R-phenhexyline for treatment of dyskinesia

Abstract

Disclosed are compositions and methods for selectively targeting the M1 and / or M4 muscarinic receptors, compositions and methods for treating dyskinesia, such as dyskinesia, with improved formulations of dipheniraxol, and in particular compositions comprising high chiral purity R-dipheniraxol or enantiomerically enriched R-dipheniraxol, and methods for selectively targeting the M1 and / or M4 muscarinic receptors, compositions and methods for treating dyskinesia, such as dyskinesia, with improved formulations of dipheniraxol, and in particular compositions comprising high chiral purity R-dipheniraxol or enantiomerically enriched R-dipheniraxol.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of priority of U.S. Provisional Patent Application Serial No. 63 / 407,219, filed on September 16, 2022, entitled "R - TRIHEXYPHENIDYL FOR TREATMENT OF MOVE MENT DISORDERS", which is incorporated herein by reference in its entirety.

[0003] Federally Sponsored Research or Development

[0004] This invention was made with government support under Grant No. T32 HD069038 awarded by the National Institutes of Health. The government has certain rights in this invention. Background of the Invention Field of the Invention

[0006] The present invention relates to the treatment of movement disorders by selectively targeting M1 and / or M4 muscarinic receptors that are preferentially expressed in the central nervous system (CNS) using enantiomerically enriched R - trihexyphenidyl. Background Art

[0007] Dystonia is a movement disorder characterized by sustained or intermittent muscle contractions that cause abnormal, often repetitive movements, postures, or both. Dystonic movements are typically patterned, distorted, and may be tremulous. Dystonia is usually triggered or worsened by voluntary action and is associated with muscle overflow activation. One of the most common causes of childhood dystonia is neonatal brain injury leading to cerebral palsy, which affects 3 in every 10,000 live births. Dystonia is under - recognized, but it is a major determinant of functional impairment in cerebral palsy. In children with dystonia, especially those with dystonia secondary to structural brain injury or metabolic disorders, there is a significant unmet need for symptomatic treatment options.

[0008] Trihexyphenidyl (THP) is an antispasmodic drug used to treat stiffness, tremors, spasms, and poor muscle control. It is an antimuscarinic agent and is commonly used to manage Parkinson's disease as well as other movement disorders. The racemic mixture of THP (containing both the R-enantiomer and S-enantiomer in a 50:50 ratio) is currently approved as a generic drug (first approved in 1949) for patients, including for the treatment of dystonia. However, there is substantial evidence demonstrating inconsistent effectiveness in treating dystonia in children with cerebral palsy. In addition, current treatment regimens are clinically ineffective because little is known about the disposition of trihexyphenidyl in the body and there are no standardized dosing guidelines, resulting in a wide range of initial doses such that treatment may require extensive trial and error by clinicians and patients to find an effective dose in an individual patient. In addition, the drug is commonly associated with intolerable, treatment-limiting side effects, causing patients to discontinue the drug even when it is otherwise effective in improving the patient's dystonia. Given the limitations of using the current THP racemic formulation and the lack of an otherwise effective drug for these conditions, there remains a need for therapeutic compositions and regimens for the improvement of dystonia in cerebral palsy, Parkinson's disease, and other movement disorders. SUMMARY OF THE INVENTION

[0009] Accordingly, embodiments of the present invention present a clinically important alternative for the treatment of dystonia and other movement disorders associated with abnormal firing of striatal cholinergic interneurons. Specifically, a drug that selectively targets M1 and / or M4 receptors that are preferentially expressed in the CNS can provide improved efficacy while reducing side effects caused by binding to other receptor subtypes (M2, M3, and M5) that are predominantly expressed peripherally (outside the CNS). The drug will selectively target the muscarinic receptors involved in movement disorders (including dystonia, Parkinson's disease, cerebral palsy, etc.) but will not target the peripheral muscarinic receptors that cause many of the side effects of current drugs. This will help treat individuals with dystonia or Parkinson's disease or other conditions that may benefit from M1 and / or M4 inhibition by providing a drug with more targeted sites of action, improving efficacy and reducing side effects.

[0010] Accordingly, a method of treating a movement disorder is contemplated herein by administering a therapeutically effective amount of enantiomerically enriched R-trihexyphenidyl ( Figure 1 ) or a pharmaceutically acceptable salt thereof to a subject in need thereof (i.e., a subject with a movement disorder). Preferably, the administered composition comprises purified R-trihexyphenidyl and more preferably is substantially free of the S-trihexyphenidyl enantiomer. The enantiomerically enriched or purified R-trihexyphenidyl agent can be used as a selective / specific inhibitor of M1 and M4 receptors and more effectively treat movement disorders.

[0011] The present invention also describes methods for selectively targeting M1 and / or M4 muscarinic receptors in a subject suffering from a movement disorder. The methods include administering to the subject a therapeutically effective amount of enantiomerically enriched R-benztropine or a pharmaceutically acceptable salt thereof. Preferably, the administered composition comprises purified R-benztropine, and more preferably is substantially free of the S-benztropine enantiomer.

[0012] The present invention also describes a therapeutic composition comprising (consisting essentially of or consisting of) enantiomerically enriched R-benztropine or a pharmaceutically acceptable salt thereof dispersed in a pharmaceutically acceptable carrier. In one or more embodiments, the therapeutic composition may be in a pharmaceutical or unit dosage form, such as a tablet, powder, gelatin capsule, 3-D printed personalized dosage form, etc.

[0013] Advantageously, administering R-benztropine as a single enantiomer may be safer and more effective because R-benztropine is a more selective / specific inhibitor of M1 and M4 receptors and simultaneously avoids side effects that may be attributed to the indiscriminate interaction of S-benztropine with M1-M5 receptors expressed outside the CNS. This is supported by the results and data presented herein, namely that the R-benztropine and S-benztropine enantiomers have different inhibitory activities against multiple muscarinic receptor subtypes and have different clearance pathways and are metabolized by different drug-metabolizing enzymes such as cytochrome P450 (CYP). Overall, the embodiments described herein have important pharmacogenomic applications for the personalization of drug therapy.

[0014] The present invention also describes improved methods of treatment for treating and managing movement disorders by taking advantage of unique factors of an individual patient (to facilitate precision medicine). For example, the embodiments described herein include obtaining or identifying the cytochrome P450 genotype (diplotype) or genotype-predicted drug metabolism phenotype (and drug-drug interactions) of a subject to inform treatment and dosing decisions. For example, subjects with reduced CYP2D6 or CYP3A4 / CYP3A5 activity due to genetic variation (poor metabolizers) or drug-drug interactions are candidates for the accumulation of S-benztropine levels that may lead to a higher incidence of side effects. Such subjects are candidates for the recommended enantiomerically enriched R-benztropine formulation. The methods include obtaining the genotype-predicted CYP450 metabolism phenotype of the individual and administering to a subject who is a poor metabolizer of CYP2D6 or CYP3A4 / CYP3A5 a therapeutically effective amount of enantiomerically enriched R-benztropine or a pharmaceutically acceptable salt thereof. The disclosed embodiments also relate to methods of initiating R-benztropine treatment in patients who are poor metabolizers of CYP2D6 or CYP3A4 / CYP3A5.

[0015] Similarly, a subject identified as a rapid (or ultra-rapid) CYP2C19 metabolizer is a candidate in whom the R-benztropine level may be rapidly depleted, and who can tolerate and even require a higher initial dose, especially when treated with an enantiomer-enriched R-benztropine formulation. If the subject is also a normal or rapid CYP2D6 or CYP3A4 / CYP3A5 metabolizer, the subject may also tolerate a higher dose of the racemic mixture without suffering side effects attributable to the S-enantiomer. The method includes obtaining the genotype-predicted CYP450 metabolic phenotype of the individual, and administering to the subject who is a rapid CYP2C19 metabolizer a therapeutically effective amount of an enantiomer-enriched R-benztropine or a racemic mixture or a pharmaceutically acceptable salt thereof.

