WAY 163909 hydrochloride is an effective agonist for the serotonin 5-HT2C receptor, with an EC50 value of 8 nM and a maximal efficacy of 90%. It shows minimal activity at the 5-HT2A receptor. The compound displays its selectivity with a Ki value of 10.5 nM at the 5-HT2C receptor, compared to higher Ki values at 5-HT2A (212 nM), 5-HT7 (343 nM), and 5-HT2B (485 nM) receptors, and it lacks significant activity at various other receptors.