Early trial data show potential effectiveness of blood cancer treatment

The first data from a small early clinical trial show Jubilant Therapeutics‘ oral therapy candidate JBI-802 may be effective for people with treatment-resistant myeloproliferative neoplasms (MPNs), a group of blood cancers that includes myelofibrosis.

In the ongoing Phase 1/2 study (NCT07612280), JBI-802 was found to rapidly and sustainably reduce levels of platelets, the tiny cell fragments that help blood to clot, with a manageable safety profile. The experimental treatment demonstrated early efficacy across multiple MPN subtypes in addition to myelofibrosis, with benefits seen for individuals with essential thrombocythemia (ET), polycythemia vera (PV), and myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN).

“These data suggest JBI-802 has the potential to offer a differentiated therapeutic option for patients living with these chronic hematologic [blood-related] malignancies,” Daniel O’Connor, president and CEO of Jubilant, said in a company press release announcing the positive data.

These early results were recently presented at the Society of Hematologic Oncology (SOHO) 2026 Annual Meeting, in a poster titled “Breaking the Limits of LSD1 Inhibition: Dual LSD1/HDAC6 Epigenetic Targeting with JBI-802 in MPNs.”

On the poster, the researchers noted that “meaningful platelet reductions were observed across all dose levels, with several patients achieving substantial and durable decreases from elevated [starting] platelet counts.”

Recommended Reading

Aug. 12, 2026 by Michela Luciano, PhD

New cancer drug shows some promise in resistant myelofibrosis

MPNs are chronic blood cancers caused by mutations in genes such as JAK2, CALR, and MPL. These variations drive the overproduction of blood cells in the bone marrow, the spongy insides of certain bones.

Myelofibrosis occurs when inflammation from these abnormal cells also leads to scar tissue buildup, known as fibrosis. Abnormalities are also seen in the other blood cancer types: In ET, the body makes too many platelets, while PV is marked by excess red blood cell production.

Primary myelofibrosis arises spontaneously without another precursor condition, while secondary myelofibrosis often occurs when ET or PV progresses, and abnormal blood cell growth ultimately causes scarring. MDS/MPN are conditions that combine features of both under-producing MDS and over-producing MPNs.

Despite existing treatments, many patients with MPNs continue to experience inadequate disease control.

JBI-802 is a potential first-in-class treatment for myelofibrosis

JBI-802 is a first-in-class therapy designed to block the activity of two enzymes, LSD1 and HDAC6, that are involved in the abnormal blood cell production seen in MPNs. This approach targets multiple disease-relevant processes simultaneously, such as abnormal platelet production, white blood cell growth, and inflammatory signaling.

The candidate medicine has a short half-life — the time it takes for drug levels to decrease by half in blood — of about 1.5 to two hours and is rapidly cleared from circulation in the body, the developer noted. This profile may support predictable drug exposure, reversible effects, and flexible dose adjustment, according to the company.

The Phase 1 part of the clinical trial is evaluating the safety, tolerability, and recommended dose of JBI-802 for the Phase 2 portion. It’s also assessing preliminary efficacy — namely platelet reduction — and molecular outcomes. Participants are taking the therapy orally, once daily, in continuous 28-day cycles.

As of June 30, the dose-escalation portion of the study had evaluated 12 people with heavily pretreated myelofibrosis, ET, PV, and MDS/MPN across four dosing groups. The therapy was tested at doses of 5 mg, 7 mg, 15 mg, and 20 mg. The scientists noted platelet reductions were observed across patients, with activity reported in JAK2-, CALR-, and MPL-mutant disease.

At the 15 mg dose, all three patients achieved platelet reductions of 72% to 81% within the first 30 days of treatment. One patient whose ET progressed to myelofibrosis achieved a maximum 5% platelet reduction within 30 days with the 7 mg dose. That dose was increased to 15 mg at week 37, resulting in an overall platelet reduction of 40%, according to the researchers.

Among nine ET/PV patients, platelet reductions ranged from 36% to 91%. Four ET/PV patients with extremely high platelet counts achieved reductions of 30% to 75% within the first 30 days, with maximum reductions during treatment ranging from 72% to 91%. Platelet responses were reported as durable and maintained through dose modification.

“These preliminary findings highlight several characteristics that we believe are important for the long-term management of myeloproliferative neoplasms,” O’Connor said.

We are particularly encouraged by the combination of meaningful clinical activity, prolonged treatment exposure, and a [pharmacological] profile that supports flexible dose adjustment.

In safety findings, no investigator-assessed dose-limiting toxicities were observed at the 5 mg, 7 mg, or 15 mg dose levels. One dose-limiting event of thrombocytopenia, or an abnormally low platelet count, occurred at the 20 mg dose level. This was managed with a protocol-defined dose reduction to 10 mg. The patient remained on treatment with platelet counts maintained within the normal range, the researchers noted.

Of the 12 treatment-emergent adverse events reported, 10 were mild to moderate (grades 1 and 2), while two were severe (grades 3 or higher). Still, no patients discontinued treatment because of thrombocytopenia or treatment-related adverse events, the team noted.

“In addition to rapid and sustained reductions in platelet counts across multiple MPN subtypes, JBI-802 has demonstrated a favorable tolerability profile, with patients remaining on treatment for more than six months and continuing to derive clinical benefit,” O’Connor said. “We are particularly encouraged by the combination of meaningful clinical activity, prolonged treatment exposure, and a [pharmacological] profile that supports flexible dose adjustment.”