On April 6, 2011, Cubist announced that it has inked an exclusive two-year agreement with Optimer Pharmaceuticals Inc. to co-promote Dificid (fidaxomicin) in the US for the treatment of Clostridium difficile infection (CDI), which is also known as Clostridium difficile-associated diarrhea (CDAD). The drug was approved by the FDA in May 2011.

In exchange for its efforts in co-promoting Dificid, Cubist will be entitled to quarterly service fees of $3.75 million ($15 million per year) over the two-year period beginning from the year of first commercial sale. Cubist will also receive additional fees of $5 million in the first year and $12.5 million in the second year should sales exceed an unspecified target. Cubist can also get a percentage of gross profits should sales go beyond these targets.

Though the agreement is scheduled to terminate two years after the first commercial sale of Dificid, it can be renewed or terminated earlier upon agreement by the two companies.

Optimer intends to market the drug to physicians, hospitals, long-term care facilities and other healthcare institutions with the help of Cubist’s existing US hospital sales force and medical affairs team who are experienced in marketing Cubicin.

Cubist’s sole marketed product Cubicin, faces fierce competition from drugs marketed for the same indication.

Cubist is heavily dependent on Cubicin. The pipeline candidates are either in early-stage or mid-stage development. Consequently, if Cubicin suffers a setback then it would have an adverse impact on the company’s shares.