Myeloid Maturity: ATRA to Enhance Anti–PD-1?

Summary Myeloid-derived suppressor cells (MDSC) are associated with resistance to anti-PD-1 therapies. All-trans retinoic acid (ATRA) may induce maturation of MDSCs and alter their immunosuppressive effects. Adding ATRA to pembrolizumab may target this resistance mechanism to enhance the overall impact of anti-PD-1–based immunotherapy. See related article by Tobin et al., p. 1209