[0016] Similarly, the method can be used to treat the dyskinesia of a subject who is a CYP2C19 poor metabolizer. The method includes obtaining the genotype-predicted CYP450 metabolic phenotype of the individual, and administering to the subject a therapeutically effective amount of an enantiomer-enriched R-benztropine or a pharmaceutically acceptable salt thereof, wherein the subject is a CYP2C19 poor metabolizer, and wherein the therapeutically effective amount is a low dose of the R-benztropine compared to the standard clinical recommended dose. For example, the effective dose in such an individual can be half of the standard recommended dose, preferably wherein the low dose is from 3 mg / day to 15 mg / day.

[0017] The method disclosed herein can also be used to treat the dyskinesia of a subject who is a CYP2D6 or CYP3A4 / CYP3A5 poor metabolizer to minimize side effects. The method includes obtaining the genotype-predicted CYP450 metabolic phenotype of the individual, and reducing the initial dose of the racemic mixture of benztropine or the racemic mixture of a pharmaceutically acceptable salt thereof to less than 1 mg / day and administering to the subject, wherein the subject is a CYP2D6 or CYP3A4 / CYP3A5 poor metabolizer, or increasing the initial dose of the racemic mixture of benztropine or the racemic mixture of a pharmaceutically acceptable salt thereof to greater than 6 mg / day and administering to the subject, wherein the subject is a CYP2D6 or CYP3A4 / CYP3A5 normal or ultra-rapid metabolizer, wherein the initial dose is based on the initial dose recommended in the clinical guidelines regarding benztropine.

[0018] The present disclosure also relates to a method of administering an initial dose of an M1 and / or M4 muscarinic receptor inhibitor to a subject in need thereof, wherein the initial dose is based on the initial dose recommended in the clinical guidelines for the inhibitor, and wherein the inhibitor is selected from the racemic mixture of trihexyphenidyl, the enantiomerically enriched R-trihexyphenidyl, and pharmaceutically acceptable salts thereof. The method generally includes obtaining the genotype of a set of cytochrome P450 enzymes in the subject that includes at least CYP2D6 and / or CYP2C19 alleles, and assigning to the subject a metabolic phenotype selected from poor metabolizer, intermediate metabolizer, or ultra-rapid metabolizer for each enzyme based on the number of functional alleles of each cytochrome P450 gene. The method includes administering to the patient an initial dose of the inhibitor, wherein the initial dose is: (a) if the metabolic phenotype is one or more of CYP2D6 poor metabolizer, CYP2D6 intermediate metabolizer, or CYP2C19 poor metabolizer, the initial dose is half of the initial dose recommended in the clinical guidelines; or (b) if the metabolic phenotype is one or more of CYP2D6 ultra-rapid metabolizer or CYP2C19 ultra-rapid metabolizer, the initial dose is the same as or higher than the initial dose recommended in the clinical guidelines.

[0019] The present disclosure also describes a method of reducing side effects caused by an initial dose of an M1 and / or M4 muscarinic receptor inhibitor in a subject in need thereof, wherein the initial dose is based on the initial dose recommended in the clinical guidelines for the inhibitor, and wherein the inhibitor is the racemic mixture of trihexyphenidyl or a racemic mixture of pharmaceutically acceptable salts thereof. The method includes obtaining the genotype of a set of CYP2D6 alleles of cytochrome P450 in the subject, and assigning to the subject a metabolic phenotype selected from poor metabolizer, intermediate metabolizer, or ultra-rapid metabolizer for CYP2D6 based on the number of functional alleles of CYP2D6. The method includes administering to the patient an initial dose of the inhibitor, wherein the initial dose is: (a) if the metabolic phenotype is one or more of CYP2D6 poor metabolizer or CYP2D6 intermediate metabolizer, the initial dose is half of the initial dose recommended in the clinical guidelines; or (b) if the metabolic phenotype is CYP2D6 ultra-rapid metabolizer, the initial dose is the same as or higher than the initial dose recommended in the clinical guidelines.

[0020] The present disclosure also describes an agent for selectively targeting M1 and / or M4 muscarinic receptors or treating dystonia in a subject in need thereof. The agent generally includes a therapeutic composition that includes an enantiomerically enriched R-trihexyphenidyl or a pharmaceutically acceptable salt thereof according to any embodiment disclosed herein, or a pharmaceutical dosage form according to any embodiment disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The molecular structure of trihexyphenidyl is shown and shows the position of a) the chiral center (chiral carbon) and the resulting b) R-enantiomer and c) S-enantiomer, which have the same chemical structure but differ in three dimensions.

[0022] Figure 2 Data identifying CYP metabolic pathways involved in the biotransformation (metabolism) of R-trihexyphenidyl and S-trihexyphenidyl are presented.

[0023] Figure 3 Shown are the results of in vitro incubations in which R-benzhexol (1,000 ng / ml) and S-benzhexol (1,000 ng / ml) were incubated with heterologously expressed CYP2C19, CYP2D6, and CYP3A4, and the metabolites produced showed that R-THP-M1 was formed almost exclusively by CYP2C19, while S-THP-M2 was formed primarily by CYP2D6.

[0024] Figure 4A- Figure 4B , Figure 4C- Figure 4D and Figure 4E- Figure 4F Illustrated is the interindividual variability in plasma concentrations of CYP2C19- and CYP2D6-dependent metabolites in three patients with different CYP2C19 and CYP2D6 genotypes when prescribed racemic trihexyphenidyl and concomitantly administered an inhibitor of CYP2C19 activity. Figure 4A- Figure 4B Graphs showing the plasma concentration-time profiles of (A) R-trihexyphenidyl and (B) S-trihexyphenidyl for Patient 1 who had an intermediate metabolizer (IM) genotype of CYP2C19 (CYP2C19*1 / *2), a normal metabolizer (NM) genotype of CYP2D6 (CYP2D6*1 / *2), and concurrently received the CYP2C19 inhibitor, esomeprazole 40 mg / day.

[0025] Figure 4C- Figure 4D Shown are graphs of the plasma concentration-time curves of (C) R-benzhexol and (D) S-benzhexol for Patient 2 who has an intermediate metabolizer (IM) genotype of CYP2C19 (CYP2C19*2 / *17), an intermediate metabolizer (IM) genotype of CYP2D6 (CYP2D6*1 / *4) and concurrently receives a CYP2C19 inhibitor, namely omeprazole 20 mg / day.

[0026] Figure 4E- Figure 4FGraph showing plasma concentration-time curves of (E) R-benztropine and (F) S-benztropine for patient 3 who has a normal metabolizer (NM) genotype for CYP2C19 (CYP2C19*1 / *1), a poor metabolizer (PM) genotype for CYP2D6 (CYP2D6*4 / *4), and is not receiving a CYP2C19 inhibitor in parallel.

[0027] Figure 5A- Figure 5B Demonstrates the inter-individual variability in CYP2C19- and CYP2D6-dependent benztropine metabolism on the plasma concentrations of racemic benztropine, R-benztropine, and S-benztropine from Figure 4A- Figure 4B patient 1, who was following a prescribed dose of (A) 0.05 mg / kg of racemic benztropine and (B) a dose normalized to 0.1 mg / kg.

