Filed by Cephalon, Inc.
                                                 pursuant to Rule 425 under the
                                                     Securities Act of 1933 and
                                                       deemed filed pursuant to
                                                  Rule 14a-12 of the Securities
                                                           Exchange Act of 1934
                                                   Commission File No.: 0-19119
                                                  Subject Company: Anesta Corp.

THE FOLLOWING IS A PRESS RELEASE DISSEMINATED BY CEPHALON, INC. ON JULY 17, 2000

CONTACT: SHERYL WILLIAMS                             ROGER EVANS
         Cephalon, Inc.                              Anesta Corp.
         610-738-6493                                801-401-7443

FOR IMMEDIATE RELEASE

CEPHALON AND ANESTA ANNOUNCE MERGER TO CREATE STRONGER, MORE PROFITABLE
PHARMACEUTICAL BUSINESS

         West Chester, PA and Salt Lake City, UT - July 17, 2000 - Cephalon,
Inc. (NASDAQ: CEPH) and Anesta Corp. (NASDAQ: NSTA) announced today that the two
companies have agreed to a merger under which Cephalon will acquire all of the
outstanding shares of Anesta in a tax-free, stock-for-stock transaction intended
to be accounted for as a pooling of interests. The transaction is expected to be
accretive to Cephalon's revenues and earnings in 2001 and beyond. Cephalon
develops and markets products to treat sleep and neurological disorders, and
cancer. Anesta is a leader in the development and commercialization of products
for the management of cancer pain and other therapeutic applications using its
patented oral transmucosal system (OTS-TM-) for drug delivery.

         Upon completion of the transaction, Anesta shareholders will receive
0.4765 shares of newly-issued Cephalon common stock for each share of Anesta
they own. Based on the closing price of Cephalon stock on July 14, 2000 of $66
per share, the total equity value of the transaction is approximately $444
million, or $31.45 per Anesta share. As part of the transaction, Anesta has
agreed to a termination fee of $15 million, which is payable under certain
conditions.

         The boards of directors of both companies have unanimously approved
the proposed merger, which is subject to the approval of Anesta shareholders,
regulatory agencies and customary closing conditions. The merger is expected
to be completed during the fourth quarter of 2000. Under the terms of the
merger agreement, Anesta will become a wholly owned subsidiary of Cephalon.

         Cephalon chairman and CEO Frank Baldino, Jr., Ph.D., stated, "We
believe the combination of Cephalon and Anesta will shorten Cephalon's time to
profitability and enable shareholders of both companies to realize continued
long-term growth through ownership of Cephalon shares. Anesta markets ACTIQ-R-,
a unique and rapidly growing product for breakthrough cancer pain, and has a
highly capable and recently expanded U.S. sales force. Merging with Anesta will
give Cephalon another high-growth product, complete our commercial integration
in oncology and enable us to apply Anesta's novel drug delivery technology to
the development of new products in both oncology and neurology."

                                  - continue -






Cephalon and Anesta Announce Merger
Page 2

         Anesta president and CEO Thomas King stated, "We believe a merger with
Cephalon will provide significant benefits to our shareholders and customers.
Cephalon is a leader in neuroscience and has developed a strong research and
development capability in oncology that fits perfectly with our drug development
and oncology marketing focus. We expect the combination of our pipelines,
products and organizations will create a stronger company with greater
opportunities for clinical and commercial success."

                  Three Key Products in the U.S., Stronger Pipeline

         The combined company will have three key marketed products in the
United States: PROVIGIL-R- (modafinil) Tablets [C-IV] is marketed for the
treatment of excessive daytime sleepiness associated with narcolepsy, and is
being developed for other potential uses; ACTIQ-R- (oral transmucosal fentanyl
citrate) is marketed for the treatment of breakthrough cancer pain, and pending
regulatory clearance will be launched in Europe through licensees Elan, Grupo
Ferrer, Laboratoire Lafon and Swedish Orphan; GABITRIL-R- (tiagabine
hydrochloride) is marketed under a co-marketing and co-development agreement
with Abbott Laboratories for the adjunctive treatment of partial seizures
associated with epilepsy.

         The combined company will have a broader pipeline of products in
clinical development, including new chemical entities to treat cancer and
neurodegenerative diseases, as well as new pharmaceutical products using its
patented oral transmucosal system (OTS-TM-), which is designed to provide
convenient, cost-effective therapy with rapid onset of action and
patient-controlled administration.

         Anesta is a leader in the development of new oral transmucosal
pharmaceutical products. In addition to its lead product, ACTIQ, the company has
other investigational product candidates in clinical development including;
OTSTM nicotine for smoking cessation, OTS fentanyl for acute pain management,
OTS etomidate for short-acting sedation, OTS piroxicam for mild to moderate
pain, OTS droperidol and OTS prochlorperazine for nausea and vomiting, and OTS
scopolamine for motion sickness.

