Cubist Pharmaceuticals is the latest company to hit the acquisition trail and is buying fellow US firm Calixa Therapeutics to boost its antibiotics portfolio.

Under the terms of the deal, Cubist is forking out $92.5 million in cash and will pay up to $310 million more in regulatory, and commercial milestones related to privately-held Calixa’s CXA-101, an anti-pseudomonal cephalosporin that was acquired from Astellas Pharma. The latter is in Phase II trials for complicated urinary tract infections and is also being tested in combination with tazobactam.

That combo, known as CXA-201, is being developed as a first-line intravenous therapy for the treatment of certain serious Gram-negative bacterial infections in the hospital, including those caused by multi-drug resistant Pseudomonas aeruginosa. The companies say that CXA-201’s demonstrated potency against P. aeruginosa gives it “a highly differentiated profile versus marketed antibiotics”.

Cubist chief executive Michael Bonney said that if successfully developed and launched, “we believe that CXA-201 would be a potent weapon in the treatment of serious infections” and play a similar role to its already-marketed Gram-positive therapy Cubicin (daptomycin). The latter is approved for the treatment of complicated skin infections and bacteremia caused by MRSA.

The deal comes a week after Celgene Corp agreed to acquire Gloucester Pharmaceuticals in a deal valued at around $640 million.