Patent Description:
Vasoconstriction related disorder comprise a group of disorders, like for example pulmonary hypertension, portal hypertension, vasospastic diseases, Raynaud's disease, acrocyanosis, livedo reticularis, post-traumatic dystrophy, occlusive diseases associated with inflammation and Buerger's disease.

Vasoconstriction is the process of constriction of blood vessels, which may result in decrease of flow of blood. Normal blood flow is necessary for carrying oxygenated blood to all parts of the body and when the normal flow is disrupted it may cause various problems. Vasoconstriction can occur due to medical condition or due to psychological disorder. This condition happens when the small muscles of the walls constrict causing narrowing of blood vessels. Actually this process is exactly opposite condition of vaso-dilation in which the blood vessels enlarge or open widely. The contraction of blood vessels can increase the heat of the body and may cause vascular conflict. Following this condition, the skin becomes paler than before since blood supply is drastically reduced. It occurs mostly on large arteries thus obstructing the blood flow but sometimes it can develop on small arterioles causing constriction of blood vessels.

An alpha adrenoreceptor antagonist (which is a vasodilator) can be administered for reducing the constriction of blood vessels and increasing blood flow. Treating the problem with calcium channel blockers would facilitate widening of blood vessels.

Control of hypertension in the vascular patient is clearly a priority. However, these patients often will have significant co-morbidities that may influence the choice of medication. The <NUM> main categories of drugs used in the initial treatment of hypertensive vascular diseases are (<NUM>). diuretics, (<NUM>). beta-adrenergic blockers, (<NUM>). calcium channel blockers, (<NUM>). angiotensin-converting enzyme (ACE) inhibitors, and (<NUM>). angiotensin receptor blockers (ARBs). Each of the antihypertensive agents is roughly equally effective, producing a good antihypertensive response in <NUM>% to <NUM>% of cases. Some antihypertensives, especially ACE and ARBs, also may have beneficial effects on the vascular and metabolic systems separate from their blood pressure lowering effects, which suggests they may be beneficial even if blood pressure is well maintained with other agents. However, there remains a need for new compounds for treatment of vasoconstriction related disorders, in particular ones that have less side effects, or preferably no side effects at all in the dosing range of such compound.

It is an object of the present invention to provide compounds for the treatment of vasoconstriction related disorders or conditions.

The above object is met by the present invention by the (2R) enantiomeric form of a <NUM>-chromanol derivative for use in the treatment of vasoconstriction related disorders or conditions as defined in the claims.

Certain chromanol compounds have been described in e.g. <CIT>, <CIT> and <CIT>. These compounds show a wide variety of protective effects on cells and organs. The compounds described in detail are developed by Sulfateq, and have abbreviations, referring to SUL-XXX (XXX being a <NUM> or <NUM> digit number). Many of these compounds are racemic mixtures, although some enantiomers have been tested as well. <CIT> relates SUL compounds for the protection of cells, in particular for protection of cells during storage. <CIT> relates to SUL compounds for use in the prophylaxis or treatment of organ damage by restoring endothelial function and/or inhibiting reactive oxygen species production and especially to compounds for prophylaxis or treatment of diabetic kidney damage.

Unexpectedly, upon further research, a number of the SUL compounds showed reversal effects of vascular constriction, which effect is useful in the treatment of vasoconstriction related disorders.

Thus, the present invention relates to the (2R) enantiomeric form of a <NUM>-chromanol derivative wherein the <NUM>-chromanol derivative is (R)(<NUM>-hydroxy-<NUM>,<NUM>,<NUM>,<NUM>-tetramethylchroman-<NUM>-yl)(piperazin-<NUM>-yl)methanone and pharmaceutically acceptable salts thereof.

According to yet another preferred embodiment, the present invention relates to the (R) enantiomeric form of a <NUM>-chromanol derivative as described, wherein the vasoconstriction related disorder is selected from the group consisting of pulmonary hypertension, portal hypertension, vasospastic diseases, Raynaud's disease, acrocyanosis, livedo reticularis, post-traumatic dystrophy, (pre)eclampsia, and Buerger's disease. Pulmonary hypertension in particular relates to pulmonary arterial hypertension, for which the present invention is preferred. Another disorder that can be treated with the described compounds is cardiac hypertrophy and fibrosis.

