Study of Bomedemstat in Participants With Essential Thrombocythemia (IMG-7289-CTP-201/MK-3543-003)

A Phase 2 Multi-Center, Open Label Study to Assess the Safety, Efficacy and Pharmacodynamics of IMG-7289 in Patients With Essential Thrombocythemia

This is a Phase 2b open label study of an orally administered LSD1 inhibitor, Bomedemstat (MK-3543, formerly called IMG-7289), in patients with essential thrombocythemia.

This study investigates the following:

• The safety and tolerability of Bomedemstat
• The pharmacodynamic effect of Bomedemstat

This is a Phase 2 multi-center, open-label study evaluating the safety, efficacy and pharmacodynamics of Bomedemstat administered orally once daily in patients with essential thrombocythemia (ET). Patients will be dosed with Bomedemstat for 169 consecutive days in the Initial Treatment Period (ITP). Qualifying patients may continue to receive Bomedemstat in the Additional Treatment Period (ATP).

Safety will be evaluated by clinical assessments of safety parameters i.e., safety laboratory testing, adverse event reporting, physical examination and vital sign assessments. Pharmacodynamics will be evaluated by hematology assessment, patient reported symptom burden, change in spleen size by palpation and other measures.

To ensure safety, a Safety Advisory Board will perform periodic reviews of safety parameters and pharmacodynamic markers.

Inclusion Criteria:

• Diagnosis of Essential Thrombocythemia per World Health Organization (WHO) diagnostic criteria for myeloproliferative neoplasms.
• Requires treatment in order to lower platelet count based on patient age over 60 or history of thrombosis.
• Have failed at least one standard therapy
• Must have discontinued ET therapy at least 1 week (4 weeks for interferon) prior to study drug initiation.

Exclusion Criteria:

• Has undergone major surgery ≤4 weeks prior to starting study drug or has not recovered from side effects of such surgery.
• Unresolved treatment related toxicities from prior therapies (unless resolved to ≤ Grade 1).
• Uncontrolled active infection.
• Current use of prohibited medications
• Known HIV infection or active Hepatitis B or Hepatitis C virus infection
• Other hematologic/biochemistry requirements, as per protocol
• Use of investigational agent within last 14 days
• Pregnant or lactating females