(14) Basic and Diluted Net Loss per Share

Basic net loss per common share is computed by dividing net loss by the weighted-average number of shares of common stock outstanding during the period. Diluted net income per share is computed by dividing net income for the period by the weighted average number of common shares outstanding and common equivalent shares from dilutive stock options, employee stock purchases, restricted stock awards, restricted stock units and shares issuable upon a potential conversion of the convertible senior notes using the treasury stock method. In loss periods, the earnings per share calculation excludes common equivalents shares because their inclusion would be antidilutive.

The following common equivalent shares were excluded from the diluted net loss per share calculation because their inclusion would have been anti-dilutive:

	Year Ended December 31,
	2017		2016		2015
Stock options		2,440,290		1,884,425		1,821,722
Shares to be issued under ESPP		44,320		83,790		—
Restricted stock units		784,000		—		—
Convertible senior notes		3,411,199		—		—
Series A-1 preferred stock warrants		—		—		130,384
Convertible preferred stock		—		—		8,354,963
Total		6,679,809		1,968,215		10,307,069

The Company is required to reserve and keep available from the Company’s authorized but unissued shares of common stock a number of shares equal to the number of shares subject to outstanding awards under the 2008 Plan and the number of shares reserved for issuance under each of the 2016 Plan and 2016 ESPP.

In connection with the issuance of the convertible senior notes in November 2017, the Company paid $12.9 million to enter into capped call option agreements to reduce the potential dilution to holders of the Company’s common stock upon conversion of the convertible senior notes. The capped call option agreements are excluded from the calculation of diluted net loss per share attributable to common stockholders as their effect is antidilutive.

Reserve for Unissued Shares of Common Stock

The Company is required to reserve and keep available out of its authorized but unissued shares of common stock such number of shares sufficient for the exercise of all shares granted and available for grant under the Company’s 2008 Plan, 2016 Plan and 2016 ESPP.

The amount of such shares of the Company’s common stock reserved for these purposes at December 31, 2017 is as follows:

	Number of Shares
Stock options issued and outstanding		2,440,290
Additional shares available for grant under equity plans		1,554,177
Total		3,994,467