Researchers say a drug commonly used to treat malaria and rheumatoid arthritis has also proved effective in treating some aggressive cancers. When scientists administered hydroxychloroquine, an anti-malarial drug, together with known cancer drugs, they found it stopped the growth of cancerous tumors in two-thirds of the patients.
Scientists know that human cancer cells grow by getting energy from adjacent tumors, where cells have begun to self-destruct.
The spread of cancer is accelerated by the death of these cells.
“This process called autophagy, which literally means to self-eat, is present in all cells," said Dr. Ravi Amaravadi. "But what we are finding in our research is that cancer cells have a very high level of autophagy even before any treatment, and so they are poised to take on the damage from existing cancer therapies and simply break down the damaged parts to fuel further growth.”
Dr. Ravi Amaravadi spoke to us via Skype. He is a cancer specialist at the University of Pennsylvania School of Medicine. His group treated patients by combining conventional cancer medications with the anti-malarial drug, hydroxychloroquine. The compound is known to inhibit autophagy and researchers hoped it could stop cancer cells from growing.
In clinical trials, scientists found that hydroxychloroquine paired poorly with some cancer drugs. But it worked well with others, such as Temsirolimus, in helping to halt tumor growth - a so-called "stable disease" rate - in patients with melanoma, an aggressive skin cancer.
“And when Temsirolimus [a cancer drug] was tested in melanoma, it had zero percent stable disease rate," said Amaravadi. "And when we combined with hydroxychloroquine malaria drug, the stable disease rate went up to 76 percent so that’s a very big difference.”
Researchers used a high dose of hydroxychloroquine to block autophagy, much higher than what's normally used to treat rheumatoid arthritis or malaria. The dosage has not yet proved harmful.
Dr. Davide Ruggero at the University of California, San Francisco, is also studying the growth of cancer cells. He says the results of the research with hydroxychloriquine are promising.
“This is a great discovery because we know that the compounds are not toxic - have already been used," said Ruggero.
But Dr. Amaravadi warns that oncologists should not use the anti-malaria drug outside of clinical settings. He says hydroxychloroquine has severe side effects when combined with some cancer drugs. So the knowledge of which compounds work well together is critical.