US drug maker Merck & Co has called off its association with Ranbaxy Laboratories that it had struck to develop anti-infective medicines, which could have fetched the Indian firm $100 million over a period of five years.

The termination of the near three year old alliance was confirmed by both Ranbaxy and MSC Pharmaceuticals, the Indian affiliate of US-based Merck & Co Inc. However the companies refused to divulge details or reasons for ending the pact.

The agreement between Merck and Ranbaxy was signed in May 2008, a month ahead of the billionaire promoters Malvinder and Shivinder Singh selling their stake in Ranbaxy to Daiichi Sankyo.

A Ranbaxy spokesperson said the agreement had been called off but details could not be given.

The pact could have seen the Indian firm net $100 million over a period of five years.

Under the agreement, Ranbaxy and Merck were to jointly work on development of  clinically validated anti-bacterial and anti-fungal drug candidates.