The vasoconstriction disorder particularly relates to α1 adrenoceptor mediated disorders, such as pulmonary arterial hypertension and cardiac hypertrophy and fibrosis.

Another indication which is preferably treated with the compound of the present invention is heart failure with preserved ejection fraction (HFpEF), in which hypertension generally is co-indicated.

In a preferred embodiment, the vasoconstrictive disorder has a co-indication of inflammation. As the chromanol compound is effective as anti-inflammatory agent, the use of said chromanol compound is very effective in the prophylaxis or treatment of vasoconstrictive and inflammation related disorders, such as pulmonary hypertension, portal hypertension and (pre)eclampsia.

SUL-<NUM> is a <NUM>:<NUM> racemic mixture of two enantiomers (S enantiomer named SUL-<NUM>, R enantiomer named SUL-<NUM>). The effects of SUL-<NUM> and SUL-<NUM> on phenylephrine (PE) -induced vascular constrictions were investigated. The results showed that whereas SUL-<NUM> exerted a dose-dependent increase of EC50, whereas no significant effects after treatment with SUL-<NUM> were observed. The SUL-<NUM> was able to inhibit or counteract the induced vascular constrictions.

According to a preferred embodiment, the present invention relates to the (R) enantiomeric form of a <NUM>-chromanol derivative, wherein said prophylaxis or treatment of vasoconstriction related disorders or conditions is mediated by inhibition of the α1 adrenoceptor. α<NUM> adrenoceptors are coupled with the G-protein (GPRC), specifically Gq and G<NUM> subtypes. Their activation leads to a downstream activation of phospholipase pathways, increase of (Ca<NUM>+)i and a subsequent constriction of the vascular smooth muscle. Additionally, we have demonstrated the ability of α<NUM> adrenoceptors to trans-activate the Epidermal Growth Factor Receptor (EGFR) which contributes to downstream phosphorylation of extracellular signal-regulated kinases <NUM> and <NUM>. The inhibition of EGFR attenuated constriction responses to PE in isolated rat aortas. Therefore, we investigate the effects of SUL-<NUM> on the mechanism of EGFR transactivation by α1 adrenoceptors.

It was found that the mechanism through which SUL-<NUM> inhibits vasoconstriction is via direct interaction with the α<NUM> adrenoceptor as a receptor antagonist. SUL-<NUM> did not affect calcium transients in any of the investigated α<NUM> adrenoceptor subtypes. Results indicate that SUL-<NUM> is capable of counteracting vascular constriction and intracellular calcium responses specifically via its action on α<NUM> adrenoceptors. Radiolabelled prazosin displacement suggests that SUL-<NUM> competitively binds to the antagonist binding site. Prazosin is an α<NUM>-blocker which acts as an inverse agonist at alpha-<NUM> adrenergic receptors. Compared with prazosin, SUL-<NUM> conveys a range of additional beneficial effects. Combined anti-oxidant, anti-inflammatory and vasodilatory properties of SUL-<NUM> may be applicable in the treatment of diseases related to vasoconstriction, such as Raynaud's disease.

According to preferred embodiment, the present invention relates to the 2R-<NUM>-chromanol derivative, wherein the prophylaxis or treatment of vasoconstriction related disorders or conditions is mediated by inhibition of the α1 adrenoceptor.

The compounds are preferably used in effective amounts, to achieve a vasodilatory effect. Effects are observed with amounts of <NUM>, but preferably higher amounts are used. Preferred amounts are concentrations in vivo or in vitro of about <NUM> or higher, more preferably about <NUM> or higher. Generally, a concentration in human of about <NUM> or lower should be sufficient and safe.

For human use, this would mean - assuming a <NUM> distribution volume, <NUM>% availability and a concentration of about <NUM> - a dosage of about <NUM> or more. Preferred amounts would result in a concentration of about <NUM> - for which a dosage of about <NUM> or more would be suitable. Hence, preferably, dosage forms of about <NUM> or more, preferably <NUM> or more, preferably <NUM> or more are suitable. Generally, solid, oral dosage forms contain as a maximum about <NUM> compound, preferably about <NUM> or less, to allow for excipients. other liquid forms of administration, larger amounts can be administered.

