On June 11, 2026 C4 Therapeutics, Inc. (C4T) (Nasdaq: CCCC), a clinical-stage biopharmaceutical company dedicated to advancing targeted protein degradation (TPD) science, reported it will present further analysis from its fully enrolled Phase 1 trial of cemsidomide, a next-generation oral IKZF1/3 degrader, in combination with dexamethasone for the treatment of relapsed/refractory multiple myeloma (RRMM) in a poster presentation at the European Hematology Association (EHA) (Free EHA Whitepaper) 2026 Congress on Friday, June 12, 2026 at 6:45 pm CEST / 12:45 pm ET.

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The analysis is consistent with previous data disclosed from the Phase 1 clinical trial and highlights cemsidomide’s anti-myeloma activity and differentiated safety profile, further supporting its development as a potential best-in-class IKF1/3 degrader. The poster will be presented by Sagar Lonial, M.D., FACP, FASCO, chief medical officer at the Winship Cancer Institute at Emory University, and an investigator in the cemsidomide clinical trials.

"Despite advances in multiple myeloma therapies, IKZF1/3 degradation remains a foundational treatment strategy across lines of therapy because it is the only approach that addresses the underlying biology of the disease and has the built-in ability to stimulate the immune function, becoming a natural partner for immune therapies. Next-generation IKZF1/3 degraders are expected to help advance treatment regimens for this persistent disease, given data demonstrating their efficacy and tolerability," said Dr. Lonial. "The clinical activity and safety profile of cemsidomide are highly encouraging for patients with relapsed/refractory multiple myeloma as they continue to seek disease-altering treatment options. The data from the ongoing Phase 1 study support the continued development of cemsidomide for patients with relapsed/refractory multiple myeloma who may benefit from IKZF1/3 degradation."

"The totality of cemsidomide data, particularly data showing that patients have experienced a deepening response over time, continue to demonstrate its potential to deliver a tolerable therapy that can provide sustained benefit for patients who have progressed through other treatment options," said Len Reyno, M.D., chief medical officer of C4 Therapeutics. "We remain focused on advancing our clinical development strategy to capitalize upon cemsidomide’s differentiated profile in hopes patients at various stages of their treatment journey may be able to benefit from this important investigational therapeutic regimen."

The poster presentation includes data on 73 patients with a data cutoff of February 27, 2026. Patients were heavily pretreated, receiving a median of seven prior lines of therapy. Fifty-five patients (75%) received prior BCMA therapy, and 55 patients (75%) received prior CAR-T or T-cell engager therapy (TCE).

At the RP2D and maximum tolerated dose (100 µg,) cemsidomide achieved a 53% overall response rate (ORR). At the 75 µg dose level, cemsidomide achieved a 40% ORR. Across all doses evaluated, cemsidomide achieved a 36% ORR.

Key new data include:

Responses deepened over time across the cemsidomide 75 µg and 100 µg dose levels:
At 75 µg, one patient whose best response was previously a partial response (PR) deepened to a very good partial response (VGPR).
At 100 µg, several patients achieved a deeper response:
One patient whose best response was previously a PR deepened to a stringent complete response (sCR)
One patient whose best response was previously a PR deepened to a VGPR
Minimal residual disease (MRD) negativity was achieved in two patients who achieved a sCR and complete response (CR) at 100 µg.
ORR was consistent across key subgroups:

ORR % (95% confidence interval (CI))
All Doses
Prior CAR-T or TCE 37% (24, 51)
Prior BCMA 33% (21, 48)
Prior Lines of Therapy > 5 Lines 33% (20, 48)
100 µg (RP2D)
Prior CAR-T or TCE 53% (28, 77)
Prior BCMA 47% (21, 73)
Prior Lines of Therapy > 5 Lines 47% (21, 73)

Durable responses were observed across all dose levels:
Patients experienced a median duration of response of 7.9 months (95% CI, 3.0 – non-evaluable).
Seven patients remain on treatment currently.

