Following Restructuring Announcement, FDA Slaps Partial Hold on Unum's Phase I Trial

Shares of Unum Therapeutics plunged more than 8% Monday after the company disclosed that the U.S. Food and Drug Administration (FDA) placed a partial clinical hold on its Phase I trial for non-Hodgkin lymphoma due to a safety concern.

In a filing with the U.S. Securities and Exchange Commission, Cambridge, Mass.-based Unum Therapeutics disclosed the FDA’s decision, which was made March 4. The company said the partial clinical hold was placed on its trial assessing the company’s asset ACTR707 in combination with Rituxan (rituximab) in patients with CD20+ B cell non-Hodgkin lymphoma. The partial clinical hold on the trial comes in the wake of the company’s announcement earlier this month that it planned to conclude its clinical program for ACTR707, as it undergoes a restructuring to focus its resources on development of a preclinical asset for solid tumors.

Unum said the hold was issued by the FDA after the company reported that one patient in the trial experienced a Grade 3 serious adverse event that is being evaluated as a possible new malignancy and is considered to be possibly related to ACTR707. Unum said it will work closely with the study leaders and the FDA to understand more about the event.

Patients who previously received ACTR707 can continue to receive rituximab infusions in the study, the company said.

ACTR707 was developed from Unum’s novel proprietary Antibody-Coupled T cell Receptor (ACTR) platform, the company said. ACTR is designed to develop autologous engineered T-cell therapies that combine the cell-killing ability of T cells and the tumor-targeting ability of co-administered antibodies to exert potent antitumor immune responses, according to company data. ACTR707 is also in a Phase I trial in combination with Herceptin (trastuzumab) for the treatment of patients with HER2+ advanced cancers. In January, the company reported that enrollment for that trial was complete and that more than half had received the therapeutic combination.

The partial clinical hold on the lymphoma trial came only days after Unum announced it had implemented a restructuring to prioritize the development of BOXR1030, for the treatment of solid tumor cancers. According to Unum, BOXR1030 expresses a glypican-3 (GPC3) targeted CAR and incorporates the novel transgene glutamic-oxaloacetic transaminase 2 (GOT2) to improve T cell function in the solid tumor microenvironment by enhancing T cell metabolism. Unum announced it had initiated formal preclinical development activities, including preclinical safety testing and GMP process development, to support filing an IND application for BOXR1030 in late 2020.   

As part of this restructuring to focus on BOXR1030, Unum is concluding its clinical trials of ACTR707. In addition to concluding its clinical programs for ACTR707, the company said it plans to reduce its current workforce by 43 employees, approximately 60%, to focus efforts on the BOXR1030 program.