Neurocrine Biosciences Updates Status of NBI-34060 for the Treatment of Insomnia

San Diego, CA - May 10, 2001

Neurocrine Biosciences, Inc. today announced the Company has completed enrollment in its Phase II transient and chronic insomnia clinical trials with NBI-34060 and is expected to report results at the end of June 2001.

In addition, the company reported the initiation of multiple dose ranging and efficacy based clinical trials for its immediate and modified release formulations, the results of which will be released during the year.

Based on the results of these studies, the company is expecting to move into multiple Phase III clinical trials beginning in September.

NBI-34060, through the combination of its two formulations, will address all aspects of transient and chronic primary insomnia. The immediate release formulation will address difficulties associated with sleep initiation and middle of the night awakenings whereas, the modified release tablet will treat patients who suffer from sleep maintenance insomnia as well as those who have the combination of sleep initiation and sleep maintenance problems.

The NBI-34060 Phase II transient insomnia clinical trial is a randomized, multi-center, double blind, placebo controlled, single dose, dose response study. The trial enrolled 331 subjects 18-64 years old. The primary endpoint of the study is latency to persistent sleep, the FDA endpoint for approval. A similar trial involving 227 subjects was successfully completed and reported in December 1999, which demonstrated a statistically significant and clinically relevant signal sedative hypnotic effect.

The NBI-34060 chronic insomnia trial was designed to evaluate the sedative hypnotic effects and safety of four dose levels of NBI-34060 relative to placebo and Ambien™ in adult patients with chronic insomnia. The study is a randomized, multi-center, double blind, placebo and active controlled, dose response study in patients with DSM IV (Diagnostic Statistical Manual of Mental Disorders) diagnosis of chronic insomnia. The trial involved 59 patients and is a six-way crossover study representing 472 nights of treatment with NBI-34060.

The company is continuing to enroll in a Phase II dose ranging study in elderly patients with chronic insomnia. The study design is intended to evaluate the sedative hypnotic effects and safety of three dose levels of NBI-34060 relative to placebo in elderly patients with chronic insomnia. The trial will enroll 44 patients aged 65 - 85 years old and is expected to complete enrollment in the 3rd Quarter.

Results of a previously reported Phase II clinical trial comparing NBI-34060, Ambien™ and zopiclone relative to placebo during Middle of the Night (MOTN) dosing demonstrated that NBI-34060 does not lead to next-day hangover effects while both Ambien™ and zopiclone exhibited statistically significant effects on residual sedation. Also, results of pharmacokinetic studies demonstrated that NBI-34060 produces sedative hypnotic effects.

In addition, these studies demonstrated no major differences in the pharmacokinetics between young adults and elderly subjects nor have significant differences in the pharmacokinetics between males and females been observed. To date the company has successfully completed 14 clinical studies involving over 830 subjects and based on preliminary data are preparing for pivotal Phase III trials for NBI-34060 starting in Q3 2001.