of the loan payable reflect current market conditions for an instrument with similar terms and maturity, therefore the carrying value of the Company’s debt approximates its fair value based on Level 3 of the fair value hierarchy.

Accrued Expenses

Accrued Expenses	6 Months Ended
	Jun. 30, 2019
Payables And Accruals [Abstract]
Accrued Expenses	5. Accrued Expenses Accrued expenses consist of the following (in thousands): June 30, 2019 December 31, 2018 Payroll and employee-related expenses $ 1,191 $ 1,690 Third-party research and development expenses 1,260 1,514 Professional fees 345 299 Loan interest 46 46 Other 45 76 Total accrued expenses $ 2,887 $ 3,625

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	6. Commitments and Contingencies The Company is a party to operating leases for approximately 7,795 square feet of office space in Newton, MA (Newton Lease), and for approximately 7,564 square feet of laboratory and office space in Sudbury, MA (Sudbury Lease). The Newton Lease expires on December 31, 2020 and the Sudbury Lease expires on February 28, 2021. Annualized base rent for the Newton Lease and the Sudbury lease is approximately $0.3 million and $0.2 million, respectively. Aggregate Lease Information Related to the Application of ASC 842 Maturities of the Company’s operating lease liabilities in accordance with ASC 842 as of June 30, 2019 are as follows (in thousands): Remainder of 2019 $ 223 2020 539 2021 30 Total maturities 792 Less: Amount representing interest (37 ) Present value of operating lease liabilities $ 755 Lease costs included in the Company’s condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2019 were $0.1 million and $0.3 million, respectively. The Company’s operating leases had a weighted average remaining lease term of 1.5 years and a weighted average discount rate of 5.5% at June 30, 2019. Additional Lease Information Related to the Application of ASC 840 The following information is disclosed in accordance with ASC 840, Leases (Topic 840) December 31, 2018 2019 $ 487 2020 539 2021 30 $ 1,056 During the three and six months ended June 30, 2018, rent expense was $0.1 million and $0.2 million, respectively.

Loan and Security Agreement

Loan and Security Agreement	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Loan and Security Agreement	7. Loan and Security Agreement In August 2014, the Company entered into a Loan Agreement with Silicon Valley Bank (“SVB”) and borrowed $7.0 million under the loan. In May 2016, the Loan Agreement was amended (“Amended Loan Agreement”) to borrow up to $10.0 million with a portion of the proceeds to be used to pay down the outstanding balance of the original $7.0 million of advances. At the time of the Amended Loan Agreement, SVB advanced a gross amount of $7.5 million to the Company. Net proceeds received by the Company were $1.6 million after deducting $5.3 million for repayment of the original advances and $0.6 million for final interest due upon maturity or prepayment of the original advances. In December 2016, upon the achievement of certain milestones, SVB advanced the remaining $2.5 million available under the Amended Loan Agreement. The borrowings were secured by a lien on all Company assets, excluding intellectual property. The May 2016 and December 2016 advances had a floating per annum interest rate equal to the greater of 4.0% or 0.5% above the prime rate. In December 2016, the interest only period was extended to 18 months. Upon the expiration of the interest only period, amounts borrowed were to be repaid over 30 equal monthly payments of principal and interest. At its option, the Company could prepay all, but not less than all, of the outstanding borrowings subject to a prepayment premium as defined in the Amended Loan Agreement. The Company was also required to make a final payment equal to 8.25% of the total borrowings (“Final Payment”) on the earliest of the loan maturity date, an acceleration of the loan as defined in the Amended Loan Agreement or at the time of prepayment. On June 29, 2018, the Company terminated the Amended Loan Agreement and repaid the $7.7 million outstanding principal balance and the Final Payment to SVB. The Company recorded a loss on extinguishment of debt of $0.6 million in the Statement of Operations, accordingly. On June 29, 2018 the Company also entered into a loan agreement with Pacific Western Bank (“PWB Loan Agreement”) providing up to $12.0 million of borrowings, of which $10.0 million was advanced on June 29, 2018. The remaining $2.0 million of borrowings available under the PWB Loan Agreement are available to the Company through one additional advance request until the end of the interest only period as defined below. Borrowings are secured by a lien on all Company assets, excluding intellectual property, and amounts borrowed have a floating per annum interest rate of the greater of 5.0% or the prime rate. The PWB Loan Agreement has a term of 48 months and an initial interest only period of 18 months. If the Company receives at least $50M of gross proceeds from the sale of its equity securities or upfront cash payment from a strategic partnership prior the expiration of the initial interest only period, the interest only period will be extended an additional six months. Upon the expiration of the initial interest only period on December 31, 2019, amounts borrowed will be repaid over 30 equal monthly payments of principal plus accrued but unpaid interest. If the interest only period is extended an additional six months, amounts borrowed will be repaid over 24 equal monthly payments of principal plus accrued but unpaid interest beginning July 1, 2020. At its option, the Company may prepay all, but not less than all, of the outstanding borrowings subject to a prepayment premium as defined in the Loan Agreement. Upon the closing of one or more financings, in which the Company receives aggregate gross proceeds of at least $25 million, a success fee of $300,000 will be due and payable to the Lender. The Company’s obligation to pay this Success Fee survives termination of the Agreement. The PWB Loan Agreement contains negative covenants restricting the Company’s activities, including limitations on dispositions, mergers or acquisitions, incurring indebtedness or liens, paying dividends or making investments and certain other business transactions. There are no financial covenants associated with the PWB Loan Agreement. The obligations under the PWB Loan Agreement are subject to acceleration upon the occurrence of specified events of default, including a material adverse change in the Company’s business, operations or financial or other condition. The Company has determined that the risk of subjective acceleration under the material adverse events clause is remote and therefore has classified the outstanding principal based on scheduled principal payments. The Company evaluated the PWB Loan Agreement for embedded features that require bifurcation, noting certain features were required to be bifurcated, but were concluded to be de minimis in value at June 30, 2019 and December 31, 2018.

