Notes Payable	12 Months Ended
Dec. 31, 2016
Debt Disclosure [Abstract]
Notes Payable	9. Notes Payable In December 2016, we entered into a supplemental funding support agreement with BMS and Pfizer whereby we received $50.0 million in exchange for two promissory notes totaling $65.0 million that become due in December 2024. The use of funds is restricted to development activities needed for regulatory approval of andexant alfa by the FDA and EMA as provided for in the agreement. Pursuant to the terms of the agreement, we are required to pay down the note each quarter in an amount equal to 5% of net sales of andexanet alfa in the USA and the EU. Should the initial regulatory approval of andexanet alfa in the USA and EU not be achieved by January 1, 2019, one hundred percent of payments due to us under the Japan License agreement and fifty percent of all other andexanet alfa license fees and milestone payments received from third party collaborators will be applied to the notes payable. In addition, if the approval of andexanet alfa in the USA and EU is not achieved by January 1, 2019, we are able to reduce the repayment amount to $60.0 million if such amount is paid by December 31, 2021 and regardless of the timing of regulatory approval, we may reduce the repayment amount to $62.5 million if such amount is paid by December 31, 2023. Any unpaid amounts shall become immediately due upon: 1) our change of control; 2) event of default; and 3) termination for breach. We have the right to prepay the repayment amount at any time without any penalty. The accounting for such funding agreement requires us to make certain estimates and assumptions, including timing of andexanet alfa approval, timing of royalty payments due to BMS and Pfizer, the expected rate of return to BMS and Pfizer, the split between current and long-term portions of the obligation and accretion of related interest expense. The upfront cash receipt of $50.0 million is recorded as notes payable, long term at issuance. The Company is accruing for interest over the term of the related note at issuance. The carrying value of the notes payable at December 31, 2016, including accrued interest of $60,000, is $49.8 million. We evaluated the features of the notes payable and determined that certain features require acceleration of payments such as pursuant to a change of control or an event of default, as well as the terms that adjust the total amount of interest required to be paid based upon the timing of initial regulatory approval in the U.S. and EU require bifurcation and fair value recognition. We determined the fair value of each derivative using a Monte Carlo simulation model taking into account the probability of these events occurring and potential repayment amounts and timing of such payments that would result under various scenarios (see Note 3). The aggregate fair value of the embedded derivatives was $246,000 at issuance and was included in long-term notes payable as of December 31, 2016. The estimated fair value of the Notes payable at December 31, 2016 was $54.9 million and the fair value was measured using Level 3 inputs. The estimated fair market value was calculated using a Monte Carlo simulation model with inputs consistent with those used in determining the embedded derivative values as described in Note 3.

9. Notes Payable

In December 2016, we entered into a supplemental funding support agreement with BMS and Pfizer whereby we received $50.0 million in exchange for two promissory notes totaling $65.0 million that become due in December 2024. The use of funds is restricted to development activities needed for regulatory approval of andexant alfa by the FDA and EMA as provided for in the agreement.

Pursuant to the terms of the agreement, we are required to pay down the note each quarter in an amount equal to 5% of net sales of andexanet alfa in the USA and the EU. Should the initial regulatory approval of andexanet alfa in the USA and EU not be achieved by January 1, 2019, one hundred percent of payments due to us under the Japan License agreement and fifty percent of all other andexanet alfa license fees and milestone payments received from third party collaborators will be applied to the notes payable. In addition, if the approval of andexanet alfa in the USA and EU is not achieved by January 1, 2019, we are able to reduce the repayment amount to $60.0 million if such amount is paid by December 31, 2021 and regardless of the timing of regulatory approval, we may reduce the repayment amount to $62.5 million if such amount is paid by December 31, 2023. Any unpaid amounts shall become immediately due upon: 1) our change of control; 2) event of default; and 3) termination for breach. We have the right to prepay the repayment amount at any time without any penalty.

The accounting for such funding agreement requires us to make certain estimates and assumptions, including timing of andexanet alfa approval, timing of royalty payments due to BMS and Pfizer, the expected rate of return to BMS and Pfizer, the split between current and long-term portions of the obligation and accretion of related interest expense.

The upfront cash receipt of $50.0 million is recorded as notes payable, long term at issuance. The Company is accruing for interest over the term of the related note at issuance. The carrying value of the notes payable at December 31, 2016, including accrued interest of $60,000, is $49.8 million.

We evaluated the features of the notes payable and determined that certain features require acceleration of payments such as pursuant to a change of control or an event of default, as well as the terms that adjust the total amount of interest required to be paid based upon the timing of initial regulatory approval in the U.S. and EU require bifurcation and fair value recognition. We determined the fair value of each derivative using a Monte Carlo simulation model taking into account the probability of these events occurring and potential repayment amounts and timing of such payments that would result under various scenarios (see Note 3). The aggregate fair value of the embedded derivatives was $246,000 at issuance and was included in long-term notes payable as of December 31, 2016.

The estimated fair value of the Notes payable at December 31, 2016 was $54.9 million and the fair value was measured using Level 3 inputs. The estimated fair market value was calculated using a Monte Carlo simulation model with inputs consistent with those used in determining the embedded derivative values as described in Note 3.