YARDLEY, PA — Jubilant Therapeutics reported early clinical activity for JBI-802 in a Phase 1/2 trial of patients with myeloproliferative neoplasms, with dose-responsive platelet reductions observed across several disease subtypes as the company advances the experimental oral dual LSD1/HDAC6 inhibitor.
As of June 30, 12 patients had been evaluated across four dose cohorts of 5 mg, 7 mg, 15 mg, and 20 mg in the dose-escalation portion of the study.
At the 15 mg dose, all three patients experienced platelet reductions of 75%, 72% and 81%, respectively, within the first 30 days of treatment.
Among nine evaluable patients with essential thrombocythemia or polycythemia vera, platelet reductions ranged from 36% to 91%. Four patients with baseline platelet counts above 1,000 × 10⁹/L had reductions of 30% to 75% in the first 30 days and maximum reductions of 72% to 91% during treatment.
The company also reported platelet reductions in patients with myelofibrosis and myelodysplastic syndrome/myeloproliferative neoplasm, with activity observed across JAK2-, CALR- and MPL-mutated disease.
Jubilant characterized the responses as durable through dose modification, suggesting that platelet effects could be managed through changes in dosing.
No investigator-assessed dose-limiting toxicities were observed at the 5 mg, 7 mg or 15 mg dose levels. One dose-limiting thrombocytopenia event occurred at 20 mg and was managed through a protocol-defined dose reduction to 10 mg.
The patient remained on treatment after the dose adjustment, with platelet counts maintained within the normal range.
Of 12 treatment-emergent adverse events reported, 10 were Grade 1 or 2 and two were Grade 3 or higher. No patients discontinued treatment because of thrombocytopenia or treatment-related adverse events.
“These preliminary findings highlight several characteristics that we believe are important for the long-term management of myeloproliferative neoplasms,” Jubilant Therapeutics President and Chief Executive Officer Daniel O’Connor stated.
JBI-802 is designed to inhibit both LSD1 and HDAC6, two epigenetic regulators involved in abnormal blood-cell proliferation and production. Jubilant is developing the drug as a once-daily oral therapy for patients with relapsed, refractory or treatment-intolerant myeloproliferative neoplasms.
The molecule has an estimated half-life of about 1.5 to two hours, a pharmacokinetic profile the company believes may allow more flexible dose adjustment and faster reversal of hematologic effects when necessary.
The ongoing Phase 1/2 study, NCT07612280, is evaluating safety and tolerability, determining a recommended Phase 2 dose and assessing preliminary efficacy through platelet reduction, durability of hematologic response and molecular outcomes.
Enrollment remains ongoing, with Jubilant expecting to report additional efficacy, safety and molecular-response data as the program progresses.
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