TORONTO - A team of Canadian and U.S. researchers has developed a new "sharp-shooter" drug they hope may be a breakthrough in treating several types of aggressive cancer.
The drug, known for now as CFI-400945, is a new class of cancer agent that targets an enzyme involved in some malignancies, among them certain types of breast cancer, and ovarian, colorectal, pancreatic and prostate cancers.
In tests on specially bred lab mice with human breast and ovarian cancers, CFI-400945 "responded spectacularly," significantly shrinking the tumours, said co-principal investigator Dr. Tak Mak of Princess Margaret Cancer Centre.
But the world-renowned researcher cautioned these results occurred in mice — and human cancers can be far more complex.
"To find a cure is our shared dream; our nightmare is that it is not yet within our reach," Mak told a packed news conference at the Toronto hospital Tuesday. "Cure is not a word we like to use lightly and we refuse to use it recklessly or promise you something we cannot deliver."
Still, he and principal collaborator Dr. Dennis Slamon of the University of California at Los Angeles, who developed the blockbuster breast cancer medication Herceptin, are excited about the promise of the new drug that's taken a decade to develop.
The scientists have applied to the U.S. Food and Drug Administration and Health Canada to begin testing the drug in a small group of patients to see if it is safe and appears to have some effect in killing cancer cells.
CFI-400945 is a new-generation drug that takes a different approach to eradicating tumours than long-standing cancer treatments.
Traditional chemotherapy works by attacking fast-dividing cancer cells. But these drugs also end up destroying other quickly dividing — and perfectly healthy — cells in the body, leading to often severe side-effects. And often, the effects of chemo wear off over time, allowing some cancers to recur.
With certain types of cancer, "one-size-fits-all therapy isn't going to work," said Slamon, explaining that researchers have been working to create different classes of drugs that home in on cancer cells only, leaving healthy cells alone.
"We began to look for specific therapies designed to fix what is broken instead of throwing in a bomb hoping to kill more bad than good cells," he said. "So we would target what's broken in the malignant cells. And since the normal cells don't have what's broken, they would be spared.
"And that is the whole idea of designer therapy or sharp-shooter drugs."
CFI-400945 is a new class among these designer drugs, designed to take aim at an enzyme called PLK4, which plays a critical role in cell division, especially in cancer cells.
Cells in some "genomically unstable" cancers can have scores more chromosomes than the 46 present in normal cells, and these malignant cells rely on PLK4 to be able to continue to proliferate out of control.
"So we target (the enzyme) to make sure that those cancer cells that have many chromosomes and aren't genomically stable cannot survive," said Mak.
If given FDA go-ahead for a patient trial, researchers will begin by administering the drug in about 30 volunteers with breast or ovarian cancer to see how strong a dose they can tolerate without it becoming dangerously toxic.
"We need to know that at the level below toxicity that it has signals that cancer cells will respond, and we will take it one day at a time," Mak said.
The researchers hope to have FDA approval by the fall, and would start their patient trial by the end of the year. If effective, Mak estimates it could be less than 10 years before the drug is approved for widespread use.
"I cannot promise you that it will work," he said of the experimental drug, "because in advanced human cancer there are many other questions that we have not got answers to.
"But we promise you this is the beginning," said Mak, his voice breaking with emotion. "There will be another drug that we will be filing for (approval) next year — and next year and next year — until we get this done."
It's taken about 100 researchers in Toronto, L.A. and China to develop CFI-400945 at a cost so far of about $40 million, said Mak, standing beside a copy of the 4,300-page application submitted to the FDA, the height of about five Toronto phone books.
That money all came from non-government sources, raised through 10 years of fundraising walks to end women's cancers, and private and corporate donations.
"Without the donors, this wouldn't be a reality," said Mak, who along with Slamon lauded fundraisers attending the announcement, among them some who have had family members or friends with cancer or been diagnosed with the disease themselves.
One of those is Randy Mellon of Toronto, who has raised about $250,000 for the Princess Margaret Cancer Foundation in the last 10 years through the annual weekend walks and other endeavours.
Mellon, who lost her father to leukemia and whose mother is a breast cancer survivor, was diagnosed in February with an aggressive form of breast cancer known as her2-positive, the kind Herceptin is designed to treat.
"This year the walk takes on a new and very personal meaning," said Mellon, who starts Herceptin in a few weeks in conjunction with chemotherapy and following radiation treatment.
"The irony is not lost that the hospital I raised so much money for is now the hospital that is going to save my life."
Mak said making the announcement about the new drug was emotional "because it's taken a long time and I have known many patients and I've known many people who have been affected and many people who have had this."
The award-winning scientist first came to prominence as the co-discoverer in 1984 of the T-cell receptor, a milestone in the study of the immune system.
"That was an academic discovery and, of course, it was greatly gratifying to be able to contribute to the understanding of how the immune system works.
"But this is not in the same league," Mak said of CFI-400945. "This is way above."