Basic net loss per share is computed by dividing net loss attributable to common stockholders by the weighted average number of common shares outstanding during each period. The Redeemable Series A-1 Preferred Stock, which was outstanding prior to its redemption on July 27, 2020, and the Convertible and Redeemable Series A-2 Preferred Stock are considered a participating security during the applicable period. Net losses are not allocated to the Redeemable Series A-1 Preferred stockholders nor the Convertible and Redeemable Series A-2 stockholders, as they were not contractually obligated to share in the Company’s losses.

Diluted net loss per share is computed by dividing net loss attributable to common stockholders by the weighted average number of common and dilutive common equivalent shares outstanding for the period using the treasury-stock method or the as-converted method. During the three months ended March 31, 2020, shares issuable in connection with the warrant options (Note 11) were considered outstanding common shares for purposes of calculating net loss per share since they did not contain any conditions that must be satisfied for the holder to exercise the warrant. Potentially dilutive shares are comprised of restricted stock and shares of common stock underlying stock options outstanding under the Plans and warrants (other than warrant options) to purchase common stock. During the three months ended March 31, 2021 and March 31, 2020, there is no difference in the number of shares used to calculate basic and diluted shares outstanding due to the Company’s net loss and potentially dilutive shares being anti-dilutive.

The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company:

	Three Months Ended March 31,
(In thousands, except for net loss per share)	2021			2020
Net loss	$	(11,596	)	$	(41,248	)
Accretion of redeemable series A-1 preferred stock		—			(5,415	)
Convertible and redeemable series A-2 preferred stock dividend		(4,100	)		—
Net loss attributable to common stockholders – basic and diluted		(15,696	)		(46,663	)
Weighted-average common shares outstanding – basic and diluted		25,117			8,904
Net loss per share attributable to common stockholders – basic and diluted	$	(0.62	)	$	(5.24	)

The following equity shares were excluded from the calculation of diluted net loss per share attributable to common stockholders because their effect would have been anti-dilutive:

	March 31,
	2021		2020
Stock options		3,293,679		2,095,909
Restricted stock		26,201		19,059
Warrants		—		116,350