Roche announced Thursday that the Phase III APHINITY study met its primary endpoint, showing that adjuvant treatment with the combination of Perjeta (pertuzumab), Herceptin (trastuzumab) and chemotherapy achieved a significant reduction in the risk of recurrence of invasive disease or death in people with HER2-positive early breast cancer compared to Herceptin and chemotherapy alone. Shares in the company rose as much as 6.9 percent on the news.

The trial randomised 4805 people with operable HER2-positive early breast cancer who had undergone surgery to receive either: six to eight cycles of chemotherapy with Perjeta and Herceptin, followed by Perjeta and Herceptin every three weeks for a total of one year of treatment; or six to eight cycles of chemotherapy with placebo and Herceptin, followed by placebo and Herceptin every three weeks for a total of one year of treatment. Along with the main goal, secondary endpoints of the study include cardiac and overall safety, overall survival, disease-free survival and health-related quality of life.

Chief medical officer Sandra Horning said "we look forward to discussing these adjuvant results with global regulatory authorities," including the FDA and European Medicines Agency. Roche added that full results from the APHINITY trial will be presented at a medical meeting this year.

The combination of Perjeta, Herceptin and chemotherapy is currently approved as a neoadjuvant treatment for people with HER2-positive early breast cancer in more than 75 countries worldwide, including the US and Europe. Herceptin generated sales of around 6.8 billion Swiss francs ($6.7 billion) last year, although the drug could face competition as early as this year in Europe from a biosimilar version from Mylan and Biocon. Meanwhile, revenue from Perjeta reached 1.8 billion francs ($1.8 billion) in 2016.

Commenting on the study results, Citi analyst Andrew Baum estimated that the positive findings would add as much as $2 billion a year to Perjeta sales. "Current Herceptin monotherapy treatment is already highly successful and represents a high hurdle to beat which makes the positive APHINITY outcome all the more impressive," noted analysts at Jeffries. However, the analysts cautioned that "for the Perjeta/Herceptin combination to become widely used as a new standard of care, we will likely need to see a strong clinical benefit demonstrated by the data, as well as the statistically significant benefit."

According to Jefferies' analyst Jeffrey Holford, results will need to show that 92 percent to 94 percent of women in the trial who received the combination of Perjeta, Herceptin and chemotherapy lived at least three years without breast tumours returning in order to gain wide usage. Holford noted that Herceptin and chemotherapy alone have shown a three-year disease-free survival rate of up to 90 percent. Holford explained that the size of the improvement will be important, because at current prices, adding Perjeta to Herceptin and chemotherapy more than doubles the cost of treatment to about $10 000 per month.