Collaboration and License Agreement (Tables)

12 Months Ended

Dec. 31, 2018

Collaboration And License Agreement Disclosure [Abstract]

Changes in Contract Assets and Liabilities

The following table presents changes in the Company’s contract assets and liabilities, which excludes research and development reimbursements under the cost sharing plan further discussed below, for the years ending December 31, 2018 and 2017 (in thousands):

	Year Ended December 31, 2018
	Balance at Beginning of Period		Additions		Deductions			Balance at End of Period
Contract liabilities:
Deferred revenue	$	33,558	$	—	$	(33,558	)	$	—
	Year Ended December 31, 2017
	Balance at Beginning of Period		Additions		Deductions			Balance at End of Period
Contract assets:
Receivable from collaboration partner	$	45,000	$	—	$	(45,000	)	$	—
Contract liabilities:
Deferred revenue	$	45,000	$	—	$	(11,442	)	$	33,558

Schedule of Research and Development Reimbursement Receivables and Related Prepayments from Collaboration Partner

The following table presents the Sanofi research and development reimbursement receivables and related prepayment activity during the years ended December 31, 2018 and 2017 (in thousands):  

	Year Ended December 31,
	2018			2017
Receivable from collaboration partner
Balance at beginning of year	$	1,013		$	—
Additions		3,994			1,013
Deductions		(5,007	)		—
Balance at end of year	$	-		$	1,013
Prepayment from collaboration partner for mavacamten
Balance at beginning of year	$	4,432		$	—
Additions for advance billings		-			1,013
Payments received from Sanofi		31,659			10,697
Actual expenses incurred		(23,118	)		(7,278	)
Balance at end of year	$	12,973		$	4,432