Preferred Stock Warrants and Common Stock Warrants (Tables)

6 Months Ended

Jun. 30, 2018

Table Text Blocks

Summary of valuation assumptions used in determining fair value of common and preferred stock warrants

Issuance Date	Underlying Security	Exercise Price	Number of Shares Issuable Upon Exercise	Warrant Contractual Term	Classification
July1, 2012	Common stock	$ 0.002	485,985(1)	(1)	Liability
August22, 2013	SeriesD preferred stock	$ 2.9891	167,500	10years	Liability
June27, 2014	SeriesD preferred stock	$ 2.9891	167,500	9.2years	Liability
July31, 2014	Common stock	$ 3.02	106,250	10years	Equity

(1)The number of shares of common stock issuable upon the exercise of the Company’s liability‑classified warrant to purchase common stock is calculated based on the number of shares of common stock equal to 12.5% of the sum of (a)the number of shares of common stock into which the outstanding shares of SeriesA preferred stock, including shares issuable upon the exercise of outstanding options to purchase shares of SeriesA preferred stock, convert upon an IPO and (b)the number of shares of common stock underlying the warrant. Such warrant is only exercisable upon the closing of an IPO of shares of the Company’s common stock. The warrant will expire, if not exercised, on the day immediately following the closing of an IPO of shares of the Company’s common stock.