Celldex Therapeutics’ CDX-301 Safely Mobilizes Hematopoietic Cells in Phase 1 Study; Future Development Planned

  Celldex Therapeutics’ CDX-301 Safely Mobilizes Hematopoietic Cells in Phase
  1 Study; Future Development Planned

                      --Results presented at ASH 2012--

Business Wire

NEEDHAM, Mass. -- December 11, 2012

Celldex Therapeutics, Inc. (NASDAQ: CLDX) announced positive results from a
Phase 1 multi-dose study of CDX-301 (FMS-like tyrosine kinase-3 ligand)
demonstrating that CDX-301 was well-tolerated and can safely and effectively
mobilize hematopoietic cell populations in healthy volunteers. The data
support future development of CDX-301 in a number of indications, including
hematopoietic stem cell transplant and cancer immunotherapy. Results were
presented in a poster entitled “A Phase 1 Trial of the Hematopoietic Growth
Factor CDX-301 (rhuFlt3L) in Healthy Volunteers” on Monday, December 10, 2012
at 6:00 pm ET at the American Society of Hematology 54th Annual Meeting and
Exposition. The lead author was Niroshana Anandasabapathy, MD, PhD, Laboratory
of Cellular Physiology and Immunology, The Rockefeller University, New York,
NY.

“The data presented today confirm previous studies and support continued
development of CDX-301, both alone and in combination with other Celldex
assets across a broad range of indications,” said Thomas Davis, MD, Senior
Vice President and Chief Medical Officer. “In particular, we believe CDX-301
holds significant potential for use in hematopoietic stem cell transplant,
where it has demonstrated improvement of blood cell reconstitution in
preclinical in vivo models. Data from the Phase 1 study will enable us to
define an appropriate dosing regimen for this indication and future
indications. We intend to work with collaborators, including academic
institutions and government agencies, to conduct future studies.”

Study Results:

30 healthy volunteers were enrolled across seven cohorts. The first five
cohorts assessed escalating doses of CDX-301 (from 1 ug/kg to 75 ug/kg) as a
five-day regimen, while the final two cohorts assessed CDX-301 (at 25 ug/kg)
as seven- and 10-day regimens. All volunteers completed dosing and safety
follow-up. Short-term dosing of five days resulted in significant mobilization
of dendritic and stem cells, with the highest levels of mobilization achieved
at the maximum dose. Ten-day dosing significantly enhanced the circulation of
white blood cells and monocytes compared to the five-day regimen. Analysis on
the expansion of stem cells, dendritic cells and other cell populations are
still being conducted and will be presented at a future medical meeting.
CDX-301 was generally well-tolerated. Transient Grade 1 lymphadenopathy was
observed in five volunteers and Grade 1 diarrhea was observed in two
volunteers. One possible dose-limiting toxicity (DLT) was observed in a
volunteer with a remote history of community acquired pneumonia (CAP) who
developed CAP on study day 12. The volunteer responded rapidly to antibiotics
and fully recovered. No additional infections or DLTs were observed in the
study. No anti-CDX-301 antibodies were detected in any volunteers through the
end of study follow-up.

About CDX-301

CDX-301 or Flt3L is a potent hematopoietic cytokine that stimulates the
expansion and differentiation of hematopoietic progenitor and stem cells.
Flt3L has demonstrated a unique capacity to increase the number of circulating
dendritic cells in both laboratory and clinical studies. In addition, Flt3L
has shown impressive results in models of cancer, infectious diseases and
inflammatory/autoimmune diseases. Celldex believes this ligand may hold
significant opportunity for synergistic development in combination with other
proprietary molecules in the Company’s portfolio.

About Celldex Therapeutics, Inc.

Celldex Therapeutics is the first antibody-based combination immunotherapy
company. Celldex has a pipeline of drug candidates in development for the
treatment of cancer and other difficult-to-treat diseases based on its
antibody focused Precision Targeted Immunotherapy (PTI) Platform. The PTI
Platform is a complementary portfolio of monoclonal antibodies,
antibody-targeted vaccines and immunomodulators used in optimal combinations
to create novel disease-specific drug candidates. For more information, please
visit www.celldextherapeutics.com.

Safe Harbor Statement Under the Private Securities Litigation Reform Act of
1995: This release contains “forward-looking statements” made pursuant to the
safe harbor provisions of the Private Securities Litigation Reform Act of
1995, including those related to the Company’s strategic focus and the future
development and commercialization of CDX-011 or any of our other drug
candidates, including rindopepimut (CDX-110), CDX-1135 (formerly TP10),
CDX-1401, CDX-1127, CDX-301, Belinostat and any future action we or the FDA
(or any other regulator) might take with respect to regulatory approvals.
Forward-looking statements reflect management's current knowledge,
assumptions, judgment and expectations regarding future performance or events.
Although management believes that the expectations reflected in such
statements are reasonable, they give no assurance that such expectations will
prove to be correct and you should be aware that actual results could differ
materially from those contained in the forward-looking statements.
Forward-looking statements are subject to a number of risks and uncertainties,
including, but not limited to, future actions that the FDA and other
regulators might take or not take with respect to CDX-011 or any drug
candidate, the market for CDX-011 or any other drug candidate or assay, future
clinical testing which will be necessary before FDA approval could be sought,
our ability to obtain additional capital on acceptable terms, or at all,
including the additional capital which will be necessary to complete the
clinical trials that we initiated in 2012 and plan to initiate in 2013; our
ability to adapt APC Targeting Technology^TM to develop new, safe and
effective vaccines against oncology and infectious disease indications; our
ability to successfully complete product research and further development of
our programs; the uncertainties inherent in clinical testing; our limited
experience in bringing programs through Phase 3 clinical trials; our ability
to manage research and development efforts for multiple products at varying
stages of development; the timing, cost and uncertainty of obtaining
regulatory approvals; the failure of the market for the Company's programs to
continue to develop; our limited cash reserves and our ability to obtain
additional capital on acceptable terms, or at all; our ability to protect the
Company’s intellectual property; the loss of any executive officers or key
personnel or consultants; competition; changes in the regulatory landscape or
the imposition of regulations that affect the Company’s products; and other
risks detailed from time to time in the Company's filings with the Securities
and Exchange Commission, including the Company's Form 10-K for the fiscal year
endedDecember 31, 2011, anditsForms 10-Q and 8-K.

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this cautionary notice. You are cautioned not to place undue reliance on any
forward-looking statements, which speak only as of the date of this release.
We have no obligation, and expressly disclaim any obligation, to update,
revise or correct any of the forward-looking statements, whether as a result
of new information, future events or otherwise.

Contact:

Celldex Therapeutics, Inc.
Sarah Cavanaugh, 781-433-3161
Vice President of IR & Corp Comm
scavanaugh@celldextherapeutics.com
or
For Media:
BMC Communications
Brad Miles, 646-513-3125
bmiles@bmccommunications.com