Theme: Clinical Research Year: 2018
High efficacy was observed in C-EDGE CO-STAR Part A, a phase 3 trial of EBR/GZR for 12
weeks in participants on OAT. CO-STAR Part B is the ongoing 3-year observational study of
participants who received ≥1 dose of EBR/GZR in Part A (n=296). We provide analyses of urine
drug screen (UDS) results, reported drug use, and a summary of reinfection in Part B.
UDS (amphetamines, barbiturates, benzodiazepines, buprenorphine, cannabinoids, cocaine,
methadone, opiates, phencyclidine, or propoxyphene) was performed at each visit in Parts A
and B; additionally in Part B, patient-reported surveys were administered at each 6-month visit
to assess risk behavior. If HCV RNA is detected at any visit, viral genotype and sequencing are
Drug use has remained constant in participants enrolled in Part B (n=199). Percentage of
participants with a positive UDS (excludes cannabinoids, methadone, buprenorphine) remained
relatively constant, with 48%, 48%, 54%, 49%, 46%, 47%, 39%, 36%, and 43% positive at day
1, treatment week (TW)12, follow-up week (FW)12, FW24, and months 6, 12, 18, 24, and 30,
respectively. Similarly, reported drug use within the last month prior to each visit was
comparable, with any-drug use reported by 50%, 47%, 48%, 45%, and 44%, at months 6, 12,
18, 24, and 30, respectively. HCV viral recurrence consistent with reinfection occurred in 6/296
participants through FW24, with a rate of 3.4 reinfections/100 person-years (95% confidence
interval, 1.3–7.5); an additional 5 viral recurrences were identified in Part B (enrollment, months
6, 18, 24, 30).
Drug use as assessed by UDS and patient report has remained comparable from the start of
treatment throughout the ongoing 3-year follow-up period. HCV reinfection among patients on
OAT following EBR/GZR therapy is uncommon, despite ongoing drug use. Additional follow-up
data including specific risk behaviors will be reported.
This study was funded by Merck & Co., Inc., Kenilworth, NJ, USA. Dr Dore received funding
from Merck & Co., Inc., as an investigator on this study.