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Stockholders' Equity	8. Stockholders’ Equity Common Stock The holders of common stock are entitled to one vote for each share held. Common stockholders are not entitled to receive dividends, unless declared by the Board of Directors. The Company has reserved for future issuances the following shares of common stock as of June 30, 2019 and December 31, 2018: June 30, 2019 December 31, 2018 Warrants 9,040 9,040 Stock options 5,087,663 4,262,341 Employee stock purchase plan 391,733 405,742 Total 5,488,436 4,677,123

Stock Incentive Plan

Stock Incentive Plan	6 Months Ended
	Jun. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Incentive Plan	9. Stock Incentive Plan On October 31, 2017, the Company adopted the 2017 Stock Option and Incentive Plan (“2017 Plan”). Upon the adoption of the 2017 Plan, no further grants would be made under the 2011 Stock Incentive Plan (“2011 Plan”). The 2017 Plan initially provided for the grant of awards for 2,038,021 shares of common stock. In addition to the shares available for grant under the 2017 Plan, any awards outstanding under the 2011 Plan as of the October 31, 2017 are cancelled, forfeited or otherwise terminated without being exercised, the number of shares underlying such awards will be available for future grant under the 2017 Plan. The 2017 Plan also provides that an additional number of shares will automatically be added to the shares authorized for issuance under the 2017 Plan on January 1 of each year. The number of shares added each year will be equal to the lesser of: (i) 4% of the outstanding shares on the immediately preceding December 31 or (ii) such amount as determined by the Compensation Committee of the registrant’s Board of Directors. On January 1, 2018, the shares available for grant under the 2017 Plan was automatically increased by 827,786 shares. On January 1, 2019, the shares available for grant under the 2017 Plan was automatically increased by an additional 832,361 shares. All of the Company’s employees, officers, directors, consultants and advisors are eligible to be granted options, restricted stock units (“RSUs”), and other share-based awards under the terms of the 2017 Plan. As of June 30, 2019, 1,945,531 shares of common stock were available for future grant under the 2017 Plan. All stock option grants are nonstatutory stock options except option grants to employees (including officers and directors) intended to qualify as incentive stock options under the Internal Revenue Code of 1986, as amended. Incentive stock options may not be granted at less than the fair market value of the Company’s common stock on the date of grant, as determined in good faith by the Board of Directors at its sole discretion. Nonqualified stock options may be granted at an exercise price established by the Board of Directors at its sole discretion (which has not been less than fair market value on the date of grant) and the vesting periods may vary. Vesting periods are generally four years and are determined by the Board of Directors or a delegated subcommittee. Stock options become exercisable as they vest. Options granted under both the 2011 Plan and 2017 Plan expire no more than 10 years from the date of grant. Stock-based compensation expense included in the Company’s statements of operations and comprehensive loss is as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Research and development $ 311 $ 144 $ 566 $ 234 General and administrative 461 368 835 683 Total $ 772 $ 512 $ 1,401 $ 917 The fair value of each stock option granted to employees and directors was estimated on the date of grant using the Black-Scholes option-pricing model, with the following range of assumptions as follows: Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Risk-free interest rate 1.9%-2.3% 2.6%-2.8% 1.9%-2.6% 2.3%-2.8% Expected dividend yield —% —% —% —% Expected term (in years) 5.5-6.1 5.5-6.1 5.5-6.8 5.5-6.1 Expected volatility 82%-83% 85%-87% 82%-83% 81%-89% A summary of the stock option activity under the 2011 and 2017 Plans is as follows: Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life (in years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2018 2,141,527 4.32 7.7 $ 4,959 Granted 1,024,250 6.71 Exercised (7,039 ) 1.85 Cancelled (16,606 ) 6.23 Outstanding at June 30, 2019 3,142,132 $ 5.09 8.0 $ 3,237 Exercisable at June 30, 2019 1,453,371 $ 3.04 6.7 $ 2,961 As of June 30, 2019, total unrecognized stock-based compensation expense relating to unvested stock options was $7.7 million. This amount is expected to be recognized over a weighted-average period of 2.9 years.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company’s unaudited interim condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (ASU) of the Financial Accounting Standards Board (“FASB”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2018 and notes thereto, included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 filed with the SEC on March 7, 2019. The unaudited interim consolidated financial statements have been prepared on the same basis as the audited financial statements with the exception of the 2019 adoption of the new leasing standard as discussed below. In the opinion of the Company’s management, the accompanying unaudited interim condensed consolidated financial statements contain all adjustments which are necessary to present fairly the Company’s financial position as of June 30, 2019, the results of its operations for the three and six months ended June 30, 2019 and June 30, 2018 and cash flows for the six months ended June 30, 2019 and June 30, 2018. Such adjustments are of a normal and recurring nature. The results for the three months ended June 30, 2019 are not necessarily indicative of the results for the year ending December 31, 2019, or for any future period.
