Debt	12 Months Ended
Dec. 31, 2016
Debt
Debt	4. Debt Promissory Notes to Related Parties The Company issued promissory notes to related parties (the Promissory Notes) at a compound interest rate of 8% per annum for an aggregate principal amount of $0.3 million on various dates from March 2009 through October 2014 with maturity dates through October 31, 2014. The Promissory Notes along with accrued interest were exchanged for convertible notes (the Convertible Notes) on November 1, 2014, in the amount of $0.4 million inclusive of accrued interest. Convertible Notes The Company completed a series of convertible note financings with certain investors beginning on November 1, 2014 and ending on February 18, 2015 (the Convertible Notes), whereby a total of $2.7 million was loaned to the Company, of which $2.0 million was loaned in 2015. Interest for the Convertible Notes compounded on a daily basis at a rate of 8 percent per annum. The Convertible Notes converted into shares of the Company’s Series A preferred stock upon close of the Series A preferred stock financing on March 31, 2015. The conversion equaled 125% of the unpaid principal plus unpaid accrued interest on the Convertible Notes. At the time of their issuance, the Convertible Notes contained a conversion premium with regard to the conversion into the Series A preferred stock. The Company determined that the redemption feature under the Convertible Notes qualified as an embedded derivative and was separated from its debt host. The bifurcation of the embedded derivative from its debt host resulted in a discount to the Convertible Notes. The discount was amortized to interest expense over the term of the Convertible Notes using the straight‑line method. The embedded derivative was accounted for separately on a fair market value basis. The Company recorded the fair value changes of the premium conversion derivative associated with the Convertible Notes to interest expense that amounted to $0.4 million and $18,000 for the years ended December 31, 2015 and 2014, respectively. As a result of their conversion into shares of Series A preferred stock on March 31, 2015 as described above, there were no Convertible Notes outstanding during 2016. Interim Notes On July 31, 2015, the Company entered into a convertible interim note financing (collectively with the notes issued in December 2015, February 2016 and April 2016, the Interim Notes), pursuant to which certain investors agreed to loan the Company approximately $2.8 million. On August 10, 2016, immediately prior to the closing of the IPO, the Company’s Interim Notes, together with accrued interest thereon, converted into 1,656,807 shares of common stock. The Interim Notes accrued interest at a rate of 8% per annum, compounded annually, and would automatically convert into shares issued to investors in the Company’s next equity financing round that results in gross proceeds of at least $5.0 million (a Qualified Financing). The conversion would be equal to unpaid principal at 115% plus any unpaid accrued interest. The investors would be paid out principal at 200% if a change of control occurred before the next financing round. In the event that a Qualified Financing, change of control, or an IPO did not occur before July 31, 2016, the parties would then negotiate a price for conversion into a new round of stock. In December 2015, the Company amended the Interim Notes and certain investors agreed to loan the Company an additional $2.7 million for a revised financing total of $5.5 million. The Interim Notes continued to accrue interest at an 8% rate per annum compounded annually, but were amended to automatically convert into shares of the same class of the Company’s next convertible preferred stock financing round (the Preferred Stock Financing). The conversion into shares issued in the Preferred Stock Financing would be equal to unpaid principal at 115% plus unpaid accrued interest. In the event that either a change of control occurs or the Company completes a public transaction which results in the Company’s stockholders holding securities listed on a national securities exchange, including an IPO, before the Preferred Stock Financing, the Interim Notes, as amended, would automatically convert into shares of the Company’s common stock at a conversion price of $6.70585 per share (which represents the original issue price of the Series A preferred stock) based on 100% of outstanding principal and unpaid accrued interest. Lastly, if a Preferred Stock Financing, change of control, or public transaction did not occur before December 31, 2016, the parties agreed to then negotiate a conversion price into a new round of stock. In February 2016, certain investors agreed to loan the Company an additional $0.2 million for a revised financing total of $5.6 million. The Interim Notes continued to accrue interest at an 8% rate per annum compounded annually, but were amended to automatically convert into shares of the same class of the Company’s next Preferred Stock Financing. The conversion into shares issued in the Preferred Stock Financing would be equal to unpaid principal at 115% plus unpaid accrued interest. In the event that either a change of control occurs or the Company completes a public transaction which results in the Company’s stockholders holding securities listed on a national securities exchange, including an IPO, before the Preferred Stock Financing, the Interim Notes, as amended, would automatically convert into shares of the Company’s common stock at a conversion price of $6.70585 per share (which represents the original issue price of the Series A preferred stock as adjusted for the Reverse Stock Split (as defined below)) based on 100% of outstanding principal and unpaid accrued interest. Lastly, if a Preferred Stock Financing, change of control, or public transaction did not occur before December 31, 2016, the parties agreed to then negotiate a conversion price into a new round of stock. In April 2016, the Company amended the Interim Notes and certain investors agreed to loan the Company an additional $5.0 million for a revised financing total, including Interim Notes previously issued, of $10.6 million. The Interim Notes continued to accrue interest at an 8% rate per annum compounded annually, but were amended so that 125% of the unpaid principal and accrued interest, would automatically convert into shares of the same class of the Company’s next convertible preferred stock financing round of at least $5.0 million (the Qualified Financing). In the event that either a change of control occurs or the Company completes a public transaction which results in the Company’s stockholders holding securities listed on a national securities exchange, including an IPO, before the Qualified Financing, 100% of outstanding principal and unpaid accrued interest on the Interim Notes, as amended, would automatically convert into shares of the Company’s common stock at a conversion price of $6.70585 per share, as adjusted for the Reverse Stock Split. Lastly, if a Qualified Financing, change of control, or public transaction did not occur, the Interim Notes would become payable on demand anytime after December 31, 2016. The Company incurred issuance costs related to the April 2016 financing in the amount of $10,000. The Interim Notes were discounted for the issuance costs, and the discount was amortized to interest expense over their remaining term using the straight‑line method. On August 10, 2016, immediately prior to the closing of the IPO, the Company’s Interim Notes, together with accrued interest thereon, converted into 1,656,807 shares of common stock. At the time of their issuance, the Interim Notes contained a conversion premium with regard to the conversion into shares at the time of the next Qualified Financing. The Company determined that the redemption feature under the Interim Notes qualified as an embedded derivative and was separated from its debt host. The bifurcation of the embedded derivative from its debt host resulted in a discount to the Interim Notes. The discount was amortized to interest expense over the term of the Interim Notes using the straight‑line method. The embedded derivative was accounted for separately on a fair market value basis. The fair value of the derivative associated with the Interim Notes was $0.3 million at December 31, 2015 and was included as premium conversion derivative on the accompanying balance sheets. As a result of the conversion of the Interim Notes, together with accrued interest thereon, into common stock immediately prior to the closing of the IPO, there was no premium conversion derivative outstanding as of December 31, 2016. The Company recorded the fair value changes of the premium conversion derivative associated with the Interim Notes to interest income (expense) that amounted to $0.2 million, $(0.1) million and zero for the years ended December 31, 2016, 2015 and 2014, respectively. As a result of their conversion to common stock on August 10, 2016 as described above, there were no Interim Notes outstanding as of December 31, 2016.

