11. Net Loss Per Share

Basic and diluted net loss per share for the years ended December 31, 2020 and 2019 was calculated as follows:



	Year Ended December 31,
	2020		2019
Numerator:
Net loss	$	(27,514)	$	(32,900)
Dividend attributable to down round feature of warrants		(303)		(359)
Dividend attributable to Series A & B convertible preferred stock		(372)		—
Series A & B convertible preferred stock - beneficial conversion feature		(9,399)		—
Net loss attributable to common stockholders for basic and diluted loss per share	$	(37,588)	$	(33,259)
Denominator:
Weighted average number of common shares outstanding - basic and diluted		59,327,713		22,582,687
Net loss per share attributable to common stockholders - basic and diluted	$	(0.63)	$	(1.47)

Included within weighted average common shares outstanding are 16,718,418 common shares issuable upon the exercise of the pre-funded warrants and penny warrants, as the warrants are exercisable at any time for nominal consideration, and as such, the shares are considered outstanding for the purpose of calculating basic and diluted net loss per share attributable to common stockholders.

The Company's potentially dilutive securities include RSUs, stock options and warrants. These securities were excluded from the computations of diluted net loss per share for the years ended December 31, 2020 and 2019, as the effect would be to reduce the net loss per share. The following table includes the potential common shares of common stock, presented based on amounts outstanding at each period end, that were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:


	Year Ended December 31,
	2020	2019
Restricted stock units to purchase common stock	753,106	90,500
Options to purchase common stock	6,393,853	4,024,566
Warrants to purchase common stock	35,986,317	10,369,752
	43,133,276	14,484,818