Among 73 patients who had already burned through a median of seven prior lines of therapy, including 75% who had received prior CAR-T or T-cell engager treatment, cemsidomide combined with dexamethasone produced a 53% overall response rate at the 100 µg recommended Phase 2 dose. That number carries weight not because it is unprecedented in relapsed/refractory myeloma, but because of who it was achieved in: a population where most approved and investigational agents struggle to clear 40% ORR, and where prior BCMA and cellular therapy exposure typically predicts diminishing returns.
The Phase 1 data, presented at EHA 2026, also show that responses deepened over time rather than plateauing. At the 100 µg level, patients who previously hit partial response later converted to stringent complete response and VGPR, and two patients achieved MRD-negative status. A median duration of response of 7.9 months with seven patients still on treatment reinforces that these are not transient signals. The safety picture is equally relevant for a drug being positioned as a long-term backbone: no discontinuations were attributed to cemsidomide, and only five patients (7%) required dose reductions, even though 58% experienced Grade 3/4 neutropenia, an on-target effect inherent to IKZF1/3 degradation that the field has learned to manage since pomalidomide’s approval in 2013.
The competitive context for next-generation IKZF1/3 degraders is real. Iberdomide (CC-220) has been in development along a similar trajectory, and C4T knows the differentiation argument must be built on tolerability and depth of response, not novelty of mechanism alone. Cemsidomide’s oral bioavailability and its MonoDAC molecular glue design are the structural claims C4T is leaning on, and the subgroup ORRs holding at 47% even in the post-CAR-T, post-BCMA-exposed cohort at the RP2D give that argument real clinical footing.
The number to track from here is the ORR in combination cohorts, particularly as C4T moves cemsidomide into regimens alongside approved IMiD-based and immune-based backbones. If combination data preserves the tolerability profile seen in this monotherapy-plus-dex Phase 1, the case for cemsidomide as a foundational rather than salvage agent becomes considerably harder to dismiss.
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