         CEPHALON, INC., HEADQUARTERED IN WEST CHESTER, PENNSYLVANIA, IS AN
INTERNATIONAL BIOPHARMACEUTICAL COMPANY DEDICATED TO THE DISCOVERY, DEVELOPMENT
AND MARKETING OF PRODUCTS TO TREAT SLEEP DISORDERS, NEUROLOGICAL DISORDERS AND
CANCER.

         DR. BALDINO AND MR. KING WILL DISCUSS THE PROPOSED MERGER WITH ANALYSTS
AND INVESTORS ON A CONFERENCE CALL BEGINNING AT 10:00 AM EST. TO PARTICIPATE IN
THE CALL, DIAL 1-913-981-4900 AND REFER TO CONFERENCE CODE NUMBER 447475.




         In addition to historical facts or statements of current condition,
this press release may contain forward-looking statements that involve risks and
uncertainties. The companies describe certain of these risks and uncertainties
in their respective filings with the Securities and Exchange Commission,
including their respective Annual Reports on Form 10-K (including the section
entitled "Risk Factors" contained in Cephalon's Form 10-K), their most recent
quarterly reports on Form 10-Q and their Current Reports on Form 8-K. These
risks and uncertainties could cause the companies' actual results and experience
to differ materially from anticipated results and expectations expressed in
these forward-looking statements. You may identify some of these forward-looking
statements by the use of words in the statements such as "anticipate,"
"estimate," "expect," "project," "intend," "plan," "believe" or words and terms
of similar meaning. The forward-looking statements in this document include, but
are not limited to, statements regarding the timing of the merger and its impact
on revenue, growth, earnings and shareholder value, the accounting treatment for
the merger, the development of pharmaceutical products, and future financial and
operating results. Actual results may differ materially from those described
herein due to a number of factors including the ability to obtain all necessary
consents and approvals to the merger; unanticipated costs related to the merger;
risks related to the timing and successful integration of the combined
businesses; and other economic, business, competitive and/or regulatory factors
affecting Cephalon's and Anesta's businesses generally. Given these risks and
uncertainties, any or all of these forward-looking statements may prove to be
incorrect. Therefore, you should not rely on any such factors or forward-looking
statements. Furthermore, the companies do not intend (and are not obligated) to
update publicly any forward-looking statements. This discussion is permitted by
the Private Securities Litigation Reform Act of 1995.

         The foregoing may be deemed to be offering materials of Cephalon, Inc.
in connection with the proposed merger of Cephalon, Inc. and Anesta Corp. on the
terms and conditions in the Agreement and Plan of Merger, dated as of July 14,
2000, among Cephalon, Inc., C Merger Sub Inc., and Anesta Corp.

         STOCKHOLDERS OF ANESTA AND OTHER INVESTORS ARE URGED TO READ THE PROXY
STATEMENT/PROSPECTUS THAT WILL BE INCLUDED IN THE REGISTRATION STATEMENT ON FORM
S-4 THAT CEPHALON WILL FILE WITH THE SEC IN CONNECTION WITH THE PROPOSED MERGER
BECAUSE IT WILL CONTAIN IMPORTANT INFORMATION ABOUT CEPHALON, ANESTA, THE
MERGER, THE PERSONS SOLICITING PROXIES IN THE MERGER AND THEIR INTERESTS IN THE
MERGER AND RELATED MATTERS. After it is filed with the SEC, the proxy
statement/prospectus will be available free of charge, on the SEC's web site
(http://www.sec.gov), or by directing a written or oral request for copies to
either John E. Osborn, Senior Vice President, General Counsel and Secretary,
Cephalon Inc., 145 Brandywine Parkway, West Chester, PA 19380 (610-344-0200) or
Roger Evans, Vice President, Finance and Administration, Anesta Corp., 4745
Wiley Post Way, Salt Lake City, UT 84116 (801-595-1405).

         Cephalon and Anesta also file annual, quarterly and special reports,
proxy statements and other information with the SEC. You may read and copy
any reports, statements or other information filed by either company at the
SEC's public reference rooms at 450 Fifth Street, N.W., Washington, DC 20549
or at the SEC's other public reference rooms in New York, New York and
Chicago, Illinois. These filings are also available on the SEC's web site at
HTTP://WWW.SEC.GOV.

NOTE: Cephalon's and Anesta's press releases are posted on the Internet at the
companies Web sites at WWW.CEPHALON.COM and WWW.ANESTA.COM. They are also
available by fax 24 hours a day at no charge by calling PR Newswire's Company
News On-Call at 800-758-5804, extension 134563.

