RF24 | PSUN95 Defining Predictors of Weight Loss Response to Lorcaserin

Abstract The need for personalized medicine in obesity is pressing, but we are currently unable to predict individual responses to weight loss (WL) medications. The melanocortin (MC) system consisting of proopiomelanocortin (POMC) and agouti related protein (AgRP) neurons and brain MC-Rs plays a critical role in regulating energy homeostasis and is targeted by lorcaserin (LOR), a 5HT2cR agonist previously FDA approved for WL. We therefore investigated the short and long-term effects of LOR on the MC system as assessed by cerebrospinal fluid (CSF) neuropeptide measurements and other parameters in order to identify potential biomarkers to predict WL response. Methods In phase-1 of our two-phase study, thirty subjects with obesity were randomized to receive placebo or LOR for 7-days and were then crossed over to 7-days of LOR or placebo after a 3-week washout period. Subjects then continued to phase-2 and were treated with LOR for 6-months. The study was terminated early as LOR was withdrawn from the market and only 19 subjects completed 6M. Anthropometrics, plasma and CSF were collected and test meals were administered after both placebo and LOR during phase-1 and at the end of phase-2. POMC prohormone and the POMC-derived peptide, β-endorphin (β-EP), were measured in CSF by in house ELISA and RIA. The MC-R antagonist, AgRP, was measured by ELISA in CSF and plasma as both may reflect brain AgRP. Results During phase-1 there was a decline in CSF POMC (p=0.001) and an increase in CSF β-EP (p=0.0017) resulting in an increase in the ratio of β-EP /POMC (processed peptide/prohormone) (p<0.0001) after 7-days of LOR vs placebo. Serum insulin and HOMA-IR also decreased despite no WL during phase-1 (p<0.005). After 6M of LOR, average WL was 6.9%, with 11/19 subjects achieving >5% and 7/19 >10% WL. Leptin, insulin and HOMA-IR declined. CSF POMC remained lower and β-EP and β-EP/POMC remained higher after 6M vs 7-day placebo (baseline), whereas AgRP increased only at 6M. Anthropometrics and caloric intake during test meals were not significantly different between LOR and placebo in phase-1 and did not predict WL at 6M. Phase-1 changes in POMC or β-EP did not predict WL. However, baseline CSF POMC and POMC/AgRP ratio correlated negatively with WL and were significantly lower in subjects with >10% WL. A CSF POMC cutoff of < 220 fmol/ml at baseline was found to predict 10% WL at 6M (p=0.045 Fisher). Conclusion In this study we show that the melanocortin system is impacted after 1 week of LOR. Furthermore lower melanocortin activity at baseline predicted a better weight loss response to drug treatment. Assessment of melanocortin activity could thus provide a way to personalize the pharmacotherapy of obesity with possible future alternative selective 5HT2cR agonists. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m., Sunday, June 12, 2022 1:00 p.m. - 1:05 p.m.