As we discussed here yesterday, ixabepilone, a semi-synthetic anticancer drug derived from a soil bacterium was up for review by the US Food and Drug Administration (FDA). Just over a half hour ago the manufacturer, Bristol-Myers Squibb, announced that the drug has indeed been approved for the treatment of advanced breast cancer. The drug will be sold under the trade name, Ixempra.

“Previously, patients with aggressive metastatic or locally advanced breast cancer no longer responding to currently available chemotherapies had limited treatment options,” said Linda Vahdat, M.D., Associate Professor of Clinical Medicine and Associate Attending Physician, New York-Presbyterian Hospital/Weill Cornell Medical Center. “The approval of IXEMPRA means that we now have an important new option for patients with metastatic breast cancer who have rapidly progressed through currently approved chemotherapies.”

Ixabepilone is a chemically-modified form of a natural product called epothilone B. The epothilones have been studied widely, both in their natural form and with modifications intended to improve their duration of action in the body. Ixabepilone is an unusual drug at a time when companies are trumpeting “targeted therapies.” This approach, to find one drug that selectively targets one enzyme, has had limited success across cancers but can be very effective for patients with specific subsets of a given cancer. Ixabepilone is still a targeted therapy, primarily by preventing microtubule depolymerization in cancer cells, but it then triggers a series of events that lead to cell death. (In fact, I have yet to hear a convincing argument as to why some anticancer drugs are considered “targeted” while others are not.). Most importantly, ixabepilone continues to kill cancer cells that have grown resistant, or unresponsive, to other chemotherapeutic agents.

Of course, the drug is not without liabilities and can cause bone marrow suppression, peripheral neuropathy, and, in rare cases, cardiac impairment. The good news is that most of these side effects can be managed. But only time will tell how widely effective this drug will be across more diverse and less controlled patient populations than those enrolled in clinical trials.

Over the last decade, I have had the pleasure of knowing a great many chemists and pharmacologists at various academic institutes and pharmaceutical companies involved in the development of various epothilones, natural and synthetic. Seeing ixabepilone to market is a triumph for all in the field of natural products research and, most importantly, a new lifeline for patients with advanced breast cancer.