S 38093 is a novel brain-penetrant antagonist (inverse agonist) of the H3 (histamine H3) receptor with Ki of 8.8, 1.44 and 1.2 µM for rat, mouse and human H3 receptors, respectively. It might offer a novel approach to addressing age-related cognitive impairments. S 38093 can suppress cAMP decrease induced by an H3 agonist via human H3 receptors (KB=0.11 µM) and antagonize mice H3 receptors (KB=0.65 µM) in cellular models. S 38093 acts as a moderate inverse agonist at rat and human H3 receptors (EC50=9 and 1.7 µM, respectively) in cells expressing a high density of H3. S 38093 is a promising candidate for additional in vivo testing as a novel H3 inverse agonist, especially in animal models of cognition.

Physicochemical Properties

Molecular Formula	C17H24N2O2
Molecular Weight	288.384664535522
Exact Mass	288.18
Elemental Analysis	C, 70.80; H, 8.39; N, 9.71; O, 11.10
CAS #	862896-30-8
Related CAS #	S 38093 hydrochloride; 1222097-72-4
PubChem CID	11380684
Appearance	White to off-white solid powder
LogP	2.5
Hydrogen Bond Donor Count	1
Hydrogen Bond Acceptor Count	3
Rotatable Bond Count	6
Heavy Atom Count	21
Complexity	341
Defined Atom Stereocenter Count	0
InChi Key	MRNMYWNBLVJWKG-UHFFFAOYSA-N
InChi Code	InChI=1S/C17H24N2O2/c18-17(20)13-5-7-16(8-6-13)21-10-2-9-19-11-14-3-1-4-15(14)12-19/h5-8,14-15H,1-4,9-12H2,(H2,18,20)
Chemical Name	4-[3-(3,3a,4,5,6,6a-hexahydro-1H-cyclopenta[c]pyrrol-2-yl)propoxy]benzamide
Synonyms	S38093; S-38093; S 38093
HS Tariff Code	2934.99.9001
Storage	Powder-20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month
Shipping Condition	Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Biological Activity

