Bexicaserin

CAS 2035818-24-5

Formula	C15H19F2N3O
Molar mass	295.334 g·mol−1

(3R)-N-(2,2-difluoroethyl)-3-methyl-1,10-diazatricyclo[6.4.1.0^4,13]trideca-4,6,8(13)-triene-5-carboxamide

• (3R)-N-(2,2-difluoroethyl)-3-methyl-1,10-diazatricyclo[6.4.1.04,13]trideca-4,6,8(13)-triene-5-carboxamide
• (7R)-N-(2,2-difluoroethyl)-7-methyl-1,2,3,4,6,7-hexahydro[1,4]diazepino[6,7,1-hi]indole-8-carboxamide
• Pyrrolo[3,2,1-jk][1,4]benzodiazepine-8-carboxamide, N-(2,2-difluoroethyl)-1,2,3,4,6,7-hexahydro-7-methyl-, (7R)-

Bexicaserin is under investigation in clinical trial NCT05626634 (Open-label, Long-term Safety Study of LP352 in Subjects With Developmental and Epileptic Encephalopathy).

PATENT

Arena Pharmaceuticals, Inc.WO2023172685 

Arena Pharmaceuticals, Inc., WO2016176177

https://patents.google.com/patent/WO2016176177A1/en

Example 1: Syntheses of Compounds of Table A Example 1.1: Preparation of N-(2,2-difluoroethyl)-7-methyl-l,2,3,4,6,7-hexahydro- [l,4]diazepino[6,7,l-hi]indole-8-carboxamide (Compound 1)

Step A: Preparation of methyl 3-formyl-lH-indole-4-carboxylate

2M solution of oxalyl dichloride in dichloromethane (DCM) (1.712 ml, 3.425 mmol) was added to DCM (15 mL) cooled down in an ice-water bath. N,N-dimethylformamide (0.250 g, 3.425 mmol) was added dropwise under nitrogen. The reaction mixture was stirred at 0 °C for 30 min. Then methyl lH-indole-4-carboxylate (0.5 g, 2.854 mmol) in DCM (10 mL) was added. The reaction mixture was warmed to room temperature and stirred for 1 h. The solvent was removed. THF (15 mL) and 20% aqueous ammonium acetate were added. The reaction mixture was stirred under reflux (-70 °C) for 30 min. The reaction mixture was then extracted with ethyl acetate. The combined organics (organic phases) were concentrated; the residue was purified by silica gel column chromatography with 90% ethyl acetate/hexanes to give the title compound (551 mg, 95.0 %) as white solid. LCMS m/z = 204.2 [M+H]⁺; Ή NMR (400 MHz, CDC1₃) δ ppm 4.00 (s, 3H), 7.34 (t, / = 7.8 Hz, 1H), 7.63 (dd, / = 8.0 and 1.0 Hz, 1H), 7.87 (dd, / = 7.5 and 1.0 Hz, 1H), 8.10 (d, / = 3.2 Hz, 1H), 9.08 (br s, 1H), 10.53 (s, 1H).

Step B: Preparation of methyl 3-methyl-lH-indole-4-carboxylate

To a stirred solution of methyl 3-formyl-lH-indole-4-carboxylate (551 mg, 2.712 mmol) in DMF (8 mL) was added 4-methylbenzenesulfonohydrazide (0.657 g, 3.525 mmol) followed by p- toluenesulfonic acid monohydrate (77.37 mg, 0.407 mmol) and tetramethylene sulfone (sulfolane, 8 mL). The reaction mixture was stirred at 100 °C for 1 h, cooled to room temperature. Sodium cyanoborohydride (0.682 g, 10.85 mmol) was added portionwise. Then the mixture was stirred at 100 °C for 2 h. The reaction mixture was cooled down, diluted with water, and extracted with 50% ethyl acetate in hexanes. The organics were concentrated; the residue was purified by silica gel column chromatography with 20% ethyl acetate hexanes to give the title compound (355 mg, 69.2 %) as off- white solid. LCMS m/z = 190.4 [M+H]⁺; Ή NMR (400 MHz, CDC1₃) δ ppm 2.41 (d, / = 1.0 Hz, 3H), 3.96 (s, 3H), 7.07-7.10 (m, 1H), 7.18 (t, / = 7.8 Hz, 1H), 7.50 (dd, / = 8.0 and 1.0 Hz, 1H), 7.64 (dd, J = 7.5 and 1.0 Hz, 1H), 8.12 (bs, 1H).

