5-HT2C receptor agonists
BI-4752
BI-4752 and BI-3234 are potent and full 5-HT2C receptor agonists and have high selectivity against the 5-HT2A and 5-HT2B receptors. They have shown good solubility and moderate permeability in vitro. In rats, both molecules have a good PK profile with high bioavailability, so they are suitable for in vivo experiments.
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The 5-HT2C receptor is a G-protein coupled receptor (GPCR). It belongs to the 5-HT2 sub-family, which is one of 14 serotonin receptor subtypes1. This particular 5-HT2 sub-family comprises of the 5-HT2A, 5-HT2B, and 5-HT2C receptors, which all share considerable sequence homology. While the 5-HT2A and 5-HT2B receptors are expressed both peripherally and, in the CNS, 5-HT2C is exclusively expressed in the CNS. To avoid potential side effects (e.g. hallucinations for 5-HT2A2, cardiac valvulopathy and pulmonary hypertension for 5-HT2B)3, substantial selectivity is desired. Both molecules fulfill this criterion. There is pre-clinical evidence that targeting the 5-HT2C receptor represents a potentially new treatment approach against a variety of diseases such as schizophrenia, obesity, sexual dysfunction, urinary incontinence, and diabetes4,5. A crystal structure of the human 5-HT2C receptor in complex with the serotonin receptor antagonist ritanserin was reported in 2018 (Figure 3)6.
BI-4752 and BI-3234 have been designed in a joint project of Boehringer Ingelheim and Evotec, whereby Evotec was involved in the synthesis and the design of the molecule.
Crystal structure of human 5-HT2C receptor in complex with ritanserin (PDB code:6 6BQH, 2.7 Å resolution)
BI-4752 displays an EC50 (5-HT2C) of 11 nM and is a weak partial 5-HT2B (EC50 = 2037 nM, Emax = 58%) and 5-HT2A (EC50 = 1881 nM, Emax = 50%) agonist. BI-4752 is selective against 5-HT1B (IC50 > 10,000 nM). BI-3234 is also a potent full 5-HT2C agonist (EC50 = 35 nM), with an even higher selectivity against the 5-HT2B and 5-HT2A receptors.
| PROBE NAME / CONTROL MOLECULE | BI-4752 | BI-3234 |
| MW [Da, free base]a | 368.5 | 382.5 |
| 5-HT2C (EC50) [nM]b | 11 | 35 |
| 5-HT2B (EC50) [nM] / Emax [%]b/c | 2037 / 58 | >10000 |
| 5-HT2A (EC50) [nM] / Emax [%]b/c | 1881 / 50 | >10000 |
| 5-HT1B (IC50) [nM]c | >10000 | >10000 |
a For the salt form you will get, please refer to the label on the vial and for the molecular weight of the salt, please refer to the FAQs
b Agonism was monitored in whole cells by measuring the Ca2+ release using the Fluorimetric Imaging Plate Reader (FLIPR) using the FLIPR Calcium 3 no-wash assay kit (Molecular Devices). More details are available in our Bioorg. Med. Chem. Lett. publication1. Additional information can be obtained via the “Contact us” formular.
c Color code: green = selective compound; yellow = weak agonist.
BI-4752 and BI-3234 possess a good solubility and a moderate permeability. They display only minimal cytochrome and hERG inhibition.
| PROBE NAME / CONTROL MOLECULE | BI-4752 | BI-3234 |
| logD @ pH 7.4 | 0.4 | 0.3 |
| Solubility @ pH 6.8 [µg/mL] | >1000 | >87 |
| Caco-2 permeability AB @ pH 7.4 [*10-6 cm/s] | 0.3 | 1.4 |
| Caco-2 efflux ratio | 13 | 28 |
| hERG [inh. % @ 10 µM] | 20 | 32 |
| hERG (IC50) [µM] | 71 | n.d. |
| CYP 3A4 (IC50) [µM] | >50 | >50 |
| CYP 2D6 (IC50) [µM] | >50 | 5 |
| t1/2 human / rat liver microsomes [min] | >60 / >60 | >60 / 55 |
BI-4752 possesses good PK profiles in micea and ratsb. BI-3234 possesses a good PK profile in ratb, with good bioavailability.
