AEEA-AEEA application prospects

The terminal carboxyl group of the molecule makes it weakly acidic (pKa ≈ 3.2) and completely ionizes into carboxylate ions (- COO ⁻) at physiological pH (7.4). This characteristic can be utilized to design pH dependent ADC release mechanisms, especially in tumor microenvironment and intracellular acidic organelle targeting, showing promising prospects.
The principle of pH dependent release: The pH values of the tumor microenvironment (pH 6.5-7.0) and lysosomes (pH 4.5-5.0) are significantly lower than those of normal tissues (pH 7.4). By utilizing the unstable properties of certain chemical bonds under acidic conditions, such as hydrazone bonds, aldehyde bonds, and vinyl ether bonds, targeted release can be achieved. The carboxylate group in this molecule can serve as a part of a "pH sensitive switch": for example, by connecting a carboxyl group to an amino containing molecule through a pH sensitive bond (such as cis aconitine), this bond can be hydrolyzed under acidic conditions to release drugs. Alternatively, carboxyl groups can form coordination complexes with metal ions, which dissociate under acidic conditions.
Specific design strategy: ① Hydrazone carboxyl synergistic system: The carboxyl group of the molecule is activated and reacted with a ketone containing drug (such as doxorubicin) to form a hydrazone bond. The half life of the hydrazone bond hydrolysis is about 1 hour at pH 5.0, while it is stable at pH 7.4. The ether bond in the linker enhances hydrophilicity, exposing the hydrazone bond fully to acidic environments. ② Metal chelation acid hydrolysis strategy: Utilizing the coordination ability of carboxyl groups with Fe ³ ⁺ or Zn ² ⁺, a metal polyphenol coordination network is constructed. Under acidic conditions, the coordination bond is broken, releasing the encapsulated drug. ③ PH responsive self elimination: Connect the amino group of the molecule to PABC drug, but the amino ester bond of PABC is stable under acidic conditions, so the strategy requires the introduction of additional pH sensitive groups (such as dimethyl maleic anhydride). In vitro release experiments showed that the release rate could reach 85% within 24 hours at pH 5.0, and was below 10% at pH 7.4. This pH dependent release is particularly suitable for lysosomal targeted ADC and tumor interstitial drug delivery, which can further enhance tumor selectivity.