The FDA has approved a drug for a rare form of skin cancer that was developed in part by researchers at an EMD Serono facility in Billerica.

The agency announced Thursday afternoon that it had approved avelumab, the first-ever treatment for metastatic Merkel cell carcinoma. The drug was jointly developed by German drugmaker Merck KGaA and Pfizer (NYSE: PFE), and will be sold by the companies as Bavencio. EMD Serono, based in Rockland, is the biopharma arm of Merck KGaA in the U.S. and Canada.

Bavencio…