First Albumin Fusion Protein Trial

ROCKVILLE, Md., March 23 /PRNewswire/ -- Human Genome Sciences, Inc. today announced that it has begun a Phase I human clinical trial of Albuferon(TM) in patients infected with Hepatitis C.

David C. Stump, M.D., Senior Vice President, Drug Development, said, "Hepatitis C is a significant public health problem in both developed and developing countries. A need exists for more effective and better tolerated treatments that will allow patients to avoid the long-term liver damage associated with this serious and insidious disease. We hope that Albuferon will become a useful therapy and meet an important need for these patients. We are excited to begin clinical trials with this novel product of a new class of drug."

Albuferon is created by fusing the gene for a human protein, interferon alpha, to the gene of another human protein, albumin. Based on preclinical studies, Albuferon should provide patients with a longer acting therapeutic activity and may offer an improved side-effect profile when compared to the current first line therapy, recombinant human interferon alpha.

The Phase I clinical trial is a multi-center, open-label study to determine the safety and pharmacology of single and double escalating doses of Albuferon in approximately 40 patients infected with Hepatitis C. Hepatitis C, a virus-caused liver inflammation, is transmitted by body fluids and affects 170 million people worldwide, or 3% of the world's population. Of these, about 95% of infected individuals reside in developing countries. In the U.S., Hepatitis C affects 3.9 million individuals, or approximately 1.8% of the U.S. population. An additional 37,000 new patients are diagnosed annually. Of these, 85% develop chronic infection and the remainder recover spontaneously from their disease within two to twelve weeks. The death toll from Hepatitis C in the U.S. is approximately 8,000 to 10,000 individuals per year.

William A. Haseltine, Ph.D., Chairman and Chief Executive Officer, said, "Initiation of a clinical trial of Albuferon is demonstration that the new technology acquired by the purchase of Principia last year is fruitful. The technology allows us to create and to manufacture new and hopefully substantially improved versions of approved biotherapeutic proteins. These compounds will be new products, not generic versions of existing drugs. We also plan to use this technology to improve the pharmaceutical characteristics of human proteins that we discover ourselves. The technology may also reduce the cost of manufacturing our own novel drugs as well."

Individuals interested in Albuferon are encouraged to contact Human Genome Sciences at 301-610-5790, extension 3550 or via the Internet at http://www.hgsi.com.

Human Genome Sciences is a company with the mission to treat and cure disease by bringing new gene-based drugs to patients.

HGS, Human Genome Sciences and Albuferon are registered trademarks of Human Genome Sciences, Inc. For additional information on Human Genome Sciences, Inc., visit the company's web site at http://www.hgsi.com . Copies of HGS press releases are also available by fax 24 hours a day at no charge by calling 800-758-5804, ext. 121115.

This announcement contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. The forward-looking statements are based on Human Genome Sciences' current intent, belief and expectations. These statements are not guarantees of future performance and are subject to certain risks and uncertainties that are difficult to predict. Actual results may differ materially from these forward-looking statements because of the company's unproven business model, dependence on new technologies, uncertainty as to clinical trial results, ability to develop and commercialize products, dependence on collaborators for services and revenue, substantial indebtedness, intense competition, uncertainty of patent and intellectual property protection, dependence on key management, uncertainty of regulation of products, dependence on key suppliers and other risks that may be described in the company's filings with the Securities and Exchange Commission. Existing and prospective investors are cautioned not to place undue reliance on these forward-looking statements, which speak only as of today's date. Human Genome Sciences undertakes no obligation to update or revise the information contained in this announcement whether as a result of new information, future events or circumstances or otherwise.

Human Genome Sciences Begins Phase I Clinical Trial of Albuferon In Hepatitis C Patients

Human Genome Sciences, Inc. today announced that it has begun a Phase I human clinical trial of Albuferon(TM) in patients infected with Hepatitis C.

March 23, 2001
Hepatitis C is a chronic liver disease caused by the hepatitis C virus (HCV). HCV is the most common chronic bloodborne disease in the United States and is four times as common as HIV, the virus that causes AIDS. HCV is a serious, often asymptomatic disease that leads to significant long-term damage and, potentially, carcinoma of the liver, in infected individuals. The disease is considered a major public health problem in both developed and developing countries and is the leading reason for liver transplant in the US.

