PLX-2853

ORLANDO, Fla.--(BUSINESS WIRE)--Opna Bio, a clinical-stage biopharmaceutical company focused on the discovery and development of novel oncology therapeutics, announced promising preclinical data from the company’s novel, multi-functional protein degrader program and positive updated data from an ongoing Phase 1 combination study with OPN-2853, a bromodomain and extra-terminal motif (BET) inhibitor, as an add-on to ruxolitinib in patients with advanced myelofibrosis. "These promising data support our goal of developing a single agent ‘super drug’ for hematological malignancies, such as multiple myeloma and lymphoma." Data were shared in an oral and poster presentation this past weekend at the 67th Annual Meeting of the American Society of Hematology (ASH), taking place December 6-9, 2025, in Orlando, FL. Multi-Functional Degraders Designed to Block Key Oncogenic Pathways Using Single Chemical Entity Opna’s novel protein degraders are designed to block multiple oncogenic targets – EP300, CBP, IKZF1 and IKZF3 – concurrently in the same cancer cell, achieving potent single agent anti-tumor activity. EP300, CBP, IKZF1 and IKZF3 are known to promote the progression of multiple myeloma, a type of blood cancer derived from malignant plasma cells in the bone marrow. In a proof-of-concept OPM-2 multiple myeloma model, OPN-5667 potently reduced the levels of key oncoproteins in vitro and caused tumor regression in all treated animals in vivo. Opna’s medicinal chemistry campaign has produced compounds with improved potency and pharmacological properties, advancing the program towards clinical candidate selection. The degrader program is built on foundational studies presented at ASH in 2024 with OPN-6602, an oral EP300/CBP inhibitor, in combination with immunomodulatory drugs (IMiDs). The combination resulted in strong synergy in vivo including complete regressions and improved response durability. A Phase 1 study of OPN-6602 is currently enrolling patients with relapsed or refractory multiple myeloma at multiple sites in the U.S. “These promising data support our goal of developing a single agent ‘super drug’ for hematological malignancies, such as multiple myeloma and lymphoma,” said Gideon Bollag, PhD, chief scientific officer of Opna Bio. “We anticipate identifying a lead candidate in mid-2026 and submitting an IND in 2027.” OPN-2853 Reduces Spleen Size in Patients with Advanced Myelofibrosis OPN-2853, a potent, orally active small molecule BET inhibitor, is being evaluated as an add-on to ruxolitinib in the PROMise study in patients with myelofibrosis who are no longer responding to ruxolitinib. Myelofibrosis is a type of blood cancer that causes bone marrow fibrosis, anemia and an enlarged spleen, amongst other symptoms. As of October 2025, 29 patients had been enrolled across multiple sites in the United Kingdom. Fourteen patients were treated with 40 mg of OPN-2853 and 15 patients were treated with 80 mg of OPN-2853 added to ruxolitinib. In 16 of 26 evaluable patients, there was a 50% or greater reduction of their palpable spleen length on treatment when compared to baseline. The combination dose has been well tolerated, and the majority of patients have completed eight cycles of combination treatment. The investigator-initiated study is led by Professor Adam Mead at the University of Oxford through a collaboration with Cancer Research UK (CRUK) and is run through the Cancer Research UK Clinical Trials Unit at the University of Birmingham. “The emerging data from the PROMise study continue to be encouraging. We are now seeing consistent and clinically meaningful spleen size reductions, improvements in symptom burden, and durable benefit for patients who previously had limited options after an inadequate response to ruxolitinib alone,” said Dr. Mead. “These findings strengthen our view that selective BET inhibition alongside JAK inhibition may offer a new therapeutic approach for patients with myelofibrosis.” About Opna Bio Opna Bio is a clinical-stage biopharmaceutical company focused on the discovery and development of novel oncology therapeutics. The company’s broad portfolio targets multiple drivers of cancer, including OPN-6602, a dual EP300/CBP inhibitor, currently in a Phase 1 clinical trial in patients with multiple myeloma, and OPN-2853, a potentially best-in-class BET bromodomain inhibitor, in a combination Phase 1 clinical trial with ruxolitinib in patients with myelofibrosis. Our novel, preclinical multi-functional degrader program is focused on targeting EP300/CBP and Ikaros/Aiolos for the treatment of multiple myeloma and lymphomas. The Opna team has a proven track record of scientific expertise and commercial value creation, having discovered and developed multiple drugs that have achieved FDA approval. For more information, please visit opnabio.com.