Subsequent Events	3 Months Ended
Mar. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	10. Subsequent Events On May 2, 2019, the Company and its wholly-owned subsidiary GB001, Inc., as borrower, entered into a credit, guaranty and security agreement (the “Credit Facility”) agented by MidCap Financial Trust (“MidCap”) and the additional lenders party thereto from time to time (together with MidCap, the “Lenders”), pursuant to which the Lenders, including affiliates of MidCap and Silicon Valley Bank, agreed to make term loans available to the Company for working capital and general business purposes, in a principal amount of up to $150.0 million in term loan commitments, including a $30.0 million term loan which was funded at the closing date, with the ability to access the remaining $120.0 million in three additional tranches (of $40.0 million, $30.0 million and $50.0 million, respectively), subject to specified availability periods, the achievement of certain clinical development milestones, minimum cash requirements and other customary conditions. The Credit Facility is secured by substantially all of the Company’s and its domestic subsidiaries’ personal property, including intellectual property, and includes affirmative and negative covenants applicable to the Company. Each term loan under the Credit Facility bears interest at an annual rate equal to the sum of (i) one-month LIBOR (customarily defined, with a change to prime rate if LIBOR funding becomes unlawful or impractical) plus (ii) 6.15%, subject to a LIBOR floor of 2.00%. The Company is required to make interest-only payments on the term loan for all payment dates prior to June 1, 2021. The term loans under the Credit Facility will begin amortizing on June 1, 2021, with equal monthly payments of principal plus interest being made by the Company to the Lenders in consecutive monthly installments following such interest-only period for 36 months or, for any funding of the fourth tranche occurring after June 1, 2021, the number of months until the Credit Facility matures on May 1, 2024. Upon final repayment of the term loans, the Company must pay an exit fee of 1.75% of the amount borrowed under the Credit Facility, less any partial exit fees previously paid. Upon partial prepayment of a portion of the term loans, the Company must pay a partial exit fee of 1.75% of the principal being prepaid. At the Company’s option, the Company may prepay the outstanding principal balance of the term loan in whole or in part, subject to a prepayment fee of 3.0% of any amount prepaid if the prepayment occurs through and including the first anniversary of the closing date, 2.0% of the amount prepaid if the prepayment occurs after the first anniversary of the closing date through and including the second anniversary of the closing date, and 1.0% of any amount prepaid after the second anniversary of the closing date and prior to May 1, 2024.

Subsequent Events

3 Months Ended

Mar. 31, 2019

10. Subsequent Events

On May 2, 2019, the Company and its wholly-owned subsidiary GB001, Inc., as borrower, entered into a credit, guaranty and security agreement (the “Credit Facility”) agented by MidCap Financial Trust (“MidCap”) and the additional lenders party thereto from time to time (together with MidCap, the “Lenders”), pursuant to which the Lenders, including affiliates of MidCap and Silicon Valley Bank, agreed to make term loans available to the Company for working capital and general business purposes, in a principal amount of up to $150.0 million in term loan commitments, including a $30.0 million term loan which was funded at the closing date, with the ability to access the remaining $120.0 million in three additional tranches (of $40.0 million, $30.0 million and $50.0 million, respectively), subject to specified availability periods, the achievement of certain clinical development milestones, minimum cash requirements and other customary conditions. The Credit Facility is secured by substantially all of the Company’s and its domestic subsidiaries’ personal property, including intellectual property, and includes affirmative and negative covenants applicable to the Company.

Each term loan under the Credit Facility bears interest at an annual rate equal to the sum of (i) one-month LIBOR (customarily defined, with a change to prime rate if LIBOR funding becomes unlawful or impractical) plus (ii) 6.15%, subject to a LIBOR floor of 2.00%. The Company is required to make interest-only payments on the term loan for all payment dates prior to June 1, 2021. The term loans under the Credit Facility will begin amortizing on June 1, 2021, with equal monthly payments of principal plus interest being made by the Company to the Lenders in consecutive monthly installments following such interest-only period for 36 months or, for any funding of the fourth tranche occurring after June 1, 2021, the number of months until the Credit Facility matures on May 1, 2024. Upon final repayment of the term loans, the Company must pay an exit fee of 1.75% of the amount borrowed under the Credit Facility, less any partial exit fees previously paid. Upon partial prepayment of a portion of the term loans, the Company must pay a partial exit fee of 1.75% of the principal being prepaid. At the Company’s option, the Company may prepay the outstanding principal balance of the term loan in whole or in part, subject to a prepayment fee of 3.0% of any amount prepaid if the prepayment occurs through and including the first anniversary of the closing date, 2.0% of the amount prepaid if the prepayment occurs after the first anniversary of the closing date through and including the second anniversary of the closing date, and 1.0% of any amount prepaid after the second anniversary of the closing date and prior to May 1, 2024.