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First Peer-Reviewed Preclinical and Early Phase 1 Results for NKTR-118 (oral PEG-naloxol) to be Presented at Upcoming Pharmacology and Pain Management Meetings

Nektar's Proprietary NKTR-118 Being Studied For Its Potential to Treat Opioid-Induced Constipation

SAN CARLOS, Calif., July 26, 2007 /PRNewswire-FirstCall/ -- The first peer-reviewed preclinical and early Phase 1 clinical data for Nektar Therapeutics' proprietary product candidate, NKTR-118 (oral PEG-naloxol) are scheduled to be presented at two upcoming scientific meetings. NKTR-118 is an oral therapy being studied for its potential to treat patients suffering from opioid-induced constipation (OIC), a debilitating side effect of opioid analgesic therapy.

NKTR-118 is an oral drug that combines Nektar's advanced small molecule PEGylation technology platform with naloxol, a derivative of the opioid- antagonist drug naloxone. Nektar's PEGylation technology helps prevent oral NKTR-118 from crossing the blood brain barrier, an important potential advance for this and possibly many other small molecule therapies. This first Phase 1 study indicates that NKTR-118 may have the potential to mitigate the constipation side effect of opioid drugs without compromising their analgesic effects.

"As the clinical development of oral NKTR-118 moves forward, the results of these studies strengthen our understanding of this innovative molecule," said Dr. Hoyoung Huh, MD, PhD, Nektar's Chief Operating Officer and Head of the PEGylation Business Unit. "The utility and importance of many small molecule drugs may be potentiated if they can be selectively modulated from crossing the blood brain barrier. This is one of the major areas where Nektar's proprietary small molecule PEGylation technology may have a significant impact."

According to IMS, more than 200 million prescriptions were written for opioids in 2006 in the United States alone. Many studies indicate that a high percentage of patients on opioids are likely to experience significant constipation and other symptoms of opioid-induced bowel dysfunction.

    The data presentations scheduled are:

    -- Sept. 9 - 11, 2007, the  of Clinical Pharmacology

       Annual Meeting, The Palace Hotel, San Francisco, California.

       -- A poster presentation of Phase 1 clinical data evaluating single

          oral doses of NKTR-118 (oral PEG-naloxol) as a peripheral opioid

          antagonist (POA) in a double-blind, placebo-controlled study in

          healthy male subjects.

    -- September 27 - 30, 2007, the American Academy of Pain Management Annual

       Clinical Meeting, Red Rock Resort, Las Vegas, Nevada.

       -- A poster presentation of Phase 1 results of an investigation of

          NKTR-118 (oral PEG-naloxol) as a selective POA;

       -- A poster presentation of the preclinical pharmacology and

          pharmacokinetics of NKTR-118 (oral PEG-naloxol).

Nektar PEGylation Platform

Nektar PEGylation technology can enhance the properties of therapeutic agents by increasing drug circulation time in the bloodstream, decreasing immunogenicity and dosing frequency, increasing bioavailability and improving drug solubility and stability. It can also be used to modify pharmaceutical agents to preferentially target certain systems within the body. It is a technique in which non-toxic polyethylene glycol (PEG) polymers are attached to therapeutic agents, and it is applicable to most major drug classes, including proteins, peptides, antibody fragments, small molecules, and other drugs.

Nektar PEGylation technology is also used in eight additional approved partnered products in the U.S. or Europe today, including Roche's PEGASYS(R) for hepatitis C and Amgen's Neulasta(R) for neutropenia.

About Nektar

Nektar Therapeutics is a biopharmaceutical company that develops and enables differentiated therapeutics with its industry-leading PEGylation and pulmonary drug development technology platforms. Nektar PEGylation and pulmonary technology, expertise, manufacturing capabilities have enabled nine approved products for partners, which include the world's leading pharmaceutical and biotechnology companies. Nektar also develops its own products by applying its PEGylation and pulmonary technology platforms to existing medicines with the objective to enhance performance, such as improving efficacy, safety and compliance.

This press release contains forward-looking statements regarding the potential of the company's PEGylation technology platform and NKTR-118. These forward-looking statements involve important risks and uncertainties, including but not limited to: (i) preclinical testing and clinical trials for NKTR-118 are long, expensive and uncertain processes, (ii) because the NKTR- 118 product development programs are in the early phases of clinical development, the risk of failure is high and can occur at any stage of development, (iii) the company may fail to obtain regulatory approval of NKTR- 118, (iv) potential competition from approved drugs or drugs under development that may be safe and effective for the same indication as that targeted by NKTR-118, and (v) the company's patent applications for NKTR-118 may fail to issue; patents that have issued may not be enforceable; or unanticipated intellectual property licenses from third parties may be required in the future. Other important risks and uncertainties are detailed in the company's reports and other filings with the SEC; including its most recent Annual Report on Form 10-K and Quarterly Report on Form 10-Q. Actual results could differ materially from the forward-looking statements contained in this press release. The company undertakes no obligation to update forward-looking statements, whether as a result of new information, future events, or otherwise. No information regarding or presented at the scientific meetings referred to above (or contained at the Internet links provided herein) is intended to be incorporated by reference in this press release.

Posted: July 2007