Conversion from calcineurin inhibitors to belatacept in HLA- sensitized kidney-transplant recipients with low-level donor specific antibodies.

Background. Belatacept could be the treatment of choice in renal-transplant recipients with renal dysfunction attributed to CNI nephrotoxicity. Few studies have described its use in patients with DSA. Methods. We retrospectively evaluated conversion from CNIs to belatacept in 29 HLA-immunized RTRs. Data regarding acute rejection, DSA and renal function were collected. These patients were compared to 42 non-immunized patients treated with belatacept. Results. Patients were converted from CNIs to belatacept a median of 444 days [IQR:85-1200] after transplantation and were followed-up after belatacept conversion, for a median of 308 days [IQR: 125-511]. At conversion, 16 patients had DSA. Nineteen DSA were observed in these 16 patients, of which 11/19 were less than 1000MFI, 7/19 were between 1000 and 3000 MFI , and one was more than 3000 MFI. At last follow-up, pre-existing DSA had decreased or stabilized. Seven patients still had DSA with a mean MFI of 1298 ± 930 at the last follow-up. No patient developed a de novo DSA in the DSA positive group. In the non-immunized group, one patient developed de novo DSA (A24- MFI 970; biopsy for cause did not show BPAR or microinflammation score). After belatacept conversion, one ABMR was diagnosed. The mean eGFR improved from 31.7 ± 14.2 mL/min/1.73 m2 to 40.7 ± 12.3 mL/min/1.73 m2 (p

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