New scaffolds for type II JAK2 inhibitors overcome the acquired G993A resistance mutation

Area of Science:

• Biochemistry
• Molecular Biology
• Oncology

Background:

• Recurrent Janus kinase 2 (JAK2) alterations drive myeloproliferative neoplasms and other hematologic malignancies.
• Existing type I JAK2 inhibitors demonstrate limited efficacy in these diseases.
• Type II JAK2 inhibitors, which stabilize an inactive kinase conformation, show potential for improved therapeutic activity.

Purpose of the Study:

• To identify and develop novel type II JAK2 inhibitors with enhanced efficacy and selectivity.
• To characterize the mechanism of action and in vivo activity of newly identified JAK2 inhibitors.
• To investigate resistance mechanisms and develop compounds that overcome them.

Main Methods:

• Screening of small molecule libraries to identify selective JAK2 inhibitors.
• Synthesis and biochemical/cellular evaluation of lead compound analogs.
• In vivo efficacy studies using a mouse model of polycythemia vera.
• Co-crystal structure determination to confirm the type II binding mode.
• Assessment of compound activity against JAK2 resistance mutations.

Main Results:

• A selective lead compound and its analogs with potent on-target biochemical and cellular activity were identified.
• Compounds demonstrated significant in vivo efficacy in a polycythemia vera mouse model.
• Co-crystal structure confirmed the type II binding mode, locking JAK2 in the 'DFG-out' conformation.
• Novel JAK2 analogs demonstrated activity against a G993A mutation conferring resistance to existing type II inhibitors.

Conclusions:

• The identified compounds represent a promising class of type II JAK2 inhibitors for treating JAK2-driven hematologic malignancies.
• These inhibitors demonstrate efficacy in preclinical models and can overcome specific resistance mutations.
• The findings provide a framework for developing next-generation JAK2-targeting therapies with improved resistance profiles.