Therapeutic Exposure and Successful Response to Pembrolizumab in a Patient With Non-Small-Cell Lung Cancer Despite Significant Renal Loss Due to Paraneoplastic Nephrotic Syndrome

Novel factors potentially initiating acute antibody-mediated rejection in pig kidney xenografts despite an efficient immunosuppressive regimen

Antibody-mediated rejection (AMR) is a common cause of graft failure after pig-to-nonhuman primate organ transplantation, even when the graft is from a pig with multiple genetic modifications. The specific factors that initiate AMR are often uncertain. We report two cases of pig kidney transplantation into immunosuppressed baboons in which we identify novel factors associated with the initiation of AMR. In the first, membranous nephropathy was the initiating factor that was then associated with the apparent loss of the therapeutic anti-CD154 monoclonal antibody in the urine when severe proteinuria was present. This observation suggests that proteinuria may be associated with the loss of any therapeutic monoclonal antibody, for example, anti-CD154 or eculizumab, in the urine, resulting in xenograft rejection. In the second case, the sequence of events and histopathology tentatively suggested that pyelonephritis may have initiated acute-onset AMR. The association of a urinary infection with graft rejection has been well-documented in ABO-incompatible kidney allotransplantation based on the expression of an antigen on the invading microorganism shared with the kidney graft, generating an immune response to the graft. To our knowledge, these potential initiating factors of AMR in pig xenografts have not been highlighted previously.

Proteinuria and Exposure to Eculizumab in Atypical Hemolytic Uremic Syndrome

BACKGROUND

Eculizumab is a monoclonal antibody for the treatment of atypical hemolytic uremic syndrome (aHUS). Kidney damage, a common condition in patients with aHUS, may result in proteinuria. Because proteinuria may affect the pharmacokinetics of therapeutic proteins such as eculizumab, the aim of our study was to investigate the effect of proteinuria on eculizumab pharmacokinetics.

METHODS

This study was an ancillary study of a previously performed pharmacokinetic-pharmacodynamic study of eculizumab in aHUS. Proteinuria, measured as urinary protein-creatinine ratios (UPCR), was investigated as covariate for eculizumab clearance. Thereafter, we evaluated the effect of proteinuria on the exposure to eculizumab in a simulation study for the initial phase and for a 2-weekly and 3-weekly interval in the maintenance phase.

RESULTS

The addition of UPCR as a linear covariate on clearance to our base model resulted in a statistically improved fit ( P < 0.001) and reduction of unexplained variability in clearance. From our data, we predicted that in the initial phase, 16% of the adult patients with severe proteinuria (UPCR >3.1 g/g) will have inadequate complement inhibition (classical pathway activity >10%) on day 7 of treatment, compared with 3% of the adult patients without proteinuria. None of the pediatric patients will have inadequate complement inhibition at day 7 of treatment. For the 2- and 3-weekly dosing intervals, we predicted that, respectively, 18% and 49% of the adult patients and, respectively, 19% and 57% of the pediatric patients with persistent severe proteinuria will have inadequate complement inhibition, compared with, respectively, 2% and 13% of the adult patients and, respectively, 4% and 22% of the pediatric patients without proteinuria.

CONCLUSIONS

Severe proteinuria is associated with a higher risk of underexposure to eculizumab.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

CUREiHUS, Dutch Trial Register, NTR5988/NL5833.