A European regulatory agency has recommended ado-trastuzumab emtansine (Kadcyla) be approved by the European Medicines Agency for the adjuvant treatment of patients diagnosed with HER2-positive breast cancer, after the successful completion of the phase 3 KATHERINE study. 

Results of the study showed ado-trastuzumab emtansine reduced the risk of invasive breast cancer recurrence or death by 50%, according to a press release from the manufacturer. The study compared the efficacy of ado-trastuzumab emtansine with trastuzumab (Herceptin, Genentech ) for the treatment of patients who have residual invasive disease in the breast and/or lymph nodes who received taxane-based chemotherapy and HER2-targeted therapy before surgery. 

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The KATHERINE study was an international, multi-center,  randomized, open-label trial that included 743 patients treated with ado-trastuzumab emtansine and 743 patients treated with trastuzumab. 

At a median follow-up of 41 months,  88.3% of patients treated with ado-trastuzumab emtansine did not have their cancer return after treatment. By comparison, 77% of patients treated with trastuzumab did not have their cancer return during the same period (HR = 0.5; 95% CI, 0.39-0.64).

“In the early breast cancer setting where cure is achievable, it is important to do everything possible to prevent progression to an advanced, incurable stage,” Levi Garraway, MD, PhD, chief medical officer and head of global product development at the manufacturer, said in the release. 

Garraway called the recommendation from the Committee for Medicinal Products for Humans a “significant step” in bringing what he called a “potentially transformative treatment option” to the European market. 

During the KATHERINE study, 25.7% of patients who received ado-trastuzumab emtansine experienced a grade 3 or higher adverse event compared with 15.4% for trastuzumab. The press release noted that the safety profile in the KATHERINE study was similar to previous studies. The most common grade 3 or higher adverse events included thrombocytopenia (5.7% vs 0.3%) and hypertension (2% vs 1.2%). 

The FDA approved ado-trastuzumab emtansine in May for the treatment of HER2-positive breast cancer with residual invasive disease after neoadjuvant treatment. While the recommendation by the committee does not guarantee approval by the European Medicines Agency, the manufacturer said they anticipate a decision in the “near future.”