This hexapeptide corresponding to residues 42-47 of the thrombin receptor has been shown to be a thrombin receptor activator. It caused half-maximal platelet aggregation at approx. 0.8 uM and was 5 times more potent than the parent peptide H-8105. In addition, SFLLRN is effective in causing tyrosine phosphorylation, inhibition of cAMP formation, and an increase in cytosolic Ca2+.