Preconditioning of the tumor microenvironment with oncolytic reovirus converts CD3-bispecific antibody treatment into effective immunotherapy

Abstract

BackgroundT-cell-engaging CD3-bispecific antibodies (CD3-bsAbs) are promising modalities for cancer immunotherapy. Although this therapy has reached clinical practice for hematological malignancies, the absence of sufficient infiltrating T cells is a major barrier for efficacy in solid tumors. In this study, we exploited oncolytic reovirus as a strategy to enhance the efficacy of CD3-bsAbs in immune-silent solid tumors.MethodsThe mutant p53 and K-ras induced murine pancreatic cancer model KPC3 resembles human pancreatic ductal adenocarcinomas with a desmoplastic tumor microenvironment, low T-cell density and resistance to immunotherapy. Immune-competent KPC3 tumor-bearing mice were intratumorally injected with reovirus type 3 Dearing strain and the reovirus-induced changes in the tumor microenvironment and spleen were analyzed over time by NanoString analysis, quantitative RT-PCR and multicolor flow cytometry. The efficacy of reovirus in combination with systemically injected CD3-bsAbs was evaluated in immune-competent mice with established KPC3 or B16.F10 tumors, and in the close-to-patient human epidermal growth factor receptor 2 (HER2)+ breast cancer model BT474 engrafted in immunocompromised mice with human T cells as effector cells.ResultsReplication-competent reovirus induced an early interferon signature, followed by a strong influx of natural killer cells and CD8+ T cells, at the cost of FoxP3+ Tregs. Viral replication declined after 7 days and was associated with a systemic activation of lymphocytes and the emergence of intratumoral reovirus-specific CD8+ T cells. Although tumor-infiltrating T cells were mostly reovirus-specific and not tumor-specific, they served as non-exhausted effector cells for the subsequently systemically administered CD3-bsAbs. Combination treatment of reovirus and CD3-bsAbs led to the regression of large, established KPC3, B16.F10 and BT474 tumors. Reovirus as a preconditioning regimen performed significantly better than simultaneous or early administration of CD3-bsAbs. This combination treatment induced regressions of distant lesions that were not injected with reovirus, and systemic administration of both reovirus and CD3-bsAbs also led to tumor control. This suggests that this therapy might also be effective for metastatic disease.ConclusionsOncolytic reovirus administration represents an effective strategy to induce a local interferon response and strong T-cell influx, thereby sensitizing the tumor microenvironment for subsequent CD3-bsAb therapy. This combination therapy warrants further investigation in patients with non-inflamed solid tumors.

Oncolytic viruses encoding bispecific T cell engagers: a blueprint for emerging immunovirotherapies

“…A recent study used a fourth OV, reovirus, for preconditioning prior to BiTE treatment rather than directly using BiTE-encoding vectors [ 128 ]. In this paper, reovirus treatment of immunocompetent mice bearing s.c. KPC3 murine pancreatic tumors was shown to induce an interferon response in tumor tissue, followed by an influx of immune effector cells.…”

“…However, as opposed to OV delivery, this may not necessarily overcome current limitations of BiTE therapy regarding intratumoral infiltration of T cells and on-target off-tumor toxicities. In addition, tumor-infiltrating virus-specific T cells induced by OV therapy can represent a potent effector cell pool for BiTE-mediated tumor cell killing [ 128 ]. An alternative approach makes use of a truncated CD19 antigen encoded by an oncolytic Vaccinia virus, aiming at directing CD19-specific CAR T cells toward virus-infected cells [ 139 ].…”

Overcoming Challenges for CD3-Bispecific Antibody Therapy in Solid Tumors

“…The replication of oncolytic virus can generate an interferon response in the TME and induce an innate and adaptive antiviral immune response [ 131 , 132 , 133 ]. We used this concept to pre-treat immune desert murine tumors (B16F10 melanoma and (LSL-Kras G12D , LSL-Trp53 R172H , Pdx-1-Cre) KPC pancreatic carcinoma) with OV, which induced sensitization and generated major T-cell influx peaking around day 7, allowing strong tumor regression upon CD3-BsAb treatment [ 134 ]. In the absence of OV sensitization, CD3-BsAb did not even delay tumor growth, underlining the importance of an inflammatory TME.…”

Acquired Resistance to Immune Checkpoint Blockades: The Underlying Mechanisms and Potential Strategies

“…Oncolytic virotherapy is an effective way to elicit new immunogenicity for tumors lacking in neoantigen ( 137 – 140 ). In the case reports of talimogene laherparepvec (T-VEC) treatment to overcome AR to ICBs in melanoma patients, three of six patients were evaluated as PR ( 141 ).…”