New York-based Pfizer has informed Neurocrine Biosciences it is terminating a collaborative agreement to develop and promote the insomnia drug indiplon, the company announced June 22, just days after it was revealed the drug may need to undergo more clinical trials.

Pfizer and Neurocrine entered into the agreement in 2002, which called for worldwide commercialization of the drug. The plan hit a snag last month, however, when the company received a not approvable letter for the 15-mg extended release tablet and an approvable letter for the 5-mg and 10-mg immediate release doses. At the time, Albert Rauch, a healthcare analyst with the investment firm AG Edwards, said the uncertain fate of the extended release tablet put in question Pfizer's incentive to stay in the deal.

The future of the drug became even murkier on June 15, when Neurocrine announced that satisfying the FDA questions about indiplon would require new data and that it had requested a meeting with the agency to determine if additional preclinical or clinical studies were needed.