According to the World Health Organization, the number one cause of death is ischemic heart disease, responsible for 16% of the world’s total deaths in 2019. Statins are effective therapeutic agents used to reduce cardiovascular disease by inhibiting 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-R). Its adverse effects on muscles are generally explained by poor bioavailability and systemic administration route. Targeted delivery of statins in liver may be one way to reduce undesired side effects.
The asialoglycoprotein receptor (ASGPR) is a C-type (Ca²⁺-dependent) lectin which is highly expressed on the surface of hepatocytes. The primary physiological role of ASGPR is considered to be binding, internalization, and subsequent clearance from the circulation of galactose- and N-acetylgalactosamine-terminated glycoproteins. The location and the function make the receptor an ideal target for delivery of therapeutic agents to liver cells.
Herein, we report on synthesis and evaluation of the ASGPR-targeted atorvastatin conjugates. The conjugation of the selected carbohydrate fragments to atorvastatin generally produced a favorable effect on the hydrophilicity of the drug. Obtained conjugates demonstrated at least 4-fold higher molar solubility than that of atorvastatin. The molar solubility of the atorvastatin calcium salt was 0.11 ± 0.01 mM, while the molar solubilities of the obtained unprotected conjugates valued from 0.19 to 0.54 mM. The affinities to ASGPR have been assessed using surface plasmon resonance (SPR) spectroscopy technique. All of the synthesized conjugates decorated with N-acetylgalactosamine as a targeting moiety demonstrated greater affinity to ASGPR compared to unmodified atorvastatin. Compounds 2a and 2b exhibited subnanomolar binding to the receptor (K_D = 0.33 and 0.15 nM, respectively) which is 4 orders of magnitude lower than that measured for atorvastatin itself and the native ASGPR ligand N-acetylgalactosamine (K_D = 1.0 and 4.5 μM, respectively). The amide-based conjugates exhibited higher water solubility and stability for hydrolysis than ester-based atorvastatin conjugates. The release of atorvastatin after incubation of the conjugate in the presence of lysosomal protease was demonstrated. The results suggest that designed amine-based compounds are potential orally administrated liver-targeted prodrug of atorvastatin that can be used in clinical practice. The hepatic selectivity of synthesized conjugates is the subject of the further exploration.