Carfilzomib versus rituximab for treatment of de novo donor-specific antibodies in lung transplant recipients

Introduction: De novo donor-specific antibodies (DSAs) increase the risk of chronic lung allograft dysfunction (CLAD) in lung transplant recipients (LTRs). Both carfilzomib (CFZ) and rituximab (RTX) lower the mean fluorescent intensity (MFI) of DSAs, but comparative data are lacking. We compared CLAD-free survival and the degree and duration of DSA depletion after treatment of LTRs with CFZ or RTX. Methods: LTRs that received CFZ or RTX for DSA depletion between 08/01/2015 and 08/31/2020 were included. The primary outcome was CLAD-free survival. Secondary outcomes were change in MFI at corresponding loci within 6 months of treatment (ΔMFI), time to DSA rebound, and change in % predicted FEV₁ 6 months after treatment (ΔFEV₁). Results: Forty-four LTRs were identified, 7 of whom had ≥2 drug events; therefore, 53 drug events were divided into 2 groups, CFZ (n = 17) and RTX (n = 36). Use of plasmapheresis, immunoglobulin, and mycophenolate augmentation was equivalent in both groups. CLAD-free survival with a single RTX event was superior to that after ≥2 drug events (p = 0.001) but comparable to that with a single CFZ event (p = 0.399). Both drugs significantly lowered the MFI at DQ locus, and the median ΔMFI was comparable. Compared to the RTX group, the CFZ group had a shorter median interval to DSA rebound (p = 0.015) and a lower ΔFEV₁ at 6 months (p = 0.014). Conclusion: Although both CFZ and RTX reduced the MFI of circulating DSAs, RTX prolonged the time to DSA rebound. Despite more pronounced improvement in FEV₁ with RTX, comparable CLAD-free survival between the 2 groups suggests that both drugs offer a reasonable treatment strategy for DSAs in LTRs.