Chloroquine eyed as anti-cancer drug

Dr. Hoyun Lee, a career scientist at Sudbury Regional Hospital’s Regional Cancer Program, plans to begin testing the effectiveness of chloroquine as an anti-cancer drug on laboratory animals at Laurentian University.

The decision follows promising results from in vitro testing at the Regional Cancer Program and the publication of Lee’s findings in the European Journal of Pharmacology in December 2009. The paper, co-authored by Dr. Raja Solomon and entitled, “Chloroquine and its analogs: a new promise of an old drug for effective and safe cancer therapies,” was 16th on a list of the most downloaded articles from the journal’s website between October 2009 and September 2010.

According to Lee, “accumulating lines of evidence now suggest that chloroquine can effectively sensitize cell-killing effects by ionizing radiation and chemotherapeutic agents in a cancer-specific manner.”

Chloroquine, in combination with other therapies, killed cancer cells 100 times more effectively than non-cancer cells.

“In my mind this was huge,” said Lee. “Cancer therapy causes a lot of side effects because the drugs also kill a lot of normal cells. If we can kill cancer cells more selectively, you can see the potential.”

The chloroquine accumulates in the lysosomes, tiny cellular organelles that break up waste materials and cellular debris. The lysosomes are clogged by the chloroquine, expand like a balloon and pop, said Lee, but why normal cells don’t die as readily as cancer cells is still a mystery.

Chloroquine is a synthetic derivative of quinine and is widely used as an anti-malarial drug and anti-rhematoid agent. It was discovered in 1934, but was considered too toxic for human use and ignored for a decade. During World War Two, clinical trials sponsored by the U.S. government for anti-malarial drug development demonstrated chloroquine’s effectiveness, leading to its introduction into clinical practice in 1947.

The medicinal properties of quinine, a natural product sourced from the bark of the chinchona tree, were originally discovered by the Quechua Indians of South America.

Researching the effectiveness of chloroquine as an anti-cancer drug may not be of interest to big pharmaceutical companies because the patent expired a long time ago.

“One of the difficulties of having a clinical trial is that nobody could make money even if it works,” said Lee. Developing an analog of chloroquine that’s more effective as an anti-cancer drug is one possibility, but it would take much more time to test it and win approval to use it. The benefit of using chloroquine is that its safety is already well established and it could be fast-tracked for use as an anti-cancer drug.

According to a study on drug development cited by Lee and Solomon in the introduction to their paper, “developing a single effective cancer drug takes an average of 15 years and US $800 million.”