Ra Pharmaceuticals (RARX) 10-Q 29 Nov 16 2016 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2016	Nov. 29, 2016
Document and Entity Information
Entity Registrant Name	Ra Pharmaceuticals, Inc.
Entity Central Index Key	1,481,512
Document Type	10-Q
Document Period End Date	Sep. 30, 2016
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	No
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		22,546,165
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q3

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 31,196	$ 19,386
Accounts receivable		6
Prepaid expenses and other current assets	669	794
Total current assets	31,865	20,186
Property and equipment, net	5,673	2,143
Intangible assets, net	278	327
Goodwill	183	183
Restricted cash	1,334	1,463
Other non-current assets	1,315	40
Total assets	40,648	24,342
Current liabilities:
Accounts payable	2,775	1,319
Accrued expenses	2,735	1,274
Deferred rent	219	104
Deferred revenue		1,621
Preferred stock tranche rights		2,620
Total current liabilities	5,729	6,938
Non-current liabilities:
Deferred rent, net of current portion	2,904	610
Deferred tax liabilities	77	77
Deferred revenue, net of current portion		241
Total liabilities	8,710	7,866
Commitments and contingencies (Note 8)
Stockholders deficit:
Common stock, $0.001 par value, 125,000,000 shares authorized at September 30, 2016 and December 31, 2015; 594,044 and 536,690 shares issued and outstanding at September 30, 2016 and December 31, 2015	1	1
Additional paid-in capital	3,330	2,700
Accumulated deficit	(57,876)	(39,900)
Total stockholders' deficit	(54,545)	(37,199)
Total liabilities, redeemable convertible preferred stock and stockholders' deficit	40,648	24,342
Series A redeemable convertible preferred stock
Redeemable convertible preferred stock:
Redeemable convertible preferred stock	27,311	27,311
Series B-1 redeemable convertible preferred stock
Redeemable convertible preferred stock:
Redeemable convertible preferred stock	26,364	26,364
Series B-2 redeemable convertible preferred stock
Current liabilities:
Preferred stock tranche rights		$ 2,620
Redeemable convertible preferred stock:
Redeemable convertible preferred stock	$ 32,808

CONDENSED CONSOLIDATED BALANCE3

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Common stock
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares issued	594,044	536,690
Common stock, shares outstanding	594,044	536,690
Series A redeemable convertible preferred stock
Redeemable convertible preferred stock
Redeemable convertible preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Redeemable convertible preferred stock, shares authorized	34,440,565	34,440,565
Redeemable convertible preferred stock, shares issued	34,440,565	34,440,565
Redeemable convertible preferred stock, shares outstanding	34,440,565	34,440,565
Redeemable convertible preferred stock, liquidation preference	$ 27,613	$ 27,613
Series B-1 redeemable convertible preferred stock
Redeemable convertible preferred stock
Redeemable convertible preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Redeemable convertible preferred stock, shares authorized	31,564,630	31,564,630
Redeemable convertible preferred stock, shares issued	31,564,630	31,564,630
Redeemable convertible preferred stock, shares outstanding	31,564,630	31,564,630
Redeemable convertible preferred stock, liquidation preference	$ 29,250	$ 29,250
Series B-2 redeemable convertible preferred stock
Redeemable convertible preferred stock
Redeemable convertible preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Redeemable convertible preferred stock, shares authorized	29,362,452	29,362,452
Redeemable convertible preferred stock, shares issued	29,362,452	0
Redeemable convertible preferred stock, shares outstanding	29,362,452	0
Redeemable convertible preferred stock, liquidation preference	$ 29,250	$ 0

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Revenue		$ 1,096	$ 4,928	$ 3,273
Operating expenses:
Research & development	$ 7,079	4,027	18,541	10,593
General & administrative	1,042	539	3,418	1,549
Total operating expenses	8,121	4,566	21,959	12,142
Loss from operations	(8,121)	(3,470)	(17,031)	(8,869)
Other income (expense):
Interest (expense) with related parties		(14)		(159)
Loss on debt extinguishment with related parties		(602)		(602)
Other income (expense)	7	154	(945)	250
Total other income (expense), net	7	(462)	(945)	(511)
Net loss	(8,114)	(3,932)	(17,976)	(9,380)
Reconciliation of net loss to net loss attributable to common shareholders:
Net loss	(8,114)	(3,932)	(17,976)	(9,380)
Gain on extinguishment of redeemable convertible preferred shares		1,673		1,673
Net loss attributable to common shareholders	$ (8,114)	$ (2,259)	$ (17,976)	$ (7,707)
Net loss per share attributable to common stockholders - basic and diluted	$ (14.22)	$ (4.57)	$ (32.73)	$ (15.84)
Weighted-average common shares used in net loss per share attributable to common stockholders - basic and diluted	570,558	494,302	549,138	486,479

CONDENSED CONSOLIDATED STATEME5

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net loss	$ (17,976)	$ (9,380)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,001	618
Accretion of discount and debt issuance costs of convertible notes with shareholders		50
Non-cash interest expense with shareholders		109
Loss on debt extinguishment with shareholders		602
Stock-based compensation	521	121
Change in fair value of preferred stock tranche rights	960	169
Change in fair value of derivative liability		(98)
Other non-cash operating activities	15	1
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	125	(300)
Accounts receivable	6	(1,443)
Other non-current assets	(925)
Accounts payable and accrued expenses	2,907	940
Deferred rent and other non current liabilities	2,409	(108)
Deferred revenue	(1,862)	(96)
Net cash used in operating activities	(12,819)	(8,815)
Cash flows from investing activities:
Purchase of property and equipment	(4,494)	(152)
Proceeds from sale of property and equipment	7	1
Decrease (increase) in restricted cash	129	(1,334)
Net cash used in investing activities	(4,358)	(1,485)
Cash flows from financing activities:
Proceeds from issuance of preferred stock	29,250	23,803
Payment of preferred stock issuance costs	(22)	(193)
Proceeds from issuance of convertible notes with shareholders		5,000
Payment of debt issuance costs		(6)
Payments of proposed public offering costs	(350)
Proceeds from exercise of common stock warrants		1
Proceeds from exercise of stock options	109	76
Net cash provided by financing activities	28,987	28,681
Net increase in cash and cash equivalents	11,810	18,381
Cash and cash equivalents, beginning of period	19,386	4,039
Cash and cash equivalents, end of period	31,196	22,420
Supplemental disclosure of noncash investing and financing activity:
Reclassification of Series B-2 tranche right liability to the balance of Series B-2 redeemable convertible preferred stock	3,580
Gain on extinguishment of Series A redeemable convertible preferred stock		1,673
Conversion of convertible notes with shareholders into Series B-1 redeemable convertible preferred stock		5,109
Changes in accounts payable and accrued expenses related to fixed asset additions	$ 10	$ 26

