Anadys Pharmaceuticals, Inc. announced that Anadys and Novartis have decided to discontinue the development of ANA975, a phase 1b compound for the treatment of hepatitis C virus (HCV) infection. The parties have determined that the results received to date from the ongoing 13 week toxicology study together with the results observed in the previous 13 week toxicology study do not support further clinical evaluation of chronic daily dosing of ANA975 in hepatitis C patients.

"Although we are disappointed to discontinue development of ANA975, our animal toxicology results have convinced us that chronic daily dosing of this compound is inappropriate for further clinical development," said Lawrence C. Fritz, PhD., president and chief executive officer of Anadys. "However, we remain optimistic that TLR7 agonists offer therapeutic potential as effective immunomodulators in multiple disease areas, albeit using alternative dosing schedules, and our plans to develop ANA773 for cancer treatment continue unabated," Dr Fritz said.

Anadys continues its development of ANA773, another TLR7 agonist prodrug distinct from ANA975, and expects to file an IND by the end of 2007. Anadys plans to evaluate ANA773 in phase I clinical trials for the treatment of advanced cancer. This programme is independent of the Novartis collaboration and is not affected by the decision to discontinue development of ANA975.

In June 2006, Anadys and Novartis suspended dosing in their 28-day phase 1b clinical trial of ANA975 in HCV infected patients due to then recently obtained information from pre-clinical 13-week toxicology studies. No clinical observations contributed to this decision. Preliminary analysis of the toxicology information revealed various new observations which appeared consistent with intense immune stimulation in animals. Subsequently, the FDA put the ANA975 IND on full clinical hold. In November 2006, Anadys and Novartis initiated a second 13-week toxicology study to understand better the observations from the first toxicology study and to assist in determining a future course of action for the programme.

Analysis of available data from the second 13-week toxicology study, together with the results from the initial 13-week toxicology study led the parties to determine that 1) chronic daily dosing of ANA975 was unlikely to provide an adequate therapeutic index; and 2) additional pre-clinical evaluation would be necessary to determine if alternate dosing schedules of ANA975 would support a safety margin sufficient for further development of this compound for the treatment of patients chronically infected with hepatitis C.