Special Bulletin - October 5th, 2007

DSMB STEPs in
On September 21, Merck and the National Institute of Allergy and Infectious Diseases (NIAID) announced that a Phase IIb clinical trial of MRKAd5, an adenovirus serotype 5 (Ad5)-based AIDS vaccine candidate developed by the company to induce cellular immune responses against HIV, failed to show any effect. Immunizations in the so-called STEP trial were discontinued because the vaccine did not lower the infection rates or the viral loads in the vaccine group compared with the placebo group. Immunizations in another trial, known as Phambili, which was testing the same vaccine in South Africa, were also suspended.

What next?
As data analysis for the STEP trial gets underway, some other trials are placed in a temporary holding pattern

Analyze this
Disappointment dominated the responses to the halting of immunizations in the STEP trial, but many agree it could hold important lessons for future vaccine strategies

Getting it right early
How will the ineffectiveness of the MRKAd5 vaccine candidate affect future preclinical and early clinical development?