[0028] Figure 5C- Figure 5D Demonstrates the inter-individual variability in CYP2C19- and CYP2D6-dependent benztropine metabolism on the plasma concentrations of racemic benztropine, R-benztropine, and S-benztropine from Figure 4C- Figure 4D patient 2, who was following a prescribed dose of (C) 0.025 mg / kg of racemic benztropine and (D) a dose normalized to 0.1 mg / kg.

[0029] Figure 5E- Figure 5F Demonstrates the inter-individual variability in CYP2C19- and CYP2D6-dependent benztropine metabolism on the plasma concentrations of racemic benztropine, R-benztropine, and S-benztropine from Figure 4E- Figure 4F patient 3, who was following a prescribed dose of (E) 0.13 mg / kg of racemic benztropine and (F) a dose normalized to 0.1 mg / kg ( Figure 5F ). Detailed Description

[0030] The present invention relates to a method for treating movement disorders using the following: an improved benztropine formulation, and in particular a composition comprising highly enantiopure R-benztropine or enantiomer-enriched R-benztropine. Accordingly, therapeutic compositions are described herein that comprise (consist essentially of or consist of) highly enantiopure R-benztropine or enantiomer-enriched R-benztropine or a pharmaceutically acceptable salt thereof dispersed in a pharmaceutically acceptable carrier. As used herein, "highly enantiopure" or "enantiomer-enriched" means that the compound is predominantly the stated enantiomer, preferably at least 75%, more preferably at least 85%, even more preferably at least 95%, even more preferably at least 99% of the compound present is the R-enantiomer (compared to a conventional benztropine racemic mixture typically containing a 50:50 mixture of the R- and S-enantiomers). Thus, the compound is preferably purified to remove substantially all of the S-enantiomer from the racemic mixture.

[0031] Pharmaceutically acceptable salts include hydrochloride, hydrobromide, acetate, benzoate, carbonate, mesylate, hydrogen tartrate, and the like. Unless otherwise indicated, references herein to therapeutic doses of enantiomers are intended to cover the salt forms.

[0032] Accordingly, various embodiments of the present invention relate to multi-component systems, pharmaceutical compositions, and methods that include highly enantiopure R-benztropine or enantiomer-enriched R-benztropine, having a dose and enantiopurity different from what can be achieved using a conventional racemic mixture and without causing adverse effects. For therapeutic use, highly enantiopure R-benztropine or enantiomer-enriched R-benztropine is administered as part of a composition comprising a therapeutically effective amount of highly enantiopure R-benztropine or enantiomer-enriched R-benztropine dispersed in a pharmaceutically acceptable carrier.

[0033] As used herein, the term "carrier" is used to refer to a diluent, excipient, vehicle, etc. in which the R-enantiomer can be suspended or dispersed for administration. Suitable carriers will be pharmaceutically acceptable. As used herein, the term "pharmaceutically acceptable" means not biologically undesirable or otherwise undesirable, i.e., it can be administered to a subject without undue toxicity, irritation, or allergic response and will not cause unacceptable biological effects or interact in a harmful manner with the R-enantiomer or any other component of the composition containing it. A pharmaceutically acceptable carrier will be selected to minimize any degradation of the R-enantiomer or other agent and to minimize any adverse side effects in the subject. Typically, trihexyphenidyl is provided in tablet form or as a liquid elixir or oral solution. Pharmaceutically acceptable ingredients include those acceptable for veterinary as well as human drug use and will depend on the route of administration. Other ingredients may be included in the composition, including preservatives, buffers, salts, and other pharmaceutically acceptable ingredients. For example, an R-enantiomer composition suitable for oral administration contains binders or bulk excipients for compression into tablets or gel-caps, such as colloidal silicon dioxide, calcium hydrogen phosphate, lactose monohydrate, magnesium stearate, microcrystalline cellulose, sodium starch glycolate, starch, etc., while liquid elixirs or oral suspensions include 5% alcohol, citric acid, parabens, sodium chloride, sugar alcohols (e.g., sorbitol), flavoring agents, etc.

[0034] The composition may contain a therapeutically effective amount of the R-enantiomer dispersed in a carrier. As used herein, a "therapeutically effective" amount means an amount that will elicit the biological or medical response of a tissue, system, or subject sought by a researcher or clinician, and in particular an amount that will cause a desired improvement in dystonia or other movement disorders (such as by selectively blocking M1 and / or M4 muscarinic receptors). Thus, the R-enantiomer is preferably provided in an amount sufficient to selectively bind to these receptors. Those skilled in the art recognize that an amount can be considered therapeutically "effective" even if the condition is not completely eradicated or stopped, provided that there is a partial improvement or alleviation of the condition or symptoms and / or effects in the subject, such as a reduction in the number, frequency, or severity of uncontrolled movements, spasms, or other dystonia metrics, or an improvement in the measurement of gross or fine motor function tasks or a recognized scale for assessing dystonia (e.g., the Burke-Fahn-Marsden Dystonia Scale, the Barry-Albright Dystonia Scale, the Melbourne Unilateral Upper Limb Function Assessment, etc.). It is also contemplated that the improved enantiomer-enriched trihexyphenidyl can be used as part of a multi-faceted treatment plan.

[0035] It is also contemplated that the patient may be able to achieve a therapeutically effective amount of the enantiomer at an initial dose lower than that of the previous racemic mixture. Generally, the therapeutically effective amount can be half of the dose required for the racemic mixture. It is also contemplated that the subject may be able to tolerate higher doses and achieve even greater therapeutic efficacy because the adverse side effects typically caused by the S-enantiomer are avoided with the new treatment modality. In one or more embodiments, the potential dose of trihexyphenidyl R may include a range from 3 mg / day to 30 mg / day or higher. That is, without wishing to be bound by theory, it is proposed that when only the R-enantiomer is used, the current effective dose recommendation of 6 mg to 60 mg / day for the racemic mixture can be halved. However, conversely, it is also proposed that when the treatment-limiting side effects of trihexyphenidyl S are removed, the subject may actually be able to tolerate even higher doses of the enantiomer-enriched trihexyphenidyl R (i.e., greater than 60 mg / day), with a correspondingly greater therapeutic efficacy (again, without the side effects typically encountered when using the same dose of the racemic mixture).

[0036] The method includes administering a therapeutically effective amount of trihexyphenidyl R or a pharmaceutically acceptable salt thereof to a subject in need (i.e., a subject suffering from a movement disorder). Preferably, the administered composition comprises purified trihexyphenidyl R, and more preferably is substantially free of the S-enantiomer of trihexyphenidyl. As used herein, "substantially free of" means that the composition (racemic mixture) has been purified to remove all or substantially all of the S-enantiomer of trihexyphenidyl, and in particular the composition contains less than 1% w / w, preferably less than 0.5% w / w, and even more preferably less than 0.1% w / w of the S-enantiomer. That is, at least 99% w / w, preferably at least 99.5% w / w, and more preferably 99.9% w / w of the trihexyphenidyl present in the composition is trihexyphenidyl R. Depending on the dosage form, the composition can be administered once daily, twice daily, or three times daily to achieve the total daily dose described herein. That is, the "effective" dose or "initial" dose refers to the total daily dose, which can be divided into one, two, or three separate administrations within a day to reach the total recommended dose for that day. Extended-release dosage forms may require less frequent dosing. As mentioned above, trihexyphenidyl is typically administered orally as tablets or liquid elixirs or oral suspensions.

