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New Orleans, May 23, 2000 - Amgen (NASDAQ: AMGN) and PRAECIS PHARMACEUTICALS (NASDAQ: PRCS) today announced at the annual meeting of the American Society of Clinical Oncology the results of two pivotal, randomized, multi-center phase 3 clinical trials of abarelix-depot-M, the first in a new class of prostate cancer drugs that avoids stimulating the secretion of testosterone, a male hormone that causes the growth of most prostate cancers.

About 85 percent of newly-diagnosed prostate cancer tumors grow aided by testosterone. The goal of hormonal treatment, therefore, is to shut off the body's supply of testosterone. While hormonal therapies reduce testosterone to very low levels, current hormonal treatments - known as leutenizing hormone releasing hormone (LHRH) agonists - initially increase levels of testosterone before the level of the hormone drops. Abarelix-depot-M is the first in a new class of prostate cancer drugs known as (GnRH) antagonists which are designed to block the secretion of testosterone without this initial surge.

In the two studies presented today, abarelix-depot-M was compared to both the most-prescribed hormonal drug and combination of drugs. The currently used hormonal therapies result in testosterone surge in approximately 85 percent of patients. In contrast, zero percent of patients treated with abarelix-depot-M experienced a testosterone surge. In the first head-to-head, randomized, multi-center study of 255 prostate cancer patients who were candidates for initial hormonal therapy, 68 percent of patients treated with abarelix-depot-M achieved therapeutically lower levels of testosterone suppression after one week of therapy compared to zero patients treated with leuprolide plus bicalutamide, the current hormonal combination therapy which consists of an LHRH agonist plus an anti-androgen.

Similarly, in a second study of 271 prostate cancer patients, 72 percent of the abarelix- depot-M treated patients achieved therapeutically low levels of testosterone after one week of therapy versus no patients treated with leuprolide.

All three therapies studied achieved and maintained testosterone suppression from day 29 through day 85 in more than 90 percent of patients. Also, all three appeared to be well tolerated.

"We have known for a long time that male hormones such as testosterone feed the growth of prostate cancer cells," said Colonel David McLeod, M.D., professor in the department of surgery at Uniformed Services University and the principal investigator for one of the studies. "Unfortunately, the hormonal medications we currently use temporarily cause a rise in these hormones. The rise delays the efficacy of treatment for up to four weeks placing patients at risk for tumor growth. This rise, or 'flare', could also lead to painful symptom flare-ups in patients with advanced disease," said Dr. McLeod, who is also director of urologic oncology at Walter Reed Medical Center in Washington. "Physicians are concerned about the risk that cancer of the prostate could worsen during the surge in testosterone that accompanies currently available hormonal drugs. That is why the urology community is hoping to benefit from drugs such as abarelix-depot-M that may provide us with an important treatment advance in this area," Dr. McLeod added.

John Trachtenberg, M.D., director of the Prostate Center at Princess Margaret Hospital in Toronto and the principal investigator on the second study, said, "In our studies, abarelix-depot-M appeared to more quickly reduce the levels of testosterone without the hormonal surge associated with other hormonal therapies."

In addition, abarelix-depot-M more rapidly lowered the level of PSA (Prostate Specific Antigen) than leuprolide alone in one study and, in the second, provided an equivalent reduction in PSA level even when the anti-androgen bicalutamide was added to leuprolide. Additional data from these studies will be submitted for publication.

Prostate cancer is the most common cancer (excluding skin cancer) and the second leading cause of cancer death in men. More than 180,000 new cases of prostate cancer will be diagnosed in the United States this year and nearly 32,000 men will die of the disease. The prostate is a small, walnut-shaped gland at the base of the male bladder which secretes a major constituent of ejaculatory fluid.

Abarelix-depot-M is being studied in the treatment of prostate cancer, including advanced-stage hormonally-responsive prostate cancer, monotherapy in the neoadjuvant setting prior to definitive therapy to achieve prostate gland volume reduction, in patients with rising PSA and in patients receiving intermittent therapy. Another dosage regimen, abarelix-depot-F, is also being studied in endometriosis.

Amgen is a global biotechnology company that discovers, develops, manufactures and markets cost-effective human therapeutics based on advances in cellular and molecular biology.

PRAECIS PHARMACEUTICALS is a fully integrated drug discovery and development company which commercializes pharmaceuticals through integration of proprietary gene and chemistry-based combinatorial evolution technologies and drug delivery strategies.

This news release contains forward-looking statements that involve significant risks and uncertainties, including those discussed below and more fully described in the Securities and Exchange Commission reports filed by Amgen, including our most recent Form 10-Q. Amgen conducts research in the biotechnology/pharmaceutical field where movement from concept to product is uncertain; consequently, there can be no guarantee that any particular product candidate will be successful and become a commercial product.

Furthermore, our research, testing, pricing, marketing and other operations are subject to extensive regulation by domestic and foreign government regulatory authorities. In addition, sales of our products are affected by reimbursement policies imposed by third party payors, including governments, private insurance plans and managed care providers. These government regulations and reimbursement policies may affect the development, usage and pricing of our products.

In addition, while we routinely obtain patents for our products and technology, the protection offered by our patents and patent applications may be challenged, invalidated or circumvented by our competitors.

Amgen, Thousand Oaks
David Kaye, 805/447-6692 (media)
Cary Rosansky, 805/447-4634 (investors)

Renee Connolly
212/696-4455 ext 227 or 917/930-8471

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