New Class of Drugs in Early Trials Offers Hope for Breast Cancer

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ORLANDO, Fla. -- A new class of drugs under development at several pharmaceutical companies showed promise in early studies against two types of especially tough-to-treat breast cancer.

The compounds, known as PARP inhibitors, work by obstructing the ability of cells damaged by chemotherapy or through genetic mutations to repair themselves, causing tumor cells to die as a result.

One of the agents being developed by a unit of Sanofi-Aventis SA, called BSI-201, prolonged survival by 3½ months, to 9.2 months, when added to a standard regimen of chemotherapy in a study of 116 women with so-called triple-negative breast cancer that had spread to other parts of the body. Such women lack receptors on their tumors for the hormones estrogen, progesterone and the protein HER2, each of which are targets for many current therapies.

The other drug, known as olaparib, is under development atAstraZenecaPLC. In a nonrandomized study of 52 women with cancer caused by mutations in genes known as BRCA1 and BRCA2, the agent given alone caused tumors to shrink significantly in as much as 41% of participants. The inherited form of breast cancer often afflicts young women with an aggressive form of the disease.

The studies were among several featured presentations Sunday at the annual meeting of the American Society of Clinical Oncology in Orlando. Advances in cancer vaccine therapies and a study showing the breast cancer drug Herceptin helps certain patients with gastric cancer were among other developments with the potential to change cancer care.

Oncologists cautioned that the PARP-inhibitor data need to be confirmed in much larger trials. There isn't any expectation that the drugs will cure patients with advanced disease, and it is likely to be several years before one such agent reaches the market. Still, doctors were encouraged by prospects of new treatments for these patients for whom current treatments typically come up short. "This is one of the most exciting findings in a long time," said Eric P. Winer, director of the breast oncology center at Dana Farber Cancer Institute, Boston, who isn't involved with the trials. In both studies, side effects from the compounds were limited, researchers said.

Merck& Co. andAbbott Laboratoriesare among other drug companies with PARP inhibitors in development. The hope is to capitalize on a weakness in some tumors in which their ability to repair their own DNA is already compromised. Tumor and normal cells alike have redundant systems to handle the crucial task of DNA repair, enabling most cells to survive even if one such system is shut down. Hitting already compromised tumor cells with PARP, though, appears to push them over the edge and causes them to die, researchers said.

In other studies, researchers reported that a vaccine derived from a biopsy of a patient's own tumor, combined with an immune system stimulant, enabled patients with a cancer known as follicular non-Hodgkin's lymphoma to live about 44 months free of their disease compared to 30 months for patients given an immune-system stimulant but without the vaccine. Patients were only eligible for the vaccine if their disease was in remission after chemotherapy treatment.

Researchers said the findings are "a milestone" in the decades-long effort to harness the power of the body's immune system in the fight against cancer. "To know that you can use the immune system to treat cancer is progress," said Stephen J. Schuster of the University of Pennsylvania and lead author of the study. "This gives us confidence that we're on the right track." Biovest International Inc., Worcester, Mass., which licensed the vaccine technology from the National Cancer Institute, funded the eight-year study.

Still, a host of challenges, including how to incorporate growing scientific knowledge about immune system traits, need to be met before vaccines are likely to play an important role in cancer therapy, researchers said.