San Diego-based Ambrx, a venture backed biopharmaceuticals firm, said this morning that it has entered into a deal with Merck. Ambrx said the deal with Merck is to design and develop rationally optimized biologic drug conjugates based on Ambrx's site-specific protein medicinal chemistry technology. Ambrx said the deal includes a $15M, upfront payment, and up to $288M in milestone payments for successful discovery, development, and commercialization.