Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

A reconciliation of the Company’s effective tax rate to the statutory federal income tax rate is as follows:


	Years Ended December 31,
	2023			2022
Federal income tax at statutory federal rate		21.0	%		21.0	%
State taxes		15.7			6.1
Stock-based compensation		18.5			(2.8	)
Tax credits		(32.5	)		(6.5	)
Other		—			(0.1	)
Change in valuation allowance		(23.7	)		(17.9	)
Total		(1.0	)%		(0.2	)%

Temporary differences that give rise to significant net deferred tax assets as of December 31, 2023 and 2022 are as follows:


	December 31,
(in thousands)	2023			2022
Deferred tax assets:
Net operating losses	$	65,194		$	64,135
Capitalized research and development expenses		—			141
Credit carryforwards		167,017			167,397
Deferred compensation		1,177			1,181
Election out of installment method		820			820
Accrued expenses		44			44
Other temporary differences		366			621
Installment sale tax basis		15,869			15,869
Total gross deferred tax assets		250,487			250,208
Valuation allowance		(250,487	)		(250,208	)
Net deferred tax assets	$	—		$	—

The change in the valuation allowance against the deferred tax assets in the years ended December 31, 2023 and 2022 was as follows:


(in thousands)	Balance at Beginning of Period		Additions		Deductions		Balance at End of Period
December 31, 2022	$	249,933	$	275	$	—	$	250,208
December 31, 2023		250,208		279		—		250,487

MERRIMACK PHARMACEUTICALS INC 10-K