BioCryst Broad-Spectrum Antiviral BCX4430 Highly Effective against Yellow Fever in a Preclinical Disease Model

  BioCryst Broad-Spectrum Antiviral BCX4430 Highly Effective against Yellow
  Fever in a Preclinical Disease Model

         Results to be presented at the 2^nd Antiviral Congress today

2nd Antiviral Congress

Business Wire

RESEARCH TRIANGLE PARK, N.C. -- November 12, 2012

BioCryst Pharmaceuticals, Inc. (NASDAQ:BCRX) today announced
proof-of-principle data demonstrating that BCX4430 is efficacious and well
tolerated in a preclinical disease model for evaluating efficacy against
yellow fever virus infection. BCX4430 is the lead compound in BioCryst’s
broad-spectrum antiviral (BSAV) research program. The objective of BioCryst’s
BSAV program is to develop broad-spectrum parenteral and oral therapeutics for
viruses that pose a threat to national health and security.

A presentation entitled “BCX4430, an adenosine analog, with potent activity
against yellow fever virus in a hamster model,” will be presented by Dr.
Justin Julander at the 2nd Antivirals Congress in Cambridge, MA today at
5:10PM E.T.

These studies comprehensively evaluated the efficacious dose, dose duration,
and therapeutic use of parenteral BCX4430 in the treatment of yellow fever
infection. Syrian Golden Hamsters–a widely accepted model for establishing
efficacy against yellow fever —virus were inoculated intraperitoneally with
ten times the cell culture infectious dose (CCID[50]) of yellow fever virus
(Jimenez strain) and treated parenterally with BCX4430 administered either
once or twice daily for 4 to 7 days. In studies with treatment just prior to
infection or delayed up to 4 days after infection, BCX4430 treated animals had
significantly (p<0.001) improved survival (80–100%) compared to animals
receiving saline placebo (20-30%). It is important to note that in this model,
serum viral titers peak at day four after infection, indicating that BCX4430
has the potential to be an effective therapeutic when administered as
pre-exposure prophylaxis; as post-exposure prophylaxis during the virus
incubation period; and as a treatment during the prodromal period and
symptomatic disease. Treated animals also exhibited significantly lower viral
titers in serum, improved weight gain, and decreased liver damage as measured
by lower levels of alanine transaminase and aspartate transaminase.

In addition, BCX4430 demonstrated a wide therapeutic index of 50 with a
minimum effective dose of 4 mg/kg/day (p<0.05 vs control), as measured by
survival, and a maximum tolerated dose of 200 mg/kg/day, as measured by
percent weight change.

The study was conducted under the National Institute of Allergy and Infectious
Diseases’ (NIAID’s) Animal Models of Infectious Disease Program. Dr. Justin
Julander of Utah State University, who coordinates yellow fever testing under
the NIAID Program stated, “BCX4430 is an exciting, potential antiviral therapy
for the treatment of yellow fever virus infection, for which no approved
treatment currently exists. The level of efficacy observed for BCX4430 in
these studies compared to other antivirals evaluated against yellow fever is
exceptional. BCX4430 warrants further study and development as a potential
human therapeutic.”

“BioCryst’s BSAV research program has generated convincing evidence of
efficacy in preclinical studies, not only in the yellow fever model, but also
against other viruses studied in vitro and in vivo. BCX4430 represents an
exciting research stage project that could become a breakthrough for the
treatment of hemorrhagic fevers caused by flaviviruses and filoviruses. These
viruses are viewed by U.S. Government Agencies as high priority targets for
development of medical countermeasures,” said Dr. William P. Sheridan, Senior
Vice President & Chief Medical Officer of BioCryst Pharmaceuticals. “We are
seeking government funding to support development of BCX4430 as a medical
countermeasure for the protection of civilian and military populations, and
plan to announce additional data from the BSAV program in upcoming
publications and at scientific conferences.”

About the BSAV Program & BCX4430

The objective of BioCryst’s BSAV research program is to develop broad-spectrum
parenteral and oral therapeutics for viruses that pose a threat to health and
national security. The lead BSAV compound is BCX4430, an RNA dependent-RNA
polymerase inhibitor that has demonstrated broad-spectrum activity in multiple
viruses and a favorable preliminary preclinical safety profile. BioCryst plans
to develop these compounds in collaboration with US Government Agencies
following the Animal Rule regulatory pathway.

About BioCryst

BioCryst Pharmaceuticals designs, optimizes and develops novel small molecule
drugs that block key enzymes involved in infectious and inflammatory diseases.
BioCryst currently has two late-stage development programs: peramivir, a viral
neuraminidase inhibitor for the treatment of influenza, and ulodesine
(BCX4208), a purine nucleoside phosphorylase (PNP) inhibitor for the treatment
of gout. In addition, BioCryst is developing two preclinical compounds:
BCX5191, a nucleoside analog inhibitor of HCV RNA polymerase (NS5B) for
hepatitis C, and BCX4161, an oral inhibitor of plasma kallikrein for
hereditary angioedema. Utilizing state-of-the-art structure-guided drug design
and crystallography, BioCryst continues to discover innovative compounds with
the goal of addressing unmet medical needs of patients and physicians. For
more information, please visit the Company's website at

Forward-Looking Statements

This press release contains forward-looking statements, including statements
regarding future results, performance or achievements. These statements
involve known and unknown risks, uncertainties and other factors which may
cause BioCryst’s actual results, performance or achievements to be materially
different from any future results, performances or achievements expressed or
implied by the forward-looking statements. These statements reflect our
current views with respect to future events and are based on assumptions and
subject to risks and uncertainties. Given these uncertainties, you should not
place undue reliance on these forward-looking statements. Some of the factors
that could affect the forward-looking statements contained herein include:
that BioCryst may not receive government funding to support the further
development of BCX4430; that HHS/BARDA may further condition, reduce or
eliminate future funding of the peramivir program; that BioCryst or its
licensees may not be able to enroll the required number of subjects in planned
clinical trials of its product candidates and that such clinical trials may
not be successfully completed; that the company or its licensees may not
commence as expected additional human clinical trials with product candidates;
that the FDA may require additional studies beyond the studies planned for
product candidates or may not provide regulatory clearances which may result
in delay of planned clinical trials, clinical hold with respect to such
product candidate or the lack of market approval for such product candidate;
that ongoing and future preclinical and clinical development may not have
positive results; that the company or its licensees may not be able to
continue future development of current and future development programs; that
such development programs may never result in future product, license or
royalty payments being received; that the companies may not be able to retain
its current pharmaceutical and biotechnology partners for further development
of its product candidates or may not reach favorable agreements with potential
pharmaceutical and biotechnology partners for further development of product
candidates; that its actual cash burn rate may not be consistent with its
expectations; that 2012 operating expenses and cash usage will be within
management’s expected ranges. Please refer to the documents BioCryst files
periodically with the Securities and Exchange Commission, specifically
BioCryst’s most recent Annual Report on Form 10-K, Quarterly Reports on Form
10-Q, and current reports on Form 8-K, all of which identify important factors
that could cause the actual results to differ materially from those contained
in BioCryst’s projections and forward-looking statements.



BioCryst Pharmaceuticals, Inc.
Robert Bennett, +1-919-859-7910
Catherine Kyroulis, +1-212-301-7174
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