Filed by Vertex Pharmaceuticals Incorporated
                          Pursuant to Rule 425 under the Securities Act of 1933
                          Subject Company: Aurora Biosciences Corporation
                          Commission File Number: 000-22669

JULY 6, 2001.


                           HART-SCOTT-RODINO CLEARANCE

CAMBRIDGE, MA AND SAN DIEGO, CA, JULY 6, 2001 -- Vertex Pharmaceuticals
Incorporated (Nasdaq:VRTX) and Aurora Biosciences Corporation (Nasdaq: ABSC)
today announced that the United States Federal Trade Commission (FTC) has
granted clearance under the Hart-Scott-Rodino Antitrust Improvements Act of 1976
with respect to Vertex's planned acquisition of Aurora. The transaction remains
subject to a favorable vote by Vertex and Aurora shareholders at special
meetings scheduled by both companies for July 18, 2001 and other customary
closing conditions.

Vertex and Aurora announced on April 30, 2001 that they had entered into a
definitive agreement whereby Vertex would acquire Aurora in a stock-for-stock
transaction. Under the terms of the agreement, each share of Aurora common stock
will convert into shares of newly issued Vertex common stock at a fixed ratio of
0.62 shares of Vertex common stock for each share of Aurora common stock.

The Hart-Scott-Rodino Antitrust Improvements Act of 1976 requires that parties
to certain mergers and acquisitions file notification with federal antitrust
authorities and obtain clearance prior to consummation of the proposed merger or
acquisition. The statute is intended to identify transactions involving
competitive overlaps between the parties. The statute imposes a 30-day waiting
period during which time the government reviews the competitive aspects of the


Vertex Pharmaceuticals Incorporated is a global biotechnology company. Vertex
seeks to discover, develop, and commercialize major pharmaceutical products
independently and with partners. Chemogenomics, Vertex's proprietary,
systematic, genomics-based platform, is designed to accelerate the discovery of
new drugs and to expand intellectual property coverage of drug candidate
compounds and classes of related compounds. This approach, which targets gene
families, has formed the basis for several commercial collaborations that retain
rights to downstream revenue for Vertex. Vertex's first approved product is
Agenerase(R) (amprenavir), an HIV protease inhibitor, which Vertex co-promotes
with GlaxoSmithKline. Vertex has 12 drug candidates in development to treat
viral diseases, inflammation, cancer, autoimmune diseases and neurological


Aurora Biosciences Corporation is a drug discovery company that uses proprietary
advances in biology, chemistry and automation to accelerate the discovery of new
medicines. Aurora's core technologies include a broad portfolio of proprietary
fluorescence assay technologies and screening platforms designed to provide an
integrated solution for drug discovery. Aurora's fluorescence assay technologies
include GeneBLAzer(TM), GenomeScreen(TM), PhosphoryLIGHT(TM) and Vivid(TM)
technologies, as well as a broad collection of fluorescent proteins.

Aurora's screening platforms include an ultra-high-throughput screening system,
the UHTSS(R) Platform, Aurora's automated master compound store, the AMCS, and
an ion channel technology screening platform, which includes Aurora's
proprietary voltage sensor probes and a voltage ion probe reader, the VIPR(TM)
subsystem. Aurora also provides assay development and screening services as part
of its drug discovery collaborations. Aurora's Big Biology(TM) initiative is an
internal drug discovery program focused on the identification of promising
preclinical candidates within all major classes of gene targets. Aurora's
technologies and drug discovery capabilities have been commercially validated by
over 20 major life sciences companies and research organizations, including
American Home Products, Bristol-Myers Squibb, Ceres, Cystic Fibrosis Foundation,
Eli Lilly, Families of SMA, GlaxoSmithKline, Genentech, Johnson & Johnson,
Merck, NV Organon Laboratories, Pfizer, Pharmacia and Roche.

                                   -- more --

Investors and security holders are advised to read the joint proxy
statement/prospectus regarding the proposed merger as filed with the Securities
and Exchange Commission, because it contains important information. Such joint
proxy statement/prospectus has been filed with the Securities and Exchange
Commission by Vertex and Aurora. The joint proxy statement/prospectus has been
sent to stockholders of Vertex and Aurora seeking their approval of the proposed
transaction. Investors and security holders may obtain a free copy of the joint
proxy statement/prospectus and other documents filed by Vertex and Aurora at the
Securities and Exchange Commission's web site at The joint proxy
statement/prospectus and such other documents may also be obtained from Vertex
by directing such request to Vertex Pharmaceuticals, 130 Waverly Street,
Cambridge, MA 02139, Attn: Investor Relations, tel: (617) 444-6100; e-mail: The joint proxy statement/prospectus and such other
documents may also be obtained from Aurora by directing such request to Aurora
Biosciences, 11010 Torreyana Road, San Diego, CA 92121, Attn: Investor
Relations, tel: 858-404-6600; e-mail:

Vertex and Aurora and their respective directors, executive officers and certain
members of management and employees may be soliciting proxies from Vertex and
Aurora stockholders in favor of the adoption of the merger agreement and the
transactions associated with the merger. A description of any interests that
Vertex and Aurora directors and executive officers have in the merger are
available in the joint proxy statement/prospectus.

Agenerase(R) is a trademark of the GlaxoSmithKline group of companies.
Aurora Biosciences(R), Big Biology(TM), GeneBLAzer(TM), GenomeScreen(TM),
PhosphoryLIGHT(TM), UHTSS(TM), VIPR(TM) and Vivid(TM) are trademarks of Aurora
Biosciences Corporation.

                                      # # #

Vertex's press releases are available at


Lynne H. Brum, Vice President, Corporate Communications and Market Development,
(617) 444-6614, or
Katie Burns, Manager, Investor Relations, (617) 444-6656


Doug Farrell, Senior Director, Investor Relations and Corporate Communications
Telephone: (858) 404-6767
Fax: (858) 404-6714