Safety and activity of talquetamab in patients with relapsed or refractory multiple myeloma (MonumenTAL-1): a multicentre, open-label, phase 1–2 study

BACKGROUND: Talquetamab is the first GPRC5D × CD3 bispecific antibody approved for relapsed or refractory multiple myeloma. In phase 1 of the MonumenTAL-1 study, initial results of subcutaneous talquetamab 0·4 mg/kg once a week and 0·8 mg/kg every 2 weeks showed preliminary clinical activity. We describe safety and activity results in patients treated with talquetamab, including patients who had received previous T-cell redirection therapy (TCR). This post-hoc analysis was done with more mature median follow-up to evaluate duration of response in patients treated with talquetamab 0·8 mg/kg every 2 weeks. METHODS: MonumenTAL-1 is a multicentre, open-label, phase 1-2 study of talquetamab, phase 1 of which has previously been published. The 0·4 mg/kg once a week and 0·8 mg/kg every 2 weeks recommended subcutaneous doses identified in phase 1 were evaluated in phase 2 in patients who were 18 years of age or older, had at least three previous lines of therapy, had an Eastern Cooperative Oncology Group performance status of 0 to 2, and were naive or exposed to previous TCR. The primary endpoint was overall response rate assessed by independent review committee in all patients who received at least one dose of talquetamab. Safety was assessed in all patients who received at least one dose of talquetamab. This study was registered with ClinicalTrials.gov, NCT03399799 (phase 1) and NCT04634552 (phase 2). FINDINGS: Between Jan 3, 2018, and Feb 20, 2023, 735 patients were screened across all phase 1-2 cohorts. Of these, 537 patients screened for inclusion were treated across phase 1 and 2 cohorts, of whom 198 (27%) patients were excluded from the study, most commonly due to not meeting eligibility criteria or not having measurable disease. As of Oct 11, 2023, 375 patients had received recommended talquetamab doses across three groups: 143 (0·4 mg/kg once a week group) and 154 (0·8 mg/kg every 2 weeks group) TCR-naive patients and 78 with previous TCR who received either recommended dose (previous TCR group). 217 (58%) of 375 patients were male and 158 (42%) were female. 325 (87%) of 375 patients were White and 32 (9%) patients were Black. Median follow-up was 25·6 months (IQR 8·5-25·9) in the 0·4 mg/kg once a week group, 19·4 months (9·2-20·7) in the 0·8 mg/kg every 2 weeks group, and 16·8 months (7·6-18·7) in the previous TCR group. Overall response rate was 74% (106 of 143 patients, 95% CI 66-81) in the 0·4 mg/kg once a week group, 69% (107 of 154 patients, 62-77) in the 0·8 mg/kg every 2 weeks group, and 67% (52 of 78 patients, 55-77) in the previous TCR group. Most common adverse events in the 0·4 mg/kg once a week, 0·8 mg/kg every 2 weeks, and previous TCR groups were cytokine release syndrome (113 [79%] of 143 patients, 115 [75%] of 154 patients, and 57 [73%] of 78 patients), taste changes (103 [72%], 110 [71%], and 59 [76%]), and infections (85 [59%], 105 [68%], and 59 [76%]). Most common grade 3-4 adverse events were neutropenia (44 [31%], 33 [21%], and 37 [47%]), anaemia (45 [31%], 40 [26%], and 21 [27%]), and lymphopenia (37 [26%], 40 [26%], and 13 [17%]). Fatal adverse events occurred in five patients in the 0·4 mg/kg once a week group, seven patients in the 0·8 mg/kg every 2 weeks group, and no patients in the previous TCR group; none were related to treatment. INTERPRETATION: Talquetamab continued to demonstrate high overall response rates in heavily pretreated patients with relapsed or refractory multiple myeloma with longer follow-up in this post-hoc analysis. Overall response rate was promising in patients with previous TCR, including therapies targeting BCMA. On-target, off-tumour adverse events were common but led to few treatment discontinuations. FUNDING: Janssen.