Long-term Debt	3 Months Ended
Mar. 31, 2017
Debt Disclosure [Abstract]
Long-term Debt	8. Long-term Debt Note 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 European Medicines Agency (“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 United States and European Union(“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 United States 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) a change of control of our company; 2) an 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. We are accruing for interest over the term of the related note. The carrying values of the notes payable at March 31, 2017 and December 31, 2016, including accrued interest of $0.7 million and $0.1 million, are $50.5 million and $49.8 million, respectively. We evaluated the features of the notes payable and determined that certain features which 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 United States 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, as further described in Note 3 to the condensed consolidated financial statements. The aggregate fair value of the embedded derivatives at issuance date was $0.3 million included in other long-term liabilities. The Company will remeasure the embedded derivatives to fair value each reporting period until the repayment, termination or maturity of the long-term note payable. For the three months ended March 31, 2017, the remeasurement gain(loss) of embedded derivatives was insignificant. The estimated fair value of the note payable at March 31, 2017 was $54.7 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. Royalty-based Financing In February 2017, we entered into a purchase and sale agreement (the “Royalty Sales Agreement”) with HealthCare Royalty Partners and its affiliates. (“HCR”) whereby HCR acquired a royalty interest in future worldwide net sales of andexanet alfa. We received $50.0 million upon closing and have the right to receive an additional $100.0 million if U.S. regulatory approval of andexanet alfa is received prior to October 2018. We are required to pay HCR a royalty of 2.0% based on tiered net worldwide sales of andexanet alfa. If the additional $100.0 million is received from HCR, the tiered royalty rate will increase to a range of 7.85% to 3.58%, as the applicable rate decreases starting at worldwide net sales levels above $150 million. Total royalty payments are capped at 195% of the funded amount, however, the royalty rates are subject to increase if the timing of marketing and manufacturing approvals from the FDA is not received before the dates within 2018 specified in the Royalty Sales Agreement. If andexanet alfa is not approved for commercial sale the Company has no repayment obligations under this agreement. We have evaluated the terms of the Royalty Sales Agreement and concluded that the features of the funded amount are similar to those of a debt instrument. Accordingly, we have accounted for the transaction as long-term debt. As the repayment of the funded amount is contingent upon the sales volumes of andexanet alfa, the repayment term may be shortened or extended depending on the actual sales of andexanet alfa. The repayment period is commencing from the first commercial sale of andexanet alfa in any country and expiring on the date when HCR has received cash payments totaling an aggregate of 195% of the funded amounts. We evaluated the terms of the debt and determined that certain features, such as the increase in the repayment amount up to $125.0 million upon a change of control and the variability in the royalty payments based upon the timing of initial regulatory approval in the United States and EU, are embedded derivatives that require bifurcation from the debt instrument 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, as further described in Note 3 to these condensed consolidated financial statements. The aggregate fair value of the embedded derivatives at issuance date was $0.6 million and is included in other long-term liabilities. The Company will remeasure the embedded derivatives to fair value each reporting period until the time the features lapse and/or termination of the Royalty Sales Agreement. The effective interest rate as of March 31, 2017 was 13.8%. For the three months ended March 31, 2017, accrued interest in the amount of $0.9 million was added to the principal balance of the debt. In connection with the Royalty Sales Agreement, we paid HCR a fee of $2.0 million and incurred additional debt issuance costs totaling $0.6 million, which includes expenses that we paid on behalf of HCR and expenses incurred directly by us. Debt issuance costs have been netted against the debt as of March 31, 2017 and are being amortized over the estimated term of the debt using the effective interest method. For the three months ended March 31, 2017, we recognized interest expense, including amortization of the debt discount, related to the debt of $0.9 million. The assumptions used in determining the expected repayment term of the debt and amortization period of the issuance costs requires that we make estimates that could impact the short and long-term classification of these costs, as well as the period over which these costs will be amortized. The carrying value of the debt as of March 31, 2017 was $47.8 million, inclusive of payment-in-kind interest expense of $0.9 million and net of unamortized debt discount of $2.5 million. The estimated fair value of long-term debt at March 31, 2017 was $43.3 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.

