Crenolanib is a selective type I pan-FLT3 inhibitor.

Area of Science:

• Oncology
• Pharmacology
• Biochemistry

Background:

• Tyrosine kinase inhibitors (TKIs) are crucial for treating malignancies.
• Maximizing TKI efficacy requires kinase selectivity and resistance to mutations.
• Existing TKIs often lack both selectivity and resistance to kinase domain mutations.

Purpose of the Study:

• To evaluate crenolanib, an investigational type I TKI, for its potency and selectivity against FLT3 mutations.
• To determine if crenolanib can overcome resistance mutations conferring resistance to other FLT3 TKIs.
• To assess crenolanib's potential to overcome clinical resistance in FLT3-mutant acute myeloid leukemia (AML).

Main Methods:

• Investigated crenolanib's inhibitory activity against FLT3 internal tandem duplication (ITD) and secondary mutations.
• Assessed crenolanib's selectivity for FLT3 over the related KIT kinase.
• Conducted a saturation mutagenesis screen to identify resistance mutations to crenolanib.

Main Results:

• Crenolanib potently inhibited FLT3-ITD and all tested resistance mutations.
• Crenolanib demonstrated high selectivity for FLT3 over KIT, unlike other FLT3 TKIs.
• No resistant FLT3-ITD colonies were recovered in mutagenesis screens, even at sub-therapeutic concentrations.

Conclusions:

• Crenolanib is the first TKI with both high kinase selectivity and invulnerability to resistance mutations.
• Its type I inhibition mechanism overcomes previous limitations.
• Crenolanib shows significant promise for deep, durable responses in FLT3-mutant AML and future TKI development.