Quantitative relationships between steroid structure and binding to putative progesterone receptors

Area of Science:

• Medicinal Chemistry
• Molecular Pharmacology
• Steroid Chemistry

Background:

• Progesterone receptors (PRs) are crucial in reproductive biology and disease.
• Understanding structure-activity relationships (SAR) of PR ligands is vital for drug development.
• Androst-4-en-3-one derivatives represent a class of compounds with potential PR interactions.

Purpose of the Study:

• To establish quantitative relationships between the chemical structure of androst-4-en-3-one derivatives and their binding affinity to putative progesterone receptors.
• To develop a predictive model for ligand-receptor interactions.

Main Methods:

• Synthesis and characterization of 55 androst-4-en-3-one derivatives.
• In vitro binding assays to determine relative binding affinity to rabbit progesterone receptors.
• Quantitative Structure-Activity Relationship (QSAR) analysis using regression modeling.

Main Results:

• A QSAR equation was derived, correlating binding affinity with structural parameters: pia, pib, surface area in/out of hydrophobic pockets, MK, and conformational changes.
• The equation demonstrated a high predictive capability (r=0.88) for known compounds.
• Surface area parameters, particularly within hydrophobic pockets, significantly influenced binding affinity.

Conclusions:

• The study successfully established a quantitative model for predicting progesterone receptor binding affinity of androst-4-en-3-one derivatives.
• Molecular shape and hydrophobic interactions are key determinants of ligand binding to progesterone receptors.
• The developed model can guide the design of novel PR modulators.