A phase I study on adoptive immunotherapy using gene-modified T cells for ovarian cancer

Abstract

Purpose: A phase I study was conducted to assess the safety of adoptive immunotherapy using gene-modified autologous T cells for the treatment of metastatic ovarian cancer.

Experimental design: T cells with reactivity against the ovarian cancer-associated antigen alpha-folate receptor (FR) were generated by genetic modification of autologous T cells with a chimeric gene incorporating an anti-FR single-chain antibody linked to the signaling domain of the Fc receptor gamma chain. Patients were assigned to one of two cohorts in the study. Eight patients in cohort 1 received a dose escalation of T cells in combination with high-dose interleukin-2, and six patients in cohort 2 received dual-specific T cells (reactive with both FR and allogeneic cells) followed by immunization with allogeneic peripheral blood mononuclear cells.

Results: Five patients in cohort 1 experienced some grade 3 to 4 treatment-related toxicity that was probably due to interleukin-2 administration, which could be managed using standard measures. Patients in cohort 2 experienced relatively mild side effects with grade 1 to 2 symptoms. No reduction in tumor burden was seen in any patient. Tracking 111In-labeled adoptively transferred T cells in cohort 1 revealed a lack of specific localization of T cells to tumor except in one patient where some signal was detected in a peritoneal deposit. PCR analysis showed that gene-modified T cells were present in the circulation in large numbers for the first 2 days after transfer, but these quickly declined to be barely detectable 1 month later in most patients. An inhibitory factor developed in the serum of three of six patients tested over the period of treatment, which significantly reduced the ability of gene-modified T cells to respond against FR+ tumor cells.

Conclusions: Large numbers of gene-modified tumor-reactive T cells can be safely given to patients, but these cells do not persist in large numbers long term. Future studies need to employ strategies to extend T cell persistence. This report is the first to document the use of genetically redirected T cells for the treatment of ovarian cancer.

Fig. 1

Growth and phenotype of gene-modified T cells. A, following allogeneic stimulation, 8 × 10⁷ Tcells were transduced with retroviral vector encoding the MOv-γ receptor and maintained at 1to 2 × 10⁶/mL in media containing IL-2. Transduced T cells were restimulated with allogeneic PBMCs on day 21, which resulted in further expansion of Tcells. Using this method, large numbers of dual-specificTcells could be generated. T cell expansion depicted is for patient 9. Representative of all six patients in cohort 2.The phenotype of transduced Tcells from cohort 2 of the study was determined with respect to T cell subset markers and chimeric receptor expression using specific antibodies and flow cytometry. B, although the relative proportions of CD4⁺ and CD8⁺ T cells varied between patients, the culture was made up predominantly of CD4⁺ and CD8⁺ cells as seen in the representative plot. C, expression of the chimeric MOv-γ receptor was evident following staining with anti-idiotype antibody (thick line) compared with isotype control antibody (thin line). Representative of all patients.

Fig. 2

Biodistribution of radiolabeled T cells. Patients received up to 7.5 × 10^{9 111}In-labeledTcells, and imaging was done using a gamma camera at intervals followingTcell transfer. A, representative image of four transfers that were done withTcells that received a single stimulation with OKT3. B, representative image of three transfers that were done usingTcells that had received two stimulations with OKT3. Radioisotope signal was detected in lungs, liver, and spleen. Radiolabeled cells were preferentially retained in lungs of patients that received twice stimulated Tcells. C, anteroposterior image of the abdomen of patient 4 at 48 hours after receiving T cells in cycle 2 with evidence of T cell localization to a peritoneal tumor (bottom) in addition to localization to liver (top).

Fig. 3

Preincubation of patient serum with protein G removed inhibitory activity. MOv-γ-transduced T cells were incubated overnight with IGROV-1tumor cells, and antitumor activity was determined by the amount of IFN-γ secreted. T cell activity was inhibited in the presence of serum taken from patient 9 afterTcell transfer. This inhibitory activity of posttreatment serum was removed by pretreatment of serum with protein G.