GENELAB-synopsis/primer below
Genelabs' Small Molecule,
Gene-Regulating Drug Program
Utilizing its proprietary MERLIN
technology, Genelabs has targeted
small molecule organics to 10-12
base pair sequences in DNA, such
that transcription factors, or other
targeted DNA regulatory proteins,
are selectively displaced from genes
in a predictable manner, and that
expression levels of target genes are
modulated. This important new class
of potential gene-regulating drugs
has applicability across virtually all
fields of medicine.
Genomics Program
Genelabs Technologies, Inc. is using
positional cloning technologies, including
direct cDNA selection, to isolate novel
human genes encoding
immunomodulatory molecules from a
cluster of such genes on human
chromosome 5 that is presumably
involved in asthma, myeloid leukemias,
and other disorders.
Unlike more traditional strategies,
Genelabs' positional cloning approach is
focused on the developing
physical/genetic map of the human
genome as means to predict where genes
of potential therapeutic value may reside.
It also enables rapid isolation and
characterization of genes expressed in
very small amounts such as cytokines or
other immunoregulators.
Currently, over 300 cDNAs from as
many as 50 putative novel genes from the
chromosome 5 cytokine gene cluster
region have been sequenced and are in
various stages of characterization.
Genelabs' studies are targeted on
development of new generation
therapeutics for treatment of immune
disorders, including asthma, and cancer.
Program Objective
The long arm of chromosome 5 is the site
of a dense cluster of immunomodulatory
genes encoding cytokines, their receptors,
transcriptional regulatory factors, and of
genes involved in DNA repair and V(D)J
recombination. Several disease genes
have also been genetically mapped to this
region, including 5q-syndrome, an
autosomal form of hereditary deafness,
Treacher-Collins syndrome, diastrophic
dysplasia, atopic allergy and bronchial
hyperresponsiveness. Cytokines, as well
as chemokines, are proinflammatory
mediators found and implicated in a
growing number of normal
immunoregulatory functions and diseases,
such as rheumatoid arthritis, atopic
allergy, asthma, cystic fibrosis,
atherosclerosis and ulcerative colitis. It is
likely that the critical gene for
asthma-susceptibility has not been found
yet, as no direct association with asthma
has been found for known region-specific
immunomodulators, such as IL4, IL5,
IL3, GM-CSF, IL9, IL13, FGFA
and beta-ADR. Isolating novel
immunomodulatory genes from this
cluster is a major technical challenge with
potentially immense commercial rewards.
To date, only a small fraction of the genes
estimated to reside within this region have
been identified. Genelabs' Cytokine
Discovery group has made significant
progress in identifying a number of the
genes in this cluster, and is uniquely
positioned to rapidly identify the
remaining as yet uncharacterized genes in
this region.
Advantage of Genelabs' Approach
Several academic cDNA and DNA
sequencing projects are in progress: the
British project, the Japanese project and
the US project being the largest three.
Certain commercial ventures have also
been randomly sequencing pieces of
cDNA and filing patents on the sequences,
in the hope that the sequences may
represent genes of interest. This approach
is however, dependent on screening
conventional cDNA libraries and
inevitably results in the preferential
identification of more abundant cDNAs.
It is thus heavily biased against the very
genes that the Genelabs approach seeks
to selectively target; genes that produce
low abundance mRNAs or mRNAs
which are only rarely expressed. One
final problem inherent in the random
picking approach occurs in those cases
where the cDNA libraries have not been
properly validated; this results in the
derivation of DNA sequences from
thousands of "junk" clones within such
libraries. In contrast to this approach
which is trammeled by the complexity and
integrity of a few cDNA libraries, the
cDNA resources that we have built are
designed to enhance the quality and
complexity of the molecules that are
sampled. Therefore, Genelabs' positional
cloning approach has substantial
advantages over other cloning strategies in
the isolation of immunomodulatory genes:
it facilitates the isolation of genes
expressed at very low levels.
