Functional and Structural Characterization of Clinical-Stage Janus Kinase 2 Inhibitors Identifies Determinants for...

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Janus kinase 2 (JAK2) is crucial for hematopoiesis; its dysregulation causes myeloproliferative neoplasms (MPNs).
• Approved JAK inhibitors (ruxolitinib, fedratinib, momelotinib, pacritinib) offer symptom relief but have variable clinical profiles due to poor JAK selectivity.
• Developing next-generation JAK2 inhibitors is hindered by a lack of comparative functional analysis and understanding of selectivity mechanisms.

Purpose of the Study:

• To provide mechanistic profiling of approved and clinical-stage JAK2 inhibitors.
• To connect JAK2 inhibitor selectivity data with structural and thermodynamic analyses.
• To elucidate the molecular basis for JAK2 inhibitor selectivity and guide future drug development.

Main Methods:

• Mechanistic profiling of ten JAK2 inhibitors (four approved, six clinical-stage).
• Comparative functional analysis of JAK isoform selectivity and erythropoietin signaling potency.
• High-resolution structural and thermodynamic analyses of inhibitor-JAK2 interactions.

Main Results:

• All investigated JAK inhibitors potently inhibited JAK2 activity.
• Significant differences were observed in JAK isoform selectivity and erythropoietin signaling potency among inhibitors.
• Structural data revealed that targeting the ATP-binding site's front pocket can achieve high potency and moderate JAK2 selectivity.

Conclusions:

• Understanding JAK inhibitor selectivity is key for developing improved MPN therapies.
• Structural insights into the ATP-binding site offer a roadmap for designing next-generation JAK2 inhibitors with enhanced selectivity.
• Targeting the front pocket of the JAK2 ATP-binding site is a promising strategy for achieving potent and selective JAK2 inhibition.