The phase III GRAVITAS-301 study did not meet its primary endpoint of improving overall response rate (ORR)

The randomized, double-blind, placebo-controlled pivotal phase III study, GRAVITAS-301 (NCT03139604), aimed to evaluate itacitinib (a novel and selective JAK1 inhibitor) versus placebo, both in combination with corticosteroids, as a first-line treatment in patients with treatment-naïve acute graft-versus-host disease.

On the 2^nd January 2020, a press release announced that GRAVITAS-301 did not meet the primary endpoint of improving overall response rate (ORR) at Day 28. The improvement in the ORR at Day 28, observed in the itacitinib arm versus the placebo arm (74% vs 66.4%, respectively; p= 0.08), was not statistically significant. The key secondary endpoint was non-relapse mortality at Month 6, and no difference was observed between the treatment and placebo arms.

The most common adverse events observed in GRAVITAS-301 were thrombocytopenia and anemia (34.9% vs 34.7% and 29.8% vs 25% in the itacitinib arm vs the placebo arm, respectively).