Secured Promissory Note Payable to Oxford Finance	3 Months Ended
Mar. 31, 2018
Secured Promissory Note Payable [Abstract]
Secured Promissory Note Payable [Text Block]	NOTE 9. Secured Promissory Note Payable to Oxford Finance On December 22, 2016, the Company entered into a loan and security agreement (the “Loan Agreement”) with Oxford Finance, under which the Company borrowed $5.0 million. The $5.0 million loan, which bears interest at 30-day U.S. LIBOR plus 6.17%, is evidenced by a secured promissory note and is repayable over four years, with interest only payable over the first 12 months and the balance fully amortized over the subsequent 36 months. The loan is secured by substantially all the Company’s assets, except for intellectual property. In conjunction with the execution of the Loan Agreement, all the holders of convertible promissory notes signed subordination agreements, under which they agreed to subordinate in favor of Oxford Finance all amounts due under their promissory notes and any security interest in the Company’s property. In addition, the holders of the notes agreed that they would not demand or receive any payment until all amounts owed to Oxford Finance under the Loan Agreement have been fully paid in cash. Upon repayment, an additional final payment equal to $325,000 is due, which is being accreted as interest expense over the term of the loan using the effective interest method. In connection with the Loan Agreement, the Company issued a warrant to Oxford Finance to purchase 7,563 shares of its Series C convertible preferred stock at an exercise price of $33.11 per share (the “Warrant”). The fair value of the Warrant at the date of issuance was approximately $134,000, which was recorded as debt discount and is being amortized as interest expense over the term of the loan using the effective‑interest method. The annual effective interest rate of the note, including the accretion of the final payment and the amortization of the debt discount, is approximately 10.5%. The Company recorded interest expense related to the Loan Agreement of $130,000, of which $95,000 was paid, during the three months ended March 31, 2018, and $126,000, of which $57,000 was paid, during the three months ended March 31, 2017. The Warrant provided that if the share price at the next equity financing was less than the Warrant exercise price, then the Warrant would be for the new class of shares, the exercise price would be the new class share price, and the number of shares would be calculated by dividing $250,000 by the new class share price. Due to this anti-dilution protection, the Company determined that the Warrant needed to be recorded as a liability, and therefore estimated the fair value of the Warrant upon issuance and at each balance sheet date, with any changes in the fair value being recorded within the gain (loss) on revaluation of financial instruments line in the statements of operations and comprehensive income (loss). Due to the antidilution protection, following the Merger, the Warrant was amended to allow the holder to purchase 10,914 shares of common stock at an exercise price of $22.99 per share. Since the amended Warrant contains no non-standard antidilution protections or similar features, the fair value of approximately $70,000 on February 13, 2018, was transferred to equity.

NOTE 9. Secured Promissory Note Payable to Oxford Finance

On December 22, 2016, the Company entered into a loan and security agreement (the “Loan Agreement”) with Oxford Finance, under which the Company borrowed $5.0 million. The $5.0 million loan, which bears interest at 30-day U.S. LIBOR plus 6.17%, is evidenced by a secured promissory note and is repayable over four years, with interest only payable over the first 12 months and the balance fully amortized over the subsequent 36 months. The loan is secured by substantially all the Company’s assets, except for intellectual property.

In conjunction with the execution of the Loan Agreement, all the holders of convertible promissory notes signed subordination agreements, under which they agreed to subordinate in favor of Oxford Finance all amounts due under their promissory notes and any security interest in the Company’s property. In addition, the holders of the notes agreed that they would not demand or receive any payment until all amounts owed to Oxford Finance under the Loan Agreement have been fully paid in cash. Upon repayment, an additional final payment equal to $325,000 is due, which is being accreted as interest expense over the term of the loan using the effective interest method.

In connection with the Loan Agreement, the Company issued a warrant to Oxford Finance to purchase 7,563 shares of its Series C convertible preferred stock at an exercise price of $33.11 per share (the “Warrant”). The fair value of the Warrant at the date of issuance was approximately $134,000, which was recorded as debt discount and is being amortized as interest expense over the term of the loan using the effective‑interest method. The annual effective interest rate of the note, including the accretion of the final payment and the amortization of the debt discount, is approximately 10.5%. The Company recorded interest expense related to the Loan Agreement of $130,000, of which $95,000 was paid, during the three months ended March 31, 2018, and $126,000, of which $57,000 was paid, during the three months ended March 31, 2017.

The Warrant provided that if the share price at the next equity financing was less than the Warrant exercise price, then the Warrant would be for the new class of shares, the exercise price would be the new class share price, and the number of shares would be calculated by dividing $250,000 by the new class share price. Due to this anti-dilution protection, the Company determined that the Warrant needed to be recorded as a liability, and therefore estimated the fair value of the Warrant upon issuance and at each balance sheet date, with any changes in the fair value being recorded within the gain (loss) on revaluation of financial instruments line in the statements of operations and comprehensive income (loss).

Due to the antidilution protection, following the Merger, the Warrant was amended to allow the holder to purchase 10,914 shares of common stock at an exercise price of $22.99 per share. Since the amended Warrant contains no non-standard antidilution protections or similar features, the fair value of approximately $70,000 on February 13, 2018, was transferred to equity.