OP40 PRA023 Demonstrated Efficacy and Favorable Safety as Induction Therapy for Moderately to Severely Active UC: Phase 2 ARTEMIS-UC Study Results

Abstract Background Tumor necrosis factor-like cytokine 1A (TL1A) is an upstream regulator of pro-inflammatory cytokines and fibrosis signals. PRA023 is an anti-TL1A monoclonal antibody in development for multiple inflammatory/fibrotic diseases using a precision medicine approach with a companion diagnostic (CDx). This Phase 2 placebo-controlled, multi-center, double-blind study aimed to assess the efficacy and safety of PRA023 for induction treatment in adults with moderately to severely active ulcerative colitis (UC). Methods Key eligibility criteria included a modified Mayo Score of 4-9, a centrally read (with adjudication) endoscopy subscore of ≥ 2, a rectal bleeding subscore of ≥ 1, and a history of insufficient response, loss of response, and/or intolerance to conventional and/or advanced (approved biologics and JAK inhibitors/S1P modulators) therapies (≤ 4 advanced agents from ≤ 3 classes). Patients were stratified by prior biologic exposure status (yes/no) and CDx status (yes/no) and randomized 1:1 to placebo or intravenous PRA023 (1000mg on Day 1, 500mg at Weeks 2, 6, and 10). The primary endpoint was clinical remission at week 12. Analyses of all ranked secondary endpoints, the first being endoscopic improvement (endoscopy score of ≤ 1), were multiplicity controlled. Results Of the 135 patients in the full analysis data set, 60/67 (89.6%) in the placebo arm and 68/68 (100%) in the PRA023 arm completed the 12-week Induction Period. Baseline characteristics were similar with minor differences in the proportion of patients with baseline endoscopy score of 3 and prior exposure to ≥ 3 advanced therapies (Table 1). A significantly greater proportion of patients who received PRA023 achieved the primary endpoint of clinical remission (26.5% PRA023 vs. 1.5% placebo, ∆25.0%, p < 0.0001) at Week 12 (Table 2). In addition, substantially more patients who received PRA023 achieved the key secondary endpoint of endoscopic improvement (36.8% PRA023 vs. 6.0% placebo, ∆30.8%, p < 0.0001). All remaining ranked secondary endpoints were met (Table 2). The rates of treatment-emergent adverse events (AEs) were similar between the two arms with no serious AEs or AEs leading to study drug discontinuation in the PRA023 arm (Table 3). There were no safety signals identified from the study. Conclusion PRA023 was effective with favorable tolerability for the induction of clinical remission and endoscopic improvement in moderately to severely active UC. A Phase 3 study will be conducted to confirm these findings. Recruitment is ongoing for the CDx+ expansion cohort of the study to assess the effectiveness of the CDx, designed to select patients with a higher probability of responding to PRA023.

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