Merck KGaA has begun a late-stage trial of its investigational Stimuvax vaccine as a potential treatment for patients with advanced, inoperable breast cancer.

The German company, which is co-developing Stimuvax with the USA’s Oncothyreon, noted that the Phase III trial, called STRIDE, will look at whether the vaccine can extend progression-free survival in patients treated with hormonal therapy. Some 900 patients with advanced breast cancer will be enrolled at an estimated 180 sites in over 30 countries.

Principal investigator Lawrence Shulman noted that “advanced-stage breast cancer remains a devastating and challenging disease and we urgently need new treatment options”. He added that if the STRIDE study proves positive, “this could make a difference for patients with hormone receptor positive metastatic breast cancer.”

Stimuvax, which is also being tested for non-small cell lung cancer in Phase III, stimulate the body’s immune system to identify and target cancer cells that express MUC1, an antigen commonly expressed in breast cancer as well as in NSCLC, multiple myeloma and colorectal, prostate and ovarian cancers.

News of the trial provided a big boost to Oncothyreon’s share price, and Simos Simeonidis, an analyst with Rodman & Renshaw, said the fact that Merck, “one of the most sophisticated players in oncology”, is investing in a second large trial with Stimuvax, “speaks to the company’s confidence about the programme”. This is especially interesting, given that it decided to go into the breast cancer trial before preliminary data from the Phase III study in lung cancer were available, he noted.

Mr Simeonidis added that Oncothyreon “is an underappreciated and interesting small cap biotech story that is still under most investors’ radar screens”.