Cell-selective telomere damage by thiopurine-based oligonucleotide for diffuse large B cell lymphoma immunotherapy

Telomerase (TERT) is an enzyme involved in maintaining telomere length in diffuse large B cell lymphoma (DLBCL). Previous attempts to target TERT(+) cancers faced challenges, including the delayed clinical responses and on-target/off-tumor toxicities. Here, we present a DLBCL-targeted oligonucleotide designed to deliver a synthetic TERT substrate, 6-thio-2'-deoxy-guanosine (6tdG), damaging telomeres and triggering apoptosis. In vitro, 6tdG-oligonucleotides (6tdGOs) were selectively cytotoxic to TERT(+) DLBCL cells without affecting activated T cells or non-malignant TERT(-) cells. Repeated intravenous administration of 6tdGO, but not 6tdG nucleoside, had significant antitumor effects against xenotransplanted human DLBCL models and syngeneic Eμ-myc/15A lymphoma in mice. In immunocompetent mice, treatment with 6tdGO induced systemic, lymphoma-specific, and CD8 T cell-mediated antitumor immune responses. The abscopal effects of 6tdGO were abolished in mice lacking expression of Sting1 or Ifnar1 but not Trl9. These findings suggest that 6tdGO-induced lymphoma cell death triggered STING-mediated type-I interferon signaling, thereby promoting recruitment/activation of CD8 T cells. Importantly, the repeated 6tdGO treatments were well-tolerated in humanized hCD34/NOG mice. Except for the reduced percentage of human B cells, 6tdGO did not decrease the numbers of hematopoietic stem cells, myeloid cells, or T cells. Overall, 6tdGO offers an effective and safer strategy against aggressive TERT(+) DLBCL with potential to activate T cell-based antitumor immunity.