Dyax Announces Underwriter`s Exercise of Over-allotment Option

CAMBRIDGE, Mass.--(Business Wire)--
Dyax Corp. (NASDAQ: DYAX) announced today that Deutsche Bank Securities Inc.
exercised in full its over-allotment option and will purchase an additional
1,113,862 shares of the Company`s common stock at a public offering price of
$2.02 per share, which will bring the aggregate net proceeds from the offering
to approximately $16.1 million. The over-allotment option was granted to the
underwriter by Dyax in connection with its recent agreement to sell
approximately 7.4 million shares of its common stock. The offering of both the
initial and the over-allotment shares is expected to close on or about June 30,
2009.

Deutsche Bank Securities Inc. was the sole underwriter for the offering.

The offering was made pursuant to a shelf registration statement that has been
filed with and declared effective by the Securities and Exchange Commission.
Additional information and details with respect to the offering are included in
a prospectus supplement and related prospectus that was filed with the
Securities and Exchange Commission on June 25, 2009. The prospectus supplement
and the related prospectus may be obtained from Deutsche Bank Securities Inc.,
Attn: Prospectus Department, 100 Plaza One, Jersey City, New Jersey 07311,
telephone: (800) 503-4611 or e-mail at prospectusrequest@list.db.com.

This press release shall not constitute an offer to sell or the solicitation of
an offer to buy, nor shall there be any sale of these securities in any state in
which such offer, solicitation or sale would be unlawful prior to registration
or qualification under the securities laws of any such state.

About Dyax

Dyax is focused on advancing novel biotherapeutics for unmet medical needs, with
an emphasis on inflammatory and oncology indications. Dyax utilizes its
proprietary drug discovery technology to identify antibody, small protein and
peptide compounds for clinical development. Dyax`s lead product candidate is
DX-88 (ecallantide), a recombinant small protein that is currently being
evaluated for its therapeutic potential in two separate indications. On June 1,
2009, Dyax submitted a response to the FDA`s Complete Response letter regarding
the review of Dyax`s Biologics License Application (BLA) of DX-88 for the
treatment of hereditary angioedema (HAE). The FDA accepted the submission and
assigned Dyax`s BLA a new Prescription Drug User Fee Act (PDUFA) action date of
December 1, 2009. DX-88 has orphan drug designation in the U.S. and E.U., as
well as Fast Track designation in the U.S., for this indication. Additionally,
DX-88 is being evaluated in Phase 2 trials for the prevention of blood loss
during on-pump cardiothoracic surgery (CTS), which are being conducted by Dyax`s
partner, Cubist Pharmaceuticals. Dyax licensed to Cubist the intravenous
formulation of DX-88 for surgical indications in North America and Europe. DX-88
and other compounds in Dyax`s pipeline were identified using its patented phage
display technology, which rapidly selects compounds that bind with high affinity
and specificity to therapeutic targets. Dyax leverages this technology broadly
with over 70 revenue generating licenses and collaborations for therapeutic
discovery, as well as in non-core areas such as affinity separations, diagnostic
imaging, and research reagents. Dyax is headquartered in Cambridge,
Massachusetts. For online information about Dyax Corp., please visit
www.dyax.com.

Dyax Disclaimer

This press release contains forward-looking statements, including statements
regarding Dyax`s proposed sale of common stock. Statements that are not
historical facts are based on Dyax`s current expectations, beliefs, assumptions,
estimates, forecasts and projections about the industry and markets in which
Dyax competes. The statements contained in this release are not guarantees of
future performance and involve certain risks, uncertainties and assumptions,
which are difficult to predict. Therefore, actual outcomes and results may
differ materially from what is expressed in such forward-looking statements.
Important factors that could affect the use of proceeds from the offering
include the risk that DX-88 could take a significantly longer time to gain
regulatory approval than Dyax expects or may never gain approval and other risk
factors included in Dyax`s most recent Annual Report on Form 10-K filed with the
Securities and Exchange Commission as supplemented by its quarterly reports on
Form 10-Q. Dyax cautions investors not to place undue reliance on the
forward-looking statements contained in this release. These statements speak
only as of the date of this release, and Dyax undertakes no obligations to
update or revise these statements, except as may be required by law.

Dyax and the Dyax logo are registered trademarks of Dyax Corp.

Dyax Corp.
George Migausky, 617-250-5733
Executive Vice President
and Chief Financial Officer
gmigausky@dyax.com
or
Nicole Jones, 617-250-5744
Director, Investor Relations and
Corporate Communications
njones@dyax.com

Copyright Business Wire 2009