Theme: Clinical Research Year: 2019
Background: High efficacy was observed in CO-STAR part A, a phase 3 trial of EBR/GZR for 12 weeks in
participants on opioid agonist therapy (OAT). CO-STAR part B is the ongoing 3-year observational study
in participants who received ≥1 dose of EBR/GZR in part A. We provide final results from the 3-year
follow-up phase, which includes reinfection rates, urine drug screen (UDS) results, and reported drug
use.
Methods: UDS 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 was detected, viral
genotype and sequencing were assessed.
Results: 199 participants enrolled in part B. Overall from the end of treatment through 3 years of followup, HCV recurrence consistent with reinfection was observed in 10/286 participants, with a rate of 1.7
reinfections/100 person-years (95% CI: 0.79, 3.0). Six participants were found to have reinfection in part
A, and 5 reinfections were identified in part B (enrollment, 6M, 18M, 24M, 30M), with 1 participant
from part A having a second reinfection in part B. During part B, the percentage of participants with
positive UDS results (excludes cannabinoids, methadone, buprenorphine) remained relatively constant,
with positive results in 67%, 56%, 51%, 45%, 43%, 46%, and 45% at part B day 1, 6M, 12M, 18M, 24M,
30M, and 36M, respectively. Similarly, participant-reported injection drug use within the month prior to
each visit was 15%, 19%, 17%, 15%, 16%, and 18% at 6M, 12M, 18M, 24M, 30M, and 36M, respectively.
Conclusion: Rates of drug use remained comparable from the start of treatment through the 3-year
follow-up. Final data from this trial in participants on OAT demonstrate that HCV reinfection following
EBR/GZR therapy is uncommon, despite ongoing drug use. Additional data including specific risk
behaviors will be reported.
Disclosure of Interest Statement:
Jason Grebely has served on advisory committees or review panels for AbbVie, Gilead, and Merck/MSD;
received grant/ research support from AbbVie, Cepheid, Gilead, and Merck/MSD; and has conducted
speaking and teaching activities for Cepheid, Gilead, and Merck/MSD. Brian Conway has served on
advisory committees or review panels for AbbVie, Gilead, and Merck; has received grant/research
support from AbbVie, Gilead, and Merck; and has conducted speaking and teaching activities for AbbVie,
Gilead, and Merck. Alain Harris Litwin has served on advisory committees or review panels and received
grant research support for Gilead Sciences and Merck. Olav Dalgard has served on advisory committees
or review panels for MSD, Janssen Cilag, Medivir, Gilead, and Abbvie; and has received grant/research
support from MSD, Medivir, Gilead, and Abbvie. Oren Shibolet has served on advisory committees or
review panels for and received grant/research support from Merck and AbbVie; and has provided
consultancy for Gilead. Ronald Nahass has received grant/research support from Merck, Gilead, ViiV,
and Janssen, and has served on advisory committees and review panels for Assembly Bio. Frederick
Altice has served on advisory committees or review panels for Merck and Gilead; has received
grant/research support from Merck and the National Institutes of Health; and has delivered speaking
and teaching activities for Gilead, BMS, Clinical Care Options, and Simply Speaking. Edward J. Gane has
conducted speaking and teaching activities for Gilead and Janssen; and has served on advisory
committees or review panels for Janssen and Roche. Anne Luetkemeyer has received grant/research
support from Merck, Proteus, and AbbVie. David M. Iser has served on advisory committees or review
panels for AbbVie, and has provided speaking teaching services for AbbVie, BMS, Gilead Sciences, and
MSD. Isaias Noel Gendrano, Michelle M. Kelly, Peggy Hwang, Eliav Barr, Michael Newton Robertson, and
Heather Platt are employees of Merck, Sharp & Dohme, a subsidiary of Merck & Co., Inc., Kenilworth, NJ,
USA, and hold stock in Merck & Co., Inc., Kenilworth, NJ, USA. Gregory Dore has conducted speaking and
teaching activities for Merck, Gilead Sciences, AbbVie, and Bristol-Myers Squibb. Cheng-Yuan Peng has
nothing to disclose.