Examples of dosages which can be used are an effective amount of the compound of the invention of a dosage of <NUM>/kg or higher, such as preferably within the range of about <NUM> /kg to about <NUM>/kg, or within about <NUM> /kg to about <NUM>/kg body weight, or within about <NUM>/kg to about <NUM>/kg body weight, or within about <NUM> /kg to about <NUM>/kg body weight. The compound of the present invention may be administered in a single daily dose, or the total daily dosage may be administered in divided dosage of two, three or four times daily.

The compounds described herein can be formulated as pharmaceutical compositions by formulation with additives such as pharmaceutically or physiologically acceptable excipients carriers, and vehicles. Suitable pharmaceutically or physiologically acceptable excipients, carriers and vehicles include processing agents and drug delivery modifiers and enhancers, such as, for example, calcium phosphate, magnesium stearate, talc, monosaccharides, disaccharides, starch, gelatin, cellulose, methyl cellulose, sodium carboxymethyl cellulose, dextrose, hydroxypropyl-P-cyclodextrin, polyvinylpyrrolidinone, low melting waxes, and the like, as well as combinations of any two or more thereof. Other suitable pharmaceutically acceptable excipients are described in "<NPL>), and "<NPL>).

A pharmaceutical composition can comprise a unit dose formulation, where the unit dose is a dose sufficient to have an vasodilatory effect, preferably a vasodilatory therapeutic effect. The unit dose may be a dose administered periodically in a course of treatment or suppression of a vasodilatory disorder.

Pharmaceutical compositions containing the compound of the invention may be in any form suitable for the intended method of administration, including, for example, a solution, a suspension, or an emulsion. Liquid carriers are typically used in preparing solutions, suspensions, and emulsions. Liquid carriers contemplated for use in the practice of the present invention include, for example, water, saline, pharmaceutically acceptable organic solvent(s), pharmaceutically acceptable oils or fats, and the like, as well as mixtures of two or more thereof. The liquid carrier may contain other suitable pharmaceutically acceptable additives such as solubilizers, emulsifiers, nutrients, buffers, preservatives, suspending agents, thickening agents, viscosity regulators, stabilizers, and the like. Suitable organic solvents include, for example, monohydric alcohols, such as ethanol, and polyhydric alcohols, such as glycols. Suitable oils include, for example, soybean oil, coconut oil, olive oil, safflower oil, cottonseed oil, and the like. For parenteral administration, the carrier can also be an oily ester such as ethyl oleate, isopropyl myristate, and the like. Compositions of the present invention may also be in the form of microparticles, microcapsules, liposomal encapsulates, and the like, as well as combinations of any two or more thereof.

Time-release or controlled release delivery systems may be used, such as a diffusion controlled matrix system or an erodible system, as described for example in: <NPL> and <NPL>, in "<NPL>. The matrix may be, for example, a biodegradable material that can degrade spontaneously in situ and in vivo for, example, by hydrolysis or enzymatic cleavage, e.g. , by proteases. The delivery system may be, for example, a naturally occurring or synthetic polymer or copolymer, for example in the form of a hydrogel. Exemplary polymers with cleavable linkages include polyesters, polyorthoesters, polyanhydrides, polysaccharides, poly(phosphoesters), poly amides, polyurethanes, poly(imidocarbonates) and poly(phosphazenes).

The compound of the invention may be administered enterally, orally, parenterally, sublingually, by inhalation (e. as mists or sprays), rectally, or topically in dosage unit formulations containing conventional nontoxic pharmaceutically or physiologically acceptable carriers, adjuvants, and vehicles as desired. For example, suitable modes of administration include oral, subcutaneous, transdermal, transmucosal, iontophoretic, intravenous, intraarterial, intramuscular, intraperitoneal, intranasal (e. via nasal mucosa), subdural, rectal, gastrointestinal, and the like, and directly to a specific or affected organ or tissue. For delivery to the central nervous system, spinal and epidural administration, or administration to cerebral ventricles, can be used. Topical administration may also involve the use of transdermal administration such as transdermal patches or iontophoresis devices. The term parenteral as used herein includes subcutaneous injections, intravenous, intramuscular, intrasternal injection, or infusion techniques. The compounds are mixed with pharmaceutically acceptable carriers, adjuvants, and vehicles appropriate for the desired route of administration.

