The Food and Drug Administration placed two clinical trials of a bispecific monoclonal antibody under development for several solid tumor indications on hold due to concerns about liver toxicity.
Rockville, Maryland-based MacroGenics said Friday that it had received a letter Thursday from the FDA, which placed a partial hold on two studies of MGD009, a bispecific antibody developed under its DART platform that targets B7-H3 and CD3 in several solid tumor indications. One study, a Phase I trial, studies the drug as a monotherapy, while another studies it in combination with the company’s PD-1 inhibitor, MGA012. The partial clinical hold means no new patients can be enrolled, though current participants may continue to receive the drug at their pre-assigned dose.
On the Nasdaq, shares of MacroGenics, which closed Friday at $16.41, fell more than 25 percent in after-hours trading following the news.
The company said the hold was due to the company reporting liver toxicity events in the monotherapy trial to the agency, including reversible elevations in transaminases with or without concurrent elevations in bilirubin. Although the company said the events were of short duration and otherwise uncomplicated, it also told the FDA it would amend the trials to mitigate the liver toxicities with additional supportive care. In response, the FDA imposed the hold, pending review of additional details and the planned amendments.
“MacroGenics’ top concern in conducting clinical trials is the safety of study participants,” CEO Scott Koenig said in a statement. However, the partial hold does not affect studies of its other B7-H3-targeting drugs, enoblituzumab and MGC018, he said.
Bispecific antibodies work by targeting cancer cell-specific antigens and also antigens on the surfaces of T cells, thereby enabling T cell-mediated killing of cancer cells. The only currently marketed bispecific antibody is Amgen’s Blincyto (blinatumomab), a CD19- and CD3-targeting antibody developed under the company’s BiTE platform for acute lymphoblastic leukemia.
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