Results of pivotal study with Valtrex published in New England Journal of Medicine -- First Anti-Viral Proven to Reduce Transmission of a Sexually Transmitted Disease

TORONTO, Ontario (January 1, 2004) -- GlaxoSmithKline today announced the publication of results from a clinical trial evaluating VALTREX® (valacyclovir hydrochloride), an oral anti-viral, in the reduction of transmission of genital herpes, in the January 1, 2004 edition of the New England Journal of Medicine. VALTREX significantly reduced the risk of transmitting herpes infection to a heterosexual partner as compared to placebo when used along with safer sex practices.

"This is the first demonstration that an anti-viral medication can reduce the transmission of a sexually transmitted chronic viral infection. As genital herpes is widespread in nearly all parts of the world, these results offer an additional approach for both patients and health care providers for what is the major concern of most persons with genital herpes; reducing the risk of transmitting their infection to their sexual partner," says Dr. Larry Corey, lead study investigator and professor, Laboratory Medicine and Medicine, University of Washington and head of the Program in Infectious Diseases, Fred Hutchinson Cancer Research Center.

The transmission study with VALTREX, published in the latest edition of New England Journal of Medicine was a randomized, double-blind, placebo-controlled trial involving 1,484 healthy, heterosexual, monogamous couples in 21 countries. The primary endpoint of the study was to evaluate the reduction in risk of transmission of symptomatic genital herpes (signs or symptoms of genital herpes confirmed with a lab test) to an uninfected partner with use of suppressive therapy with VALTREX. The study showed that once-daily suppressive therapy with VALTREX 500 mg caplets, along with safer sex practices, reduced the risk of transmission of symptomatic genital herpes by 75 per cent versus placebo (0.5 per cent versus 2.2 per cent).

In addition, suppressive therapy with VALTREX reduced the risk of overall acquisition of the virus (with or without symptoms, confirmed by a lab test) by 48 per cent versus placebo (1.9 per cent versus 3.6 per cent). In addition, VALTREX significantly reduced the number of recurrences in the infected partner versus placebo, consistent with previous studies.

Throughout the eight-month study, all couples were counselled on safer sex practices at all study visits. The principles of safer sex practices were (1) to avoid sexual contact when the infected partner had any symptoms of genital herpes and (2) consistent and correct use of condoms during all sexual contacts.

The most commonly reported side effects in the study were headache (VALTREX 29 per cent, placebo 26 per cent), nasopharyngitis (VALTREX 16 per cent, placebo 15 per cent), and upper respiratory infection (VALTREX 9 per cent, placebo 10 per cent). The effect of VALTREX on transmission of genital herpes has not been established in immunocompromised individuals or same-sex couples.

About Genital Herpes

More than 86 million people worldwide are infected with the herpes simplex virus that causes genital herpes (HSV-2). Eight out of 10 people who are infected with the virus may not even be aware of their condition, and may only have experienced a mild initial outbreak without recognizing recurring symptoms of the disease. In Canada, 20 per cent of the population is infected with the virus. The virus never leaves the body, making it a lifelong infection that can recur at various times with or without symptoms.

Symptoms of genital herpes may include painful or itchy clusters of blisters, bumps or rashes in the genital area, or on the thighs or buttocks. Many people confuse GH symptoms with other conditions such as urinary tract infections, ingrown hair, jock itch, zipper burn, allergic reactions, vaginal infections, a cut or a scratch, or irritation from sexual intercourse or tight jeans.

Though the disease is most contagious during an outbreak, it can also be contagious between outbreaks when no signs and symptoms are present. In fact, in clinical studies, the majority of people got genital herpes from a partner who knew they had genital herpes but reported no signs or symptoms at the time of recent sexual activity. To help prevent spreading the disease to others, sexual contact should be avoided during outbreaks and latex condoms should be used at all times.

About Valtrex

VALTREX® (valacyclovir hydrochloride) caplets are indicated for the treatment or suppression of genital herpes in immunocompetent individuals and for the suppression of recurrent genital herpes in HIV infected individuals with CD4 cell counts >100cells/mm(3).

Adverse events reported with VALTREX include headache, nausea, abdominal pain, fatigue and rash. No data are available on the efficacy of suppressive therapy with VALTREX of more than one year's duration in healthy patients (six months in HIV-infected patients), or when started more than 72 hours after the onset of rash in herpes zoster or signs and symptoms for episodic therapy. Patients should tell their doctor if they have kidney problems because their dosage of VALTREX may need to be adjusted.

Health Canada has not yet approved VALTREX for reducing the risk of transmission of genital herpes.

About GlaxoSmithKline

GlaxoSmithKline Inc. -- one of the world's leading research-based pharmaceutical and health-care companies -- is committed to improving the quality of human life by enabling people to do more, feel better and live longer. In Canada, GlaxoSmithKline is a top 20 investor in Canadian research and development, contributing more than $100 million annually. The company is also among the top 10 corporate charitable donors and is recognized as one of the 50 best companies to work for in Canada.

For more information please contact:

Sandra Da Silva

Edelman

Tel.: 416-979-1120/416-580-0722

VALTREX® is a registered trademark, used under license by GlaxoSmithKline Inc.