Oral administration is a preferred route of administration, and formulations suitable for oral administration are preferred formulations.

The compounds described for use herein can be administered in solid form, in liquid form, in aerosol form, or in the form of tablets, pills, powder mixtures, capsules, granules, injectables, creams, solutions, suppositories, enemas, colonic irrigations, emulsions, dispersions, food premixes, and in other suitable forms. The compounds can also be administered in liposome formulations.

Injectable preparations, for example, sterile injectable aqueous or oleaginous suspensions, may be formulated according to the known art using suitable dispersing or wetting agents and suspending agents. The sterile injectable preparation may also be a sterile injectable solution or suspension in a nontoxic parenterally acceptable diluent or solvent, for example, as a solution in propylene glycol. Among the acceptable vehicles and solvents that may be employed are water, Ringer's solution, and isotonic sodium chloride solution. In addition, sterile, fixed oils are conventionally employed as a solvent or suspending medium. For this purpose any bland fixed oil may be employed including synthetic mono- or diglycerides. In addition, fatty acids such as oleic acid find use in the preparation of injectables.

Suppositories for rectal administration of the drug can be prepared by mixing the drug with a suitable nonirritating excipient such as cocoa butter and polyethylene glycols that are solid at room temperature but liquid at the rectal temperature and will therefore melt in the rectum and release the drug.

Solid dosage forms for oral administration may include capsules, tablets, pills, powders, and granules. In such solid dosage forms, the active compound may be admixed with at least one inert diluent such as sucrose, lactose, or starch. Such dosage forms may also comprise additional substances other than inert diluents, e.g., lubricating agents such as magnesium stearate. In the case of capsules, tablets, and pills, the dosage forms may also comprise buffering agents. Tablets and pills can additionally be prepared with enteric coatings.

Liquid dosage forms for oral administration may include pharmaceutically acceptable emulsions, solutions, suspensions, syrups, and elixirs containing inert diluents commonly used in the art, such as water. Such compositions may also comprise adjuvants, such as wetting agents, emulsifying and suspending agents, cyclodextrins, and sweetening, flavoring, and perfuming agents.

Also disclosed are articles of manufacture and kits containing the claimed compound for use in treating, preventing, or suppressing symptoms associated with vasodilatory related conditions or disorders as defined in the claims. The article of manufacture comprises a container with a label. Suitable containers include, for example, bottles, vials, and test tubes. The containers may be formed from a variety of materials such as glass or plastic. The container holds a composition having an active agent which is effective for treating, preventing, or suppressing symptoms associated with a vasodilatory disorder or with a condition associated with vasodilatory dysfunction as defined in the claims. The active agent in the composition is the compound of the invention. The label on the container preferably indicates that the composition is used for treating, preventing, or suppressing symptoms associated with a vasodilatory related disorder or condition as defined in the claims. In a non-claimed aspect, the label may also indicate directions for either in vivo or in vitro use, such as those described above.

Also disclosed are kits comprising the compound of the invention for use as defined in the claims. In some embodiments, the kit of the invention comprises the container described above. In other embodiments, the kit of the invention comprises the container described above and a second container comprising a buffer. It may further include other materials desirable from a commercial and user standpoint, including other buffers, diluents, filters, needles, syringes, and package inserts with instructions for performing any methods described herein.

The amount of active ingredient that may be combined with the carrier materials to produce a single dosage form will vary depending upon the host to which the active ingredient is administered and the particular mode of administration. It will be understood, however, that the specific dose level for any particular patient will depend upon a variety of factors including the activity of the specific compound employed, the age, body weight, body area, body mass index (BMI), general health, sex, diet, time of administration, route of administration, rate of excretion, drug combination, and the type, progression, and severity of the particular disease undergoing therapy or condition to be treated. The unit dosage chosen is usually fabricated and administered to provide a defined final concentration of drug in the blood, tissues, organs, or other targeted region of the body. The effective amount for a given situation can be readily determined by routine experimentation and is within the skill and judgment of the ordinary clinician or skilled person.

