ABSTRACT In the past few decades, a tremendous amount of effort has been invested in developing gene and cell therapies for inherited genetic diseases such as Huntington's disease (HD). However, progress in their clinical application has been very limited. One of the major barriers is the lack of appropriate animal models that allow precise prediction patterns in human patients. Most of the animal models used for gene and cell therapy study are primarily focused on safety and toxicity evaluation, while therapeutic efficacy cannot be fully addressed because they do not carry the same human diseases. Although mouse models of human diseases are available and have been widely used for the development of new therapies, mice are not good predictors for humans because of the fundamental differences (genome composition, body size, life span and metabolic mechanism) between humans and rodents. Although monkeys are one of the best models for studying pharmacokinetics and overall impact of treatment, they are primarily used for safety and toxicity evaluation. Even HD monkey models, created by chemical induction or focal gene transfer in the brain, develop similar cellular pathology, therapeutic efficacy and systemic evaluation cannot be determined, which is one of the major barriers in drug and therapeutic development. The development of transgenic HD monkeys has opened the door for a new paradigm of animal modeling for the advancement of novel gene and cell therapy. HD monkeys not only carry the genetic defect that leads to human HD, they also develop clinical features comparable to humans that no other animal model does. While testing in HD monkeys has yet to be achieved until a cohort of well characterized HD monkeys was established, iPS cell lines derived from HD monkeys with a board spectrum of HD pathology and clinical features are a unique in vitro model for studying HD pathogenesis and the development of novel therapeutic approaches. New knowledge and treatments generated from iPS cells can next be translated and applied in HD monkeys from whom the stem cells were derived, thus the goal of personalized medicine can also be evaluated.