Nature of Business

Nature of Business	9 Months Ended
	Sep. 30, 2016
Nature of Business
Nature of Business	1. Nature of Business Ra Pharmaceuticals, Inc. (the “Company”) is a clinical-stage biopharmaceutical company using its proprietary peptide chemistry platform to create novel therapeutics to treat life-threatening diseases that are caused by excessive or uncontrolled activation of the complement system, an essential component of the body’s innate immune system. The Company’s lead product candidate, RA101495, is being developed as a convenient self-administered subcutaneous, or SC, injection, which is an injection into the tissue under the skin for the treatment of paroxysmal nocturnal hemoglobinuria, or PNH, a rare, chronic, life-threatening, blood disorder where red blood cells are mistakenly attacked and destroyed by the complement system. The Company is also developing RA101495, administered SC, to treat other debilitating complement-mediated diseases such as myasthenia gravis, or MG, and lupus nephritis, or LN. The Company is also pursuing discovery and preclinical programs targeting selective inhibition of other uncontrolled complement pathway factors to treat a variety of ophthalmologic, renal and inflammatory diseases. In addition to its focus on developing novel therapeutics to treat complement-mediated diseases, the Company has a collaboration with Merck & Co., Inc., or Merck, for a non-complement cardiovascular target. The Company was incorporated in Delaware on June 27, 2008 and is located in Cambridge, Massachusetts. During 2011, the Company acquired Cosmix Verwaltungs GmbH (“Cosmix”), organized in Germany. The condensed consolidated financial statements include the assets and liabilities and operating results of the Company and its wholly-owned subsidiary, Cosmix. In January 2016, the Company formed a wholly-owned subsidiary organized in the United Kingdom (“UK”), Ra Europe Limited for the purpose of conducting clinical trials in Europe and the UK. Since inception, the Company has devoted substantially all of its efforts to research and development, business planning, acquiring operating assets, seeking protection for its technology and product candidates, and raising capital. On October 31, 2016, we completed an initial public offering (“IPO”), in which we issued and sold 7,049,230 shares of our common stock at a public offering price of $13.00 per share, resulting in net proceeds to us of $82.9 million after deducting $6.4 million of underwriting discounts and commissions and offering costs of $2.3 million. On November 29, 2016, we completed the sale of an additional 1,057,385 shares of common stock to the underwriters under the underwriters’ option in the IPO to purchase additional shares of common stock at the public offering price of $13.00 per share, resulting in net proceeds to us of $12.8 million after deducting underwriting discounts and commissions. The shares began trading on the NASDAQ Global Market on October 26, 2016. Upon the closing of the IPO, all of the outstanding shares of convertible preferred stock automatically converted into 13,623,933 shares of common stock at the applicable conversion ratio then in effect and the outstanding warrants to purchase 222,775 shares of common stock net exercised, in accordance with their terms, into 221,573 shares of common stock.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2016
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Unaudited Interim Financial Information The condensed consolidated financial statements of the Company included herein have been prepared, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). 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 financial statements as of and for the year ended December 31, 2015, and notes thereto, included in the Company’s final prospectus for the IPO filed with the Securities and Exchange Commission pursuant to Rule 424(b)(4) on October 26, 2016 (the “Prospectus”). Basis of Presentation and Use of Estimates The accompanying condensed consolidated financial statements are unaudited. 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”). The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited financial statements. The unaudited condensed consolidated financial statements include the accounts of Ra Pharmaceuticals, Inc. and its wholly owned subsidiary. All intercompany transactions and balances of the subsidiary have been eliminated in consolidation. 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 September 30, 2016, the results of its operations for the three and nine months ended September 30, 2016 and 2015 and cash flows for the nine months ended September 30, 2016 and 2015. Such adjustments are of a normal and recurring nature. The results for the three and nine months ended September 30, 2016 are not necessarily indicative of the results for the year ending December 31, 2016, or for any future period. The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts in the financial statements and accompanying notes. Management considers many factors in selecting appropriate financial accounting policies and in developing the estimates and assumptions that are used in the preparation of the financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, which include, but are not limited to, expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates and whether historical trends are expected to be representative of future trends. Management’s estimation process often may yield a range of potentially reasonable estimates and management must select an amount that falls within that range of reasonable estimates. On an ongoing basis, the Company’s management evaluates its estimates related to, but not limited to, estimates related to convertible notes (“Convertible Notes”), bifurcated features embedded in the Convertible Notes, preferred stock tranche rights, stock-based compensation expense, clinical and pre-clinical trial accruals, and reported amounts of revenues and expenses during the period. The Company bases its estimates on historical experience and other market-specific or other relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions. Reverse Stock Split In connection with preparing for its IPO, the Company effected a one-for-seven reverse stock split of the Company’s common stock. The reverse stock split became effective on October 14, 2016. The par value and authorized shares of common stock and convertible preferred stock were not adjusted as a result of the reverse stock split. All share and per share amounts within the financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to this reverse stock split, including reclassifying an amount equal to the reduction in par value of common stock to additional paid-in capital. Summary of Significant Accounting Policies The Company’s significant accounting policies are described in Note 2, “Summary of Significant Accounting Policies,” in the Prospectus. There have been no material changes to the significant accounting policies during the period ended September 30, 2016. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”), which supersedes existing revenue recognition guidance. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The standard defines a five-step process to achieve this principle and will require companies to use more judgment and make more estimates than under the current guidance. The Company expects that these judgments and estimates will include identifying performance obligations in the customer contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. ASU 2014-09 also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts. In April 2016, the FASB issued ASU 2016-10, Revenue From Contracts With Customers: Identifying Performance Obligations and Licensing (“ASU 2016-10”), which addresses certain implementation issues and clarifies certain core revenue recognition principles of ASU 2014-09. In July 2015, the FASB voted to delay the effective date of this standard such that ASU 2014-09, as amended by ASU 2016-10, will be effective for the Company for annual periods beginning after December 15, 2017 and for interim periods within those fiscal years. Early adoption of the standard is permitted for annual periods beginning after December 15, 2016. The Company is evaluating the impact that the adoption of these ASUs will have on its financial statements. In August 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements—Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s ability to Continue as a Going Concern (“ASU 2014-15”), which provides guidance in GAAP about management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. The amendments in ASU 2014-15 are effective for the annual reporting period ending after December 15, 2016 and for annual and interim periods thereafter. Early adoption is permitted. The Company is currently evaluating the potential impact of ASU 2014-15 on its financial statements. In April 2015, the FASB issued ASU 2015-03, Interest — Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs (“ASU 2015-03”), which changes the presentation of debt issuance costs in financial statements. Under this authoritative guidance, an entity presents such costs in the balance sheet as a direct deduction from the related debt liability rather than as an asset. Amortization of the costs is reported as interest expense. The new guidance was effective for the Company beginning January 1, 2016. Early adoption was permitted. ASU 2015-03 did not have a significant impact on the Company’s financial statements. In November 2015, the FASB issued ASU 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes (“ASU 2015-17”), which changes the classification of deferred taxes in financial statements. This update requires that deferred tax liabilities and assets be classified as noncurrent on the balance sheet. The current requirement that deferred tax liabilities and assets of each jurisdiction of an entity be offset and presented as a single amount is not affected by the amendments in this update. The amendments in ASU 2015-17 are effective for annual periods beginning after December 15, 2016, and interim periods within those annual periods. Early adoption is permitted. The Company does not expect ASU 2015-17 to have an impact on its financial statements. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842 ) (“ASU 2016-02”), which changes the presentation of assets and liabilities relating to leases. The core principle of Topic 842 is that a lessee should recognize the assets and liabilities that arise from leases. All leases create an asset and a liability for the lessee in accordance with FASB Concepts Statement No. 6, Elements of Financial Statements , and, therefore, recognition of those lease assets and lease liabilities represents an improvement over previous GAAP, which did not require lease assets and lease liabilities to be recognized for most leases. The provisions of this guidance are effective for annual periods beginning after December 15, 2018, and for interim periods therein. The Company has not yet assessed the impact of this new standard on its financial statements. In March 2016, the FASB issued ASU 2016-09, Stock Compensation (Topic 718) (“ASU 2016-09”), which is intended to simplify several aspects of the accounting for share-based payment award transactions. The guidance will be effective for the fiscal year beginning after December 15, 2016, including interim periods within that year. The Company is currently evaluating the potential impact ASU 2016-09 may have on its financial position

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2016
Fair Value Measurements
Fair Value Measurements	3. Fair Value Measurements Below is a summary of assets and liabilities measured at fair value as of September 30, 2016 and December 31, 2015 (in thousands): As of September 30, 2016 Quoted Prices Significant Significant in Active Observable Unobservable Markets Inputs Inputs (Level 1) (Level 2) (Level 3) Total Financial Assets Cash equivalents - Money market funds $ $ — $ — $ Total $ $ — $ — $ As of December 31, 2015 Quoted Prices Significant Significant in Active Observable Unobservable Markets Inputs Inputs (Level 1) (Level 2) (Level 3) Total Financial Assets Cash equivalents - Money market funds $ $ — $ — $ Total $ $ — $ — $ Financial Liabilities Preferred stock tranche rights $ — $ — $ $ Total $ — $ — $ $ The Company’s cash equivalents consist principally of money market funds. Cash equivalents are stated at fair value and consist of Level 1 financial instruments in the fair value hierarchy. Preferred Stock Tranche Rights are stated at fair value and are considered Level 3 inputs because their fair value measurement is based, in part, on significant inputs not observed in the market. The Company determined the fair value of Preferred Stock Tranche Rights as described in Note 9.

Property and Equipment, net

Property and Equipment, net	9 Months Ended
	Sep. 30, 2016
Property and Equipment, net
Property and Equipment, net	4. Property and Equipment, net Property and equipment, net, consists of the following (in thousands): As of As of 2016 2015 Computer equipment and software $ $ Furniture, fixtures, and other Laboratory equipment Construction in progress — Leasehold improvements Accumulated depreciation ) ) Property and equipment, net $ $ Depreciation expense was $0.3 million and $0.2 million for the three months ended September 30, 2016 and 2015, respectively, and $1.0 million and $0.6 million for the nine months ended September 30, 2016 and 2015, respectively.

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2016
Accrued Expenses
Accrued Expenses	5. Accrued Expenses Accrued expenses consist of the following (in thousands): As of As of 2016 2015 Payroll and employee-related costs $ $ Research and development costs Consulting costs Professional fees Other Total $ $

Convertible Notes

Convertible Notes	9 Months Ended
	Sep. 30, 2016
Convertible Notes
Convertible Notes	6. Convertible Notes On April 1, 2015, the Company entered into a Convertible Note Purchase Agreement (the “Note Agreement”) with the holders of its existing Series A Preferred Stock. Upon entering the Note Agreement, the Company issued Convertible Notes and warrants to purchase 221,521 shares of the Company’s common shares. In connection with the issuance, the Company received gross proceeds of $5.0 million and incurred issuance costs of $6,000. The Convertible Notes bore interest at a rate of 8% per annum and were payable in full at the earliest of March 2018 (“Maturity Date”), an event of default as defined in the Note Agreement, or the sale of the Company. As discussed in more detail below, the notes and accrued interest thereon converted into shares of Series B-1 Preferred Stock on July 10, 2015. The Convertible Notes included certain features resulting in automatic conversion or possible early redemption. In the event the Company sold or issued shares (“Equity Securities”) resulting in cash proceeds to the Company of no less than $5 million (“Qualified Financing”), the Convertible Notes would automatically convert into the Equity Securities at a conversion price equal to the price per share paid by the investors purchasing the Equity Securities. In the event of the Company undergoing a change in control prior to the Maturity Date, the Convertible Notes would automatically convert into the right to receive 3 times the outstanding principal, plus accrued interest. Lastly, the Convertible Notes included a put feature, at the option of the holders, whereby upon an event of default, repayment of the Convertible Notes could be accelerated in the amount of outstanding principal, plus accrued interest. Each of these three features were embedded derivatives that required bifurcation and accounting as liabilities to be measured at fair value at each reporting date. The embedded features requiring separate accounting were combined and valued upon issuance using a single income valuation approach. The Company estimated the fair value of the combined embedded derivative identified above using a “with and without” income valuation approach. Under this approach, the Company estimated the present value of the fixed interest rate debt based on the fair value of similar debt instruments excluding the embedded features. This amount was then compared to the fair value of the debt instrument including the embedded features using a probability weighted approach by assigning each embedded derivative feature a probability of occurrence, with consideration provided for the settlement amount including conversion terms, prepayment penalties, the expected life of the liability and the applicable discount rate. The Company recorded approximately $0.1 million as the fair value of the combined embedded derivative liability on April 1, 2015, resulting in a debt discount. The debt discount was being amortized as interest expense over the life of the Convertible Notes under the effective interest method prior to conversion. Changes in the estimated fair value of the embedded features were recorded as a component of other income (expense) in the condensed consolidated statement of operations. As of July 10, 2015 and April 1, 2015, the Company ascribed a probability to the mandatory conversion feature upon a Qualified Financing of approximately 100% and 98%, respectively. As of July 10, 2015 and April 1, 2015, the Company ascribed a probability to the redemption feature upon a change in control of approximately 0% and 1%, respectively. For all other features included in the combined embedded derivative, the Company estimated a 0% and 1% probability of occurrence as of July 10, 2015 and April 1, 2015, respectively. The Company classified the liability within Level 3 of the fair value hierarchy as the probability factors are unobservable inputs and significant to the valuation model. On July 10, 2015, the Company received gross proceeds of approximately $24.1 million from the issuance of Series B-1 Preferred Stock to new and existing investors at a price per share of $0.92667. This transaction was a Qualified Financing and resulted in the automatic conversion of the notes into 5,512,743 shares of Series B-1 Preferred Stock at a conversion price of $0.92667 per share. Upon conversion, the Company recorded the difference between the fair value of the Series B-1 Preferred Stock issued and the carrying value of the Convertible Notes plus accrued interest as a $0.6 million loss on debt extinguishment in its condensed consolidated statement of operations. The warrants issued in connection with the Convertible Notes may be exercised at any time for shares of common stock at an exercise price of $0.01 per share. The warrants expire in March 2022. The Company estimated the fair value of these warrants as of the issuance date using a Black-Scholes option pricing model with the following assumptions: As of April 1, 2015 Risk-free interest rate % Expected dividend yield % Expected term (in years) Expected volatility % The proceeds from the Convertible Notes and warrants issuance were allocated between the notes and the warrants on a relative fair value basis. The Company allocated $0.5 million of the proceeds from the Convertible Notes to the common stock warrants and recognized this amount as additional paid-in capital with a corresponding debt discount upon issuance. As of September 30, 2016, the common stock warrants issued in connection with the Convertible Notes had not been exercised and remained outstanding. In October 2016, upon the closing of the IPO, all of the outstanding warrants net exercised, in accordance with their terms, into shares of common stock. See Note 9 for further details.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2016
Commitments and Contingencies.
Commitments and Contingencies	7. Commitments and Contingencies Significant contracts and agreements In April 2013, the Company entered into a collaboration and license agreement with Merck under which the Company granted Merck an exclusive license to develop, manufacture, and commercialize the Company’s cyclomimetrics compounds. See Note 11 for further details. Lease commitments In September 2010, the Company entered into a lease for approximately 6,500 square feet of research and development laboratories and general office space in One Kendall Square, Cambridge, Massachusetts. In September 2012, the Company amended the original lease to provide for additional space of approximately 4,000 square feet in the same facility. The Company’s lease expired on April 30, 2016. In September 2015, the Company entered into a new lease for approximately 27,000 square feet of research and development laboratories and general office space in 87 Cambridge Park Drive, Cambridge, Massachusetts. The lease commenced in September 2015 and expires in April 2023. The Company moved its operations to the space in April 2016. In connection with the new lease, the Company recorded a lease incentive obligation for reimbursable costs under a tenant improvement allowance provided by the landlord. As of September 30, 2016 and December 31, 2015, the Company has recorded a lease incentive obligation of $2.7 million and $0.4 million in deferred rent in the condensed consolidated balance sheet. The Company has accounted for all facility leases as operating leases. Rent expense was $0.2 million and $0.1 million for the three months ended September 30, 2016 and 2015, respectively, and $0.8 million and $0.2 million for the nine months ended September 30, 2016 and 2015, respectively. Future minimum commitments due under these non-cancelable operating lease agreements as of September 30, 2016 are as follows (in thousands): Years ending December 31, Operating Leases 2016 (remaining three months) $ 2017 2018 2019 2020 Thereafter Total minimum lease payments $ Restricted cash As of September 30, 2016 and December 31, 2015, the Company had restricted cash of $1.3 million and $1.5 million, respectively. During the nine months ended September 30, 2016, restricted cash decreased pursuant to the return of $0.1 million letter of credit for the Company’s facility lease at One Kendall Square that expired during the period. During the year ended December 31, 2015, restricted cash increased pursuant to a letter of credit of $1.4 million for the Company’s facility lease at 87 Cambridge Park Drive in Cambridge, Massachusetts. Letters of credit are secured by cash equivalents held in a money market fund. Litigation The Company is not a party to any litigation and does not have contingency reserves established for any litigation liabilities.

