Positive Phase I and Pre-Clinical Data Suggest Acambis' M2e-Based Universal Influenza Vaccine, ACAM-FLU-A(TM), Could Tackle Infl
January 03 2008 - 4:11AM
Business Wire
Acambis plc (Acambis) (LSE:ACM), a leading vaccine development
company, today announced positive data from two trials of its
universal influenza vaccine ACAM-FLU-A�. The novel vaccine targets
the M2e peptide, which is found unchanged on the surface of all �A�
strains of the influenza virus, including all pandemic influenza
strains. As such, this vaccine could overcome the current need to
adapt influenza vaccines every year to correspond to circulating
strains. The Phase 1 clinical trial showed the vaccine to be well
tolerated and immunogenic and the pre-clinical challenge study
suggests that this M2e-based vaccine can protect against highly
pathogenic viruses such as pandemic influenza strains, including
H5N1. Currently, influenza vaccines are regularly reformulated
owing to the rapid mutation of the virus. ACAM-FLU-A� combines the
conserved M2e peptide with a carrier molecule from Hepatitis B,
which is used to help stimulate the immune system. This novel
vaccine design means that ACAM-FLU-A� could potentially provide
protection against �A� strains of influenza. Historically,
influenza pandemics have only been caused by �A� strains of the
virus. Therefore ACAM-FLU-A� has potential both as a vaccine
against pandemic influenza and as part of seasonal influenza
vaccination. The Phase 1 trial was a double-blind,
placebo-controlled study conducted at three centres in the USA. The
study consisted of four arms: placebo, ACAM-FLU-A� alone or
combined with aluminium hydroxide or QS-21. Healthy volunteers aged
between 18 and 40 were given two doses 30 days apart, their immune
response against the M2 protein was tested after 60 days and any
adverse events to the vaccine were recorded. The vaccine was shown
to be immunogenic and well-tolerated, with no serious adverse
events. Whilst immune responses were seen in all the vaccinated
groups, blood tests showed that the highest immune responses
occurred in the group who received ACAM-FLU-A� with QS-21. In this
group, 90% of people who received ACAM-FLU-A� plus QS-21 had
antibodies to the M2 protein in their system. QS-21 Stimulon�
adjuvant is an investigational adjuvant (immune stimulant) provided
under an agreement with Antigenics Inc., which has recently been
converted to a non-exclusive license and supply agreement. The
pre-clinical study tested the ability of an M2e-based vaccine to
protect against the Vietnam 2004 strain(1) of H5N1 avian influenza
(bird flu). The H5N1 virus was lethal in the placebo-treated group,
whereas 70% of those in the group vaccinated with the M2e-based
vaccine from the same influenza strain were protected. Dr Michael
Watson, Executive Vice President, Research & Development at
Acambis commented: �Taken together, the data from these two trials
demonstrate the potential of Acambis� approach to offer protection
against �A� strains of the influenza virus, including pandemic
influenza strains. As a universal vaccine, ACAM-FLU-A� can
potentially overcome many of the drawbacks of existing influenza
vaccines. It can be manufactured at any time of the year, and could
be stockpiled in advance of a pandemic or potentially used
routinely to ensure population protection against future
pandemics.� Following these results, Acambis will explore
partnering in parallel with continued development of ACAM-FLU-A�.
About Acambis Acambis is a leading vaccine company developing novel
vaccines that address significant unmet medical needs or
substantially improve standards of care. ChimeriVax�-JE, Acambis�
most advanced product in its development-stage pipeline, has to
date shown an excellent safety and efficacy profile following
pivotal Phase 3 trials. It is currently undergoing paediatric
trials in India and is partnered with Sanofi Pasteur and Bharat
Biotech. Acambis� proprietary ChimeriVax� technology, developed in
association with St Louis University, has also been used to develop
ChimeriVax�-West Nile, which is undergoing Phase 2 clinical
testing, making it the most advanced investigational vaccine
against the West Nile virus. Acambis has established a global
collaboration with Sanofi Pasteur for further development and
commercialisation of the vaccine. ChimeriVax� has also been applied
to development of Sanofi Pasteur�s tetravalent dengue vaccine,
which has successfully demonstrated proof-of-concept in a Phase 2
trial by generating 100% seroconversion to all four dengue virus
serotypes. Acambis also has the only vaccine in development against
Clostridium difficile bacteria, a leading cause of
hospital-acquired infections. C. difficile is estimated to cause at
least 360,000 cases of C. difficile-associated disease in the US
alone with annual costs to the healthcare system of $3.2bn.