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of Allena Pharmaceuticals, Inc. and its wholly owned subsidiaries Allena Pharmaceuticals Security Corporation (“Security Corporation”), which was incorporated in December 2014, and Allena Pharmaceuticals Ireland Limited, which was incorporated in March 2017. All intercompany transactions and balances have been eliminated.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Fair value is defined as the price that would be received upon sale of an asset or paid to transfer a liability between market participants at measurement dates. ASC Topic 820, Fair Value Measurement Level 1 inputs: Quoted prices in active markets for identical assets or liabilities. Level 2 inputs: Inputs other than quoted prices included within Level 1 that are either directly or indirectly observable, such as quoted market prices, interest rates and yield curves. Level 3 inputs: Unobservable inputs developed using estimates or assumptions developed by the Company, which reflect those that a market participant would use in pricing the asset or liability. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.
Leases	Leases The Company adopted ASU No. 2016-02, Leases (Topic 842) A lease qualifies as a finance lease if any of the following criteria are met at the inception of the lease: (i) there is a transfer of ownership of the leased asset to the Company by the end of the lease term, (ii) the Company holds an option to purchase the leased asset that it is reasonably certain to exercise, (iii) the lease term is for a major part of the remaining economic life of the leased asset, (iv) the present value of the sum of lease payments equals or exceeds substantially all of the fair value of the leased asset, (v) the nature of the leased asset is specialized to the point that it is expected to provide the lessor no alternative use at the end of the lease term. All other leases are recorded as operating leases. Finance and operating lease assets and liabilities are recognized at the lease commencement date based on the present value of the lease payments over the lease term using the discount rate implicit in the lease. If the rate implicit is not readily determinable, the Company’s utilizes its incremental borrowing rate at the lease commencement date. Operating lease assets are further adjusted for prepaid or accrued lease payments. Operating lease payments are expensed using the straight-line method as an operating expense over the lease term. Finance lease assets are amortized to depreciation expense using the straight-line method over the shorter of the useful life of the related asset or the lease term. Finance lease payments are bifurcated into (i) a portion that is recorded as imputed interest expense and (ii) a portion that reduces the finance liability associated with the lease. The Company separates lease and non-lease components when determining which lease payments to include in the calculation of its lease assets and liabilities. Variable lease payments are expensed as incurred. If a lease includes an option to extend or terminate the lease, the Company reflects the option in the lease term if it is reasonably certain it will exercise the option. Operating leases are recorded in “Operating lease assets,” “Operating lease liabilities” and “Operating lease liabilities, net of current portion” on the Company’s condensed consolidated balance sheet. The Company did not have any finance leases recorded on its condensed consolidated balance sheet as of June 30, 2019. The remainder of the Company’s significant accounting policies are described in the Annual Report filed on Form 10-K for the year ended December 31, 2018 that was filed with the United States Securities and Exchange Commission on March 7, 2019.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In 2016, the FASB issued ASC 842, which amends a number of aspects of lease accounting and requires entities to recognize right-of-use assets and liabilities on the balance sheet. ASC 842 was effective on January 1, 2019. In July 2018, the FASB issued ASU No. 2018-11, Leases (Topic 842): Targeted Improvements The Company elected the package of transition practical expedients for leases that commenced prior to January 1, 2019, allowing it not to reassess (i) whether any expired or existing contracts contain leases, (ii) the lease classification for any expired or existing leases and (iii) the initial indirect costs for any existing leases. The Company recorded, upon adoption of ASC 842 on January 1, 2019, right-of-use assets of $1.0 million and corresponding liabilities of $1.0 million related to its operating leases. The Company did not have any leases at January 1, 2019 that would qualify as finance leases. These adjustments had no impact on the Company’s consolidated statement of operations and had no impact on the Company’s accumulated deficit. Refer to Note 6, “Commitments and Contingencies,” for further information regarding the Company’s leases as well as certain disclosures required by ASC 842. In June 2018, the FASB issued ASU No. 2018-07, Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In 2018, the FASB issued ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract In 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement In 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments

Net Loss per Share (Tables)

Net Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Summary of Basic and Diluted Net Loss per Share Attributable to Common Stockholders	Basic and diluted net loss per share attributable to common stockholders was calculated as follows (in thousands, except share and per share data): Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Numerator: Net loss $ (11,273 ) $ (8,647 ) $ (22,692 ) $ (16,527 ) Net loss attributable to common stockholders $ (11,273 ) $ (8,647 ) $ (22,692 ) $ (16,527 ) Denominator: Weighted-average common shares—basic and diluted 20,903,298 20,733,043 20,859,251 20,714,319 Net loss per share attributable to common stockholders—basic and diluted $ (0.54 ) $ (0.42 ) $ (1.09 ) $ (0.80 )
Summary of Anti-dilutive Securities Excluded from Calculation of Diluted Net Loss per Share	The following table sets forth the potentially dilutive securities that have been excluded from the calculation of diluted net loss per share because to include them would be anti-dilutive (in common stock equivalent shares): Six Months Ended June 30, 2019 2018 Warrants 9,040 9,040 Stock options 3,142,132 2,097,652 Total 3,151,172 2,106,692

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Summary of Financial Assets and Liabilities Measured at Fair Value	The following tables present information about the Company’s financial assets and liabilities that have been measured at fair value at June 30, 2019 and December 31, 2018, and indicates the fair value hierarchy of the valuation inputs utilized to determine such fair value (in thousands): Description June 30, 2019 Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Money market funds, included in cash and cash equivalents $ 48,115 $ 48,115 $ — $ — Total assets $ 48,115 $ 48,115 $ — $ — Description December 31, 2018 Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Money market funds, included in cash and cash equivalents $ 61,415 $ 61,415 $ — $ — Total assets $ 61,415 $ 61,415 $ — $ —

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Jun. 30, 2019
Payables And Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consist of the following (in thousands): June 30, 2019 December 31, 2018 Payroll and employee-related expenses $ 1,191 $ 1,690 Third-party research and development expenses 1,260 1,514 Professional fees 345 299 Loan interest 46 46 Other 45 76 Total accrued expenses $ 2,887 $ 3,625

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2019
Operating Leased Assets [Line Items]
Schedule of Future Minimum Commitments under Operating Leases	The following information is disclosed in accordance with ASC 840, Leases (Topic 840) December 31, 2018 2019 $ 487 2020 539 2021 30 $ 1,056
ASC 842
Operating Leased Assets [Line Items]
Schedule of Maturities of Operating Lease Liabilities	Maturities of the Company’s operating lease liabilities in accordance with ASC 842 as of June 30, 2019 are as follows (in thousands): Remainder of 2019 $ 223 2020 539 2021 30 Total maturities 792 Less: Amount representing interest (37 ) Present value of operating lease liabilities $ 755