HCV is an RNA virus that was initially identified in 1989. Although significant advancements have been made in understanding the virus and developing drugs against it, the virus continues to prove a challenging one for scientists to study. Unlike some other viruses, HCV is difficult to grow in cell culture and also changes its genetic makeup as it replicates, leading to a number of mutations as the virus has evolved. These mutations have now been classified into at least 6 major genotypes (classified as 1 to 6) and their closely related subtypes (classified as 1a, 1b, etc.). This genetic fluidity of the virus has posed a significant challenge to scientists attempting to develop a vaccine against the virus.

The mechanism by which HCV causes disease is poorly understood, however, it is believed that the body's cytotoxic T cells, which play a key role in the body's defenses against infection, kill the liver cells infected with HCV, thereby leading to liver damage.

Patient Population
HCV affects 170 million people worldwide (3% of the population worldwide), with 95% of infected individuals residing in developing countries. In the US, HCV affects 3.9 million individuals, representing approximately 1.8% of the US population. An additional 37,000 new patients are diagnosed annually; 85% of these individuals develop chronic infection, while the remainder recover spontaneously from their disease within 2 to 12 weeks. The death toll from hepatitis C in the US is approximately 8,000 to 10,000 individuals per year.

HCV genotypes 1, 2, and 3a are found worldwide, while the remaining genotypes are found in isolated geographic regions. In the US, genotype 1 accounts for 70% to 80% of HCV cases, genotype 2 accounts for approximately 15% of cases, and genotype 3 accounts for 5%. Most patients are infected with a single genotype of the virus. There is evidence that response to therapy varies with genotype. The mix of genotypes varies in the different infected populations around the world.

The incidence of HCV in the developed world is declining thanks to the availability of reliable diagnostic tests enabling routine screening of the blood supply. Despite the falling incidence of HCV, the disease is expected to be a major health care burden in the next few decades. Officials with the Centers for Disease Control and Prevention predict that the death toll from hepatitis C will triple in the next 20 years, eclipsing that of AIDS.

HCV is a disease of the adult population. Approximately 65% of cases in the US occur in individuals ages 30 to 49, with new cases found predominantly in adults aged 20 to 45.

Transmission
Hepatitis C is transmitted primarily through significant or repeated exposures to blood. In the U.S, injectable drug use and sexual contact with infected persons are the two exposures that presently account for the majority of HCV cases. In developing countries, HCV transmission occurs predominantly via administration of non-sterile injections.

Prior to the early 1990's, exposure from the blood supply was a significant source of HCV infection, as was injectable drug use. As of 1992, however, reliable diagnostic tests became available to undertake routine screening of the blood supply, such that the risk of exposure to HCV from the blood supply is now estimated to be quite low (at 1 in 100,000 transfusion recipients). At the present time, approximately 60% of new HCV cases with an identifiable risk factor are the result of injectable drug use and 15-20% occur due to sexual contact with infected persons.

Risk factors currently used to determine whether to screen a patient for HCV include:

• History of injecting illegal drugs
• Receipt of a blood transfusion or organ transplant prior to 1992
• Receipt of a blood product for hemophilia or other clotting factor condition before 1987
• Persistent normal alanine aminotransferase (ALT) levels
• Long-term kidney dialysis
• Exposure to blood or needlesticks in the workplace (e.g., health care, emergency or public safety workers), or
• Being born to an HCV-infected mother.

Screening for HCV is recommended in the presence of one or more risk factors.

Diagnosis
Typically, patients are evaluated for the presence of HCV if they have one or more risk factors listed above or if elevated alanine aminotransferase levels are found in a routine blood test. Alanine aminotransferase is an enzyme that is released by liver cells when they die; chronic abnormally high levels are indicative of liver damage.

When HCV is suspected, routine laboratory tests are followed with antibody tests to determine whether antibodies to the HCV virus are present in the blood and whether the RNA for the HCV virus itself is present. A liver biopsy is also performed to determine the extent to which the virus has damaged the liver. Genotyping of the virus is done to aid in planning therapy, since it is believed that different genotypes require different courses of treatment.

Symptoms
While HCV is a serious condition, it is a silent disease, with only 25% to 30% of patients reporting symptoms. When they occur, the symptoms of the disease tend to be vague, (e.g. fatigue, stomach pain, fever, loss of appetite, nausea, and joint pain) and common to a number of acute or chronic medical conditions, thus they are not particularly helpful in pointing physicians to a diagnosis of hepatitis. As the disease progresses, patients may develop jaundice, a yellow discoloration of the skin that indicates a decline in liver function.

