Cancer Gene Blocker Shows Promise

Cancer researchers today unveiled an experimental drug that curbs the growth of a variety of tumors in animals by suppressing the action of a cancer-related gene, c-Myc.

The drug, designated CX-3543, “has been a very impressive compound in animal tumor models and we are looking forward to moving it into clinical development,” Dr. William G. Rice, from Cylene Pharmaceuticals in San Diego, California said during a press briefing at the annual meeting of the American Association for Cancer Research. The c-Myc gene is active in many types of tumors, and until now had been an “undruggable,” target, Rice and colleagues explain in a meeting abstract. CX-3543 suppresses c-Myc activity by binding to the secondary DNA structures of the gene. CX-3543 also suppresses the growth factor VEGF that promotes formation of blood vessels supplying tumors. In animals grafted with colorectal tumors, CX-3543 produced an 85 percent reduction in c-Myc levels and up to 85 percent reduction in tumor growth, depending on the dose of drug given and when it was administered. In similar prostate cancer experiments, “we saw essentially complete reduction in tumor growth and when we compared CX-3543 to Taxol we saw at least equivalent if not better inhibition,” Rice reported. “Also, in a very-difficult-to-treat pancreatic cancer model, we saw anywhere from 50 percent to 90 percent reductions in tumor growth depending on the dose of CX-3543,” he added. All of these tumors are largely driven by high levels of c-Myc. Dr. Geoff M. Wahl, from The Salk Institute in La Jolla, California, who organized the program for this year’s AACR meeting, said CX-3543 represents “one exciting advance in taking cancer-specific gene alterations and targeting them. This is a new direction in which cancer therapy must go in the future.” (Source: Reuters Health: Megan Rauscher: MedLine Plus: April 2004)