Isis Earns $7 Million in Milestone Payments from GSK for Advancement of ISIS-GSK3 Rx to Treat Viral Infection

   Isis Earns $7 Million in Milestone Payments from GSK for Advancement of
                    ISIS-GSK3 Rx to Treat Viral Infection

PR Newswire

CARLSBAD, Calif., Oct. 7, 2013

CARLSBAD, Calif., Oct. 7, 2013 /PRNewswire/ --Isis Pharmaceuticals, Inc.
(NASDAQ: ISIS) announced today that GlaxoSmithKline (GSK) has added a
development candidate ISIS-GSK3[Rx], to its collaboration with Isis. Isis
earned $7 million in milestone payments associated with the advancement of
this program. ISIS-GSK3[Rx] is an antisense drug designed to inhibit the
production of an undisclosed target to treat a common viral infection. Isis
will develop ISIS-GSK3[Rx] to Phase 2 proof-of-concept, after which GSK has an
exclusive option to in-license the program and further develop and
commercialize the asset.

(Photo: http://photos.prnewswire.com/prnh/20130807/LA60006LOGO)

"We are pleased with the progress of our collaboration with GSK and look
forward to achieving further successes, including advancing ISIS-GSK3[Rx ]into
clinical studies. The benefit of GSK's expertise enables us to further expand
the breadth of our pipeline into areas where effective new therapies are
needed," said B. Lynne Parshall, chief operating officer of Isis.

As a part of the alliance, Isis is eligible to earn additional pre-licensing
milestone payments from GSK as ISIS-GSK3[Rx] advances. Isis is also eligible
to receive double-digit royalties on sales of ISIS-GSK3[Rx]. The alliance
applies Isis' antisense drug discovery platform to discover and develop new
therapeutics against targets for rare and/or serious diseases.

ABOUT ISIS PHARMACEUTICALS, INC.
Isis is exploiting its leadership position in antisense technology to discover
and develop novel drugs for its product pipeline and for its partners. Isis'
broad pipeline consists of 30 drugs to treat a wide variety of diseases with
an emphasis on cardiovascular, metabolic, severe and rare diseases, including
neurological disorders, and cancer. Isis' partner, Genzyme, is
commercializing Isis' lead product, KYNAMRO™, in the United States for the
treatment of patients with HoFH. Isis' patents provide strong and extensive
protection for its drugs and technology. Additional information about Isis is
available at www.isispharm.com.

ISIS PHARMACEUTICALS' FORWARD-LOOKING STATEMENT
This press release includes forward-looking statements regarding Isis'
strategic alliance with GlaxoSmithKline and the discovery, development and
therapeutic potential of ISIS-GSK3[Rx] for the treatment of viral infections.
Any statement describing Isis' goals, expectations, financial or other
projections, intentions or beliefs is a forward-looking statement and should
be considered an at-risk statement. Such statements are subject to certain
risks and uncertainties, particularly those inherent in the process of
discovering, developing and commercializing drugs that are safe and effective
for use as human therapeutics, and in the endeavor of building a business
around such drugs. Isis' forward-looking statements also involve assumptions
that, if they never materialize or prove correct, could cause its results to
differ materially from those expressed or implied by such forward-looking
statements. Although Isis' forward-looking statements reflect the good faith
judgment of its management, these statements are based only on facts and
factors currently known by Isis. As a result, you are cautioned not to rely
on these forward-looking statements. These and other risks concerning Isis'
programs are described in additional detail in Isis' annual report on Form
10-K for the year ended December 31, 2012, and its most recent quarterly
report on Form 10-Q, which are on file with the SEC. Copies of these and other
documents are available from the Company.

In this press release, unless the context requires otherwise, "Isis,"
"Company," "we," "our," and "us" refers to Isis Pharmaceuticals and its
subsidiaries.

Isis Pharmaceuticals® is a registered trademark of Isis Pharmaceuticals, Inc.
KYNAMRO™ is a trademark of Genzyme Corporation.

SOURCE Isis Pharmaceuticals, Inc.

Website: http://www.isispharm.com
Contact: D. Wade Walke, Ph.D., Vice President, Corporate Communications and
Investor Relations, 760-603-2741; Amy Blackley, Ph.D., Associate Director,
Corporate Communications, 760-603-2772