Step C: Preparation of methyl 3-methylindoline-4-carboxylate

To a solution of methyl 3-methyl-lH-indole-4-carboxylate (1.253 g, 6.622 mmol) in TFA (trifluoroacetic acid) (4.06 mL) in an ice-water bath was added triethylsilane (4.231 ml, 26.49 mmol) drop wise under N₂. The reaction mixture was warmed to room temperature and stirred overnight. The mixture was concentrated and added water. After adjusting pH to 8 with saturated aqueous NaHC0₃ solution, the mixture was extracted with ethyl acetate. The combined organics were concentrated. The residue was purified by silica gel column chromatography with 25% ethyl acetate/hexanes (column prewashed with 0.1% Et₃N/hexanes) to give the title compound (1.013 g, 80.0 %) as orange-red oil. LCMS m/z = 192.2 [M+H]⁺; Ή NMR (400 MHz, CDC1₃) δ ppm 1.25 (d, J = 6.9 Hz, 3H), 3.25 (dd, J = 8.6 and 1.7 Hz, 1H), 3.68 (t, / = 8.5 Hz, 1H), 3.83-3.92 (m, 1H), 3.90 (s, 3H), 6.78 (dd, / = 7.8 and 1.0 Hz, 1H), 7.07 (t, / = 7.8 Hz, 1H), 7.34 (dd, / = 7.8 and 1.0 Hz, 1H).

Step D: Preparation of 2-tert-butyl 8-methyl 7-methyl-3,4,6,7-tetrahydro- [l,4]diazepino[6,7,l-hi]indole-2,8(lH)-dicarboxylate

A mixture of methyl 3-methylindoline-4-carboxylate (1.013 g, 5.297 mmol) and 2- bromoethanamine hydrobromide (1.302 g, 6.357 mmol) was heated at 115 °C overnight. The residue was dissolved in methanol and purified by preparative HPLC (5-60% CH₃CN/H₂0 with 0.1% TFA over 30 min). The combined fractions were then concentrated to give methyl l-(2-aminoethyl)-3- methylindoline-4-carboxylate. LCMS m/z = 235.4 [M+H]⁺; Ή NMR (400 MHz, CDC1₃) δ ppm 1.24 (d, / = 7.0 Hz, 3H), 2.92-3.00 (m, 3H), 3.25 (dd, / = 8.5 and 1.7 Hz, 1H), 3.30-3.40 (m, 2H), 3.80-3.90 (m, 1H), 3.88 (s, 3H), 6.64 (d, / = 7.7 Hz, 1H), 7.11 (t, / = 7.8 Hz, 1H), 7.27 (dd, / = 7.9 and 0.8 Hz, 1H).

Methyl l-(2-aminoethyl)-3-methylindoline-4-carboxylate obtained above was dissolved in methanol (10 mL), 37% formaldehyde in water (1.183 ml, 15.89 mmol) was added, followed by TFA (1.217 ml, 15.89 mmol). The reaction mixture was heated at 80 °C for lh and concentrated. The residue was dissolved in THF (8 mL), and added saturated aqueous NaHC0₃ (8 mL) solution and di-tert-butyl dicarbonate (0.776 ml, 5.297 mmol). The reaction mixture was stirred at room temperature overnight, diluted with water, and extracted with ethyl acetate. The combined organics were concentrated. The residue was purified by silica gel column chromatography with 25% ethyl acetate/hexanes to give the title compound (1.212 g, 66.0 %) as colorless oil. LCMS m/z = 347.2 [M+H]⁺; Ή NMR (400 MHz, CDC1₃) δ ppm rotamers 1.20 (d, / = 6.9 Hz, 3H), 1.35-1.45 (br, 9H), 2.80-2.95 (m, 1H), 3.08-3.18 (m,lH), 3.24-3.35 (m, 2H), 3.35-3.45 (m, 1H), 3.85-3.95 (m, 1H), 3.86 (s, 3H), 3.97-4.08 (m, 2H), 4.62-4.88 (m, 1H), 6.91-7.06 (m, 1H), 7.36 (d, J = 8.0 Hz, 1H).