Treatment
Chronically infected HCV patients are prescribed therapy if they have persistently elevated alanine aminotransferase levels indicative of liver damage, detectable RNA for the hepatitis C virus, and an abnormal liver biopsy.

The mainstay of treatment for HCV is interferon alfa therapy, typically given via injection under the skin in combination with capsules of ribavirin, an antiviral agent. A new pegylated, or long-acting version of interferon alfa was approved by the FDA in January 2001 in the U.S. This new therapy is likely to become incorporated into the standard of care for hepatitis C once it becomes available.

While combination therapy for the treatment of HCV has provided hope for the many patients afflicted with the disease, this complex regimen has a number of shortcomings.

First, the effectiveness of interferon therapy, even in combination with ribavirin, is far from optimal. In clinical studies, approximately 40% of previously untreated patients receiving this combination therapy had undetectable levels of the virus at 48 weeks in controlled studies, while approximately 46% of relapsed patients receiving this combination therapy had undetectable levels at 24 weeks. While interferon combination therapy provides an opportunity for cure in a significant number of patients, improvement in the effectiveness of HCV therapy clearly is needed.

Second, interferon therapy is associated with numerous side effects. Flu- like symptoms are common early in treatment and fatigue, hair loss, rash, and a severe form of anemia, which places a patient at increased risk of heart problems, can occur during treatment. Irritability, apathy, depression, and other mental changes also occur and prevent use of the therapy in some patients. Rarely, serious side effects such as autoimmune disease, depression with suicidal risk, seizures, acute kidney failure, eye diseases, scarring of lung tissue, hearing impairment, and serious infections, can occur. Over one- fourth of patients receiving interferon combination therapy in clinical trials required a change in their regimen due to side effects.

Lastly, interferon therapy is inconvenient, requiring a lengthy course of therapy (6 to 12 months) involving injections which patients must give to themselves under the skin 3 times weekly at home along with multiple ribavirin capsules taken twice daily.

While new agents are likely to offer some improvements in efficacy and convenience over the current regimens, further improvements in effectiveness, safety, and convenience of HCV therapy remain highly desirable.

Long-Term Consequences
While HCV may remain silent for many years, it has serious long-term consequences for afflicted individuals. Chronic liver disease, 40% of which is HCV-related, is currently the tenth leading cause of death in the US. Approximately 20% of patients afflicted with chronic hepatitis C develop cirrhosis, or scarring of the liver, typically after a period of approximately 20 to 30 years. Liver transplant is the only available treatment for patients who develop severe cirrhosis.

Other Resources

American Digestive Health Foundation (http://www.adhf.org)

American Liver Foundation (http://www.liverfoundation.org)

Centers for Disease Control and Prevention (http://www.cdc.gov/hepatitis)

NATAP (http://www.natap.org)

About Human Genome Sciences, Inc.
Human Genome Sciences is a company with the mission to treat and cure disease by bringing new gene-based drugs to patients.

HGS, Human Genome Sciences and Albuferon are registered trademarks of Human Genome Sciences, Inc. For additional information on Human Genome Sciences, Inc., visit the company's web site at http://www.hgsi.com . Copies of HGS press releases are also available by fax 24 hours a day at no charge by calling 800-758-5804, ext. 121115.

This announcement contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. The forward-looking statements are based on Human Genome Sciences' current intent, belief and expectations. These statements are not guarantees of future performance and are subject to certain risks and uncertainties that are difficult to predict. Actual results may differ materially from these forward-looking statements because of the company's unproven business model, dependence on new technologies, uncertainty as to clinical trial results, ability to develop and commercialize products, dependence on collaborators for services and revenue, substantial indebtedness, intense competition, uncertainty of patent and intellectual property protection, dependence on key management, uncertainty of regulation of products, dependence on key suppliers and other risks that may be described in the company's filings with the Securities and Exchange Commission. Existing and prospective investors are cautioned not to place undue reliance on these forward-looking statements, which speak only as of today's date. Human Genome Sciences undertakes no obligation to update or revise the information contained in this announcement whether as a result of new information, future events or circumstances or otherwise.

SOURCE Human Genome Sciences, Inc.
CO: Human Genome Sciences, Inc.
ST: Maryland