[0037] Advantageously, trihexyphenidyl is a selective / specific inhibitor of M1 and M4 receptors, with an activity 525 times that of S-trihexyphenidyl, which also interacts indiscriminately with all five receptors (M1-M5) with comparable inhibitory potency. Thus, trihexyphenidyl is a more effective antimuscarinic agent, and improved therapeutic benefits can be obtained by using highly enantiopure trihexyphenidyl or enantiomerically enriched trihexyphenidyl, while avoiding side effects attributable to the S-enantiomer. In addition, the stereoselective metabolism of trihexyphenidyl means that clinicians can use pharmacogenetic testing and precision medicine to identify subjects who may be intolerant to the conventional racemic mixture of trihexyphenidyl.

[0038] Metabolic phenotyping can be obtained using any standard method, including phenotyping based on test probe substances such as dextromethorphan (DXM). However, more commonly, pharmacogenetic testing from patient body fluid samples (blood, serum, urine, saliva, etc.) can be used to assign a predicted metabolizer phenotype or status according to established guidelines such as those published by the Clinical Pharmacogenetics Implementation Consortium (CPIC). There are currently genetic assays that predict metabolic phenotypes based on the presence or absence of gene variants of various CYP450 enzymes, which result in altered metabolic clearance of a given drug in an individual. Based on an understanding of the functional effects of specific pharmacogenetic variants or "alleles" on enzyme activity, the results of genetic assays are translated into expected metabolic phenotypes. Publicly available resources are used to facilitate this translation process. The Pharmacogene Variation (PharmVar) Consortium evaluates, catalogs, and curates reports on allelic variants of genes that affect drug metabolism, disposition, and response, which are available at pharmvar.org; and provides a unified nomenclature system for use by the global pharmacogenetic / genomic community (including academia, medicine, industry, and regulatory agencies). The standardized nomenclature (core allele definitions) developed by PharmVar is used by the Pharmacogenomics Knowledgebase (Pharmaco gThe Pharmacogenomics Knowledgebase (PharmGKB) and the Clinical Pharmacogenetics Implementation Consortium (CPIC). PharmGKB is an NIH-funded resource that provides information on how human gene variations affect responses to drugs and collects, curates, and disseminates knowledge about clinically actionable gene-drug associations and genotype-phenotype relationships. CPIC creates, curates, and publishes freely available, peer-reviewed, evidence-based, updatable, and detailed gene / drug clinical practice guidelines that follow a standardized format, including systematic grading of evidence and giving clinical recommendations based on standardized terminology and peer review. CPIC guidelines are published at cpicpgx.org, are published in top clinical pharmacology journals, are indexed in PubMed recognized by academic societies, and are cited by ClinGen and PharmGKB. The coordinated activities of PharmVar, PharmGKB, and CPIC ensure the consistency of the evaluation of new allele data submitted to PharmVar for evaluation and curation, as well as the evaluation of evidence for assessing the association between drug gene variations and drug clearance / systemic drug exposure and the resulting clinical consequences (i.e., related to drug efficacy or side effect risk), so as to clinically apply drug gene variation data in the form of guidelines to convert gene laboratory test results into actionable prescribing decisions for the drugs involved.

[0039] Genetic variations or polymorphisms in these enzymes can affect enzyme activity, ranging from complete loss of catalytic activity in poor metabolizers to increased enzyme activity associated with rapid clearance in ultrarapid metabolizers. Generally, having fully functional alleles on each chromosome results in the assignment of the "normal metabolizer" status, and the presence of non-functional variants on each chromosome results in the assignment of the "poor metabolizer" status. Intermediate metabolizer status typically involves a diplotype composed of a non-functional allele combined with an allele with reduced activity or a partially functional allele. Depending on the drug gene involved, an ultrarapid metabolizer status can be assigned when two or more functional copies of the gene are present on the same chromosome (e.g., a duplication or amplification event) or when there are alleles associated with increased activity. The assignment of predicted function to specific alleles is gene-specific. For example, the CYP2D6*2 allele is associated with full enzyme activity, while the CYP2C19*2 allele is associated with complete loss of activity. Information on variants and related phenotypes for each CYP450 enzyme is continuously updated and available on the PharmVar website. Other major sources of PGx guidelines include clinical practice guidelines from medical organizations, the Pharmacogenomics Knowledgebase (PharmGKB), and drug labels and pharmacogenetic association tables from the US Food and Drug Administration (FDA).

[0040] Once variants are identified, they can be converted into activity scores that reflect the relative activity of enzyme activity in a particular patient (see, e.g., Gaedigk, A., Simon, S., Pearce, R., Bradford, L., Kennedy, M. and Leeder, J. (2008), The CYP2D6 Activity Score: Translating Genotype Information into a Qualitative Measure of Phenotype. Clinical Pharmacology & Therapeutics, 83: 234-242. doi:10.1038 / sj.clpt.6100406). PharmVar, PharmGKB and CPIC continuously review the activity scores and the associated genotype-predicted phenotypes.

[0041] Genotype-predicted metabolic phenotypes are classified and labeled relative to the average individual labeled as a normal metabolizer. Common nomenclature refers to one extreme of these functional phenotypes as "poor metabolizers" and the other extreme as "ultrarapid metabolizers". Poor metabolizers are typically individuals in whom both copies (both alleles) of the gene have low activity or are non-functional. Ultrarapid metabolizers are typically individuals who carry at least one allele with a duplication of the normally functioning allele (and thus an overall increase in function), even if the other allele may have reduced function but is still functional and is usually present as multiple copies of the reduced-function allele. "Normal" metabolizers are typically individuals who carry two normally functioning alleles, or one normally functioning allele and a duplication of the reduced-function allele. "Intermediate" metabolizers fall between poor metabolizers and normal metabolizers and are typically individuals who carry one normally functioning allele or a duplication of the reduced-function allele and one non-functional allele, or two reduced-function alleles, or one reduced-function allele and a duplication of the reduced-function allele, resulting in an overall activity level that is at least somewhat (higher than poor metabolizers but still lower than normal metabolizers).

[0042] Based on the disclosed methods, an "activity score" for an enzyme can be calculated based on the individual activity values for each allele, and this activity score can be used to assign a predicted individual functional phenotype (Gaedigk et al., 2008). Generally, a total activity score of 0 (or less than 0.5) indicates a poor metabolizer, and an activity score of 2.5 and above indicates an ultra-rapid metabolizer. Normal metabolizers have an activity score of 1.5 - 2.0, and an activity score between 0.5 and 1 indicates an intermediate metabolizer. Activity score information for individual enzymes can be found on the PharmVar website, such as pharmvar.org / gene / CYP2D6 or pharmvar.org / gene / CYP2C19. Similarly, CYP isoforms can be measured by a variety of commercially available kits. In addition, in addition to genotype, drug-drug interactions must also be considered to account for any other xenobiotics that the subject is taking that can act as CYP450 inhibitors.

[0043] Thus, in one or more embodiments, a clinician can first identify a subject in need of treatment having a predicted functional phenotype of a poor metabolizer of CYP2D6 or CYP3A4 / CYP3A5, which is an ideal candidate for precision medicine. The clinician can use any suitable method for metabolic phenotyping (including genotype-predicted phenotypes and drug-induced phenotypes) to obtain the CYP450 metabolic phenotype of the individual (or preferably at least the CYP2D6 or CYP3A4 / CYP3A5 phenotype). For example, pharmacogenetic testing or metabolic phenotyping can be performed using test probe substances according to known protocols to evaluate the metabolites produced by the individual, or according to standard genotyping. Similarly, a variety of CYP450 assays are available, and new methods are being routinely developed. Pharmacogenetic testing of CYP450 enzyme activity is also routinely available, including the interpretation of results and the assignment of functional phenotypes.

