Collaboration Agreements (Tables)

3 Months Ended

Mar. 31, 2015

Fred Hutchinson Cancer Research Center [Member]

Summary of Potential Success Payments, Payable in Cash or Publicly-Traded Equity

The following table summarizes the potential success payments, which are payable in cash or publicly-traded equity at the Company’s discretion:

Multiple of Equity Value at issuance		5.0x		7.5x		10.0x		15.0x		20.0x		25.0x		30.0x		35.0x		40.0x
Per share common stock price required for payment	$	20.00	$	30.00	$	40.00	$	60.00	$	80.00	$	100.00	$	120.00	$	140.00	$	160.00
Success payment(s) (in millions)	$	10	$	25	$	40	$	50	$	50	$	50	$	50	$	50	$	50

Assumptions Used to Calculate Estimated Fair Value of Success Payment Liability

The following variables were incorporated in the calculation of the estimated fair value of the success payment liability as of March 31, 2015:

Assumptions	March 31, 2015		December 31, 2014
Fair value of common stock	$	60.66	$	52.22
Risk free interest rate		1.63%-1.91%		1.94%-2.16%
Expected volatility		75%		75%
Expected term (years)		6.55-9.55		6.79-9.79

Memorial Sloan Kettering Cancer Center [Member]

Summary of Potential Success Payments, Payable in Cash or Publicly-Traded Equity

The following table summarizes the potential success payments, which are payable in cash or publicly-traded equity at the Company’s discretion:

Multiple of Equity Value at issuance		10.0x		15.0x		30.0x
Per share common stock price required for payment	$	40.00	$	60.00	$	120.00
Success payment(s) (in millions)	$	10	$	70	$	70

Assumptions Used to Calculate Estimated Fair Value of Success Payment Liability

 The following variables were incorporated in the calculation of the estimated fair value of the success payment liability as of March 31, 2015:

Assumptions	March 31, 2015		December 31, 2014
Fair value of common stock	$	60.66	$	52.22
Risk free interest rate		1.65%-1.91%		1.95%-2.16%
Expected volatility		75%		75%
Expected term (years)		6.64-9.65		6.89-9.89