A RIPK1-specific PROTAC degrader achieves potent antitumor activity by enhancing immunogenic cell death.

Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) functions as a critical stress sentinel that coordinates cell survival, inflammation, and immunogenic cell death (ICD). Although the catalytic function of RIPK1 is required to trigger cell death, its non-catalytic scaffold function mediates strong pro-survival signaling. Accordingly, cancer cells can hijack RIPK1 to block necroptosis and evade immune detection. We generated a small-molecule proteolysis-targeting chimera (PROTAC) that selectively degraded human and murine RIPK1. PROTAC-mediated depletion of RIPK1 deregulated TNFR1 and TLR3/4 signaling hubs, accentuating the output of NF-κB, MAPK, and IFN signaling. Additionally, RIPK1 degradation simultaneously promoted RIPK3 activation and necroptosis induction. We further demonstrated that RIPK1 degradation enhanced the immunostimulatory effects of radio- and immunotherapy by sensitizing cancer cells to treatment-induced TNF and interferons. This promoted ICD, antitumor immunity, and durable treatment responses. Consequently, targeting RIPK1 by PROTACs emerges as a promising approach to overcome radio- or immunotherapy resistance and enhance anticancer therapies.

Sculpting the tumour microenvironment by combining radiotherapy and ATR inhibition for curative-intent adjuvant immunotherapy.

The combination of radiotherapy/chemoradiotherapy and immune checkpoint blockade can result in poor outcomes in patients with locally advanced head and neck squamous cell carcinoma (HNSCC). Here, we show that combining ATR inhibition (ATRi) with radiotherapy (RT) increases the frequency of activated NKG2A+PD-1+ T cells in animal models of HNSCC. Compared with the ATRi/RT treatment regimen alone, the addition of simultaneous NKG2A and PD-L1 blockade to ATRi/RT, in the adjuvant, post-radiotherapy setting induces a robust antitumour response driven by higher infiltration and activation of cytotoxic T cells in the tumour microenvironment. The efficacy of this combination relies on CD40/CD40L costimulation and infiltration of activated, proliferating memory CD8+ and CD4+ T cells with persistent or new T cell receptor (TCR) signalling, respectively. We also observe increased richness in the TCR repertoire and emergence of numerous and large TCR clonotypes that cluster based on antigen specificity in response to NKG2A/PD-L1/ATRi/RT. Collectively, our data point towards potential combination approaches for the treatment of HNSCC.

Harnessing radiotherapy-induced NK-cell activity by combining DNA damage-response inhibition and immune checkpoint blockade.

BACKGROUND: Despite therapeutic gains from immune checkpoint inhibitors (ICI) in many tumor types, new strategies are needed to extend treatment benefits, especially in patients failing to mount effective antitumor T-cell responses. Radiation and drug therapies can profoundly affect the tumor immune microenvironment. Here, we aimed to identify immunotherapies to increase the antitumor response conferred by combined ataxia telangiectasia and Rad3-related kinase inhibition and radiotherapy. METHODS: Using the human papillomavirus (HPV)-negative murine oral squamous cell carcinoma model, MOC2, we assessed the nature of the antitumor response following ataxia telangiectasia and Rad3-related inhibitor (ATRi)/radiotherapy (RT) by performing RNA sequencing and detailed flow cytometry analyses in tumors. The benefit of immunotherapies based on T cell immunoreceptor with Ig and ITIM domains (TIGIT) and Programmed cell death protein 1 (PD-1) immune checkpoint blockade following ATRi/RT treatment was assessed in the MOC2 model and confirmed in another HPV-negative murine oral squamous cell carcinoma model called SCC7. Finally, immune profiling was performed by flow cytometry on blood samples in patients with head and neck squamous cell carcinoma enrolled in the PATRIOT clinical trial of combined ATRi/RT. RESULTS: ATRi enhances radiotherapy-induced inflammation in the tumor microenvironment, with natural killer (NK) cells playing a central role in maximizing treatment efficacy. We demonstrated that antitumor activity of NK cells can be further boosted with ICI targeting TIGIT and PD-1. Analyses of clinical samples from patients receiving ATRi (ceralasertib) confirm the translational potential of our preclinical studies. CONCLUSION: This work delineates a previously unrecognized role for NK cells in the antitumor immune response to radiotherapy that can be augmented by small-molecule DNA damage-response inhibitors and immune checkpoint blockade.