The drug, approved last Friday in the U.S. along with a companion diagnostic test for just a small subset of lung cancer patients, epitomizes drugmakers' new strategy of developing very expensive but effective medicines for the few to replace the blockbusters for the masses now getting generic competition.
It's also part of the long-awaited advent of personalized medicine, in which doctors identify patients with gene changes or variations that fuel their disease and then try to match them with new medicines that specifically target those genes.
"This is a paradigm shift," Dr. Paul A. Bunn Jr., a University of Colorado professor and cancer researcher involved in testing Xalkori, told journalists during a conference call hosted by Pfizer. "It used to be that everybody with cancer was treated the same" with surgery and chemotherapy.
Xalkori, a pill with relatively minor side effects compared to traditional infused chemotherapy, was approved for the roughly 4 percent of patients with non-small cell lung cancer who have what's called the ALK fusion gene.
This change occurs when ALK, short for anaplastic lymphoma kinase, and another gene on the same chromosome rearrange their positions and fuse together. That turns the ALK gene on constantly, fueling cancer cell growth. Xalkori works by blocking the kinase enzyme, key to that process.
About 6,000 Americans a year develop this cancer, Pfizer said. Those patients, called ALK positive, now can be identified with a $250 molecular diagnostic test developed by Pfizer's partner, Abbott Molecular Oncology, and also approved last Friday.
In Pfizer-funded early and midstage studies that led to Xalkori's approval, just over half of patients had their tumors disappear, shrink or stop growing for nearly two years on average. Research to determine overall survival is ongoing.
By comparison, nonsmall cell lung cancer - about 85 percent of cancer cases - usually isn't diagnosed until it has spread, is tough to treat and kills nearly 95 percent of patients within five years. Lung cancer is the top killer among cancers worldwide.
Xalkori, known chemically as crizotinib, costs about $9,600 a month and is taken until it stops fighting tumors, at which point patients likely would be put on older chemo drugs they hadn't taken yet. Pfizer has started a Xalkori patient assistance program with a maximum $100 monthly copayment for insured patients meeting certain financial limits.
Pfizer is currently running two late-stage studies that compare Xalkori to different chemotherapy treatments that have been the standard of care. It's unusual to get approval before completing such large, late-stage studies. Xalkori was approved remarkably quickly, just four years after Japanese researchers reported they had identified the ALK gene variation.
Pfizer is awaiting approval from regulators in the European Union, Switzerland, Japan and Korea, and also is testing crizotinib against other types of cancer.
Pfizer said 3 percent to 5 percent of patients with nonsmall cell lung cancer have the ALK gene fusion. But one research group presented data at a recent cancer conference showing 8 percent of those patients have it.
Pfizer needs some big sellers because its $10.7 billion-a-year cholesterol fighter, Lipitor, the world's top-selling drug, loses U.S. patent protection on Nov. 30. That starts an unprecedented wave of much-cheaper generic versions of many drugs taken daily by millions.
On the Web: www.xalkori.com