New drug, study method show breast cancer promise
San Antonio • A novel and faster way to test cancer drugs has yielded its first big result: An experimental medicine that shows promise against a hard-to-treat form of breast cancer.
The method involves studying drugs in small groups of people to quickly separate winners from duds.
Bringing a new cancer drug to market usually takes more than a decade and tests in thousands of patients, and costs more than $1 billion. Companies can't afford many studies like that and patients can't afford to wait years for potentially life-saving new medicines, said Don Berry, a biostatistician at the University of Texas MD Anderson Cancer Center.
He helped design the novel analytical method used in a study discussed Friday at the San Antonio Breast Cancer Symposium, an international conference on the disease.
Researchers testing a drug usually don't see results until they're all in, to prevent biasing the study. But several years ago, an unusual partnership decided to try a new way. It involves the National Cancer Institute, the Food and Drug Administration, drug companies, dozens of cancer research centers and charitable foundations.
The study, called I-SPY 2, enrolls small groups of women on experimental drugs or combinations, then gives them surgery to see what effect treatment had. The best result is a complete response, where no signs of cancer remain. Each patient's results are analyzed as they come in, and advanced statistical methods are used to calculate probabilities that the drug would help in various situations, depending on which women had a complete response.
"This allows us to learn and adapt from each patient as the study goes on," and results on early participants guide treatment that later participants get, said Dr. Hope Rugo of the University of California, San Francisco. When enough evidence indicates a high probability of success, the drug "graduates" to final-phase testing aimed at winning FDA approval.
On Friday, Rugo gave results on the first of seven drugs being tested veliparib, made by AbbVie Inc., a North Chicago, Ill., company recently spun off from Abbott Laboratories. It is in a new class of experimental medicines called PARP inhibitors, which target an enzyme cancer relies on to grow.
The I-SPY 2 testing suggests that adding the chemotherapy drug carboplatin and veliparib to usual chemo before surgery improved outcomes for women with "triple negative" breast cancer tumors that are not fueled by estrogen, progesterone or the gene that the medicine Herceptin targets.
Up to 20 percent of breast cancers are this type, and they're more common in young women, blacks and Hispanics, and women with certain breast cancer gene mutations.
Researchers were able to determine this after tests in only 71 women. They calculate that tests of only 300 women with triple negative tumors are needed to give a definitive answer, and that the drug has at least a 90 percent probability of success in such patients. If more types of cancer are included, the probability of success drops to 55 percent.
The results show that "we can get early reads on something that is worth pursuing" and bail quickly on treatments that don't help, said Dr. Carlos Arteaga of the Vanderbilt-Ingram Comprehensive Cancer Center in Nashville.
Last week, another company participating in the study, Puma Biotechnology Inc., said its experimental drug neratinib also had "graduated" and would enter a definitive study. Results of the early testing will be presented at a cancer conference next year.
The San Antonio meeting is sponsored by the American Association for Cancer Research, Baylor College of Medicine and the UT Health Science Center..