Subsequent Events	3 Months Ended
Mar. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	13. Subsequent Events On April 4, 2019, the Company announced that it is discontinuing development of its sole clinical stage program, MM-310, its antibody-directed nanotherapeutic for the treatment of solid tumors. This decision was the result of a comprehensive review of available safety data from its Phase 1 clinical trial of MM-310. Based on emerging data since the amendment of the clinical protocol in late 2018, the Company concluded that the trial would not be able to reach an optimal therapeutic index for MM-310. On April 4, 2019, the Company also announced that it expects to initiate a workforce reduction as it closes out clinical activities, reflective of its narrowed preclinical pipeline and in line with prior cost-cutting measures. On April 30, 2019 the Company announced that it committed to a course of action to implement a reduction in headcount, after which the Company expects to have approximately 13 employees. The reduction in headcount is primarily focused on the Company’s clinical organization as a result of the discontinuation of development of MM-310. The Company estimates it will incur expenses for one-time termination benefits in connection with this corporate restructuring of approximately $1.5 million to $1.7 million for employee severance, benefits and related costs, all of which are expected to result in cash expenditures, inclusive of Sergio L. Santillana, the Chief Medical Officer of the Company, who provided notice of his resignation effective as of April 12, 2019. The reduction in headcount is expected to be substantially completed by May 31, 2019 and fully completed by July 2019. On April 15, 2019, the Company prepaid in full all principal, accrued and unpaid interest, fees, costs and expenses under the Loan Agreement with Hercules in an aggregate amount equal to $16.0 million (the “Payoff Amount”). The Company had previously borrowed $15.0 million under the Loan Agreement. The Payoff Amount includes a prepayment penalty of $0.2 million. In connection with the payment of the Payoff Amount, all liens and security interests granted to secure the obligations under the Loan Agreement and all guaranties of the obligations under the Loan Agreement terminated. On May 7, 2019, the Company sold its equity position in Silver Creek for $7.8 million. In May 2019, the Company auctioned laboratory equipment from the Company’s research and development operations, resulting in approximately $1.3 million in cash.

Subsequent Events

3 Months Ended

Mar. 31, 2019

13. Subsequent Events

On April 4, 2019, the Company announced that it is discontinuing development of its sole clinical stage program, MM-310, its antibody-directed nanotherapeutic for the treatment of solid tumors. This decision was the result of a comprehensive review of available safety data from its Phase 1 clinical trial of MM-310. Based on emerging data since the amendment of the clinical protocol in late 2018, the Company concluded that the trial would not be able to reach an optimal therapeutic index for MM-310.

On April 4, 2019, the Company also announced that it expects to initiate a workforce reduction as it closes out clinical activities, reflective of its narrowed preclinical pipeline and in line with prior cost-cutting measures. On April 30, 2019 the Company announced that it committed to a course of action to implement a reduction in headcount, after which the Company expects to have approximately 13 employees. The reduction in headcount is primarily focused on the Company’s clinical organization as a result of the discontinuation of development of MM-310. The Company estimates it will incur expenses for one-time termination benefits in connection with this corporate restructuring of approximately $1.5 million to $1.7 million for employee severance, benefits and related costs, all of which are expected to result in cash expenditures, inclusive of Sergio L. Santillana, the Chief Medical Officer of the Company, who provided notice of his resignation effective as of April 12, 2019. The reduction in headcount is expected to be substantially completed by May 31, 2019 and fully completed by July 2019.

On April 15, 2019, the Company prepaid in full all principal, accrued and unpaid interest, fees, costs and expenses under the Loan Agreement with Hercules in an aggregate amount equal to $16.0 million (the “Payoff Amount”). The Company had previously borrowed $15.0 million under the Loan Agreement. The Payoff Amount includes a prepayment penalty of $0.2 million. In connection with the payment of the Payoff Amount, all liens and security interests granted to secure the obligations under the Loan Agreement and all guaranties of the obligations under the Loan Agreement terminated.

On May 7, 2019, the Company sold its equity position in Silver Creek for $7.8 million.

In May 2019, the Company auctioned laboratory equipment from the Company’s research and development operations, resulting in approximately $1.3 million in cash.