Note Payable	6 Months Ended
Jun. 30, 2013
Note Payable
Note Payable	5. Note Payable On March 21, 2011, the Company executed a debt financing agreement whereby the Company had access to borrow up to $15,000,000 of senior loan financing through January 1, 2012. On December 30, 2011, the Company amended its credit facility to provide for an extension of its drawdown period through December 1, 2012, provided that it had drawn down at least $5,000,000 as of August 1, 2012. On July 23, 2012, the Company obtained an additional 60 day extension to the initial drawdown date from August 1, 2012 to October 1, 2012. For each draw, the Company shall make six months of interest only payments at a fixed rate of 11.5% followed by 30 months of interest and principal payments at a fixed rate of 8.5% and a final payment of 6% of the amount drawn. The debt is secured by all the Company’s assets, except for the Company’s intellectual property, which is subject to a negative pledge agreement. Upon entry into the agreement, the Company issued warrants to purchase 34,000 shares of Series C redeemable convertible preferred stock (“Series C Preferred”) at an exercise price of $13.3530. The estimated fair value of the warrants at issuance of approximately $345,000 was recorded as a deferred financing cost offsetting the note payable liability and is being amortized to interest expense over the expected term of the loan. Upon extension of the credit facility in December 2011, the Company issued a warrant to purchase up to an additional 86,000 shares of its Series D redeemable convertible preferred stock (“Series D Preferred”) at an exercise price of $13.9040. The estimated fair value of the warrant at issuance of approximately $1,074,000 was recorded as a deferred financing cost offsetting the note payable liability and is being amortized to interest expense over the expected term of the loan. As of June 30, 2013 and December 31, 2012, $15,000,000 and $5,000,000 respectively had been drawn. There is no further borrowing capacity under this facility as of June 30, 2013. Effective immediately prior to the closing of the Company’s IPO, the warrants for convertible preferred stock became warrants for common stock and were reclassified to stockholders’ equity. Prior to the IPO, the Company had classified the warrants as a liability and re-measured the liability to estimated fair value using the Black-Scholes option pricing model. Assumptions used to revalue the Series C Preferred warrants at June 30, 2012 were as follows: contractual life according to the remaining terms of the warrants, no dividend yield, risk-free interest rate of 1.43% and volatility of 76%. Assumptions used to revalue the Series D Preferred warrants at June 30, 2012 were as follows: contractual life according to the remaining terms of the warrants, no dividend yield, risk-free interest rate of 1.58% and volatility of 77%. The increase in the fair value of the Series C Preferred warrants from issuance in March 2011 through the IPO in October of 2012, totaled $55,000 and was recorded in warrant and other income (expense), net, in the statement of operations and comprehensive loss, and included expense of $105,000 and $97,000 for the three and six months ended June 30, 2012. The decrease in value of the Series D Preferred warrants from issuance in December 2011 through the IPO in October of 2012 totaled $18,000 and was recorded in warrant and other income (expense), net, in the statement of operations and comprehensive loss, including expense of $5,000 and income of $2,000 for the three and six months ended June 30, 2012. All warrants were exercised on a cashless basis in December of 2012 resulting in the net issuance of 49,000 shares of common stock and no warrants are outstanding as of June 30, 2013. Included in interest expense for the three and six months ended June 30, 2013 and 2012 was amortization of debt issuance costs of $85,000, $170,000, $52,000 and $104,000, respectively, and interest expense of $469,000 and $779,000 related to the note payable for the three and six months ended June 30, 2013. No interest expense was recorded for the three and six months ended June 30, 2012 as no amounts had yet been drawn under the credit facility. The balance of accrued interest expense at June 30, 2013 was $120,000. The remaining unamortized debt issuance cost at June 30, 2013 was $906,000.

5. Note Payable

On March 21, 2011, the Company executed a debt financing agreement whereby the Company had access to borrow up to $15,000,000 of senior loan financing through January 1, 2012. On December 30, 2011, the Company amended its credit facility to provide for an extension of its drawdown period through December 1, 2012, provided that it had drawn down at least $5,000,000 as of August 1, 2012. On July 23, 2012, the Company obtained an additional 60 day extension to the initial drawdown date from August 1, 2012 to October 1, 2012. For each draw, the Company shall make six months of interest only payments at a fixed rate of 11.5% followed by 30 months of interest and principal payments at a fixed rate of 8.5% and a final payment of 6% of the amount drawn. The debt is secured by all the Company’s assets, except for the Company’s intellectual property, which is subject to a negative pledge agreement.

Upon entry into the agreement, the Company issued warrants to purchase 34,000 shares of Series C redeemable convertible preferred stock (“Series C Preferred”) at an exercise price of $13.3530. The estimated fair value of the warrants at issuance of approximately $345,000 was recorded as a deferred financing cost offsetting the note payable liability and is being amortized to interest expense over the expected term of the loan.

Upon extension of the credit facility in December 2011, the Company issued a warrant to purchase up to an additional 86,000 shares of its Series D redeemable convertible preferred stock (“Series D Preferred”) at an exercise price of $13.9040. The estimated fair value of the warrant at issuance of approximately $1,074,000 was recorded as a deferred financing cost offsetting the note payable liability and is being amortized to interest expense over the expected term of the loan. As of June 30, 2013 and December 31, 2012, $15,000,000 and $5,000,000 respectively had been drawn. There is no further borrowing capacity under this facility as of June 30, 2013.

Effective immediately prior to the closing of the Company’s IPO, the warrants for convertible preferred stock became warrants for common stock and were reclassified to stockholders’ equity. Prior to the IPO, the Company had classified the warrants as a liability and re-measured the liability to estimated fair value using the Black-Scholes option pricing model. Assumptions used to revalue the Series C Preferred warrants at June 30, 2012 were as follows: contractual life according to the remaining terms of the warrants, no dividend yield, risk-free interest rate of 1.43% and volatility of 76%. Assumptions used to revalue the Series D Preferred warrants at June 30, 2012 were as follows: contractual life according to the remaining terms of the warrants, no dividend yield, risk-free interest rate of 1.58% and volatility of 77%.

The increase in the fair value of the Series C Preferred warrants from issuance in March 2011 through the IPO in October of 2012, totaled $55,000 and was recorded in warrant and other income (expense), net, in the statement of operations and comprehensive loss, and included expense of $105,000 and $97,000 for the three and six months ended June 30, 2012. The decrease in value of the Series D Preferred warrants from issuance in December 2011 through the IPO in October of 2012 totaled $18,000 and was recorded in warrant and other income (expense), net, in the statement of operations and comprehensive loss, including expense of $5,000 and income of $2,000 for the three and six months ended June 30, 2012.

All warrants were exercised on a cashless basis in December of 2012 resulting in the net issuance of 49,000 shares of common stock and no warrants are outstanding as of June 30, 2013.

Included in interest expense for the three and six months ended June 30, 2013 and 2012 was amortization of debt issuance costs of $85,000, $170,000, $52,000 and $104,000, respectively, and interest expense of $469,000 and $779,000 related to the note payable for the three and six months ended June 30, 2013. No interest expense was recorded for the three and six months ended June 30, 2012 as no amounts had yet been drawn under the credit facility. The balance of accrued interest expense at June 30, 2013 was $120,000. The remaining unamortized debt issuance cost at June 30, 2013 was $906,000.