A Phase I Trial of Janus Kinase (JAK) Inhibition with INCB039110 in Acute Graft-Versus-Host Disease (aGVHD)

Background: Corticosteroids are considered standard first-line systemic therapy for patients with aGVHD, but this approach is effective in only approximately half of all cases. For patients who progress or do not respond to corticosteroids, no specific agent has been identified as standard, and regimens are typically selected based on investigator experience and patient co-morbidities. In preclinical models, JAK inhibition has been shown to impair production of cytokines as well as the differentiation and trafficking of T cells implicated in the pathogenesis of aGVHD. Retrospective studies have suggested that JAK1/JAK2 inhibition with ruxolitinib treatment provides clinical benefit in patients with steroid-refractory GVHD (Zeiser et al, Leukemia 2015;29:2062-2068). Herein, we report preliminary safety results from a prospective randomized, parallel-cohort, open-label phase 1 trial evaluating the potent and selective JAK 1 inhibitor INCB039110 in patients with aGVHD.

Methods: Male or female patients 18 years or older who underwent their first allo-hematopoietic stem cell transplant (HSCT) from any donor source and developed grades IIB-IVD aGVHD were eligible for the study. Patients were randomized 1:1 to either a 200 or 300 mg oral daily dose of INCB039110 in combination with corticosteroids, and were stratified based on prior treatment status (treatment-naive [TN] versus steroid-refractory [SR]). The primary endpoint of the study was safety and tolerability; secondary endpoints included overall response rate at Days 14, 28, 56, and 100, non-relapse mortality, and pharmacokinetic (PK) evaluations. Patients were assessed through Day 28 for dose-limiting toxicities (DLTs) and response. A Bayesian approach was used for continuous monitoring of DLTs from Days 1-28. Treatment continued until GVHD progression, unacceptable toxicity, or withdrawal from the study. Acute GVHD was graded according to MN-CIBMTR criteria; adverse events (AEs) were graded according to NCICTCAE v 4.03.

Results: Between January and June 2016, 31 patients (TN, n=14; SR, n= 17) were randomized. As of July 25, 2016, data were available from 30 patients who received an oral daily dose of 200 mg (n=14) or 300 mg (n=16) INCB039110 in combination with 2 mg/kg methylprednisolone (or equivalent dose of prednisone). The median durations of treatment were 60.8 days and 56.5 days for patients receiving a daily dose of 200 mg and 300 mg INCB039110, respectively. One DLT of Grade 3 thrombocytopenia was reported. The most frequently reported AEs included thrombocytopenia/platelet count decrease (26.7%), diarrhea (23.3%), peripheral edema (20%), fatigue (16.7%), and hyperglycemia (16.7%). Grade 3 or 4 AEs occurred in 77% of patients and with similar frequency across dose groups and included cytomegalovirus infections (n=3), gastrointestinal hemorrhage (n=3), and sepsis (n=3). Five patients had AEs leading to a fatal outcome, including multi-organ failure (n=2), sepsis (n=1), disease progression (n=1), and bibasilar atelectasis, cardiopulmonary arrest, and respiratory distress (n=1); none of the fatal events was attributed to INCB039110. Efficacy and PK evaluations are ongoing and will be updated at the time of presentation.

Conclusion: The oral, selective JAK1 inhibitor INCB039110 can be given safely to steroid-naive or steroid-refractory aGVHD patients. The safety profile was generally consistent in both dose groups. Biomarker evaluation, PK, and cellular phenotyping studies are ongoing. The recommended phase 2 dose will be selected and reported based on PK studies and final safety data.