Human Genome Sciences and GlaxoSmithKline Announce Positive Results in Second of Two Phase 3 Trials of BENLYSTA in Systemic Lupus Erythematosus

- BENLYSTA (belimumab) 10 mg/kg plus standard of care met its primary efficacy
endpoint by achieving a statistically significant improvement in patient
response rate versus placebo plus standard of care at Week 52 in BLISS-76 -

- Primary efficacy endpoint met in two pivotal Phase 3 trials, as specified by
Special Protocol Assessment agreement with FDA -
ROCKVILLE, Md. & LONDON--(Business Wire)--
Human Genome Sciences, Inc. (Nasdaq:HGSI) and GlaxoSmithKline PLC (GSK) today
announced that BENLYSTA (belimumab) met the primary endpoint in BLISS-76, the
second of two pivotal Phase 3 trials in seropositive patients with systemic
lupus erythematosus (SLE). BLISS-76 study results through 52 weeks showed that
belimumab 10 mg/kg plus standard of care achieved a statistically significant
improvement in patient response rate as measured by the SLE Responder Index at
Week 52, compared with placebo plus standard of care. Study results also showed
that belimumab was generally well tolerated, as demonstrated by a similar rate
of discontinuations due to adverse events across treatment groups, with overall
adverse event rates comparable between belimumab and placebo treatment groups.

"The BLISS-76 results confirm our view 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. "We take
great pride in the innovation and scientific rigor that has made it possible to
bring BENLYSTA to this point. We plan to submit marketing applications in the
first half of 2010, following discussions with regulatory authorities in the
United States, Europe and other regions. We will continue to work with GSK to
advance this drug to the market where it may benefit patients with significant
need."

Carlo Russo, M.D., Senior Vice President, Biopharm Development, GSK, said, "The
results from this second pivotal Phase 3 trial reinforce our belief that
belimumab could deliver a significant therapeutic option for patients with lupus
who have had no new treatment in fifty years. We look forward to continuing our
collaboration with HGS in order to bring this important medicine to patients."

The data from the BLISS-76 study were analyzed after 52 weeks, in accord with
the study protocol, in support of a potential Biologics License Application in
the United States and Marketing Authorization Applications in Europe and other
regions. However, the BLISS-76 study is ongoing and will continue for 24 more
weeks. Additional data will be available following completion of the full
76-week study period. Belimumab is an investigational drug and the first in a
new class of drugs called BLyS-specific inhibitors. Belimumab is being developed
by HGS and GSK under a co-development and commercialization agreement entered
into in August 2006.

Key Findings from BLISS-76

"We are delighted that the efficacy of treatment with belimumab plus standard of
care was superior to placebo plus standard of care in both BLISS-52 and
BLISS-76, with overall adverse event rates comparable to placebo plus standard
of care," said David C. Stump, M.D., Executive Vice President, Research and
Development, HGS. "Belimumab met the primary endpoint in both pivotal Phase 3
trials, as specified by the Special Protocol Assessment Agreement with FDA. We
look forward to the full presentation of the BLISS-76 52-week results at an
appropriate scientific meeting, hopefully in the first half of 2010."

Topline BLISS-76 results include:

* Based on an intention-to-treat (ITT) analysis, belimumab 10 mg/kg met its
primary efficacy endpoint of superiority versus placebo at Week 52. A
statistically significant improvement was shown in patient response rate for
belimumab 10 mg/kg plus standard of care, vs. placebo plus standard of care, as
measured by the SLE Responder Index at Week 52: 43.2% for 10 mg/kg belimumab,
40.6% for 1 mg/kg belimumab, and 33.8% for placebo (p=0.021 and p=0.10 for 10
mg/kg and 1 mg/kg belimumab, respectively vs. placebo). The 1 mg/kg dose plus
standard of care did not achieve statistically significant improvement in the
current study. The SLE Responder Index defines patient response as an
improvement in SELENA SLEDAI score of 4 points or greater, with no clinically
significant BILAG worsening and no clinically significant worsening in
Physician`s Global Assessment.
* Results for prespecified major secondary efficacy endpoints were:

* The proportion of patients with a reduction in SELENA SLEDAI score of at least
4 points by Week 52, was 46.9% for belimumab 10 mg/kg, 42.8% for belimumab 1
mg/kg, and 35.6% for placebo (p=0.0062 and p=0.087 for belimumab 10 mg/kg and 1
mg/kg, respectively vs. placebo).
* Improvement from baseline in Physician`s Global Assessment (PGA) at Week 24
was not statistically different between the belimumab and placebo treatment
groups. Mean improvement in PGA at Week 52, a prespecified although not a major
secondary endpoint, was 0.49 for belimumab 10 mg/kg, 0.55 for belimumab 1 mg/kg,
and 0.46 for placebo (p=0.12 for belimumab 10 mg/kg and p=0.022 for 1 mg/kg,
respectively vs. placebo).
* At entry into the BLISS-76 study, approximately 46% of patients were receiving
steroids at a prednisone-equivalent dose of at least 7.5 mg per day. Among these
patients, the percentage of patients who had their average steroid dose reduced
by at least 25% from baseline to 7.5 mg per day or less during the last 12 weeks
of study was 16.7% for belimumab 10 mg/kg, 19.2% for belimumab 1 mg/kg, and
12.7% for placebo (not statistically significant 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. Mean improvement in the SF-36 PCS score at Week 52, a
prespecified although not a major secondary endpoint, was 3.41 for belimumab 10
mg/kg, 4.37 for belimumab 1 mg/kg, and 2.85 for placebo (p=0.51 for belimumab 10
mg/kg and p=0.012 for 1 mg/kg, respectively vs. placebo).

