PROTAC Targeted Degradation of IRAK-4 as Potential Treatment in Cancer

Abstract

Toll-like receptors and interleukin-1 receptor directly interact with intracellular interleukin receptor associated kinase (IRAK) family members to initiate innate immune and inflammatory responses following activation by pathogens. The IRAK family members are involved in linking the innate immune response to the pathogenesis of various diseases, including cancers, non-infectious immune disorders, and metabolic disorders. The Patent Highlight showcases exemplary PROTAC compounds that exhibit a broad range of pharmacological activities associated with degradation of protein targets for the treatment of cancer.

Important Compound Classes

Title

Compounds and Methods for the Targeted Degradation of IRAK-4

Patent Publication Number

WO 2022/266258 A1 (URL: https://patents.google.com/patent/WO2022266258A1/en?oq=WO+2022%2f266258+A1)

Publication Date

December 22, 2022

Priority Application

US 63/210,880

Priority Date

June 15, 2021

Inventors

Araujo, E. M. V.; Cantley, J. L.; Hornberger, K. R.; Medina, J. R.

Assignee Company

Arvinas Operations, Inc. [US/US]; 5 Science Park, 395 Winchester Ave., New Haven, CT 06511, United States.

Disease Area

Cancer

Biological Target

IRAK-4

Summary

The interleukin-1 receptor-associated kinases (IRAKs) are key mediators of interleukin-1 receptor (IL1R) and Toll-like receptor (TLR) networks, which are critically involved in regulating the signaling of innate immune responses. IRAKs play important roles in transducing inflammatory signals downstream of the TLRs and IL-1Rs. The four members of the mammalian IRAK kinase family are IRAK-1, IRAK-2, IRAK-3 (IRAKM), and IRAK-4; however, only IRAK-1 and IRAK-4 exhibit kinase activity. IRAK-4 plays a key role in mediating IL1R/TLR signaling and is rapidly recruited to the receptor-signaling complex upon IL1R/TLR activation. Upon binding to IL1R/TLR, IRAK-4 interacts with IRAK-2 and MyD88 to form a large signaling complex, called the Myddosome. As such, IRAK-4 catalyzes the phosphorylation of IRAK-1, leading to its activation, hyperphosphorylation, and dissociation from the Myddosome complex. Following this, IRAK-1 interacts with the E3 ubiquitin ligase, TNF receptor-associated factor 6 (TRAF6).

In addition, the activated TRAF6 complex drives downstream events, including the IκB kinase (IKK)-nuclear factor-κB (NFκB) and mitogen-activated protein kinase (MAPK) signaling pathways. This ultimately result in the upregulation of proinflammatory cytokines. Inhibition of IRAK-1 and IRAK-4 kinases has been shown to suppress inflammation. In particular, IRAK-4 kinase inhibition in human primary monocytes stimulated with TLR7/8 agonist blocks inflammatory cytokine RNA and protein production, including IL-1, IL-6, and TNF. Previous attempts to inhibit the MyD88 pathway revealed that neither selective IRAK-4 kinase inhibitors nor a novel series of potent, specific IRAK-4 degraders targeting its scaffolding function exhibited significant anti-proliferative effects.

Human patients lacking IRAK-4 are severely immunocompromised, and knock-in mice containing inactive IRAK-4 were completely resistant to lipopolysaccharide- and CpG-induced shock, which illustrated that IRAK-4 kinase activity is essential for cytokine production, activation of MAPKs, and induction of NF-κB-regulated genes in response to TLR ligands. Therefore, given the central role of IRAK-4 in Toll-like/IL-1R signaling and immunological protection, IRAK-4 inhibitors have been identified as potentially valuable therapeutics in inflammatory diseases, sepsis, and autoimmune disorders. Furthermore, since IRAK-4 possesses scaffolding as well as kinase-dependent signaling activity, its degradation may be a valuable alternative to inhibition by small molecules.

E3 ubiquitin ligases confer substrate specificity for ubiquitination and therefore are more attractive therapeutic targets than general proteasome inhibitors due to their specificity for certain protein substrates. However, the development of ligands of E3 ligases has proven challenging, in part because they must disrupt protein–protein interactions. Notably, since the discovery of nutlins, the first small-molecule E3 ligase inhibitors, additional compounds have been reported that target E3 ligases.

Cereblon is a protein that in humans is encoded by the CRBN gene and forms an E3 ubiquitin ligase complex with damaged DNA binding protein 1 (DDB1), Cullin-4A (CUL4A), and regulator of cullins 1 (ROC 1). Cereblon ubiquitination of target proteins results in increased levels of fibroblast growth factor 8 (FGF8) and fibroblast growth factor 10 (FGF10). FGF8 in turn regulates several developmental processes, such as limb and auditory vesicle formation. In the absence of cereblon, DDB1 forms a complex with DDB2 that functions as a DNA damage-binding protein.

The disclosure in patent WO 2022266258 A1 describes bifunctional compounds having the structural formula ITM-LNK-CLM, which contains on one end a cereblon E3 ubiquitin ligase that binds to the E3 ubiquitin ligase and, on the other end, a moiety that binds the target protein, IRAK-4. The target protein is placed in close proximity to the ubiquitin ligase to effect degradation of target protein. The exemplary bifunctional compounds exhibit a broad range of pharmacological activities associated with degradation/inhibition of IRAK-4, which may treat or prevent diseases or disorders resulting from cellular signaling mediated by the target protein.

Key Structures

Biological Assay

ELISA protocol using human IRAK-4 matched antibody pair kit, OCI-Ly10, and PBMC cells. A pharmacodynamic study was conducted using C.B.17 SCID mice bearing OCI-LY1 tumor xenografts. Animals were dosed orally after tumors were inoculated, and IRAK-4 concentrations in the tumor samples were found to be much lower in the cells treated with exemplary compound Ex. 112.

Biological Data

The table below shows lipopolysaccharide (LPS)-stimulated IL-6 inhibition/R848-stimulated IL-6 inhibition IC₅₀, where A = <10.0 nM, B = ≥10.0 nM, and C = ≥50.0 nM. For D_max, Y_max value, A = ≥90, B = ≥80 and <90, and C = ≥70 and <80.

Recent Review Articles

See refs (1−6).

The author declares no competing financial interest.