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	9 Months Ended
	Sep. 30, 2016
Redeemable Convertible Preferred Stock
Redeemable Convertible Preferred Stock	8. Redeemable Convertible Preferred Stock Series A Preferred Stock In February 2010, the Company issued 12,887,999 shares of Series A Preferred Stock pursuant to the Series A Preferred Stock agreement at a price of $0.80176 per share, for gross proceeds of $9.7 million, and the conversion of the principal and accrued interest totaling $0.6 million related to convertible notes and incurred issuance costs of $0.2 million, (the “First Tranche”). Additionally, in accordance with the terms of the Series A Preferred Stock agreement, investors were granted the right to purchase up to an additional 21,552,566 shares of the Company’s Series A Preferred Stock at a price of $0.80176, in two subsequent closings (the “Second Tranche” and “Third Tranche,” respectively), upon the Company meeting certain milestone criteria by approval of the Board of Directors and approval of investors holding a majority of the Series A Preferred Stock (the “Series A Preferred Stock Tranche Rights”). In February 2012, the Board of Directors waived certain Second Tranche milestone events provided for in the Series A Preferred Stock agreement and the Company issued 10,776,283 shares of Series A Preferred Stock at a price of $0.80176 for gross proceeds of $8.6 million and incurred issuance costs of $6,000. In March 2014, the Board of Directors waived certain Third Tranche milestone events provided for in the Series A Preferred Stock agreement and the Company issued 10,776,283 shares of Series A Preferred Stock at a price of $0.80176 for gross proceeds of $8.6 million and incurred issuance costs of $9,000. As of September 30, 2016 and December 31, 2015, the total authorized, outstanding and issued Series A Preferred Stock of the Company was 34,440,565 shares. In October 2016, upon the closing of the Company’s IPO, all outstanding shares of Series A Preferred Stock converted into 4,920,074 shares of the Company’s common stock. Series A Preferred Stock Tranche Rights The Company determined the right of the investors to purchase shares of Series A Preferred Stock in two future tranches met the definition of a freestanding financial instrument and was recognized as a liability at fair value upon the initial issuance of the First Tranche of Series A Preferred Stock in February 2010. The Company adjusted the carrying value of the Series A Preferred Stock Tranche Rights liability to its estimated fair value at each subsequent reporting date and immediately prior to the issuance of the Second and Third Tranche of Series A Preferred Stock through charges to other income (expense) in the condensed consolidated statement of operations. Upon the closing of each tranche, the marked-to-market fair value of the liability was included in the carrying value of Series A Preferred Stock issued. Immediately prior to the issuance of the Third Tranche of Series A Preferred Stock in March 2014, the Company adjusted the carrying value of the liability to its estimated fair value of $3.4 million and recorded the adjustment of $1.6 million within other income on the condensed consolidated statements of operations. The fair value of the Third Tranche obligation was determined using the fair value of the Series A Preferred Stock under the guideline public company option-pricing method on the date of the issuance. Series B Preferred Stock In July 2015, the Company issued 31,564,630 shares of Series B-1 Preferred Stock pursuant to the Series B Preferred Stock agreement at a price of $0.92667 per share for gross proceeds of $24.1 million and the conversion of the principal and accrued interest totaling $5.1 million related to the April 2015 Convertible Notes (Note 7) and incurred issuance costs of $0.2 million (the “Series B-1 Closing”). Additionally, in accordance with the terms of the Series B Preferred Stock agreement, investors were granted the right to purchase up to an additional 29,362,452 shares of the Company’s Series B-2 Preferred Stock (“Series B-2 Preferred Stock”) at a price of $0.99617 (the “Series B-2 Preferred Stock Tranche Rights”), in any number of subsequent closings upon the request of each investor (the “Subsequent Closings”) or in a mandatory closing upon the Company meeting certain milestone criteria by approval of the Board of Directors and certain investors (the “Mandatory Closing”). Upon consummation of a Mandatory Closing, if an investor fails to purchase the full amount of Series B-2 Preferred Stock allocated to the investor in the Series B Preferred Stock agreement at the Mandatory Closing, then all shares of Series A Preferred Stock and Series B Preferred Stock held by such investor will automatically be converted into shares of common stock of the Company initially on a one for one basis. In June 2016, the Board of Directors and required certain investors waived the milestone criteria and triggered the Mandatory Closing of the Series B-2 Preferred Stock. In June 2016, the Company issued 29,362,452 shares of Series B-2 Preferred Stock pursuant to the Series B Preferred Stock Agreement at a price of $0.99617 per share, for gross proceeds of $29.2 million and incurred issuance costs of $22,000 (“the Series B-2 Closing”). The Company incurred $0.2 million of costs related to the issuance of the Series B-1 Preferred Stock. $17,000 of the Series B-1 Preferred Stock issuance costs were allocated to Preferred Stock Tranche Rights relating to the Series B-2 Preferred Stock upon issuance. The amount allocated to the Series B-1 Preferred Stock was offset against the proceeds upon closing of the issuance of the first tranche of Series B Preferred Stock. The amount allocated to the future tranche rights was recorded as an offset to the tranche right liability at issuance. The Company incurred $22,000 of costs related to the issuance of the Series B-2 Preferred Stock. As of September 30, 2016 and December 31, 2015, the total authorized, outstanding and issued Series B-1 Preferred Stock of the Company was 31,564,630 shares. As of September 30, 2016, the total authorized, outstanding and issued Series B-2 Preferred Stock of the Company was 29,362,452 shares. As of December 31, 2015, the total authorized Series B-2 Preferred Stock of the Company was 29,362,452 shares, and no shares were outstanding and issued. In October 2016, upon the closing of the Company’s IPO, all outstanding shares of Series B-1 and B-2 Preferred Stock converted into 8,703,859 shares of the Company’s common stock. Series B-2 Preferred Stock Tranche Rights The Company determined the right of the investors to purchase shares of Series B-2 Preferred Stock in a Subsequent Closing or in a Mandatory Closing met the definition of a freestanding financial instrument and was recognized as a liability at fair value upon the initial issuance of the Series B-1 Preferred Stock in July 2015. As of June 14, 2016, December 31, 2015 and July 10, 2015, the Series B-2 Preferred Stock Tranche Rights liability had a fair value of $3.6 million, $2.6 million and $2.7 million, respectively. The fair value of the Series B-2 Preferred Stock Tranche Rights liability was determined using the probability-weighted present value of the benefit of the investment with the following assumptions: As of As of As of June 14, 2016 December 31, 2015 July 10, 2015 Probability of Series B-2 Preferred Stock closing % % % Expected years until Series B-2 Preferred Stock closing — Discount rate % % % Risk-free interest rate % % % Expected dividend yield % % % The Company adjusted the carrying value of the Series B-2 Preferred Stock Tranche Rights liability to its estimated fair value at each reporting date subsequent to issuance and immediately prior to the issuance of the Series B-2 Preferred Stock on June 14, 2016 through charges to other income (expense) in the condensed consolidated statement of operations. During the three and nine months ended September 30, 2016, the Company recognized total other expense of $0 and $1.0 million, respectively, related to changes in the fair value of the Series B-2 Preferred Stock Tranche Rights. The change in the carrying value of the Series A Preferred Stock Tranche Rights liability and the Series B-2 Preferred Stock Tranche Rights liability (collectively, the “Preferred Stock Tranche Rights”) on the condensed consolidated balance sheets during the nine months ended September 30, 2016 and the year ended December 31, 2015 was as follows: Nine Months Ended Year Ended 2016 2015 Beginning Balance — Issuance of Series B-2 Preferred Stock Tranche Rights — Change in Fair Value ) Issuance of Series B-2 Preferred Stock ) — Ending Balance — The Series B-2 Preferred Stock Tranche Rights liability was extinguished in June 2016 upon the issuance of the Series B-2 Preferred Stock. Immediately prior to the issuance of the Series B-2 Preferred Stock in June 2016, the Company adjusted the carrying value of the liability to its estimated fair value of $3.6 million. The rights, preferences, and privileges of the Series A, Series B-1 and Series B-2 (collectively the “Preferred Stock”) are included in the Prospectus. There were no changes to the rights, preferences, and privileges of the Preferred Stock during the nine months ended September 30, 2016.

