Merck & Co., Inc. announced their candidate AIDS vaccine failed to provide protection in a human study designed to test for efficacy. In this Merck trial involving high risk volunteers, an equal number of people received either placebo or AIDS vaccine. The independent Data Safety Monitoring Board recommended that the trial be stopped because it was not reaching its efficacy endpoints.
Merck has stopped further vaccinations but will continue to follow volunteers in the trial. The Merck trial was being carried out in conjunction with the HIV Vaccine Trials Network (HVTN), a prestigious trial network funded by the US National Institutes of Health.
Don Hildebrand, GeoVax’s President and CEO, commented, “We, along with the rest of the scientific community, are disappointed in the clinical failure of Merck’s HIV vaccine trial. We all share the same goal of finding a safe and effective vaccine to address the devastation of the HIV/AIDS epidemic. We, however, would like to take this opportunity to highlight important differences between our vaccine technology and the technology used in the Merck trial.”
GeoVax AIDS vaccines advancing in human trials represent a significantly different vaccine approach, vaccine composition and results to date than the Merck vaccine.
1) Prototypes for the GeoVax vaccines were selected from a series of trials in non-human primates for their ability to protect against the development of AIDS when vaccinated individuals were administered an AIDS causing virus. At each major step along the development pathway, GeoVax vaccines providing the best protection against AIDS were moved forward.
2) GeoVax AIDS vaccines demonstrated excellent protective results in non- human primate models, much better protective results than reported for Merck’s vaccine in similar models. GeoVax AIDS vaccines protected 22/23 non-human primates for over 3 1/2 years and 5/6 non-vaccinated controls died of AIDS post-AIDS virus infection.
3) GeoVax AIDS vaccines are designed to elicit protective antibodies (Ab) as well as protective T cells (white blood cells) against the AIDS virus. The Merck vaccine stimulates only T cells for providing protection and does not include the Env protein of HIV which is the target for protective antibody (Ab).
4) Protective Ab has been difficult to elicit with HIV/AIDS vaccines. GeoVax has approached this challenge by vaccinating with the natural form of Env (HIV envelope antigens) under conditions that elicit tightly binding Ab. GeoVax studies in non-human primates clearly show this Ab correlates with protection.
5) GeoVax vaccines use an attenuated smallpox vaccine to provide pulses of HIV proteins (antigen) to stimulate protective anti-AIDS vaccine responses. Pulses of antigen from the GeoVax vaccines elicit T cell responses that rapidly mobilize and then contract into a state called “central memory” from which they rapidly expand to fight the appearance of HIV.
Merck’s vaccines use adenovirus instead of poxvirus vectors. Adenovirus vectors provide more prolonged AIDS virus antigen exposure than the GeoVax poxvirus vectors. Prolonged antigen exposure affects the state of elicited T cells and can compromise the ability to rapidly expand in the fight against an infection.
“The Merck study highlights the importance of clinical trials in vaccine development,” said Dr. Harriet Robinson, Chief Scientific Advisor for GeoVax. “The volunteers who participate in these trials are Heroes of Vaccine Development and make it possible for products that are safe and effective to be identified and licensed for human use. GeoVax salutes the volunteers who participated in the Merck trials and the volunteers that are participating in the GeoVax trials. These are people who care and have volunteered for the greater good of humanity.”
GeoVax AIDS vaccines are being prepared to enter Phase 2 human trials. These large trials will expand the safety and positive immune response data demonstrated in the five (5) prior GeoVax AIDS vaccine trial groups. These trials will be conducted in collaboration with the HIV Vaccine Trials Network.
On the basis of non-human primate studies, GeoVax believes its vaccines will be safe and protective. A rigorously conducted clinical trial in human volunteers will be accomplished to confirm effectiveness in preventing AIDS. With 14,000 new HIV/AIDS infections reported daily and more than 60 million people living with HIV/AIDS worldwide, the need for an effective HIV/AIDS vaccine is extremely urgent.