Developers partner on cemsidomide plus Elrexfio to treat myeloma
C4 expects to launch clinical trial next year to test combination treatment
C4 Therapeutics and Pfizer are teaming up to evaluate whether combining C4’s investigational oral therapy cemsidomide with Pfizer’s approved multiple myeloma treatment Elrexfio (elranatamab) can strengthen the immune system’s ability to fight the blood cancer.
Under the agreement, Pfizer will provide Elrexfio at no cost for C4’s planned Phase 1b clinical trial, set to begin before the end of June next year. The study will assess the safety of the combination treatment, and identify the optimal dose of cemsidomide to use alongside Elrexfio, according to a C4 press release announcing the collaboration.
“We look forward to initiating this trial to evaluate cemsidomide in combination with [Elrexfio] in the hopes we can develop a new treatment regimen and potentially improve outcomes for multiple myeloma patients in earlier lines of therapy,” said Andrew Hirsch, C4’s president and CEO.
Specifically, the developers hope that combining cemsidomide with Elrexfio “may amplify the anti-myeloma immune response and lead to [a] higher quality of responses” among myeloma patients, according to C4.
Multiple myeloma is a type of blood cancer that arises from the abnormal and uncontrolled growth of plasma cells, which are immune cells that normally produce antibodies to help fight infection. The cancer starts in the bone marrow — the spongy tissue at the center of the bones where blood cells are made — and can spread throughout the body, causing a range of symptoms.
Myeloma known to be hard-to-treat, and often recurs
Although several therapies — including Elrexfio — are available for multiple myeloma patients, the disease remains challenging to treat because it is often refractory, failing to respond or losing responsiveness to treatment, as well as relapsing, meaning it frequently returns despite treatment.
Cemsidomide, previously known as CFT7455, is designed to induce the selective degradation of IKZF1 and IKZF3, two proteins that multiple myeloma cells rely on for survival and proliferation. By promoting the removal of these proteins, cemsidomide is expected to suppress cancer cell growth and help control disease progression.
Our supply agreement with Pfizer creates an opportunity for cemsidomide to be combined with [Elrexfio], which is on the path to potentially becoming a standard of care [treatment] in a growing market.
An earlier Phase 1 clinical trial (NCT04756726) involving 72 adults with relapsed or refractory multiple myeloma showed that cemsidomide was well tolerated in combination with dexamethasone, a corticosteroid. That open-label trial — one in which both participants and researchers know the exact treatment being given — also found that this combination achieved lasting responses in this already heavily treated patient population. Phase 2 clinical testing is planned for early 2026, according to C4.
For its part, Elrexfio is approved in the U.S. and the European Union as a treatment for relapsing or refractory multiple myeloma. It contains an antibody that targets both B-cell maturation antigen (BCMA), a protein found on plasma cells, and CD3, found on immune T-cells. The therapy works to bring T-cells close to plasma cells, enabling their destruction.
In the U.S., Elrexfio can only be used in adults who have received at least four prior lines of therapy for their multiple myeloma. Such treatment includes a proteasome inhibitor, an immunomodulatory agent, and a CD38 inhibitor. In the European Union, the criterion is three or more prior lines of therapy in patients whose cancer has worsened since their last treatment.
Trial to test if cemsidomide-Elrexfio combo can enhance immune response
C4 believes that combining cemsidomide with Elrexfio could enhance the immune response against the cancer. The planned Phase 1b clinical trial will test the safety and tolerability of the combination of cemsidomide, Elrexfio, and dexamethasone as a second-line or later therapy. It will also determine the best dose of cemsidomide to use with Elrexfio.
“Our supply agreement with Pfizer creates an opportunity for cemsidomide to be combined with [Elrexfio], which is on the path to potentially becoming a standard of care BCMA×CD3 bispecific [an antibody that can target two different proteins at the same time] in a growing market,” Hirsch said.
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