Raje N, et al. - In this phase 1 study involving patients with relapsed or refractory multiple myeloma, researchers investigated the safety of bb2121, a chimeric antigen receptor (CAR) T-cell therapy that targets B-cell maturation antigen (BCMA). Outcomes revealed its antitumor activity. The most common events were hematologic toxic effects of grade 3 or higher, including neutropenia, leukopenia, anemia, and thrombocytopenia.

Methods

• In the dose-escalation phase, bb2121 was administered as a single infusion at doses of 50×10⁶, 150×10⁶, 450×10⁶, or 800×10⁶ CAR-positive (CAR+) T cells and in the expansion phase, at the doses of 150×10⁶ to 450×10⁶ CAR+ T cells.
• Participants received at least three previous lines of therapy, including a proteasome inhibitor and an immunomodulatory agent, or were refractory to both drug classes.
• Safety was assessed as the primary end point.

Results

• Researchers reported results for the first 33 consecutive patients who received a bb2121 infusion; following the last infusion date, the data-cutoff date was 6.2 months later.
• Hematologic toxic effects, including neutropenia (in 85% of the patients), leukopenia (in 58%), anemia (in 45%), and thrombocytopenia (in 45%), were identified to be the most common events of grade 3 or higher.
• Cytokine release syndrome was experienced by a total of 25 patients (76%), which was of grade 1 or 2 in 23 patients (70%) and grade 3 in 2 patients (6%); 14 patients (42%) experienced neurologic toxic effects, and 13 patients (39%) had grade 1 or 2.
• The objective response rate of 85% was reported; including complete responses in 15 patients (45%); relapse was reported in 6 of the 15 patients who had a complete response.
• Findings revealed the median progression-free survival of 11.8 months (95% confidence interval, 6.2 to 17.8).
• MRD-negative status (≤10−4 nucleated cells) was identified in all 16 patients who had a response (partial response or better) and who could be evaluated for minimal residual disease (MRD).