SAN FRANCISCO – Atop its eye-opening $450 million financing earlier this month, Moderna Therapeutics Inc. stacked another $50 million from Merck & Co. Inc. as well as an equity investment of $50 million from the pharma giant in a three-year license and collaboration deal that gives Merck rights to commercialize five product candidates that could come from the arrangement, designed to explore vaccines and passive immunity treatments against viral diseases using modified messenger RNA (mRNA).