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In malignant diseases, targeting of immune checkpoints successfully changed the therapeutic landscape and helped to unleash anti-tumor T cell responses, resulting in durable clinical outcomes, but only in up to 50% of patients. The success of these therapies and the need to overcome intrinsic and acquired therapy resistance stimulated research to identify new pathways and targets. Numerous clinical trials are currently evaluating novel checkpoint inhibitors or recently developed strategies like modulating the tumor microenvironment, mostly in combination with approved therapies. This short review briefly discusses promising therapeutic targets, currently still under investigation, with the chance to realize clinical application in the foreseeable future.