Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2019

Summary of Potential Common Shares Excluded from Calculation of Diluted Net Loss per Share

The following potential common shares, presented based on amounts outstanding at each period end, were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:

	Three and Nine Months Ended September 30,
	2019		2018
Stock options to purchase common stock		8,258,031		7,444,040
Unvested restricted stock units		145,900		289,908
Shares issuable under ESPP		13,171		44
Total common stock equivalents		8,417,102		7,733,992

Summary of Impact on Condensed Consolidated Balance Sheets for Opening Balances Related to Lease

The impact to the Condensed Consolidated Balance Sheets for the opening balances is as follows (in thousands):

	December 31, 2018		Impact of adoption of ASC 842			January 1, 2019
Operating lease assets	$	—	$	13,737		$	13,737
Accrued expenses and other current liabilities		15,207		(1,768	)		13,439
Operating lease liabilities		—		4,285			4,285
Lease incentive obligation, net of current portion		6,776		(6,776	)		—
Deferred rent		2,216		(2,216	)		—
Operating lease liabilities, net of current portion		—		20,212			20,212