[0044] When a subject is identified as having impaired CYP2D6 or CYP3A4 / CYP3A5 enzyme activity, the subject is labeled as a CYP2D6 or CYP3A4 / CYP3A5 poor metabolizer. In such cases, using precision or personalized medicine, clinicians are now informed that when treated with the racemic mixture of conventional trihexyphenidyl, the subject may have a higher risk of adverse side effects (due to the accumulation of S-trihexyphenidyl). In such cases, the clinician can adjust the initial dose of racemic trihexyphenidyl based on the subject's metabolic phenotype to minimize side effects. In contrast, subjects identified as "normal" metabolizers can start with a higher initial dose of racemic trihexyphenidyl and may have a lower risk of adverse side effects. However, as would be understood by one of ordinary skill in the art, the dose is determined via dose adjustments consistent with typical clinical care. In one or more embodiments, the methods described herein include administering a therapeutically effective amount of enantiomerically enriched R-trihexyphenidyl or a pharmaceutically acceptable salt thereof to a subject who is a CYP2D6 or CYP3A4 / CYP3A5 poor metabolizer. The disclosed embodiments also relate to methods of initiating treatment with enantiomerically enriched R-trihexyphenidyl in a patient who is a CYP2D6 or CYP3A4 / CYP3A5 poor metabolizer.

[0045] Similarly, when prescribing a conventional racemic mixture of trihexyphenidyl or an enantiomerically enriched R-trihexyphenidyl formulation for the treatment of dyskinesia, the clinician can utilize the individual's CYP2C19 metabolic phenotype (predicted from the CYP2C19 genotype). When a patient is identified as having impaired CYP2C19 enzyme activity, the patient is assigned to the CYP2C19 poor metabolizer status and can be effectively managed with a lower dose of the conventional racemic mixture of trihexyphenidyl or a formulation highly enriched in R-trihexyphenidyl. Similarly, patients with a CYP2C19 genotype associated with increased activity (such as CYP2C19*17 / *17) are assigned to the ultra-rapid metabolizer phenotype and may require a higher than usual dose to achieve a therapeutic concentration of R-trihexyphenidyl in vivo. It should be understood that a particular advantage of using enantiomerically enriched R-trihexyphenidyl is that by substantially removing S-trihexyphenidyl from the formulation, concerns associated with additional genetic variations from CYP2D6 isoforms are reduced or eliminated. Thus, using precision or personalized medicine, clinicians can now be better informed of the individual unique factors that can affect the therapeutic benefits and toxicity risks associated with different treatment regimens.

[0046] Accordingly, the embodiments described herein can be used to inform clinicians of treatment regimens in a more precise and personalized manner to improve patient outcomes. Those skilled in the art can develop appropriate treatment plans based on the patient's age and condition, the patient's tolerance to side effects, and the severity of the condition.

[0047] In some embodiments, highly enantiopure R-benztropine or enantiomerically enriched R-benztropine or a composition can be provided in unit dosage forms in a suitable container. The term "unit dosage form" refers to a physically discrete unit suitable as a single dose for human or animal use. Each unit dosage form can contain a predetermined amount of highly enantiopure R-benztropine or enantiomerically enriched R-benztropine (and / or other active agents) calculated to produce the desired effect in a carrier. In one or more embodiments, highly enantiopure R-benztropine or enantiomerically enriched R-benztropine can be provided separately from the carrier (e.g., in its own vial, ampoule, sachet, or other suitable container) for in situ mixing (e.g., in a pharmacy or at home) and then administration to a subject. In one or more embodiments, highly enantiopure R-benztropine or enantiomerically enriched R-benztropine is provided as discrete tablets, pills, gelatin capsules, 3-D printed individualized dosage forms, etc.

[0048] Also disclosed herein are kits containing highly enantiopure R-benztropine or enantiomerically enriched R-benztropine. The kits further contain instructions for administering the highly enantiopure R-benztropine or enantiomerically enriched R-benztropine to a subject. The highly enantiopure R-benztropine or enantiomerically enriched R-benztropine can be provided as part of a dosage unit already dispersed in a pharmaceutically acceptable carrier or separately from the carrier. The kits can further contain instructions for preparing the highly enantiopure R-benztropine or enantiomerically enriched R-benztropine for administration to a subject, including, for example, instructions for dispersing the highly enantiopure R-benztropine or enantiomerically enriched R-benztropine in a suitable vehicle to produce an elixir or oral suspension.

[0049] It should be understood that the therapeutic methods described herein are applicable to humans and for veterinary use in any suitable animal (including but not limited to dogs, cats, and other companion animals, as well as rodents, primates, horses, cattle, pigs, etc.). These methods can also be applied to clinical research and / or study.

[0050] The embodiments described herein are applicable to treating a subject in which selective inhibition of the M1 and / or M4 muscarinic receptors produces a beneficial effect in the subject. For example, the embodiments described herein are applicable to treating a subject suffering from a variety of movement disorders, including dystonia or dystonia secondary to another condition (such as Parkinson's disease, cerebral palsy, Angelman syndrome, or other genetically mediated movement disorders, etc.).

[0051] After reviewing the present disclosure text and the following working examples of this document, additional advantages of various embodiments of the present invention will be clear to those skilled in the art. It should be understood that unless otherwise indicated herein, the various embodiments described herein are not necessarily mutually exclusive. For example, a feature described or depicted in one embodiment may also be included in other embodiments, but not necessarily. Thus, the present invention encompasses various combinations and / or integrations of the specific embodiments described herein.

[0052] As used herein, the phrase "and / or" when used in a list of two or more items means that any one of the listed items can be taken alone, or any combination of two or more of the listed items can be taken. For example, if a composition is described as comprising or excluding components A, B, and / or C, then the composition can comprise or exclude only A; only B; only C; a combination of A and B; a combination of A and C; a combination of B and C; or a combination of A, B, and C.

[0053] "Enantiomers" refer to asymmetric molecules that can exist in two different isomeric forms, which are different in configuration in space. Other terms used to specify or refer to enantiomers include "stereoisomers" (due to different arrangements or stereochemistry around chiral centers; although all enantiomers are stereoisomers, not all stereoisomers are enantiomers). Molecules that exist in two enantiomeric forms are chiral, which means they can be considered to exist in "left-handed" and "right-handed" forms. The most common cause of chirality in organic molecules is the presence of a tetrahedral carbon bonded to four different substituents or groups. Such a carbon is called a chiral center, as Figure 1 shown. Enantiomers have the same empirical chemical formula and are generally considered to be chemically identical in terms of their reactions, their physical properties, and their spectral properties. However, there is an increasing awareness of the different pharmacokinetic properties of enantiomers or isomers of the same compound. The "R" and "S" designations are used in their usual meaning to denote the absolute configuration of a molecule around its chiral center.

[0054] This specification also uses numerical ranges to quantify certain parameters related to various embodiments of the present invention. It should be understood that when a numerical range is provided, such a range should be interpreted as providing literal support for claims that refer only to the lower limit value of the recited range and for claims that refer only to the upper limit value of the recited range. For example, the disclosed numerical range of about 10 to about 100 provides literal support for claims that refer to "greater than about 10" (without an upper limit) and for claims that refer to "less than about 100" (without a lower limit).

[0055] Examples

[0056] The following examples illustrate the method according to the present invention. However, it should be understood that these examples are provided by way of illustration and that nothing therein should be construed as limiting the overall scope of the present invention.

