Abstract
Interleukin-1 (IL-1) family cytokines are potent mediators of inflammation, acting to coordinate local and systemic immune responses to a wide range of stimuli. Aberrant signaling by IL-1 family cytokine members, however, is linked to myriad inflammatory syndromes, autoimmune conditions and cancers. As such, blocking the inflammatory signals inherent to IL-1 family signaling is an established and expanding therapeutic strategy. While several FDA-approved IL-1 inhibitors exist, including an Fc fusion protein, a neutralizing antibody, and an antagonist cytokine, none specifically targets the co-receptor IL-1 receptor accessory protein (IL-1RAcP). Most IL-1 family cytokines form productive signaling complexes by binding first to their cognate receptors – IL-1RI for IL-1α and IL-1β; ST2 for IL-33; and IL-36R for IL-36α, IL-36β and IL-36γ – after which they recruit the shared secondary receptor IL-1RAcP to form a ternary cytokine/receptor/co-receptor complex. Recently, IL-1RAcP was identified as a biomarker for both AML and CML. IL-1RAcP has also been implicated in tumor progression in solid tumors and an anti-IL1RAP antibody (nadunolimab, CAN04) is in phase II clinical studies in pancreatic cancer and non-small cell lung cancer (NCT03267316). As IL-1RAcP is common to all of the abovementioned IL-1 family cytokines, targeting this co-receptor raises the possibility of selective signaling inhibition for different IL-1 family cytokines. Indeed, previous studies of IL-1β and IL-33 signaling complexes have revealed that these cytokines employ distinct mechanisms of IL-1RAcP recruitment even though their overall cytokine/receptor/co-receptor complexes are structurally similar. Here, using functional, biophysical, and structural analyses, we show that antibodies specific for IL-1RAcP can differentially block signaling by IL-1 family cytokines depending on the distinct IL-1RAcP epitopes that they engage. Our results indicate that targeting a shared cytokine receptor is a viable therapeutic strategy for selective cytokine signaling inhibition.
Highlights
Interleukin-1 (IL-1), a critical regulator of inflammation and pro-inflammatory cytokine of the IL-1 superfamily, has long been known to play a role in inflammatory syndromes, autoimmune diseases, and cancers [1,2,3,4,5,6]
Targeting a shared co-receptor in order to inhibit signaling, raises the question as to the antibody’s effect on signaling by the diverse members of the IL-1 cytokine family: If an antibody targets a shared IL-1 family signaling co-receptor, will it inhibit just IL-1? Or will it affect IL-33 signaling? And, what is the feasibility of targeting a shared co-receptor to selectively inhibit signaling by cytokines that require the same co-receptor? Here, we show that the inhibitory potency and cytokine specificity of an anti-IL-1RAcP antibody depends predominantly on the location and composition of its epitope on the IL-1RAcP co-receptor
Using a range of functional, structural, and biophysical analyses, we provide the molecular basis for how two anti-IL-1RAcP antibodies, CAN03 and CAN04, exert distinct potencies in IL-1b inhibition while both preferentially inhibit IL-1b versus IL-33 signaling
Summary
Interleukin-1 (IL-1), a critical regulator of inflammation and pro-inflammatory cytokine of the IL-1 superfamily, has long been known to play a role in inflammatory syndromes, autoimmune diseases, and cancers [1,2,3,4,5,6]. The cytokine/receptor complex (IL-1/IL-1RI) recruits the common co-receptor Interleukin-1 receptor accessory protein (IL-1RAcP). As this ternary complex (IL-1/ IL-1RI/IL-1RAcP) forms, Toll/Interleukin-1 receptor (TIR) domains, attached through single transmembrane helices to each receptor, engage one another intracellularly, initiating a potent signaling cascade. Blocking this inflammatory signal at the cytokine/receptor level is currently the most common and effective therapeutic strategy
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