Phase 2 multicenter trial of ofatumumab and prednisone as initial therapy of chronic graft-vs-host disease.

Standard initial therapy of chronic graft vs. host disease (cGVHD) with glucocorticoids results in suboptimal and transient responses in a significant number of patients. Safety and feasibility of anti-CD20 directed B-cell therapy with ofatumumab (1000 mg IV on days 0 and 14) and prednisone (1 mg/kg/day) was previously established in our phase I trial (n=12). We now report the mature results of the phase II expansion of the trial (n=38). The overall NIH severity of cGVHD was moderate (63%) or severe (37%) with 74% of all patients affected by the overlap subtype of cGVHD and 82% by prior acute cGVHD. The combined therapy was generally well tolerated, with some anticipated infusion reactions to ofatumumab, and common toxicities of glucocorticoids. Total B-cell depletion following therapy was profound, with marginal recovery within first 12 months from initial therapy. The observed 6 month clinician-reported and 2014 NIH-defined overall response rates (ORR=complete + partial response[CR/PR]) of 62.5% (1-sided lower 90% confidence interval=51.5%) were not superior to pre-specified historic benchmark of 60%. Post-hoc comparison of 6 month NIH response suggested benefit compared to more contemporaneous NIH-based benchmark of 48.6% with frontline sirolimus/prednisone (CTN 0801 trial). Baseline cGVHD features (organ involvement, severity, initial IS agents) were not significantly associated with 6-month ORR. The median time to initiation of second-line therapy was 5.4 months (range 0.9-15.1 months). Failure-free survival (FFS) was 64.2% (95% CI 46.5-77.4%) at 6 months and 53.1% (95% CI 35.8-67.7%) at 12 months, whereas FFS with CR/PR at 12 months of 33.5% exceeded a benchmark of 15% in post-hoc analysis, and was associated with greater success in steroid discontinuation by 24 months (odds ratio 8 (95% CI 1.21-52.7). This single-arm phase II trial demonstrated acceptable safety and potential efficacy of the upfront use of ofatumumab in combination with prednisone in cGVHD. This trial is registered at www.clinicaltrials.gov as NCT01680965.