The World of Immunotherapy Needs More Than PD-1/PD-L1—Two of the New Kids on the Block: LAG-3 and TIGIT

Immunotherapy has paved the way for the development of solid tumor new treatments in the last decade. The approval of immune checkpoint inhibitors such as anti PD-1/PD-L1 provided a revolution with optimal results. However, a considerable proportion of patients experience adverse therapeutic effects, and up to 50% may develop secondary resistance in the first three to five years. This has prompted the need for identifying new targets for immunotherapy that have good tolerance and biosafety and, of course, good tumoral response, either alone or in combination. Two of these new targets are the Lymphocyte-activation gene 3 (LAG-3) and the T cell immunoglobulin and ITIM domain (TIGIT). They are responsible for several interactions with the immune system, prompting an immunosuppressive phenotype in the tumor microenvironment. Both LAG-3 and TIGIT can be druggable, alone or in combination with anti-PD-1/PD-L1, with rather safe profiles making them attractive. In this review, we highlight some of the immune mechanisms of TIGIT and LAG-3 and their detection by immunohistochemistry, providing some insight into their use in the clinical setting.