Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2019

Reconciliation of Cash, Cash Equivalents and Restricted Cash

The following table provides a reconciliation of cash, cash equivalents and restricted cash to amounts shown in the condensed consolidated statements of cash flows:

	September 30,
	2019		2018
	(in thousands)
Cash and cash equivalents	$	77,559	$	36,038
Restricted cash		1,274		1,790
Total cash, cash equivalents and restricted cash	$	78,833	$	37,828

ASC 606

Impact of Adoption of ASC 606 on Previously Reported Amounts of Financial Statement

As part of the adoption, the Company reviewed its collaboration and license agreement with Novartis to determine the cumulative effect impact related to the adoption of ASC 606. (For a complete discussion of the accounting for the Company’s agreement with Novartis, see Note 10.) The adoption of ASC 606 resulted in a change to the pattern of revenue recognition whereby the Company expects to recognize revenue from its collaboration agreement with Novartis as costs are incurred, which likely will not occur evenly over the performance period as a result of applying the cost-to-cost method, in contrast to recognizing revenue on a straight-line basis over the estimated performance period under ASC 605. The impact on previously reported amounts as a result of the adoption of ASC 606 is as follows:

Condensed Consolidated Balance Sheets
	December 31, 2018
	(in thousands)
	As revised under ASC 606			As originally reported under ASC 605			Effect of change
Current portion of deferred revenue	$	770		$	3,684		$	(2,914	)
Long-term portion of deferred revenue	$	30,750		$	29,474		$	1,276
Accumulated deficit	$	(95,758	)	$	(97,396	)	$	1,638

Condensed Consolidated Statements of Operations and Comprehensive Loss
	Three Months Ended September 30, 2018
	(in thousands, except per share amounts)
	As revised under ASC 606			As originally reported under ASC 605			Effect of change
Collaboration revenue	$	1,602		$	954		$	648
Loss from operations	$	(15,635	)	$	(16,283	)	$	648
Net loss	$	(14,148	)	$	(14,796	)	$	648
Net loss per share attributable to common    stockholders-basic and diluted	$	(0.38	)	$	(0.40	)	$	0.02
	Nine Months Ended September 30, 2018
	(in thousands, except per share amounts)
	As revised under ASC 606			As originally reported under ASC 605			Effect of change
Collaboration revenue	$	4,126		$	2,704		$	1,422
Loss from operations	$	(39,754	)	$	(41,176	)	$	1,422
Net loss	$	(36,791	)	$	(38,213	)	$	1,422
Net loss per share attributable to common    stockholders-basic and diluted	$	(1.42	)	$	(1.48	)	$	0.06
	For the Year Ended December 31, 2018
	(in thousands, except per share amounts)
	As revised under ASC 606			As originally reported under ASC 605			Effect of change
Collaboration revenue	$	5,322		$	3,684		$	1,638
Loss from operations	$	(59,926	)	$	(61,564	)	$	1,638
Net loss	$	(55,577	)	$	(57,215	)	$	1,638
Net loss per share attributable to common    stockholders-basic and diluted	$	(1.95	)	$	(2.00	)	$	0.05

Condensed Consolidated Statement of Cash Flows
	Nine Months Ended September 30, 2018
	(in thousands)
	As revised under ASC 606			As originally reported under ASC 605			Effect of change
Net loss	$	(36,791	)	$	(38,213	)	$	1,422
Adjustments to reconcile net loss to net cash used in operating activities:
Deferred revenue	$	(1,484	)	$	(62	)	$	(1,422	)
Cash, cash equivalents and restricted cash, beginning of period	$	53,347		$	53,347		$	—
Cash, cash equivalents and restricted cash, end of period	$	37,828		$	37,828		$	—
	For the Year Ended December 31, 2018
	(in thousands)
	As revised under ASC 606			As originally reported under ASC 605			Effect of change
Net loss	$	(55,577	)	$	(57,215	)	$	1,638
Adjustments to reconcile net loss to net cash used in operating activities:
Deferred revenue	$	(1,890	)	$	(252	)	$	(1,638	)
Cash, cash equivalents and restricted cash, beginning of period	$	53,347		$	53,347		$	—
Cash, cash equivalents and restricted cash, end of period	$	39,992		$	39,992		$	—