Mellors moderated a news briefing during which researchers detailed results of phase 3 clinical trials of the new drugs, raltegravir and maraviroc, at the 14th annual Retrovirus Conference in Los Angeles.

Experienced patients with human immunodeficiency virus (HIV) -- the microbe responsible for AIDS -- are infected with virus strains that have developed resistance to almost all classes of drugs designed to fight AIDS.

"We had patients who had no drugs that were still active against HIV," Roy Steigbigel, professor of medicine at the State University of New York Stony Brook Health Sciences Center, told United Press International.

"Yet when these patients were given raltegravir, 61 percent of them were able to reduce viral levels in the blood to undetectable levels," Steigbigel said. "That compared to 5 percent of patients with the same background of drugs who did not receive raltegravir."

Raltegravir is an investigative integrase inhibitor being developed by Merck. In earlier studies, the drug was known as MK-0518.

Integrase is one of the three enzymes of the virus that is required for viral replication. Drugs to inhibit the other enzymes, protease and reverse transcriptase, have already been developed and are basic backbones of multi-drug combinations.

In two phase 3 trials, raltegravir delivered along with the best combination of other drugs available was clearly superior to the best optimized treatment without raltegravir, said David Cooper, director of the National Centre in HIV Epidemiology and Clinical Research in Sydney, Australia.

Overall, Cooper said, 77 percent of the 232 patients in his BENCHMARK-1 trial achieved an undetectable viral load after 16 weeks of treatment, compared with 41 percent of 118 patients who did not receive the experimental drug.

In BENCHMARK-II, Steigbigel said the results mirrored Cooper's trial. He said 77 percent of 230 patients on raltegravir achieved an undetectable virus, compared with 43 percent of 119 patients on the best available care without raltegravir.

Steigbigel said that, when raltegravir was combined with two newly approved agents, the injectable fusion inhibitor enfuvirtide (Fuzeon, also known as T-20) and darunavir (Prezista), "about 98 percent of patients were able to reach undetectable virus levels."

Researchers reporting phase 3 trials of Pfizer's experimental drug maraviroc found similar results in similarly designed trials.

Howard Mayer, executive director of global research and development at Pfizer, said the results of MOTIVATE I and II showed that about 60 percent of 426 patients taking maraviroc were able to lower viral levels to undetectable compared with less than 30 percent of 209 patients on optimized background treatment.

Maraviroc was delivered either once a day or twice a day, with the twice-a-day formulation appearing to have a slightly better result in achieving undetectable levels of virus. Both the regimens, however, were superior to combinations without maraviroc.

Research has determined that undetectable viral levels -- although not a cure -- slows viral replication to the point where the virus has less chance of mutating and developing resistance to the drugs.

Maraviroc is known as a CCR5 inhibitor. CCR5 is one of two receptors used by the virus to help it enter cells, where the virus then begins its replication process.

Mellors said that in order for HIV to enter a cell, it has to go through a doorway. "The virus is like a key to that door, but it requires a receptor, CCR5 or CXCR4, to turn the combination of that lock," he explained. Some individuals have exclusively CCR5 receptors; others have both CCR5 and CXCR4 receptors. In the maraviroc trials, all the patients had CCR5 receptors.

Mellors, in moderating the discussion, noted that the findings seen with maraviroc and raltegravir were similar to the revolutionary results in 1996 at the Retrovirus Conference in Washington in which the first combination therapies were described.

Those studies ushered in the era of effective anti-retroviral therapy that altered the face of the AIDS epidemic in the Western world. Instead of a two-year life expectancy marked by serial bouts of nasty opportunistic infections with uncommon pneumonia and diarrhea, patients who stayed adherent to drug therapy were able to have extended survival.

As good as the results are with maraviroc and raltegravir, Steigbigel told UPI, "We still need to be developing more drugs. This virus always seems to develop resistance to what we throw at it."

The new drugs still require Food and Drug Administration approval before they will be widely available.

earlier related report
Analysis: Formula and death in Botswana
Los Angeles, Feb. 27 (UPI) -- A cascade of human and natural events literally tumbled out of the sky, turning programs designed to help mothers prevent infecting their children with the virus that causes AIDS into chaos.

Instead of saving children, the intersection of floods, formula supply shortages and the uptake of anti-breastfeeding recommendations appears to have led to a 25-fold increase in deaths due to diarrhea diseases among infants in Botswana.

Researchers at the 14th annual Retrovirus Conference in Los Angeles said Monday that during the past decade health authorities have encouraged women infected with human immunodeficiency virus (HIV) to formula-feed their infants -- because HIV can be transmitted through breastfeeding.

In Botswana, an African country at the top of the list in percentage of HIV-infected adults, but with one of the continent's most aggressive treatment programs, thousands of mothers with the virus were bottle-feeding their infants when the rains came in early 2006.

The storms flooded large areas of Botswana, including the second-largest city of Francistown. The floods overwhelmed the city's ability to maintain clean water facilities, and soon after the flooding, health authorities noticed a disturbing increase in hospitalizations for diarrhea among children under six months of age. Most of those children were being fed with formula.

In 2005 Botswana authorities counted 9,166 children who were hospitalized for diarrhea illnesses; 21 children died, reported Dr. Tracy Creek, an epidemiologist with the Centers for Disease Control and Prevention in Atlanta.

In 2006, after the floods, 35,046 children were hospitalized for these diseases, and 532 children died between January and March, she said. She said that the figure is probably an underestimate because it only reports children who died in hospitals.

"A household survey conducted in the area found that 50 percent of infant deaths did not occur in hospital facilities. In one village 30 percent of formula-fed babies -- but none of the breast-fed babies -- died," Creek said.

On top of the diarrhea disaster, health authorities found another epidemic had emerged: More than 153 children died from malnutrition, and 93 percent of those children were being bottle fed.

Creek said it appears that Botswana pharmacies, cut off by the flood and unable to receive adequate supplies of formula from South Africa -- a problem often faced even during good weather -- were providing less than optimal amounts of formula to women for their infants. "Botswana does not have any companies that produce formula," Creek said.

"A lot of things we in the West feel are transportable to developing nations may not be appropriate for the population," Dr. Michael Thigpen, a medical epidemiologist in the CDC's Division of HIV/AIDS Prevention, told United Press International.

Thigpen also presented a study that showed an increase in childhood gastrointestinal illness and excessive deaths among children who discontinued breastfeeding in favor of formula. Several other similar studies were also reported at the conference Monday.

He said that ongoing studies are attempting to determine -- in the light of his and other studies and the Botswana disaster -- whether continuing breastfeeding and risking the transmission of HIV is offset by deaths caused by diarrhea and other infections.

The Botswana experience, and several other reports from clinical trials in Africa at the conference that found problems in trying to reduce breastfeeding, called into question policies and recommendations of the World Health Organization -- and resulted in changes for breastfeeding in developing countries.

Peggy Henderson, a scientist at the Department of Child and Adolescent Health and Development of the WHO, in discussing the Botswana report, said a new consensus statement suggests that when making recommendations for infant feeding by HIV-infected women, healthcare authorities "should take greater consideration of the health service available and the counseling and support she is likely to receive.

"Exclusive breastfeeding (not other alternative food) is recommended for HIV-infected women for the first six months of life unless replacement feeding is acceptable, feasible, affordable, sustainable and safe for them and their infants before that time."

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