EXHIBIT 99.1

    Immunomedics Regains North American Development Rights from Amgen for
                                   Epratuzumab

MORRIS PLAINS, N.J. & THOUSAND OAKS, Calif.--(BUSINESS WIRE)--April 8,
2004--Immunomedics, Inc. (Nasdaq:IMMU) and Amgen Inc. (Nasdaq:AMGN) today
announced that Amgen has returned to Immunomedics all rights for epratuzumab,
the humanized CD22 monoclonal antibody therapeutic licensed to Amgen by
Immunomedics in December 2000, including rights to second generation molecules
and conjugates.

As part of the transaction, Immunomedics has agreed to issue to Amgen a 5-year
warrant to purchase 100,000 shares of the Company's common stock with a strike
price equal to $16.00 per share. Amgen will receive a final payment of $600,000
from Immunomedics if epratuzumab is approved for commercialization in the United
States for non-Hodgkin's lymphoma therapy. There are no other financial
obligations between the parties as a result of the agreement.

Roger M. Perlmutter, M.D., Ph.D., executive vice president of Research and
Development at Amgen, stated, "Our relationship with Immunomedics has been
positive. Phase 2 data demonstrate that epratuzumab is active against NHL.
Epratuzumab was also shown to be safe and well-tolerated when administered as a
single agent or in combination with rituximab (Rituxan). Our transfer of
preclinical and clinical data to Immunomedics will aid their efforts to develop
epratuzumab, in which endeavors we wish them well."

Immunomedics' president and chief executive officer, Cynthia L. Sullivan,
commented, "Amgen has been an excellent partner, and we are pleased with their
decision to transfer the epratuzumab program to us. By regaining North American
and Australian rights to our product, we can now discuss worldwide licensing of
this product with other interested companies. Since epratuzumab is currently
being tested in patients with autoimmune disease, we anticipate that it also may
have utility in this group of indications."

To date, epratuzumab has been studied, either alone or in combination with
rituximab, in over 300 patients with indolent or aggressive non-Hodgkin's
lymphomas, which are newly diagnosed in more than 50,000 patients annually in
the United States, and where there are over 350,000 patients being followed with
this disease.

About Immunomedics

Immunomedics is a biopharmaceutical company focused on the development,
manufacture and commercialization of diagnostic imaging and therapeutic products
for the detection and treatment of cancer and other serious diseases. Integral
to these products are highly specific monoclonal antibodies and antibody
fragments designed to deliver radioisotopes and chemotherapeutic agents to
tumors and other sites of disease. Immunomedics has nine therapeutic product
candidates in clinical development and has two marketed diagnostic imaging
products. The most advanced therapeutic product candidates are LymphoCide(R)
(epratuzumab), for which certain Phase II clinical trials for the treatment of
non-Hodgkin's lymphoma have already been completed, and CEA-Cide(R)
(labetuzumab), which is in Phase I/II clinical trials for the treatment of
certain solid tumors.

This release, in addition to historical information, contains forward-looking
statements made pursuant to the Private Securities Litigation Reform Act of
1995. Such statements, including statements regarding clinical trials, involve
significant risks and uncertainties and actual results could differ materially
from those expressed or implied herein. Factors that could cause such
differences include, but are not limited to, risks associated with new product
development (including clinical trials outcome and regulatory
requirements/actions), competitive risks to marketed products and availability
of financing and other sources of capital, as well as the risks discussed in the
Company's Annual Report on Form 10-K for the year June 30, 2003.

About Amgen

Amgen is a global biotechnology company that discovers, develops, manufactures
and markets important human therapeutics based on advances in cellular and
molecular biology.

This news release contains forward-looking statements that involve significant
risks and uncertainties, including those discussed below and others that can be
found in Amgen's Form 10-K for the year ended December 31, 2003, and in Amgen's
periodic reports on Form 10-Q and Form 8-K. Amgen is providing this information
as of the date of this news release and does not undertake any obligation to
update any forward-looking statements contained in this document as a result of
new information, future events or otherwise.

No forward-looking statement can be guaranteed and actual results may differ
materially from those we project. Amgen's results may be affected by its ability
to successfully market both new and existing products domestically and
internationally, sales growth of recently launched products, difficulties or
delays in manufacturing its products, and regulatory developments (domestic or
foreign) involving current and future products and manufacturing facilities. In
addition, sales of Amgen's products are affected by reimbursement policies
imposed by third party payors, including governments, private insurance plans
and managed care providers, and may be affected by domestic and international
trends toward managed care and healthcare cost containment as well as possible
U.S. legislation affecting pharmaceutical pricing and reimbursement. Government
regulations and reimbursement policies may affect the development, usage and
pricing of Amgen's products. Furthermore, Amgen's research, testing, pricing,
marketing and other operations are subject to extensive regulation by domestic
and foreign government regulatory authorities. Amgen or others could identify
side effects or manufacturing problems with its products after they are on the
market. In addition, Amgen competes with other companies with respect to some of
its marketed products as well as for the discovery and development of new
products. Discovery or identification of new product candidates cannot be
guaranteed and movement from concept to product is uncertain; consequently,
there can be no guarantee that any particular product candidate will be
successful and become a commercial product. In addition, while Amgen routinely
obtain patents for its products and technology, the protection offered by its
patents and patent applications may be challenged, invalidated or circumvented
by its competitors. Further, some raw materials, medical devices and component
parts for Amgen's products are supplied by sole third party suppliers.