Results from REACH1, a Single-Arm Phase 2 Study of Ruxolitinib in Combination with Corticosteroids for the Treatment of Steroid-Refractory Acute Graft-Vs-Host Disease

Introduction:

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potentially curative treatment option for patients with high-risk or relapsed hematologic malignancies. Development of acute graft-vs-host disease (aGVHD) is a risk factor for nonrelapse mortality after allo-HSCT. Systemic corticosteroids (CS) are recommended first-line treatment for aGVHD, but <50% of patients (pts) achieve sustained responses, and there are no approved therapies for steroid-refractory (SR) aGVHD. Ruxolitinib (RUX) is an oral, selective inhibitor of Janus kinase (JAK)1/JAK2 signaling, implicated in GVHD pathogenesis. Retrospective studies showed clinical benefit from RUX in pts with SR aGVHD. Here, we report results from the REACH1 trial (NCT02953678) evaluating RUX plus CS in SR aGVHD.

Methods:

REACH1 was an open-label, single-cohort, multicenter, phase 2 study. Eligible pts were ≥12 years old, had an allo-HSCT from any donor source for hematologic malignancies, developed grade II-IV SR aGVHD per Mount Sinai Acute GVHD International Consortium criteria, and had ≤1 systemic treatment in addition to CS for aGVHD. SR aGVHD was defined as GVHD that progressed after 3 days or had not improved after 7 days of primary treatment with methylprednisone ≥2 mg/kg/d (or equivalent), development of GVHD in another organ after receiving CS (≥1 mg/kg/d methylprednisone) for skin or skin plus upper gastrointestinal GVHD, or inability to tolerate CS taper. Pts received RUX 5 mg twice daily (BID), with optional increase to 10 mg BID in the absence of cytopenias. The primary endpoint was overall response rate (ORR) at Day 28, defined as the proportion of pts having complete response (CR), very good partial response, or partial response (PR). The key secondary endpoint was 6-month duration of response (DOR; time from first response to GVHD progression or death).

Results:

At the primary analysis of ORR (02 Apr 2018), 71 pts received ≥1 dose of RUX. Mean (range) age was 52.9 (18-73) years; 49.3% of pts were men. Acute myeloid leukemia (AML) and myelodysplastic syndrome were the most common primary malignancies (28.2% each). Most pts (80.3%) received peripheral blood stem cells; 18.3% received bone marrow, and 1.4% received cord blood as the stem cell source. Treatment was ongoing in 17 pts (23.9%) at data cutoff. At baseline, 23 pts (32.4%) had grade II aGVHD, 34 (47.9%) had grade III, and 14 (19.7%) had grade IV; 36 pts (50.7%) had ≥2 organs involved. Before starting RUX, 19 pts (26.8%) had progressive aGVHD after 3 days of CS treatment, 30 (42.3%) had no response after 7 days of CS, 8 (11.3%) developed new organ involvement on CS <2 mg/kg, and 14 (19.7%) were taper intolerant. At Day 28, ORR (95% CI) was 54.9% (42.7%-66.8%) with responses observed irrespective of grade or SR criteria (Table 1). Median DOR among Day 28 responders has not been reached (lower limit, 159 days; Figure 1). Event-free probability estimates (95% CI) for Day 28 responders at 3 and 6 months were 79.0% (62.3%-88.9%) and 67.0% (47.3%-80.7%), respectively. Best ORR at any time was 73.2% (CR, 56.3%). Median (range) time to response was 7.0 (6-49) days. Two pts had malignancy relapse (AML in both). At Day 28, 43 pts were on RUX and CS treatment; 55.8% (24/43) of these pts had a 50% reduction from baseline in CS dose (Figure 2). Most pts (69/71) initiated RUX at 5 mg BID. At Day 28, 46.5% of pts (20/43) received RUX 10 mg BID. The most common treatment-emergent adverse events (TEAEs; any grade, grade 3/4) were anemia (60.6%, 46.5%), hypokalemia (47.9%, 18.3%), decreased platelet count (43.7%, 38.1%), peripheral edema (43.7%, 11.3%), and decreased neutrophil count (36.6%, 31.0%). Cytomegalovirus (CMV) infection, viremia, and chorioretinitis occurred in 9 (12.7%), 4 (5.6%), and 1 (1.4%) pts, respectively (43.7% of pts were CMV+ at baseline). Fatal treatment-related TEAEs were sepsis and pulmonary hemorrhage (1 pt each) and were attributed to both RUX and CS.

Conclusion:

In this first prospective trial of RUX in pts with SR aGVHD, RUX treatment resulted in overall responses in 54.9% of pts with SR aGVHD by Day 28, many of whom (68%) had grade III/IV disease at baseline. Best ORR at any time was 73.2% (CR, 56.3%). Responses were rapid and durable. Most pts achieved sustained reductions in CS dose. The AE profile was consistent with expectations for RUX and pts with SR aGVHD. RUX represents a promising therapeutic strategy; a phase 3 trial of RUX vs best available therapy in SR aGVHD is underway.

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