Evaluation of Immune Response (gpELISA) as the Principal Surrogate Endpoint for Protection of Herpes Zoster Afforded by Zostavax

• Activity Number: 474
• Type: Contributed
• Date/Time: Wednesday, August 3, 2011 : 8:30 AM to 10:20 AM
• Sponsor: Biopharmaceutical Section
• Author(s): Xiaoming Li*+ and Xiaopeng Miao and Ivan S. F. Chan
• Companies: Merck Research Laboratories and Boston University and Merck Research Laboratories
• Keywords: Surrogate Endpoint ; Statistical Surrogacy ; Principle Surrogacy ; Vaccine Trial

Abstract

Use of surrogate endpoints in clinical trials can shorten and hence make drug development more cost-effective. Validating a surrogate for a clinical endpoint is critical in this context. The most commonly used approach to validate a surrogate endpoint is to demonstrate 'statistical surrogacy', based on the four criteria by Prentice (1989). A more recently proposed approach is 'principle surrogacy', by Frangakis and Rubin (2002) and Gilbert and Hudgens (2008). In the herpes zoster (HZ) vaccine (ZOSTAVAX) efficacy trials, the primary endpoint is the incidence of HZ. The antibody response, as measured by gpELISA post-vaccination, has been established as an immune correlate of protection based on these efficacy trials, using the approach of statistical surrogate. In this work, the 'principle surrogacy' of gpELISA will be evaluated, together with its 'statistical surrogacy'.