Atripla, a new fixed-dose once-a-day tablet for the treatment of HIV-1, is shown at the National Press Club in Washington, Wednesday, July 12, 2006. [AP Photo]

People infected with the virus that causes AIDS will soon be able to take a once-a-day pill that combines three drugs in a "cocktail" therapy that can be swallowed in a single dose.

The pill, called Atripla, includes three Food and Drug Administration-approved medicines that already form one of the most widely prescribed treatments for HIV and AIDS. The FDA approved the combination version Wednesday.

The medicine will still be expensive: more than US$1,100 for a month's supply.

Atripla can replace the two or more pills HIV-positive patients now must take each day to keep the human immunodeficiency virus in check, making it simpler to stick to a treatment regimen. The new pill is expected to be available within seven business days.

"As a physician, I know, whether in dealing with cancer or dealing with infection, that's an opportunity to significantly improve compliance. And compliance with therapy is as important as the therapy itself for a successful outcome," said Dr. Andrew von Eschenbach, the FDA's acting commissioner.

If the single pill does help patients stick to their pill-taking regimen, that in turn could slow the emergence, and ultimately, transmission, of drug-resistant strains of the virus. Those strains can evolve when patients take less than 95 percent of their pills, said John Martin, head of Gilead Sciences Inc., the manufacturer of two of the drugs in Atripla.

"The fewer pills, the better they are able to achieve that 95 percent threshold," Martin said.

Atripla won't do away with the multiple other drugs that AIDS patients often must take to fend off infections and other complications of their weakened immune systems, said Frank Oldham Jr., executive director of the National Association of People with AIDS. And some patients will have to take other HIV drugs along with Atripla to combat the virus effectively.

Atripla combines Viread (tenofovir), Emtriva (emtricitabine) and Sustiva (efavirenz). Viread and Emtriva, both made by Gilead of Foster City, Calif., are now sold in combination under the brand name Truvada. Sustiva is made by New York-based Bristol-Myers Squibb Co.

The pill will be just as expensive as Truvada and Sustiva when purchased separately: The wholesale price will be US$1,150 for a 30-day supply. Switching to the combo pill would require insured patients to make just one, rather than two, co-payments, saving some money.

Several initial attempts by the two companies to combine the three drugs failed. The two companies then settled on a process called "bi-layer" technology to join them in a single pill.

"The fact that innovator companies in the US have actually heeded the call to collaborate on this is just an amazing happening," said Veronica Miller, director of the Forum for Collaborative HIV Research. The effort, Miller said, could lead to future collaborations on better drug combinations formulated for use in infants and children.

The FDA approved last month the first three-drug combination pill to treat HIV as part of foreign AIDS relief efforts. Atripla also will be available for use in the 15 countries covered by that program, the President's Emergency Plan for AIDS Relief. Unlike Atripla, the other combo pill must be taken twice daily and is for sale only outside the United States.

Interest in Atripla as the first once-daily, three-drug pill may be greatest in developing countries, for both medical and logistical reasons, said Dr. Murray Lumpkin, deputy commissioner for international and special programs at the FDA.

"The idea of having a fixed-dose combination has been one of the, as you might say, one of the holy grails," Lumpkin said.

About 40 million people worldwide, including 1 million Americans, are HIV positive. Each year, roughly 5 million people are infected with HIV and 3 million die from AIDS, according to the World Health Organization.

The three drugs inhibit the replication of HIV within the body but are not a cure. Nor will the new pill be suitable for all patients: Sustiva, for instance, can cause birth defects. Serious psychiatric symptoms including severe depression, suicide attempts, aggressive behavior, delusions and paranoia also have been reported in patients taking the drug.

Gilead, Bristol-Myers Squibb and Merck & Co. Inc. intend to seek approval to sell the pill outside the US

Merck, based in Whitehouse Station, N.J., is involved because it has rights to market one of the three drug ingredients, efavirenz, under the brand name Stocrin in many foreign countries, including most of the developing world.