Positive Preclinical Data for NKTR-214, an Investigational Cancer Immunotherapy Targeting the IL-2 Receptor Complex, Presented

      Positive Preclinical Data for NKTR-214, an Investigational Cancer
 Immunotherapy Targeting the IL-2 Receptor Complex, Presented at AACR Annual
                                 Meeting 2013

NKTR-214 Demonstrates Improved Efficacy in Resistant Preclinical Melanoma
Model Through Preferential Activation of Tumor Killing Immune Cell Subtype

PR Newswire

SAN FRANCISCO, April 7, 2013

SAN FRANCISCO, April 7, 2013 /PRNewswire/ -- Nektar Therapeutics (Nasdaq:
NKTR) today presented positive preclinical data for NKTR-214, a novel cancer
immunotherapy which targets the IL-2 receptor complex, at the 2013 American
Association for Cancer Research (AACR) Annual Meeting. NKTR-214 is a new
immunocytokine that is being developed as a potential treatment for multiple
cancers. NKTR-214 targets the IL-2 receptor complex through selective
receptor binding to the IL2Rβ subtype. Activation of the IL2Rβ subtype
promotes tumor killing by the body's own immune system.

"We are extremely encouraged by the dramatic efficacy observed with NKTR-214
treatment in an aggressive and resistant preclinical model of melanoma," said
Stephen Doberstein, Ph.D., Senior Vice President and Chief Scientific Officer
of Nektar Therapeutics. "NKTR-214 is specifically designed to harness the
potent immunostimulatory effects of the IL-2 receptor complex while minimizing
the immunosuppressive effects that have greatly limited the efficacy of the
native IL-2 protein. Importantly, NKTR-214 represents the first application
of our technology platform to target a receptor subtype in the tumor
microenvironment while avoiding the unwanted effects from off-target receptor
binding. NKTR-214 also has improved pharmacokinetics and enhanced tumor
penetration which allow for a ten-fold reduction in overall dosing. We are
excited about the potential of NKTR-214 to emerge as a powerful new
immunotherapy in the fight against cancer."

NKTR-214 is a novel immunocytokine therapy that is engineered using Nektar's
polymer conjugate technology to selectively target the beneficial IL-2
receptor complex. In the preclinical data presented at AACR, NKTR-214
exhibits differentiated IL-2 receptor binding which results in significantly
altered immune cell populations in the tumor microenvironment compared to the
clinically validated IL-2 protein therapy, aldesleukin. Specifically,
NKTR-214 maintains high affinity for the IL-2 receptor subunit beta, which
activates tumor-killing T cells within the tumor microenvironment. At the
same time, NKTR-214 exhibits up to 100-fold reduced affinity to the IL-2
receptor subunit alpha-beta, which activates immuno-suppressive regulatory
T-cells. In a well-validated animal model of melanoma, NKTR-214 demonstrated
significantly improved dosing, at once every 9 days as compared to twice a day
dosing with aldesleukin.

The data was presented today at the AACR Annual Meeting 2013 in Poster
Session, Immunology 2, (Abstract #482): Charych, et al., "Tipping the balance
in the tumor microenvironment: An engineered cytokine (NKTR-214) with altered
IL-2 receptor binding selectivity and improved efficacy in a mouse melanoma

About Nektar
Nektar Therapeutics is a biopharmaceutical company developing novel
therapeutics based on its PEGylation and advanced polymer conjugation
technology platforms. Nektar has a robust R&D pipeline of potentially
high-value therapeutics in pain, oncology and other therapeutic areas. In the
area of pain, Nektar has an exclusive worldwide license agreement with
AstraZeneca for naloxegol (NKTR-118), an investigational drug candidate, which
has completed Phase 3 clinical development as a once- daily, oral tablet for
the treatment of opioid-induced constipation. This agreement also includes
NKTR-119, an earlier stage development program that is a co-formulation of
naloxegol and an opioid. In the proprietary pipeline, NKTR-181, a novel
mu-opioid analgesic candidate for chronic pain conditions, is in Phase 2
development in osteoarthritis patients with chronic knee pain. NKTR-192, a
novel mu-opioid analgesic in development to treat acute pain is in Phase 1
clinical development. In oncology, etirinotecan pegol (NKTR-102) is being
evaluated in a Phase 3 clinical study (the BEACON study) for the treatment of
metastatic breast cancer and is also in Phase 2 studies for the treatment of
ovarian and colorectal cancers.

