MART-1 TCR gene-modified peripheral blood T cells for the treatment of metastatic melanoma: a phase I/IIa clinical trial

Background: Adoptive cell therapy with peripheral blood T cells expressing transgenic T-cell receptors (TCRs) is an innovative therapeutic approach for solid malignancies. We investigated the safety and feasibility of adoptive transfer of autologous T cells expressing melanoma antigen recognized by T cells 1 (MART-1)-specific TCR, cultured to have less differentiated phenotypes, in patients with metastatic melanoma.

Materials and methods: In this phase I/IIa trial, peripheral blood T cells from HLA-A2∗02:01-positive patients with unresectable stage IIIC/IV melanoma expressing MART-1 were selected and stimulated with anti-CD3/CD28 beads, transduced with a modified MART-1_(26-35)-specific 1D3 TCR (1D3HMCys) and expanded in interleukin (IL)-7 and IL-15. Patients received a single infusion of transgenic T cells in a dose-escalating manner. Feasibility, safety and objective response rate were assessed.

Results: Twelve pretreated metastatic cutaneous (n = 7) and uveal (n = 5) melanoma patients were included. Patient 1 received 4.6 × 10⁹ 1D3HMCys T cells and experienced grade 5 toxicity after 9 days. Subsequent patients received 5.0 × 10⁷ [n = 3; cohort (c) 2], 2.5 × 10⁸ (n = 2; c3) and 1.0 × 10⁸ (n = 6; c4) 1D3HMCys T cells. The study was prematurely terminated because of dose-dependent toxicity, concerning skin (10/12), eyes (3/12), ears (4/12) and cytokine release syndrome (5/12), with 7 patients experiencing grade 3-5 toxicity. Partial responses were seen in 2/11 (18%) assessable patients and persistence of 1D3HMCys T cells corresponded to infused cell dose.

Conclusions: Production of TCR-modified cells as described leads to highly potent T cells. Partial responses were seen in 18% of patients with dose-dependent 'on-target, off-tumor' toxicity and a maximum tolerated dose of 1.0 × 10⁸ cells.