Complex sentence: In May 2007, results from the phase I clinical trial of the drug demonstrated "potent, rapid, prolonged, dose-dependent, highly significant antiviral activity" for PRO 140.
Split into simpler sentences: In May 2007, they announced results from the phase I clinical trial of the drug. The researchers said the results demonstrated "potent, rapid, prolonged, dose-dependent, highly significant antiviral activity" for PRO 140.