Acambis� influenza programme aims to develop a universal vaccine
against influenza, for which a universal �A� strain vaccine,
ACAM-FLU-A�, has completed a Phase 1 trial. It also includes
various further vaccine candidates in the research and pre-clinical
stages. Acambis is recognised internationally as the leading
producer of smallpox vaccines. Acambis� ACAM2000� (Smallpox
(Vaccinia) Vaccine, Live) vaccine for active immunisation against
smallpox disease for persons determined to be at high risk for
smallpox infection was licensed by the US Food and Drug
Administration in August 2007. Acambis has manufactured doses of
ACAM2000� for emergency-use stockpiles held by the US Government
and several other governments around the world. For safety and
prescribing information, please refer to www.acambis.com/ACAM2000.
Acambis is based in Cambridge, UK and Cambridge, Massachusetts, US,
and is listed on the London Stock Exchange (ACM). More information
is available at www.acambis.com. About influenza and influenza
vaccines Today, seasonal influenza represents the single largest
vaccine market in the world, worth an estimated $2.2bn and
projected to grow to $4bn by 2010(3). It is still a major global
threat, which the WHO estimates causes between 250,000 and 500,000
deaths every year around the world(2)..Immunity against influenza
viruses, whether acquired by natural infection or immunisation, is
typically transient due to the virus�s ability to mutate and evade
pre-existing immunity. Accordingly, current licensed vaccines are
updated on an annual basis to target most effectively the presently
circulating strains. Pandemic influenza viruses are sufficiently
distinct from seasonal epidemic viruses that new vaccines must be
developed to address them. Pandemic influenza vaccines, primarily
targeting avian H5N1 viruses, are being stockpiled for emergency
use. However, the efficacy of these vaccines may be negatively
impacted by continual mutations in circulating H5N1 strains.
Experts believe the next pandemic could cause disease in two
billion people. Based on best-case scenarios modelled on the mild
pandemic of 1968, this could result in two to seven million deaths.
However, if the death toll associated with the 1918 influenza virus
were applied to today�s world population, there could be 180 to 360
million deaths globally.(4) Currently, influenza vaccines are
reformulated, generally each year, to address mutations in
influenza strains (known as �antigenic drift�). Preparations are
ongoing around the world for a potential pandemic, which would
result from a major genetic change in the influenza virus (known as
�antigenic shift�). The need to change vaccine formulations each
year results in delays in initiating vaccination programmes. In
addition, it is estimated that vaccine producers would need between
three and six months to product a strain-specific vaccine against a
pandemic strain. About ACAM-FLU-A� ACAM-FLU-A� is a recombinant
vaccine that uses a hepatitis B core protein (HBc) to present M2e,
the extracellular domain of the ion channel protein M2(5). M2 is
one of the three proteins expressed on the surface of the �A�
strain influenza virus and of infected cells alongside
haemagglutinin (HA) and neuraminidase (NA). Unlike HA and NA, M2 is
highly conserved, albeit under natural conditions not easily
recognised by the immune system. M2e could elicit an immune
response to all influenza �A� strains. As such, ACAM-FLU-A� has the
potential to be both a universal pandemic or pre-pandemic influenza
vaccine and part of a universal seasonal vaccine. Historically,
influenza pandemics have been caused by �A� strains of the virus
while seasonal vaccines target both �A� and �B� strains of the
virus. References (1) The Vietnam 2004 Clade 1 avian influenza
virus has been used by manufacturers to develop and produce
pre-pandemic vaccines.
http://www.who.int/csr/disease/avian_influenza/guidelines/recommendati
onvaccine.pdf (Due to its length, this URL may need to be
copied/pasted into your Internet browser's address field. Remove
the extra space if one exists) (2) WHO:
http://www.who.int/mediacentre/factsheets/fs211/en/ (3) Datamonitor
(4) Kamps-Hoffmann-Preiser, Influenza Report 2006 (5) Neirynck et
al., Nature Medicine, 5, 1157, 1999 �Safe Harbour� statement
Statements contained within this news release may contain
forward-looking comments, which involve risks and uncertainties
that may cause actual results to vary from those contained in the
forward-looking statements. In some cases, you can identify such
forward-looking statements by terminology such as 'may', 'will',
'could', 'forecasts', 'expects', 'plans', 'anticipates',
'believes', 'estimates', 'predicts', 'potential', or 'continue'.
Predictions and forward-looking references in this news release are
subject to the satisfactory progress of research which is, by its
very nature, unpredictable. Forward projections reflect
management's best estimates based on information available at the
time of issue.
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