Telomerase reverse transcriptase (abbreviated to TERT, or hTERT in humans) is a catalytic subunit of the enzyme telomerase. Telomerase is a ribonucleoprotein polymerase that lengthens telomeres – structures at the end of chromosomes that are DNA strands in the nucleus of all cells. Telomeres protect the ends of the chromosomes from destruction and normal cell death.  The human cell divides anywhere from 60-100 times throughout its life cycle.  Each time this division occurs, telomeres are shortened until they no longer serve to protect the chromosome. This is the basis for the aging process in humans. As cells die, they are no longer able to replicate newer, fresher cells, hence causing our bodies to age.

The telomerase protein plays a role in normal cell death because it is usually repressed, resulting in progressive shortening of telomeres. When telomerase begins to function abnormally, the cell can become immortal. This process is thought to be important in the development of several types of cancer. In 2008, Merck initiated a Phase 1 clinical trial of a DNA cancer vaccine based on Vical’s DNA delivery technology that uses pDNA encoding hTERT. The Phase 1 trial will evaluate the safety, tolerability and immunogenicity of the vaccine.