Special Considerations for Paxlovid Treatment Among Transplant Recipients With SARS-CoV-2 Infection

(SARS-CoV-2) pandemic has been historic in terms of the number of lives tragically affected and the huge toll of morbidity and mortality.1 During the pandemic's first year there were many drugs employed and formally studied, with at best modest clinical benefits.2 In mid-2021, results of studies with 2 new drugs brought substantial new hope. Merck and Ridgeback Biotherapeutics' drug, molnupiravir, was reported to reduce death and hospitalization from coronavirus disease 2019 (COVID-19) by 30%.3 Soon after this, Pfizer reported impressive results for its drug, Paxlovid. In this report we will discuss the latter drug and why, despite its great efficacy, it may pose a major safety risk to transplant patients and others treated with calcineurin inhibitors (CNIs) or mTOR (mammalian target of rapamycin) inhibitors. Paxlovid is a combination of 2 oral drugs. The first, nirmatrelvir (PF-07321332), is a newly developed agent that blocks the SARS-CoV-2 3CL protease, which is navir, which is used only to slow nirmatrelvir meta