Nearly a month after Merck paused enrollment in three clinical trials in multiple myeloma to gather more information about patient deaths, the FDA has now put a stop to those studies altogether.
Merck (NYSE: MRK) said Wednesday that the FDA has placed a complete hold on two Phase 3 trials testing its immunotherapy drug pembrolizumab (Keytruda). A third trial, a Phase 1 study, was placed on partial hold, which means that only part of the clinical work has been suspended. Merck said the FDA decided to place holds on the studies after a review of the data found that more patients died in the groups that received the company’s drug as a treatment for multiple myeloma, a cancer of the blood, compared to the control group.
Pembrolizumab is part of a class of drugs called checkpoint inhibitors, which work by blocking a protein that cancers use to evade detection by the immune system. The Merck drug has already notched FDA approvals as a treatment for skin, lung, and kidney cancers, as well as one form of Hodgkin lymphoma. In May, the company received an additional approval for pembrolizumab as a treatment for the most common form of lung cancer.
But checkpoint inhibitors have not yet been approved to treat multiple myeloma, a blood cancer in which the plasma cells grow rapidly, crowding out healthy red and white blood cells. The American Cancer Society estimates that 30,000 people will be diagnosed with multiple myeloma this year. Following lymphoma and leukemia, multiple myeloma is the third most common blood cancer.
Merck had been testing its drug in combination with two established treatments for the disease, pomalidomide (Pomalyst) and dexamethasone. The company did not give any detail about the nature of the patient deaths in the multiple myeloma trials. But in earlier studies of pembrolizumab in other cancers, the company noted that some patients developed immune-mediated pneumonitis, a type of lung infection. In some cases, the infection was fatal. This side effect has been observed in patients given other checkpoint inhibitors as well.
Merck said that the FDA determined that the available data indicate that the risks patients face taking the drug outweigh any potential benefit. Patients in the trials who received the Merck drug along with the older multiple myeloma drugs will stop receiving that combination treatment.
Merck says the clinical holds in multiple myeloma do not affect the company’s other clinical trials testing the drug.