Hepatitis C Direct-Acting Antivirals in the Immunosuppressed Host: Mechanisms, Interactions, and Clinical Outcomes.

Direct-acting antivirals (DAAs) have transformed hepatitis C virus (HCV) management, offering high cure rates, favorable safety, and simplified regimens. Management in immunosuppressed patients remains challenging due to drug-drug interactions (DDIs). The objective of this review is to summarize clinical outcomes, safety, and pharmacologic considerations of DAA therapy in immunosuppressed patients, including solid organ transplant recipients and those on biological agents. We reviewed clinical studies, pharmacologic databases, and guidelines to characterize DAA classes, mechanisms, and relevant DDIs in immunosuppressed HCV patients. In transplant recipients, DAAs achieved sustained virological response (SVR) > 90% with minimal graft rejection. Safety profiles were favorable, and immunosuppressant dose adjustments were rarely needed. DDIs, particularly with calcineurin inhibitors (tacrolimus, cyclosporine), require careful monitoring due to variable trough-level effects. Evidence also supports the efficacy and safety of DAAs in patients on biological agents, without compromising SVR. Pharmacokinetic data indicate DAAs maintain antiviral activity across HCV genotypes in the presence of immunosuppressants, though mTOR inhibitors may alter efficacy in certain HCV genotypes. DAAs are highly effective and safe in immunosuppressed patients, achieving high SVR rates and potential graft survival benefits. Prospective studies are needed to assess DAA therapy in patients receiving biological agents and to optimize co-administration strategies with immunosuppressive agents.