Abstract 3137: A novel expansion method for functional natural killer cells and its clinical application
Authors: Ishikawa Takeshi , Sakamoto Naoyuki , Okayama Tetsuya , Oka Kaname , Kokura Satoshi , Ideno Mitsuko , Kato Akiko , Enoki Tatsuji , Kitagawa Masanari , Mineno Junichi , Yasuda Tomoyo , Doi Toshifumi , Naito Yuji , Itoh Yoshito , Yoshikawa Toshikazu 
Published: August 2015

Background: Natural killer (NK) cell-based adoptive immunotherapy is a promising approach for the treatment of cancer. But, it is difficult to generate the sufficient scale and purity of NK cells, and reliable methods to produce large number of functional NK cells have not been established yet. We have developed novel clinical-grade NK cells expansion method to produce the high purity, large scale and functional NK cells using a combination of recombinant human fibronectin fragment (RetroNectin®) -induced T-cells (RN-T cells), OK-432 and IL-2. We subsequently conducted a Phase 1 clinical study to evaluate the safety and efficacy of this NK cell therapy. In this paper, we address the characteristics of the NK cells elicited by this method and the results of immune monitoring in the clinical trial.

Methods: To confirm the significance of RN-T cells as stimulator, we compared the stimulation effects on NK cells between RN-T cells and aCD3-T cells, which stimulated by anti-CD3 mAb only. Next, we analyzed expanded NK cells from PBMCs obtained from 31 cancer patients to verify the efficacy of this method. In the Phase 1 trial, patients with unresectable digestive cancer were enrolled. They received weekly intravenous administration of autologous NK cells elicited by the novel method three times to assess the safety of the number of adoptive cells at 0.5 × 109(cohort1), 1 × 109(cohort 2) and 2 × 109 cells (cohort 3) per dose. The phenotype and cytotoxicity of expanded NK cells were analyzed. For immune monitoring, cytotoxicity of PBMCs and whole blood cytokine levels were examined following NK cell infusion.

Results: The stimulation by RN-T cells could induce preferable NK cell proliferation rather than the one by aCD3-T. As results of 31 cancer patients, 688±76-fold expansion was achieved in this system with PBMCs, and the NK cell populations were highly purified (84.7±3.6%) and highly expressed functional markers such as NKG2D (97.3±0.6%) and CD16 (96.8±0.7%). In the Phase 1 clinical trial, no NK cell infusion related severe or unexpected toxicities were observed. The response rate and the disease control rate in 10 per protocol patients were 0% and 50.0%, respectively. Although no clinical responses were observed, the cytotoxicity of PBMCs against K-562 targets increased in most patients (80%). The average of cytotoxic activity of PBMCs increased more than two times after the NK cell infusion.

Conclusion:

Although no patients receiving the NK cell therapy alone experienced a clinical response, adoptive immunotherapy of the NK cells elicited by the novel method is expected to exert considerable ADCC activity in vivo because of their high expression of CD16. Now, we are conducting clinical trial in which we explore the combination of this novel NK therapy with IgG1 antibodies such as trastuzumab and cetuximab. We also address the ongoing clinical trial in this paper.

Citation Format: Takeshi Ishikawa, Naoyuki Sakamoto, Tetsuya Okayama, Kaname Oka, Satoshi Kokura, Mitsuko Ideno, Akiko Kato, Tatsuji Enoki, Masanari Kitagawa, Junichi Mineno, Tomoyo Yasuda, Toshifumi Doi, Yuji Naito, Yoshito Itoh, Toshikazu Yoshikawa. A novel expansion method for functional natural killer cells and its clinical application. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3137. doi:10.1158/1538-7445.AM2015-3137