G-Protein antagonist peptides are primarily utilized in research to study G-protein-coupled receptor (GPCR) signaling pathways. By inhibiting G-protein activation, these peptides help scientists understand the role of GPCRs in cellular processes and disease mechanisms. They are also used in drug development to identify potential therapeutic targets for conditions like cancer, cardiovascular diseases, and neurological disorders. Additionally, these peptides aid in dissecting the complex interactions between GPCRs and their downstream effectors, providing insights into signaling cascades and potential intervention points for pharmacological treatments.