AAK1-IN-4 is a potent and specific inhibitor of adaptor protein-2-associated kinase 1 (AAK1), capable of efficiently penetrating the central nervous system and exhibiting oral bioactivity. It has demonstrated a high degree of selectivity with an AAK1 inhibitory concentration (IC50) of 4.6 nM, a Filt dissociation constant (Ki) of 0.9 nM, and a cellular IC50 of 8.6 nM. AAK1-IN-4 holds promise as a valuable tool in the investigation of neuropathic pain [1].

AAK1-IN-4 (compound 43) at 0.5 μM for 0-10 minutes shows significant cell potency with a value of 2.4 in liver microsomes and high metabolic stability, with values of 95, 95, and 93 in human, rat, and mouse microsomes respectively, without detected CYP inhibition [1].

AAK1-IN-4, administered orally at a dosage of 3 mg/kg, substantially mitigates tactile allodynia, achieving nearly 80% pain response inhibition in a rat model of chronic constriction injury (CCI)-induced pain, alongside demonstrating considerable spinal cord penetration and an 8.8 spinal-cord-to-plasma concentration ratio. When dosage ranged from 1-10 mg/kg, AAK1-IN-4 significantly attenuated mechanical allodynia in a rat model of streptozotocin (STZ)-induced diabetic peripheral neuropathic pain (DPNP), with peak pain response inhibition exceeding 80% at 10 mg/kg and over 60% at 3 mg/kg. These findings underscore AAK1-IN-4's potent analgesic effects across different doses and neuropathic pain models, affirming its therapeutic potential.