After Tesaro buy, GSK wades deeper into cancer unveiling big immunotherapy deal with Germany's Merck

GSK is muscling its way into the cancer big leagues, months after agreeing to shell out $5 billion for cancer drugmaker Tesaro. On Tuesday, the British drugmaker said it would co-develop a fusion protein immunotherapy — designed to offer fresh ways to fight difficult-to-treat cancers beyond the existing PD-1/PD-L1 class — with Germany’s Merck KGaA in a deal valued up to about $4.2 billion.