Current Project Status
In studies that have already been
published, Genelabs scientists had
isolated a cDNA from a complex mixture
of T-cell specific cDNAs that was
subsequently found by functional studies
to encode a new cytokine, IL13. Recent
analysis of about 3,000 cDNAs selected
with the genomic region spanning 1.2 Mb
of 5q31 that included IL13, IL4, IL5,
IRF1, IL3, GM-CSF, revealed 150
novel cDNA clones with median size of
~500 bp, and 10 known human cDNAs
that had not been mapped to this genomic
area before. Physical mapping of cDNAs
to the starting YACs and chromosome
5-specific cosmids enabled us to group
cDNAs into ~ 50 "bins" according to their
location and partial overlap with each
other. Due to extensive homologies
detected by sequence analysis, 10 new
genes have been identified within this
region, and their near full length
sequences isolated. They include human
homologs of known genes:
Amiloride-sensitive sodium
channel (a putative receptor)
LC Acyl-CoA synthetase
RAD50 (a putative tumor
suppressor)
Septin 2 (a putative cell cycle
control gene)
Prolyl 4-hydroxylase, alpha
subunit (a putative chaperone)
Ubiquinol cytochrome C
reductase
GTP-binding regulatory
protein (a signal transduction
pathway gene)
KIF3A-like protein
FRAXE-like gene
GDF-9
In our publication on a novel human gene
RAD50 (Dolganov et al., 1996) we have
suggested that this might be a tumor
suppressor. Our data is supported by those
of R. Satodate et al. (1996) claiming that
this particular genomic region is deleted
in stomach adenocarcinomas. Many
cDNAs revealed interesting tissue
expression profiles, suggesting that they
might be novel immunomodulators. These
gene candidates are in varying stages of
evaluation. It is important to note that, to
date, half of the genes isolated during the
selection process are immunomodulatory
in nature, and there is a strong likelihood
that several of these novel genes encode
proteins of therapeutic interest.
Summary
Using internally-developed positional
cloning technologies and novel reagents,
the Cytokine Discovery group at Genelabs
has identified a number of novel genes
from the cytokine gene cluster on human
chromosome 5, a region known to contain
a number of immunomodulatory genes,
and thought to be associated with
susceptibility to atopy and asthma. The
ability of direct selection techniques to
selectively isolate genes from very large
genomic regions has therefore been
definitively demonstrated by the study
summarized here, as well as by numerous
other successful examples from Genelabs
scientists and collaborators. Genelabs
proposes to further characterize these gene
candidates and the other 50 "bins" in order
to identify novel genes with demonstrated
disease association and potential
therapeutic interest.
Isolating other immunomodulatory genes
from this cluster is a major technical
challenge but has immense commercial
rewards. Cytokines have become
important therapeutics in the treatment of
infection, cancer and hematologic
disorders and are being developed for the
treatment of inflammation and
autoimmune diseases. With only a small
number of cytokines commercially
available, the worldwide market in 1996
nevertheless exceeded $5 billion.
Asthma Program
Asthma is an inflammatory disease with
intermittent respiratory symptoms,
bronchial hyperresponsiveness and
reversible airflow obstructions. Asthma
affects five to ten percent of the
population in the United States, and it
contains a genetic component that plays a
major role in its pathogenesis. Recent
studies have confirmed the complexity of
asthma genetics that is most likely
associated with several major asthma
susceptibility genes. An understanding of
the genetic variation that predisposes
people to asthma could open a variety of
potential diagnostic and therapeutic
avenues.
Genetic mapping studies suggest that as
yet unidentified genes associated with
asthma reside in the region of
chromosome 5 that Genelabs is studying.
Genelabs scientists used positional
cloning to isolate many new genes for the
purpose of identifying the gene or genes
potentially associated with asthma from
this region and have discovered more than
50 novel chromosome-5 specific genes,
one or more of which may be implicated
in the pathophysiology of asthma.
Physical mapping studies have shown that
this region within the long arm of human
chromosome 5 encodes an unusually large
number of immunomodulatory proteins
including growth factors, growth factor
receptors, transcription regulatory factors
and hormone/neurotransmitter receptors.
