The U.S. Food and Drug Administration (FDA) has granted fast track designation to the experimental medicine FCLN-049, which is being developed as a potential treatment for relapsed or refractory acute myeloid leukemia (AML).
This designation aims to expedite the development of therapies with the potential to address unmet needs in the management of serious health conditions. Fast track status grants CLN-049’s developer, Cullinan Therapeutics, access to benefits such as more frequent communication with the FDA during the drug development process.
“Fast Track designation underscores both the urgent need for new options in relapsed and refractory acute myeloid leukemia and the promise of CLN-049,” Jeffrey Jones, MD, Cullinan’s chief medical officer, said in a company press release.
Jones said this designation “provides important momentum for development, and we look forward to collaborating closely with the FDA to rapidly advance CLN-049 for patients who desperately need more effective therapies.”
The challenge of treating relapsed or refractory AML
AML is an aggressive form of blood cancer. While treatments exist, the disease can be refractory, meaning it doesn’t respond to initial therapy, or relapsed, meaning it returns after a response. For people whose AML is relapsed or refractory, treatment options remain limited.
CLN-049 is designed to redirect the immune system to attack cancer cells. It binds to two proteins at the same time: FLT3, a receptor typically expressed at high levels on AML cells, and CD3, a protein expressed by cancer-killing immune cells called T-cells. By binding to both proteins simultaneously, CLN-049 aims to trigger the T-cells to attack the cancer cells. The therapy is given by intravenous infusion (into the bloodstream).
Cullinan is currently running a Phase 1 clinical trial (NCT05143996) testing various doses of CLN-049 in adults with AML or myelodysplastic syndrome (MDS), a precancerous blood disorder that can progress to AML. The study aims to enroll 60 participants with AML or MDS that is relapsed or refractory to available treatments. Recruitment is ongoing at nine sites across the U.S.
Early clinical results shared at the ASH 2025 meeting
At the 67th American Society of Hematology (ASH) Annual Meeting and Exposition, held Dec. 6-9 in Orlando, Florida, Cullinan presented interim data from the ongoing trial in an oral session on Dec. 8.
Data from 23 AML patients who received CLN-049 at a dose of 6 micrograms per kilogram (mcg/kg) or higher showed that 57% had a response, meaning their cancer decreased after treatment. About 30% achieved composite complete response, which indicates no detectable leukemia in the bone marrow, though some still had abnormal blood counts at the latest follow-up.
Among 13 patients treated at the highest dose (12 mcg/kg), 69% responded, and 31% achieved a composite complete response. Responses were seen across genetic risk groups, meaning patients responded regardless of baseline risk factors.
Safety data from 40 patients with AML or MDS showed that CLN-049 had a manageable safety profile, according to Cullinan. The most common side effects included infusion reactions, febrile neutropenia, pneumonia, mouth soreness (stomatitis), white blood cell count decreases, and cytokine release syndrome (an inflammatory disorder that can be triggered by immune-modulating cancer drugs). More than 10% of patients had white blood cell count decreases, febrile neutropenia, and/or pneumonia that was considered serious.
“Initial results from our Phase 1 study have shown meaningful efficacy, including complete responses, reinforcing the broad potential of this FLT3-directed T cell engager in a population where effective treatment options are currently limited and fragmented,” Jones said.
The post CLN-049 now has FDA fast track designation for hard-to-treat AML appeared first on Rare Cancer News.