Final results of a large clinical trial indicate that Genentech’s antibody Perjeta dramatically increases survival times for women with late-stage cancer, but at a steep price.

Use of the drug pertuzumab (Perjeta) extended survival for women with late-stage, HER2-positive breast cancer who had not received previous treatment by nearly 16 months over standard care, the drug’s maker Genentech announced this weekend.

Women treated with the approved drug Herceptin and docetaxel chemotherapy lived 41 months, while those who also received pertuzumab lived 57 months, according to the final, long-term results of pertuzumab’s Phase III clinical trial.

“Adding Perjeta to treatment with Herceptin and chemotherapy resulted in the longest survival observed to date in a clinical study of people with HER2-positive metastatic breast cancer,” said Dr. Sandra Horning, chief medical officer at Genentech. 

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Preliminary results from the same study, dubbed CLEOPATRA, were enough to win the Food and Drug Administration’s approval for the drug for use in women with late-stage HER2-positive cancer in 2012. Late last year, pertuzumab was OK’d for use before surgery in patients with early-stage HER2-positive breast cancer.

Pertuzumab, a genetically engineered antibody, specifically targets HER2-positive breast cancers. These patients are considered higher risk because the HER2 protein, from which the cancer type takes its name, boosts cancer cell growth and survival. HER2-positive tumors affect about 20 percent of breast cancer patients.

“As one of the investigators on this study, it is personally very exciting to see this result,” said Dr. Paula Klein, an assistant professor at the Icahn School of Medicine at Mount Sinai in New York. “This prolongation of survival is unprecedented, particularly in this group of patients with higher risk disease.”

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But, Klein noted, the drug will be expensive.

“This benefit also comes from no significant increase in toxicity,” she said. “Unfortunately, it does come with a financial toxicity given the expense of dual antibodies.”

According to industry publication FiercePharma, brand-name Perjeta carries a price tag of $5,900 a month, or about $71,000 a year.

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