For this reason, it may be anticipated that
genes encoding proteins involved in
diseases other than asthma may also prove
to be among the novel genes isolated by
Genelabs. Patent applications have been
filed in the United States to claim these
novel gene sequences and the company is
now collaborating with John Fahy, M.D.
and his colleagues at the University of
California San Francisco (UCSF) to
evaluate whether the expression of these
genes is altered in atopic asthmatic
patients compared to healthy subjects,
which will help implicate the specific
putative asthma gene candidates.
DRUG DISCOVERY AT GENELABS
Genelabs' enabling technology, MERLIN,
offers access to a new field of
pharmaceuticals: small molecule organic
DNA-binding drugs targeted to specific
disease associated genes. MERLIN facilitates
the discovery of novel DNA-binding
chemistries from complex mixtures and the
characterization of these molecules that
allows optimizing and targeting them to
specific gene sequences. The resulting drugs
are expected to be capable of up-regulating or
down-regulating, as appropriate, the
expression levels of target genes.
Genelabs? Diagnostics Pte Ltd (also referred to as GLD) is a wholly-owned
subsidiary of Genelabs Technologies, Inc., a biopharmaceutical company
focused on the discovery and development of gene-regulating drugs.
GLD manufactures and sells diagnostic products. The core business consists of
Western Blot assays, rapid tests for the point-of-care market, and ELISAs
(Enzyme-Linked Immunosorbent Assays) for the screening market. These
products are mainly used for the diagnosis of infectious diseases and
immunological disorders.
Western Blot assays are qualitative tests used for the detection of antibodies to
viruses or bacteria (e.g. HIV, Helicobacter pylori) in human serum or plasma.
They are often used as a more specific supplemental test on human serum or
plasma specimens found reactive using first line screening tests such as ELISAs.
Genelabs announced positive results of a pivotal
trial of its first drug candidate and its intent to
submit a New Drug Application to the FDA. If
approved, GL701 will be the first new drug
indicated for the treatment of lupus in the past 40
years (see Company Press Release).
GL701 for Systemic Lupus
Erythematosus
GL701, Genelabs' drug candidate for systemic
lupus erythematosus (SLE), is a pharmaceutical
preparation that contains prasterone, the
pharmaceutical generic designation for
dehydroepiandrosterone (DHEA), as the active
ingredient. GL701 is manufactured under US
Food and Drug Administration (FDA) regulations
that govern the purity, content and identity of
drugs (current Good Manufacturing Practices,
cGMPs). DHEA is a naturally occurring hormone
that is produced by the adrenal glands. SLE
patients generally have abnormally low levels of
DHEA and studies have shown that hormonal
influences play a role in the development and
progression of SLE.
Studies by Genelabs' scientific collaborators at
Stanford University have indicated that oral
administration of DHEA may be effective and
safe for the treatment of SLE. A Phase II clinical
study conducted at Stanford University in 1993
involved 28 women with SLE who received
either DHEA or placebo over the three-month
study period. Results of this study, published in
Arthritis and Rheumatism in December 1995,
demonstrated a benefit in the DHEA-treated
group compared to the placebo-treated group in
all of the efficacy variables. These variables
include the patients' own assessment of their
condition (Patient Global Assessment), the
physicians' clinical assessment of disease
(Physician Global Assessment) and a commonly
accepted disease activity index (Systemic Lupus
Erythematosus Disease Activity Index -
SLEDAI). In addition, mean prednisone dose was
decreased in the group of patients treated with
DHEA while it increased in the group of patients
treated with placebo. Prednisone, a corticosteroid
drug that is commonly used to treat SLE, has
many serious side effects that can lead to
disability and death in SLE patients.
Genelabs filed an Investigational New Drug
application (IND) with the FDA in December
1993. In May 1994, the company started its first
Phase III clinical trial, a randomized,
double-blind, placebo-controlled, multi-center
study for the treatment of mild to moderate SLE
in women who require prednisone or other
steroids for their treatment. The study was
designed to learn whether GL701 would allow
steroid-dependent SLE patients to reduce their
prednisone dose to 7.5 mg per day (a dose
equivalent to physiologic levels) or less while
either improving or maintaining stability of their
disease activity. The company initiated a second
Phase III clinical trial of GL701 in women with
mild to moderate lupus in March 1996. The study
was designed to determine whether GL701 can
improve or stabilize clinical outcome and disease
symptoms in women with SLE.