MOLECULE / PROPERTIES | MOUSE | RAT | RAT |
| Clearance [% QH] | 36 | 83 | 17.5 |
| Mean residence time after i.v. dose [h] | 1.80 | 3.80 | 2.0 |
| tmax [h] | 1.67 | 1.41 | 0.50 |
| Cmax [nM] | 29 | 92 | 66.90 |
| F [%] | 14 | 87 | 37 |
| Vss [L/kg] | 3.5 | 13 | 3.0 |
a Mouse doses: 6 μmol/kg i.v.; 25 μmol/kg p.o. The i.v. formulation contained a 0.9% NaCl solution; the oral formulation was a standard natrosol solution, acidified with 0.1 N HCl to pH 7.
b Rat doses: 6 μmol/kg i.v.; 25 μmol/kg p.o. The i.v. formulation contained a 0.9% NaCl solution; the oral formulation was a standard natrosol solution, acidified with 0.1 N HCl to pH 7.
Our current in vivo data for both compounds come from diabetes research. The daily food intake of diabetic db/db mice was reduced upon administration of both BI-4752 and BI-3234 (100 mg/kg) (Figure 4a). The body weight decreased over the 28 days period (Figure 4b). It is worth noting that despite the high dose (100 mg/kg), the compound was well tolerated over 28 days. These first two pre-clinical results confirmed our hypothesis that signaling via the 5-HT2c receptor might play a role in body weight regulation. When we tested the effect of those compounds on glycemic control as measured by HbA1c levels (Figure 4c), we only observed a decrease in mice treated with BI-4752 (-1.1%). When mice were treated with BI-3234, no significant HbA1c lowering was observed.
in vivo study in db/db mice. a) Daily food intake; b) Body weight development over 28 days; c) Glucose lowering on day 28 (as assessed by HbA1c measurement).
BI-3234 is offered as an active control compound. It is structurally closely related to BI-4752, also a potent 5-HT2C agonist (EC50 = 35 nM), and selective against the 5-HT2B and 5-HT2A receptors. It is therefore not suitable as an in vitro negative control. Unlike BI-4752 however, BI-3234 did not improve glucose control after 28 days treatment in a murine model (100 mg/kg, bid), and can therefore be used as a control molecule for in vivo experiments.
BI-3234 which serves as a control molecule for in vivo experiments
BI-4752 inhibits the 5-HT1B receptor in the low micromolar range (Ki = 0.75 µM) but was found to be selective against a panel of GPCRs. BI-3234 inhibits the 5HT2B (Ki = 1.14 µM) and 5-HT1B (Ki = 0.75 µM) receptors in the low micromolar range but was found to be selective against a panel of GPCRs.
| SELECTIVITY DATA AVAILABLE | BI-4752 | BI-3234 |
SafetyScreen44™ with kind support of  | Yes | Yes |
| Invitrogen® | No | No |
| DiscoverX® | No | No |
| Dundee | No | No |
Download selectivity data:
BI-4752_selectivityData.xlsx
BI-3234_selectivityData.xlsx
lorcaserin (APD356), sibutramine
BI-4752 and BI-3234 are 5-HT2C receptor agonists with good in vitro potency (EC50 5-HT2C = 11 nM and 35 nM, respectively) and excellent selectivity against 5-HT2a and 5-HT2b. They have different in vivo properties and hence, represent good tools to study 5-HT2c receptor molecular signaling.
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Tye H., Mueller S. G., Prestle J., Scheuerer S., Schindler M., Nosse B., Prevost N., Brown C. J., Heifetz A., Moeller C., Pedret-Dunn A., Whittaker M.
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Smith B. M., Smith J. M., Tsai J. H., Schultz J. A., Gilson C. A., Estrada S. A., Chen R. R., Park D. M., Prieto E. B., Gallardo C. S., Sengupta D., Dosa P. I., Covel J. A., Ren A., Webb R. R., Beeley N. R., Martin M., Morgan M., Espitia S., Saldana H. R., Bjenning C., Whelan K. T., Grottick A. J., Menzaghi F., Thomsen W. J.
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Cell 2018, 172, 719-730.
When you plan a publication, please use the following acknowledgement:
BI-4752 and BI-3234 was kindly provided by Boehringer Ingelheim via its open innovation platform opnMe, available at https://www.opnme.com.