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

Tamoxifen, a selective estrogen receptor modulator, reduces fat mass and induces adipose tissue browning in obese mice, suggesting its potential as an antiobesity drug. However, small-molecule therapies often cause nonspecific side effects. The goal is to transport 4-hydroxytamoxifen (4-OHT) specifically into cells using the human neuropeptide Y (NPY) receptor type 1 (hY₁R), which is highly expressed on the surface of adipocytes. NPY conjugates are generated that link 4-OHT with three enzymatically cleavable and one self-immolative diamine linkers. All conjugates exhibit similar behavior regarding receptor activation and internalization. The activity of the intracellularly released 4-OHT is measured using a luciferase reporter gene assay. The diamine linker construct is the only conjugate that induces full reporter gene activation after internalization. However, the attachment of the drug to the peptide is unstable. Among peptides with enzymatically cleavable linkers, the conjugate with the GFLG linker exhibits the greatest reporter gene activity and is selected for further validation. A detailed analysis of its stability is performed using chromatography and mass spectrometry. Excellent plasma stability is demonstrated by fluorescence and isotopic labeling. These results demonstrate successful drug transport into target cells, paving the way for the further optimization of obesity therapies with reduced side effects.