First Phase III Clinical Trial
In the first Phase III study, SLE patients treated
with GL701 had a greater response to treatment
than those on placebo, demonstrated by sustained
reduction of their prednisone dose to physiologic
levels. This beneficial effect was most evident in
patients with active disease (SLEDAI >2) at
baseline.
The study enrolled 191 women with mild to
moderate SLE, who were receiving daily doses of
10 to 30 mg of prednisone, at 18 sites in the
United States. Patients were randomized to
received either placebo or 100 mg or 200 mg of
GL701 daily for seven to nine months. At
enrollment, baseline SLE Disease Activity Index
(SLEDAI) scores were recorded for all patients.
During the study, steroid doses were required to
be reduced at each visit according to the study
protocol, provided a patient's SLEDAI score had
not increased.
The study results, presented in November 1997 at
the American College of Rheumatology National
Scientific Meeting showed that, compared to the
placebo group, a greater percentage of patients in
the GL701 200 mg group achieved the primary
endpoint of a sustained reduction of their steroid
dose to 7.5 mg per day or less (i.e., physiologic
levels equivalent to those normally produced by
their own adrenal glands). This beneficial effect
was most evident in the group of 137 SLE
patients with active disease at baseline, defined
as a SLEDAI score greater than 2. Among these
patients, response rates were 51% for the group
who received daily doses of 200 mg of GL701,
38% for the group who received 100 mg of
GL701 and 29% for the group who received
placebo. Results also indicated that GL701 was
well tolerated in these women with SLE. These
safety results may not apply to the general
population because people with SLE are believed
to have abnormally low DHEA levels.
Second Phase III Clinical Trial
In September 1999, Genelabs announced positive
results of its second Phase III clinical trial of
GL701 for SLE. The study enrolled 381 women
with SLE randomized to receive either an oral
dose of 200 mg of GL701 or placebo once a day
for 12 months. The study was designed to
determine whether GL701 can improve or
stabilize clinical outcome and disease symptoms
in patients with SLE. Efficacy was measured by
the response of the patients to the treatment
(disease activity was stable or improved) utilizing
measurement tools including Systemic Lupus
Erythematosus Disease Activity Index
(SLEDAI), Systemic Lupus Activity Measure
(SLAM), Krupp Fatigue Severity Score (KFSS),
and Patient Global Assessment.
Based on the strength of preliminary data from
this study and the results of the first Phase III
clinical trial, the company intends to submit a
New Drug Application (NDA) for the treatment
of SLE with GL701. Genelabs has requested a
pre-NDA meeting with the FDA and intends to
begin the filing process as soon as possible
following that meeting.
Earlier this year the FDA granted Fast Track
designation to GL701 for SLE, which means that
the FDA has determined that GL701 is intended
to treat a serious or life-threatening condition for
which there is no adequate therapy currently
available. This designation also means that the
FDA can take actions to expedite the review of
the NDA including assigning priority review
status. It also allows the FDA to approve a Fast
Track drug if it has an effect on a clinical or
surrogate endpoint that is likely to predict its
clinical benefit. The legal authority for the FDA
to designate a drug as a Fast Track drug was
created by the FDA Modernization Act of 1997.
The FDA also granted Orphan Drug designation
to GL701 for the treatment of lupus. Orphan
Drug designation provides seven years of
marketing exclusivity from the date of a drug's
approval. DHEA has not been approved by the
FDA for any indication.
What is Systemic Lupus Erythematosus?
Systemic lupus erythematosus (SLE), also called
lupus, is a debilitating, chronic, autoimmune
disease that causes inflammation of various parts
of the body, especially the skin, joints and
kidneys. In SLE, the immune system is
over-active and produces too many abnormal
antibodies that react with the body's own tissues.
The exact cause of lupus is not known, but
heredity, environment and hormonal changes
may be involved.
