The drug-services firm Catalent is buying MaSTherCell, a cell therapy manufacturing specialist based in Gosselies, Belgium, for $315 million. MaSTherCell operates a clinical-scale facility in Gosselies. A commercial-scale plant under construction will more than double the site’s staff of 240. MaSTherCell is also building a facility in Houston that will employ about 50 when it opens later this year. Catalent entered the adjacent gene therapy service market last year with its $1.2 billion acquisition of Paragon Bioservices.