Phase III Trial Shows Tripartite Chemotherapy More Effective for Treating HER2 Positive Metastatic Breast Cancer

Results of the CLEOPATRA (CLinical Evaluation of Pertuzumab and TRAstuzumab) phase III clinical trial showed that the combination of pertuzumab, Herceptin (trastuzumab), and docetaxel was more potent than the duo comprising Herceptin and docetaxel for the treatment of HER2-positive metastatic breast cancer (mBC).

The results, which are to be published at an upcoming medical conference, were recently released by Roche (Basel, Switzerland).

Pertuzumab is a monoclonal antibody that functions as a HER2 dimerization inhibitor. HER dimerization is believed to play an important role in the growth and formation of several different cancer types, and pertuzumab is the first investigational medicine developed to prevent specifically the HER2 receptor from pairing with other HER receptors (EGFR/HER1, HER3, and HER4).

Herceptin is a monoclonal antibody designed to target and block the function of HER2 by activating the body’s immune system and suppressing HER2 to target and destroy the tumor. Herceptin has been shown to improve response rates, disease-free survival, and overall survival while maintaining quality of life in women with HER2-positive breast cancer. The mechanisms of action of pertuzumab and Herceptin are believed to complement each other as both bind to the HER2 receptor but at different sites.

Docetaxel is a synthetic derivative of the naturally occurring compound paclitaxel. Like paclitaxel, docetaxel promotes the formation of microtubules that do not function properly. One of the roles of normal microtubules is to aid in cell duplication, and by disrupting this function, docetaxel inhibits cell reproduction.

The CLEOPATRA study was a phase III, randomized, double-blind, placebo-controlled clinical study that evaluated the efficacy and safety profile of pertuzumab combined with Herceptin and docetaxel chemotherapy compared to Herceptin and docetaxel in people with HER2-positive mBC. It comprised a population of 808 people with previously untreated HER2-positive mBC from 19 countries worldwide. The patients were treated with either the combination of pertuzumab, Herceptin, and docetaxel or with only Herceptin and docetaxel.

Results of the study revealed that patients receiving the tripartite treatment lived significantly longer without their disease getting worse than did those who received only Herceptin and docetaxel. Severity of side effects was consistent with that seen in previous studies of pertuzumab and Herceptin, either in combination or alone.

“These results with pertuzumab combined with Herceptin and docetaxel are very encouraging and represent our commitment to developing potential new personalized options for people with this aggressive disease,” said Dr. Hal Barron, chief medical officer at Roche. “We plan to submit the study results for global regulatory approval this year.”

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