Step E: Preparation of 2-(tert-butoxycarbonyl)-7-methyl-l,2,3,4,6,7-hexahydro- [l,4]diazepino[6,7,l-hi]indole-8-carboxylic acid

To a solution of 2-tert-butyl 8-methyl 7-methyl-3,4,6,7-tetrahydro-[l,4]diazepino[6,7,l- hi]indole-2,8(lH)-dicarboxylate (1.212 g, 3.499 mmol) in dioxane (10 mL) was added a 1M solution of lithium hydroxide in water (13.99 ml, 13.99 mmol). The reaction mixture was stirred at 80 °C for 2 h. Organic solvent was evaporated. The residue was diluted with water, adjusted pH to 3-4 with aqueous 5% citric acid. The off-white precipitate was collected and dried to give the title compound (1.116 g, 96.0 %) as off-white solid. LCMS m/z = 333.4 [M+H]⁺.

Step F: Preparation of N-(2,2-difluoroethyl)-7-methyl-l,2,3,4,6,7-hexahydro- [l,4]diazepino[6,7,l-hi]indole-8-carboxamide

To the solution of 2-(tert-butoxycarbonyl)-7-methyl- 1,2, 3,4,6, 7-hexahydro- [l,4]diazepino[6,7,l-hi]indole-8-carboxylic acid (25 mg, 75.21 μιηοΐ), HATU (42.87 mg, 0.113 mmol) and triethylamine (20.97 μί, 0.150 mmol) in DMF (2 mL) was added 2,2-difluoroethanamine (9.146 mg, 0.113 mmol). The reaction was stirred at room temperature overnight. The mixture was purified by semi preparative HPLC (15-85% CH₃CN/H₂0 with 0.1% TFA over 30 min). The combined fractions were lyophilized to give tert-butyl 8-((2,2-difluoroethyl)carbamoyl)-7-methyl-3,4,6,7-tetrahydro- [l,4]diazepino[6,7,l-hi]indole-2(lH)-carboxylate, which was dissolved in dioxane (0.5 mL). A solution of 4M HC1 in dioxane (0.5 mL) was added. The reaction mixture was stirred at room temperature for 4 h and concentrated. The residue was purified by semi preparative HPLC (5-60% CH₃CN/H₂0 with 0.1% TFA over 30 min). The combined fractions were lyophilized to give the title compound as TFA salt (17 mg, 55.2 %). LCMS m z = 296.2 [M+H]⁺; Ή NMR (400 MHz, CD₃OD) δ ppm 1.18 (d, / = 6.9 Hz, 3H), 3.10-3.20 (m, 1H), 3.26-3.40 (m, 2H), 3.40-3.64 (m, 3H), 3.65-3.85 (m, 3H), 4.21 (d, / = 14.9 Hz, 1H), 4.40 (d, J = 14.9 Hz, 1H), 6.00 (tt, J = 56.0 and 3.9 Hz, 1H), 6.99 (d, J = 7.8 Hz, 1H), 7.12 (d, / = 7.9 Hz, 1H).

Example 1.2: Preparation of (S)- N-(2,2-difluoroethyl)-7-methyl-l,2,3,4,6,7-hexahydro- [l,4]diazepino[6,7,l-hi]indole-8-carboxamide (Compound 2) and (R)- N-(2,2-difluoroethyl)-7- methyl-l,2,3,4,6,7-hexahydro-[l,4]diazepino[6,7,l-hi]indole-8-carboxamide (Compound 3)

Enantiomers of N-(2,2-difluoroethyl)-7-methyl- 1,2,3, 4,6, 7-hexahydro-[l, 4]diazepino[6,7,l-hi]indole-8- carboxamide were obtained by chiral HPLC separation using following conditions. Column: Chiralpak IC column 250 x 20 mm (L x I.D.)

Flow: 12 mL/min

Eluent: 12 % ethanol/8 % mTBE/80 % hexanes with 0.1 % Et₃N

Detector: UV 254 nm

Retention time: 1^st eluting enantiomer 22.0 min, 2^nd eluting enantiomer 23.5 min

After separation, both enantiomers were further purified by semi preparative HPLC (5-60%

CH₃CN/H₂0 with 0.1% TFA (trifluoroacetic acid) over 30 min). The combined fractions were lyophilized to give the title compounds as the TFA salt.