The present invention will be further illustrated using the examples below. In the examples, reference is made to figures wherein.

Porcine kidneys were obtained from a local slaughterhouse (Kroon Vlees, Gotenburgweg <NUM>, <NUM> TM Groningen, The Netherlands) and transported on ice in normal physiological Krebs buffer containing <NUM> NaCl, <NUM> KCl, <NUM> CaCl<NUM> × <NUM><NUM>O, <NUM> MgCl<NUM> × <NUM><NUM>O, <NUM> NaH<NUM>PO<NUM> × H<NUM>O, <NUM> NaHCO<NUM> and <NUM> D-(+)-Glucose monohydrate (all ingredients were purchased from Merck) in ultrapure water.

The renal artery tree was dissected from the kidney, cleaned of surrounding connective tissue and cut into equally-sized ring segments (<NUM> in length). In some rings, endothelium denudation was performed by gentle rubbing of the intimal surface with a paper clip. Rings were mounted in organ baths as described previously (Buikema et al. Arterial rings were washed thoroughly by replacing Krebs buffer and allowed to equilibrate for a period of <NUM> under <NUM> of resting tension before they were assessed for viability by inducing <NUM> subsequent constrictions with KCl (<NUM>). Rings that failed to produce a threshold increase in diameter of <NUM> were excluded. After washout and stabilization, rings were treated for <NUM> minutes by incubation with vehicle (<NUM>% DMSO), SUL-<NUM>, SUL-<NUM> or SUL-<NUM>, followed by subsequent incubation with cumulative doses of phenylephrine.

Dose-dependent constriction responses to phenylephrine (<NUM>-<NUM>M - <NUM>-<NUM>M) were recorded in said isolated porcine intrarenal arteries. Buffer was warmed to <NUM> and aerated with <NUM> % O<NUM> and <NUM> % CO<NUM> before use.

CHO-K1 cells were stably transfected with a plasmid containing human α1-AR subtypes A, B and D in separate cell lines in DMEM-F12 medium with <NUM>% FBS, <NUM>% penicillin-streptomycin and 200µg/mL Geneticin (G418, Invitrogen, Carlsbad, CA).

HeLa cells endogenously expressing histamine and TP receptors were grown in DMEM-F12 medium enriched with <NUM>% FBS and <NUM>% penicillin-streptomycin. Cells were kept in a tissue culture incubator at <NUM> in <NUM>% Oz / <NUM>% CO<NUM> atmosphere and grown in <NUM><NUM> non-treated cell culture flasks. Plating was performed <NUM> hours before measurement on black transparent-bottom <NUM>-well plates at <NUM>,<NUM> cells per well density.

On the next day, CHO cells were treated with either vehicle (<NUM>% DMSO) or SUL-<NUM> enantiomers for <NUM> at <NUM> and stimulated with a <NUM>-fold dilution series of PE (<NUM>-100pM). [Ca<NUM>+]i was measured using the fluorescent FLIPR Calcium <NUM> assay kit (Molecular Devices) in immortalized CHO cells stably expressing the α<NUM> adrenoceptor.

Initially, calcium responses induced by non-cumulative concentration series of phenylephrine were investigated using fluorescent measurements in α1A adrenoceptor-overexpressing CHO cells treated with SUL-<NUM> and SUL-<NUM> (<FIG>). Fluorescent measurement data was processed and analyzed in SoftMax Pro <NUM> and expressed as % of baseline AUC with a <NUM>-fold multiplier using an average of first <NUM> measurement points as baseline.

The "Vehicle" used in all experiments is <NUM>% DMSO solution.

Vascular constriction responses are expressed as percentage of final response to KCl. Data are expressed as mean ± SEM. *p < <NUM>.

The binding of SUL-<NUM> to the antagonist binding site on the α1A-AR, induced fit molecular docking simulation was performed, using prazosin as a reference as follows.

