Cubist Pharmaceuticals Inc. (CBST) is a biopharmaceutical company focused on the research, development, and commercialization of antibacterial therapies targeting serious infections in acute care hospital settings, including Gram-positive and Gram-negative pathogens such as MRSA and Clostridium difficile; its core products include Cubicin (daptomycin), a lipopeptide antibiotic for Staphylococcus aureus bacteremia and complicated skin infections, Entereg (alvimopan) for accelerating gastrointestinal recovery post-surgery, co-promoted Dificid (fidaxomicin) for C. difficile infections, and late-stage assets like Zerbaxa (ceftolozane/tazobactam), Sivextro (tedizolid), and ceftolozane/tazobactam combinations. Founded in 1992 and headquartered in Lexington, Massachusetts, with international operations in Zurich, Switzerland, the company serves global hospital acute care markets, emphasizing unmet needs in antibiotic resistance through innovative anti-infectives and partnerships. In recent years, Cubist completed acquisitions of Trius Therapeutics and Optimer Pharmaceuticals in 2013 for approximately $1.6 billion to bolster its Gram-positive and C. difficile portfolios; launched Sivextro (tedizolid) following FDA approval in June 2014; and became a wholly owned subsidiary of Merck & Co., Inc. in January 2015 after a $9.5 billion transaction, integrating its antibiotics leadership into Merck's hospital acute care division while maintaining operations as Cubist Pharmaceuticals LLC.