Filed by Advanced Magnetics, 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

                                       Subject Company: Advanced Magnetics, Inc.
                                                     Commission File No. 0-14732


ON JULY 10, 2000, CYTOGEN CORPORATION, A DELAWARE CORPORATION, AND ADVANCED
MAGNETICS, INC., A DELAWARE CORPORATION, JOINTLY ISSUED THE FOLLOWING PRESS
RELEASE:

                                                     
Contacts:
Richard W. Krawiec, Cytogen Corporation                 Jerome Goldstein, Advanced Magnetics, Inc.
Vice President, Investor Relations                      Chairman and Chief Executive Officer
and Corporate Communications                            617-497-2070 ext. 3030
609-750-8289




                      CYTOGEN TO ACQUIRE ADVANCED MAGNETICS

            STRATEGIC MERGER STRENGTHENS CYTOGEN'S ONCOLOGY PRESENCE,
          AS WELL AS PROVIDING PRODUCT, TECHNOLOGY AND CASH RESOURCES

Princeton, NJ and Cambridge, MA - July 10, 2000 - Cytogen Corporation (Nasdaq:
CYTO) and Advanced Magnetics, Inc. (AMEX: AVM) today jointly announced that they
have entered into a definitive merger agreement under which Cytogen will acquire
Advanced Magnetics, a developer of novel diagnostic pharmaceuticals for use in
magnetic resonance imaging (MRI). The transaction represents a strategic step
for Cytogen to broaden its oncology franchise, which it intends to leverage
through its proteomics business and the development of products using its
prostate specific membrane antigen (PSMA) technology. The two companies believe
that this stock-for-stock transaction, which includes products, technology, and
cash assets, is in the best interests of the shareholders of both companies and
provides the combined company with the following benefits:

o    The acquisition broadens Cytogen's medical oncology presence and
     strengthens its position in the area of cancer staging and detection, in
     which Cytogen currently markets two products, ProstaScint-Registered
     Trademark-, a prostate cancer imaging agent, and OncoScint CR/OV-Registered
     Trademark-, an imaging agent for ovarian and colorectal cancers.

o    Advanced Magnetics' near-term product, Combidex-Registered Trademark-, a
     MRI contrast agent for the detection of lymph node metastases, has produced
     promising clinical results and creates the potential for an enhanced
     revenue stream. The U.S. Food and Drug Administration (FDA) recently issued
     an approvable letter with respect to Combidex, following a priority review.




o    The combined company plans to utilize Cytogen's oncology sales and
     marketing organization for the expected launch of Combidex in the first
     half of 2001.

o    At March 31, 2000, Advanced Magnetics had $19.5 million in cash and
     marketable securities. The enhanced cash position created by the merger
     secures development resources and provides leverage to other areas of the
     combined business, including prostate cancer diagnostics and therapeutics
     based on PSMA technology and Cytogen's AxCell Biosciences proteomics
     subsidiary.

o    The combined development teams, which have been responsible for a total of
     five FDA approved products to date, will apply their expertise to obtaining
     and maintaining regulatory approvals and accelerating the commercial
     introduction of product candidates in the pipeline. One such product
     candidate is Advanced Magnetics' next-generation imaging agent, Code 7228,
     which is scheduled to enter Phase II clinical development later this year.
     Code 7228 is being developed for oncology and magnetic resonance
     angiography applications.

o    Cytogen gains cutting-edge, iron oxide-based imaging technology as well as
     a state-of-the-art manufacturing facility, and a patent portfolio
     consisting of 25 U.S. patents and additional U.S. and foreign pending
     patent applications. Cytogen plans to use Advanced Magnetics' Cambridge,
     Massachusetts, GMP facility for fill, finish, and distribution of two of
     Cytogen's existing products, ProstaScint and OncoScint CR/OV imaging
     agents.

