Cullinan Therapeutics doses first patient in pivotal CLN-049 AML study
Cullinan Therapeutics has dosed the first patient in a pivotal Phase 2 study of CLN-049, its investigational FLT3xCD3 T cell engager, in adults with relapsed or refractory acute myeloid leukaemia (AML). The milestone follows a successful End-of-Phase 1 meeting with the US Food and Drug Administration and marks a significant step forward for a programme carrying both Orphan Drug and Fast Track designations.
The Nasdaq-listed company (CGEM) said the study is designed to be potentially registrational. It incorporates a short dose-optimisation phase evaluating two target dose levels before seamless advancement to a single-arm expansion cohort at the recommended Phase 2 dose. The design also includes an exploratory cohort for patients with newly diagnosed TP53-mutated AML, a genetically high-risk population with particularly limited treatment options.
How CLN-049 works
CLN-049 is engineered to bind FLT3, a receptor tyrosine kinase overexpressed on leukaemic blasts, and CD3 on T cells simultaneously, redirecting cytotoxic T cell activity against FLT3-expressing tumour cells. Crucially, it is designed to engage both mutated and non-mutated forms of FLT3, which the company says makes it applicable across a broad patient population regardless of mutation status. This breadth of coverage is clinically meaningful in AML, where FLT3 mutations are present in roughly one-third of patients but FLT3 overexpression is far more widespread.
In parallel with the registrational study, Cullinan is initiating a Phase 1/2 combination trial evaluating CLN-049 alongside azacitidine and venetoclax in newly diagnosed AML. The aza-ven doublet has become a standard backbone for older or unfit patients since its approval, and testing a T cell engager on top of that regimen reflects an emerging combination strategy across the AML field. A Phase 1 dose-escalation update is expected in December 2026.
Jeffrey Jones, Chief Medical Officer at Cullinan, said the study addressed "an urgent need for new treatment approaches that can benefit a broad range of patients" with relapsed or refractory AML.
Market context and competitive landscape
AML is the most common acute leukaemia in adults, with approximately 23,000 new US diagnoses each year. Five-year survival for relapsed or refractory disease sits at 10% or below, and no approved immunotherapy exists in the indication. That gap has attracted substantial industry attention: T cell engager and CAR-T programmes from several companies are in active development for AML, including bispecifics targeting CD123, CD33, and FLT3. The field is crowded but pre-commercial, meaning a first approval in AML immunotherapy would carry considerable commercial and scientific weight.
Cullinan's strategy of pursuing FLT3 as the tumour-side anchor is shared by a number of other developers, which means differentiation will ultimately hinge on the safety and durability data generated in pivotal-stage studies. Cytokine release syndrome and on-target, off-tumour effects on normal haematopoietic progenitors, which also express FLT3, remain the principal safety considerations for this class. Investors and clinicians will look closely at the December Phase 1 update for early efficacy signals and the tolerability profile before drawing conclusions about CLN-049's competitive position.
With the registrational study now enroling and combination work beginning concurrently, Cullinan is running an ambitious parallel development strategy that compresses its timeline but also concentrates execution risk.