Net Loss per Share

12 Months Ended

Dec. 31, 2017

15. Net Loss per Share

Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted average number of common shares outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted average number of common shares and potentially dilutive securities outstanding for the period determined using the treasury stock and if converted methods. Contingently issuable shares are included in the calculation of basic loss per share as of the beginning of the period in which all the necessary conditions have been satisfied. Contingently issuable shares are included in diluted loss per share based on the number of shares, if any, that would be issuable under the terms of the arrangement if the end of the reporting period was the end of the contingency period, if the results are dilutive.

For purposes of the diluted net loss per share calculation, stock options are considered to be common stock equivalents, but they were excluded from the Company’s calculation of diluted net loss per share allocable to common stockholders because their inclusion would have been anti-dilutive. Therefore, basic and diluted net loss per share applicable to common stockholders was the same for all periods presented.

Upon the closings of the March Offering and the December Offering, the Company sold 4,600,000 and 2,265,500 shares of common stock, respectively. The issuance of these shares resulted in a significant increase in the Company’s weighted-average shares outstanding for the year ended December 31, 2017 when compared to the comparable prior year period and is expected to continue to impact the year-over-year comparability of the Company’s net loss per share calculations for the next three and twelve months.

The following common stock equivalents were excluded from the calculation of diluted net loss per share allocable to common stockholders because their inclusion would have been anti-dilutive:


	As of December 31,
	2017	2016
Unvested restricted common stock	513,225	822,638
Outstanding stock options	4,372,126	3,411,783
Estimated number of shares issuable for convertible notes (1)	244,896	—
Total	5,130,247	4,234,421

(1)

Represents the number of shares that would have been issued if the Company had elected to pay the December Success Payment Notes, as discussed in Note 8, in shares of the Company’s common stock, based on the closing price of the common stock on December 31, 2017. The number of shares issued, for purposes of this presentation, is calculated by dividing the principal of the notes payable, including accrued interest, by the stock price per share.

The table above reflects restricted stock issued upon exercise of unvested stock options as exercised on the dates that the shares are no longer subject to repurchase.