Study Finds Pill Coating
Kills HIV, Herpes And More
By Maggie Fox
Health and Science Correspondent
WASHINGTON, (Reuters) - An ingredient used to coat pills to help them last longer in the digestive system could offer a new avenue for preventing transmission of the AIDS virus, researchers said on Monday.
They said the ingredient kills not only the HIV virus that causes AIDS, but the herpes virus and the bacteria that cause a range of sexually transmitted diseases (STDs), including gonorrhea, trichomonas and chlamydia.
Formulated into a cream, it has worked in mice to prevent sexual transmission with no serious side-effects, said Dr. Robert Neurath, head of the Laboratory of Biochemical Virology at the New York Blood Center.
The ingredient is used to coat enteric tablets, which must dissolve in the small intestine rather than in the stomach. Known as cellulose acetate phthalate, it holds its own in the acidic environment of the stomach but breaks down in the more alkaline environment of the intestine.
It is classified as an "inert" substance -- one that has no active effects -- and Neurath said he never dreamed such a chemical would work.
"This was a step prompted by desperation," he said in a telephone interview.
Neurath's team had been looking for a microbicide -- something besides a condom that women, and men, could use that would protect them from STDs and especially HIV. Groups that lobby for the development of a microbicide say many men refuse to use condoms and beat sexual partners who demand their use.
The result is that many women are infected each year.
Advocates for microbicides argue that a cream that could be used easily and privately would save millions of lives.
About two years ago, Neurath said, his team modified a milk protein that worked well against HIV and herpes viruses.
But they ran into a roadblock -- mad cow disease. Bovine spongiform encephalopathy (BSE) had swept British herds and there were some suggestions it could be passed on in milk.
"There was some concern expressed that milk-derived products should not be used for medicinal purposes," Neurath said. So his team had to look for something else.
"We decided to either have a quick success or get out of the field of microbicides," he said.
"We looked for something inexpensive, widely available, with possible broad activity. We also suspected that other people probably never actually screened what are called inactive ingredients for activity, so we thought we would be the only ones doing it."
They trawled through several hundred compounds listed in a book, testing each one against HIV.
Finally they came upon cellulose acetate phthalate. Writing in the British journal Biologicals, published by the International Association of Biological Standardization, they said they formulated a cream containing the compound.
Not only did it work in mice to kill viruses and bacteria, but it did not kill the "good" bacteria such as lactobacilli, which belong in a healthy vagina.
Neurath's team did not test it against sperm but assume that it will inactivate sperm, acting as a contraceptive.
Other researchers are racing to get microbicides to market and have found them in similarly unlikely places, such as a detergent widely used in toothpaste.
"We were trying to avoid the use of detergents because detergents affect cells," Neurath said.
Because cellulose acetate phthalate is widely used in tablets, it must be safe, he added.
He feels the discovery was simply lucky.
"There were other compounds used for tablet coating which are similar to the one we discovered which had absolutely no activity," he said. "I think it was a chance discovery."
The United States has the highest incidence of STDs in the industrialized world, with 66 million people, or more than one in three people aged 15 to 65 infected with at least one incurable STD such as HIV or herpes.
An estimated 42 million people worldwide are infected with HIV and 13 million have died of AIDS, according to the World Health Organization. AIDS is now the fourth leading cause of death worldwide.
Neurath's team is working with the National Cancer Institute and other groups to develop the cream.