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Summary of Shares of Common Stock Reserved	The Company has reserved for future issuances the following shares of common stock as of June 30, 2019 and December 31, 2018: June 30, 2019 December 31, 2018 Warrants 9,040 9,040 Stock options 5,087,663 4,262,341 Employee stock purchase plan 391,733 405,742 Total 5,488,436 4,677,123

Stock Incentive Plan (Tables)

Stock Incentive Plan (Tables)	6 Months Ended
	Jun. 30, 2019
Summary of Stock-based Compensation Expense	Stock-based compensation expense included in the Company’s statements of operations and comprehensive loss is as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Research and development $ 311 $ 144 $ 566 $ 234 General and administrative 461 368 835 683 Total $ 772 $ 512 $ 1,401 $ 917
Summary of Stock Option Activity	A summary of the stock option activity under the 2011 and 2017 Plans is as follows: Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life (in years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2018 2,141,527 4.32 7.7 $ 4,959 Granted 1,024,250 6.71 Exercised (7,039 ) 1.85 Cancelled (16,606 ) 6.23 Outstanding at June 30, 2019 3,142,132 $ 5.09 8.0 $ 3,237 Exercisable at June 30, 2019 1,453,371 $ 3.04 6.7 $ 2,961
Employees and Directors
Schedule of Assumptions Used in Black-Scholes Option Pricing Model to Estimate Fair Value of Stock Options	The fair value of each stock option granted to employees and directors was estimated on the date of grant using the Black-Scholes option-pricing model, with the following range of assumptions as follows: Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Risk-free interest rate 1.9%-2.3% 2.6%-2.8% 1.9%-2.6% 2.3%-2.8% Expected dividend yield —% —% —% —% Expected term (in years) 5.5-6.1 5.5-6.1 5.5-6.8 5.5-6.1 Expected volatility 82%-83% 85%-87% 82%-83% 81%-89%

Nature of Business - Additional

Nature of Business - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Jun. 28, 2019	Jun. 30, 2019	Dec. 31, 2018
Class Of Stock [Line Items]
Accumulated deficit		$ 140,297	$ 117,605
Cash and cash equivalents		$ 48,523	$ 61,643
Direct Offering
Class Of Stock [Line Items]
Common stock, shares issued and sold	2,632,092
Purchase price per share	$ 3.80
Gross proceeds from issuance of common stock	$ 10,000
Receives from issuance of common stock after deducting offering costs	$ 9,600

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 2019	Jan. 01, 2019
Summary Of Significant Accounting Policies [Line Items]
Entity incorporated date	Dec. 31, 2014
Lease, practical expedients, package	true
Operating lease, right-of-use assets	$ 745,000	$ 1,000,000
Operating lease, liabilities		1,000,000
Finance lease, right-of-use assets		0
Finance lease, liabilities		$ 0
Allena Pharmaceuticals Security Corporation
Summary Of Significant Accounting Policies [Line Items]
Entity incorporated date	Dec. 31, 2014
Allena Pharmaceuticals Ireland Limited
Summary Of Significant Accounting Policies [Line Items]
Entity incorporated date	Mar. 31, 2017

Net Loss per Share - Summary of

Net Loss per Share - Summary of Basic and Diluted Net Loss per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net loss	$ (11,273)	$ (8,647)	$ (22,692)	$ (16,527)
Net loss attributable to common stockholders	$ (11,273)	$ (8,647)	$ (22,692)	$ (16,527)
Denominator:
Weighted-average common shares—basic and diluted	20,903,298	20,733,043	20,859,251	20,714,319
Net loss per share attributable to common stockholders—basic and diluted	$ (0.54)	$ (0.42)	$ (1.09)	$ (0.80)

Net Loss per Share - Summary _2

Net Loss per Share - Summary of Anti-dilutive Securities Excluded from Calculation of Diluted Net Loss per Share (Details) - shares	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of loss per share	3,151,172	2,106,692
Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of loss per share	9,040	9,040
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of loss per share	3,142,132	2,097,652