[0057] Example 1

[0058] Study on the Biotransformation of Trihexyphenidyl and Its Application in Dystonic Cerebral Palsy

[0059] Objective: Trihexyphenidyl (THP) is an anticholinergic drug commonly used to treat dystonia and other movement disorders in children with cerebral palsy or certain genetic disorders such as Angelman syndrome. The pathophysiology of dystonia includes an increase in the number of striatal cholinergic interneurons and abnormal excitation of striatal cholinergic interneurons. Therefore, anticholinergic drugs such as THP are potential treatments, and rodent models have demonstrated normalization of striatal activity after exposure to THP. For example, studies in mouse models have shown that trihexyphenidyl acts on the M4 muscarinic receptor in the striatum and normalizes dopamine release associated with dystonia. However, in clinical practice, patients treated with THP have demonstrated inconsistent efficacy and adverse effects (nausea, constipation, and urinary retention), which may be due to variations in the dose-exposure relationship. Due to adverse events, patients often need to reduce the dose or discontinue treatment. These mixed results have led modern recommendations to conclude that there is insufficient evidence for the effectiveness of trihexyphenidyl in people with cerebral palsy.

[0060] In Angelman syndrome, trihexyphenidyl can be used to treat dystonia, myoclonus, and other movement disorders. Rodent models of Angelman syndrome have demonstrated disrupted dopamine release, with increased dopamine in the nucleus accumbens and decreased dopamine in the striatum, leading to movement disorders and behavioral changes. Modulation of muscarinic receptors with an M4-selective antimuscarinic agent such as trihexyphenidyl can have the benefit of increasing dopamine release in the striatum, while muscarinic receptor antagonism of M1 and M5 receptors in the nucleus accumbens results in decreased dopamine release. Because trihexyphenidyl is a selective M1, M4 muscarinic antagonist, it has the potential to contribute to the treatment of both dopamine deficiency and excess in patients with Angelman syndrome, making it a promising therapeutic option for treating movement disorders and behavioral changes.

[0061] Many drugs are metabolized in the liver by one or more (and often in combination) of the cytochrome P450 (CYP) enzyme family. For example, CYP2D6 is a key xenobiotic-metabolizing enzyme involved in the clearance of many drugs. Genetic polymorphisms of CYP2D6 or other enzymes such as CYP3A4 / CYP3A5 or CYP2C19 result in large inter-individual variability in drug metabolism and, consequently, large inter-individual variability in drug clearance from the body. Similarly, how fast or slow an individual metabolizes and / or clears a drug affects how that drug functions in their body - both in terms of the degree of therapeutic efficacy and side effects.

[0062] Most patients can be characterized as having "normal" enzyme function of the various CYP450 enzymes and are facile at metabolizing certain drugs. However, some patients have little or no enzyme function for certain enzymes and can be considered or assigned to a "poor metabolizer" status for those enzymes, i.e., these patients have a significantly reduced ability to metabolize certain drugs that are metabolized via those particular enzymes. Thus, an individual's pharmacogenomic profile together with information on which CYP450 metabolic pathway a given drug follows can help predict dose effects. The consequence of reduced enzyme activity due to pharmacogenetic variability or drug-drug inhibition is the accumulation of the drugs involved and an increased risk of concentration-dependent side effects. Conversely, pharmacogenetic variants that result in increased activity, such as duplications / doublings of functional CYP2D6 variants or the CYP2C19*17 / *17 genotype, can lead to enhanced drug clearance from the body, resulting in sub-therapeutic concentrations and treatment failure. In addition, some drugs or foods act as inhibitors of CYP2D6, CYP3A4 / CYP3A5, or CYP2C19 enzyme function and, consequently, these drugs or foods can inhibit or reduce the metabolism of those drugs if co-administered or consumed within the time frame of the drug. These considerations are equally applicable to other enzymes in the CYP450 family.

[0063] For example, in the context of the present disclosure, as shown herein, a patient who is a poor metabolizer of CYP2D6 is predicted to have a reduced ability to metabolize and clear trihexyphenidyl S - enantiomer (the enantiomer responsible for side effects), and thus has a higher likelihood of side effects when treated with the racemic mixture. In such a case, the individual is a potential candidate for treatment with enantiomer - enriched trihexyphenidyl R - enantiomer. Similarly, in the context of the present disclosure, as shown herein, a patient who is a rapid metabolizer of CYP2C19 is predicted to have a rapid clearance of trihexyphenidyl R - enantiomer (the enantiomer responsible for therapeutic effect), and thus may benefit from a higher initial dose to ensure a sufficient (therapeutically effective) plasma level of trihexyphenidyl R - enantiomer (for binding to M1 and / or M4 receptors). And depending on whether the clinician treats with the racemic mixture or enantiomer - enriched trihexyphenidyl R - enantiomer, the CYP2D6 status of the individual can also be taken into account (if S - enantiomer metabolism is a concern).

[0064] The treatment regimen for the racemic mixture of THP is currently recommended to start at a low dose of 0.5 - 1 mg / day and be gradually increased by 1 mg every 3 - 5 days until beneficial or adverse effects occur. The usual effective dose varies widely, ranging from 6 to 60 mg / day, but some patients require higher doses. In short, little is known about the biotransformation of THP, which could inform an individualized dosing strategy to provide optimal systemic exposure for each patient. The biotransformation of THP was investigated through in - vivo and in - vitro analyses to determine whether a new regimen could improve drug response while reducing the side effects of this otherwise promising drug.

[0065] Methods: Trihexyphenidyl and deuterated trihexyphenidyl (D11 - THP, (racemic " 11 D - trihexyphenidyl", in which all 11 available hydrogens on the cyclohexane ring have been deuterated, and "5D - trihexyphenidyl", in which all five available hydrogens on the phenyl ring have been deuterated) were incubated with recombinant CYP2D6, CYP2C19, and CYP3A4 / CYP3A5 enzymes and human liver microsomes. The resulting metabolites were identified and quantified using a mass spectrometer. Urine samples from patients taking THP were also obtained and the metabolites were identified and quantified using a mass spectrometer.

[0066] Preliminary results: Incubation of THP with recombinant CYP450 enzymes revealed that CYP2D6 metabolism predominated at lower concentrations of THP (0.2 μg / ml), which shifted to CYP3A4 metabolism predominance at higher (supraphysiological) concentrations (6 μg / ml). Incubation of D11-THP confirmed hydroxylation of the cyclohexane ring by CYP2D6 and CYP3A4, yielding two, possibly three, different metabolites (two major, one minor), with the major metabolite having a MW of 238. Patient urine samples revealed mixed CYP2D6 and CYP3A4 metabolite formation, with CYP3A4 metabolites predominantly present in the urine of all patients, confirming the in vitro results.

[0067] Further results: Subsequent analysis using a larger panel of CYP450 enzymes provided more insights. Racemic trihexyphenidyl (20 ng / ml) was incubated with a panel of heterologously expressed human CYPs (XenoTech LLC), and metabolites with a molecular weight equivalent to that of trihexyphenidyl plus an additional 16 Da (consistent with the formation of hydroxylated metabolites) were separated by liquid chromatography using a chiral column (Restek Biphenyl, 1.8 μm, 100 x 2.1 mm) that could not resolve individual enantiomers, and the abundance of each metabolite was determined by tandem mass spectrometry (LC / MS / MS). Since the structure (position on the cyclohexane ring) of the metabolites remained to be established, these metabolites were named "Metabolite 1", "Metabolite 2", and "Metabolite 3", and the amount of metabolites formed was evaluated by integrating the elution peak areas in arbitrary area units. Under these experimental conditions, incubation of racemic THP with a larger panel of 12 recombinant CYPs revealed two major metabolites and one minor metabolite formed by three key CYPs, namely CYP2C19, CYP2D6, and CYP3A4, with minor contributions from CYP3A5 and CYP2C9 ( Figure 2 ). The contributions of the three key CYPs to in vitro metabolite formation were 51% CYP2C19, 43% CYP2D6, and 6% CYP3A4. Incubation of D11-THP with human liver microsomes confirmed that both metabolites were formed by hydroxylation of the cyclohexane ring. The same metabolites were present in patient urine and plasma samples, with Metabolite 1 predominating.

