Proteasome Inhibitor Carfilzomib‐Based Therapy for Antibody‐Mediated Rejection of the Pulmonary Allograft: Use and Short‐Term Findings

We present this observational study of lung transplant recipients (LTR) treated with carfilzomib (CFZ)‐based therapy for antibody‐mediated rejection (AMR) of the lung. Patients were considered responders to CFZ if complement‐1q (C1q)‐fixing ability of their immunodominant (ID) donor‐specific anti‐human leukocyte antibody (DSA) was suppressed after treatment. Treatment consisted of CFZ plus plasma exchange and immunoglobulins. Fourteen LTRs underwent CFZ for 20 ID DSA AMR. Ten (71.4%) of LTRs responded to CFZ. DSA IgG mean fluorescence intensity (MFI) fell from 7664 (IQR 3230–11 874) to 1878 (653–7791) after therapy (p = 0.001) and to 1400 (850–8287) 2 weeks later (p = 0.001). DSA C1q MFI fell from 3596 (IQR 714–14 405) to <30 after therapy (p = 0.01) and <30 2 weeks later (p = 0.02). Forced expiratory volume in 1s ( FEV₁) fell from mean 2.11 L pre‐AMR to 1.92 L at AMR (p = 0.04). FEV₁ was unchanged after CFZ (1.91 L) and subsequently rose to a maximum of 2.13 L (p = 0.01). Mean forced expiratory flow during mid forced vital capacity (25–75) (FEF_25–75) fell from mean 2.5 L pre‐AMR to 1.95 L at AMR (p = 0.01). FEF_25–75 rose after CFZ to 2.54 L and reached a maximum of 2.91 L (p = 0.01). Responders had less chronic lung allograft dysfunction or progression versus nonresponders (25% vs. 83%, p = 0.04). No deaths occurred within 120 days and 7 patients died post CFZ therapy of allograft failure. Larger prospective interventional studies are needed to further describe the benefit of CFZ‐based therapy for pulmonary AMR.