Common Stock

Common Stock	9 Months Ended
	Sep. 30, 2016
Common Stock.
Common Stock	9. Common Stock The Company was authorized to issue up to 125,000,000 shares of common stock with a $0.001 par value per share as of September 30, 2016 and December 31, 2015. As of September 30, 2016 and December 31, 2015, the Company had 594,044 and 536,690 shares, respectively, of common stock issued and outstanding. The rights, preferences, and privileges of the Company’s common stock are included in the Prospectus. There were no changes to the rights, preferences, and privileges of the common stock during the nine months ended September 30, 2016. As of September 30, 2016 and December 31, 2015, the Company had warrants to purchase 222,775 shares of common stock issued and outstanding. In October 2016, upon the closing of the IPO, all of the outstanding warrants to purchase 222,775 shares of common stock net exercised, in accordance with their terms, into 221,573 shares of common stock. Reserve for future issuance The Company has reserved for future issuances the following number of shares of common stock: As of September 30, As of December 31, 2016 2015 Conversion of Series A Preferred Stock Conversion of Series B-1 Preferred Stock Conversion of Series B-2 Preferred Stock — Stock-based compensation awards Warrants to purchase Common Stock Total

Revenue Recognition

Revenue Recognition	9 Months Ended
	Sep. 30, 2016
Revenue Recognition
Revenue Recognition	10. Revenue Recognition Merck Collaboration and License Agreement In April 2013, the Company entered into a multi-target collaboration and license agreement with Merck to use its proprietary drug discovery technology platform to identify orally available cyclic peptides for non-complement program targets nominated by Merck and provide specific research and development services. Under the agreement, the Company granted Merck licenses under certain of its intellectual property rights to manufacture, develop and commercialize compounds and products directed to selected program targets. The agreement consists of a research phase, where the Company and Merck collaborated on identifying and pre-clinically developing orally available cyclic peptides suitable for further development by Merck, and a development and commercialization phase pursuant to which Merck has sole discretion and responsibility, including financial responsibility, for further development and commercialization of these peptides, on a program-by-program basis, from the collaboration. In April 2015, the Merck Agreement was amended to extend the research term of the collaboration to April 2016. At the signing of the Merck Agreement, Merck made an upfront non-refundable, technology license fee of $4.5 million to the Company. In addition, during the research term, which ended in April 2016, the Merck Agreement provided for reimbursement of research and development services provided by the Company in accordance with pre-specified limits for the number of the Company’s full-time equivalent employees (“FTEs”) working under the Merck Agreement. At the conclusion of the research term, Merck elected to continue the development of a non-complement cardiovascular target, for which the Company had received $3.5 million in preclinical milestone payments as of September 30, 2016. The Company has identified two deliverables in connection with the Merck Agreement: (1) rights to access the Company’s technology platform for each program target, and (2) the research & development services provided during the research term. The Company has determined that none of the deliverables have standalone value. Since the separability criteria have not been met for any of the deliverables, the deliverables are being accounted for as a single combined unit of accounting at the outset of the arrangement. The Company has recognized revenue in connection with the upfront non-refundable license fee ratably over the research term of the Merck Agreement. Payments for research and development services and reimbursement for certain lab supplies and reagents have been recognized as services are performed, and milestone payments are recognized as these milestones are achieved, assuming all other revenue recognition criteria are met. The Company has determined that the $3.5 million in milestone payments received through September 30, 2016 were substantive in nature as they were commensurate with the enhancement of value under the Merck Agreement and because the Company concluded at the start of the collaboration that there was no certainty that these milestones would be successful. Accordingly, the Company has accounted for these milestone payments under the milestone method. The Company is entitled to receive future aggregate milestone payments of up to $61.5 million for the non-complement cardiovascular target selected, consisting of remaining preclinical and clinical milestones of $16.5 million, regulatory milestones of $19.0 million, and commercial milestones of $26.0 million, and low-to-mid single digit percentage royalties on future sales, if any. Following the end of the research term, any future milestone payments will be recognized as revenue upon achievement as no further performance obligations exist for the Company under the Merck Agreement. The Company recognized revenue of $0 and $0.2 million during the three months ended September 30, 2016 and 2015, respectively, and $4.2 million and $0.8 million during the nine months ended September 30, 2016 and 2015, respectively, related to upfront, non-refundable payments. The Company recognized revenue of $0 and $0.8 million during the three months ended September 30, 2016 and 2015, respectively, and $0.6 million and $2.3 million during the nine months ended September 30, 2016 and 2015, respectively, related to research and development services performed under the agreement. In addition, the Company also recognized approximately $0 and $0.1 million during the three months ended September 30, 2016 and 2015, respectively, and $0.1 million and $0.2 million during the nine months ended September 30, 2016 and 2015, respectively, in revenue related to reimbursable expenses under the terms of the Merck Agreement. As of September 30, 2016 and December 31, 2015, the Company had $0 and $1.9 million, respectively, of deferred revenue, and, $0 and $6,000, respectively, of billed and unbilled accounts receivable pursuant to the agreement with Merck.

Stock Incentive Plan

Stock Incentive Plan	9 Months Ended
	Sep. 30, 2016
Stock Incentive Plan
Stock Incentive Plan	11. Stock Incentive Plan The Company maintains the 2010 Stock Incentive Plan (the “2010 Plan”) for employees, consultants, advisors, and directors. The 2010 Plan provides for the grant of incentive, non-qualified stock options and restricted stock grants as determined by the Board of Directors. The Company has reserved 2,495,607 shares of common stock under the 2010 Plan. As of September 30, 2016 and December 31, 2015, the Company has 101,109, and 678,781, respectively, of shares available for future issuance under the 2010 Plan. Shares of common stock issued upon exercise of stock options are generally issued from new shares of the Company. The 2010 Plan provides that the exercise price of incentive stock options cannot be less than 100% of the fair market value of the common stock on the date of the award for participants who own less than 10% of the total combined voting power of stock of the Company, and not less than 110% for participants who own more than 10% of the Company’s voting power. Options and restricted stock granted under the 2010 Plan vest over periods as determined by the Board of Directors, which generally are equal to four years. Options generally expire ten years from the date of grant. Total stock-based compensation expense recorded in research and development and general and administrative expenses, respectively, for employees, directors and non-employees during the three and nine months ended September 30, 2016 and 2015 is as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Research and development $ $ $ $ General and administrative Total $ $ $ $ As of September 30, 2016 and December 31, 2015, the total unrecognized compensation expense related to non-vested, employee and non-employee director stock options, net of related forfeiture estimates, was $4.8 million and $1.2 million, respectively. As of September 30, 2016 and December 31, 2015, the total unrecognized compensation cost related to non-vested, non-employee stock options, net of related forfeiture estimates, was $0.1 million and $0, respectively. The Company expects to recognize its remaining unrecognized stock-based compensation expense over a weighted-average period of approximately three years. The weighted-average grant date fair value per share for awards granted was $0.58 during the three months ended September 30, 2016, and was $0.48 and $0.26 during the nine months ended September 30, 2016 and 2015, respectively. The Company did not grant any awards to employee and non-employee directors during the three months ended September 30, 2015. 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 for the three and nine months ended September 30, 2016 and 2015 is as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Risk free interest rate 1.29% N/A 1.23 -1.59% % Expected dividend yield — N/A — — Expected term (in years) 6.0 N/A 6.0 - 6.1 Expected volatility 86.99% - 87.17% N/A 74.12% - 87.17% % The following table summarizes the activity of the Company’s stock option plan for the nine months ended September 30, 2016, (intrinsic values in thousands): Number of Weighted- Average Aggregate Outstanding at December 31, 2014 $ $ Granted $ Exercised ) $ Cancelled or forfeited ) $ Outstanding at December 31, 2015 $ $ Granted $ Exercised ) $ Cancelled or forfeited ) $ Outstanding at September 30, 2016 $ $ Exercisable at September 30, 2016 $ $ Vested or expected to vest at September 30, 2016 $ $ The total intrinsic value of options exercised was $47,000 and $36,000 during the three months ended September 30, 2016 and 2015, respectively, and $0.1 million and $36,000 during the nine months ended September 30, 2016 and 2015, respectively. Stock Option Grants to Non-Employees During the nine months ended September 30, 2016 and 2015, the Company granted 28,571 and 14,285, respectively, of non-qualified stock options to non-employees, excluding grants to non-employee directors. The Company did not grant any non-qualified stock options to non-employees during the three months ended September 30, 2016 and 2015. The unvested shares held by non-employees are revalued using the Company’s estimate of fair value at each reporting period through the remaining vesting period. Stock-based compensation expense related to stock option grants to non-employees was $22,000 and $7,000 during three months ended September 30, 2016 and 2015, respectively, and was $0.1 million and $0.1 million during the nine months ended September 30, 2016 and 2015, respectively. The fair value of each non-qualified stock option granted to non-employees was estimated on the date of grant and at each revaluation date using the Black-Scholes option-pricing model, with the following range of assumptions, excluding performance-based awards, during the nine months ended September 30, 2016 and 2015 is as follows (in thousands): Nine Months Ended September 30, 2016 2015 Risk free interest rate 1.46% - 1.76% 1.93% - 2.31% Expected dividend yield — — Expected term (in years) 9.4 - 10.0 9.2 - 10.0 Expected volatility 78.43% - 89.47% 75.34% - 79.89% Performance-based Stock Options In December 2015, the Company granted 5,714 non-qualified stock options to a non-employee consultant of the Company, which contain performance-based vesting criteria. Milestone events are specific to the Company’s development and progression in clinical trial studies. Stock-based compensation expense associated with this performance-based stock options is recognized if the achievement of the performance condition is considered probable using management’s best estimates. As of December 31, 2015, management determined that it was not probable these conditions would be met, and therefore no stock-based compensation expense relating to performance-based awards was recorded. As of September 30, 2016, management determined these conditions were met, and therefore stock-based compensation expense relating to this performance-based award was recorded during the nine months ended September 30, 2016. In February 2016, the Company granted 29,285 shares of qualified stock options to an employee of the Company. Vesting of the stock option award only commences upon the occurrence of a Trigger Event, which is defined in the employee’s equity agreement as the consummation of either (i) an initial public offering of the Company’s common stock and (ii) a private placement financing, in one or a series of related closings, resulting in gross proceeds to the Company of at least $20 million (the “Trigger Event”). Stock-based compensation expense associated with this performance-based stock options is recognized if the achievement of the performance condition is considered probable using management’s best estimates. As of September 30, 2016, management determined that it was not probable the Trigger Event would be met, and therefore stock-based compensation expense relating to this performance-based award was not recorded during the nine months ended September 30, 2016. In October 2016, upon the closing of the initial public offering, the vesting of this stock option award commenced.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2016
Income Taxes
Income Taxes	12. Income Taxes Deferred tax assets and deferred tax liabilities are recognized based on temporary differences between the financial reporting and tax basis of assets and liabilities using statutory rates. A valuation allowance is recorded against deferred tax assets if it is more likely than not that some or all of the deferred tax asset will not be realized. There were no significant income tax provisions or benefits for the three and nine months ended September 30, 2016 and 2015. Due to uncertainty surrounding the realization of its favorable tax attributes in future tax returns, the Company has recorded a full valuation allowance against the Company’s otherwise recognizable net deferred tax assets.