[0068] Conclusion: Biotransformation of THP occurs by hydroxylation of the cyclohexane ring, with hydroxylation mainly through the combined metabolism of CYP2C19, CYP2D6, and CYP3A4, and metabolites were confirmed to be present in the plasma and urine of all patients taking THP.

[0069] Example 2

[0070] Further analysis of enantiomers

[0071] Further analysis of THP identified differences in the enantiomers of THP. The binding affinity of the R-enantiomer was up to 525 times that of the S-enantiomer, and the R-enantiomer had selective affinity for human M1 and M4 muscarinic receptors, while the S-enantiomer had equal affinity for all receptor subtypes. In addition, our data revealed stereoselective metabolism of THP.

[0072] We performed in vitro incubations in which R-benzhexol (1,000 ng / ml) and S-benzhexol (1,000 ng / ml) were incubated with heterologously expressed CYP2C19, CYP2D6, and CYP3A4 and as for Figure 2 The separation of metabolites produced during the incubation was performed using a chiral column (Supelco Astec The hydroxylation metabolite of CYP generation is eluted from the column with two pairs or two peaks. One pair has an elution time of 10.8 and 11.2 minutes, and the second pair has a retention time of 12.0 and 12.9 minutes. The metabolite pair of earlier wash-out is called M1, wherein the peak (R-THP-M1) of 10.8 minutes is formed by R-benzhexol, and the metabolite (S-THP-M1) of 11.2 minutes wash-out is formed by S-benzhexol. Similarly, the peak of 12.0 minutes is called R-THP-M2, and the peak of 12.9 minutes is called S-THP-M2.

[0073] The data presented indicate that R-THP-M1 and S-THP-M2 are the most abundant metabolites formed under these experimental conditions, and that R-THP-M1 is almost entirely formed by CYP2C19, whereas S-THP-M2 is primarily formed by CYP2D6 ( Figure 3 ). Therefore, in patients who are poor CYP2D6 metabolizers, S-trihexyphenidyl accumulates to higher concentrations, potentially leading to an increased risk of side effects, while patients who are ultra-rapid CYP2C19 metabolizers may have lower levels of R-THP, resulting in reduced effectiveness of the drug. Based on this new understanding, it is proposed that the development of formulations enriched in or containing only R-trihexyphenidyl reduces or eliminates the potential toxicity associated with S-trihexyphenidyl and CYP2D6 genetic variation.

[0074] We investigated this by determining the effect of the genotype-predicted phenotype of CYP2D6 and CYP2C19 metabolizers on the concentrations of S-benzhephol and R-benzhephol metabolites present in patient plasma.Figure 4A- Small Figure 4F ) The results in Small Figure 4F demonstrate that the metabolite patterns in the three patients differed due to the CYP2C19 and CYP2D6 genotypes of the patients, the prescribed dose of racemic trihexyphenidyl, and the concurrent administration of a CYP2C19 activity inhibitor. In each Small Figure 4F , the disposition of S-trihexyphenidyl or R-trihexyphenidyl is shown by black circles, while the M1 metabolite concentration is indicated by gray circles, and the M2 metabolite concentration is indicated by white circles. Note that CYP2D6-dependent S-THP-M2 concentrations were not detected in Patient 2 (a CYP2D6 intermediate metabolizer predicted to have reduced CYP2D6 activity) or Patient 3 (a CYP2D6 poor metabolizer with no activity). Concentrations of the CYP3A4-dependent S-THP-M1 metabolite were present in all three patients and exceeded the concentration of S-trihexyphenidyl in Patients 1 and 2. For R-THP, the CYP2C19-dependent R-THP-M1 concentration was highest relative to the R-trihexyphenidyl plasma concentration in Patient 3, who had the normal metabolizer CYP2C19*1 / *1 genotype, and lowest relative to the R-trihexyphenidyl plasma concentration in Patient 1, who had the intermediate CYP2C19*1 / *2 genotype and was receiving the highest dose of the CYP2C19 inhibitor esomeprazole, 40 mg / day.

[0075] For the same three patients, the interindividual variability in CYP2C19- and CYP2D6-dependent trihexyphenidyl metabolism described in Figure 4 is presented in Figure 5. Steady-state concentrations of racemic trihexyphenidyl (black circles) and the two individual enantiomers (S-trihexyphenidyl (white circles) and R-trihexyphenidyl (grey circles)) were measured over the entire 6-hour dosing interval. Each patient was unique with respect to CYP2C19 and CYP2D6 genotypes, the prescribed dose of racemic trihexyphenidyl, and the concurrent administration of CYP2C19 activity inhibitors; each pair represents the results for an individual patient, with the respective genotype, racemic trihexyphenidyl dose, and inhibitor dose indicated above each column. In each pair, the left panel represents plasma concentrations of the prescribed actual dose, and the right panel represents the concentration-time curve corrected for a common dose of 0.1 mg / kg of racemic trihexyphenidyl. In other words, assuming linear kinetics, the right panel indicates the concentrations expected after dosing each patient with a 0.1 mg / kg dose. The shape of the curves is the same, but for Patients 1 and 2, the curves are shifted up two- and four-fold, respectively. The curve for Patient 3 is shifted down because the actual dose was higher than 0.1 mg / kg. The similarity of the racemic (black) and R-trihexyphenidyl (grey) disposition in Patients 1 (CYP2D6 normal metabolizer; NM) and 2 (CYP2D6 intermediate metabolizer; IM) indicates that most of the trihexyphenidyl present in the plasma of these patients is present as R-trihexyphenidyl. For Patient 3 (CYP2D6 poor metabolizer; PM), the S-trihexyphenidyl (white circles) concentration accounted for approximately 32% of the total trihexyphenidyl present, compared with 5%-6% for the other two patients. Put another way, the concentration of S-trihexyphenidyl in Patient 3 was approximately 50% of the concentration of R-trihexyphenidyl. In all patients, the concentration of R-trihexyphenidyl was greater than that of S-trihexyphenidyl, and in Patients 1 and 2, the concentration of R-trihexyphenidyl tended to decline more slowly because of the intermediate metabolizer CYP2C19 genotype and the presence of CYP2C19 activity inhibitors (esomeprazole and omeprazole), respectively.

[0076] These data suggest that THP is stereoselectively metabolized by hydroxylation of the cyclohexane ring, where in vitro R-THP is mainly metabolized by CYP2C19 and S-THP is mainly metabolized by CYP2D6. Collectively, these observations are consistent with CYP2C19 forming R-THP-M1 being the major pathway involved in R-trihexyphenidyl clearance (with reduced enzyme activity due to genetic variation and concurrent administration of inhibitors affecting the remaining enzyme activity), and CYP2D6-dependent formation of S-THP-M2 affecting reduced clearance, thus accumulating higher concentrations of S-trihexyphenidyl (possibly increasing the chance of drug adverse reactions).