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets	$ 48,115	$ 61,415
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets	48,115	61,415
Money market funds, included in cash and cash equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market funds, included in cash and cash equivalents	48,115	61,415
Money market funds, included in cash and cash equivalents | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market funds, included in cash and cash equivalents	$ 48,115	$ 61,415

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended	12 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Change in valuation methods or transfers	$ 0			$ 0
Transfers within fair value hierarchy		$ 0	$ 0	$ 0

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Payroll and employee-related expenses	$ 1,191	$ 1,690
Third-party research and development expenses	1,260	1,514
Professional fees	345	299
Loan interest	46	46
Other	45	76
Total accrued expenses	$ 2,887	$ 3,625

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)ft²	Jun. 30, 2018USD ($)
Operating Leased Assets [Line Items]
Lease costs	$ 0.1		$ 0.3
Operating lease, weighted average remaining lease term	1 year 6 months		1 year 6 months
Operating lease, weighted average discount rate	5.50%		5.50%
Operating leases, rent expense, net		$ 0.1		$ 0.2
Newton, MA
Operating Leased Assets [Line Items]
Rentable office space under operating lease | ft²			7,795
Base rent for office space			$ 0.3
Operating lease expiration date			Dec. 31, 2020
Sudbury, MA
Operating Leased Assets [Line Items]
Rentable office space under operating lease | ft²			7,564
Base rent for office space			$ 0.2
Operating lease expiration date			Feb. 28, 2021

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019
Lessee Lease Description [Line Items]
Present value of operating lease liabilities		$ 1,000
ASC 842
Lessee Lease Description [Line Items]
Remainder of 2019	$ 223
2020	539
2021	30
Total maturities	792
Less: Amount representing interest	(37)
Present value of operating lease liabilities	$ 755

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Future Minimum Commitments under Operating Leases (Details) $ in Thousands	Dec. 31, 2018USD ($)
Operating Leases Future Minimum Payments Due [Abstract]
2019	$ 487
2020	539
2021	30
Total future operating lease commitment	$ 1,056

Loan and Security Agreement - A

Loan and Security Agreement - Additional Information (Details) - USD ($)	Jun. 29, 2018	Dec. 31, 2016	May 31, 2016	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Aug. 31, 2014
Debt Instrument [Line Items]
Loss on extinguishment of debt				$ 617,000		$ 617,000
Loan Agreement | SVB
Debt Instrument [Line Items]
Loan agreement, maximum borrowing capacity			$ 10,000,000				$ 7,000,000
Proceeds from loan agreement		$ 2,500,000	7,500,000
Net proceeds from loan agreement			1,600,000
Repayment under loan agreement			5,300,000
Payment for final interest due upon maturity or prepayment of the original advances			$ 600,000
Loan agreement, stated interest rate		4.00%	4.00%
Loan agreement, interest rate above prime rate		0.50%	0.50%
Loan agreement, extended interest only payment period		18 months
Loan agreement, number of monthly payments					30 months
Loan agreement, frequency of payments					monthly
Percentage of final payment based on total borrowings					8.25%
Repayment of outstanding principal balance	$ 7,700,000
Loss on extinguishment of debt	600,000
Loan Agreement | PWB
Debt Instrument [Line Items]
Loan agreement, maximum borrowing capacity	$ 12,000,000
Loan agreement, interest rate above prime rate	5.00%
Loan agreement, extended interest only payment period	6 months
Loan agreement, number of monthly payments	30 months
Loan agreement, frequency of payments					monthly
Loan agreement, advanced amount	$ 10,000,000
Loan agreement, remaining borrowing capacity	$ 2,000,000
Loan agreement, term	48 months
Loan agreement, interest only payment period	18 months
Expiration of initial interest only period	Dec. 31, 2019
Loan agreement, extended additional interest only payment period	6 months
Loan agreement, number of additional monthly payments	24 months
Aggregate gross proceeds for success fee to be paid	$ 25,000,000
Success fee payable	300,000
Loan Agreement | PWB | Minimum
Debt Instrument [Line Items]
Gross proceeds from sale of equity securities or upfront cash payment	$ 50,000,000

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details)	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Common stock, voting rights	one vote for each share held