Net loss Per Share Attributable

Net loss Per Share Attributable to Common Stockholders	9 Months Ended
	Sep. 30, 2016
Net loss Per Share Attributable to Common Stockholders
Net loss Per Share Attributable to Common Stockholders	13. Net loss Per Share Attributable to Common Stockholders The Company computes basic and diluted earnings (loss) per share using a methodology that gives effect to the impact of outstanding participating securities (the “two-class method”). As the three and nine months ended September 30, 2016 and 2015 resulted in net losses, there is no income allocation required under the two-class method or dilution attributed to weighted average shares outstanding in the calculation of diluted loss per share. Basic and diluted net loss per common share are calculated as follows: Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Numerator: Net loss $ ) $ ) $ ) $ ) Gain on extinguishment of redeemable convertible preferred shares — — Net loss attributable to common stockholders — basic and diluted $ ) $ ) $ ) $ ) Denominator: Weighted-average common shares used in net loss per share attributable to common stockholders - basic and diluted Net loss per share attributable to common stockholders - basic and diluted $ ) $ ) $ ) $ ) The following Common Stock equivalents, presented on an as converted basis, were excluded from the calculation of net loss per share for the periods presented, due to their anti-dilutive effect: Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Convertible preferred stock Common stock warrants Outstanding stock options Total

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2016
Subsequent Events.
Subsequent Events	14. Subsequent Events: On October 14, 2016, the Company’s stockholders approved the 2016 Stock Award and Incentive Plan (the “2016 Plan”), which became effective on October 25, 2016. A total of 1,300,000 shares of common stock were reserved for issuance under the 2016 Plan, plus 101,109 shares originally available for future issuance under the 2010 Plan. In addition, the number of shares of common stock that may be issued under the 2016 Plan will automatically increase on each January 1, beginning on January 1, 2017 and ending on January 1, 2026, equal to the lesser of (i) 2,000,000 shares of common stock, (ii) 4% of the Company’s shares of common stock outstanding on the immediately preceding December 31 or (iii) an amount determined by the administrator of the 2016 Plan appointed by the Company’s board of directors. On October 14, 2016, the Company’s stockholders approved the 2016 Employee Stock Purchase Plan (the “ESPP”), which became effective on October 25, 2016. A total of 175,000 shares of common stock were reserved for issuance under the ESPP. In addition, the number of shares of common stock that may be issued under the ESPP will automatically increase on each January 1, beginning on January 1, 2017 and ending on January 1, 2026, equal to the lesser of (i) 300,000 shares of common stock, (ii) 1% of the Company’s shares of common stock outstanding on the immediately preceding December 31 or (iii) an amount determined by the administrator of the ESPP appointed by the Company’s board of directors. On October 14, 2016, the Company amended its certificate of incorporation to effect a one-for-seven reverse stock split of its issued and outstanding shares of common stock and a proportional adjustment to the existing conversion ratios for each series of the Company’s convertible preferred stock. Accordingly, all share and per share amounts for all periods presented in the accompanying interim condensed consolidated financial statements and notes thereto have been adjusted retroactively, where applicable, to reflect this reverse stock split and adjustment of the preferred stock conversion ratios. On October 31, 2016, we completed an IPO, in which we issued and sold 7,049,230 shares of our common stock at a public offering price of $13.00 per share, resulting in net proceeds to us of $82.9 million after deducting $6.4 million of underwriting discounts and commissions and offering costs of $2.3 million. On November 29, 2016, we completed the sale of an additional 1,057,385 shares of common stock to the underwriters under the underwriters’ option in the IPO to purchase additional shares of common stock at the public offering price of $13.00 per share, resulting in additional net proceeds to us of $12.8 million after deducting discounts and commissions. The shares began trading on the NASDAQ Global Market on October 26, 2016. Upon the closing of the IPO, all of the outstanding shares of convertible preferred stock automatically converted into 13,623,933 shares of common stock at the applicable conversion ratio then in effect and the outstanding warrants to purchase 222,775 shares of common stock net exercised, in accordance with their terms, into 221,573 shares of common stock.

Summary of Significant Accoun20

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2016
Summary of Significant Accounting Policies
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates The accompanying condensed consolidated financial statements are unaudited. 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”). The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited financial statements. The unaudited condensed consolidated financial statements include the accounts of Ra Pharmaceuticals, Inc. and its wholly owned subsidiary. All intercompany transactions and balances of the subsidiary have been eliminated in consolidation. 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 September 30, 2016, the results of its operations for the three and nine months ended September 30, 2016 and 2015 and cash flows for the nine months ended September 30, 2016 and 2015. Such adjustments are of a normal and recurring nature. The results for the three and nine months ended September 30, 2016 are not necessarily indicative of the results for the year ending December 31, 2016, or for any future period. The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts in the financial statements and accompanying notes. Management considers many factors in selecting appropriate financial accounting policies and in developing the estimates and assumptions that are used in the preparation of the financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, which include, but are not limited to, expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates and whether historical trends are expected to be representative of future trends. Management’s estimation process often may yield a range of potentially reasonable estimates and management must select an amount that falls within that range of reasonable estimates. On an ongoing basis, the Company’s management evaluates its estimates related to, but not limited to, estimates related to convertible notes (“Convertible Notes”), bifurcated features embedded in the Convertible Notes, preferred stock tranche rights, stock-based compensation expense, clinical and pre-clinical trial accruals, and reported amounts of revenues and expenses during the period. The Company bases its estimates on historical experience and other market-specific or other relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”), which supersedes existing revenue recognition guidance. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The standard defines a five-step process to achieve this principle and will require companies to use more judgment and make more estimates than under the current guidance. The Company expects that these judgments and estimates will include identifying performance obligations in the customer contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. ASU 2014-09 also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts. In April 2016, the FASB issued ASU 2016-10, Revenue From Contracts With Customers: Identifying Performance Obligations and Licensing (“ASU 2016-10”), which addresses certain implementation issues and clarifies certain core revenue recognition principles of ASU 2014-09. In July 2015, the FASB voted to delay the effective date of this standard such that ASU 2014-09, as amended by ASU 2016-10, will be effective for the Company for annual periods beginning after December 15, 2017 and for interim periods within those fiscal years. Early adoption of the standard is permitted for annual periods beginning after December 15, 2016. The Company is evaluating the impact that the adoption of these ASUs will have on its financial statements. In August 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements—Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s ability to Continue as a Going Concern (“ASU 2014-15”), which provides guidance in GAAP about management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. The amendments in ASU 2014-15 are effective for the annual reporting period ending after December 15, 2016 and for annual and interim periods thereafter. Early adoption is permitted. The Company is currently evaluating the potential impact of ASU 2014-15 on its financial statements. In April 2015, the FASB issued ASU 2015-03, Interest — Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs (“ASU 2015-03”), which changes the presentation of debt issuance costs in financial statements. Under this authoritative guidance, an entity presents such costs in the balance sheet as a direct deduction from the related debt liability rather than as an asset. Amortization of the costs is reported as interest expense. The new guidance was effective for the Company beginning January 1, 2016. Early adoption was permitted. ASU 2015-03 did not have a significant impact on the Company’s financial statements. In November 2015, the FASB issued ASU 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes (“ASU 2015-17”), which changes the classification of deferred taxes in financial statements. This update requires that deferred tax liabilities and assets be classified as noncurrent on the balance sheet. The current requirement that deferred tax liabilities and assets of each jurisdiction of an entity be offset and presented as a single amount is not affected by the amendments in this update. The amendments in ASU 2015-17 are effective for annual periods beginning after December 15, 2016, and interim periods within those annual periods. Early adoption is permitted. The Company does not expect ASU 2015-17 to have an impact on its financial statements. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842 ) (“ASU 2016-02”), which changes the presentation of assets and liabilities relating to leases. The core principle of Topic 842 is that a lessee should recognize the assets and liabilities that arise from leases. All leases create an asset and a liability for the lessee in accordance with FASB Concepts Statement No. 6, Elements of Financial Statements , and, therefore, recognition of those lease assets and lease liabilities represents an improvement over previous GAAP, which did not require lease assets and lease liabilities to be recognized for most leases. The provisions of this guidance are effective for annual periods beginning after December 15, 2018, and for interim periods therein. The Company has not yet assessed the impact of this new standard on its financial statements. In March 2016, the FASB issued ASU 2016-09, Stock Compensation (Topic 718) (“ASU 2016-09”), which is intended to simplify several aspects of the accounting for share-based payment award transactions. The guidance will be effective for the fiscal year beginning after December 15, 2016, including interim periods within that year. The Company is currently evaluating the potential impact ASU 2016-09 may have on its financial position

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2016
Fair Value Measurements
Schedule of assets and liabilities measured at fair value	Below is a summary of assets and liabilities measured at fair value as of September 30, 2016 and December 31, 2015 (in thousands): As of September 30, 2016 Quoted Prices Significant Significant in Active Observable Unobservable Markets Inputs Inputs (Level 1) (Level 2) (Level 3) Total Financial Assets Cash equivalents - Money market funds $ $ — $ — $ Total $ $ — $ — $ As of December 31, 2015 Quoted Prices Significant Significant in Active Observable Unobservable Markets Inputs Inputs (Level 1) (Level 2) (Level 3) Total Financial Assets Cash equivalents - Money market funds $ $ — $ — $ Total $ $ — $ — $ Financial Liabilities Preferred stock tranche rights $ — $ — $ $ Total $ — $ — $ $

