Conference Coverage

B-cell maturation antigen targeted in myeloma trials



– Three novel treatment strategies that target B-cell maturation antigen (BCMA) have shown promise in recent multiple myeloma clinical trials, according to Shaji K. Kumar, MD, of the Mayo Clinic Cancer Center in Rochester, Minn.

Multiple myeloma Courtesy Wikimedia Commons/KGH/Creative Commons License

These strategies include B-cell maturation antigen (BCMA)–specific chimeric antigen receptor (CAR) T-cell therapies, bispecific T-cell engagers (BiTEs), and a BCMA antibody–drug conjugate, Dr. Kumar said at the annual congress on Hematologic Malignancies held by the National Comprehensive Cancer Network.

“Clearly, there are a lot of exciting drugs that are currently in clinical trials, but these three platforms appear to be much more advanced than the others, and hopefully we will see that in the clinic in the near future,” Dr. Kumar said.

The antibody-drug conjugate, GSK2857916, is a humanized IgG1 anti-BCMA antibody conjugated to a microtubule-disrupting agent that has produced an overall response rate in 67% in a group of myeloma patients who had previously received multiple standard-of-care agents.

“Some of the responses were quite durable, lasting several months,” he said.

Now, GSK2857916 is being evaluated in a variety of different combinations, including in a phase 2 study of the antibody-drug conjugate in combination with lenalidomide plus dexamethasone, or bortezomib plus dexamethasone, in patients with relapsed or refractory disease.

Some of the most “exciting” data with anti-BCMA CAR T-cell therapy in myeloma involves bb2121, which showed durable clinical responses in heavily pretreated patients, according to data presented at the 2017 annual meeting of the American Society of Hematology.

“The overall response rate is quite significant,” said Dr. Kumar, who related a 94% rate of overall response that was even higher in patients treated with doses of 150 x 106 CAR+ T cells or more. Many of the response were lasting, he said, with five patients in ongoing response for more than 1 year.

“The results are exciting enough that this is actually moving forward with registration trials,” Dr. Kumar said.

Additionally, promising results have been presented on a novel CAR T-cell product, LCAR-B38M, which principally targets BCMA and led to a significant number of patients who achieved stringent complete response that lasted beyond 1 year.

Multiple BCMA-targeting CAR T-cell products that use different vectors and costimulatory molecules are currently undergoing clinical trials, Dr. Kumar said.

In contrast to CAR T-cell products that must be customized to each patient in a process that takes weeks, BiTEs are a ready-made approach to allow T cells to engage with tumor cells.

“In patients with advanced disease, a lot can change in that short time frame, so having an approach that is off the shelf, which is not patient specific, is quite attractive,” Dr. Kumar said.

BCMA-directed BiTE therapies under investigation include AMG 420 and PF-06863135, he added.

Dr. Kumar reported one disclosure related to Dr. Reddy’s Laboratories.

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