Human Vγ9δ2 T (GDT) cells, activated by a range of agents, including aminobisphosphonates such as zoledronate, have antitumor activities that may translate into effective treatment of human malignancy. Tumor responses have been observed following adoptive transfer of ex vivo expanded human GDT cells in a mouse tumor model and in lymphoma patients treated with zoledronate and interleukin-2 (IL-2). As zoledronate and low concentrations of chemotherapeutic agents markedly enhance GDT cell killing of tumor targets in vitro, clinical protocols that replicate this combination would be expected to be most likely to demonstrate any potential clinical benefit of GDT cell based therapies. Protocols for generation of large numbers of ex vivo expanded GDT cells would facilitate this as chemotherapy and zoledronate administration could be followed by infusion of cells after chemotherapy agents have been excreted. We aimed to determine the feasibility of expanding peripheral blood GDT cells from cancer patients for therapeutic application, to assess the safety and maximal tolerated doses of intravenous GDT infusions and to determine the destination of the infused GDT cells prior to clinically evaluating the combination of chemotherapy, zoledronic acid and ex vivo expanded GDT cells. To address this aim we conducted a phase I dose escalation study involving administration of zoledronate and autologous in vitro activated GDT cells to subjects with metastatic malignancy. Peripheral blood GDT cells were activated and expanded following leukapheresis by culture with zoledronic acid and 700 IU/ml of IL-2 for 7~14 days. Subjects received 8 GDT cells treatments, at weekly intervals, at 3 or 4 dose levels from 5 × 10^6 ~5 × 10^9 with the highest doses being determined by the number of available cells. Trafficking of administered GDT cells was determined by labeling 5 × 10^7 of the cells with indium-111 oxine and undertaking whole body imaging with clinical gamma-cameras at 1, 4, 8, 24 and 48 hours after administration. Our results were that from 18 of 41 subjects (44 %) sufficient cells could be generated from a single leukapheresis to escalate the doses until at least two doses of > 5 × 10^8 GDT could be administered. No dose limiting toxicity was observed up to the highest doses administered (1.5 × 10^9 cells). Following intravenous administration the majority of cells initially migrated to the lungs where they remained for 1~24 hours. Progressively, and generally beginning 1~4 hours after administration, the majority of GDT cells migrated from the lungs to the liver and spleen. In the small numbers of subjects evaluated it was difficult to evaluate for trafficking into tumors against the background of intense uptake in the lungs, liver and spleen and further evaluation of specifically selected patients is required. In conclusion, administration of large numbers of in vitro activated and expanded autologous GDT cells is safe and can be achieved in a significant proportion of subjects with malignancy. The majority of administered cells go to the lungs, liver and spleen suggesting that this mode of therapy may be most applicable to malignancies in these sites. Our data confirms that clinical studies of GDT cell therapy in combination with aminobisphosphonates and chemotherapy are feasible.

Disclosures: Administration of autologous gamma-delta T cells.; None of the authors listed have received any income from the listed companies.; Received research funding from Novartis and Medinet Ltd, Japan.

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