By Will Dunham
WASHINGTON, April 4 (Reuters) - The new AIDS drug Prezista performed very well in halting the onslaught of the human immunodeficiency virus in people with advanced infection, a study published on Wednesday showed.
The success of the drug, made by the Johnson & Johnson <JNJ.N> unit Tibotec Pharmaceuticals Ltd., comes at a time of acute need for new AIDS therapies because many existing drugs are failing as HIV mutates to thwart them.
It is in a class of drugs called protease inhibitors that are designed suppress HIV and prevent it from replicating. The researchers said Prezista, also called darunavir, expands treatment options for patients who do not improve with other treatment.
It is given along with a low dose of an older protease inhibitor called ritonavir.
Prezista won approval from the U.S. Food and Drug Administration last year, marking Johnson & Johnson's initial foray into the $1.5 billion U.S. market for protease inhibitors. It received conditional marketing approval in the European Union for all 27 member states last month.
The researchers tracked 110 people given Prezista in combination with ritonavir and 120 people getting other protease inhibitors for about 11 months.
Forty-five percent of those getting Prezista experienced a drop in their viral load -- the concentration of HIV in their blood -- to undetectable levels, compared to 10 percent of those getting other drugs, the researchers said.
HIV ravages the body's immune system by attacking certain protective white blood cells. Patients getting Prezista had an increase in the number of these cells five times higher than the other patients, the study found.
About 40 million people are infected with the incurable AIDS virus worldwide.
Researchers led by Dr. Bonaventura Clotet of the Hospital Universitari Germans Trias i Pujol in Barcelona, Spain, reported the results in the Lancet medical journal.
"Its potency has been something that has been very unexpected and very impressive," Clotet said in a telephone interview.
"We were very excited by the findings of quite dramatic suppression in viral load in patients," Clotet added.
While many AIDS drugs are available, experts say an alarming number of patients are becoming resistant to them because the virus can mutate quickly -- particularly if patients fail to meticulously follow their drug regimens -- rendering some drugs ineffective.
Dr. Rodger MacArthur of Wayne State University in Detroit, Michigan, who wrote a Lancet commentary on the findings, said doctors treating AIDS patients will welcome the findings. He said patients have been given the drug at Detroit Medical Center.
"The patients who have gone on it have done remarkably well. It seems to be very safe. It seems very well tolerated," MacArthur said in a telephone interview.
"There really is nothing else in this class that is in development, or at least not that is close to entering clinical trials. So this is likely to be the last (new) protease inhibitor that we see for three to five years," MacArthur added.