NKTR-105 Demonstrates Superior Antitumor Activity and Improved Pharmacokinetics Over Docetaxel in Preclinical Studies Presented at AACR

DENVER and SAN CARLOS, Calif., April 22, 2009 /PRNewswire-FirstCall/ -- Nektar Therapeutics presented data today at the American Association for Cancer Research (AACR) 100th Annual Meeting demonstrating that NKTR-105, a novel PEGylated form of docetaxel, has superior antitumor activity, as well as greater and sustained exposure in plasma and tumor tissue, over docetaxel in preclinical models.

In a comparative study of NKTR-105 and docetaxel, NKTR-105 treatment significantly delayed tumor growth as compared to docetaxel (122% v. 48%), which was associated with greater and sustained tumor exposure to docetaxel after NKTR-105 administration. Treatment with NKTR-105 increased docetaxel concentrations in tumors (0.4 to 4-fold higher) and resulted in an improved time-concentration profile (2-fold greater) as compared to docetaxel in a non-small cell lung (H460) mouse xenograft model.

"The encouraging antitumor activity and unique pharmacokinetic profile of NKTR-105 in these data support our ongoing Phase 1 study in patients with refractory solid cancers," said Randall Moreadith, M.D., Ph.D. Senior Vice President, Drug Development and Chief Development Officer. "We believe NKTR-105 has the potential to offer improved efficacy as well as improved safety and tolerability due to its prolonged half-life and increased uptake by tumor tissue relative to docetaxel. We are excited about the drug's potential to significantly expand therapeutic options for oncologists and patients."

In previous preclinical studies, NKTR-105 demonstrated superior antitumor activity with no neutropenia in multiple tumor models, indicating that NKTR-105 may enable sustained therapeutic levels of docetaxel without the myelosuppression that is a dose-limiting toxicity for this widely-used cancer therapy.

NKTR-105 is currently being evaluated in a Phase 1 clinical trial in cancer patients. The Phase 1 study will assess the safety, pharmacokinetics and antitumor activity of NKTR-105 in approximately 30 patients with refractory solid tumors who have failed all prior available therapies. In the current trial of NKTR-105, the compound has required no pre-treatment with corticosteroids and shown no evidence of neutropenia in patients to date.

NKTR-105 is a novel form of docetaxel that was developed using Nektar's advanced polymer technology platform. The compound belongs to the taxoid family and acts by disrupting the microtubular network in cells. It is being developed as an anti-neoplastic agent, and is the company's second oncology program in clinical development.

Docetaxel is a versatile chemotherapy agent currently approved by the FDA for use in breast, non-small cell lung, prostate, gastric, and head and neck cancers. Oncolytics such as docetaxel typically have sub-optimal half-lives which can limit their therapeutic efficacy, or have a safety and tolerability profile that limits their use. Nektar's advanced polymer conjugate technology platform has the potential to be used to optimize the bioactivity of these small molecule compounds and increase the sustained exposure of active drug to tumor cells in the body. Annual sales of docetaxel are in excess of $2 billion worldwide.

The poster presentation from today's session entitled "Novel Agents 4" can be found on Nektar's website at www.nektar.com/product_pipeline/oncology_nktr-105.html.

Nektar Therapeutics is a biopharmaceutical company developing novel therapeutics based on its PEGylation and advanced polymer conjugation technology platforms. Nektar's technology and drug development expertise have enabled nine approved products for partners, which include leading biopharmaceutical companies. Nektar is also developing a robust pipeline of its own potentially high-value therapeutics that address unmet medical needs by leveraging and expanding its technology platforms to improve and enable molecules.

Nektar is headquartered in San Carlos, California, with additional R&D operations in Huntsville, Alabama and Hyderabad, India.

This press release contains forward-looking statements that reflect the company's current views regarding the potential of the Company's technology platforms and the potential of NKTR-105. These forward-looking statements involve risks and uncertainties, including but not limited to: (i) NKTR-105 is in the early stages of clinical development and the risk of failure is high and can unexpectedly occur at any time; (ii) the timing or success of the commencement or end of clinical trials may be delayed or unsuccessful due to slower than anticipated patient enrollment, drug manufacturing challenges, changing standards of care, clinical trial design, clinical outcomes, or delay or failure in obtaining regulatory approval in one or more important markets; (iii) clinical trials are long, expensive and uncertain processes and the risk of failure of any product that is in clinical development and prior to regulatory approval remains high and can occur at any stage due to efficacy, safety or other factors; (iv) the company's patent applications for its proprietary or partner product candidates may not issue, patents that have issued may not be enforceable, or intellectual property licenses from third parties may be required in the future; and (v) the outcome of any existing or future intellectual property or other litigation related to Nektar's proprietary product candidates. Other important risks and uncertainties are detailed in the company's reports and other filings with the Securities and Exchange Commission, 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. For more information on Nektar Therapeutics, please visit www.nektar.com.

    Contact:
    Jennifer Ruddock, 650-631-4954
    Nektar Therapeutics

CONTACT: Jennifer Ruddock of Nektar Therapeutics, +1-650-631-4954

Web site: http://www.nektar.com/

Ticker Symbol: (NASDAQ-NMS:NKTR)

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Posted: April 2009

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