Nektar and collaborators announce publication in Blood Advances of preclinical data demonstrating that NKTR-255, a novel polymer-conjugated human IL-15, enhances the efficacy of CD19-targeted CAR-T cell immunotherapy


— CD8 induced by IL-15 conjugated to a polymer (NKTR-255)+ Proliferation of T lymphocytes and natural killer cells live

— NKTR-255 Enhanced the Efficacy of Human CD19 CAR-T Cells in a Xenogeneic Lymphoma Model —

SAN FRANCISCO, November 9, 2022 /PRNewswire/ — Nektar Therapeutics (Nasdaq: NKTR) today announced the release of preclinical data in Blood advancesthe open access journal of the American Society of Hematology, highlighting the effects of NKTR-255, a novel polymer-conjugated human IL-15, on the efficacy of human CD19 CAR-T cells in a lymphoma model xenogeneic and on CD8+ Proliferation of effector T cells (T cells) and natural killer (NK) cells in non-human primates.

(PRNewsfoto/Nektar Therapeutics)

“The results published today reinforce the fundamental rationale for the clinical development program we are pursuing for NKTR-255-enhancing CAR-T cell therapies,” said Jonathan Zalevsky, Ph.D., Director of Research and Development at Nektar. “We look forward to advancing our research in combination with cell therapies and are excited to initiate our Phase 2/3 clinical trial of NKTR-255 following approved CAR-T cell therapies in patients with diffuse lymphoma at relapsed or refractory large B cells. “

The data in this publication demonstrates that NKTR-255 not only improved live proliferation and accumulation of T and NK cells in non-human primates, but also demonstrated improvement live antitumor efficacy of human CD19 CAR-T in immunodeficient mice with lymphoma.

“In contrast to mice treated with CAR-T alone, those that received CAR-T and NKTR-255 had significantly higher blood and marrow CAR-T counts that were maintained after tumor clearance, without evidence of persistent proliferation or ongoing activation/depletion assessed by Ki-67 and co-expression of inhibitory receptors,” said Dr. Cameron turtle, lead author of the publication and CLEARbridge Chair in Cancer Immunotherapy at Sydney Medical School. “These data support ongoing clinical research on combined CAR-T and NKTR-255 for B-cell malignancies.”

The main conclusions are summarized below:

  • Serum IL-15 concentration is independently associated with longer persistence of CD19 CAR-T in humans

  • NKTR-255 promotes CD8+ Accumulation of effector and memory T and NK cells in non-human primates

  • NKTR-255 enhances proliferation and survival of human CD19 CAR-T at low target cell abundance

  • NKTR-255 Enhances Human CD19 CAR-T Accumulation and Efficacy in Immunodeficient Lymphoma-Bearing Mice

The full citation for this article can be viewed at:

About the NKTR-255

NKTR-255 is a biologic that targets the IL-15 pathway to activate the body’s innate and adaptive immunity. Through optimal engagement of the IL-15 receptor complex, NKTR-255 is designed to enhance functional NK cell populations and the formation of long-term immunological memory, which may lead to a sustained anti-tumor immune response and sustainable.

Preclinical findings suggest that NKTR-255 has the potential to synergistically combine with antibody-dependent cellular cytotoxicity molecules as well as enhance CAR-T therapies.

There are two ongoing investigator sponsored trials evaluating NKTR-255 after treatment with CAR-T cell therapy. Fred Hutchinson Cancer Center is conducting a Phase 1 study evaluating NKTR-255 in combination with CD19 CAR-T cell therapy in patients with relapsed or refractory large B-cell lymphoma (NCT05359211), and Stanford University is conducting a Phase 1 study evaluating NKTR-255 in combination with CD19/22 CAR-T cell therapy in patients with relapsed or refractory B-cell acute lymphoblastic leukemia (NCT03233854).

Nektar is also designing a Nektar-sponsored Phase 2/3 study combining NKTR-255 with approved CAR-T cell therapies in diffuse large B-cell lymphoma, which it aims to initiate in Q1 2023.

About Nektar Therapeutics

Nektar Therapeutics is a biopharmaceutical company with a strong wholly-owned R&D portfolio of investigational drugs in oncology and immunology, as well as a pipeline of approved drug partners. Nektar is headquartered in San Francisco, Californiawith additional operations in Huntsville, Alabama. Additional information about the Company and its drug development programs and capabilities is available online at

Caution Regarding Forward-Looking Statements

This press release contains forward-looking statements that can be identified by words such as: “will”, “may”, “launch”, “potential”, “demonstrate”, “initiate” and similar references to future periods. Examples of forward-looking statements include, but are not limited to, statements we make regarding the therapeutic potential and future development plans of NKTR-255 and our other drug candidates in research programs, the outlook and plans of our collaborations with other companies, the timing of the initiation of clinical studies and data readouts for our drug candidates, and our expectations (including our expected costs and savings) following our restructuring, reorganization and downsizing, and our expected working capital and our cash trail. Forward-looking statements are neither historical facts nor guarantees of future performance. Instead, they are based solely on our current beliefs, expectations and assumptions about the future of our business, our future plans and strategies, expected 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 beyond our control. Our actual results may differ materially from those indicated in the forward-looking statements. Accordingly, you should not rely on any such forward-looking statements. Important factors that could cause our actual results to differ materially from those set forth in the forward-looking statements include, among others: (i) our statements regarding the therapeutic potential of NKTR-255 and our other drug candidates are based on results preclinical and clinical data and observations and are subject to change as research and development continues; (ii) NKTR-255 and our other drug candidates are investigational agents and the continued research and development of these drug candidates is subject to substantial risks, including negative safety and efficacy in ongoing clinical studies (despite positive results from previous preclinical and clinical studies); (iii) NKTR-255 and our other drug candidates are in various stages of clinical development and the risk of failure is high and may occur unexpectedly at any stage prior to regulatory approval; (iv) the timing of the start or end of clinical trials and the availability of clinical data may be delayed or unsuccessful due to challenges caused by the COVID-19 pandemic, regulatory delays, slower than expected patient recruitment , manufacturing challenges, changing standards of care, changing regulatory requirements, clinical trial design, clinical results, competitive factors, or the delay or failure to obtain final regulatory approval in one or more significant markets; (v) we may not realize the expected cost savings we expect from the restructuring and reorganization, (vi) patents may not issue from our patent applications for our drug candidates, patents that issued may not be enforceable, or additional intellectual property licenses from third parties may be required; and (vii) certain other important risks and uncertainties set forth in our Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on November 4, 2022. Any forward-looking statements we make in this press release are based solely on information we currently have available and are only valid as of the date they are 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.


Viviane Wu by Nektar Therapeutics



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