                                      # # #




THE FOLLOWING IS THE SCRIPT TO A CEPHALON, INC. CONFERENCE CALL ON JULY 17,
2000:

                                 CEPHALON, INC.

                             MODERATOR: JASON RUBIN

                        REMARKS FOR 7/17 CONFERENCE CALL

JASON RUBIN

Good morning. Earlier today Cephalon and Anesta announced the agreement approved
by their boards of directors to merge the two companies. With us this morning to
discuss the proposed transaction are Frank Baldino, Jr., chairman and chief
executive officer of Cephalon, and Tom King, Anesta's president and chief
executive officer. Kevin Buchi, Cephalon's senior vice president and chief
financial officer, and Bob Roche, Cephalon's senior vice president of sales and
marketing are also with us this morning to help answer your questions.

Before we begin, you are reminded that certain statements on this call are
forward-looking statements that involve risks and uncertainties. These
forward-looking statements may include statements regarding the timing of the
merger and its impact on revenue, growth, earnings, operations and shareholder
value, the accounting treatment for the merger, the development of
pharmaceutical products, and future financial and operating results. Additional
information on factors that may affect the business and financial results of the
companies can be found in filings of the companies with the Securities and
Exchange Commission.

Now I am pleased to introduce Dr. Frank Baldino, Jr., chairman and CEO of
Cephalon. Frank.

FRANK BALDINO

Thank you, Jason, and good morning everyone.

Today's announcement marks an important turning point for both companies. The
proposed merger with Anesta presents the opportunity to achieve a number of
important objectives and milestones. I believe it will:

     -    accelerate Cephalon's revenue and earnings growth next year and
          beyond, and

     -    make Cephalon profitable sooner.

It will also:

     -    add Actiq, a rapidly growing product for breakthrough cancer pain, to
          Cephalon's portfolio,

     -    complete Cephalon's commercial integration in oncology, and

     -    add a novel drug delivery platform for development of new products in
          both oncology and neurology.

We believe this is a perfect match for us. Anesta has an exciting and growing
product in Actiq, a novel drug delivery technology, and the infrastructure to
sell products into the oncology community. Actiq's method for treating
breakthrough cancer pain is unique and its impact on patients is rapid and
profound. In this regard, Actiq is an excellent addition to our portfolio. I'm
also pleased to note that its sales have been growing rapidly. First quarter
2000 Actiq sales were up 57 percent compared to the fourth quarter of 1999, and
sales have continued to grow rapidly during the second quarter.

Cephalon has developed a technology platform that we believe will create
innovative drug therapies to treat many forms of cancer, and this transaction
would complete Cephalon's commercial integration in oncology and give us
access to an important medical specialty not presently served by Cephalon's
sales force. Coincidentally, Provigil may also have applications in oncology
because cancer specialists -- the same physicians Anesta's sales reps call on
today --have used Provigil to treat the fatigue associated with chemotherapy
and expressed interest in conducting studies of the drug for this indication.

We're also excited about Anesta's oral transmucosal system, which provides a
rapid onset of activity and has potential applications in a number of areas.
Each of Anesta's OTS development programs represents innovative and promising
new product opportunities.

We believe there are positive synergies between our companies and that the
merger creates opportunities to build a much stronger business together. We
believe the merger will accelerate Cephalon's revenues and earnings growth, be
accretive to revenues and earnings in 2001 and beyond, and accelerate our path
to profitability. We expect the merger will close sometime during the fourth
quarter of 2000.




That concludes my formal remarks. Now I'm pleased to welcome Tom King to the
conference call for his comments on the transaction. Tom.

TOM KING

Thank you, Frank. This is a very exciting day for Anesta, its employees, its
customers, and its shareholders. We're extremely proud of what we have
accomplished to date, and look forward to an even brighter future as part of the
Cephalon organization.

Sales of our lead product, Actiq, have been very strong since we reacquired the
product from Abbott earlier this year and assumed responsibility for marketing
and selling it in the United States. It is a remarkable product for breakthrough
cancer pain -- simple to use, effective and patient-friendly. It has also
introduced a new drug delivery system, which we believe has great potential in a
variety of therapeutic areas.

We are developing a number of products using the OTS system for applications
including smoking cessation, pain management, short-term sedation, and nausea
and vomiting. We're excited about the potential of this system to deliver new
medications safely and effectively where patients need to have rapid relief
and be in control of their own therapy. Cephalon's expertise in neuroscience
and its rapidly expanding research programs in oncology will allow us to
identify many more applications for the OTS system.

I believe that this merger represents a unique strategic opportunity, that the
combination of our two companies will be greater than the sum of its parts, and
that our shareholders will derive greater long-term value through this merger.

That concludes my formal remarks. Now we would be pleased to take your
questions.