8. Long-term Debt

Note 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 European Medicines Agency (“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 United States and European Union(“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 United States 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) a change of control of our company; 2) an 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. We are accruing for interest over the term of the related note. The carrying values of the notes payable at March 31, 2017 and December 31, 2016, including accrued interest of $0.7 million and $0.1 million, are $50.5 million and $49.8 million, respectively.

We evaluated the features of the notes payable and determined that certain features which 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 United States 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, as further described in Note 3 to the condensed consolidated financial statements. The aggregate fair value of the embedded derivatives at issuance date was $0.3 million included in other long-term liabilities. The Company will remeasure the embedded derivatives to fair value each reporting period until the repayment, termination or maturity of the long-term note payable. For the three months ended March 31, 2017, the remeasurement gain(loss) of embedded derivatives was insignificant.

The estimated fair value of the note payable at March 31, 2017 was $54.7 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.

Royalty-based Financing

In February 2017, we entered into a purchase and sale agreement (the “Royalty Sales Agreement”) with HealthCare Royalty Partners and its affiliates. (“HCR”) whereby HCR acquired a royalty interest in future worldwide net sales of andexanet alfa. We received $50.0 million upon closing and have the right to receive an additional $100.0 million if U.S. regulatory approval of andexanet alfa is received prior to October 2018.

We are required to pay HCR a royalty of 2.0% based on tiered net worldwide sales of andexanet alfa. If the additional $100.0 million is received from HCR, the tiered royalty rate will increase to a range of 7.85% to 3.58%, as the applicable rate decreases starting at worldwide net sales levels above $150 million. Total royalty payments are capped at 195% of the funded amount, however, the royalty rates are subject to increase if the timing of marketing and manufacturing approvals from the FDA is not received before the dates within 2018 specified in the Royalty Sales Agreement. If andexanet alfa is not approved for commercial sale the Company has no repayment obligations under this agreement. We have evaluated the terms of the Royalty Sales Agreement and concluded that the features of the funded amount are similar to those of a debt instrument. Accordingly, we have accounted for the transaction as long-term debt.

As the repayment of the funded amount is contingent upon the sales volumes of andexanet alfa, the repayment term may be shortened or extended depending on the actual sales of andexanet alfa. The repayment period is commencing from the first commercial sale of andexanet alfa in any country and expiring on the date when HCR has received cash payments totaling an aggregate of 195% of the funded amounts.

We evaluated the terms of the debt and determined that certain features, such as the increase in the repayment amount up to $125.0 million upon a change of control and the variability in the royalty payments based upon the timing of initial regulatory approval in the United States and EU, are embedded derivatives that require bifurcation from the debt instrument 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, as further described in Note 3 to these condensed consolidated financial statements. The aggregate fair value of the embedded derivatives at issuance date was $0.6 million and is included in other long-term liabilities. The Company will remeasure the embedded derivatives to fair value each reporting period until the time the features lapse and/or termination of the Royalty Sales Agreement.

The effective interest rate as of March 31, 2017 was 13.8%. For the three months ended March 31, 2017, accrued interest in the amount of $0.9 million was added to the principal balance of the debt.

In connection with the Royalty Sales Agreement, we paid HCR a fee of $2.0 million and incurred additional debt issuance costs totaling $0.6 million, which includes expenses that we paid on behalf of HCR and expenses incurred directly by us. Debt issuance costs have been netted against the debt as of March 31, 2017 and are being amortized over the estimated term of the debt using the effective interest method. For the three months ended March 31, 2017, we recognized interest expense, including amortization of the debt discount, related to the debt of $0.9 million. The assumptions used in determining the expected repayment term of the debt and amortization period of the issuance costs requires that we make estimates that could impact the short and long-term classification of these costs, as well as the period over which these costs will be amortized. The carrying value of the debt as of March 31, 2017 was $47.8 million, inclusive of payment-in-kind interest expense of $0.9 million and net of unamortized debt discount of $2.5 million.

The estimated fair value of long-term debt at March 31, 2017 was $43.3 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.