Optimal hepatitis C treatment adherence patterns and sustained virologic response among people who inject drugs: The HERO study

Background & Aims: Direct-acting antivirals (DAAs) are highly effective for treating HCV infection even among people who inject drugs (PWID). Yet, little is known about patients' adherence patterns and their association with sustained virologic response (SVR) rates. We aimed to summarize various adherence patterns and determine their associations with SVR. Methods: Electronic blister packs were used to measure daily adherence to once-a-day sofosbuvir/velpatasvir during the 12-week treatment period among active PWIDs. Blister pack data were available for 496 participants who initiated DAAs for whom SVR status was known. Adherence was summarized in multiple patterns, such as total adherent days, consecutive missed days, and early discontinuations. Thresholds for adherence patterns associated with >90% SVR rates were also determined. Results: The overall SVR rate was 92.7%, with a median adherence rate of 75%. All adherence patterns indicating greater adherence were significantly associated with achieving SVR. Participant groups with ≥50% (>42/84) adherent days or <26 consecutive missed days achieved an SVR rate of >90%. Greater total adherent days during 9-12 weeks and no early discontinuation were significantly associated with higher SVR rates only in those with <50% adherence. Participants with first month discontinuation and ≥2 weeks of treatment interruption had low SVR rates, 25% and 85%, respectively. However, greater adherent days were significantly associated with SVR (adjusted odds ratio 1.10; 95% CI 1.04–1.16; p <0.001) even among participants with ≥14 consecutive missed days. Conclusions: High SVR rates can be achieved in the PWID population despite suboptimal adherence. Encouraging patients to take as much medication as possible, with <2 weeks consecutive missed days and without early discontinuation, was found to be important for achieving SVR. Impact and implications: People who inject drugs can be cured of HCV in >90% of cases, even with relatively low adherence to direct-acting antivirals, but early discontinuations and long treatment interruptions can significantly reduce the likelihood of achieving cure. Clinicians should encourage people who inject drugs who are living with HCV to adhere daily to direct-acting antivirals as consistently as possible, but if any days are interrupted, to continue and complete treatment. These results from the HERO study are important for patients living with HCV, clinicians, experts writing clinical guidelines, and payers. Clinical Trial Number: NCT02824640.