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Shares of Common Stock Reserved (Details) - shares	Jun. 30, 2019	Dec. 31, 2018
Class Of Stock [Line Items]
Shares of common stock reserved for future issuances	5,488,436	4,677,123
Warrants
Class Of Stock [Line Items]
Shares of common stock reserved for future issuances	9,040	9,040
Stock Options
Class Of Stock [Line Items]
Shares of common stock reserved for future issuances	5,087,663	4,262,341
Employee Stock Purchase Plan
Class Of Stock [Line Items]
Shares of common stock reserved for future issuances	391,733	405,742

Stock Incentive Plan - Addition

Stock Incentive Plan - Additional Information (Details) - USD ($) $ in Millions	Jan. 01, 2019	Jan. 01, 2018	Oct. 31, 2017	Jun. 30, 2019
2011 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for grant			0
2011 Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based award, vesting period				4 years
2011 Plan | Stock Options | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based award, expiration period				10 years
2017 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option grant effective date			Oct. 31, 2017
Share based award, description				Upon the adoption of the 2017 Plan, no further grants would be made under the 2011 Stock Incentive Plan (“2011 Plan”). The 2017 Plan initially provided for the grant of awards for 2,038,021 shares of common stock. In addition to the shares available for grant under the 2017 Plan, any awards outstanding under the 2011 Plan as of the October 31, 2017 are cancelled, forfeited or otherwise terminated without being exercised, the number of shares underlying such awards will be available for future grant under the 2017 Plan. The 2017 Plan also provides that an additional number of shares will automatically be added to the shares authorized for issuance under the 2017 Plan on January 1 of each year. The number of shares added each year will be equal to the lesser of: (i) 4% of the outstanding shares on the immediately preceding December 31 or (ii) such amount as determined by the Compensation Committee of the registrant’s Board of Directors. On January 1, 2018, the shares available for grant under the 2017 Plan was automatically increased by 827,786 shares. On January 1, 2019, the shares available for grant under the 2017 Plan was automatically increased by an additional 832,361 shares.
Percentage criteria for additional shares granted			4.00%
Additional shares available for grant	832,361	827,786
2017 Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for future grant				1,945,531
Stock-based award, vesting period				4 years
2017 Plan | Stock Options | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based award, expiration period				10 years
2017 Plan | Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for grant			2,038,021
2011 And 2017 Plans
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense related to unvested employee stock options				$ 7.7
Unrecognized stock-based compensation expense, weighted average period for recognition				2 years 10 months 24 days

Stock Incentive Plan - Summary

Stock Incentive Plan - Summary of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 772	$ 512	$ 1,401	$ 917
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	311	144	566	234
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 461	$ 368	$ 835	$ 683

Stock Incentive Plan - Schedule

Stock Incentive Plan - Schedule of Assumptions Used in Black-Scholes Option Pricing Model to Estimate Fair Value of Stock Options (Details) - Stock Options - Employees and Directors	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate, minimum	1.90%	2.60%	1.90%	2.30%
Risk-free interest rate, maximum	2.30%	2.80%	2.60%	2.80%
Expected volatility, minimum	82.00%	85.00%	82.00%	81.00%
Expected volatility, maximum	83.00%	87.00%	83.00%	89.00%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 6 months	5 years 6 months	5 years 6 months	5 years 6 months
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days	6 years 9 months 18 days	6 years 1 month 6 days

Stock Incentive Plan - Summar_2

Stock Incentive Plan - Summary of Stock Option Activity (Details) - 2011 And 2017 Plans - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Outstanding, Beginning balance	2,141,527
Shares, Granted	1,024,250
Shares, Exercised	(7,039)
Shares, Cancelled	(16,606)
Shares, Outstanding, Ending balance	3,142,132	2,141,527
Shares, Exercisable	1,453,371
Weighted-Average Exercise Price, Outstanding, Beginning balance	$ 4.32
Weighted-Average Exercise Price, Granted	6.71
Weighted-Average Exercise Price, Exercised	1.85
Weighted-Average Exercise Price, Cancelled	6.23
Weighted-Average Exercise Price, Outstanding, Ending balance	5.09	$ 4.32
Weighted-Average Exercise Price, Exercisable	$ 3.04
Weighted-Average Remaining Contractual Life (in years), Outstanding	8 years	7 years 8 months 12 days
Weighted-Average Remaining Contractual Life (in years), Exercisable	6 years 8 months 12 days
Aggregate Intrinsic Value, Outstanding	$ 3,237	$ 4,959
Aggregate Intrinsic Value, Exercisable	$ 2,961