Ligand Pharmaceutical will buy Pfenex to add the latter’s protein expression technology to its core drug discovery and formulation business. The deal – worth $516 million – is expected to complete before the end of the year. Ligand cited Pfenex’s expression technology as a major motivation for the deal, pointing out it is out-licensed for numerous commercial and development-stage programs. CEO John Higgins likened the deal to Ligand’s acquisition of the technology Captisol – gained when the firm bought Cydex…