Awaited breast cancer drugs coming to market
Awaited breast cancer drugs coming to market
Tamoxifen and herceptin could break new ground
With one drug aimed at prevention and the other at treatment, the federal Food and Drug Administration’s Oncologic Drugs Advis ory Committee has unanimously approved two breast cancer agents: tamoxifen and herceptin. Both drugs, touted as potential breakthroughs in fighting the disease, were approved on the same day in early September. Herceptin was given full approval Sept. 25; tamoxifen is expected to receive final approval well before the end of the year.
Tamoxifen was already on the market as Nolvadex by Wilmington, DE-based Zeneca for prevention therapy against the recurrence of breast cancer. The panel has approved tamoxifen for a new indication as a prevention therapy for healthy — but high-risk — women. The potentially dangerous side effects of tamoxifen, however, led the FDA to propose development of educational materials to help prescribers and patients alike assess whether the drug is appropriate. The educational materials will be developed by Zeneca and the National Cancer Institute (NCI), which helped fund clinical trials and supported the new indication. Harmful side effects from the clinical trials included a number of patients developing endometrial cancer, blood clots in the lungs, and cataracts.
The remaining open question on tamoxifen is whether it is capable of preventing breast cancer. The long-term viability has yet to be determined because the NCI-sponsored trial recently completed its four-year period.
The trial involved 13,388 women, given either the drug or placebo. After four years, 85 patients taking tamoxifen developed breast cancer, compared with 154 on placebo, an inferred breast cancer reduction rate of 45%. But 33 patients taking tamoxifen also developed endometrial cancer, compared with 14 on placebo, while 17 on tamoxifen developed blood clots in their lungs, vs. six on placebo.
As one of the first drugs in history to be marketed for cancer prevention, tamoxifen is being anticipated as highly as herceptin, which itself opens new doors in the advances of tailoring drugs to attack molecular structures and cancer-causing genes.
Herceptin: Few side effects
Specifically indicated to attack breast cancer caused by an overproduction in some patients of the HER-2/neu protein that promotes tumor growth, herceptin also is being praised for its lack of toxic side effects common in other chemotherapy drugs. Common side effects to those drugs include hair loss and lowered blood counts. An estimated 25% to 30% of metastatic breast cancer in patients is attributed to overproduction of HER-2. Herceptin is manufactured by Genentech in South San Francisco, CA.
A monclonal antibody, herceptin is indicated as a combination therapy with the chemotherapy agent TAXOL (paclitaxel injection) as a first-line treatment or as a single-agent therapy in cases of chemotherapy failure. The drug works by binding to the HER-2 protein on a cell’s surface, thwarting incoming signals to replicate.
Works best with TAXOL
In trials, the drug worked best in combination with TAXOL, decreasing measurable breast cancer in 48% of patients, compared with 32% on chemotherapy agents alone, for a 50% better response rate. The use of herceptin with adriamycin and cytoxin resulted in a 20% increase in effectiveness, compared with using the two drugs without herceptin.
And like the unanswered questions about the long-term effects of tamoxifen, research is continuing into the possible threats that a herceptin chemotherapy regimen may have on a patient’s heart.
[For additional information on tamoxifen, contact Zeneca Pharmaceuticals, 1800 Concord Pike, Wilmington, DE 19803. Telephone: (302) 886-2231.
For more information on herceptin, contact Genentech, One DNA Way, South San Francisco, CA 94080. Telephone: (800) 821-8590.]
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