SCHEME

Bexicaserin (INNTooltip International Nonproprietary Name; developmental code names LP352 and AN352) is a selective serotonin 5-HT_2C receptor agonist which is under development for the treatment of seizures in developmental disabilities such as Dravet syndrome and Lennox-Gastaut syndrome.^[1][3][2] It is taken by mouth.^[2][1]

The drug is highly selective for the serotonin 5-HT_2C receptor, with negligible affinity for the serotonin 5-HT_2A and 5-HT_2B receptors.^[2] Because it does not activate the serotonin 5-HT_2B receptor, bexicaserin is not expected to pose a risk of cardiac valvulopathy, unlike the existing agent fenfluramine.^[2]

As of October 2024, bexicaserin is in phase 3 clinical trials for treatment of developmental disabilities.^[1][3] It is being developed by Longboard Pharmaceuticals.^[1][3]

The activation of 5HT2c receptors has been shown to reduce epileptic seizure activity by inhibiting CaV3 calcium channels which mediate the T-type calcium current.^[4] CaV3 calcium channels facilitate high frequency burst firing in princible neurons of the subiculum. This firing pattern is upregulated following status epilepticus, with these hyperactive neurons often serving as the initiation point for seizures.^[5][6][7]

References

1. ^ Jump up to:^{a b c d e f} “Bexicaserin – Longboard Pharmaceuticals”. AdisInsight. 16 October 2024. Retrieved 29 October 2024.
2. ^ Jump up to:^{a b c d e f} Dell’isola GB, Verrotti A, Sciaccaluga M, Roberti R, Parnetti L, Russo E, et al. (June 2024). “Evaluating bexicaserin for the treatment of developmental epileptic encephalopathies”. Expert Opinion on Pharmacotherapy. 25 (9): 1121–1130. doi:10.1080/14656566.2024.2373350. PMID 38916481.
3. ^ Jump up to:^a b c “Delving into the Latest Updates on Bexicaserin with Synapse”. Synapse. 28 October 2024. Retrieved 29 October 2024.
4. ^ Petersen AV, Jensen CS, Crépel V, Falkerslev M, Perrier JF (2017). “Serotonin Regulates the Firing of Principal Cells of the Subiculum by Inhibiting a T-type Ca2+ Current”. Frontiers in Cellular Neuroscience. 11: 60. doi:10.3389/fncel.2017.00060. PMC 5339341. PMID 28326015.
5. ^ Menendez de la Prida L, Gal B (June 2004). “Synaptic contributions to focal and widespread spatiotemporal dynamics in the isolated rat subiculum in vitro”. The Journal of Neuroscience. 24 (24): 5525–36. doi:10.1523/JNEUROSCI.0309-04.2004. PMC 6729319. PMID 15201325.
6. ^ Su H, Sochivko D, Becker A, Chen J, Jiang Y, Yaari Y, et al. (May 2002). “Upregulation of a T-type Ca2+ channel causes a long-lasting modification of neuronal firing mode after status epilepticus”. The Journal of Neuroscience. 22 (9): 3645–55. doi:10.1523/JNEUROSCI.22-09-03645.2002. PMC 6758371. PMID 11978840.
7. ^ Cohen I, Navarro V, Clemenceau S, Baulac M, Miles R. On the origin of interictal activity in human temporal lobe epilepsy in vitro. Science. 2002 Nov 15;298(5597):1418-21. doi: 10.1126/science.1076510. PMID 12434059.

Clinical data
Other names	LP352; LP-352; AN352; AN-352
Routes of administration	Oral[1]
Drug class	Serotonin 5-HT2C receptor agonist[1][2]
Pharmacokinetic data
Elimination half-life	5–7 hours[2]
Identifiers
showIUPAC name
CAS Number	2035818-24-5
PubChem CID	122662787
DrugBank	DB18885
ChemSpider	129309383
UNII	R8XR1D6SCB
KEGG	D13035
ChEMBL	ChEMBL5314507
Chemical and physical data
Formula	C15H19F2N3O
Molar mass	295.334 g·mol−1
3D model (JSmol)	Interactive image
showSMILES
showInChI

////Bexicaserin, PHASE 2, LP 352, LP-352, AN 352, AN-352