Cubist Pharmaceuticals, long-seen as a takeover target itself, has hit the acquisition trail and is buying Trius Therapeutics and Optimer Pharmaceuticals in deals worth over $1.60 billion.

First up, Cubist is paying $13.50 per share in cash, or $707 million, to get hold of Trius, plus potentially another $2 per share through a contingent value right (CVR), valuing the total transaction at up to $818 million. The CVR will be primarily redeemable depending on the success of Trius' late-stage antibiotic tedizolid (TR-701), which is in development for the treatment of certain Gram-positive infections, including methicillin-resistant Staphylococcus aureus (MRSA).

Tedizolid met all primary and secondary endpoints in two Phase III trials studying patients with acute bacterial skin and skin structure infections and will be submitted to the US Food and Drug Administration during the second half of the year and in Europe in the first half of 2014. The drug is partnered with Bayer outside North America and the European Union.

An antibiotic is also at the heart of the Optimer purchase, namely Dificid (fidaxomicin), which Cubist already co-promotes. The latter is paying $10.75 per share in cash, or $535 million, and this deal also has a CVR element worth up to $5.00 depending on Dificid sales. That would value the transaction at up to $801 million.

In May 2011 Dificid became the first antibacterial approved by the FDA in more than 25 years to treat Clostridium difficile-associated diarrhoea. Second-quarter 2013 sales reached $19 million, up 13% on the first quarter and Cubist notes that the CDAD market is large, with over 700,000 cases annually in the USA alone; in Eurpope, the drug is known as Dificir and is partnered with Astellas.