GRK2 and osteoarthritis: Tesmer et al. found that paroxetine (PX) as a GRK2 inhibitor functioned well both in vitro and in vivo.[33] Kamal et al. used PX as a GRK2‐inhibitor to suppress the GPCR desensitization for treatment of osteoarthritis.[34] These examples suggest that low toxic “old drug” PX could serve as a GRK2 inhibitor to stabilize S1PR1 on T cell surface for releasing the sequestered T cells in the BM to boost GBM immunotherapy, which has not been investigated and reported.