Crocus plant to provide a tumor killing “smart bomb”

By Dr. Ananya Mandal, MDSep 12 2011

According to the latest research, a drug derived from plant extracts could wipe out tumors in a single treatment with minimal side effects. Scientists have turned a chemical found in crocuses into a ‘smart bomb’ that targets cancerous tumors. The advantage is that healthy tissue is unharmed, reducing the odds of debilitating side effects. And unlike other side effect-free drugs, it is able to kill off more than one type of the disease, including breast, prostate, lung and bowel cancer. Potentially, all solid tumours could be vulnerable to drugs developed this way, meaning it could be used against all but blood cancers.

In some tests of the drug, half of tumors vanished completely after a single injection, the British Science Festival will hear this week. The drug, based on colchicine, an extract from the autumn crocus, is at an early stage of development, and has so far been tested only on mice. It is known as a vascular disrupting agent (VDA).

But the University of Bradford researchers are optimistic about its potential in humans.

Professor Laurence Patterson said: ‘What we have designed is effectively a “smart bomb” that can be triggered directly at any solid tumor without appearing to harm healthy tissue. “If all goes well, we would hope to see these drugs used as part of a combination of therapies to treat and manage cancer,” he said.

Colchicine has long been known to have anti-cancer properties but has been considered too toxic for use in the human body. To get round this, the researchers attached a chemical ‘tail’ to it, deactivating it until it reaches the cancer. Once there, the tail is cut off by an enzyme called MMP, which is found in tumors. Removing the tail activates the drug, which then attacks and breaks down the blood vessels supplying the tumors with oxygen and nourishment.

“The drug is inactive until triggered by the activity of an enzyme that is always found in the tumor environment but not elsewhere. Triggering releases a potent, anti-cancer agent which destroys the tumor's blood vessels, effectively starving the tumors to death, a process known as hemorrhagic necrosis,” Dr Adams explained. Tests on specially bred mice that have human cancerous tumors have shown that the drug and its delivery system can have a “cure rate” of greater than 70 per cent after a single dose, he said. Four different cancers have been treated and the animals suffered no adverse effects.

Cancers use the blood supply to spread around the body and it is hoped that the treatment, called ICT2588, will also combat this. The first tests on humans could start in as little as 18 months at St James's University Hospital in Leeds. If successful, the drug could be on the market in six to seven years.

Henry Scowcroft, of Cancer Research UK, said, “This is exciting but very early work that hasn’t yet been tested in cancer patients.” Professor Paul Workman, of the Institute of Cancer Research in London, said the results so far were promising. He added, “If confirmed in more extensive laboratory studies, drugs based on this approach could be very useful as part of combination treatments.”