Astellas and partner Optimer Pharmaceuticals are celebrating after regulators in Europe gave the green light to their antibiotic Dificlir.

The European Commission has approved Dificlir (fidaxomicin) for the treatment of Clostridium difficile infections, which can cause severe diarrhoea. The thumbs-up is based on two Phase III trials which compared the drug with oral vancomycin, a common antibiotic used to treat CDI.

The data showed that Dificlir was as effective as vancomycin in treating CDI and had a significantly lower rate of recurrence (including relapses) compared to vancomycin in the 30 days following treatment. Some 1,1164 patients were involved in the studies.

The first-in-class macrocyclic antibiotic was approved in the USA in May, where it is sold as Dificid and has got off to a reasonable start. It posted sales of $10.6 million for its first quarter on the market across the Atlantic.

Pedro Lichtinger, Optimer's chief executive, said the European approval is "a key step in making fidaxomicin more widely available to patients across the globe to treat this very serious disease". He added that "we believe we have obtained a very strong label recognising the benefits of Dificlir".

The approval was expected, given that European Medicines Agency's  Committee for Medicinal Products for Human Use recommended its authorisation in September. Then, the EMA noted that the potential cost of C difficile infection per year in the European Union has been estimated to be as high as 3 billion euros.

Astellas bagged the rights to Dificlir in Europe, theMiddle East, Africa and the Commonwealth of Independent States in a deal signed in February this year. The Japanese drugmaker paid an upfront fee of $68 million and the alliance could be worth over $220 million to Optimer.