While targeting the PD1/PDL1 axis with therapeutic antibodies (eg. nivolumab / atezolizumab) offers unprecedented clinical benefit in metastatic melanoma and lung cancer, durable responses are observed only in a fraction of patients. To evaluate novel drugs capable of leveraging the efficacy of PD1/PD-L1 axis blockade, Explicyte has validated a series of in vivo tumor models of anti-PD-L1 and anti-PD1 antibody therapy. In these models, we propose to strengthen the preclinical efficacy data by ancillary mechanism of action (MOA) studies relying on the quantification of key immunological markers, within the tumor or in peripheral organs. These validated models can also support research of specific innovative biomarkers capable of identifying responding and non-responding subjects.