Highlight
– Ramantamig (JNJ-79635322) is a trispecific T-cell engager directed at BCMA, GPRC5D, and CD3 designed to increase tumor binding avidity and overcome antigen-loss mediated resistance in multiple myeloma (MM).
– In preclinical models, ramantamig produced potent cytotoxicity at sub-nanomolar concentrations, depleted malignant plasma cells in patient ex vivo assays and whole-blood co-cultures, and showed tumor prevention and regression activity in murine xenograft models.
– These data support clinical translation; two phase 1 trials in relapsed/refractory MM (NCT05652335, NCT06768489) are ongoing to evaluate safety, tolerability, pharmacokinetics, and early efficacy.
This preclinical study demonstrates impressive sub-nanomolar potency of ramantamig, a trispecific T-cell engager simultaneously targeting BCMA and GPRC5D. The dual-antigen approach addresses a critical limitation of single-target immunotherapies: antigen escape. By engaging both BCMA and GPRC5D, ramantamig maintains activity against heterogeneous myeloma cell populations and cells that have downregulated either antigen—a mechanism frequently observed in post-CAR-T or post-bispecific relapses.
Clinical Utility: HIGH (for preclinical data). The construct showed consistent activity across multiple model systems: engineered cell lines, primary patient bone marrow samples, whole-blood co-culture, and xenograft models. The ability to deplete malignant plasma cells in ex vivo patient material is particularly encouraging, as it suggests the mechanism translates to clinically relevant disease biology. The ongoing phase 1 trials (NCT05652335, NCT06768489) will be critical to determine safety and early efficacy signals.
Would I implement this clinically? NOT YET—awaiting phase 1 safety data, but with high interest:
1) Monitor early-phase trial results closely for CRS profile, neurotoxicity incidence, and on-target off-tumor effects (particularly dermatologic toxicity from GPRC5D expression in skin/nails)
2) If safety is acceptable, prioritize enrollment of patients who have relapsed after BCMA-directed therapy (CAR-T, belantamab, teclistamab) to test the antigen-escape hypothesis
3) Evaluate MRD-negative response rates and duration compared with single-target bispecifics as key efficacy benchmarks
4) Consider sequencing strategies: whether trispecifics should be positioned before or after single-target BCMA therapies
5) Prepare institutional infrastructure for step-up dosing protocols and CRS management if approved
Key open question: Does dual targeting truly improve durability, or do other resistance mechanisms (T-cell exhaustion, immunosuppressive microenvironment) dominate in relapsed myeloma? Clinical data will clarify whether the mechanistic advantage translates into prolonged remissions.