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	9 Months Ended
	Sep. 30, 2016
Property and Equipment, net
Schedule of property and equipment, net	Property and equipment, net, consists of the following (in thousands): As of As of 2016 2015 Computer equipment and software $ $ Furniture, fixtures, and other Laboratory equipment Construction in progress — Leasehold improvements Accumulated depreciation ) ) Property and equipment, net $ $

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2016
Accrued Expenses
Schedule of accrued expenses	Accrued expenses consist of the following (in thousands): As of As of 2016 2015 Payroll and employee-related costs $ $ Research and development costs Consulting costs Professional fees Other Total $ $

Convertible Notes (Tables)

Convertible Notes (Tables)	9 Months Ended
	Sep. 30, 2016
Convertible Notes
Schedule of assumptions used in estimating fair value of warrants	As of April 1, 2015 Risk-free interest rate % Expected dividend yield % Expected term (in years) Expected volatility %

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2016
Commitments and Contingencies.
Schedule of future minimum commitments due under non-cancelable operating lease agreements	Future minimum commitments due under these non-cancelable operating lease agreements as of September 30, 2016 are as follows (in thousands): Years ending December 31, Operating Leases 2016 (remaining three months) $ 2017 2018 2019 2020 Thereafter Total minimum lease payments $

Redeemable Convertible Prefer26

Redeemable Convertible Preferred Stock (Tables)	9 Months Ended
	Sep. 30, 2016
Redeemable Convertible Preferred Stock
Schedule of assumptions to determine fair value of the Series B-2 Preferred Stock Tranche Rights liability	As of As of As of June 14, 2016 December 31, 2015 July 10, 2015 Probability of Series B-2 Preferred Stock closing % % % Expected years until Series B-2 Preferred Stock closing — Discount rate % % % Risk-free interest rate % % % Expected dividend yield % % %
Schedule of the change in fair value of the tranche rights liability	Nine Months Ended Year Ended 2016 2015 Beginning Balance — Issuance of Series B-2 Preferred Stock Tranche Rights — Change in Fair Value ) Issuance of Series B-2 Preferred Stock ) — Ending Balance —

Common Stock (Tables)

Common Stock (Tables)	9 Months Ended
	Sep. 30, 2016
Common Stock.
Schedule of shares of common stock reserved for future issuances	As of September 30, As of December 31, 2016 2015 Conversion of Series A Preferred Stock Conversion of Series B-1 Preferred Stock Conversion of Series B-2 Preferred Stock — Stock-based compensation awards Warrants to purchase Common Stock Total

Stock Incentive Plan (Tables)

Stock Incentive Plan (Tables)	9 Months Ended
	Sep. 30, 2016
Stock Incentive Plan
Schedule of stock-based compensation expense	Total stock-based compensation expense recorded in research and development and general and administrative expenses, respectively, for employees, directors and non-employees during the three and nine months ended September 30, 2016 and 2015 is as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Research and development $ $ $ $ General and administrative Total $ $ $ $
Schedule of stock option activity	The following table summarizes the activity of the Company’s stock option plan for the nine months ended September 30, 2016, (intrinsic values in thousands): Number of Weighted- Average Aggregate Outstanding at December 31, 2014 $ $ Granted $ Exercised ) $ Cancelled or forfeited ) $ Outstanding at December 31, 2015 $ $ Granted $ Exercised ) $ Cancelled or forfeited ) $ Outstanding at September 30, 2016 $ $ Exercisable at September 30, 2016 $ $ Vested or expected to vest at September 30, 2016 $ $
Employee and director stock options
Stock Incentive Plan
Schedule of assumptions used to calculate 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 for the three and nine months ended September 30, 2016 and 2015 is as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Risk free interest rate 1.29% N/A 1.23 -1.59% % Expected dividend yield — N/A — — Expected term (in years) 6.0 N/A 6.0 - 6.1 Expected volatility 86.99% - 87.17% N/A 74.12% - 87.17% %
Non-employee stock options
Stock Incentive Plan
Schedule of assumptions used to calculate fair value of stock options	The fair value of each non-qualified stock option granted to non-employees was estimated on the date of grant and at each revaluation date using the Black-Scholes option-pricing model, with the following range of assumptions, excluding performance-based awards, during the nine months ended September 30, 2016 and 2015 is as follows (in thousands): Nine Months Ended September 30, 2016 2015 Risk free interest rate 1.46% - 1.76% 1.93% - 2.31% Expected dividend yield — — Expected term (in years) 9.4 - 10.0 9.2 - 10.0 Expected volatility 78.43% - 89.47% 75.34% - 79.89%

Net loss Per Share Attributab29

Net loss Per Share Attributable to Common Stockholders (Tables)	9 Months Ended
	Sep. 30, 2016
Net loss Per Share Attributable to Common Stockholders
Schedule of basic and diluted net loss per common share	Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Numerator: Net loss $ ) $ ) $ ) $ ) Gain on extinguishment of redeemable convertible preferred shares — — Net loss attributable to common stockholders — basic and diluted $ ) $ ) $ ) $ ) Denominator: Weighted-average common shares used in net loss per share attributable to common stockholders - basic and diluted Net loss per share attributable to common stockholders - basic and diluted $ ) $ ) $ ) $ )
Schedule of Common Stock equivalents excluded from the calculation of net loss due to anti-dilutive effect	Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Convertible preferred stock Common stock warrants Outstanding stock options Total

Nature of Business (Details)

Nature of Business (Details) - USD ($) $ / shares in Units, $ in Thousands	Nov. 29, 2016	Oct. 31, 2016	Oct. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Nature of Business
Payment of offering expenses				$ 22	$ 193
Common Stock
Nature of Business
Number of shares into which the warrants may be converted				222,775		222,775
IPO | Common Stock | Subsequent Events
Nature of Business
New share issues		7,049,230
Share price (in dollars per share)		$ 13	$ 13
Proceeds from initial public offering		$ 82,900
Underwriting discounts and commissions		6,400
Payment of offering expenses		$ 2,300
Shares issued upon conversion		13,623,933
Number of shares into which the warrants may be converted		222,775	222,775
Shares issued from warrants exercised		221,573	221,573
Over-Allotment Option | Common Stock | Subsequent Events
Nature of Business
New share issues	1,057,385
Share price (in dollars per share)	$ 13
Proceeds from initial public offering	$ 12,800

Summary of Significant Accoun31

Summary of Significant Accounting Policies (Details)	Oct. 14, 2016
Subsequent Events
Summary of Significant Accounting Policies
Stock split ratio	0.142857

Fair Value Measurements (Detail

Fair Value Measurements (Details) - Total - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Financial Assets
Total	$ 30,958	$ 19,049
Financial Liabilities
Preferred stock tranche rights		2,620
Total		2,620
Quoted Prices in Active Markets (Level 1)
Financial Assets
Total	30,958	19,049
Significant Unobservable Inputs (Level 3)
Financial Liabilities
Preferred stock tranche rights		2,620
Total		2,620
Money market funds
Financial Assets
Cash equivalents	30,958	19,049
Money market funds | Quoted Prices in Active Markets (Level 1)
Financial Assets
Cash equivalents	$ 30,958	$ 19,049

Property and Equipment, net (De

Property and Equipment, net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Property and Equipment, net
Property and equipment, gross	$ 7,643		$ 7,643		$ 4,402
Accumulated depreciation	(1,970)		(1,970)		(2,259)
Property and equipment, net	5,673		5,673		2,143
Depreciation, Depletion and Amortization	300	$ 200	1,001	$ 618
Computer equipment and software
Property and Equipment, net
Property and equipment, gross	43		43		71
Furniture, fixtures, and other
Property and Equipment, net
Property and equipment, gross	365		365		62
Laboratory equipment
Property and Equipment, net
Property and equipment, gross	3,503		3,503		2,941
Construction in progress
Property and Equipment, net
Property and equipment, gross					535
Leasehold improvements
Property and Equipment, net
Property and equipment, gross	$ 3,732		$ 3,732		$ 793

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Accrued Expenses
Payroll and employee-related costs	$ 805	$ 60
Research and development costs	1,217	545
Consulting costs	135	122
Professional fees	493	62
Other	85	485
Total	$ 2,735	$ 1,274

Convertible Notes - Details and

Convertible Notes - Details and features of convertible notes (Details) $ / shares in Units, $ in Thousands	Jul. 10, 2015USD ($)$ / sharesshares	Apr. 01, 2015USD ($)itemshares	Jul. 31, 2015USD ($)$ / shares	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)$ / shares	Sep. 30, 2015USD ($)
Convertible notes disclosures
Proceeds from issuance of convertible notes with shareholders						$ 5,000
Payment of debt issuance costs						6
Proceeds from issuance of preferred stock					$ 29,250	23,803
Loss on debt extinguishment				$ 602		$ 602
Series B-1 redeemable convertible preferred stock
Convertible notes disclosures
Proceeds from issuance of preferred stock	$ 24,100		$ 24,100
Price per share of stock issued | $ / shares	$ 0.92667		$ 0.92667
Convertible Debt | Note Agreement
Convertible notes disclosures
Proceeds from issuance of convertible notes with shareholders		$ 5,000
Payment of debt issuance costs		$ 6,000
Debt instrument stated interest rate		8.00%
Minimum threshold of cash proceeds from the sale or issuance of shares that would trigger an automatic conversion of debt into equity securities (Qualified Financing)		$ 5,000
Multiple of outstanding principal amount that debt converts into in the event of a change in control | item		3
Number of automatic conversion features of debt instrument | item		3
Fair value of embedded derivative liability		$ 100
Probability of meeting qualified financing that triggers automatic conversion of debt into equity securities	100.00%	98.00%
Probability of debt being automatically redeemed due to a change in control	0.00%	1.00%
Probability of debt being automatically converted or redeemed due to other features	0.00%	1.00%
Warrant exercise price per share | $ / shares					$ 0.01
Convertible Debt | Note Agreement | Series B-1 redeemable convertible preferred stock
Convertible notes disclosures
Shares of stock issued upon qualified financing automatic conversion of notes | shares	5,512,743
Debt instrument conversion price per share | $ / shares	$ 0.92667
Loss on debt extinguishment	$ 600
Convertible Debt | Note Agreement | Common stock warrants
Convertible notes disclosures
Number of shares into which the warrants may be converted | shares		221,521

Convertible Notes - Assumptions

Convertible Notes - Assumptions used in determination of fair value (Details) - Common stock warrants - USD ($) $ in Millions	Apr. 01, 2015	Sep. 30, 2016
Assumptions
Proceeds from convertible notes allocated to warrants and recognized as additional paid-in capital		$ 0.5
Black-Scholes
Assumptions
Risk-free interest rate (as a percent)	1.65%
Expected dividend yield (as a percent)	0.00%
Expected term (in years)	7 years
Expected volatility (as a percent)	86.00%