Cemsidomide in combination with dexamethasone was generally well tolerated. Incidences of on-target neutropenia remained manageable; 42 patients (58%) experienced Grade 3/4 neutropenia. All treatment emergent adverse events were manageable with no discontinuations deemed related to cemsidomide and minimal dose reductions (five patients; 7%).

UPCOMING INVESTOR EVENTS

June 18, 2026 at 9 am ET: C4T will host an educational webinar with Nisha Joseph, M.D., associate professor at the Winship Cancer Institute at Emory University and investigator in the cemsidomide clinical trials to discuss the evolving multiple myeloma landscape, the role of IKZF1/3 degradation in treating multiple myeloma, and cemsidomide’s profile.

About Cemsidomide
Cemsidomide is an investigational, next-generation orally bioavailable MonoDAC degrader (molecular glue) of IKZF1/3, transcription factors foundational to multiple myeloma biology. Data from the fully enrolled Phase 1 trial show cemsidomide’s differentiated safety and tolerability profile and potentially class-leading anti-myeloma activity that support the potential for durable outcomes.

About Multiple Myeloma
Multiple myeloma is a blood cancer that affects plasma cells in the bone marrow. It is the second most common blood cancer, with approximately 36,000 people in the United States diagnosed each year. Multiple myeloma is characterized by cycles of remission and relapse, which leads to patients needing multiple lines of therapy to manage this persistent disease. More than 175,000 patients in the United States are estimated to be living with or in remission from myeloma. However, despite treatment advances, approximately 40% of patients do not survive beyond five years.

About IKZF1/3 Degradation
Targeted degradation of IKZF1 (Ikaros) and IKF3 (Aiolos) is a foundational therapeutic strategy to treat multiple myeloma, a blood cancer affecting plasma cells. IKZF1/3 degradation leads to downregulation of IRF4, which promotes myeloma cell death. IKZF1/3 degradation also activates T-cells, which contributes to broader anti-myeloma response. For decades, IKZF1/3 degradation has been used in approved therapies for multiple myeloma. Next-generation IKZF1/3 degraders are being developed to leverage advances in targeted protein degradation research while continuing to address the biology foundational to multiple myeloma.

About the MOMENTUM Trial
MOMENTUM (Multi-center trial Of cemsidoMidE iN relapsed/refracTory mUltiple Myeloma) is a Phase 2, open-label, single-arm study to evaluate the efficacy, safety, pharmacokinetics and pharmacodynamics of cemsidomide in combination with dexamethasone in patients with relapsed/refractory multiple myeloma. Data from the Phase 1 trial identified 100 µg as the recommended Phase 2 dose. The primary endpoint is overall response rate per International Myeloma Working Group response criteria, as assessed by an independent review committee. Approximately 100 patients who have received at least three prior anti-myeloma regimens that must have included an IKZF1/3 degrader, a proteasome inhibitor, an anti-CD38 antibody, and a T-cell engager or CAR-T therapy will be enrolled in the trial. More information is available at clinicaltrials.gov (NCT07284758).

About Cemsidomide in Combination With Elranatamab (ELREXFIO)
The Phase 1b trial is designed to evaluate the safety, tolerability and preliminary efficacy of cemsidomide and dexamethasone in combination with elranatamab, an FDA-approved B-cell maturation antigen CD3 targeted bispecific antibody. Data generated from the cemsidomide Phase 1 trial in relapsed/refractory multiple myeloma demonstrate robust T-cell activation and cytokine expression across multiple doses. By activating immune T-cells, cemsidomide, when combined with a BCMAxCD3 bispecific such as elranatamab, may amplify the anti-myeloma immune response and lead to deeper and more durable responses. The study will evaluate different cemsidomide dose levels (beginning with 75 µg, with the opportunity to simultaneously explore 50 µg and 100 µg) in patients who have received one to four prior lines of therapy, which must have consisted of at least one IKZF1/3 degrader. Exclusion criteria for patients include those who have received prior treatment with a BCMA-directed T-cell engager or BCMA-directed CAR-T therapy. More information is available at clinicaltrials.gov (NCT07280013).

(Press release, C4 Therapeutics, JUN 11, 2026, View Source [SID1234666596])