ROCKVILLE, Maryland and LONDON, July 20 --

- BENLYSTA (belimumab) met its primary efficacy endpoint by achieving a
statistically significant improvement in patient response rate versus placebo in
BLISS-52 -

- First drug for lupus to reach this advanced stage of clinical development and
achieve positive results, in the largest randomized placebo-controlled clinical
trial ever completed in SLE patients -

Human Genome Sciences, Inc. (Nasdaq: HGSI) and GlaxoSmithKline PLC (GSK) today
announced that BENLYSTA(TM) (belimumab, formerly LymphoStat-B(R)) met the
primary endpoint in BLISS-52, the first of two pivotal Phase 3 trials in
patients with serologically active systemic lupus erythematosus (SLE). In the
placebo-controlled BLISS-52 study, the results showed that belimumab plus
standard of care achieved a clinically and statistically significant improvement
in patient response rate at Week 52, compared with standard of care alone. Study
results also showed that belimumab was generally well tolerated, with adverse
event rates comparable between belimumab and placebo treatment groups.


The BLISS-52 results demonstrated that BENLYSTA has the potential to become the
first new approved drug in decades for people living with systemic lupus, said
H. Thomas Watkins, President and Chief Executive Officer, HGS. Given the limited
treatment options currently available, patients would benefit greatly from
potential new treatments. BENLYSTA is an outstanding example of the type of
treatment HGS is working to develop and bring to patients. Assuming positive
results in November from our second Phase 3 trial of BENLYSTA, we and GSK plan
to submit marketing applications in the United States, Europe and other regions
in the first half of 2010.

Belimumab is an investigational drug and the first in a new class of drugs
called BLyS-specific inhibitors. No new drug for lupus has been approved by
regulatory authorities in more than 50 years. Belimumab is being developed by
HGS and GSK under a co-development and commercialization agreement entered into
in August 2006.

Lupus is a chronic, often debilitating, and sometimes fatal illness that
affects an estimated five million people worldwide and can have a devastating
effect on both patients living with the disease and their families, said Carlo
Russo, M.D., Senior Vice President, Biopharm Development, GSK. BENLYSTA is the
first medicine being developed specifically for lupus that has reached this late
stage of clinical development with positive results. We look forward to
completing the pivotal studies, with the hope of bringing this potentially
important therapeutic advance to patients suffering from SLE.

Key Findings from BLISS-52

The BLISS-52 results support and extend the findings that emerged in the
serologically active subgroup of SLE patients at Week 52 in our Phase 2 trial,
said David C. Stump, M.D., Executive Vice President, Research and Development,
HGS. We are delighted to report that the efficacy of treatment with BENLYSTA
plus standard of care was superior in this study to that of placebo plus
standard of care, while the safety profile was comparable overall to placebo.
BENLYSTA met the primary endpoint in this Phase 3 study at a robust level of
statistical significance. BENLYSTA also significantly reduced SLE disease
activity versus placebo based on a number of other measures, including SELENA
SLEDAI and Physician’s Global Assessment. Of note, a greater percentage of
patients receiving BENLYSTA achieved a clinically meaningful reduction in
steroid dose. We hope to have a full presentation of BLISS-52 results at an
appropriate scientific meeting later in 2009.

Topline BLISS-52 results include: -- Based on an intention-to-treat (ITT)
analysis, belimumab met its primary efficacy endpoint of superiority versus
placebo at Week 52. A clinically and statistically significant improvement was
shown in patient response rate for belimumab plus standard of care, vs. placebo
plus standard of care: 57.6% for 10 mg/kg belimumab, 51.7% for 1 mg/kg
belimumab, and 43.6% for placebo (p=0.0006 and p=0.011 for 10 mg/kg and 1 mg/kg
belimumab, respectively vs. placebo). Patient response was defined by an
improvement in SELENA SLEDAI score of 4 points or greater, no clinically
significant BILAG worsening, and no clinically significant worsening in
Physician’s Global Assessment. Results for each individual component of
the patient response rate were consistent with the overall improvement shown for
the primary endpoint. -- Results for prespecified major secondary efficacy
endpoints were: -- A significantly greater percentage of patients receiving
belimumab achieved a reduction in SELENA SLEDAI score of at least 4 points by
Week 52, with 58.3% for 10 mg/kg belimumab, 53.% for 1 mg/kg belimumab, and
46.0% for placebo (p=0.0024 and p=0.019 for 10 mg/kg and 1 mg/kg belimumab,
respectively vs. placebo). -- Improvement in Physician’s Global Assessment
(PGA) at Week 24 was greatest in the belimumab 10 mg/kg treatment group versus
placebo (p=0.0003 for 10 mg/kg and p=0.27 for 1 mg/kg belimumab, respectively)
with improvement observed within 4-8 weeks. -- A higher percentage of patients
in both belimumab treatment groups, versus placebo, had their average prednisone
dose reduced by at least 25% from baseline to 7.5 mg per day or less during the
last 12 weeks of study (p=0.053 for 10 mg/kg and p=0.025 for 1 mg/kg belimumab,
respectively vs. placebo). -- Improvement in health-related quality of life at
Week 24 as measured by the SF-36 Physical Component Summary (PCS) score was not
significantly different among treatment groups. However, although not a major
secondary endpoint, improvement in the SF-36 PCS score at Week 52 was
significantly greater in both belimumab treatment groups (p=0.025 for 10 mg/kg
and p=0.027 for 1 mg/kg belimumab, respectively vs. placebo). -- In BLISS-52,
belimumab was generally well tolerated, with rates of overall adverse events,
serious adverse events, infections and fatalities comparable between belimumab
and placebo treatment groups. Serious infections were reported in 5.9% of
patients on placebo and 6.1% of patients on belimumab. The most common adverse
events were headache, arthralgia, upper respiratory tract infections, urinary
tract infection and influenza, and were also comparable between belimumab and
placebo treatment groups. No malignancies were reported.

