Amgen Inc. will expand its collaboration with Merck on research seeking a cure for a special type of head and neck cancer, the company announced Friday. The Thousand Oaks biotech and Merck, based in Kenilworth, N.J., plan to launch a Phase 1 trial on patients with recurrent or metastatic squamous cell carcinoma of the head and neck, which begin in mucus cells. The study will combine Keytruda, a Merck drug, and talimogene laherparepvec, an investigational drug from Amgen. Both drugs trigger anti-tumor immune responses from the body. “We hope these trials will provide us with insights on the combination of these therapies for patients with this form of cancer for whom treatment options are currently limited,” Dr. Sean Harper, executive vice president of research and development at Amgen, said in a statement. In addition, the two companies will work together on a global Phase 3 study of the drug combination to treat melanoma, a rare but lethal form of skin cancer. Shares closed down $1.09 or less than 1 percent to $156.26 on the Nasdaq.