Commitments and Contingencies -

Commitments and Contingencies - Lease commitments and restricted cash (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)ft²	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)ft²	Dec. 31, 2015USD ($)	Sep. 30, 2012ft²	Sep. 30, 2010ft²
Lease commitments
Rent expense	$ 200	$ 100	$ 800	$ 200
Restricted cash
Restricted cash	1,300		1,300		$ 1,500
Increase (decrease) in restricted cash			(129)	$ 1,334
One Kendall Square, Cambridge, Massachusetts
Lease commitments
Leased area (in square feet) | ft²							6,500
Additional area leased per the amended lease agreement (in square feet) | ft²						4,000
Restricted cash
Increase (decrease) in restricted cash			(100)
87 Cambridge Park Drive, Cambridge, Massachusetts
Lease commitments
Leased area (in square feet) | ft²		27,000		27,000
Restricted cash
Increase (decrease) in restricted cash					1,400
87 Cambridge Park Drive, Cambridge, Massachusetts | Deferred rent
Lease commitments
Lease incentive obligation	$ 2,700		$ 2,700		$ 400

Commitments and Contingencies38

Commitments and Contingencies - Future minimum commitments (Details) $ in Thousands	Sep. 30, 2016USD ($)
Future minimum commitments due under the non-cancelable operating lease agreements
2016 (remaining three months)	$ 249
2,017	1,222
2,018	1,358
2,019	1,396
2,020	1,435
Thereafter	3,502
Total minimum lease payments	$ 9,162

Redeemable Convertible Prefer39

Redeemable Convertible Preferred Stock - Series A Preferred Stock (Details)	1 Months Ended				9 Months Ended
	Oct. 31, 2016shares	Mar. 31, 2014USD ($)$ / sharesshares	Feb. 29, 2012USD ($)$ / sharesshares	Feb. 28, 2010USD ($)tranche$ / sharesshares	Sep. 30, 2016USD ($)shares	Sep. 30, 2015USD ($)	Dec. 31, 2015shares
Redeemable Convertible Preferred Stock
Proceeds from issuance of preferred stock | $					$ 29,250,000	$ 23,803,000
Principal and accrued interest converted | $						$ 5,109,000
Series A redeemable convertible preferred stock
Redeemable Convertible Preferred Stock
Shares issued (in shares)		10,776,283	10,776,283	12,887,999
Share price (in dollars per share) | $ / shares		$ 0.80176	$ 0.80176	$ 0.80176
Proceeds from issuance of preferred stock | $		$ 8,600,000	$ 8,600,000	$ 9,700,000
Principal and accrued interest converted | $				600,000
Stock issuance costs | $		$ 9,000	$ 6,000	$ 200,000
Investors granted right to purchase shares (in shares)				21,552,566
Investors granted right to purchase shares, share price (in dollars per share) | $ / shares				$ 0.80176
Number of tranches | tranche				2
Shares authorized (in shares)					34,440,565		34,440,565
Shares outstanding (in shares)					34,440,565		34,440,565
Shares issued (in shares)					34,440,565		34,440,565
Shares of common stock upon conversion (in shares)	4,920,074

Redeemable Convertible Prefer40

Redeemable Convertible Preferred Stock - Series A Preferred Stock Tranche Rights (Details) $ in Thousands	1 Months Ended	9 Months Ended
	Mar. 31, 2014USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)	Dec. 31, 2015USD ($)	Feb. 28, 2010tranche
Redeemable Convertible Preferred Stock
Preferred stock tranche rights				$ 2,620
Fair value adjustment		$ (960)	$ (169)
Series A redeemable convertible preferred stock
Redeemable Convertible Preferred Stock
Number of tranches | tranche					2
Preferred stock tranche rights	$ 3,400
Series A redeemable convertible preferred stock | Other Nonoperating Income (Expense).
Redeemable Convertible Preferred Stock
Fair value adjustment	$ 1,600

Redeemable Convertible Prefer41

Redeemable Convertible Preferred Stock - Series B Preferred Stock (Details) - USD ($)	Jul. 10, 2015	Oct. 31, 2016	Jun. 30, 2016	Jul. 31, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Redeemable Convertible Preferred Stock
Proceeds from issuance of preferred stock					$ 29,250,000	$ 23,803,000
Principal and accrued interest converted						$ 5,109,000
Series B redeemable convertible preferred stock
Redeemable Convertible Preferred Stock
Shares of common stock upon conversion (in shares)		8,703,859
Series B-1 redeemable convertible preferred stock
Redeemable Convertible Preferred Stock
Shares issued (in shares)				31,564,630
Share price (in dollars per share)	$ 0.92667			$ 0.92667
Proceeds from issuance of preferred stock	$ 24,100,000			$ 24,100,000
Principal and accrued interest converted				5,100,000
Stock issuance costs			$ 200,000	$ 200,000
Shares authorized (in shares)					31,564,630		31,564,630
Shares outstanding (in shares)					31,564,630		31,564,630
Shares issued (in shares)					31,564,630		31,564,630
Series B-2 redeemable convertible preferred stock
Redeemable Convertible Preferred Stock
Shares issued (in shares)			29,362,452
Share price (in dollars per share)			$ 0.99617
Proceeds from issuance of preferred stock			$ 29,200,000
Stock issuance costs			22,000
Investors granted right to purchase shares (in shares)				29,362,452
Investors granted right to purchase shares, share price (in dollars per share)				$ 0.99617
Conversion basis (in shares)				1
Stock issuance costs allocated to Preferred Stock Tranche Rights			$ 17,000
Shares authorized (in shares)					29,362,452		29,362,452
Shares outstanding (in shares)					29,362,452		0
Shares issued (in shares)					29,362,452		0

Redeemable Convertible Prefer42

Redeemable Convertible Preferred Stock - Series B-2 Preferred Stock Tranche Rights Liability (Details) - USD ($) $ in Thousands	Jun. 14, 2016	Dec. 31, 2015	Jul. 10, 2015
Redeemable Convertible Preferred Stock
Preferred stock tranche rights		$ 2,620
Series B-2 redeemable convertible preferred stock
Redeemable Convertible Preferred Stock
Preferred stock tranche rights	$ 3,600	$ 2,620	$ 2,700

Redeemable Convertible Prefer43

Redeemable Convertible Preferred Stock - Series B-2 Preferred Stock Tranche Rights Liability Assumptions (Details) - Series B-2 redeemable convertible preferred stock	Jun. 14, 2016	Dec. 31, 2015	Jul. 10, 2015
Assumptions
Probability of Series B-2 Preferred Stock closing (as a percent)	100.00%	80.00%	85.00%
Expected years until Series B-2 Preferred Stock closing (in years)		6 months	8 months 12 days
Discount rate (as a percent)	0.00%	19.00%	18.00%
Risk-free interest rate (as a percent)	0.00%	2.70%	2.90%
Expected dividend yield (as a percent)	0.00%	0.00%	0.00%

Redeemable Convertible Prefer44

Redeemable Convertible Preferred Stock - Series B-2 Preferred Stock Tranche Rights Liability Fair Value Adjustment (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Redeemable Convertible Preferred Stock
Fair value adjustment		$ 960	$ 169
Series B-2 redeemable convertible preferred stock
Redeemable Convertible Preferred Stock
Fair value adjustment		960		$ (74)
Series B-2 redeemable convertible preferred stock | Other Nonoperating Income (Expense).
Redeemable Convertible Preferred Stock
Fair value adjustment	$ 0	$ 1,000

Redeemable Convertible Prefer45

Redeemable Convertible Preferred Stock - Series B-2 Preferred Stock Tranche Rights Change in Carrying Value (Details) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Redeemable Convertible Preferred Stock
Beginning Balance	$ 2,620
Change in fair value of preferred stock tranche rights	960	$ 169
Issuance of Series B-2 Preferred Stock	(3,580)
Ending Balance			$ 2,620
Series B-2 redeemable convertible preferred stock
Redeemable Convertible Preferred Stock
Beginning Balance	2,620
Issuance of Series B-2 Preferred Stock Tranche Rights			2,694
Change in fair value of preferred stock tranche rights	960		(74)
Issuance of Series B-2 Preferred Stock	$ (3,580)
Ending Balance			$ 2,620

Common Stock - Common stock par

Common Stock - Common stock par and shares authorized, issued and outstanding (Details) - $ / shares	Sep. 30, 2016	Dec. 31, 2015
Common Stock.
Common stock, shares authorized	125,000,000	125,000,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares issued	594,044	536,690
Common stock, shares outstanding	594,044	536,690

Common Stock - Additional infor

Common Stock - Additional information (Details) - Common Stock - shares	Oct. 31, 2016	Oct. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Sale of stock
Number of shares into which the warrants may be converted			222,775	222,775
IPO | Subsequent Events
Sale of stock
Number of shares into which the warrants may be converted	222,775	222,775
Shares issued from warrants exercised	221,573	221,573

Common Stock - Shares reserved

Common Stock - Shares reserved for future issuances (Details) - shares	Sep. 30, 2016	Dec. 31, 2015
Common stock
Shares reserved for future issuances	16,043,311	11,165,804
Common stock warrants
Common stock
Shares reserved for future issuances	222,775	222,775
Stock-based compensation awards
Common stock
Shares reserved for future issuances	2,196,603	1,513,727
Series A redeemable convertible preferred stock
Common stock
Shares reserved for future issuances	4,920,074	4,920,074
Series B-1 redeemable convertible preferred stock
Common stock
Shares reserved for future issuances	4,509,228	4,509,228
Series B-2 redeemable convertible preferred stock
Common stock
Shares reserved for future issuances	4,194,631

Revenue Recognition (Details)

Revenue Recognition (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 30, 2013	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Collaborative Arrangements
Revenues			$ 1,096,000	$ 4,928,000	$ 3,273,000
Billed and unbilled accounts receivable						$ 6,000
Merck | Product related collaborative arrangement
Collaborative Arrangements
Payments received	$ 4,500,000
Deferred Revenue		$ 0		0		1,900,000
Billed and unbilled accounts receivable		0		0		$ 6,000
Merck | Product related collaborative arrangement | Upfront non-refundable payments
Collaborative Arrangements
Revenues		0	200,000	4,200,000	800,000
Merck | Product related collaborative arrangement | Research and development
Collaborative Arrangements
Revenues		0	800,000	600,000	2,300,000
Merck | Product related collaborative arrangement | Reimbursable expense
Collaborative Arrangements
Revenues		$ 0	$ 100,000	100,000	$ 200,000
Merck | Product related collaborative arrangement | Preclinical milestones
Collaborative Arrangements
Milestone payment received				3,500,000
Merck | Product related collaborative arrangement | Preclinical and clinical milestones
Collaborative Arrangements
Future milestone payments				16,500,000
Merck | Product related collaborative arrangement | Regulatory milestones
Collaborative Arrangements
Future milestone payments				19,000,000
Merck | Product related collaborative arrangement | Commercial milestones
Collaborative Arrangements
Future milestone payments				26,000,000
Merck | Product related collaborative arrangement | Maximum
Collaborative Arrangements
Future milestone payments				$ 61,500,000

