Synthesis of CXCR2 and CCR7 chemokine receptor antagonists targeting a conserved intracellular binding site

Chemokines are a class of small, secreted proteins (8 - 12 kDa) that direct cellular trafficking and leukocyte migration to sites of inflammation and tumor growth. They are classified into four groups, i.e. the CXC, CC, XC and CX3C chemokines, distinguished based on the position of conserved cysteine residues in the amino terminus. The CXC and CC chemokines are the largest and most studied groups. Their cysteine residues are separated by a single amino acid (CXC) or are adjacent (CC). Chemokines bind to G-protein coupled receptors (GPCRs) to exert their biological effects. The CXC and CC motif chemokine receptors (CCR and CXCR) CXCR2 and CCR7 are involved in multiple diseases. CXCR2 is involved in the diverse inflammatory and autoimmune diseases, such as chronic obstructive lung disease (COPD), asthma, cystic fibrosis, acute lung injury, rheumatoid arthritis and psoriasis. Additionally, elevated CXCR2 signaling is observed in many cancers, including colon, breast, prostate, lung, ovary, pancreas and brain cancer, and correlates with a poor prognosis. Similarly, increased CCR7-expression is observed in many types of cancer, with tumor cells undergoing CCR7-mediated metastasis, predominantly to the lymph nodes. Metastasis is the hallmark of cancer that is expected to contribute to 90% of all cancer deaths. Therefore, antagonists of CXCR2 and CCR7 are promising agents for treatment of inflammatory disorders and cancer. The number of small-molecule CXCR2 antagonists that have been reported is fairly large. In contrast, very few CCR7 antagonists are known. One strategy for identifying new CCR7 antagonists, is screening CXCR2 antagonists that are known to target the intracellular binding site that is conserved among multiple human chemokine receptors. First, a previously reported thiazolo[4,5-d]pyrimidine based CXCR2 antagonist was selected that is known to target this intracellular binding pocket. Since few core-modified analogues of this compound were previously reported, this was a strong starting point for scaffold hopping with the aim of finding new CXCR2 and CCR7 chemotypes, and simultaneously filling in missing CXCR2 SAR-data. Fourteen scaffold analogues were prepared, which resulted in the discovery of three novel CXCR2 antagonists with IC50 values below 1 μM in both the binding and calcium mobilization assay. These are the triazolo[4,5-d]pyrimidine, isoxazolo[4,5-d]pyrimidine and pyrido[3,4-d]pyrimidine. CXCR2 antagonists containing these scaffolds had not been previously described. All three compounds could be further optimized by structural modification of the substituents. Hit-optimization of the pyrido[3,4-d]pyrimidine was attempted, by exploring different substituents at the 2-, 4-, 5-, and 6- position. In total 18 analogues were prepared. However, besides a single compound with five times lower potency, all compounds were inactive. In conclusion, the pyrido[3,4-d]pyrimidine is a 'singleton' hit compound. Screening of the 14-membered compound library of scaffold-modified analogues of thiazolo[4,5- d]pyrimidine CXCR2 antagonist for CCR7 antagonism, led to the discovery of a triazolo[4,5- d]pyrimidine hit-compound, with a Ca2+-flux IC50 of 2.13 μM against CCR7, and a selectivity of 0.3 for CCR7 versus CXCR2. Hit optimization was performed while varying the 3-, 5- and 7-positions, and preparing around 40 analogues. This resulted in the discovery of a 0.43 μM potent CCR7 antagonist with 25-fold selectivity over CXCR2.

Jaar van publicatie:2023

Toegankelijkheid:Open