Under the terms of the agreement, Cytogen will acquire all of Advanced
Magnetics' outstanding stock in a tax-free, stock-for-stock transaction
structured as a pooling of interests. Advanced Magnetics' shareholders will
receive $60 million in shares of Cytogen common stock. Each outstanding Advanced
Magnetics common share will be converted into $8.75 market value of Cytogen
common shares, subject to a collar on the price of Cytogen common stock ranging
from $8.55 to $11.56. The transaction is subject to approval by Advanced
Magnetics' shareholders and is expected to close in the third quarter of 2000.

"By growing Cytogen via a strategic, synergistic acquisition, we are aiming to
leverage the value of our existing assets and expertise to increase shareholder
value," said H. Joseph Reiser, Ph.D., Cytogen's Chief Executive Officer. "This
acquisition fits well with our continuing strategy to introduce specialized
cancer products that aid physicians in the diagnosis and staging of various
cancers using novel physiological targeting approaches. Since lymph nodes are
often the first sites to which cancer spreads from the primary tumor, such
staging information is critical in making the best treatment decisions. The
Advanced Magnetics acquisition goes hand in glove with our present prostate
cancer product and related development efforts, and their near-term product,
Combidex, could allow us to build a leading company in lymph-node-based cancer
staging and diagnosis. We estimate that in the broader oncology field there are
over 800,000 cancer patients in the United States who may benefit from lymph
node imaging."

"Advanced Magnetics' working capital should provide the combined company with
ready funding for the commercialization of Combidex, assuming final approval is
granted," added Dr. Reiser. "With the combined expertise of the two management
teams, we believe that we could be in a stronger position to accelerate other
corporate goals related to the development of immunotherapies, the acquisition
of new products, and the further acceleration of our proteomics initiative at
our wholly owned subsidiary, AxCell BioSciences."




"Cytogen provides a logical strategic fit for Advanced Magnetics' products and
personnel," said Jerome Goldstein, Chairman and CEO of Advanced Magnetics.
"Advanced Magnetics' technology and products have the potential to achieve
greater market penetration under the Cytogen umbrella than they do alone.
Therefore, I believe that the combination of the two companies is in the best
interests of both groups of shareholders. In addition, the timing of this
transaction is ideal. We recently received an initial action letter from the FDA
indicating that our Combidex MRI contrast agent for imaging of metastatic lymph
nodes was `approvable,' subject to certain conditions being satisfied. We
believe the combined company will be well positioned to launch and market this
product to oncologists upon anticipated final approval, given our combined
experience in the oncology marketplace with metastatic cancer detection and
Cytogen's recent deployment of a dedicated oncology sales force."

UBS Warburg LLC and SG Cowen Securities Corporation acted as the financial
advisors to Cytogen Corporation and Advanced Magnetics, respectively.

Cytogen Corporation is an established biopharmaceutical company in Princeton,
NJ, with two principal lines of business, proteomics and oncology. The Company
is extending its expertise in antibodies and molecular recognition to the
development of new products and a proteomics-driven drug discovery platform. The
Company has established a pipeline of product candidates based on its
proprietary antibody and prostate specific membrane antigen, or PSMA,
technologies. The Company, with Progenics Pharmaceuticals, Inc., has formed a
joint venture focusing on the development of cancer immunotherapies based on
PSMA technology. The Company's cancer management franchise currently comprises
three marketed FDA-approved products: ProstaScint-Registered Trademark-, used to
image the extent and spread of prostate cancer; OncoScint CR/OV-Registered
Trademark-, a diagnostic imaging agent for colorectal and ovarian cancer; and
Quadramet-Registered Trademark-, for the relief of cancer-related bone pain. The
Company's wholly owned subsidiary, AxCell Biosciences Corporation, is developing
a proprietary protein pathway database as a drug discovery and development tool
for the pharmaceutical and biotechnology industries. For additional information
on Cytogen, visit the Company's web sites at www.cytogen.com and
www.axcellbio.com.

