# The Role of mTOR Inhibitors in COVID-19 Outcomes Among Heart Transplant Recipients

## TL;DR

This study found that mTOR inhibitors, especially when used without CNIs, may offer protective effects against severe outcomes in heart transplant recipients with COVID-19.

## Contribution

The study provides new evidence on the potential protective role of CNI-free mTOR-based immunosuppression in reducing severe COVID-19 outcomes in heart transplant patients.

## Key findings

- mTOR users had higher all-cause mortality, but no COVID-19-related deaths occurred in the CNI-free mTOR group.
- mTOR-based immunosuppression was non-inferior to standard therapy for general COVID-19 outcomes.
- The mTOR+CNI subgroup had higher mortality compared to non-mTOR regimens.

## Abstract

Background: Heart failure (HF) remains a major global health challenge, with orthotopic heart transplantation (OHT) serving as the gold-standard therapy for end-stage disease. Chronic immunosuppression required to prevent graft rejection increases the risk of infections and malignancies. The COVID-19 pandemic underscored the particular vulnerability of transplant recipients to severe SARS-CoV-2 infection. Specific immunosuppressive agents used in OHT patients may differentially affect SARS-CoV-2 infection. In particular, mTOR inhibitors may modulate viral replication and immune responses, potentially influencing disease severity. Objectives: This study evaluated the impact of immunosuppressive regimens—particularly mTOR inhibitors—on COVID-19 outcomes in heart transplant recipients, comparing mTOR-based therapy (with or without calcineurin inhibitors, CNIs) to non-mTOR-based regimens. Methods: This single-center retrospective observational study included 556 orthotopic heart transplant recipients (76.3% male; median age, 58 years) followed from March 2020 to March 2024. To compare patients receiving mTOR inhibitors with similar non-mTOR recipients, 3:1 propensity score matching was performed based on age, sex, and body mass index. Among the study population, 88 patients (15.8%) received mTOR inhibitors (everolimus or sirolimus), of whom 66 were concomitantly treated with calcineurin inhibitors and 22 without. Data were obtained from the National Health Fund database and clinical follow-ups. Results: Overall mortality was 13.5%, and COVID-19-related mortality 3.2%. COVID-19 incidence was 33% in the mTOR group versus 36.7% in the non-mTOR group (p = 0.52). Hospitalization rates were 3.4% and 6.4% (p = 0.29), respectively. All-cause mortality was higher among mTOR users (21.6% vs. 11.7%, p = 0.02), especially in the mTOR+CNI subgroup. Notably, no COVID-19-related deaths occurred in the mTOR CNI-free group. Conclusions: mTOR-based immunosuppression was non-inferior to standard therapy for COVID-19 outcomes. The absence of COVID-19-related deaths in patients on mTOR CNI-free regimens suggests potential protective effects that merit further investigation.