Background: Currently used direct-acting antivirals (DAA) share pharmacokinetic pathways with many comedications commonly used in patients with chronic hepatitis C virus (HCV) infection, therefore drug-drug interactions (DDI) might exist. Although extensive (DDI) verification is recommended by most clinical practice guidelines, real-world studies have shown that approximately one-tenth of patients on DAA therapy also take concomitant medication with the potential for significant interactions. Despite the risk of significant DDI when patients are administered DAA and a concomitant medication, to date, there is very little information on whether these interactions translate into changes in the toxicity or efficacy of any involved DAA or comedication in clinical practice. Clarifying this issue is a critical point, as the DDI profile of the currently used DAA is not the same, with SOF/VEL showing a lower risk of significant DDI than GLE/PIB. Thus the objective of this study is to compare the percentage of comedication switch, withdrawal, or dose reduction at treatment initiation and during treatment with GLE/PIB or SOF/VEL.

Methods: The patients will be enrolled from the GEHEP 001/HEPAVIR cohort. "The HEPAVIR-DAA cohort (NCT02057003)", includes HIV/HCV-coinfected patients, and "the GEHEP-MONO cohort (NCT02333292)", that includes HCV mono-infected individuals, are ongoing prospective multicenter cohorts of patients receiving DAA combinations prescribed in clinical practice, outside clinical trials. Main Study End Point will be the frequency of comedication switch, withdrawal or dose reduction at treatment initiation (index date) and during treatment with GLE/PIB or SOF/VEL.

Inclusion Criteria:

1. Treatment naive patients who received therapy with GLE/PIB or SOF/VEL between April 1st, 2018, and July 1st, 2023, receiving ≥ 1 comedication or recreational drug.
2. Attended in a hospital with electronic clinical records allowing access to all clinical visits and prescribed medications, both in all hospitals and in primary care institutions of the corresponding Spanish region during the study period.

Exclusion Criteria:

Patients who meet any of the following criteria will be excluded from the study:

1. HCV treatment-experienced patients will be excluded.
2. Patients without any comedication or recreational drug use
3. Those who have attended private health care

The patients will be enrolled from the GEHEP 001/HEPAVIR cohort. "The HEPAVIR-DAA cohort (NCT02057003)", includes HIV/HCV-coinfected patients, and "the GEHEP-MONO cohort (NCT02333292)", that includes HCV mono-infected individuals, are ongoing prospective multicenter cohorts of patients receiving DAA combinations prescribed in clinical practice, outside clinical trials.