The primary sequence of α1A adrenoceptor was obtained from UniProt database (The UniProt Consortium, <NUM>) using reference code P35348 and uploaded to SWISS-MODEL in order to build a homology model, resulting in <NUM> templates. Subsequently, template ligand codes were used to query the PDB database to obtain structural data in SMILES format, which were processed by Chemmine to detect similarities with SUL-<NUM>. The SWISS-MODEL template that contained a ligand with the highest similarity score (a D3 dopamine receptor in complex with, Eticlopride, ETQ) was used to align the α1A-AR sequence onto a modelled backbone. The resulting homology model was validated by Ramachandran plot and prepared with Protein Preparation Wizard by the addition of hydrogens, bond order assignment, generation of partial charges to heteroatoms and disulfide bonds. Final refinement was performed by hydrogen bond assignment at pH <NUM> and restrained minimization at <NUM> RMSD.

Prazosin, SUL-<NUM> and SUL-<NUM> structural files were converted from SMILES to 3D structures using LigPrep. Protonation states were generated with Epik at pH <NUM> and small molecule energy parameters were computed using OPLS3 forcefield.

Flexible molecular docking simulation was performed using Induced Fit, part of the Schrödinger Small-Molecule Drug Discovery suite. A binding centroid was defined between residues involved in antagonist binding confirmed by mutagenesis (PHE312, PHE308 and ASP106) and ligands were docked within 15Å, using an extended sampling protocol without constrains. Residues within 5Å of resulting ligand poses were refined using Prime to improve ligand conformational sampling. Finally, the Scorpion server was used for the assessment and classification of small molecule-protein interactions and the final results were rendered using PyMOL <NUM>.

To explore the effects of the enantiomers of (<NUM>-hydroxy-<NUM>,<NUM>,<NUM>,<NUM>-tetramethylchroman-<NUM>-yl)(piperazin-<NUM>-yl)methanone (SUL-<NUM> and SUL-<NUM>) on constriction of isolated porcine intrarenal arteries, cumulative dose response curves to the α<NUM> adrenoceptor agonist phenylephrine (PE) were constructed in the presence and absence of SUL-<NUM> and SUL-<NUM>.

Whereas SUL-<NUM> exerted a dose-dependent increase of EC<NUM> (Figure 1A, Table <NUM>), we observed no significant effects after treatment with SUL-<NUM> (<FIG>, Table <NUM>).

Additionally, the effects of SUL-<NUM> were investigated on stimulation with methoxamine, which is an alternative α<NUM> adrenoceptor agonist. Similar to PE, dose response curves to methoxamine were shifted rightward by SUL-<NUM> pre-treatment (<FIG>). Removal of the endothelium did not abrogate the effects of SUL-<NUM> on methoxamine induced constriction (<FIG>).

To gain insight into receptor specificity of SUL-<NUM>, the effects of SUL-<NUM> on histamine and U46619 (a synthetic thromboxane agonist) induced constrictions were investigated (<FIG>). SUL-<NUM> did not affect constriction responses to histamine (Table <NUM>) and although the shift in EC50 of U46619-induced constrictions in the presence of <NUM> SUL-<NUM> was statistically significant (Table <NUM>), the small effect size led us to exclude an action of SUL-<NUM> on thromboxane receptors.

Inhibition of EGF receptor (EGFR) transactivation is known to inhibit α<NUM> adrenoceptor mediated constrictions (REF). Therefore, we investigated the role of EGFR transactivation in SUL-<NUM> mediated inhibition of vasoconstriction. For this, porcine intrarenal arteries were pre-treated with the EGFR blocker AG1478 (<FIG>). First, an initial measurement was performed to determine the dose of AG1478 which would cause maximal inhibition of vascular constriction induced by PE (<FIG>). Subsequently, isolated arteries were treated with AG1478 (<NUM>) and SUL-<NUM> (<NUM>) and studied for PE-induced vasoconstriction. Despite maximal inhibition of EGFR transactivation by AG1478, SUL-<NUM> still demonstrated an additional inhibitory effect on PE-mediated constriction (<FIG>).

