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Adoptively transferred melanoma-reactive CTL primed in the presence of IL-21 and transferred with concurrent CTLA4 blockade results in enhanced CTL persistence and tumor regression

Anti-CTLA4 monotherapy yields long-term benefit in < 10% of patients with metastatic melanoma, with most patients failing to respond likely due to inadequate expansion of endogenous tumor-reactive T cells. We postulated that adoptive transfer of melanoma-reactive CD8+ cytotoxic T lymphocytes (CTL) primed in the presence of Interleukin-21 (IL-21), which programs antigen-specific cells to retain characteristics of long-lived memory cells, could provide a bolus of immune effectors with enhanced in vivo persistence that, in combination with anti-CTLA4 blockade, would lead to tumor regression. Of ten patients with therapy-resistant melanoma, 4 patients experienced durable clinical responses, including 2 complete responders (CR,100% regression), and 2 partial responders (PR, 79% and 75% regression respectively). Three additional patients experienced stable disease (SD). The infused CTL were detected in the peripheral blood at frequencies up to 8% in all patients for up to 40 weeks. In patients with clinical benefit (CR, PR, SD), the persisting CTL exhibited CD28 expression, secreted IL-2, proliferated in vitro, and acquired central memory phenotype. These patients developed de novo anti-tumor responses (epitope spreading) to non-targeted antigens. This study represents a first-in-man study combining antigen-specific T cell therapy with immune checkpoint blockade, and highlights a potential synergistic biologic and therapeutic effect.

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Correspondence to Cassian Yee.

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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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  • Melanoma
  • Stable Disease
  • Tumor Regression
  • Metastatic Melanoma
  • Adoptive Transfer