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License and Collaboration Agreements - Additional Information (Detail) - USD ($)		1 Months Ended	12 Months Ended
	Sep. 30, 2012	Oct. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Related Party Transaction [Line Items]
Payments under exclusive option license agreement			$ 1,250,000
Share issued under the agreements			59,761
Issuance of common stock related to technology licensing option			$ 750,000	$ 750,000
Research and development expense			2,000,000
Payments under license agreement			4,500,000
Potential milestone payments payable			33,000,000
Contractual obligations due MSK, Amgen and QIMR			0	0
Maximum
Related Party Transaction [Line Items]
Potential milestone payments related to sales			104,000,000
Potential milestone payments upon achievement of milestone			59,000,000
Clinical Services
Related Party Transaction [Line Items]
Payments under license agreement				$ 100,000
Clinical supplies
Related Party Transaction [Line Items]
Payments under license agreement					$ 600,000
Amgen
Related Party Transaction [Line Items]
Payments under license agreement			0
QIMR Berghofer Medical Research Institute
Related Party Transaction [Line Items]
Research and development expense			200,000
License fee		$ 3,000,000
License Agreements \| Amgen
Related Party Transaction [Line Items]
Payments under license agreement	$ 250,000
Potential milestone payments payable			86,000,000
Payment under development and regulatory approval milestones			1,000,000
Sales revenue threshold for maximum milestone payment			1,000,000,000
Percentage of common stock				5.10%
License Agreements \| Amgen \| Milestone For Clinical Trials
Related Party Transaction [Line Items]
Potential milestone payments payable			14,000,000
License Agreements \| Amgen \| Favorable Regulatory Action
Related Party Transaction [Line Items]
Potential milestone payments payable			72,000,000
License Agreements \| Amgen \| Maximum
Related Party Transaction [Line Items]
Potential milestone payments related to sales			206,000,000
License Agreements \| Amgen \| Series A 1 Convertible Preferred Stock
Related Party Transaction [Line Items]
Share issued under the agreements					2,006,688	3,531,774
Estimated fair value of stock upon issuance	$ 2,800,000
License Agreements \| Prior to Recapitalization \| Amgen \| Series A 1 Convertible Preferred Stock
Related Party Transaction [Line Items]
Share issued under the agreements	5,538,462
License Agreements \| After Recapitalization \| Amgen \| Series A 1 Convertible Preferred Stock
Related Party Transaction [Line Items]
Share issued under the agreements	615,384
License Agreement With Amgen
Related Party Transaction [Line Items]
Payments under license agreement			$ 1,500,000	$ 1,200,000	$ 800,000
Milestone payments paid				$ 1,000,000