Notes Payable	6 Months Ended
Jun. 30, 2017
Notes Payable [Abstract]
Notes Payable	NOTE 6. NOTES PAYABLE Facility Agreement Pursuant to a Facility Agreement (the “Facility Agreement”) we entered into with entities affiliated with Deerfield Management Company, L.P. (collectively, “Deerfield”) during February 2013, we issued promissory notes in the aggregate principal amount of $20.5 million (the “Notes”). The Notes bear simple interest at a rate of 8.75% per annum, payable quarterly in arrears commencing on April 1, 2013. In connection with the execution of the Facility Agreement, we issued warrants to purchase an aggregate of 5.5 million shares of common stock immediately exercisable at an exercise price per share initially equal to $2.63 (the “Warrants”). During the year ended December 31, 2016, warrants to purchase 5.5 million shares of common stock were net exercised, resulting in the issuance of approximately 4.2 million shares of common stock. The cashless net exercises of the warrants did not result in any additional funds being collected by us. As of December 31, 2016, no warrants remained outstanding. In addition, the Facility Agreement requires us to maintain consolidated cash and cash equivalents on the last day of each calendar quarter of not less than $2.0 million. As security for our repayment of our obligations under the Facility Agreement, we granted to Deerfield a security interest in substantially all of our property. The Facility Agreement has a maximum term of seven years from inception. Subsequent to the date of the Facility Agreement, at the election of the holders of Notes representing a majority of the aggregate principal amount of the outstanding Notes, the Notes holders may elect to receive 25% of the net proceeds from any financing that includes an equity component, including without limitation, the sale or issuance of our common stock, options, warrants or other securities convertible or exchangeable for shares of our common stock, as payment of the Notes. This right is subject to certain exceptions set forth in the Facility Agreement. The Notes holders have the option to require us to repay the Notes if we complete a Major Transaction (as defined in the Facility Agreement), including a change of control or a sale of all or substantially all of our assets. Additionally, the principal balance of the Facility Agreement may become immediately due and payable upon an Event of Default (as defined in the Facility Agreement), in which case the Notes holders would have the right to require us to repay 100% of the principal amount of the loan, plus any accrued and unpaid interest thereon. The Facility Agreement does not provide for a prepayment of the Notes at our option. On June 23, 2017, pursuant to a partial exercise by the Notes holders of their right to elect to receive up to 25% of the net proceeds from any qualified financing that includes an equity component, we paid $4.5 million of outstanding principal, together with accrued and unpaid interest, to one of the Notes holders with proceeds from our underwritten public equity offering (Refer to “Note 8. Stockholders’ Equity” for additional details). Financing Derivative A number of features embedded in the Notes required accounting for as a derivative, including the indemnification of certain withholding taxes and the acceleration of debt upon (i) a qualified financing, (ii) an event of default, (iii) a Major Transaction, and (iv) the exercise of the warrant via offset to debt principal. These features represent a single derivative (the “Financing Derivative”) that was bifurcated from the debt instrument and accounted for as a liability at fair value, with changes in fair value between reporting periods recorded in other income (expense), net. The estimated fair value of the Financing Derivative was determined by comparing the difference between the fair value of the Notes with and without the Financing Derivative by calculating the respective present values from future cash flows using a 9.2% and 10.6% weighted average market yield at June 30, 2017 and December 31, 2016, respectively. The estimated fair value of the Financing Derivative as of June 30, 2017 and December 31, 2015 was $0.0 million and $0.4 million, respectively. Notes We initially recorded the Notes and Warrants at $14.1 million and $6.4 million, respectively, based upon the relative fair value allocation of the $20.5 million of proceeds. The carrying value of the Notes at the inception of the debt was $12.8 million, resulting in an original issue discount of $7.7 million. As of June 30, 2017 and December 31, 2016, we had outstanding $16.0 million and $20.5 million aggregate principal amount of Notes, respectively. As of June 30, 2017 and December 31, 2016, a debt discount of $2.9 million and $4.3 million, respectively, remained to be amortized through February 2020, the maturity of the Notes. As of June 30, 2017, $2.6 million out of the outstanding $16.0 million aggregate principal amount of Notes was reclassified from “Notes payable, non-current” to “Notes payable, current”, as that portion of the principal becomes due by June 30, 2018.

