Sanofi License and Collaboration Agreement (Tables)

6 Months Ended

Jun. 30, 2019

Collaboration And License Agreement Disclosure [Abstract]

Changes in Contract Liabilities

The following table presents changes in the Company’s contract liabilities, which excludes research and development reimbursements under the cost sharing plan further discussed below, for the six months ended June 30, 2018 (in thousands):

	Six Months Ended June 30, 2018
	Balance at Beginning of Period		Additions		Deductions			Balance at End of Period
Contract liabilities:
Deferred revenue	$	33,558	$	—	$	(11,970	)	$	21,588

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 six months ended June 30, 2019 and 2018 (in thousands):  

	Six Months Ended June 30,
	2019			2018
Receivable from collaboration partner
Balance at beginning of period	$	—		$	1,013
Deductions		—			(1,013	)
Balance at end of period	$	—		$	—
Prepayment from collaboration partner for mavacamten
Balance at beginning of period	$	12,973		$	4,432
Payments received from Sanofi		7,777			11,809
Actual expenses incurred		(18,494	)		(7,126	)
Balance at end of period	$	2,256		$	9,115