October 23, 2008

Positive Preclinical Data Demonstrating Anti-Tumor Activity of NKTR-105 (PEG-Docetaxel) Presented at 20th EORTC-NCI-AACR Conference

GENEVA and SAN CARLOS, Calif., Oct. 23 /PRNewswire-FirstCall/ -- Nektar Therapeutics announced today that positive preclinical data for NKTR-105 (PEG-docetaxel) was presented at the 2008 EORTC-NCI-AACR (European Organization for Research and Treatment of Cancer-National Cancer Institute-American Association for Cancer Research) Symposium on Molecular Targets and Cancer Therapeutics being held in Geneva, Switzerland. NKTR-105 is the second oncology development program derived from Nektar's innovative small molecule PEGylation technology platform.

"These data highlight the exciting potential of NKTR-105 to treat multiple solid tumor types," said Randall Moreadith, M.D., Ph.D., Nektar Senior Vice President of Drug Development and Chief Development Officer. "The superior anti-tumor activity of NKTR-105 in preclinical tumor models as compared to docetaxel underscores the value of utilizing our proprietary PEGylation platform with oncolytics. As we have seen with the data for NKTR-102, PEG-irinotecan, which is advancing in Phase 2 clinical development, our technology platform enables a substantially improved pharmacokinetic profile that potentially enhances therapeutic efficacy."

The preclinical data presented for NKTR-105 shows significantly greater anti-tumor activity as compared to docetaxel in colorectal (LoVo and LS174T) and non-small cell lung (H460) mouse xenograft models of human tumors. Partial regressions were observed in two of the cell lines (LoVo and LS174T) for NKTR-105, while no regressions were observed for docetaxel. At maximum tolerated doses, the percent of tumor growth delay for NKTR-105 was 2.5-, 2.0-, and 1.6-fold greater than docetaxel in H460, LoVo, and LS174T xenograft models, respectively.

Nektar plans to file an Investigational New Drug Application (IND) for NKTR-105 by end of 2008 to initiate a Phase 1 clinical study.

Data Presentation for NKTR-105

The poster presentation from today's session entitled 'Tubulin-interacting agents' can be found on Nektar's website at http://www.nektar.com/wt/page/NKTR_105

2008 EORTC-NCI-AACR Symposium - Poster # 448, "NKTR-105, A Novel PEGylated Docetaxel, Demonstrates Superior Anti-Tumor Activity Versus Docetaxel in Human Non-Small Cell Lung and Colon Mouse Xenograft Models"

About NKTR-105

NKTR-105 is a novel PEGylated conjugate of docetaxel, an anti-neoplastic agent belonging to the taxoid family that acts by disrupting the microtubular network in cells. Docetaxel is a major chemotherapy agent approved for use in five different cancer indications: breast, non-small cell lung, prostate, gastric and head and neck. Annual sales of docetaxel count for more than 20 percent of the global market for the top five branded chemotherapy agents.

Using Nektar's small molecule PEGylation technology, NKTR-105 was created to improve the time-concentration profile and anti-tumor activity of docetaxel. The drug candidate will enter Phase 1 clinical development in early 2009.

Nektar PEGylation technology can enhance the properties of small and large molecules by increasing drug circulation time, improving pharmacokinetics, decreasing immunogenicity and dosing frequency, increasing bioavailability and improving drug solubility and stability. Nektar PEGylation technology has enabled all of the PEGylated products approved over the last ten years, which include eight approved partnered products, including UCB's Cimzia(R), Roche's PEGASYS(R) for hepatitis C and Amgen's Neulasta(R) for neutropenia.

About Nektar

Nektar Therapeutics is a biopharmaceutical company developing novel therapeutics based on its unique and proprietary PEGylation and advanced polymer conjugate chemistry technology platforms. Nektar's technologies and drug development expertise have enabled eight approved products for partners, which include leading biopharmaceutical companies. Nektar has a robust pipeline of high-value therapeutics in development designed to address significant unmet medical needs.

This press release contains forward-looking statements that reflect the company's current views regarding the potential, progress, and clinical plans for the company's proprietary and partnered product pipeline, and the value and potential of the company's technology platforms. These forward-looking statements involve risks and uncertainties, including but not limited to: (i) the company's proprietary product candidates and those of its partners are in various stages of clinical development and the risk of failure is high and can occur at any stage prior to regulatory approval; (ii) the timing or success of the commencement or end of clinical trials and commercial launch of partnered products 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 the company'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. 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 http://www.nektar.com/

    Stephan Herrera, 415-488-7699    [email protected]     Jennifer Ruddock, 650-631-4954    [email protected]  

Nektar Therapeutics

CONTACT: Stephan Herrera, +1-415-488-7699, [email protected], orJennifer Ruddock, +1-650-631-4954, [email protected], both of NektarTherapeutics

Web site: http://www.nektar.com/http://www.nektar.com/wt/page/NKTR_105