NOTE 6. NOTES PAYABLE

Facility Agreement

Pursuant to a Facility Agreement (the “Facility Agreement”) we entered into with entities affiliated with Deerfield Management Company, L.P. (collectively, “Deerfield”) during February 2013, we issued promissory notes in the aggregate principal amount of $20.5 million (the “Notes”). The Notes bear simple interest at a rate of 8.75% per annum, payable quarterly in arrears commencing on April 1, 2013.

In connection with the execution of the Facility Agreement, we issued warrants to purchase an aggregate of 5.5 million shares of common stock immediately exercisable at an exercise price per share initially equal to $2.63 (the “Warrants”). During the year ended December 31, 2016, warrants to purchase 5.5 million shares of common stock were net exercised, resulting in the issuance of approximately 4.2 million shares of common stock. The cashless net exercises of the warrants did not result in any additional funds being collected by us. As of December 31, 2016, no warrants remained outstanding.

In addition, the Facility Agreement requires us to maintain consolidated cash and cash equivalents on the last day of each calendar quarter of not less than $2.0 million. As security for our repayment of our obligations under the Facility Agreement, we granted to Deerfield a security interest in substantially all of our property.

The Facility Agreement has a maximum term of seven years from inception. Subsequent to the date of the Facility Agreement, at the election of the holders of Notes representing a majority of the aggregate principal amount of the outstanding Notes, the Notes holders may elect to receive 25% of the net proceeds from any financing that includes an equity component, including without limitation, the sale or issuance of our common stock, options, warrants or other securities convertible or exchangeable for shares of our common stock, as payment of the Notes. This right is subject to certain exceptions set forth in the Facility Agreement. The Notes holders have the option to require us to repay the Notes if we complete a Major Transaction (as defined in the Facility Agreement), including a change of control or a sale of all or substantially all of our assets. Additionally, the principal balance of the Facility Agreement may become immediately due and payable upon an Event of Default (as defined in the Facility Agreement), in which case the Notes holders would have the right to require us to repay 100% of the principal amount of the loan, plus any accrued and unpaid interest thereon. The Facility Agreement does not provide for a prepayment of the Notes at our option.

On June 23, 2017, pursuant to a partial exercise by the Notes holders of their right to elect to receive up to 25% of the net proceeds from any qualified financing that includes an equity component, we paid $4.5 million of outstanding principal, together with accrued and unpaid interest, to one of the Notes holders with proceeds from our underwritten public equity offering (Refer to “Note 8. Stockholders’ Equity” for additional details).

Financing Derivative

A number of features embedded in the Notes required accounting for as a derivative, including the indemnification of certain withholding taxes and the acceleration of debt upon (i) a qualified financing, (ii) an event of default, (iii) a Major Transaction, and (iv) the exercise of the warrant via offset to debt principal. These features represent a single derivative (the “Financing Derivative”) that was bifurcated from the debt instrument and accounted for as a liability at fair value, with changes in fair value between reporting periods recorded in other income (expense), net.

The estimated fair value of the Financing Derivative was determined by comparing the difference between the fair value of the Notes with and without the Financing Derivative by calculating the respective present values from future cash flows using a 9.2% and 10.6% weighted average market yield at June 30, 2017 and December 31, 2016, respectively. The estimated fair value of the Financing Derivative as of June 30, 2017 and December 31, 2015 was $0.0 million and $0.4 million, respectively.

Notes

We initially recorded the Notes and Warrants at $14.1 million and $6.4 million, respectively, based upon the relative fair value allocation of the $20.5 million of proceeds. The carrying value of the Notes at the inception of the debt was $12.8 million, resulting in an original issue discount of $7.7 million.

As of June 30, 2017 and December 31, 2016, we had outstanding $16.0 million and $20.5 million aggregate principal amount of Notes, respectively. As of June 30, 2017 and December 31, 2016, a debt discount of $2.9 million and $4.3 million, respectively, remained to be amortized through February 2020, the maturity of the Notes.

As of June 30, 2017, $2.6 million out of the outstanding $16.0 million aggregate principal amount of Notes was reclassified from “Notes payable, non-current” to “Notes payable, current”, as that portion of the principal becomes due by June 30, 2018.