Dec 05, 2012 - 10:32 pm
See the below re a drug still in trials but looking very exciting:
"New breast cancer drug heralded as breakthrough
It’s being called one of the most promising breast cancer therapies to enter the research pipeline in decades.
A new drug being tested by California scientists is showing a four-fold increase in tumor suppression times for women with advanced forms of the disease and has the potential to surpass the success of Herceptin in prolonging the lives of breast cancer patients.
“I’d say this is groundbreaking,” says Dr. Richard Finn, a UCLA scientist who presented preliminary findings on the compound at a meeting of the American Association for Cancer Research in San Antonio Wednesday.
“This magnitude of benefit really is not seen with many drugs in cancer medicine. There are not many drugs that have preformed that way in any disease,” Finn says.
The drug — known now by the prosaic, pre-commercial name of PD 0332991 — has yet to enter the large-scale, Phase 3 trials that could send it into wide-spread clinical use.
But its success in the just-completed Phase-2 research being reported rivals the results shown by the miracle drug Herceptin at a similar stage of testing two decades ago.
However the new drug — which pushed tumor suppression times up to an average 26.1 months from the 7.5 months seen by patients given a standard treatment — can benefit a far larger breast cancer population than Herceptin, Finn says.
The drug, which was given in conjunction with the staple medication letrozole, targets women with estrogen receptor positive (ER+) tumors, which account for some 50 to 60 per cent of all breast cancer patients.
Herceptin works on cancers known as human epidermal growth factor 2 positive (HER2 +) tumors, which account for just 20-25 per cent of all cases.
Earlier, Phase 1 trials of the new drug showed it was safe for human usage and caused few of the harsh side effects associated with many chemotherapies.
For the most recent trial, some 160 patients with incurable breast cancer were split into two equal groups, with both receiving letrozole but only one the new, pill-delivered compound.
In other findings reported Wedneday, the new drug also brought the number of patients responding positively to chemotherapy to 45 per cent — up from the 31 per cent in those who were given letrozole alone.
Some 70 per cent of those on the drug had tumor shrinkage for at least six months compared to 44 per cent on the standard medication.
Because Herceptin showed such clear and substantial benefits for patients enrolled in early Phase 3 studies, those trials were halted in the late 1990s and the drug was fasttracked to market.
Finn, who will help launch large scale trials early next year, hopes the new drug could follow a similar approval pathway.
“I think that’s always possible in clinical studies,” he says.
Finn says traditional ER positive chemotherapies like letrozole — marketed as Femara — work by blocking the receptor sites on cancer cells that allow hormones like estrogen to latch on and feed the tumor.
He says PD 0332991 may enhance the effectiveness of these hormone- blocking drugs by amplifying their ability to cover receptors or by blocking different kinds of receptor sites not targeted by the older compounds.
Dr. Jawaid Younus, a top Western University cancer specialist, called the new drug promising, but had the normal reservations that are raised about the size and composition of almost any Phase 2 trial.
“This is definitely exciting. . . . It is certainly promising,” said Younus, an oncologist at the London Ont. school.
“But I think it is too early because of the lack of information that we have with the limited number of patients in a Phase 2 trial. But . . . we look forward to the Phase 3 trial.”
Younus’s key concern was that the patients entered in the recent study were selected by specific cancer markers that may have maximized the drug’s benefits — benefits that might be diluted in a broader ER positive population.
“They were selecting a group that could have imparted a huge clinical benefit and could have moved the progression free survival from a reasonable difference to a significant difference,” he says.
“You don’t know if this humongous difference is going to be sustained.”
Still, Younus says, he’s eager to follow the upcoming Phase 3 trials and hopes that the new drug can add to the limited armament of medications that are currently available for ER positive patients.
Finn says the new drug may work in conjunction with other breast cancer drugs and could transform the ER positive form of the disease into a chronic, treatable condition.
“That’s our hope. When you see this kind of remarkable data in a randomized Phase 2 study, we hope that’s what’s going to happen in the future,” he says.
The drug was originally developed by the pharmaceutical giant Pfizer for potential use in some forms of blood cancers like Myeloma."