483. Pharmacokinetics of Nirmatrelvir and Ritonavir in COVID-19 Patients with Hemodialysis

Abstract Background Nirmatrelvir/ritonavir (Paxlovid) is one of the few therapeutic options for COVID-19. It is not recommended to use in patients with end-stage renal disease (ESDR), and large-scale clinical trials are needed to support its application in this population. We investigated the pharmacokinetics of nirmatrelvir/ritonavir (150 mg/100 mg twice a day) in COVID-19 patients with hemodialysis (HD). Methods SARS-Cov-2 tested positive patients with HD were included and given treatment with nirmatrelvir/ritonavir (150 mg/100 mg twice a day) for 5 days. For most patients, a 4 h-HD started 2 h after the morning dose on day 2. Blood samples were collected 4 h and 12 h after the first dose on day 1 to obtain peak and trough concentrations, respectively. And the blood samples at the start and finish time points of HD were drawn to observe the effect of dialysis on drug clearance. A tandem mass spectrometry (LC-MS/MS) method was conducted to quantify the nirmatrelvir and ritonavir concentrations. Results A total of 14 COVID-19 patients undergoing dialysis were enrolled, with 4 females and 10 males. The age was 66.6 ± 8.0 years and the body mass index (BMI) was 22.3 ± 3.5. The peak concentration of nirmatrelvir after the first dose was 4960 ± 1889 ng/mL. And the trough concentration was 2940 ± 1305 ng/mL, which was approximately 10 times above the EC90 (292 ng/mL). Nirmatrelvir concentration fell by 42% from 10426 ± 3191 ng/mL to 6035 ± 2402 ng/mL during 4 h-HD. The peak and trough concentrations of ritonavir were 816 ± 445 ng/mL and 326±201 ng/mL after the first dose, respectively. And the concentration fell by 17% during 4 h-HD. Based on the assumption of a first-order elimination kinetic, nirmatrelvir/ritonavir 150 mg/100 mg, once a day dose regimen was simulated which showed that the plasma concentration of nirmatrelvir could also achieve the target EC90 value.Figure 1.Plasma concentration of nirmatrelvir (blue circles) and ritonavir (orange circles) in COVID-19 patients with hemodialysis during the course of 150 mg/100 mg twice a day treatment. 4 h- hemodialysis was performed at 26 - 30 h after the first dose. Data are presented as the mean ± standard deviation. The open circles indicate the individual concentration data.Figure 2.Simulated plasma concentration data in dialysis patients following a single dose of 150 mg/100 mg nirmatrelvir/ritonavir. Long dashed line represents patients not on dialysis. Short dashed line represents patients receiving a 4 h - dialysis. Conclusion 150 mg/100 mg twice a day dose regimen of nirmatrelvir/ritonavir produced sufficient concentrations to reach the effective target in COVID-19 patients with HD. Simulation data suggested that a modified dose with 150 mg/100 mg once a day could also reach effective concentration. Our data provide evidence for the application of nirmatrelvir/ritonavir in patients with ESRD and further validation in large-scale investigation was needed. Disclosures All Authors: No reported disclosures