Cullinan Therapeutics announced that the U.S. Food and Drug Administration has granted Fast Track designation to its FLT3xCD3 bispecific T‑cell engager CLN‑049 for the treatment of relapsed or refractory acute myeloid leukemia (AML). The designation signals that the FDA recognizes CLN‑049 as a promising candidate that could address an unmet medical need and may allow the company to accelerate the review process for future regulatory submissions.
CLN‑049 is engineered to bind both FLT3, a protein expressed on the surface of most AML cells, and CD3 on T‑cells, redirecting the patient’s own immune cells to attack the leukemia. The drug is intended for patients whose disease has returned after standard therapy or who have not responded to initial treatment, a population that currently has limited therapeutic options and a poor prognosis.
Phase 1 data presented at the 67th American Society of Hematology meeting on December 8, 2025 showed encouraging efficacy: at the highest target dose of 12 µg/kg, the overall response rate (ORR) was 69 % and the composite complete response rate (CRc) was 31 %. Across all patients receiving ≥6 µg/kg, the CRc rate was 30 % and the ORR was 57 %. Safety data indicated a manageable profile, with cytokine release syndrome and infusion‑related reactions occurring at rates consistent with other bispecific T‑cell engagers.
The Fast Track designation is a strategic win for Cullinan. It enables more frequent FDA interactions, potential rolling review, and priority review eligibility, all of which can shorten the time to market. The milestone also strengthens the company’s competitive positioning in the AML space, where few immunotherapies exist, and is likely to boost investor confidence in its oncology pipeline. Management emphasized that the designation provides momentum for development and underscores the broad applicability of CLN‑049 across FLT3‑positive AML patients, regardless of mutation status.
Dr. Jeffrey Jones, Chief Medical Officer, said the designation “underscores both the urgent need for new options in relapsed and refractory AML and the promise of CLN‑049.” He added that the early Phase 1 results “reinforce the broad potential of this FLT3‑directed T‑cell engager in a population where effective treatment options are currently limited and fragmented.”
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