Background: The two new strata of the INSIGHT trial evaluate feasibility and safety of s.c. injections of IMP321 (eftilagimod alpha) in combination with either SOC first/second-line drug therapy (Stratum C) or in combination with an PD-L1 inhibitor (avelumab; Stratum D) in advanced stage solid tumors as well as to generate first efficacy data. This proof-of-concept data could build the basis for further clinical studies exploring the therapeutic potential of combinations of active immunotherapy using IMP321 with SOC drug therapies or immunotherapies targeting the PD-1/PD-L1 axis in various solid tumor entities. IMP321 is a MHC class II agonist that activates antigen-presenting cells (primary target cells) and then CD8 T cells (secondary target cells). Activation of the dendritic cell network and subsequent T cell recruitment at the tumor site with IMP321 may lead to enhanced anti-tumor CD8 T cell responses. Thus, especially combinations with PD-1/PD-L1 inhibitors might display interesting effects by activating immune cells and disabling immune inhibitory mechanisms at the same time. Methods: This is a prospective investigator initiated phase I trial consisting of four strata. New stratum C: Patients with solid tumors treated with SOC chemo- or targeted therapy in first or second line receive concomitant s.c. IMP321 injections. This combination is aimed to enhance the immune response against tumor cells compared to chemo-/targeted SOC therapy alone. New stratum D: Patients will receive avelumab i.v. q2w along with s.c. IMP321 injections. This combination is aimed to enhance efficacy by combining IMP321’s activating effects on immune cells with the release of immune inhibitory effects caused by interruption of the PD-1/PD-L1 axis. It is planned to enroll 20 patients in Stratum C and 12 patients in stratum D. Main efficacy endpoint is the overall response rate (RECIST 1.1). Overall recruitment has started; currently (Feb 2019) 14 patients have been enrolled. EudraCT: 2016-002309-20. Clinical trial information: NCT03252938