Nektar's technology has enabled eight approved products in the U.S. or Europe
through partnerships with leading biopharmaceutical companies, including UCB's
Cimzia^® for Crohn's disease and rheumatoid arthritis, Roche's PEGASYS^® for
hepatitis C and Amgen's Neulasta^® for neutropenia. Additional
development-stage products that leverage Nektar's proprietary technology
platform include Baxter's BAX 855, a long-acting PEGylated rFVIII program,
which is in Phase 3 clinical development.

Nektar is headquartered in San Francisco, California, with additional
operations in Huntsville, Alabama and Hyderabad, India. Further information
about the company and its drug development programs and capabilities may be
found online at http://www.nektar.com.

Cautionary Note Regarding Forward-Looking Statements
This press release contains "forward-looking statements" within the meaning of
the Private Securities Litigation Reform Act of 1995. Forward-looking
statements can be identified by words such as: "anticipate," "intend," "plan,"
"expect," "believe," "should," "may," "will" and similar references to future
periods. Examples of forward-looking statements include, among others,
statements we make regarding the therapeutic potential of NKTR-214 and the
value and potential of our technology and drug candidates in our research and
development pipeline. Forward-looking statements are neither historical facts
nor assurances of future performance. Instead, they are based only on our
current beliefs, expectations and assumptions regarding the future of our
business, future plans and strategies, anticipated events and trends, the
economy and other future conditions. Because forward-looking statements relate
to the future, they are subject to inherent uncertainties, risks and changes
in circumstances that are difficult to predict and many of which are outside
of our control. Our actual results may differ materially from those indicated
in the forward-looking statements. Therefore, you should not rely on any of
these forward-looking statements. Important factors that could cause our
actual results to differ materially from those indicated in the
forward-looking statements include, among others, (i) positive preclinical
efficacy findings, such as those for NKTR-214 reported in this press release,
are subject to inherent scientific and medical uncertainties typical for this
stage of drug development and may not be confirmed in subsequent preclinical
studies or in clinical trials; (ii) NKTR-214 is in early stage research and
there are a number of hurdles, including the successful completion of
preclinical toxicology studies, prior to NKTR-214 being ready to enter into
clinical development; (iii) our drug candidates and those of our collaboration
partners are in various stages of clinical development and the risk of failure
is high and can unexpectedly occur at any stage prior to regulatory approval
for numerous reasons including safety and efficacy findings even after
positive findings in previous preclinical and clinical studies; (iv) the
timing of the commencement or end of clinical trials and the commercial launch
of our drug candidates may be delayed or unsuccessful due to regulatory
delays, slower than anticipated patient enrollment, manufacturing challenges,
changing standards of care, evolving regulatory requirements, clinical trial
design, clinical outcomes, competitive factors, or delay or failure in
ultimately obtaining regulatory approval in one or more important markets; (v)
acceptance, review and approval decisions for new drug applications by health
authorities is an uncertain and evolving process and health authorities retain
significant discretion at all stages of the regulatory review and approval
decision process; (vi) scientific discovery of new medical breakthroughs is an
inherently uncertain process and the future success of the application of our
technology platform to potential new drug candidates is therefore highly
uncertain and unpredictable and one or more research and development programs
could fail; and (vii) certain other important risks and uncertainties set
forth in our Annual Report on Form 10-K filed with the Securities and Exchange
Commission on March 1, 2013. Any forward-looking statement made by us in this
press release is based only on information currently available to us and
speaks only as of the date on which it is made. We undertake no obligation to
update any forward-looking statement, whether written or oral, that may be
made from time to time, whether as a result of new information, future
developments or otherwise.

Nektar Investor Inquiries:
Jennifer Ruddock/Nektar Therapeutics       (415) 482-5585
Susan Noonan/SA Noonan Communications, LLC (212) 966-3650
Nektar Media Inquiries:
Karin Bauer/MSL                            (415) 817-2524
Mike Huckman /MSL                          (646) 500-7631

SOURCE Nektar Therapeutics

Website: http://www.nektar.com
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