Type I JAK2 inhibitors improve symptoms and outcomes of patients with myeloproliferative neoplasms (MPNs), but mutant allele JAK2 VF remains unchanged with this therapy. Type II JAK2 inhibitors bind the inactive conformation of the kinase domain and reduce the fraction of JAK2 VF mutant allele in vivo, suggesting an improved approach for JAK2 inhibition. Ajax Pharmaceuticals Inc. presented preclinical data on the type II JAK2 inhibitor AJ1-10502 for the treatment of MPNs.