Targets	Rat H3 receptor ( Ki = 8.8 µM ); Mouse H3 receptor ( Ki = 1.44 µM ); Human H3 receptor ( Ki = 1.2 µM )
ln Vitro	In vitro activity: S 38093 can suppress cAMP decrease induced by an H3 agonist via human H3 receptors (KB=0.11 µM) and antagonize mice H3 receptors (KB=0.65 µM) in cellular models. S 38093 acts as a moderate inverse agonist at rat and human H3 receptors (EC50=9 and 1.7 µM, respectively) in cells expressing a high density of H3[2].
ln Vivo	S 38093 dramatically boosts the proliferation of progenitors in the DG of the hippocampal region in young adult mice (0.3 and 3 mg/kg/d p.o., 28 days). Treatment with S 38093 (0.3 mg/kg/d) dramatically increases the proportion of DCX+ cells with tertiary dendrites. In the DG of the hippocampal DG of aged mice, S 38093 (0.3, 1 and/or 3 mg/kg) significantly increases cell proliferation, survival, and maturation in comparison to vehicle. A one-way ANOVA with repeated measure revealed that S 38093 (3 mg/kg/d p.o., 28 days) increases dendritic intersections in both genotypes and has a strong effect on cell survival. In APPSWETG mice only, this effect is significant from 50 to 80. Chronic administration of S 38093 (1 and/or 3 mg/kg/day p.o., 28 days) in aged mice reverses this age-dependent decrease in transcripts of BDNF-IX, BDNF-IV, and BDNF-I. Furthermore, compared to the vehicle-aged group, S 38093 increases VEGF transcripts at three tested doses (0.3, 1 and 3 mg/kg/d)[1]. S 38093 considerably reduces R-α-Methylhistamine-induced dipsogenia in mice from 10 mg/kg i.p. and raises ex vivo N-tele-Methylhistamine cerebral levels from 3 mg/kg p.o.[2].
Enzyme Assay	S 38093 is a new type of inverse agonist that selectively blocks the H3 (histamine H3) receptor in the brain. Its Ki values for rat, mouse, and human H3 receptors are 8.8, 1.44, and 1.2 µM, respectively.
Cell Assay	After being harvested at a density of 2 x 106 cells per milliliter, the cells were suspended in Hank's balanced salt solutions/HEPES (pH7.4) buffer, which contained 1 mM isobutyl-methylxanthine and 1 mg/ml BSA. After adding 1 μl of the fluor 647-anti-cAMP antibody solution to 100 μl of the cell suspension, 6 μl aliquots of the mixture were put into white 384-well microtiter plates. Then, in order to preactivate adenylate cyclase, the cells were incubated with 6 μl aliquots of S 38093 and/or the reference compounds (specific H3 agonist Imetit or antagonist Thioperamide) at increasing concentrations (0.01-100 μM), in the presence of forskolin (FSK, 0.5 μM final concentration). The cells were treated with the lysis buffer (0.35% Triton X-100, 10mM CaCl2, 50mM HEPES) containing LANCE EU-W8044 labeled streptavidin and biotinyled cAMP after a one-hour incubation period at room temperature in the dark. Plates were read on a microplate reader following a 20-hour dark incubation period at +4°C.
Animal Protocol	The mice are required to learn to discriminate between a frightening shock context and a comparable non-shock context over the course of an eight-day contextual fear discrimination paradigm. The mice are exposed to the training shock context exclusively on day 1, and then every day from days 2 through 8, they are exposed to the shock and non-shock context in that order. Every day at 4 pm, the mice are gavaged with either S 38093 or the vehicle after completing the context discrimination task, which runs from 10 am to 2 pm. To prevent any potential acute behavioral effects, behavioral testing is always conducted prior to administering the drug and vehicle. The percentage of time the mice spent freezing is used to measure learning, and testing is stopped when the percentage of freezing consistently differs significantly between the two contexts. Following a 29-day drug regimen, the mice are tested. One side of a Med-Associates shuttle box (ENV-010MC; 20.3 cm × 15.9 cm × 21.3 cm high) with a clear plexiglass wall, three aluminum walls, and a stainless steel grid as a floor is used for conditioning. Digital cameras positioned above the conditioning chamber capture mouse behavior. The software programs Freezeframe and Freezeview are used to record and analyze freezing behavior, respectively. Mice in training context A are first brought into the room in their new cages after being given time to acclimate in new ones outside of it. The plexiglass wall is up, the stainless steel grid is visible, the house fan and light are on, and a light anise fragrance is employed as an olfactory cue. Throughout the trial, the door to the sound-dampening enclosure is closed. A single foot shock of 0.75 mA is given to the mice 180 s after they are placed in the training context, lasting 2 s. The mice are returned to their original cages fifteen seconds after the footshock stops. In the interim between trials, the grids and catch trays are cleaned with non-alcoholic antiseptic wipes. An hour later, the mice are placed in context B and brought into the room in paper buckets. The plexiglass wall is left down, the plastic placemat sheets are placed inside the shuttle box to create a high-walled circular enclosure, the house fan and light are turned off, and a light lemon scent is employed as the olfactory cue. One prominent element in both settings, the stainless steel grid, was left exposed. The mice are returned to their original cages after spending 180 seconds in the chambers without experiencing a foot shock. In between trials, the grids and catch trays are cleaned with 70% ethanol. The discrimination ratio, which is calculated as follows: A = freezing in context A, B = freezing in context B, and the discrimination ratio = A/(A + B), allowed for the evaluation of discrimination between the two contexts. Greater discrimination is indicated by larger values.
References	[1]. S 38093, a histamine H3 antagonist/inverse agonist, promotes hippocampal neurogenesis and improves context discrimination task in aged mice. Sci Rep. 2017 Feb 20;7:42946. [2]. Mechanistic characterization of S 38093, a novel inverse agonist at histamine H3 receptors. Eur J Pharmacol. 2017 May 15;803:11-23.

Solubility Data

Solubility (In Vitro)

DMSO: 2~57 mg/mL (6.9~197.7 mM) Water: <1 mg/mL Ethanol: ~57 mg/mL (~197.7 mM)

Solubility (In Vivo)

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples. Injection Formulations (e.g. IP/IV/IM/SC) Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline) *Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution. Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline) Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil) Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals). Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)] *Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution. Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline) Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline) Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline) Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil) Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline) Oral Formulations Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium) Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals). Oral Formulation 3: Dissolved in PEG400 Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose Oral Formulation 6: Mixing with food powders Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.  (Please use freshly prepared in vivo formulations for optimal results.)

Preparing Stock Solutions		1 mg	5 mg	10 mg
	1 mM	3.4676 mL	17.3382 mL	34.6765 mL
	5 mM	0.6935 mL	3.4676 mL	6.9353 mL
	10 mM	0.3468 mL	1.7338 mL	3.4676 mL

*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.