A study presented at the joint 2008 ICAAC/IDSA in Washington, DC supports the further development for RDEA806, an experimental NNRTI from Ardea Biosciences. Results from a phase 2a, 8-day monotherapy dose finding study were presented. Several doses, in both capsule and enteric-coated tablet formulations, were tested for absorption, drug interactions and anti-HIV activity.

Overall, people taking RDEA806 experienced drops in HIV levels of around 1.7 log. The responses were better at higher doses. The company has decided to proceed with testing 600, 800 and 1000mg enteric-coated tablets in its phase 2b studies, set to begin by the end of 2008.

There were no interactions between RDEA806 and either Viread (tenofovir) or Emtriva (emtricitabine). It does not interact with the CYP3A4 enzyme pathway, so it does not require Norvir boosting.

There were no moderate to severe (grade 3/4) adverse events reported in the study. No drug related rashes were reported, although the study might not have been long enough to detect such a problem.

After years of little development, the NNRTI class of HIV drugs -- which includes Sustiva (efavirenz), Viramune (nevirapine) and Intelence (etravirine) -- is finally seeing some new drug development. In addition to RDEA806, rilpivarine (TMC-278) and Idexa's IDX899 show promise. Widely considered more tolerable than protease inhibitors, NNRTIs have long been hampered by a high degree of cross-resistance leading most people to have only one shot at this class. All of these new drugs seem to overcome resistance to the first generation NNRTIs, giving many a second chance to take NNRTIs.