* In BLISS-76, belimumab was generally well tolerated, with rates of overall
adverse events, serious and/or severe adverse events, all infections, serious
and/or severe infections, and discontinuations due to adverse events comparable
between treatment groups receiving belimumab plus standard of care and the
treatment group receiving placebo plus standard of care. Serious and/or severe
adverse events were reported in 26.8% of patients on belimumab and 24.0% of
patients on placebo. Infections were reported in 72.1% of patients on belimumab
and 67.3% of patients on placebo. Serious and/or severe infections were reported
in 7.2% of patients on belimumab and 8.0% of patients on placebo. Serious and/or
severe infusion reactions were reported in 1.1% of patients on belimumab and
0.7% of patients on placebo. Discontinuations due to adverse events were 7.2% in
the belimumab treatment groups and 7.6% in the placebo treatment group.
Malignancies were reported by 2, 3, and 1 subjects in the belimumab 10 mg/kg,
belimumab 1 mg/kg and placebo groups, respectively. There were three deaths in
the study, with 1, 2, and 0 reported in the belimumab 10 mg/kg, belimumab 1
mg/kg and placebo groups, respectively.

"The lupus community has waited for decades for one positive Phase 3 trial of an
investigative drug developed for lupus. Now we have two. Based on the data we
now have in hand, we have cause for hope that belimumab may emerge as a
significant new treatment for lupus," said Joan T. Merrill, M.D., a study
investigator, Program Chair, Clinical Pharmacology Research Program, Oklahoma
Medical Research Foundation, Oklahoma City, and Professor, Department of
Medicine, University of Oklahoma Health Sciences Center.

About the 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 seropositive (HEp-2 ANA ≥ 1:80
and/or anti-dsDNA ≥ 30 IU/mL) 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 randomized and treated 819 patients at 136
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. Data
from BLISS-76 were analyzed after 52 weeks in support of a potential Biologics
License Application in the United States and Marketing Authorization
Applications 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 measured by the SLE Responder Index, which is 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); (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 indicates a moderate flare of disease activity). Analysis for the primary
endpoint is based on intention-to-treat 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; BLISS-76, n=273), 1 mg/kg
belimumab (BLISS-52, n=288; BLISS-76, n=271), or placebo (BLISS-52, n=287;
BLISS-76, n=275). Patients are dosed intravenously on Days 0, 14 and 28, then
every 28 days thereafter for the duration of the study. All patients receive
standard of care therapy in addition to the study medication. Safety is reviewed
by an independent Data Monitoring Committee throughout both studies.

About Belimumab

Belimumab is an investigational human monoclonal antibody drug that specifically
recognizes and inhibits the biological activity of B-lymphocyte stimulator, or
BLyS. 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.
The results of two pivotal Phase 3 trials, BLISS-52 and BLISS-76, suggest that
belimumab can reduce SLE disease activity.

About the HGS/GSK Collaboration

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. No new drug for lupus has been approved by
regulatory authorities in more than 50 years. For more information on lupus,
visit the Lupus Foundation of America at www.lupus.org, the Lupus Research
Institute at www.lupusresearchinstitute.org, the National Institute of Arthritis
and Musculoskeletal and Skin Diseases at www.niams.nih.gov, or Lupus Europe at
www.elef.rheumanet.org.

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 800-753-9057 or
913-312-0718, passcode 9331404, 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 888-203-1112 or
719-457-0820, confirmation code 9331404. Today`s conference call also will be
webcast and can be accessed at www.hgsi.com. 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`s collaboration with HGS is led by its GSK Biopharm R&D
division, which employs novel approaches to harness the therapeutic potential of
biopharmaceuticals for the benefit of patients with serious autoimmune disease.
This innovative research is one way GSK - one of the world`s leading
research-based pharmaceutical and healthcare companies - can deliver on its
commitment to improve 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 www.gsk.com.

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 lupus, hepatitis C,
inhalation anthrax and cancer.

The Company`s primary focus is rapid progress toward the commercialization of
its two lead drugs, BENLYSTA (belimumab) for lupus and ZALBIN (albinterferon
alfa-2b) for hepatitis C. BENLYSTA has successfully met its primary endpoint in
two pivotal Phase 3 trials in systemic lupus erythematosus, and the submission
of marketing applications in the U.S., Europe and other regions is planned in
the first half of 2010. ZALBIN has completed Phase 3 development, and the
submission of global marketing applications is planned in fourth quarter 2009.
In May 2009, HGS submitted a Biologics License Application to the FDA for
raxibacumab for the treatment of inhalation anthrax. 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 (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
www.hgsi.com. Health professionals and patients interested in clinical trials of
HGS products may inquire via e-mail to medinfo@hgsi.com or by calling HGS at
(877) 822-8472.

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 Human Genome
Sciences` unproven business model, its dependence on new technologies, the
uncertainty and timing of clinical trials, Human Genome Sciences` 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, Human Genome
Sciences` 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 SEC. 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.

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.

HGS CONTACTS:
Media
Jerry Parrott
Vice President, 301-315-2777
Corporate Communications
or
Investors
Peter Vozzo, 301-251-6003
Senior Director, Investor Relations
or
GSK CONTACTS:
U.K. Media Inquiries --
Philip Thomson, (020) 8047-5502
Gwenan White, (020) 8047-5502
Claire Brough, (020) 8047-5502
Stephen Rea, (020) 8047-5502
or
U.S. Media Inquiries --
Holly Russell, 919-483-2839
Mary Anne Rhyne, 919-483-2839
or
European Analyst/Investor Inquiries -
David Mawdsley, (020) 8047-5564
Sally Ferguson, (020) 8047-5543
Gary Davies, (020) 8047-5503
or
U.S. Analyst/Investor Inquiries -
Tom Curry, 215-751-5419
Jen Hill Baxter, 215-751-7002

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