A DRUG traditionally used to treat breast cancer also reduces the size of harmful protein deposits in AL amyloidosis, a disease with some similarities to Alzheimer鈥檚. Giampaolo Merlini, the Italian doctor who made the chance discovery, says it could point the way to a treatment for other amyloid diseases such as Alzheimer鈥檚, Britain鈥檚 fourth biggest killer.
The protein deposits, called amyloid fibrils, are symptomatic of a number of diseases. The fibrils are stable aggregates of protein that collect between the cells within organs, especially the kidneys, liver, spleen and skin. Fibrils are also consistently found in the brains of people with Alzheimer鈥檚. Mark Pepys, an expert on amyloid diseases at Hammersmith Hospital in London, says there is now 鈥渙verwhelming鈥� evidence that amyloid deposits cause the symptoms of Alzheimer鈥檚.
Amyloid diseases can prove fatal, and until now the only treatment has been organ transplants, obviously impossible for patients with Alzheimer鈥檚.
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The new discovery was made when a colleague of Merlini鈥檚 at the University of Pavia began taking an anti-cancer drug known as IDOX (4鈥�-iodo-4鈥�-deoxydorubicin). IDOX is widely available in Europe as a treatment for breast cancer, but Merlini鈥檚 colleague was suffering from a cancerous form of AL amyloidosis. In such cases, cancer cells in the bone marrow overproduce the protein that creates the fibrils. IDOX was originally prescribed to kill off these cancer cells but it also immediately began to shrink the fibrils.
鈥淧reviously he had a large visible lump of amyloid in his leg which stopped him walking very far,鈥� says Merlini. 鈥淏ut after just 48 hours of taking IDOX, he was able to walk long distances.鈥� The drug has since been tested on eight other patients and it is now entering clinical trials. No one yet knows how the drug works.
Unfortunately, because IDOX was designed as an anti-cancer drug, it can only be given to patients suffering from the cancerous form of AL amyloidosis. Its ability to kill cells would produce severe side effects, and while toxic drugs are common in cancer treatment, they would be unacceptable in other patients. But Merlini says that the section of the IDOX molecule that is active in reducing fibrils is not toxic. He is now working on a non-toxic version of the drug as a possible treatment for Alzheimer鈥檚 and other amyloid diseases. But he says that it may take more than five years to develop.
