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MELBOURNE, Australia -- An experimental, three-drug tuberculosis (TB) treatment regimen demonstrated bactericidal activity in patients with drug-sensitive or multidrug-resistant disease, researchers reported here.

The combination of the investigational agent nitroimidazole (PA-824), moxifloxacin, and pyrazinamide resulted in 71.4% of TB patients achieving clearance of bacteria in the sputum compared with 37.8% of patients on standard of care after 8 weeks of therapy (P<0.05), said , of the nonprofit TB Alliance in New York City, and colleagues.

The combination fared particularly well in patients with drug sensitive TB compared with standard therapy, the authors said in a presentation at the International AIDS Conference.

About 20% of the patients in the short-course arm were co-infected with HIV, Everitt said during a press briefing, but the results among those co-infected patients did not differ from the others as far as treatment for TB was concerned.

"We found there were no differences in how well people responded in clearing bacteria out of their system," Everitt said. "I think the experience was very similar to people with HIV versus those who were not HIV infected. There was no need to adjust doses for people living with HIV in this group."

One of the primary goals with TB treatment is to reduce the time for therapy to 4 to 6 months from the current 1 to 2 years, Everitt explained.

The researchers enrolled 181 patients with drug-sensitive TB and 26 patients with multidrug-resistant TB. The study was conducted at six sites in South Africa and at two sites in Tanzania.

The patients who had completed 8 weeks of therapy at the time of analysis included 56 patients on the daily 200 mg dose of nitroimidazole in the combination, and 54 patients on the 100-mg dose of nitroimidazole in the combination. Another 54 patients were assigned to standard of care, the combination of isoniazid, rifampicin, pyrazinamide, and ethambutol.

The mean age of the patients was 31, about 65% were men, and 71% were black.

After 8 weeks, 71.4% of patients in the 200 mg-arm combination achieved bacterial clearance of bacteria in the sputum compared with 65.7% of those in the 100-mg arm and 37.8% of those on standard therapy.

Daily log reduction in bacteria was 0.155 in the 200-mg combination versus 0.112 log reduction in the standard care treatment arm (P<0.05), Everitt said.

The positive results from this trial will give the TB Alliance momentum to conduct a phase III trial with a planned recruitment of 1,500 patients, Everitt explained.

But he cautioned the study's "2 months of treatment would not be considered a cure."

"So all of these patients will go on to a complete course of treatment afterwards under their national TB program," he told MedPage Today.

In the phase III study, patients will be treated for either 4 months or 6 months and then will be followed for up to 2 years to determine if the shorter treatment prevents disease rebound.

CEO of the TB Alliance, pointed out that the organization has made a phase III trial possible for about $50 million, using grants from philanthropic agencies and some government agencies. That's a fraction of what it costs pharmaceutical companies to reach the same stage, he said.

He stated that TB "is the quintessential disease of poverty, and that is one of the reasons why developing new therapeutics has been so problematic. There really has been no commercial incentive for the normal development process. The return on investment just isn't there."

"One of the key elements of the nonprofit formula is that everything we develop has to be both affordable and available to those in need," Spigelman explained. "We can do this because of the willingness of these funding groups to support the research and development."

, of the Burnet Institute in Melbourne, who moderated the press conference, told MedPage Today that "in tuberculosis, there has not been development of drugs for a long period of time and the results of those coming through now are quite promising, with the ability to shorten treatments for patients with HIV and also for those without HIV."

Shorter treatment times should lead to cost savings, Spigelman said. "If you look at the U.S, therapy for one multidrug-resistant TB patient can run $500,000," he said. "Even with drug-sensitive tuberculosis, we are still looking at 6 to 9 months of therapy."

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