Professor Sandra V. Navarra, M.D., a principal investigator and Head of
Rheumatology at the University of Santo Tomas, Manila, The Philippines, said,
Given the limitations of available therapies, there is a great need for well
tolerated and effective treatments for lupus. We are very encouraged by the
findings of BLISS-52, and look forward to presenting these results later in the
year. We also look forward to the results of BLISS-76 later this year.

About the BENLYSTA (belimumab) Phase 3 Development Program

The Phase 3 development program for belimumab includes two double-blind,
placebo-controlled, multi-center Phase 3 superiority trials - BLISS-52 and
BLISS-76 - to evaluate the efficacy and safety of belimumab plus standard of
care, versus placebo plus standard of care, in serologically active (i.e.,
autoantibody-positive) patients with SLE. This is the largest clinical trial
program ever conducted in lupus patients. BLISS-52 randomized and treated 865
patients at 90 clinical sites in 13 countries, primarily in Asia, South America
and Eastern Europe. BLISS-76 enrolled and randomized 826 patients at 133
clinical sites in 19 countries, primarily in North America and Europe. The
design of the two trials is similar, but the duration of therapy in the two
studies is different - 52 weeks for BLISS-52 and 76 weeks for BLISS-76. The data
from BLISS-76 will be analyzed after 52 weeks in support of a potential
Biologics License Application in the United States and Marketing Authorization
Application in Europe and other regions. HGS designed the Phase 3 program for
belimumab in collaboration with GSK and leading international SLE experts, and
the program is being conducted under a Special Protocol Assessment agreement
with FDA.

The primary efficacy endpoint of BLISS-52 and BLISS-76 is the patient response
rate at Week 52, as defined by: (1) a reduction from baseline of at least 4
points on the SELENA SLEDAI disease activity scale (which indicates a clinically
important reduction in SLE disease activity); (2) no worsening of disease as
measured by the Physician’s Global Assessment (worsening defined as an
increase of 0.30 points or more from baseline); and (3) no new BILAG A organ
domain score (which indicates a severe flare of lupus disease activity) and no
more than one new BILAG B organ domain score (which would indicate a moderate
flare of disease activity). Analysis for the primary endpoint is based on
intention-to-treat (ITT) and adjusted for baseline stratification factors,
including SELENA SLEDAI score, proteinuria and race.

In each of the two Phase 3 trials, patients were randomized to one of three
treatment groups: 10 mg/kg belimumab (BLISS-52, n=290), 1 mg/kg belimumab
(BLISS-52, n=288), or placebo (BLISS-52, n=287). Patients are dosed
intravenously on Days 0, 14 and 28, then every 28 days thereafter for the
duration of the study. All receive standard of care therapy in addition to the
study medication. Safety is reviewed by an independent Data Monitoring Committee
throughout both studies.

About BENLYSTA (belimumab)

Belimumab is an investigational human monoclonal antibody drug that
specifically recognizes and inhibits the biological activity of B-lymphocyte
stimulator, or BLyS(R). BLyS is a naturally occurring protein discovered by HGS
that is required for the development of B-lymphocyte cells into mature plasma B
cells. Plasma B cells produce antibodies, the body’s first line of defense
against infection. In lupus and certain other autoimmune diseases, elevated
levels of BLyS are believed to contribute to the production of autoantibodies -
antibodies that attack and destroy the body’s own healthy tissues. The
presence of autoantibodies appears to correlate with disease severity.
Preclinical and clinical studies suggest that belimumab can reduce autoantibody
levels in SLE. BLISS 52 results suggest that belimumab can reduce SLE disease
activity, and a second Phase 3 trial, BLISS-76, is underway to confirm these

About the Collaboration with GSK

In August 2006, HGS and GSK entered into a definitive co-development and
co-commercialization agreement under which HGS has responsibility for conducting
the belimumab Phase 3 trials, with assistance from GSK. The companies will share
equally in Phase 3/4 development costs, sales and marketing expenses, and
profits of any product commercialized under the current agreement.

About Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic, life-threatening autoimmune
disease. Approximately five million people worldwide, including approximately
1.5 million in the United States, suffer from various forms of lupus, including
SLE. Lupus can occur at any age, but appears mostly in young people ages 15 to
45. About 90 percent of those diagnosed with lupus are women. African-American
women are about three times more likely to develop lupus, and it is also more
common in Hispanic, Asian and American Indian women. Symptoms may include
extreme fatigue, painful and swollen joints, unexplained fever, skin rash and
kidney problems. Lupus can lead to arthritis, kidney failure, heart and lung
inflammation, central nervous system abnormalities, inflammation of the blood
vessels and blood disorders. For more information on lupus, visit the Lupus
Foundation of America at, the Lupus Research Institute at, the National Institute of Arthritis and
Musculoskeletal and Skin Diseases at, or Lupus Europe at

Conference Call

HGS management will hold a conference call to discuss this announcement today
at 8:15 AM Eastern. Investors may listen to the call by dialing 1-888-632-5010
or +1-913-312-0402, passcode 8364417, five to 10 minutes before the start of the
call. A replay of the conference call will be available within a few hours after
the call ends. Investors may listen to the replay by dialing 1-888-203-1112 or
+1-719-457-0820, confirmation code 8364417. Today’s conference call also
will be webcast and can be accessed at Investors interested in
listening to the live webcast should log on before the conference call begins to
download any software required. Both the audio replay and the archive of the
conference call webcast will remain available for several days.

About GlaxoSmithKline

GlaxoSmithKline is one of the world’s leading research-based
pharmaceutical and healthcare companies, and is committed to improving the
quality of human life by enabling people to do more, feel better and live
longer. For more information, visit GlaxoSmithKline on the World Wide Web at

About Human Genome Sciences

The mission of HGS is to apply great science and great medicine to bring
innovative drugs to patients with unmet medical needs. The HGS clinical
development pipeline includes novel drugs to treat hepatitis C, lupus,
inhalation anthrax and cancer.

The Company’s primary focus is rapid progress toward the
commercialization of its two lead drugs, Albuferon(R) (albinterferon alfa-2b)
for hepatitis C and BENLYSTA(TM) (belimumab, formerly LymphoStat-B(R)) for
lupus. Albuferon has now completed Phase 3 development, and the submission of
global marketing applications is expected in fall 2009. BENLYSTA successfully
met its primary endpoint in the first of two Phase 3 trials in systemic lupus
erythematosus; results of the second BENLYSTA Phase 3 trial are expected in
November 2009. Also in late-stage development is raxibacumab (ABthrax(TM)) for
the treatment of inhalation anthrax (Biologics License Application currently
pending with the U.S. Food and Drug Administration). In addition, HGS has
substantial financial rights to certain products in the GSK clinical pipeline
including darapladib, currently in Phase 3 development in patients with coronary
heart disease, and Syncria(R) (albiglutide), currently in Phase 3 development in
patients with type 2 diabetes.

For more information about HGS, please visit the Company’s web site at Health professionals and patients interested in clinical trials of
HGS products may inquire via e-mail to This e-mail
address is being protected from spam bots, you need JavaScript enabled to view
it or by calling HGS at +1-301-610-5790, extension 3550. HGS, Human Genome
Sciences, ABthrax, Albuferon, BENLYSTA, BLyS and LymphoStat-B are trademarks of
Human Genome Sciences, Inc.

HGS Safe Harbor Statement

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, its dependence on new technologies, the
uncertainty and timing of clinical trials, the Company’s ability to
develop and commercialize products, its dependence on collaborators for services
and revenue, its substantial indebtedness and lease obligations, its changing
requirements and costs associated with facilities, intense competition, the
uncertainty of patent and intellectual property protection, the Company’s
dependence on key management and key suppliers, the uncertainty of regulation of
products, the impact of future alliances or transactions and other risks
described in the Company’s filings with the Securities and Exchange
Commission. In addition, while the Company has completed delivery of ABthrax to
the U.S. Strategic National Stockpile, the Company will continue to face risks
related to FDA’s approval of the Company’s Biologics License
Application for ABthrax. If the Company is unable to meet requirements
associated with the ABthrax contract, future revenues from the sale of ABthrax
to the U.S. Government will not occur. 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

GlaxoSmithKline Forward-Looking Statements

Under the safe harbor provisions of the US Private Securities Litigation Reform
Act of 1995, GSK cautions investors that any forward-looking statements or
projections made by GSK, including those made in this announcement, are subject
to risks and uncertainties that may cause actual results to differ materially
from those projected. Factors that may affect GSK’s operations are
described under ’Risk Factors’ in the ’Business Review’
in GSK’s Annual Report on Form 20-F for 2008.

SOURCE: Human Genome Sciences, Inc.

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