4. Debt

Promissory Notes to Related Parties

The Company issued promissory notes to related parties (the Promissory Notes) at a compound interest rate of 8% per annum for an aggregate principal amount of $0.3 million on various dates from March 2009 through October 2014 with maturity dates through October 31, 2014. The Promissory Notes along with accrued interest were exchanged for convertible notes (the Convertible Notes) on November 1, 2014, in the amount of $0.4 million inclusive of accrued interest.

Convertible Notes

The Company completed a series of convertible note financings with certain investors beginning on November 1, 2014 and ending on February 18, 2015 (the Convertible Notes), whereby a total of $2.7 million was loaned to the Company, of which $2.0 million was loaned in 2015. Interest for the Convertible Notes compounded on a daily basis at a rate of 8 percent per annum. The Convertible Notes converted into shares of the Company’s Series A preferred stock upon close of the Series A preferred stock financing on March 31, 2015. The conversion equaled 125% of the unpaid principal plus unpaid accrued interest on the Convertible Notes.

At the time of their issuance, the Convertible Notes contained a conversion premium with regard to the conversion into the Series A preferred stock. The Company determined that the redemption feature under the Convertible Notes qualified as an embedded derivative and was separated from its debt host. The bifurcation of the embedded derivative from its debt host resulted in a discount to the Convertible Notes. The discount was amortized to interest expense over the term of the Convertible Notes using the straight‑line method. The embedded derivative was accounted for separately on a fair market value basis. The Company recorded the fair value changes of the premium conversion derivative associated with the Convertible Notes to interest expense that amounted to $0.4 million and $18,000 for the years ended December 31, 2015 and 2014, respectively. As a result of their conversion into shares of Series A preferred stock on March 31, 2015 as described above, there were no Convertible Notes outstanding during 2016.

Interim Notes

On July 31, 2015, the Company entered into a convertible interim note financing (collectively with the notes issued in December 2015, February 2016 and April 2016, the Interim Notes), pursuant to which certain investors agreed to loan the Company approximately $2.8 million. On August 10, 2016, immediately prior to the closing of the IPO, the Company’s Interim Notes, together with accrued interest thereon, converted into 1,656,807 shares of common stock.

