Neurocrine Biosciences Announces Positive Findings in Phase I/II Malignant Brain Tumor Clinical Trial.

Business Editors and Health/Medical Writers

SAN DIEGO--(BW HealthWire)--April 19, 2000

Results Confirm Antitumor Activity in Humans With Recombinant

Chimeric Protein, NBI - 3001

Neurocrine Biosciences Inc. (Nasdaq:NBIX) Wednesday announced results from a Phase I/II clinical trial in patients with advanced malignant glioma.

Based on magnetic resonance imaging (MRI) findings reported by the investigators, 56% of patients exhibited a therapeutic response (greater than a fifty percent reduction in tumor size).

No significant peripheral drug-related toxicity was observed. While approximately one third of the patients exhibited side effects during or immediately following therapy, they are consistent with marked tumor cell death and the subsequent inflammatory response resulting from the IL-4 toxin therapy. Based on these results, the company expects to initiate a Phase II clinical study to bridge into a pivotal Phase III efficacy trial.

Thirty-one patients with end-stage (grade 4) recurrent glioblastoma, unresponsive to surgery and radiotherapy, were treated with intratumoral infusions of IL-4 for up to four days in a Phase I/II study conducted at nine leading neurosurgery centers in the USA and Germany. Treating physicians were asked to rate the patients' response to therapy at the last evaluable follow-up visit which ranged from 1-16 months. Twenty-nine of the 31 patients were available for evaluation. Four patients (13%) were reported as having complete remissions (no evidence of viable tumor); 14 patients (48%) experienced a partial response (greater than a 50% reduction in tumor mass). Seven patients (24%) were rated with stable disease, with the remaining four patients (13%) experiencing progressive disease.

"Malignant Brain Tumors are one of the most life-threatening forms of cancer. Preliminary data with IL-4 Fusion Toxin in approximately 40 patients treated to date with recurrent glioblastoma has shown promising anti-tumor effects," said Mitchel S. Berger, M.D., professor and chair of the Department of Neurological Surgery and director of the Brain Tumor Research Center at the University of California San Francisco. "We are hopeful that this new approach may offer better efficacy for localized tumors in the brain and the periphery."

In addition, the company and its collaborators at the National Institutes of Health have been conducting preclinical studies designed to assess NBI-3001 for the treatment of systemic forms of cancer such as colon, breast, prostate, kidney cancers and melanoma. Neurocrine expects to initiate Phase I/II clinical trials in a peripheral form of cancer in second half 2000.

"These findings strongly support a small, earlier study completed under an independent physician-sponsored investigational new drug (IND), and confirm our animal data demonstrating the highly active nature of this exotoxin fusion protein," said Dr. Bruce Campbell, sr. vice president, Development at Neurocrine Biosciences. "Although the data are provisional at this stage, the combination of a striking lack of systemic side effects with a potent intracranial response is extremely encouraging. The unanimous vote among the investigators, to proceed as quickly as possible with further trials, confirms our belief that we may have finally identified a compound capable of effectively treating this lethal form of brain cancer."

While patient enrollment is complete, Neurocrine will continue to maintain patient follow-up from this study and has planned a follow-up bridging study to evaluate enhanced distribution of the drug within tumors. This study will more completely demonstrate the nature of anti-tumor response and is expected to bridge into pivotal Phase III efficacy trials within one year. Neurocrine has been granted "fast track" (Subpart E) status by the Food and Drug Administration (FDA) and looks forward to meeting with the agency shortly to review these results as well as to discuss future clinical studies.

How IL-4 Works

Preclinical data suggest that when infused directly into a glioblastoma, IL-4 Fusion Toxin kills tumor cells but not the healthy brain cells. IL-4 Fusion Toxin is a protein in which a blood cell derived growth factor (IL-4) has been joined with a Pseudomonas exotoxin, a potent toxin that can destroy cells. IL-4 has very high affinity for-IL-4 receptors, which are highly localized on malignant brain tumors, but not on normal brain cells. IL-4 binds tightly to the IL-4 receptors on the surface of the cancer cells and delivers the exotoxin directly into the cell, resulting in cell death. IL-4 Fusion Toxin is administered via a special catheter that permits delivery directly into the brain tumor.

Neurocrine is collaborating with Medtronic, a leading drug delivery company and manufacturer, to develop a proprietary delivery system for administration of the drug directly into malignant brain tumors using Medtronic's SynchroMed(TM) Infusion System. This state of the art delivery system may allow continuous saturation of the tumor without repeat procedures or treatments.

Neurocrine Biosciences is a leading neuroscience company focused on the discovery and development of novel therapeutics for neuropsychiatric, neuroinflammatory and neurodegenerative diseases and disorders. The company's neuroscience, endocrine and immunology disciplines provide a unique biological understanding of the molecular interaction between central nervous, immune and endocrine systems for the development of therapeutic interventions for anxiety, depression, insomnia, stroke, malignant brain tumors, multiple sclerosis, obesity and diabetes.

Neurocrine Biosciences Inc. news releases are available through the company's Web site via the Internet at http://www.neurocrine.com.

In addition to historical facts, this press release may contain forward-looking statements that involve a number of risks and uncertainties. Among the factors that could cause actual results to differ materially from those indicated in the forward looking statements are risks and uncertainties associated with Neurocrine's IL-4 Fusion Toxin research and development program including, but not limited to, risks and uncertainties associated with, or arising out of, clinical development including risk that IL-4 Fusion Toxin Product candidate, will not successfully enter early clinical trials for systemic forms of cancer proceed through additional glioblastoma clinical trials or that in later stage clinical trials will not show that it is effective in treating any forms of cancer; determinations by regulatory and governmental authorities, uncertainties relating to patent protection and intellectual property rights of third parties; impact of competitive products and technological changes; availability of capital and cost of capital; and other material risks. A more complete description of these risks can be found in the company's Form 10K for Dec. 31, 1999. Neurocrine undertakes no obligation to update the statements contained in this press release after the date hereof.