Targeted myeloma treatment shows promise in Phase 1 trial

More than 40% of patients in a Phase 1 clinical trial of myeloma treatment cevostamab responded to the drug, meaning their cancer burden was reduced. The treatment also demonstrated a manageable safety profile.

The trial enrolled people with myeloma that was relapsed or refractory, meaning it had failed to respond or had come back following previous lines of myeloma treatment.

Results from the study were published in Nature Medicine in a paper titled, “FcRH5×CD3 bispecific antibody cevostamab in relapsed or refractory multiple myeloma: a phase 1 trial.” The work was funded by Roche subsidiary Genentech, which is developing cevostamab.

“Fixed-duration cevostamab has manageable safety and induces durable remissions in patients with late-line disease,” the researchers wrote. “These data support the continued development of cevostamab alone or in combination with standard of care or investigational agents.”

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Bispecific antibody therapy targets new protein

Myeloma is a type of blood cancer marked by the uncontrolled growth of certain cells in the bone marrow. Cevostamab is designed to simultaneously stick to two targets: FcRH5, a protein expressed by all myeloma cells, and CD3, which is expressed by cancer-killing immune cells. By targeting both at once, the therapy aims to trigger the immune system to attack cancer more effectively.

This type of two-pronged therapy is known as a bispecific antibody. While several medications in this class are approved in the U.S. to treat certain myeloma patients, cevostamab is the first that targets FcRH5.

“In myeloma, there’s always a need to reach for the next treatment, so having another validated target will give us more options, particularly for patients who might have already tried our currently approved [bispecific antibody] therapies,” Adam Cohen, MD, co-author of the study and director of myeloma immunotherapy at the University of Pennsylvania, said in a university news story. “These results have opened the door to new studies investigating a fixed-duration approach for other bispecific antibodies as well.”

The Phase 1 clinical trial (NCT03275103) enrolled 324 people with relapsed/refractory myeloma, most of whom had received six or more lines of therapy. All participants were treated with cevostamab, administered via infusion into the bloodstream every three weeks. A range of doses was tested; the trial’s main goals were to assess cevostamab’s safety and determine the optimal dose for further testing.

Safety data showed that cevostamab had a safety profile consistent with what’s typical for potent anticancer therapies. Most patients had serious side effects, the most common of which were low blood cell counts, anemia, and infections. Three participants died due to severe side effects related to cevostamab.

Based on the safety data, the researchers identified 160 mg as the target dose for future testing. There appeared to be a greater risk of serious infection at higher doses, though fatal side effects were still reported at this dose. Among the 167 patients who received the 160 mg dose, the objective response rate was 44.3%. In other words, nearly half of the patients experienced a reduction in cancer burden following cevostamab treatment. More than one in four patients had a response judged as very good or better.

The researchers said these response rates are compelling given that the trial participants had received many prior lines of therapy without success, though they stressed that further studies are needed to confirm cevostamab’s safety and efficacy.

“These data validate FcRH5 as a therapeutic target for myeloma and show that fixed-duration cevostamab has manageable safety and induces durable remissions in patients with late-line disease,” the researchers wrote.