KENILWORTH, N.J. — Merck & Co. said Monday it will acquire Cubist Pharmaceuticals Inc. for $8.4 billion. The transaction will include $1.1 billion in net debt (based on projected cash balances) and other considerations for a total transaction value of about $9.5 billion.

"Cubist is a global leader in antibiotics and has built a strong portfolio of both marketed and late-stage pipeline medicines," said Merck chairman and chief executive officer Kenneth Frazier. "Combining this expertise with Merck’s strong capabilities and global reach will enable us to create a stronger position in hospital acute care while addressing critical areas of unmet medical need, such as antibiotic resistance."

Cubist CEO Michael Bonney described the deal as an opportunity to accelerate that company’s leadership in antibiotics and while delivering value to shareholders. "We have a deep respect for Merck, and it is clear that they share our commitment to addressing the growing global problem we are facing in combating antibiotic-resistant bacteria," he said. "Under Merck’s robust commercial platform, global reach and scientific expertise, we believe Cubist’s programs can thrive. We’re proud of the company that our team has built and are confident that Cubist’s important mission and focus on significant unmet medical needs will continue."

Cubist’s antibiotic Cubicin is the only approved once-a-day therapy for both S. aureus bacteremia and complicated skin and skin structure infections (cSSSI). It has been used to treat more than 2 million patients and continues to be an important therapy in the acute care environment. Company officials say that Cubist’s in-line and late-stage pipeline of anti-infective medicines, including Zerbaxa, which is pending approval from the Food and Drug Administration, will enhance Merck’s hospital acute care business in various therapeutic areas, including Gram-positive and Gram-negative multi-drug resistant infections.

Merck officials say that Cubist complements Merck’s strategy and the global initiative it launched last year, particularly in the area of sharpening its commercial focus on key therapeutic areas that have the potential to deliver the greatest return on investment.