"Saving lives with nirmatrelvir/ritonavir one transplant patient at a time".

Background: Solid organ transplant (SOT) recipients are at risk of complications from COVID-19. Nirmatrelvir/ritonavir (Paxlovid) can reduce mortality from COVID-19 but is contraindicated in patients receiving calcineurin inhibitors (CI), which depend on cytochrome p4503A (CY3PA). In this study, we aim to show the feasibility of nirmatrelvir/ritonavir administration to SOT recipients receiving CI with coordination of medication management and limited tacrolimus trough monitoring.

Methods: We reviewed adult SOT recipients treated with nirmatrelvir/ritonavir from 4/14 to 11/1/2022 and assessed for changes in tacrolimus trough and serum creatinine after therapy.

Results: Of 47 patients identified, 28 were receiving tacrolimus and had follow-up laboratory testing. Patients had a mean age of 55 years, 17 (61%) received a kidney transplant and 23 (82%) received three or more doses of SARS-CoV-2 mRNA vaccine. Patients had mild-moderate COVID-19 and started nirmatrelvir/ritonavir within 5 days of symptom onset. Median baseline tacrolimus trough concentration was 5.6 ng/mL (Interquartile range 5.1-6.7), while median follow-up tacrolimus trough concentration was 7.8 ng/mL (Interquartile range 5.7-11.5, p = 0.0017). Median baseline and follow-up serum creatinine levels were 1.21 mg/dL (Interquartile range 1.02-1.39) and 1.21 mg/dL (interquartile range 1.02-1.44, p = 0.3162), respectively. One kidney recipient had a follow up creatinine level >1.5 times baseline. No patients were hospitalized or died from COVID-19 in the follow up period.

Conclusion: While administration of nirmatrelvir/ritonavir resulted in a significant increase in tacrolimus concentration, this did not result in significant nephrotoxicity. Early oral antiviral treatment in SOT recipients is feasible with medication management, even with limited tacrolimus trough monitoring.