The water-solubility improvement mechanism of AEEA-AEEA

The off-target toxicity of ADCs is one of the primary factors limiting their therapeutic window. Sources of toxicity include: nonspecific binding of hydrophobic linkers-drug payloads to plasma proteins, uptake by liver sinusoidal endothelial cells, and clearance by the reticuloendothelial system after forming aggregates. AEEA-AEEA significantly enhances water solubility, thereby reducing off-target toxicity at multiple levels.
Water-soluble modification mechanism: The AEEA-AEEA backbone contains four ether oxygen atoms and two amide bonds. The ether oxygen atoms serve as strong hydrogen bond acceptors, with each oxygen capable of binding 1-2 water molecules; the NH and C=O groups of the amide bonds also participate in the hydrogen bonding network. Dynamic hydration number measurements indicate that a single AEEA-AEEA molecule can bind approximately 6-8 water molecules in aqueous solution, forming a stable hydration layer. This high hydration reduces the logP value of the linker-drug payload by 1.5-2.0 units (e.g., MMAE-monAEEA has a logP of ~3.5, while MMAE-AEEA-AEEA's logP drops to 1.8). Meanwhile, the spatial repulsion generated by the hydration layer effectively hinders hydrophobic binding with serum albumin and lipoproteins.
Off-target toxicity reduction effects: ① Reduced hepatic uptake: Hydrophilic ADCs are less recognized by clearance receptors on sinusoidal endothelial cells, leading to a 50-70% decrease in hepatic distribution and significant alleviation of hepatotoxicity (e.g., elevated transaminases). ② Mitigated thrombocytopenia: Hydrophobic ADCs often interact with platelet membranes, causing immune-mediated platelet destruction. AEEA-AEEA modification reduces platelet binding by 80%. ③ Alleviated peripheral neuropathy: Hydrophilic payloads struggle to cross the blood-nerve barrier, decreasing drug accumulation in dorsal root ganglia. In animal studies, ADCs with AEEA-AEEA linkers achieved a maximum tolerated dose (MTD) increase from 10 mg/kg to 25 mg/kg, expanding the therapeutic window by 2.5-fold. Currently, multiple clinical-stage ADCs (e.g., DS-8201 derivatives, SGN-35 improved variants) have adopted this strategy.