A155 - Efficacy and Safety of a Novel Two-Dose Regimen of Xenopax for Acute Rejection Prophylaxis in Kidney Transplantation

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Author Block: T. Zhu, Renal Transplant Department, Zhongshan Hospital, Fudan University, Shanghai, China
*Purpose: Xenopax, a high-affinity antibody against the interleukin-2 receptor, was evaluated in a two-dose regimen to optimize rejection prophylaxis after kidney transplantation.
*Methods: This was a multicenter, single-arm, open-label study. Eligible first-time kidney transplant recipients, who were enrolled across 12 hospitals between August 9, 2022 and May 22, 2024, received xenopax intravenously at a dose of 1 mg/kg within 24 h prior to transplantation (first dose) and again on post-transplant day 8 (second dose). All patients received standard maintenance triple immunosuppressive therapy. The primary endpoint was 3- and 6-month post-transplant AR incidence.
Figure 1. Study design (A) and participant enrollment flowchart (B)
*Results: Of 101 enrolled patients, one withdrew. Consequently, 100 were included in the full analysis set (FAS)/safety set (SS), 92 were included in the per-protocol set (PPS). In the FAS, the incidence of AR was 3.0% at both 3 and 6 months (95% CI: 1.0%-8.5%). In the PPS, the incidence was 2.2% at both time points (95% CI: 0.6%-7.6%). Eleven patients (11%) had 13 infections (onset: 34-147 days), with a median time to first infection of 85 days. Seven-month patient survival was 99.0% (95% CI: 97.0%-100.0%) and graft survival was 100%. Six patients (6.0%) had delayed graft function (DGF). Serum IL-2R levels declined by post-transplant day 8 (second dose), then rose at 1 month and 3 months. SCr levels fell postoperatively compared to baseline. Adverse events (AEs) occurred in 64 patients (64%) with 225 events. Nineteen patients (19%) had drug-related AEs with 62 events, of which 4 patients were considered serious AEs.
Figure 2. Temporal changes in serum IL-2R (A) and SCr levels (B) in FAS
*Conclusions: This Xenopax regimen showed favorable efficacy and tolerability for AR prevention in kidney transplant recipients.