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 treating physician according to the World Health Organization (WHO) * Treatment with ruxolitinib for ≥18 weeks prior to study entry, and on a stable dose of ruxolitinib 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 ruxolitinib treatment * Patients who have had a documented spleen response to ruxolitinib. * Prior splenectomy * Prior MDM2 inhibitor therapy or p53-directed therapy