Targeting the nonenzymatic scaffold function of RIPK1 via a VHL-recruiting PROTAC synergizes with immunotherapy in melanoma.

Receptor-interacting protein kinase 1 (RIPK1) mediates cell survival, inflammation, and cell death, and its kinase-independent scaffolding function drives tumor progression and therapeutic resistance, which cannot be eliminated by conventional RIPK1 kinase inhibitors. To overcome this limitation, we adopted proteolysis-targeting chimera (PROTAC) technology to achieve complete RIPK1 protein depletion. Through linker structural optimization with a rigid phenyl ring incorporation, we successfully identified a potent RIPK1 degrader, compound B11. In A375 and B16F10 melanoma cells, B11 exhibited robust RIPK1 degradation activity, with DC50 values of 4.48 nM and 4.61 nM, respectively, and a maximum degradation efficiency of 98% in both cell lines. Mechanistically, B11 induced VHL E3 ligase-dependent ubiquitination and proteasomal degradation of RIPK1, which ablated the kinase-independent scaffolding function and markedly sensitized melanoma cells to TNF-α-triggered cell death. In vivo studies verified that B11 significantly enhanced the efficacy of anti-PD-1 immunotherapy. Moreover, combined treatment with B11 and a STING agonist further improved antitumor efficacy. This work demonstrates that PROTAC-mediated RIPK1 degradation is a viable strategy to target undruggable scaffolding functions of RIPK1, providing a novel lead compound B11, encoded with KWGS-B11, and design paradigm for RIPK1-targeted anticancer drug development.