P10: TALQUETAMAB, A G PROTEIN-COUPLED RECEPTOR FAMILY C GROUP 5 MEMBER D X CD3 BISPECIFIC ANTIBODY, IN PATIENTS WITH RELAPSED/REFRACTORY MULTIPLE MYELOMA (RRMM): UPDATED PHASE 1 RESULTS FROM MONUMENTAL-1
Authors: N. W. C. J van de Donk, M C Minnema, J G Berdeja, A Oriol, A Krishnan, P Rodríguez-Otero, E Askari, M Mateos, L. J Costa, R Verona, J Ma, S Girgis, S Yang, B. W Hilder, J Russell, J. D Goldberg, A Chari
Journal: HemaSphere (2022)

G protein-coupled receptor family C group 5 member D (GPRC5D) has limited expression in healthy human tissue but is highly expressed in malignant plasma cells, making it a promising target for immunotherapy approaches for MM. Talquetamab (JNJ-64407564) is a first-in-class bispecific antibody that binds to both GPRC5D and CD3 receptors to redirect T cells to kill MM cells. Updated and new results of talquetamab at the recommended phase 2 doses (RP2Ds) are reported (NCT03399799). Eligible patients had RRMM or were intolerant to standard therapies. Patients who were previously treated with B-cell maturation antigen (BCMA)-directed therapies were eligible. This analysis focuses on patients who received talquetamab subcutaneously (SC; range: 5.0–800 μg/kg) weekly (QW) or biweekly (Q2W) with step-up dosing. The primary objectives were to identify the RP2D (part 1) and assess talquetamab safety and tolerability at the RP2Ds (part 2). Adverse events (AEs) were graded by CTCAE v4.03; cytokine release syndrome (CRS) was graded per Lee et al 2014 criteria. Responses were investigator-assessed per IMWG criteria. As of July 19, 2021, 95 patients had received SC talquetamab. The original RP2D was 405 μg/kg SC talquetamab QW with step-up doses, and a second RP2D of 800 μg/kg SC talquetamab Q2W with step-up doses was also identified. 30 patients received 405 μg/kg QW (median 61.5 years [range 46–80]; 63% male; 100% triple-class exposed; 80% penta-drug exposed; 77% triple-class refractory, 20% penta-drug refractory; 30% prior BCMA-directed therapy; median follow-up [mF/U]: 7.5 mo [range 0.9–15.2]). 23 patients received 800 μg/kg Q2W (median 60.0 years [range 47–84]; 48% male; 96% triple-class exposed; 70% penta-drug exposed; 65% triple-class refractory, 22% penta-drug refractory; 17% prior BCMA-directed therapy; mF/U: 3.7 mo [range 0.0–12.0]). No treatment discontinuations due to AEs were reported at either RP2Ds. Most common AEs at the 405 μg/kg QW were CRS (73%; 1 grade 3 CRS), neutropenia (67%; grade 3/4: 60%), and dysgeusia (60%; grade 2: 29%). Skin-related AEs occurred in 77% of patients and were all grade 1/2 (nail disorders: 30%). Infections occurred in 37% of patients (1 grade 3 COVID-19 pneumonia). Most common AEs at 800 μg/kg Q2W were CRS (78%; all grade 1/2), dry mouth (44%; all grade 1/2), and neutropenia (44%; grade 3/4: 35%). Skin-related AEs occurred in 65% of patients with grade 3 events in 13% (nail disorders: 17%). Infections occurred in 13% of patients (1 grade 3 pneumococcal sepsis). In 30 response-evaluable patients treated at 405 μg/kg QW, the overall response rate (ORR) was 70% (very good partial response or better [≥VGPR]: 57%). In 17 response-evaluable patients treated at 800 μg/kg Q2W, the ORR was 71% (≥VGPR: 53%). Responses were durable and deepened over time with both RP2Ds (Figure). Median duration of response (DOR) was not reached at either RP2D; 6-month DOR rate was 67% (95% CI: 41–84) at 405 μg/kg QW. Serum trough levels of talquetamab were comparable at both RP2Ds. Pharmacodynamic data at both RP2Ds showed peripheral T cell activation and induction of cytokines. SC talquetamab is well tolerated and highly effective at both RP2Ds. Preliminary data suggest that less frequent, higher doses of SC talquetamab do not negatively impact the safety profile. Further evaluation of talquetamab as monotherapy (phase 2; NCT04634552) and in combination with other therapies in patients with RRMM is underway.