People With Lupus
Prevalence in the US is approximately
200,000 people
Approximately 90 percent of lupus patients
are women
Onset of disease occurs most often during the
child-bearing years
Afflicts women of all ethnic and
socioeconomic backgrounds; is somewhat
more prevalent in certain ethnic groups,
particularly among African-Americans
Health Impact of SLE
SLE is a devastating, life-long autoimmune
disease
Common signs and symptoms include severe
fatigue, arthritis, facial rash and unusual
sensitivity to sunlight as well as
inflammation of the lungs and heart
More serious medical conditions can include
life-threatening organ damage and severe
infection
Significantly impacts quality of life
There is no cure for SLE
More than 90 percent of patients in US live
more than 10 years after being diagnosed
Death can occur either from manifestations
of the disease or complications of current
therapy
No drug has been approved for the treatment
of SLE in the US in the past 40 years
Diagnosis
Diagnosis of lupus is difficult: symptoms
mimic other illnesses, are often vague, and
may come and go
It can take many years from the first signs of
the disease to diagnosis
Currently, there is no single laboratory test
used to diagnose SLE
A thorough review of a person's medical
history, along with an analysis of the results
obtained in routine laboratory tests, and some
specialized tests related to immune function
assist in the diagnosis of lupus
The American College of Rheumatology
(ACR) has established a list of 11 symptoms
or signs that help distinguish lupus from other
diseases. For a diagnosis of SLE, a person
should display four or more symptoms (the
symptoms do not all have to occur at the
same time)
Signs and Symptoms of SLE
Lupus is an unpredictable disease that can affect
any part of the body. There are many physical
and lifestyle changes that confront people with
lupus throughout the course of the disease. The
most common challenges that lupus patients
experience include:
Fatigue
This is a chronic problem that is
usually accompanied by joint pain and
stiffness. It can affect many aspects of
daily life, making it difficult for people
with lupus to function at work or
perform routine activities.
Photosensitivity
About one-third of people with lupus
are photosensitive. Skin rashes and/or
systemic symptoms can occur after
being exposed to ultraviolet light. This
reaction requires patients with lupus
to avoid direct, prolonged exposure to
the sun, which can limit outdoor
activity.
Changes in
Personal
Appearance
Depending on the severity of the
disease, appearance changes can
include skin rashes, facial swelling and
weight change. Some changes (such
as weight gain and swelling) often
occur as a result of the medications
used to treat lupus. These appearance
changes can become emotionally
challenging for lupus patients.
Changes in
Physical Ability
Arthritis, fatigue and the need for rest
and photosensitivity often prohibit
people with lupus from maintaining
normal work and social schedules.
Lupus patients can become frustrated
and feel isolated when they are unable
to participate in outdoor and/or
physical activities as a result of their
disease.
Effects of
Treatments
Potentially serious side effects of
current SLE treatments can have
adverse health consequences ranging
from mild to life-threatening.
Serious Medical Conditions Caused by or
Associated With SLE
Kidney Disease
Approximately 90 percent of people
with lupus will develop some degree
of kidney damage. Some lupus
patients will develop kidney disease
serious enough to require treatment
with high doses of corticosteroids,
cytotoxic agents, dialysis or renal
transplantation.
Central Nervous
System (CNS)
Disease
Neurologic manifestations of SLE are
common and vary from mild to severe.
CNS problems can include seizures,
memory loss, headache, confusion,
hearing and visual changes, muscle
weakness, depression and emotional
disturbances.
Pleuritis
Pleurisy (inflammation of the lining of
the lung) is the most common
respiratory manifestation in SLE.
Pleurisy symptoms include shortness
of breath, chest pain, and coughing up
blood or thick mucus.
Treatment of SLE
Approaches to the treatment of SLE vary based
on the clinical problems present and whether the
disease is active at a given time. Currently,
first-line therapy consists of prednisone (a
corticosteroid) and hydroxychloroquine (an
anti-malarial), the only medications that are FDA
approved for the treatment of lupus. Cytotoxic
drugs are sometimes used when the disease is
particularly severe, and other drugs such as
NSAIDs or anti-psychotics may be used when
appropriate for specific symptoms.
Corticosteroids
(Steroids)
Corticosteroids are very powerful
drugs that reduce inflammation in
various tissues of the body. Dosage
levels are determined based on disease
activity. The most commonly
prescribed corticosteroid is
prednisone. There are many
complications associated with
corticosteroid treatment. Side effects
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