Novel Injectable Drug Shows Promise in Relapsed/Refractory Myeloma

Higher doses of PF-06863135 (elranatamab), a novel drug being evaluated for the treatment of multiple myeloma, showed promising results in patients with relapsed/refractory disease, according to early study findings.

“We recently reported on the intravenous dosing of (PF-06863135) and demonstrated evidence of anti-myeloma activity in heavily pretreated relapsed/refractory multiple myeloma. We now extend these findings and report the results of subcutaneous (PF-06863135),” said Dr. Nizar J. Bahlis, of the Arnie Charbonneau Cancer Institute at the University of Calgary, while presenting the data at the 2021 American Society of Clinical Oncology (ASCO) Annual Meeting.

“The primary objective was to assess the safety (and) tolerability of (PF-06863135) administered and determine recommended phase 2 doses. The secondary objectives include the evaluation of anti-myeloma activity, as well as the duration of response,” he added.

Weekly subcutaneous injections of the study drug were tested in 30 patients across several doses.

On average, patients had received eight prior treatments. The majority (87%) had triple-refractory disease, with nearly all patients (97%) having received prior anti-CD38 therapy. Twenty-three percent of patients received BCMA-directed antibody drug conjugate or CAR-T cell therapy.

Patients who received doses at or above 215 μg/kg (20 patients) had the best outcomes, with an overall response rate (the percentage of patients whose disease shrunk in response to treatment) of 70%. Out of the 215-, 360-, 600-, and 1000-μg/kg dose groups, the highest dose had the best outcomes, with an 83.3% overall response rate, including 16.7% of patients with a complete response (meaning that they had no detectable disease), 50% with a very good complete response, and 16.7% with a partial response. Average time to response was 22 days, ranging from 21 to 50 days.

There were 14 patients with confirmed response to treatment; in this cohort, average duration of response (the length of time where cancer responds to treatment without growing) was not reached. There was a 92.3% probability of responders being event-free at six months.

Within the entire study population, the most common all-cause side effects were lymphopenia, a reduction of white blood cells, (83.3%); cytokine release syndrome (73%); anemia, a lack of healthy red blood cells (57%); injection site reaction (53%); thrombocytopenia, a decrease of blood platelets (53%); and neutropenia, a decrease in neutrophils (40%). There were no side effects that were so severe that they led to patients receiving a smaller dose of the drug.

Ultimately, Bahlis added, that these findings should lead to future studies of PF-06863135 alone and in combination with other drugs.

“These results clearly support the further development of (PF-06863135), both as monotherapy or in combination with other anti-myeloma agents,” he concluded.

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