Successful Management of Severe COVID-19 in a Kidney Transplant Recipient Safe Co-Administered Tacrolimus and Ensitrelvir: A Case Report

Background and Clinical Significance: COVID-19 may worsen in patients receiving immunosuppressants. Furthermore, drug–drug interactions and concomitant use of anti-inflammatory drugs complicate treatment. We report the clinical course of severe COVID-19 pneumonia in a 74-year-old Japanese male kidney transplant recipient. Case Presentation: The patient had been taking tacrolimus (TAC) (2.5 mg/day), mycophenolate mofetil (1000 mg/day), and prednisone (5 mg/day) since his kidney transplant 7 years earlier. Twenty days before admission, he tested positive for SARS-CoV-2 antigen and was administered molnupiravir for 5 days. At admission, real-time PCR testing of a nasopharyngeal specimen revealed high viral loads, with Ct values of 22.2 and 27.9 for the E and N2 genes, respectively. An oxygen flow rate of 15 L/min was required to maintain arterial oxygen saturation above 90%. TAC was continued, and antibiotics, steroids, anti-interleukin-6 receptor antibodies, intravenous immunoglobulin, and ensitrelvir (ESV) were administered. With invasive positive-pressure ventilation, positive end-expiratory pressure (PEEP), and prone positioning, the arterial oxygen tension/inspired oxygen tension (P/F) improved from 61.3 to 386 within 7 h. The patient was extubated 30 h after admission. The TAC dose was adjusted from 2.5 mg/day to 1 mg/day to achieve the target trough level. The patient was discharged on hospital day 8. PCR testing at discharge showed a decrease in viral load. Conclusions: This study provides insights into the treatment of COVID-19 in patients receiving immunosuppressants. Combination therapy of ESV and TAC was feasible in kidney transplant recipients with dose adjustment. The use of other anti-inflammatory drugs should also be considered.