Biomarker Analysis in Patients (pts) with Steroid-Refractory Acute Graft-Vs-Host Disease (aGVHD) Treated with Ruxolitinib (RUX) or Best Available Therapy (BAT) in the Randomized, Phase 3 REACH2 Study

BACKGROUND aGVHD, a common complication of allogeneic stem cell transplant (alloSCT), is driven by proinflammatory cytokines and chemokines that activate the immune system, resulting in end-organ damage. Steroids are first-line treatment but up to 50% of pts are steroid refractory (SR), resulting in high mortality and morbidity. RUX, a JAK1/JAK2 inhibitor, inhibits cytokine-dependent activation of the JAK-STAT pathway and cell proliferation and differentiation, which prevents worsening of aGVHD and allows recovery. JAK pathway inhibition by RUX may also lead to modulation of proinflammatory cytokines and prognostic GVHD biomarkers. The phase 3 randomized REACH2 trial (NCT02913261) in SR aGVHD demonstrated superiority of RUX vs BAT, with a significantly higher overall response rate (ORR; complete [CR] + partial response [PR]) at D28 (62% vs 39%; P < .001) and higher durable ORR at D56 (40% vs 22%; P < .001) (Zeiser R, et al. N Engl J Med. 2020). In this exploratory analysis of REACH2, we assessed whether baseline (BL) levels of proinflammatory cytokines and GVHD markers were prognostic for response and how this changed over time related to treatment. METHODS Pts (N = 309; ≥ 12 y old with grade II-IV SR aGVHD after alloSCT) were randomized 1:1 to RUX (starting at 10 mg bid) or investigator-selected BAT and stratified by aGVHD grade; 295 pts had valid biomarker levels. Serum samples were collected at BL, D14, and D28 and biomarkers, including inflammatory cytokines, soluble receptors of cytokines, chemokines, and tissue-specific markers for gastrointestinal (GI), liver, and skin GVHD, were assessed (Table). Biomarker levels at BL were stratified by response (CR, PR, none [NR]) at D28 for each treatment arm; those that differed by response were analyzed by logistic regression (LR) to assess the association (CR+PR vs NR), adjusting for treatment. The analysis was repeated, adjusting for key covariates that had significant impact on the biomarker-response relationship. Change in biomarkers over time (BL to D28) was assessed via geometric mean values at each visit, along with fold change from BL for each treatment arm. RESULTS Of 22 GVHD biomarkers assessed, 17 (77%) were evaluable (Table). Higher median BL levels of proinflammatory cytokines (IL-6, IL-8, TNF-α), soluble cytokine receptors (IL2RA, TNFRSF1A, ST2) and tissue-specific GVHD markers (REG3A, HGF) were generally observed in NR vs CR pts (Table) and were further analyzed. Higher BL levels of these marker