Dual Targeting Approach Using 4-Hydroxytamoxifen Neuropeptide Y Conjugates for Selective Addressing of Adipose Tissue

Area of Science:

• Pharmacology
• Biochemistry
• Metabolic Diseases

Background:

• Selective estrogen receptor modulators like tamoxifen show potential for obesity treatment by reducing fat mass and promoting adipose tissue browning.
• Current small-molecule therapies for obesity often lead to nonspecific side effects, necessitating targeted delivery approaches.
• Adipocytes, the cells that store fat, highly express the human neuropeptide Y receptor type 1 (hY1R), presenting a potential target for drug delivery.

Purpose of the Study:

• To develop a targeted drug delivery system for 4-hydroxytamoxifen (4-OHT) to adipocytes using the hY1R.
• To design and synthesize NPY conjugates linking 4-OHT with various linkers (enzymatically cleavable and self-immolative diamine).
• To evaluate the efficacy and stability of these conjugates for potential obesity therapeutics with reduced side effects.

Main Methods:

• Synthesis of NPY conjugates linking 4-OHT with three enzymatically cleavable and one self-immolative diamine linker.
• Assessment of receptor activation and cellular internalization of the conjugates.
• Measurement of intracellular 4-OHT activity using a luciferase reporter gene assay.
• Stability analysis of promising conjugates using chromatography, mass spectrometry, fluorescence, and isotopic labeling.

Main Results:

• All synthesized conjugates demonstrated similar receptor activation and internalization.
• The self-immolative diamine linker conjugate showed full reporter gene activation but exhibited unstable drug attachment.
• The conjugate with the GFLG enzymatically cleavable linker displayed the highest reporter gene activity and was selected for further study.
• The GFLG conjugate demonstrated excellent plasma stability, confirmed by fluorescence and isotopic labeling.

Conclusions:

• Targeted delivery of 4-OHT to adipocytes via NPY conjugates is feasible.
• The GFLG linker conjugate shows promise for enhanced stability and efficacy in delivering anti-obesity drugs.
• This approach represents a significant step towards developing obesity therapies with improved targeting and potentially fewer side effects.