Stock Incentive Plan - Incentiv

Stock Incentive Plan - Incentive plan information (Details) - shares	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Stock Incentive Plan
Common stock reserved under the Plan	16,043,311	11,165,804
2010 Stock Incentive Plan (the "2010 Plan")
Stock Incentive Plan
Common stock reserved under the Plan	2,495,607
Shares available for future issuance	101,109	678,781
Vesting period	4 years
Stock options | 2010 Stock Incentive Plan (the "2010 Plan")
Stock Incentive Plan
Expiration period	10 years
Stock options | Less than 10% voting power | 2010 Stock Incentive Plan (the "2010 Plan")
Stock Incentive Plan
Minimum exercise price, as a percent to fair market value of common stock	100.00%
Stock options | Less than 10% voting power | 2010 Stock Incentive Plan (the "2010 Plan") | Maximum
Stock Incentive Plan
Voting power (as a percent)	10.00%
Stock options | More than 10% voting power | 2010 Stock Incentive Plan (the "2010 Plan")
Stock Incentive Plan
Minimum exercise price, as a percent to fair market value of common stock	110.00%
Stock options | More than 10% voting power | 2010 Stock Incentive Plan (the "2010 Plan") | Minimum
Stock Incentive Plan
Voting power (as a percent)	10.00%

Stock Incentive Plan - Stock-ba

Stock Incentive Plan - Stock-based compensation expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Stock Incentive Plan
Stock-based compensation expense	$ 251	$ 30	$ 521	$ 121
Research and development
Stock Incentive Plan
Stock-based compensation expense	149	18	309	67
General and administrative
Stock Incentive Plan
Stock-based compensation expense	$ 102	$ 12	$ 212	$ 54

Stock Incentive Plan - Employee

Stock Incentive Plan - Employee, director and non-employee stock options (Details) - USD ($)	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Stock Incentive Plan
Stock-based compensation expense		$ 251,000	$ 30,000	$ 521,000	$ 121,000
2010 Stock Incentive Plan (the "2010 Plan") | Stock options
Stock Incentive Plan
Weighted-average grant date fair value per share (in dollars per share)		$ 0.58		$ 0.48	$ 0.26
Number of Shares
Outstanding, beginning				834,946	290,948	290,948
Granted				1,464,972		656,292
Exercised				(57,354)		(51,508)
Cancelled or forfeited				(147,070)		(60,786)
Outstanding, ending	290,948	2,095,494		2,095,494		834,946
Exercisable		232,773		232,773
Vested or expected to vest		1,937,054		1,937,054
Weighted Average Exercise Price
Outstanding, beginning (in dollars per share)				$ 2.66	$ 1.82	$ 1.82
Granted (in dollars per share)				4.55		2.87
Exercised (in dollars per share)				1.89		1.61
Cancelled or forfeited (in dollars per share)				2.87		1.75
Outstanding, ending (in dollars per share)	$ 1.82	$ 3.99		3.99		$ 2.66
Exercisable (in dollars per share)		2.59		2.59
Vested or expected to vest (in dollars per share)		$ 3.92		$ 3.92
Average Remaining Contractual Life (in years)
Outstanding	8 years 9 months 18 days			9 years 4 months 24 days		9 years 1 month 6 days
Exercisable				8 years 3 months 18 days
Vested or expected to vest				9 years 4 months 24 days
Aggregate Intrinsic Value
Outstanding	$ 306,000	$ 3,429,000		$ 3,429,000		$ 174,000
Exercisable		704,000		704,000
Vested or expected to vest		3,221,000		3,221,000
Total intrinsic value of options exercised		47,000	36,000	100,000	$ 36,000
2010 Stock Incentive Plan (the "2010 Plan") | Employee and director stock options
Stock Incentive Plan
Unrecognized compensation expense		$ 4,800,000		$ 4,800,000		1,200,000
Period over which remaining unrecognized stock-based compensation expense is recognized				3 years
Assumptions used in the valuation model
Risk free interest rate		1.29%			1.76%
Risk free interest rate, minimum				1.23%
Risk free interest rate, maximum				1.59%
Expected term (in years)		6 years			6 years
Expected volatility					73.32%
Expected volatility, minimum		86.99%		74.12%
Expected volatility, maximum		87.17%		87.17%
2010 Stock Incentive Plan (the "2010 Plan") | Employee and director stock options | Minimum
Assumptions used in the valuation model
Expected term (in years)				6 years
2010 Stock Incentive Plan (the "2010 Plan") | Employee and director stock options | Maximum
Assumptions used in the valuation model
Expected term (in years)				6 years 1 month 6 days
2010 Stock Incentive Plan (the "2010 Plan") | Non-employee stock options
Stock Incentive Plan
Stock-based compensation expense		$ 22,000	$ 7,000	$ 100,000	$ 100,000
Unrecognized compensation expense		$ 100,000		$ 100,000		$ 0
Assumptions used in the valuation model
Risk free interest rate, minimum				1.46%	1.93%
Risk free interest rate, maximum				1.76%	2.31%
Expected volatility, minimum				78.43%	75.34%
Expected volatility, maximum				89.47%	79.89%
Number of Shares
Granted				28,571	14,285
2010 Stock Incentive Plan (the "2010 Plan") | Non-employee stock options | Minimum
Assumptions used in the valuation model
Expected term (in years)				9 years 4 months 24 days	9 years 2 months 12 days
2010 Stock Incentive Plan (the "2010 Plan") | Non-employee stock options | Maximum
Assumptions used in the valuation model
Expected term (in years)				10 years	10 years

Stock Incentive Plan - Performa

Stock Incentive Plan - Performance-based stock options (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Feb. 29, 2016	Dec. 31, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Stock Incentive Plan
Stock-based compensation expense			$ 251	$ 30	$ 521	$ 121
Performance-based stock options | 2010 Stock Incentive Plan (the "2010 Plan") | Consultant
Stock Incentive Plan
Number of options granted		5,714
Stock-based compensation expense							$ 0
Performance-based stock options | 2010 Stock Incentive Plan (the "2010 Plan") | Employee
Stock Incentive Plan
Number of options granted	29,285
Minimum amount of gross proceeds from issuance of shares in an IPO or private placement that triggers vesting of awards	$ 20,000

Net loss Per Share Attributab54

Net loss Per Share Attributable to Common Stockholders - Basic and diluted net loss per common share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator:
Net loss	$ (8,114)	$ (3,932)	$ (17,976)	$ (9,380)
Gain on extinguishment of redeemable convertible preferred shares		1,673		1,673
Net loss attributable to common shareholders	$ (8,114)	$ (2,259)	$ (17,976)	$ (7,707)
Denominator:
Weighted-average common shares used in net loss per share attributable to common stockholders - basic and diluted	570,558	494,302	549,138	486,479
Net loss per share attributable to common stockholders - basic and diluted	$ (14.22)	$ (4.57)	$ (32.73)	$ (15.84)

Net loss Per Share Attributab55

Net loss Per Share Attributable to Common Stockholders - Common stock equivalents excluded from the calculation of net loss due to anti-dilutive effect (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Common Stock equivalents excluded from the calculation of net loss per share due to their anti-dilutive effect
Total	15,942,202	9,883,872	15,942,202	9,883,872
Convertible preferred stock
Common Stock equivalents excluded from the calculation of net loss per share due to their anti-dilutive effect
Total	13,623,933	9,429,302	13,623,933	9,429,302
Common stock warrants
Common Stock equivalents excluded from the calculation of net loss per share due to their anti-dilutive effect
Total	222,775	222,775	222,775	222,775
Outstanding stock options
Common Stock equivalents excluded from the calculation of net loss per share due to their anti-dilutive effect
Total	2,095,494	231,795	2,095,494	231,795

Subsequent Events (Details)

Subsequent Events (Details) $ / shares in Units, $ in Thousands	Nov. 29, 2016USD ($)$ / sharesshares	Oct. 31, 2016USD ($)$ / sharesshares	Oct. 14, 2016shares	Oct. 31, 2016$ / sharesshares	Sep. 30, 2016USD ($)shares	Sep. 30, 2015USD ($)	Dec. 31, 2015shares
Subsequent Events
Common stock reserved under the Plan					16,043,311		11,165,804
Payment of offering expenses | $					$ 22	$ 193
Common Stock
Subsequent Events
Number of shares into which the warrants may be converted					222,775		222,775
2010 Stock Incentive Plan (the "2010 Plan")
Subsequent Events
Common stock reserved under the Plan					2,495,607
Subsequent Events
Subsequent Events
Stock split ratio			0.142857
Subsequent Events | 2016 Stock Award and Incentive Plan (the "2016 Plan") | Common Stock
Subsequent Events
Common stock reserved under the Plan			1,300,000
Increase in number of shares reserved for issuance (shares)			2,000,000
Percentage of common stock outstanding			4.00%
Subsequent Events | 2016 Employee Stock Purchase Plan (the "ESPP") | Common Stock
Subsequent Events
Common stock reserved under the Plan			175,000
Increase in number of shares reserved for issuance (shares)			300,000
Percentage of common stock outstanding			1.00%
Subsequent Events | 2010 Stock Incentive Plan (the "2010 Plan") | Common Stock
Subsequent Events
Common stock reserved under the Plan			101,109
Subsequent Events | IPO | Common Stock
Subsequent Events
New share issues		7,049,230
Share price (in dollars per share) | $ / shares		$ 13		$ 13
Proceeds from initial public offering | $		$ 82,900
Underwriting discounts and commissions | $		6,400
Payment of offering expenses | $		$ 2,300
Shares issued upon conversion		13,623,933
Number of shares into which the warrants may be converted		222,775		222,775
Shares issued from warrants exercised		221,573		221,573
Subsequent Events | Over-Allotment Option | Common Stock
Subsequent Events
New share issues	1,057,385
Share price (in dollars per share) | $ / shares	$ 13
Proceeds from initial public offering | $	$ 12,800