ATHX-105 for obesity. In addition to our MultiStem programs, we are developing pharmaceuticals for the treatment of obesity and certain neurological conditions associated with cognition, attention and wakefulness. In the obesity area, we are developing compounds that selectively stimulate the 5HT2c serotonin receptor in the brain, which is known to play an important role in regulating appetite. These compounds, known as 5HT2c agonists, are designed to reduce appetite and food intake, in order to achieve substantial weight loss over time.
We have completed several clinical trials involving ATHX-105, a potent and selective 5HT2c receptor agonist that was being developed for the treatment of obesity. In July 2007, we initiated a phase I clinical trial for ATHX-105 in the United Kingdom. The primary objective of the phase I clinical trial was to assess the short-term safety of ATHX-105 and to establish an appropriate dose range for subsequent clinical trials that will be conducted in order to assess safety and effectiveness. The phase I clinical trial, which included 107 subjects, was completed in January 2008, and top line results were announced shortly after completion of the study.
The results of the study demonstrated that ATHX-105 was well-absorbed, resulting in good drug exposures following oral administration, and was generally well tolerated up to a maximum tolerated dose of 100 mg. There were no severe or serious adverse events observed in the clinical trial, no negative effects on cardiovascular, hematology or other clinical parameters, and no discontinuations due to adverse events. In addition to this study, we completed two phase I clinical trials in the United Kingdom to further assess safety and tolerability of ATHX-105 administered at various dose levels, as well as examine regional absorption of the drug in the gastrointestinal tract for the purpose of developing a formulated product.
Based upon the results of these and other studies, we applied to the FDA in the summer of 2008 to initiate a double blind, placebo controlled phase II clinical trial involving administration of ATHX-105 to patients in the United States. In September 2008, following the FDA’s review of our investigational new drug application, or IND, the proposed trial was placed on partial clinical hold pending the receipt of additional information and resolution of several issues relating to ATHX-105’s preclinical package and the proposed phase II study design.
At the suggestion of the FDA, we conducted two additional studies to provide further data about ATHX-105’s potential toxicological profile, one repeating a prior study under different conditions and another study that we had not previously conducted and that is not typically included in preclinical evaluation. While the first study confirmed our prior negative findings, meaning the absence of a relevant toxicological effect, the second study produced data that suggests a rat specific toxicological effect. We met with the FDA to discuss the issues and reached resolution regarding all of the study design issues related to the partial clinical hold. However, based on the results of the additional test and discussions with the FDA, we believe that the apparent rodent specific effect could require additional non-clinical studies and greatly complicate long-term toxicology testing and thereby increase substantially the development time, risks and costs associated with subsequent development of ATHX-105. Furthermore, these increased risks of development could make it substantially more difficult or impractical for us to establish an attractive, third-party collaboration for the further development and commercialization of ATHX-105.
Consequently, we have decided to suspend further development of ATHX-105 and withdraw our IND application, and are currently focusing on the advancement of next generation compounds that exhibit improved characteristics. While the potential significance of this toxicological effect to humans remains unclear, it appears to be a compound-specific effect that is not representative of the class of next generation compounds that we are continuing to develop while we explore potential partnerships for the program.