ATLANTA (FRONTLINE MEDICAL NEWS) – The novel Janus kinase 1 (JAK1) inhibitor INCB052793 showed encouraging activity, particularly in combination with azacitidine, in certain patients with advanced myeloid malignancies in a phase 1/2 trial.

The activity was seen even in patients who previously failed treatment with hypomethylating agents, Amer M. Zeidan, MD, reported at the annual meeting of the American Society of Hematology.

During a monotherapy dose escalation study (phase 1a), treatment was given daily at doses of 25 mg (three patients), 35 mg (three patients) and 50 mg (four patients). During monotherapy dose expansion, 11 patients – 4 with myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN), 3 with multiple myeloma (MM), 2 with diffuse large B-cell lymphoma, and 1 each with chronic lymphocytic leukemia and Hodgkin’s lymphoma – received oral INCB052793 monotherapy at a dose of 35 mg daily for 21-day cycles.

In the combination therapy dose escalation phase (phase 1b), seven patients with MM received INCB052793 at doses of 25 mg or 35 mg daily plus dexamethasone, and nine patients with acute myeloid leukemia (AML) or MDS received INCB052793 plus azacitidine. During the dose expansion, 12 patients received a daily dose of 35 mg for 28-day cycles plus azacitidine (in AML and MDS patients), according to Dr. Zeidan of Yale University, New Haven, Conn.

The study employed a 3+3 dose-escalation design until dose-limiting toxicities occurred. Patients were treated in continuous cycles until study termination, consent withdrawal, disease progression, or unacceptable toxicity.

Phase 2 of the study is evaluating INCB052793 in combination with azacitidine in nine patients with AML or high-risk MDS who failed prior therapy with hypomethylating agents. The 35-mg daily dose was selected for this phase based on pharmacodynamic effect and the presence of thrombocytopenia in solid tumor patients at higher doses, he said.

At the data cutoff for this preliminary assessment, 1 of the 11 patients who received INCB052793 monotherapy – a patient with MDS/MPN – experienced complete response (CR) and remained on study at the data cutoff. Two monotherapy patients with MDS/MPN experienced partial remission (PR).

Of seven patients with MM in the INCB052793-plus-dexamethasone group, two had a minimal response with a reduction in M protein.

In the INCB052793-plus-azacitidine group, overall response rates were 67% in 12 patients with AML and 56% in patients with MDS or MDS/MPN.

In the AML group, there was one CR, one morphologic leukemia-free state, and two PRs. In the MDS group, three of seven patients had a CR. Among the two patients in the MDS/MPN group, one had a CR and one had a PR.

Of note, none of the seven patients in the INCB052793-plus-dexamethasone group had received prior treatment with hypomethylating agents, while 10 of 21 patients in the INCB052793-plus-azacitidine phase 1b group had, as well as all of the nine phase 2 patients. The results were as of Nov. 3, 2017, Dr. Zeidan said.

The JAK/STAT pathway plays an important role in cytokine and growth factor signal transduction. Dysregulation of the JAK/STAT pathway is associated with the pathogenesis of various hematologic malignancies, Dr. Zeidan explained, noting that blocking JAK signaling can inhibit AML cell proliferation through STAT3/5 inhibition and induction of caspase-dependent apoptosis.

INCB052793 is a small molecule JAK1 inhibitor with potential as monotherapy or in combination with standard therapies for treating advanced hematologic malignancies. It could be of particular benefit for high-risk MDS patients who have failed prior therapy with hypomethylating agents, as these patients have no available standard of care and their overall survival is often less than 6 months, he said.

These preliminary data show that treatment is associated with a number of nonhematologic and hematologic adverse events. Grade 3 or greater adverse events were observed in 45% of patients receiving INCB052793 monotherapy, 86% of patients receiving INCB052793 plus dexamethasone, and 95% of those receiving INCB052793 plus azacitidine.

The most common adverse events with INCB052793 plus dexamethasone were anemia, hypercalcemia, hypophosphatemia, pneumonia, sepsis, and thrombocytopenia. With INCB052793 plus azacitidine, the most common events were febrile neutropenia, anemia, neutropenia, and thrombocytopenia.

Most patients included in the current analysis discontinued treatment, including 91% of INCB052793 monotherapy patients, 100% of INCB052793-plus-dexamethasone patients, and 90% of INCB052793-plus-azacitidine patients. The primary reasons for discontinuation were disease progression or adverse events.

Despite these events, the findings suggest that combination therapy with INCB052793 and azacitidine is promising for patients with advanced myeloid malignancies, Dr. Zeidan said. However, signals of activity were lacking in multiple myeloma or lymphoid malignancies.

The findings of encouraging activity in patients who previously failed on hypomethylating agents are of particular interest, and suggest that INCB052793 might resensitize refractory/relapsed patients to the effects of these agents, Dr. Zeidan noted, concluding that these preliminary safety and efficacy data support further evaluation of INCB052793 in this setting. Enrollment is ongoing in phase 2 of the trial.

This study is sponsored by Incyte. Dr. Zeidan reported serving as a consultant for Incyte and Otsuka and as a member of the speakers bureau for Takeda. He also reported financial relationships with AbbVie, Pfizer, Gilead, Celgene, and Ariad.

SOURCE: Zeidan A et al. ASH 2017 Abstract 640 .