Nektar Presents Positive Preclinical Data for NKTR-214, a Novel Cancer Immunotherapy, At the 2013 American Society of Clinical

    Nektar Presents Positive Preclinical Data for NKTR-214, a Novel Cancer
   Immunotherapy, At the 2013 American Society of Clinical Oncology Annual

NKTR-214 Demonstrates Improved Efficacy and Better Tolerability in Aggressive
and Resistant Preclinical Melanoma Model

PR Newswire

SAN FRANCISCO, June 3, 2013

SAN FRANCISCO, June 3, 2013 /PRNewswire/ -- Nektar Therapeutics (NASDAQ:NKTR)
announced positive preclinical data for NKTR-214, an investigational cancer
immunotherapy which targets the IL-2 receptor complex and is being developed
as a potential treatment for multiple cancers. The results were presented
today at the 2013 ASCO Annual Meeting in Chicago. NKTR-214 targets the IL-2
receptor complex through selective receptor binding to the IL2R beta subtype.
Activation of the IL2R beta subtype promotes tumor killing by the body's own
immune system.

"The design of NKTR-214 provides dramatic efficacy in an aggressive and
resistant preclinical model of melanoma, despite dosing 10-fold less cytokine
at a significantly lower dosing frequency as compared to standard aldesleukin
dosing," said Stephen Doberstein, Ph.D., Senior Vice President and Chief
Scientific Officer of Nektar Therapeutics. "The ability to dial back the dose
intensity with NKTR-214 results in a potentially safer therapy while still
increasing efficacy. The reduced dosing frequency alsomakes it amenable to
combination with other immunotherapies such as immune checkpoint inhibitor

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. 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 is designed to
minimize the immunosuppressive effects that normally limit the efficacy of
standard aldesleukin. In the preclinical data presented at ASCO, NKTR-214
exhibits efficacy and tolerability that is superior to the clinically approved
cytokine aldesleukin (Proleukin®). NKTR-214 was as efficacious as aldesleukin,
even when NKTR-214 was dosed with 20-fold less total cytokine or dosed only
once every fourteen days. NKTR-214 is currently undergoing further
pre-clinical IND-enabling toxicological and efficacy studies.

NKTR-214 Preclinical Data Presentation

Abstract Title: "An engineered immunotherapy (NKTR-214) with altered
selectivity towards the IL-2 receptor: Efficacy and tolerability in a murine
tumor model", Charych et al.

     oAbstract Number: 3060
     oSession Title/Track: Developmental Therapies - Immunotherapy
     oDate: June 3, 2013, 8:00 a.m. — 11:45 a.m. Central Time
     oLocation: S Hall A2

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 oncology, pain 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 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. 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. In
anti-infectives, Amikacin Inhale is in Phase 3 studies conducted by Bayer
Healthcare as an adjunctive treatment for intubated and mechanically
ventilated patients with Gram-negative pneumonia.

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

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
early stage of drug development and may not be confirmed in subsequent
preclinical studies or in clinical trials, if any; (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 the potential
commencement of clinical studies for NKTR-214; (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) 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 (such
as NKTR-214) is therefore highly uncertain and unpredictable and one or more
research and development programs could fail; and (vi) certain other important
risks and uncertainties set forth in our Quarterly Report on Form 10-Q filed
with the Securities and Exchange Commission on May 9, 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:  
Karen Bauer                                               (415) 817-2549
Mike Huckman                                              (646) 500-7631

SOURCE Nektar Therapeutics

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