VaxGen Inc.'s investigational vaccine for the prevention of HIV infection failed to hit primary or secondary endpoints in a Phase III trial conducted in Thailand.
As the poor results were anticipated, VaxGen's stock (NASDAQ:VXGN) took the news fairly well, dropping 46 cents Wednesday to close at $9.39.
The results released are preliminary, yet powerful, because they confirm that AidsVax is ineffective in preventing HIV infection.
Back in February, VaxGen's stock dropped 47.3 percent, or $6.16, to close at $6.86 on news that a larger Phase III conducted in North America, Puerto Rico, the Netherlands and Canada failed to hit its primary endpoint - a statistically significant reduction of HIV infection within the study population as a whole. (See BioWorld Today, Feb. 25, 2003.)
"Following the results announced in February, failure of the Thailand trial was widely anticipated," Sharon Seiler, vice president, senior biotech analyst at Punk, Ziegel & Co. in New York, told BioWorld Today. "Although the trials worked differently, there really was no reason to expect that results would be very different from each other."
Seiler said that even before releasing the February data, VaxGen proactively diversified, "and most investors I speak with own the stock for future programs." Those programs include research and development in the anthrax and smallpox arenas.
Indeed, Kesinee Yip, associate director of corporate communications for VaxGen Inc., in Brisbane, Calif., told BioWorld Today that, after releasing poor data in February, the company "heard a loud and clear signal from the market that [investors] were not interested in having VaxGen pursue these HIV programs with investor money. Any further research in this area would need to be funded by the government or philanthropic organizations."
Analysis Of Both Phase III Trials Continue
It's difficult to pinpoint what went wrong with AidsVax, since investigators continue to study the data. The vaccine is made of a recombinant form of the gp120 protein on the surface of HIV and is produced in mammalian cell culture.
Yip didn't have a specific date as to when final results of the Thailand trial would be completed. She said the randomized, double-blind, placebo-controlled trial was designed to evaluate AidsVax B/E in 2,500 volunteers who were injectable drug users. AidsVax B/E was a candidate against blood-borne transmission of HIV subtype E and one strain of HIV subtype B.
During the 36-month trial, a total of seven injections were administered at months 0, 1, 6, 12, 18, 24 and 30. The company said 105 volunteers who received placebo became infected with HIV and 106 volunteers who received at least one injection of AidsVax B/E became infected, producing an infection rate in placebo and vaccine recipients of 3.1 percent.
In the earlier Phase III trial, AidsVax B/B was studied in 5,400 volunteers, primarily homosexual men. The vaccine was designed to work against two B strains. Investigators had hoped the trial would show that the vaccine worked at least 30 percent better than placebo in stopping the HIV infection. However, the reduction of infection among volunteers who received at least three doses turned out to be 3.8 percent (p=0.76).
The data did indicate a statistically significant reduction of HIV infection among blacks and Asians. There were 67 percent fewer HIV infections among 498 volunteers classified as ethnic minorities, other than Hispanics, who received vaccine compared to placebo (p<0.01). There were 78 percent fewer HIV infections among the 314 black volunteers who received vaccine, compared to placebo (p<0.02).
Yip said final data related to the earlier Phase III likely would be presented at an appropriate scientific forum or in a peer-reviewed journal.
Toward its refocusing end, VaxGen recently received an $80.3 million grant from the National Institutes of Health for the development of an anthrax vaccine. Yip said the vaccine, rPA102, is the subject of Phase I trials. (See BioWorld Today Oct. 2, 2003.)
The company also is developing a smallpox vaccine.
VaxGen was spun out of South San Francisco-based Genentech Inc. in 1995 for the purpose of developing an AIDS vaccine. At the outset, Genentech had a 25 percent equity stake in VaxGen. Today Genentech owns 10 percent to 11 percent of the company. (See BioWorld Today, July 1, 1999, and Oct. 13, 1999.)