RLX-33

Potency assay, off target (cells): Within target family: RLX-33 had no detectable agonist activity (or antagonist activity at RXFP1 at all concentrations tested up to 30 μM. TLX-33 had no detectable agonist activity in the presence of FSK compared to the agonist relaxin-3 and displayed weak antagonist activity (<30% inhibition at 100 μM in CHO-hRXFP4 cells).

Potency assay (off target): Outside target family: RLX-33 was assessed in radioligand binding assays against a panel of 45 GPCRs, ion channels, and transporters at the NIMH Psychoactive Drug Screening Program (PDSP): at 10 μM had little to no off-target activity (<50% inhibition) with the exception of the 5-HT2c receptor, muscarinic M2 receptor, and sigma-2 receptor with inhibitions of 53, 51, and 95%, respectively. A follow-up confirmation assay determined that RLX-33 had weak affinity at sigma-2 with a Ki = 3.2 μM.