Advanced Magnetics, Inc. is a biopharmaceutical company, with offices in
Cambridge, MA, and Princeton, NJ, dedicated to the development and
commercialization of pharmaceutical products for the diagnosis and treatment of
cancer and other diseases. Feridex I.V.-Registered Trademark-, the Company's
contrast agent used in MRI for the detection of liver lesions, is currently
marketed in the United States, Japan, western Europe, Argentina, Israel, China
and South Korea. GastroMARK-Registered Trademark-, for use in conjunction with
MRI to distinguish the loops of the bowel from other abdominal structures, is
marketed in the United States and western Europe. An approvable letter has been
received from the U.S. Food and Drug Administration for the Company's third
product, Combidex, for use in MRI to aid diagnosis of lymph node disease. The
Company's Research and Development efforts include Code 7228 for use in oncology
applications as well as MR angiography. For additional information on Advanced
Magnetics, visit the Company's web site at www.advancedmagnetics.com.




This release contains certain "forward-looking statements" within the meaning of
the Private Securities Litigation Reform Act of 1995. These statements are based
on managements' current expectations and are subject to uncertainty and changes
in circumstances. Actual results may vary materially from the expectations
contained in the forward-looking statements. The forward-looking statements in
this release include statements addressing the following subjects: expected date
of closing the acquisition; future financial and operating results; timing and
benefits of acquisition; expected regulatory approval and marketing of Combidex;
and enhanced product development efforts.

The following factors, among others, could cause actual results to differ
materially from those described in the forward-looking statements: failure of
the Advanced Magnetics' shareholders to adopt the agreement providing for
Cytogen's acquisition of Advanced Magnetics; the risk that the businesses of
Cytogen and Advanced Magnetics will not be integrated successfully; and other
economic, business, competitive and/or regulatory factors affecting Advanced
Magnetics' and Cytogen's businesses, the ability to satisfy the conditions
specified for final approval of Combidex for imaging of lymph nodes and to
resolve the final labeling for Combidex with the FDA.

More detailed information about these factors is set forth in Advanced
Magnetics' and Cytogen's filings with the Securities and Exchange Commission,
including Advanced Magnetics' Annual Report on Form 10-K for the fiscal year
ended September 30, 1999, Cytogen's Annual Report on Form 10-K for the fiscal
year ended December 31, 1999, their most recent Quarterly Reports on Form 10-Q
and Cytogen's Current Reports on Form 8-K. Advanced Magnetics and Cytogen are
under no obligation to (and expressly disclaim any such obligation to) update or
alter their forward-looking statements whether as a result of new information,
future events or otherwise.

Investors and security holders are advised to read the proxy
statement/prospectus regarding the business combination transaction referenced
in the foregoing information when it becomes available, because it will contain
important information. The proxy statement/prospectus will be filed with the
Securities and Exchange Commission by Advanced Magnetics, Inc. and Cytogen
Corporation. Investors and security holders may obtain a free copy of the proxy
statement/prospectus (when available) and other documents filed by Advanced
Magnetics and Cytogen at the Commission's web site at http://www.sec.gov. The
proxy statement/prospectus and such other documents may also be obtained from
Advanced Magnetics or from Cytogen by directing such request to Advanced
Magnetics, Inc., Attention: Corporate Secretary, 61 Mooney Street, Cambridge, MA
02138, telephone: (617) 497-2070; or Cytogen Corporation: Corporate Secretary,
600 College Road East, CN 5308, Princeton, NJ 08540, telephone: (609) 750-8200.

Advanced Magnetics and certain other persons referred to below may be deemed to
be participants in the solicitation of proxies of Advanced Magnetics'
shareholders to adopt the agreement providing for Cytogen's acquisition of
Advanced Magnetics. The participants in the solicitation may include the
directors and executive officers of Advanced Magnetics, who may have an interest
in the transaction, including as a result of holding shares or options of
Advanced Magnetics. A detailed list of the names and interests of Advanced
Magnetics' directors and executive officers is contained in Advanced Magnetics'
Proxy Statement for its most recent Annual Meeting, which may be obtained
without charge at the Commission's web site at http://www.sec.gov.