A Phase 1 Study of PRT12396 in Participants With Select Myeloproliferative Neoplasms

Inclusion Criteria: * Willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations (including contraception requirements), and other study procedures. * Confirmed diagnosis of PV or MF according to WHO 2016 or revised ICC/WHO 2022 criteria * Documented presence of a JAK2 V617 mutation * Eastern Cooperative Oncology Group (ECOG) performance status of 0-2 * Estimate life expectancy of ≥12 weeks per investigator assessment. * Negative serum or urine pregnancy test and agree to use contraception or maintain true abstinence. * Adequate organ function and bone marrow reserves (hematology, renal, and hepatic) Exclusion Criteria: * History of another malignancy within 3 years prior to enrollment, except for malignancy considered cured with low risk of recurrence. * Clinically significant anemia due to nutritional deficiency or hemolytic disorders. * Active or uncontrolled infection requiring systemic therapy or hospitalization. * Any other medical or psychiatric conditions that, in the Investigator's judgment, would increase risk or interfere with study participation or interpretation of results. * Clinically significant or uncontrolled medical conditions, including active infection or cardiovascular disease, that would increase risk or interfere with study participation. * Unresolved toxicity \> Grade 1 from prior anticancer therapy, except for alopecia or peripheral neuropathy ≤ Grade 2. * Pregnancy or breastfeeding * Known sensitivity or contraindication to any component of study, or the excipients of study treatment. * Prior systemic therapy for PV or MF, prior or planned allogeneic hematopoietic stem-cell transplantation, recent major surgery, prior splenectomy or prior splenic irradiation, or use of hematopoietic growth factors within protocol-defined washout periods. * Use of strong or moderate cytochrome P450 (CYP) 3A4 inhibitor or inducer, sensitive CYP3A substrates with narrow therapeutic range, or acid-reducing agents that cannot be discontinued prior to study treatment. * Participation in another interventional clinical study.