Note 9 — Net Loss Per Share Attributable to Common Stockholders

The following table (in thousands, except for loss per share) reconciles basic and diluted weighted average common shares outstanding for the years ended December 31, 2018 and 2017:


	Year ended
	December 31,
	2018		2017
Weighted average common shares outstanding:
Basic		106,564		100,926
Dilutive unvested stock, convertible preferred stock, Common Stock Warrants and IPO Warrants		—		—
Diluted		106,564		100,926

Basic and diluted net loss per share attributable to common stockholders	$	(0.41)	$	(0.35)

Potentially dilutive securities that were not included in the diluted net loss per share computations because their effect would have been anti-dilutive were as follows (in thousands):


	Year ended
	December 31,
	2018		2017
Unvested stock (1)		498		258
Convertible preferred stock		3,552		—
Common Stock Warrants		454		—
IPO Warrants(2)		12,082		12,082
Total potentially dilutive common shares		16,586		12,340

⁽¹⁾

Does not include 10.8 million shares and 25.7 million shares of unvested stock for the year ended December 31, 2018 and 2017 because the performance conditions had not yet been satisfied as of December 31, 2018 and 2017, respectively.

⁽²⁾

The IPO Warrants are exercisable at a price of $11.50 per share and expire July 24, 2022. The Company may redeem the Warrants at a price of $0.01 per IPO Warrant upon 30 days’ notice only if the last sale price of our common stock is at least $17.50 per share for any 20 trading days within a 30-trading day period. If the Company redeems the IPO Warrants in this manner, the Company will have the option to do so on a cashless basis with the issuance of an economically equivalent number of shares of Company common stock.