A new family of anti-cancer drugs based on the metal silver has been discovered by researchers working at the University of Johannesburg (UJ) in South Africa. Earlier this week the University published a press release in which the scientists reported that a silver thiocyanate phosphine complex – known as UJ3 – had been tested successfully in their laboratory using both rats and human cancer cells. Published recently in BioMetals, UJ3 was shown to be as effective in destroying cancer cells as a widely used chemotherapy drug (see light microscope images below left, © UJ).

“The UJ3 complex is as effective as the industry-standard drug Cisplatin in killing cancer cells in laboratory tests done on human breast cancer and melanoma, a very dangerous form of skin cancer,” said biochemist Marianne Cronjé. She continued: “However, UJ3 requires a 10 times lower dose to kill cancer cells. It also focuses more narrowly on cancer cells, so that far fewer healthy cells are destroyed.” Encouragingly, not only is a much lower dose required, but UJ3 is also far less toxic.

The drug was synthesised in the laboratory of chemist Reinhout Meijboom who commented: “In rat studies, we see that up to 3 grams of UJ3 can be tolerated per kilogram of bodyweight. This makes UJ3 and other silver phosphine complexes we have tested about as toxic as Vitamin C.” The University, which has been awarded a United States patent (9,676,801) for the use of silver complexes as anti-cancer agents, is optimistic that UJ3 will become a successful chemotherapy drug in future, where the lower dose, decreased toxicity and greater focus on cancer cells will mean fewer side effects.

Meijboom explained: “UJ3 appears to target the mitochondria, resulting in programmed cell death to kill cancer cells – a process called apoptosis. When a cancer cell dies by apoptosis, the result is a neat and tidy process where the dead cell’s remains are ‘recycled,’ not contaminating healthy cells around them, and not inducing inflammation.”

Seen at right is the team of Meijboom, Cronjé and Zelinda Engelbrecht (© UJ) who published their findings in BioMetals. Because UJ3 and the other anti-cancer drugs are based on silver, rather than platinum, they are far more economical to produce. The silver complexes can also be synthesised with standard laboratory equipment, opening the way for large-scale manufacture. While research on UJ3 and other silver-based drugs is ongoing at the University, their search for the “silver bullet” appears to be gathering momentum.