Bispecific T cell engager (BsTe) is a fusion recombinant protein comprised of two single–chain variable fragments with dual specificity for a tumor–associated antigen (TAA) and T cell receptor (usually CD3ε). Immunotherapy with BsTe has shown efficacy in patients with hematologic malignancies and uveal melanoma. However, the antitumor efficacy of BsTe in most solid tumors has been limited due to their short serum half-life and insufficient tumor concentration. We designed a novel serotype 5/3 oncolytic adenovirus encoding for a BsTe cross-linking Mucin1 (MUC1) to CD3, Ad5/3–E2F–d24–aMUC1aCD3. The BsTe (aMUC1aCD3) is designed for the treatment of human solid tumors, where the BsTe links CD3 molecules on the surface of T cells and MUC1 on the target cancer cells.
Cell viability assays were used to assess the oncolytic potential of the novel Ad5/3–E2F–d24–aMUC1aCD3 construct. The functionality of virus-derived aMUC1aCD3 was evaluated in vitro using T cell activation, proliferation and cancer cell killing assays. The efficacy of the aMUC1aCD3 coding virus was investigated in vivo using a humanized MUC1 expressing lung cancer xenograft mouse model.
The addition of aMUC1aCD3 transgenes did not compromise virus replication capacity. When Ad5/3–E2F–d24–aMUC1aCD3 is combined with allogenic T cells, rapid tumor cell lysis upon infection was observed using different cancer cell lines. TILT-321 infected cells secreted functional aMUC1aCD3 engagers as evidenced by increased T cell activity and competitive binding to MUC1+ cells. Ad5/3–E2F–d24–aMUC1aCD3 treatment also led to effective anti–tumor efficacy in vivo in a human MUC1 expressing lung cancer xenograft model. This response was associated with increased intratumoral T cell activation mediated by the aMUC1aCD3-armed adenovirus.
This study provides proof-of-concept for an effective strategy to overcome some of the limitations of recombinant BsTe delivery in the treatment of solid tumors. The proposed technology could be beneficial for the treatment of solid tumors preferentially those expressing MUC1.
The authors.
Ida-Montin Foundation, Orion Foundation, Minerva Foundation, Jane and Aatos Erkko Foundation.
J.M. Santos, V. Cervera-Carrascon, S.Sorsa: Financial Interests, Institutional, Full or part-time Employment: TILT Biotherapeutics Ltd; Financial Interests, Personal, Stocks/Shares: TILT Biotherapeutics Ltd. R. Havunen: Financial Interests, Institutional, Full or part-time Employment: TILT Biotherapeutics Ltd. All other authors have declared no conflicts of interest.