Prospective iterative trial of proteasome inhibitor-based desensitization.

A prospective iterative trial of proteasome inhibitor (PI)-based therapy for reducing HLA antibody (Ab) levels was conducted in five phases differing in bortezomib dosing density and plasmapheresis timing. Phases included 1 or 2 bortezomib cycles (1.3 mg/m(2) × 6-8 doses), one rituximab dose and plasmapheresis. HLA Abs were measured by solid phase and flow cytometry (FCM) assays. Immunodominant Ab (iAb) was defined as highest HLA Ab level. Forty-four patients received 52 desensitization courses (7 patients enrolled in multiple phases): Phase 1 (n = 20), Phase 2 (n = 12), Phase 3 (n = 10), Phase 4 (n = 5), Phase 5 (n = 5). iAb reductions were observed in 38 of 44 (86%) patients and persisted up to 10 months. In Phase 1, a 51.5% iAb reduction was observed at 28 days with bortezomib alone. iAb reductions increased with higher bortezomib dosing densities and included class I, II, and public antigens (HLA DRß3, HLA DRß4 and HLA DRß5). FCM median channel shifts decreased in 11/11 (100%) patients by a mean of 103 ± 54 mean channel shifts (log scale). Nineteen out of 44 patients (43.2%) were transplanted with low acute rejection rates (18.8%) and de novo DSA formation (12.5%). In conclusion, PI-based desensitization consistently and durably reduces HLA Ab levels providing an alternative to intravenous immune globulin-based desensitization.

Randomized controlled pilot study of B cell-targeted induction therapy in HLA sensitized kidney transplant recipients.

Optimal induction regimens for patients at high risk for antibody and/or cell-mediated rejection have not been established. This pilot, prospective, randomized study evaluated addition of B cell/plasma cell-targeting agents to T cell-based induction with rabbit antithymocyte globulin (rATG) in high immunologic risk renal transplant recipients. Patients were randomized to induction with rATG, rATG + rituximab, rATG + bortezomib or rATG + rituximab + bortezomib. Inclusion criteria were: (1) current cytotoxic panel reactive antibody (PRA) ≥20% or peak cytotoxic PRA ≥50% or (2) T or B cell positive flow crossmatch with donor-specific antibody (DSA) or (3) historical positive serologic or cytotoxic crossmatch or DSA to donor or (4) prior allograft loss with more than one acute rejection. Median overall follow-up was 496 days: 1-year and overall acute rejection were 25% and 27.5%, and 25% of patients developed de novo DSA within 1 year. One-year and overall patient survival were 97.5% and 92.5%, and 1-year and overall death-censored allograft survival were 97.5% and 95%. Renal allograft function posttransplant was similar among all arms. Eight of nine cases of peripheral neuropathy were mild, whereas one case was moderate and required a narcotic prescription. In conclusion, addition of rituximab and/or bortezomib to rATG induction has an acceptable safety/toxicity profile in a high immunologic risk renal transplant population.