Merck Announces Phase 3 Trial Initiation for Bomedemstat, an Investigational Candidate for the Treatment of Certain Patients With Essential Thrombocythemia

The initiation of a second Phase 3 clinical trial for bomedemstat demonstrates company’s commitment to advancing research in myeloproliferative neoplasms (MPNs)

Merck (NYSE: MRK), known as MSD outside of the United States and Canada, today announced the initiation of Shorespan-007, a pivotal Phase 3 clinical trial evaluating bomedemstat, an investigational orally available lysine-specific demethylase 1 (LSD1) inhibitor, for the treatment of patients with essential thrombocythemia (ET) who have previously not received cytoreductive therapy. Essential thrombocythemia is a chronic, rare blood disorder and is the most common type of myeloproliferative neoplasm. Global recruitment of the Shorespan-007 trial has begun, with patients now enrolling.

“The standard of care in essential thrombocythemia has remained unchanged for decades, and patients are in need of new options that have the potential to not only improve disease control, but also improve their quality of life,” said Dr. Gregory Lubiniecki, vice president, global clinical development, Merck Research Laboratories. “We are rapidly advancing our clinical development programs with the goal of helping to address these unmet needs and bring more options to patients living with myeloproliferative neoplasms.”

Shorespan-007 is a Phase 3, randomized, double-blind, active comparator-controlled clinical trial (NCT06456346) evaluating bomedemstat compared to the current standard of care chemotherapy, hydroxyurea, for treatment of patients with ET who have previously not received cytoreductive therapy. The trial will enroll approximately 300 patients globally. The primary endpoint of the study is durable clinicohematologic response rate (CHR). Key secondary endpoints include Myelofibrosis Symptom Assessment Form version 4.0 (MFSAF v4.0) individual fatigue symptom item score, Patient-reported Outcomes Measurement Information System (PROMIS) Fatigue SF-7a total fatigue score and MFSAF v4.0 total symptom score. Additional secondary endpoints include duration of hematologic remission, event-free survival and disease progression rate.

As previously announced, in addition to Shorespan-007, bomedemstat is also being investigated in Shorespan-006, a Phase 3, global, randomized, open-label, active comparator-controlled clinical trial (NCT06079879), evaluating bomedemstat compared to best available therapy as treatment in approximately 300 patients with ET who have an inadequate response to or are intolerant of hydroxyurea.

Bomedemstat has U.S. Food and Drug Administration Orphan Drug and Fast Track Designations for the treatment of ET and myelofibrosis (MF), Orphan Drug Designation for the treatment of acute myeloid leukemia and Priority Medicines scheme designation by the European Medicines Agency for the treatment of MF. Merck presented updated data from the Phase 2b Shorespan-003 trial, including first time genomic data, at the American Society of Hematology (ASH) Annual Meeting in December 2023. The Shorespan-003 trial is one of multiple Phase 2 clinical trials where bomedemstat is being evaluated alone and in combination for the treatment of MPNs such as ET, MF and polycythemia vera (PV).

About essential thrombocythemia

Essential thrombocythemia is a chronic, rare blood disorder that is the most common type of myeloproliferative neoplasm. Essential thrombocythemia is most often caused by genetic mutations that cause the bone marrow to produce too many platelets, which can obstruct blood flow and cause a stroke, heart attack or pulmonary embolism. The disease is more common in women than men and in people ages 50 to 70. It is estimated that fewer than 200,000 people in the U.S. have essential thrombocythemia, which can significantly impact quality of life due to burdensome symptoms. The most common symptoms are fatigue (reported in 90% of patients), insomnia, migraines, headache and dizziness.

About bomedemstat

Bomedemstat (MK-3543) is an investigational small molecule, irreversible LSD1 inhibitor being developed by Merck. LSD1 regulates the proliferation of hematopoietic stem cells, playing an essential role in cell differentiation and maturation. Bomedemstat is being evaluated in a wide range of MPNs, including ET, MF and PV.

Merck’s focus on cancer

Every day, we follow the science as we work to discover innovations that can help patients, no matter what stage of cancer they have. As a leading oncology company, we are pursuing research where scientific opportunity and medical need converge, underpinned by our diverse pipeline of more than 25 novel mechanisms. With one of the largest clinical development programs across more than 30 tumor types, we strive to advance breakthrough science that will shape the future of oncology. By addressing barriers to clinical trial participation, screening and treatment, we work with urgency to reduce disparities and help ensure patients have access to high-quality cancer care. Our unwavering commitment is what will bring us closer to our goal of bringing life to more patients with cancer. For more information, visit https://www.merck.com/research/oncology.

About Merck

At Merck, known as MSD outside of the United States and Canada, we are unified around our purpose: We use the power of leading-edge science to save and improve lives around the world. For more than 130 years, we have brought hope to humanity through the development of important medicines and vaccines. We aspire to be the premier research-intensive biopharmaceutical company in the world – and today, we are at the forefront of research to deliver innovative health solutions that advance the prevention and treatment of diseases in people and animals. We foster a diverse and inclusive global workforce and operate responsibly every day to enable a safe, sustainable and healthy future for all people and communities. For more information, visit www.merck.com and connect with us on X (formerly Twitter), Facebook, Instagram, YouTube and LinkedIn.

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