Discovery of 3-benzyloxy-6-arylpyridazine derivatives as novel multi-target agents toward Parkinson's disease therapy

Based on the multitarget-directed ligand strategy, a series of pyridazine derivatives, including 3-benzyloxy-6-arylpyridazines, N-benzyl-6-(2-hydroxyphenyl) pyridazinones and 3-benzylthio-6-(2- hydroxyphenyl) pyridazines, were designed and synthesized. In vitro evaluation revealed that most 3-benzyloxy-6-arylpyridazines displayed potent and selective MAO-B inhibitory activity. Among them, compounds 6l (IC₅₀ = 0.0053 μM, SI > 1904.7) and 6s (IC₅₀ = 0.0031 μM, SI > 3194.8) were identified as the most promising inhibitors, acting via a reversible and competitive mechanism. Additionally, both compounds 6l and 6s demonstrated moderate antioxidant activity and strong chelating ability toward Cu²⁺. Notably, 6l effectively suppressed Cu²⁺-induced ROS generation. Further assessments of BBB permeability and aqueous solubility indicated that both 6l and 6s can penetrate the BBB, with 6l exhibiting moderate solubility. In anti-neuroinflammatory assays, 6l significantly inhibited LPS-induced activation of BV-2 cells and reduced the release of inflammatory factors NO、TNF-α and IL-1β. It also reduced LPS-induced intracellular ROS production, and protected SH-SY5Y cells from MPTP⁺-induced injury. Pharmacokinetics study confirmed that 6l could enter the central nervous system. In an MPTP-induced subacute mouse PD model, high-dose 6l significantly improved behavioral deficits, restored DA content, lowered MDA content, reduce oxidative stress and neuroinflammation. These results demonstrated that compound 6l is a promising multi-target anti-PD agent worthy of further investigation.