Unum Therapeutics Looks to File IPO, Reveals Patient Deaths in Early Clinical Trial

After a flurry of c-suite and board appointments, Unum Therapeutics is looking to take the company public. In its IPO announcement last week Unum revealed early data from its Phase I non-Hodgkin lymphoma therapy that included toxicity concerns at higher dosing levels.

Cambridge, Mass.-based Unum, which evolved from the LabCentral incubator program in Kendall Square, is developing antibody-coupled T-cell receptor technology. Its lead product ACTR087 in combination with Genentech’s Rituxan (rituximab) is being developed to treat adult patients with relapsed or refractory non-Hodgkin lymphoma.

In its filing with the U.S. Securities and Exchange Commission Unum shared some positive data from a small cohort of patients at a lower dose. Of six dosed patients the company two complete responses and one partial response were observed, the company said in its filing. However, patients who received a higher dose experienced some safety concerns. Unum said two of the nine patients who received the higher dose died from serious adverse events. Additionally, Unum said an additional patient died following an ACTR087-related severe CRS (cytokine release syndrome).

Unum is certainly not the first company working in CAR-T to experience patient deaths. Juno Therapeutics was forced to pull the plug on a promising CAR-T treatment following the deaths of five patients who suffered from cerebral edemas.

The deaths forced the U.S. Food and Drug Administration to place a clinical hold on the trial. The hold was removed in February after the FDA reviewed additional trial data, the company said in its filing. Unum noted that if it continued to "observe severe side effects in our clinical trials" then the FDA could halt or slap another clinical hold on the trial due to safety risks.

In addition to ACTR087 Unum has two additional products in the clinic. The company has initiated a Phase I trial for ACTR707, a modified ACTR construct, which will be used in combination with Rituxan to treat adult patients with relapsed or refractory non-Hodgkin lymphoma. Additionally, the company has a Phase I trial testing ACTR087 in combination with Seattle Genetics novel antibody SEA-BCMA in adult patients with relapsed or refractory multiple myeloma. Unum and Seattle Genetics forged an agreement to develop and commercialize ACTR therapies for cancer in 2015. The Phase I trial is the first product candidate from that collaboration, the company said in its filing.

Unum’s ACTR technology is part of the ever-growing immuno-oncology field. Its ACTR product candidates take T cells from patients and then genetically modify them to express the ACTR protein. ACTR is a chimeric protein which combines parts of proteins found on both T cells and natural killer cells to create a doubly-powerful attack on cancer cells. The modified cells are then re-administered to the patients with a tumor-specific antibody.

"When an ACTR T cell encounters a tumor cell bound with antibodies, it binds to those antibodies and kills the tumor cell through a process known as antibody-dependent cellular cytotoxicity (ADCC), a function not normally observed with T cells. No special modification of the tumor-specific antibody is required in order for ADCC to take place," the company said in its filing.

Unum said its platform can be directed against a wide range of cancer targets through the co-administration of antigen-specific antibodies.

Unum intends to list shares of its common stock on the Nasdaq Exchange under the ticker symbol UNUM.

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