Ruxolitinib for pediatric patients with treatment-naïve and steroid-refractory acute graft-versus-host disease (REACH4)

• Ruxolitinib demonstrated clinically meaningful efficacy in pediatric patients with either treatment‑naïve or steroid-refractory aGvHD

• We identified the ruxolitinib dosage across the pediatric age range treated, and no unexpected safety signals were observed in children

In REACH4 (NCT03491215), a phase 1/2, open-label, single-arm, multicenter study, the pharmacokinetics (PK), efficacy, and safety of ruxolitinib were evaluated in treatment-naïve and steroid-refractory pediatric patients with grade II-IV acute graft-versus-host disease (aGVHD; n=45). Ruxolitinib dosing was based on age and targeted the exposure in adults receiving 10 mg twice daily; group 1 (≥12 to <18 years) received 10 mg twice daily and preliminary starting doses for groups 2 (≥6 to <12 years) and 3 (≥2 to <6 years) were 5 mg twice daily and 4 mg/m2 twice daily, respectively. Phase 1 primary objective was to assess ruxolitinib PK parameters and define an age-appropriate recommended phase 2 dose (RP2D) for patients <12 years of age. Phase 2 primary objective was to measure the activity of ruxolitinib as assessed by overall response rate (ORR) at day 28; the key secondary objective was to assess the durable ORR at day 56. Ruxolitinib exposure was comparable across age groups; starting doses were confirmed as the RP2D. The median duration of ruxolitinib exposure was 3.8 months (range 0.3-11.2). ORR in all patients was 84.4% (90% confidence interval [CI], 72.8-92.5) at day 28, with a durable ORR at day 56 of 66.7% (90% CI, 53.4-78.2); high response rates were observed across age groups and in both treatment-naïve and steroid-refractory subgroups. Adverse events were consistent with those expected in ruxolitinib-treated patients with aGvHD (anemia, decreased neutrophil and leukocyte count). In pediatric patients with aGvHD, ruxolitinib showed clinically meaningful efficacy with no new safety signals.