Evaluation of Ruxolitinib in Combination With PU-H71 for Treatment of Myelofibrosis

This is a multicenter 2-part, Phase 1b study designed to assess the safety, tolerability, PK and preliminary efficacy of PU-H71 (dihydrochloride salt) in subjects taking concomitant ruxolitinib. The first part (Dose Escalation) will employ a standard 3+3 dose escalation design to determine MTD. The second part of the study (Dose Confirmation) will confirm the RP2D in an expanded population. Up to 30 subjects who have active disease despite having received a minimum of 6 months of ruxolitinib therapy (including last 2 months at a daily dose of ≥5 mg twice daily and no more than one dose reduction 2-8 weeks prior to the baseline visit)stable dose will be enrolled to evaluate the safety, PK, and MTD of IV PU-H71 administered in combination ruxolitinib. Four ascending dose levels are planned. The planned dose levels of PU-H71 are 225 mg/m2, 300 mg/m2, 400 mg/m2, and 600 mg/m2. Additional dosing cohorts may be added at the discretion of the Safety Review Committee (SRC). Following a 28-day screening period, eligible subjects will receive PU-H71 once weekly intravenously for three consecutive weeks, followed by one week off on a 28-day cycle (D1, D8, D15, every 28 days). Ruxolitinib will be administered twice daily per the package insert at the stable dose the subject had been receiving prior to enrolling in the study. Subjects will have pk samples taken and ECGs performed at various time points throughout the study. Subjects will have safety evaluations including physical examinations, vital signs, laboratory assessments, and AE reporting. If deemed necessary, additional safety measurements will be performed at the discretion of the Investigator or the SRC. Subjects will be treated until disease progression, DLT, death, or study termination. At each dose level, a 3+3 dose escalation design will be employed. If none of the initial 3 subjects in the cohort experience a DLT within the first cycle, a new cohort of 3 subjects will be treated at the next higher dose level. If 1 of the 3 subjects in a cohort experiences a DLT, then 3 additional subjects will be treated at the same dose level as described under Dose Limiting Toxicities. Once the MTD has been determined in the dose escalation portion of the study, up to 15 patients may be enrolled for further evaluation of safety, PK, and preliminary clinical activity in a dose confirmation phase. A safety review committee (SRC) will assess the safety, tolerability, and available PK information collected for each dose level, decide whether to proceed to the next cohort, and determine the dose for the cohort.