The Interim Notes accrued interest at a rate of 8% per annum, compounded annually, and would automatically convert into shares issued to investors in the Company’s next equity financing round that results in gross proceeds of at least $5.0 million (a Qualified Financing). The conversion would be equal to unpaid principal at 115% plus any unpaid accrued interest. The investors would be paid out principal at 200% if a change of control occurred before the next financing round. In the event that a Qualified Financing, change of control, or an IPO did not occur before July 31, 2016, the parties would then negotiate a price for conversion into a new round of stock.

In December 2015, the Company amended the Interim Notes and certain investors agreed to loan the Company an additional $2.7 million for a revised financing total of $5.5 million. The Interim Notes continued to accrue interest at an 8% rate per annum compounded annually, but were amended to automatically convert into shares of the same class of the Company’s next convertible preferred stock financing round (the Preferred Stock Financing). The conversion into shares issued in the Preferred Stock Financing would be equal to unpaid principal at 115% plus unpaid accrued interest. In the event that either a change of control occurs or the Company completes a public transaction which results in the Company’s stockholders holding securities listed on a national securities exchange, including an IPO, before the Preferred Stock Financing, the Interim Notes, as amended, would automatically convert into shares of the Company’s common stock at a conversion price of $6.70585 per share (which represents the original issue price of the Series A preferred stock) based on 100% of outstanding principal and unpaid accrued interest. Lastly, if a Preferred Stock Financing, change of control, or public transaction did not occur before December 31, 2016, the parties agreed to then negotiate a conversion price into a new round of stock.

In February 2016, certain investors agreed to loan the Company an additional $0.2 million for a revised financing total of $5.6 million. The Interim Notes continued to accrue interest at an 8% rate per annum compounded annually, but were amended to automatically convert into shares of the same class of the Company’s next Preferred Stock Financing. The conversion into shares issued in the Preferred Stock Financing would be equal to unpaid principal at 115% plus unpaid accrued interest. In the event that either a change of control occurs or the Company completes a public transaction which results in the Company’s stockholders holding securities listed on a national securities exchange, including an IPO, before the Preferred Stock Financing, the Interim Notes, as amended, would automatically convert into shares of the Company’s common stock at a conversion price of $6.70585 per share (which represents the original issue price of the Series A preferred stock as adjusted for the Reverse Stock Split (as defined below)) based on 100% of outstanding principal and unpaid accrued interest. Lastly, if a Preferred Stock Financing, change of control, or public transaction did not occur before December 31, 2016, the parties agreed to then negotiate a conversion price into a new round of stock.

In April 2016, the Company amended the Interim Notes and certain investors agreed to loan the Company an additional $5.0 million for a revised financing total, including Interim Notes previously issued, of $10.6 million. The Interim Notes continued to accrue interest at an 8% rate per annum compounded annually, but were amended so that 125% of the unpaid principal and accrued interest, would automatically convert into shares of the same class of the Company’s next convertible preferred stock financing round of at least $5.0 million (the Qualified Financing). In the event that either a change of control occurs or the Company completes a public transaction which results in the Company’s stockholders holding securities listed on a national securities exchange, including an IPO, before the Qualified Financing, 100% of outstanding principal and unpaid accrued interest on the Interim Notes, as amended, would automatically convert into shares of the Company’s common stock at a conversion price of $6.70585 per share, as adjusted for the Reverse Stock Split. Lastly, if a Qualified Financing, change of control, or public transaction did not occur, the Interim Notes would become payable on demand anytime after December 31, 2016. The Company incurred issuance costs related to the April 2016 financing in the amount of $10,000. The Interim Notes were discounted for the issuance costs, and the discount was amortized to interest expense over their remaining term using the straight‑line method.

On August 10, 2016, immediately prior to the closing of the IPO, the Company’s Interim Notes, together with accrued interest thereon, converted into 1,656,807 shares of common stock. At the time of their issuance, the Interim Notes contained a conversion premium with regard to the conversion into shares at the time of the next Qualified Financing. The Company determined that the redemption feature under the Interim Notes qualified as an embedded derivative and was separated from its debt host. The bifurcation of the embedded derivative from its debt host resulted in a discount to the Interim Notes. The discount was amortized to interest expense over the term of the Interim Notes using the straight‑line method. The embedded derivative was accounted for separately on a fair market value basis. The fair value of the derivative associated with the Interim Notes was $0.3 million at December 31, 2015 and was included as premium conversion derivative on the accompanying balance sheets. As a result of the conversion of the Interim Notes, together with accrued interest thereon, into common stock immediately prior to the closing of the IPO, there was no premium conversion derivative outstanding as of December 31, 2016. The Company recorded the fair value changes of the premium conversion derivative associated with the Interim Notes to interest income (expense) that amounted to $0.2 million, $(0.1) million and zero for the years ended December 31, 2016, 2015 and 2014, respectively.

As a result of their conversion to common stock on August 10, 2016 as described above, there were no Interim Notes outstanding as of December 31, 2016.