An Open-Label, Multicenter, Phase 1b/2 Study of the Safety and Efficacy of KRT-232 Combined With Ruxolitinib in Patients With Primary Myelofibrosis (PMF), Post-Polycythemia Vera MF (Post-PV-MF), Or Post-Essential Thrombocythemia MF (Post ET-MF) Who Have a Suboptimal Response to Ruxolitinib

Inclusion Criteria:

• Confirmed diagnosis of PMF, post-PV MF, or post-ET MF, as assessed by treatingphysician according to the World Health Organization (WHO)
• Treatment with ruxolitinib for ≥18 weeks prior to study entry, and on a stable dose ofruxolitinib in the 8 weeks prior to study entry
• Spleen ≥5 cm palpable below the LLCM or ≥450 cm3 by MRI or CT
• Patients must have at least 2 symptoms with a score of at least 1 on the MFSAF v4.0
• ECOG performance status of 0 to 2

Exclusion Criteria:

• Patients who are positive for TP53 mutations
• Documented disease progression or clinical deterioration any time while on ruxolitinibtreatment
• Patients who have had a documented spleen response to ruxolitinib.
• Prior splenectomy
• Prior MDM2 inhibitor therapy or p53-directed therapy