Bomedemstat for Polycythemia Vera After Standard Treatments Fail

Polycythemia vera (PV) is a myeloproliferative neoplasm (MPN). MPNs like PV are blood cancers in which the bone marrow makes too many blood cells. Most cases are driven by a mutation in the JAK2 gene, which causes overproduction of red blood cells and often platelets and white blood cells.

New Phase 2 data suggest that bomedemstat may help control blood counts and symptoms when PV no longer responds to standard treatments. Bomedemstat is an investigational therapy taken by mouth. 

The results were shared at the 2025 American Society of Hematology (ASH) annual meeting in December.

The need to expand treatment options for polycythemia vera 

Current PV treatments mainly focus on reducing blood clot risk and managing symptoms. Common treatments include phlebotomies or medications that reduce red blood cell counts. Phlebotomy is the removal of blood from the body. To treat PV, around 1 unit of blood is removed at one time. This is about the same amount as a standard blood donation. More options are needed as most existing ones become resistant on the long-term course of the disease

What is bomedemstat, and how does it work?

Bomedemstat is an irreversible inhibitor of lysine-specific demethylase 1 (LSD1). An irreversible inhibitor means that it completely inactivates the enzyme LSD1.   Once bomedemstat is given, it cannot be undone with a different medication. 

LSD1 is an enzyme involved in regulating how blood cells mature, especially red blood cells and platelets. 

By targeting LSD1, bomedemstat is intended to:

• Normalize blood cell production
• Reduce the need for phlebotomy
• Improve disease-related symptoms

Although bomedemstat is still under investigation, it has previously shown efficacy in other MPNs, including myelofibrosis and essential thrombocythemia.

A study for PV resistant to therapy 

SHORES PAN-004 is an open-label Phase 2 clinical trial evaluating bomedemstat in adults with polycythemia vera who were resistant or intolerant to at least one prior cytoreductive therapy. The study included 20 previously treated PV patients with a median age of 67.5. All received oral bomedemstat starting at 40 mg daily, with dose adjustments to maintain a hematocrit below 45%.

• Most had prior thrombotic events (blood clots) or significant symptom burden
• All participants had preserved bone marrow function and low fibrosis scores meaning that their bone marrow was capable of producing a sufficient amount of healthy blood cells 

The study showed meaningful improvements across multiple disease markers:

• More controlled red blood cell production below 45% without phlebotomy by week 52, and a median duration of control was over 6 months. 
• There was also a platelet reduction in 90% of patients, with platelet counts to 450 × 10⁹/L or lower, lasting a median of 9.4 months. 
• 85% achieved white blood cell counts below 10 × 10⁹/L at some point and the median duration of response exceeded 8 months

How bomedemstat improved symptoms

Symptom burden was measured using the Myelofibrosis Symptom Assessment Form (MFSAF), a validated patient-reported questionnaire. By week 36 participants had a meaningful reduction in symptoms, and the improvements were maintained through week 52. 

What about safety and side effects?

Bomedemstat demonstrated a manageable safety profile.

• Most treatment-related side effects were mild or moderate.
• Only 10% experienced severe (grade 3–4) blood count changes.
• No patients stopped treatment due to drug-related side effects.
• No new thrombotic events were reported during the study.

While larger studies are still needed, this Phase 2 trial suggests bomedemstat could become a meaningful new treatment option for people living with difficult-to-treat polycythemia vera, as it has proven to:

• Control red cells, platelets, and white blood cells
• Reduce symptom burden
• Limit reliance on repeated phlebotomy

If you or a loved one is living with polycythemia vera and current treatments are no longer working, ongoing research like this offers real reasons for hope. 

Clinical trials continue to expand options that focus on improving daily life, symptoms, and long-term health. Staying informed and asking your care team about emerging therapies can help you take an active role in your care.

SUBSCRIBE TO NEWSLETTER

Explore more clinical trials and use our filters for personalized options with our clinical trial finder.

CLINICAL TRIAL FINDER

Source: Efficacy and safety of the LSD1 inhibitor bomedemstat in participants with polycythemia vera (PV) resistant or intolerant to cytoreductive therapy: The Phase 2 shorespan-004 study