To further investigate the mechanisms through which SUL-<NUM> inhibits α<NUM> adrenoceptor mediated contractions, PE-induced calcium transients were studied in CHO cells stably overexpressing the human α<NUM> adrenoceptor subtypes A, B and D. SUL-<NUM> shifted dose response curves rightwards for all three α<NUM> adrenoceptor subtypes (<FIG>, B and C, Table <NUM>). SUL-<NUM> did not affect calcium transients in any of the investigated α<NUM> adrenoceptor subtypes (only shown for the α<NUM> adrenoceptor A subtype in <FIG>).

To confirm specificity of SUL-<NUM> for the α<NUM> adrenoceptor additionally histamine and U46619 induced calcium transients were studied in HeLa cells endogenously expressing human histamine H<NUM> receptor. SUL-<NUM> did not significantly affect histamine and U46619 induced calcium transients (<FIG> and Table <NUM>).

SUL-<NUM> affected PE-induced calcium transients, indicating that the effects of SUL-<NUM> are upstream of calcium. We therefore explored whether SUL-<NUM> could directly interact with the α<NUM> adrenoceptor as a receptor antagonist. For this, a displacement binding assay was performed on the α1A adrenoceptor transgenic CHO cells using radiolabeled prazosin, an established α1A adrenoceptor antagonist. SUL-<NUM> was more potent in displacing the radioligand compared to SUL-<NUM>, which displaced [<NUM>-Methoxy-<NUM>]-prazosin only at concentrations higher than <NUM> (<FIG>).

Prazosin coexists in two protonation forms at pH <NUM>. In the protonated form, the N1 assumes a positive charge, subsequently forming a salt bridge with the negatively charged side chain of ASP106, ultimately causing this form to assume an inverted orientation relative to its non-protonated form. The quinazoline scaffold of non-protonated prazosin was docked close to TM5 to form a confocal hydrogen bond between the <NUM>,<NUM>-methoxy groups and SER188, a hydrogen bond between furan oxygen and SER83, and between prazosin carboxamide and GLN177 side chain; van der Waals interactions with side chains of PHE86, VAL107, ILE178, PHE289, MET292, and PHE312; π-π interactions with PHE288 and PHE312; and a π-hydrogen bond interaction with the side chain carboxy group and backbone peptide carboxamide of ASP106. The proposed binding mode of non-protonated prazosin indicated interactions which were in accord with those described in the literature.

An induced fit of SUL-<NUM> and SUL-<NUM> demonstrated alignment of the chromane scaffold with prazosin quinazoline, <NUM>-hydroxy groups (SUL) and <NUM>-metoxy (prazosin) as well as over their common piperazine moiety. Residues which were involved in forming contacts with all three compounds were VAL107, ILE178, SER188, PHE288, PHE289.

Glide scores computed using the Schrödinger Small-Drug Discovery Suite were - <NUM> kcal×mol-<NUM>, -<NUM> kcal×mol-<NUM> and -<NUM> kcal×mol-<NUM> for prazosin, SUL-<NUM> and SUL-<NUM> respectively. Prazosin and SUL-<NUM> formed contacts with PHE312 and ASP106 confirmed in prazosin binding by mutagenesis, whereas SUL-<NUM> did not show interactions with these residues. Additionally, the chirality of SUL-<NUM> enables the orientation of its carboxamide towards ASN179, effectively forming a hydrogen bond. Additional hydrogen bond was formed between its protonated N-terminal and TYR316.

Claim 1:
The (2R) enantiomeric form of a <NUM>-chromanol derivative, wherein the derivative is (2R)(<NUM>-hydroxy-<NUM>,<NUM>,<NUM>,<NUM>-tetramethylchroman-<NUM>-yl)(piperazin-<NUM>-yl)methanone and pharmaceutically acceptable salts thereof for use in the prophylaxis or treatment of vasoconstriction related disorders or conditions wherein said vasoconstriction related disorders or conditions is selected from the group consisting of pulmonary hypertension, portal hypertension, vasospastic diseases, Raynaud's disease, acrocyanosis, livedo reticularis, post-traumatic dystrophy, (pre)eclampsia, Buerger's disease, pulmonary arterial hypertension, heart failure with preserved ejection fraction, and cardiac hypertrophy and fibrosis.