	March 31,			December 31,
	2021			2020
	(in thousands)
Computer hardware and software	$	1,302		$	2,758
Furniture and equipment		964			1,865
Leasehold improvements		6,559			9,220
		8,825			13,843
Less: Accumulated depreciation		(4,652	)		(7,088	)
	$	4,173		$	6,755

Depreciation expense for the three months ended March 31, 2021 and 2020 was $2.6 million and $0.7 million, respectively.

During the three months ended March 31, 2021, the Company removed property and equipment that was fully-depreciated from the condensed consolidated balance sheet, resulting in a decrease of $1.8 million to the gross balance of property and equipment and accumulated depreciation.

During the three months ended March 31, 2021, the Company wrote off property and equipment related to a multi-tenant building under an operating lease for office space in Cambridge, Massachusetts, in connection with the early termination of the lease by the Company. The gross balance of property and equipment and accumulated depreciation decreased by $3.3 million. Of the gross balance, $2.1 million was depreciated immediately upon termination of the lease, and $1.2 million had been depreciated prior to the termination of the lease.

The useful life for computer hardware and software is three years, furniture and equipment is five years and leasehold improvements is the lesser of the useful life or the term of the respective lease.

	March 31,		December 31,
	2021		2020
	(in thousands)
Accrued research and development costs	$	39,276	$	34,398
Employee-related		3,640		14,769
Professional services		7,817		5,184
Other		687		500
	$	51,420	$	54,851