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May 1, 2007
PRO 140 Has Potent and Lasting HIV Effect (AIDSmeds.com)
by Tim Horn
Progenics Pharmaceuticals has announced encouraging results from an early study of PRO 140, its experimental HIV entry inhibitor. Of particular interest, the company noted in a press release, was the fact that viral loads remained 90% below pre-treatment levels two to three weeks after a single dose of the drug.
PRO 140 is a laboratory-made antibody that binds to a protein on the membrane of CD4 cells called CCR5. Once it does this, HIV cannot successfully bind with the surface of CD4 cells, thus preventing the virus from infecting healthy cells.
While Celsentri® (maraviroc), which was recently recommended for FDA approval by the agency's Antiviral Drugs Advisory Committee, works differently than PRO 140, both drugs target CCR5 and are being tested as HIV entry inhibitors.
Progenics' clinical trial, conducted at 10 sites in the U.S., examined three single intravenous doses of PRO 140: 0.5 milligram per kilogram (mg/kg) of body weight, 2.0 mg/kg, and 5.0 mg/kg. A total of 39 HIV-positive patients were enrolled in the study, none of whom had used antiretrovirals in the past.
All patients were screened prior to the study for the presence of virus that utilizes only CCR5 as the entry coreceptor (as opposed to the CXCR4 coreceptor). Of the 13 patients in each dosing group, 10 patients received PRO 140 and three received placebo.
No other HIV medications were taken in the study.
Viral load reductions were the chief focus of the study. Patients who received 5.0 mg/kg of PRO 140 achieved an average maximum decrease of viral load of 1.83 log (98.5%), with some patients achieving viral load reductions of 2.5 log (99.7%).
Nine days after receiving single-dose PRO 140, these same individuals had viral loads that averaged 1.7 log (98%) below their pre-treatment levels. And after two to three weeks, patients who received 5.0 mg/kg PRO 140 still averaged viral loads 1.0 log below pre-treatment levels.
Thirty days after single-dose PRO 140, viral loads in most patients had returned to their pre-treatment levels.
According to the press release generated by Progenics, the completed study found PRO 140 to be generally well tolerated with no serious drug-related adverse events reported.
A more detailed discussion of the study results is planned for an upcoming scientific conference.
