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                                                                  Exhibit 99.1

            ABGENIX AND MILLENNIUM BIOTHERAPEUTICS FORM COLLABORATION

  Collaboration Marks Fifth Corporate Deal for Abgenix and Start Of Development
            for Millennium BioTherapeutic's First Clinical Candidate

FREMONT, Calif., and CAMBRIDGE, Mass., July 15 /PRNewswire/ -- Abgenix, Inc.,
(Nasdaq: ABGX) and Millennium BioTherapeutics, Inc. (MBio), a majority-owned
subsidiary of Millennium Pharmaceuticals, Inc. (Nasdaq: MLNM) today announced
that they have signed an exclusive agreement to utilize Abgenix's XenoMouse(TM)
technology to develop an antibody drug candidate toward a proprietary,
biologically-validated target discovered by MBio.

Under the agreement, Millennium BioTherapeutics will use Abgenix's XenoMouse
technology to generate fully human antibodies to an undisclosed antigen target
in the area of inflammatory disease. In return, Abgenix will receive research
payments and could receive additional fees and milestone payments plus royalty
payments on future product sales by MBio. MBio will be responsible for product
development, manufacturing, and marketing of any products developed through the
collaboration. This is Abgenix's fifth corporate collaboration involving its
proprietary technology for generating fully human antibody product candidates
and is the start of preclinical development for MBio's first clinical candidate.

"We are pleased to be collaborating with Millennium BioTherapeutics, a leader in
the application of genomics to protein and antibody products," stated R. Scott
Greer, president and chief executive officer of Abgenix. "MBio is our first
collaboration directly with a genomics company."

"The initiation of this collaboration is an important step toward our goal of
filing an Investigational New Drug (IND) application in 1999 on a clinical
candidate," said Dr. John Maraganore, general manager of MBio. "This
collaboration also demonstrates that through the focused application of our
powerful genomics-driven target discovery efforts, MBio intends to deliver
promising therapeutic antibody candidates to the market," Maraganore added.

Abgenix and Millennium BioTherapeutics Form Collaboration

Millennium BioTherapeutics, a majority-owned subsidiary of Millennium
Pharmaceuticals, Inc., uses genomics technology and informatics to discover and
develop biotherapeutic (therapeutic proteins and antibodies, vaccines, gene
therapy and antisense) products. Millennium Pharmaceuticals, Inc. has granted
its commercialization rights for biotherapeutic products to MBio. MBio currently
has over 70 employees and a major corporate alliance with Eli Lilly and Company.

Millennium, a leading genomics-driven life sciences company, employs large-scale
genetics, genomics, high throughput screening and informatics in an integrated,
broad-based discovery platform to enable and accelerate the discovery and
development of new, proprietary therapeutic, diagnostic and life sciences
products and services addressing major market needs. Headquartered in Cambridge,
Mass. Millennium and its affiliates currently employ more than 550 people.

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Abgenix, a biopharmaceutical company, develops and intends to commercialize
antibody therapeutic products for the prevention and treatment of a variety of
disease conditions, including transplant-related diseases, inflammatory and
autoimmune disorders, and cancer. Abgenix has developed a proprietary technology
which it believes enables it to quickly generate high affinity, fully human
antibody product candidates to essentially any disease target appropriate for
antibody therapy. Besides Millennium, Abgenix has collaborative arrangements
with Genentech, Inc., Pfizer Inc., Schering-Plough Research Institute and Cell
Genesys, Inc. In addition, Abgenix has four proprietary antibody product
candidates that are under development internally, two of which are in human
clinical trials.

Statements made in this press release about Abgenix's product development
activities, clinical trials, product pipelines, corporate partnerships and
patent portfolio, other than statements of historical fact, are forward looking
statements and are subject to a number of uncertainties that could cause actual
results to differ materially from the statements made, including risks
associated with the success of clinical trials, research and product development
programs, the regulatory approval process, competitive products and the extent
and breadth of Abgenix's patent portfolio. Please see Abgenix's Form S-1 dated
April 3, 1998 and amendments thereto for information about risks associated with
clinical trials and product development programs and other risks, which may
affect Abgenix.

This press release contains forward-looking statements that involve a number of
risks and uncertainties for both Millennium Pharmaceuticals, Inc. and it's
majority-owned subsidiary, Millennium BioTherapeutics, Inc. Among the factors
that could cause actual results to differ materially from those indicated in
such forward looking statements include uncertainties relating to gene
identification, drug discovery and clinical development processes; changes in
relationships with strategic partners and dependence upon strategic partners for
the performance of critical activities under the collaborative agreements; the
impact of competitive products and technological changes; uncertainties relating
to patent protection; and uncertainties relating to the Company's ability to
obtain the substantial additional funds required for its progress. The factors
that could affect the performance of Millennium are more fully described in
filings by Millennium with the Securities and Exchange Commission including but
not limited to the factors set forth under the heading "Business -- Factors That
May Affect Results" in the Annual Report on Form 10-K of Millennium for the year
ended December 31, 1997 as filed on March 31, 1998.