BX471 hydrochloride (ZK-811752 hydrochloride) is a potent, selective non-peptide CCR1 antagonist (Ki: 1 nM for human CCR1). It shows 250-fold selectivity for CCR1 over CCR2, CCR5, and CXCR4.

MIP-1α-CCR1:1 nM （ki）, MCP-3-CCR1:5.5 nM （ki）, RANTES-CCR1:2.8 nM （ki）

BX471 is a potent functional antagonist based on its ability to inhibit a number of CCR1-mediated effects including Ca2+ mobilization, increase in extracellular acidification rate, CD11b expression, and leukocyte migration and it is also able to displace 125I-MIP-1α/CCL3 binding to mouse CCR1 in a concentration-dependent manner (Ki: 215 nM). BX471 demonstrates a greater than 10,000-fold selectivity for CCR1 compared with 28 G-protein-coupled receptors [1]. BX471 also inhibits the RANTES-mediated adhesion of T lymphocytes to activated endothelium [4]. BX471 (0.1-10 μM) shows dose-dependent inhibition of RANTES-mediated and shear-resistant adhesion on IL-1β-activated microvascular endothelium in shear flow in isolated blood monocytes. Increasing concentrations of BX471 inhibits the Ca2+ transients induced by MIP-1α/CCL3 in both human and mouse CCR1 (IC50s: 5.8 nM and 198 nM) [2].

BX471 has a borderline significant effect on the number of CCR5-positive CD8 cells in the peripheral blood. BX471 reduces the amount of FSP1-positive cells by 65% in UUO kidneys as compared with vehicle control [2]. BX471 (4 mg/kg, p.o. or i.v.) is orally active with a bioavailability of 60% in dogs. Furthermore, BX471 effectively reduces disease in a rat experimental allergic encephalomyelitis model of multiple sclerosis [1]. BX471 (20 mg/kg, s.c.) reaches peak plasma levels of 9 μM by around 30 minutes, and this rapidly declines to approximately 0.4 μM after 2 hours. From 4 to 8 hours the drug plasma levels drop to 0.1 μM or lower. Mice treated with 20 mg/kg of BX471 for 10 days shows a reduction of interstitial CD45 positive leukocytes of approximately 55%. Pretreatment with BX471 reduces macrophage and neutrophil accumulation in the kidney after ischemia-reperfusion injury [3].