Although our life expectancy has increased tremendously over the last century, there is still a 125-year theoretical limit on our lifespan, and no medical therapy available today has been able to break through this barrier. There is a clock that ticks inside every dividing cell of our bodies. This clock is found at the tips of our chromosomes, in a region of the chromosome called the telomere. When human cells divide, telomeres shorten, and the length of the telomeres correlates with the age of these cells. This telomere clock may be, at least in part, the clock of aging; controlling telomere length may be a way to break through our 125-year theoretical maximum lifespan. Sierra Sciences is working to determine whether telomere shortening really is the primary cause of aging and whether we can prevent it. Telomerase stops the telomere clock from ticking, and can give cells the potential to divide forever. The gene for telomerase is turned on only in our reproductive cells and in cancer cells, and is turned off in almost all other cells. A small-molecule compound could possibly turn it back on to prevent the shortening of our telomeres. Sierra Sciences has discovered 39 families of small-molecule compounds that induce telomerase in human cells. Our chemists have created designer compounds based on one of these families, some of which give us activity up to 16% of what we believe is needed for a human cell to become immortal. Recently, we have also begun screening natural products in a partnership with Isagenix Corporation.