Cemsidomide Elicits T-Cell Activation in C4 Therapeutics’ Multiple Myeloma Study

C4 Therapeutics Inc. (CCCC), a clinical-stage biopharmaceutical company specializing in targeted protein degradation, presented new biomarker data from its Phase 1 trial of cemsidomide with dexamethasone and its Phase 1b trial of cemsidomide with elranatamab (ELREXFIO) in patients with relapsed/refractory multiple myeloma at the 23rd International Myeloma Society Annual Meeting.

Data from 62 heavily pre-treated patients in the Phase 1 trial revealed coordinated activation of T cells, including CD8+ T cells, alongside functional changes in natural killer cells.

The most significant enhancement in immune cell activity was observed at the highest evaluated cemsidomide doses of 75 µg and 100 µg.

Initial findings from the first two patients in the Phase 1b trial indicated that cemsidomide promoted the expansion and activation of CD8+ effector memory T cells, evidenced by increased HLA-DR expression.

Early data also showed a reduction in markers associated with T-cell exhaustion, such as PD-1, TIM-3, and LAG3, when cemsidomide was combined with elranatamab.

These findings offer early biomarker evidence supporting the potential of cemsidomide as a combination partner for immune-based therapies in multiple myeloma.

Elranatamab is a BCMA-directed T-cell engager approved for treating certain patients with relapsed or refractory multiple myeloma.

Following review of safety data from the first six patients in the Phase 1b study, the safety data review committee deemed the 75 µg cemsidomide dose level, when combined with elranatamab, safe.

The Phase 1b trial is now advancing to a dose-escalation safety cohort evaluating 100 µg of cemsidomide and an expansion cohort evaluating the 75 µg dose.

The study is designed to assess the safety, tolerability, and preliminary efficacy of the combination.

Cemsidomide is an investigational oral cereblon-modulating protein degrader targeting IKZF1 and IKZF3, transcription factors involved in multiple myeloma biology.

C4 Therapeutics is evaluating the candidate as a potential combination therapy to enhance immune responses against myeloma cells.

Upcoming Milestones

C4 Therapeutics expects to evaluate data from all cohorts in the Phase 1b cemsidomide and elranatamab trial in mid-2027.

The company will continue advancing cemsidomide through clinical development in multiple myeloma, including dose escalation and expansion cohorts designed to further assess its safety, biomarker effects, and potential anti-myeloma activity.

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