For individuals with severe to profound hearing loss, SPI is developing drugs aimed to regenerate cells within the cochlea and restore hearing. SPI has proprietary compounds that inhibit the cyclin dependent kinase inhibitor 1B (p27Kip1). Inhibition of p27Kip1 induces adult cells within the inner ear to become more stem-like.
For example, in the cochlea of deafened animals, supporting cells can be coaxed to re-enter the cell cycle, proliferate, and regenerate both a supporting cell and a sensory hair cell. This novel technology could be used to repopulate many different types of non-regenerating tissues and organs.
In mice deficient in p27Kip1, terminally differentiated cells within the organ of Corti are now capable of cellular regeneration (Kil 2011). Importantly, these newly dividing cells have the capacity to become replacement auditory hair cells, supporting cells, and neurons in adulthood (Osterle et al 2011).