PD-1 cis-targeted IL-2v in combination with radiotherapy inhibits lung cancer growth and remodels the immune microenvironment.

Background: More efficient therapeutic options for non-small cell lung cancer (NSCLC) are needed as the survival at 5 years of metastatic disease is near zero. In this regard, we used a preclinical model of metastatic lung adenocarcinoma (SV2-OVA) to assess the safety and efficacy of novel radio-immunotherapy combining hypofractionated radiotherapy (HRT) with muPD1-IL2v immunocytokine and muFAP-CD40 bispecific antibody.

Methods: We evaluated the changes in the lung immune microenvironment at multiple timepoints following combination therapies and investigated their underlying antitumor mechanisms. Additionally, we analyzed the tumor clonal heterogeneity upon the combination treatments to explore potential mechanisms associated with the lack of complete response.

Results: The combination of HRT with muPD1-IL2v had a potent antitumor effect and increased survival in the SV2-OVA lung cancer model. Importantly, this combination therapy was devoid of measurable toxicity. It induced remodeling of the immune contexture through the increase of CD8⁺ T and natural killer (NK) cells. The addition of muFAP-CD40 to the combination treatment further increased infiltrating CD8⁺ T cells, expressing high levels of effector molecules, both in the periphery and core tumor regions. An accumulation of CD8⁺ PD-1⁺ TOX⁺ (exhausted) T cells, already at the 'early' timepoint, is consistent with the limited clinical benefits provided by the various combination treatments in this model. The study of the clonal dynamics of tumor cells during disease progression and therapy highlighted a clonal selection upon HRT+muPD1-IL2v therapy.

Conclusions: We demonstrated that HRT+muPD1-IL2v combination is a potent therapeutic strategy to delay tumor growth and increase survival in a metastatic lung cancer model, but additional studies are required to completely understand the resistance mechanisms associated with the lack of complete response in this model.