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Immunomedics Reports First Results of Labetuzumab-SN-38 in Colorectal Cancer

Immunomedics Reports First Results of Labetuzumab-SN-38 in Colorectal Cancer

Results Presented as Late-Breaking Poster at 2013 Annual Meeting of the
American Association for Cancer Research

WASHINGTON, April 9, 2013 (GLOBE NEWSWIRE) -- Immunomedics, Inc.
(Nasdaq:IMMU), a biopharmaceutical company primarily focused on the
development of monoclonal antibody-based products for the targeted treatment
of cancer, autoimmune and other serious diseases, today announced that its
proprietary antibody-drug conjugate (ADC), labetuzumab-SN-38, appears to be
safe and reasonably well tolerated within a clinically effective dosage range
in patients with advanced colorectal cancer. Results from this Phase I study
were presented by Dr. Neil H. Segal from the Memorial Sloan Kettering Cancer
Center, New York, NY.

Labetuzumab-SN-38 is one of three agents from the Company's robust ADC program
that are in clinical development. Labetuzumab is a slowly-internalizing
antibody that recognizes the carcinoembryonic antigen (CEA; CEACAM5 or CD66e),
which is expressed in many solid cancers, including more than 80% of
colorectal cancer. In prior clinical trials, the antibody was shown to be safe
when administered unconjugated or bound to the radioisotope, iodine-131, for
radioimmunotherapy.

SN-38 is the active metabolite of irinotecan, which is a standard therapy for
patients with metastatic colorectal cancer, but has major gastrointestinal and
hematologic toxicity. By targeting SN-38 directly to CEA-expressing tumors,
delivery of SN-38 may be increased while mitigating systemic toxicity.
Preclinical studies have shown that the antibody-drug linkage was susceptible
to cleavage in serum, with 50% of SN-38 released in ~1.0 day, leading to a
locally enhanced concentration within the tumor site. In animal models of
human colorectal cancer, the ADC exhibited high anti-tumor activity.

The goal of this single-arm, dose-escalation study was to determine the
maximum-tolerated dose of labetuzumab-SN-38 in patients with metastatic
colorectal cancer. Patients who had previously been treated with at least one
prior irinotecan-containing regimen were enrolled to receive 2 doses of the
ADC separated by 14 days. In the absence of unacceptable toxicity or disease
progression, treatment continues for at least 24 weeks for a total of 12
cycles. Treatment may continue past 24 weeks if the patient reports a partial
response or stable disease, with no unacceptable toxicity.

At the time of reporting, 11 patients with a median of 5 prior therapies have
been treated at the 2, 4, 8, and 16 mg/kg dose levels. The average number of
doses given was 3.9, with 6 of 11 patients receiving 3 or more doses. Five
patients received 2 or more doses of 16 mg/kg, of which 1 has currently
received 18 doses and has a continuing partial response after 8 doses.

One dose-limiting toxicity was observed at 16 mg/kg. Otherwise, the ADC was
well tolerated. No human anti-humanized antibodies have been detected to date.
Analysis of serum samples showed the intact conjugate clears more quickly than
the antibody, consistent with SN-38 being gradually released from the ADC.

"These initial results are very encouraging," remarked Cynthia L. Sullivan,
President and Chief Executive Officer of Immunomedics. "What differentiates
our ADCs from other companies' products is the high ratio of drug to antibody,
which, in labetuzumab-SN-38, is 6. While dose-escalation is continuing with
this study, we are opening a new study with the same ADC in the same disease
setting, but with a more intensive and a higher dosing schedule," added Ms.
Sullivan.

About Immunomedics

Immunomedics is a New Jersey-based biopharmaceutical company primarily focused
on the development of monoclonal antibody-based products for the targeted
treatment of cancer, autoimmune and other serious diseases. We have developed
a number of advanced proprietary technologies that allow us to create
humanized antibodies that can be used either alone in unlabeled or "naked"
form, or conjugated with radioactive isotopes, chemotherapeutics, cytokines or
toxins, in each case to create highly targeted agents. Using these
technologies, we have built a pipeline of therapeutic product candidates that
utilize several different mechanisms of action. We also have a majority
ownership in IBC Pharmaceuticals, Inc., which is developing a novel
DOCK-AND-LOCK™ (DNL™) method with us for making fusion proteins and
multifunctional antibodies, and a new method of delivering imaging and
therapeutic agents selectively to disease, especially different solid cancers
(colorectal, lung, pancreas, etc.), by proprietary, antibody-based,
pretargeting methods. We believe that our portfolio of intellectual property,
which includes approximately 220 active patents in the United States and more
than 400 foreign patents, protects our product candidates and technologies.
For additional information on us, please visit our website at
www.immunomedics.com. The information on our website does not, however, form a
part of this press release.

This release, in addition to historical information, may contain
forward-looking statements made pursuant to the Private Securities Litigation
Reform Act of 1995. Such statements, including statements regarding clinical
trials, out-licensing arrangements (including the timing and amount of
contingent payments), forecasts of future operating results, potential
collaborations, and capital raising activities, 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 any cash payment that the Company might
receive in connection with a sublicense involving a third party and UCB, which
is not within the Company's control, new product development (including
clinical trials outcome and regulatory requirements/actions), our dependence
on our licensing partners for the further development of epratuzumab and
veltuzumab for non-cancer indications, competitive risks to marketed products
and availability of required financing and other sources of funds on
acceptable terms, if at all, as well as the risks discussed in the Company's
filings with the Securities and Exchange Commission. The Company is not under
any obligation, and the Company expressly disclaims any obligation, to update
or alter any forward-looking statements, whether as a result of new
information, future events or otherwise.

CONTACT: For More Information:
         Dr. Chau Cheng
         Senior Director, Investor Relations & Grant Management
         (973) 605-8200, extension 123
         ccheng@immunomedics.com