[0077] Based on these preliminary results, we propose that R-benztropine will be superior to the racemic mixture because the R-enantiomer is more selective for the M1 and M4 muscarinic receptors, which are involved in dyskinesias, including dystonia, and more specifically, Parkinson's disease, cerebral palsy, and Angelman syndrome. The S-enantiomer is not selective for muscarinic subtypes and can actually cause side effects due to its interaction with M1-M5 and activation of peripheral muscarinic receptors, suggesting that the S-enantiomer may be associated with side effects, especially in CYP2D6 poor metabolizers. Administration of R-THP as a single enantiomer can be safer and more effective. The data also demonstrate that the R-enantiomer and S-enantiomer have different metabolic and clearance pathways (metabolized by different ADMERs); this observation can have important pharmacogenomic applications for the individualization of drug therapy, including adjusting dosing recommendations based on an individual's CYP2D6 and CYP2C19 metabolizer status.

Claims

1. A therapeutic composition comprising an enantiomerically enriched R-benztropine or a pharmaceutically acceptable salt thereof dispersed in a pharmaceutically acceptable carrier.

2. The composition according to claim 1, wherein the composition comprises R-benztropine with an enantiomeric excess of at least about 75%.

3. The composition according to claim 1, wherein the composition comprises R-benztropine with an enantiomeric excess of at least about 85%.

4. The composition according to claim 1, wherein the composition comprises R-benztropine with an enantiomeric excess of at least about 95%.

5. The composition according to claim 1, wherein the composition comprises R-benztropine with an enantiomeric excess of at least about 99%.

6. The composition according to claim 1, wherein the composition comprises less than 25% of S-benztropine.

7. The composition according to claim 1, wherein the R-benztropine is at least 95% enantiomerically pure.

8. The composition according to claim 1, wherein the R-benztropine is in a pharmaceutically acceptable salt form selected from hydrochloride, hydrobromide, acetate, benzoate, carbonate, mesylate, and bitartrate.

9. A pharmaceutical dosage form comprising a therapeutically effective amount of the composition according to claim 1.

10. The dosage form according to claim 9, wherein the dosage form is a tablet, capsule, or oral solution.

11. The dosage form according to claim 9, wherein the therapeutically effective amount is a dose of 3 mg / day to 30 mg / day.

12. A method of selectively targeting M1 and / or M4 muscarinic receptors in a subject in need thereof, the method comprising administering to the subject a therapeutically effective amount of an enantiomerically enriched R-benztropine or a pharmaceutically acceptable salt thereof, wherein the R-benztropine selectively binds to M1 and / or M4 in the subject.

13. The method according to claim 12, wherein an oral dosage form containing R-benztropine is administered, wherein the dosage form comprises R-benztropine with an enantiomeric excess of at least about 75%.

14. The method according to claim 13, wherein the dosage form contains purified R-benztropine and is more preferably substantially free of the S-benztropine enantiomer.

15. The method according to claim 13, wherein the dosage form is a tablet, capsule, or oral solution.

16. The method according to claim 13, the method comprising administering the R-benztropine at a dose of 3 mg / day to 30 mg / day.

17. The method according to claim 12, wherein after administration of the R-benztropine, the subject exhibits a decrease in the number, frequency, or severity of uncontrolled movements, spasms, or an improvement in the measurement of gross or fine motor function tasks.

18. Use of an agent for selectively targeting M1 and / or M4 muscarinic receptors in a subject in need thereof or for treating dystonia in a subject in need thereof, said agent comprising a therapeutic composition, said therapeutic composition comprising an enantiomerically enriched R-benztropine according to any one of claims 1-8 or a pharmaceutically acceptable salt thereof or a pharmaceutical dosage form according to any one of claims 9-11.

19. An improved method for treating dyskinesia in a subject in need thereof, said subject being a poor metabolizer of CYP2D6 or CYP3A4 / CYP3A5, said method comprising: obtaining the CYP450 metabolic phenotype of said subject, and administering to said subject a therapeutically effective amount of enantiomerically enriched R-benztropine or a pharmaceutically acceptable salt thereof, wherein said subject is a poor metabolizer of CYP2D6 or CYP3A4 / CYP3A5.

20. An improved method for treating dyskinesia in a subject in need thereof, said subject being a poor metabolizer of CYP2C19, said method comprising: obtaining the CYP450 metabolic phenotype of said subject, and administering to said subject a therapeutically effective amount of enantiomerically enriched R-benztropine or a pharmaceutically acceptable salt thereof, wherein said subject is a poor metabolizer of CYP2C19, and wherein said therapeutically effective amount is a low dose of said R-benztropine as compared to the dose recommended in the clinical guidelines regarding benztropine.

21. The method according to claim 20, wherein said low dose is half of the standard recommended dose, preferably wherein said low dose is from 3 mg / day to 15 mg / day.

22. An improved method for treating dyskinesia in a subject who is a poor metabolizer of CYP2D6 or CYP3A4 / CYP3A5 to minimize side effects, said method comprising: obtaining the CYP450 metabolic phenotype of said subject, and reducing the initial dose of a racemic mixture of benztropine or a racemic mixture of a pharmaceutically acceptable salt thereof to less than 1 mg / day and administering it to said subject, wherein said subject is a poor metabolizer of CYP2D6 or CYP3A4 / CYP3A5, or increasing the initial dose of a racemic mixture of benztropine or a racemic mixture of a pharmaceutically acceptable salt thereof to greater than 6 mg / day and administering it to said subject, wherein said subject is a normal or ultra-rapid metabolizer of CYP2D6 or CYP3A4 / CYP3A5, wherein said initial dose is based on the initial dose recommended in the clinical guidelines regarding benztropine.

23. A method for administering an initial dose of an M1 and / or M4 muscarinic receptor inhibitor to a subject in need thereof, said initial dose being based on the initial dose recommended in the clinical guidelines regarding said inhibitor, said method comprising: Obtain the genotype of a set of cytochrome P450 enzymes of the subject that at least includes CYP2D6 and / or CYP2C19 alleles, and assign a metabolic phenotype selected from poor metabolizer, intermediate metabolizer, or ultrarapid metabolizer to the subject for each enzyme based on the number of functional alleles of each cytochrome P450 gene; Administer an initial dose of the inhibitor to the patient, wherein the initial dose is: (a) If the metabolic phenotype is one or more of CYP2D6 poor metabolizer, CYP2D6 intermediate metabolizer, or CYP2C19 poor metabolizer, the initial dose is half of the initial dose recommended in the clinical guidelines; or (b) If the metabolic phenotype is one or more of CYP2D6 ultrarapid metabolizer or CYP2C19 ultrarapid metabolizer, the initial dose is the same as or higher than the initial dose recommended in the clinical guidelines; and wherein the inhibitor is selected from the racemic mixture of trihexyphenidyl, the enantiomerically enriched R-trihexyphenidyl, and its pharmaceutically acceptable salts.

24. A method for reducing side effects caused by an initial dose of an M1 and / or M4 muscarinic receptor inhibitor in a subject in need thereof, the initial dose being based on the initial dose recommended in the clinical guidelines regarding the inhibitor, the method comprises: Obtain the genotype of a set of cytochrome P450 that at least includes CYP2D6 alleles of the subject, and assign a metabolic phenotype selected from poor metabolizer, intermediate metabolizer, or ultrarapid metabolizer to the subject for each enzyme based on the number of functional alleles of CYP2D6; Administer an initial dose of the inhibitor to the patient, wherein the initial dose is: (a) If the metabolic phenotype is CYP2D6 poor metabolizer or CYP2D6 intermediate metabolizer, the initial dose is half of the initial dose recommended in the clinical guidelines; or (b) If the metabolic phenotype is CYP2D6 ultrarapid metabolizer, the initial dose is the same as or higher than the initial dose recommended in the clinical guidelines; and wherein the inhibitor is the racemic mixture of trihexyphenidyl or the racemic mixture of its pharmaceutically acceptable salts.

25. The method according to any one of claims 19 - 24, wherein the therapeutically effective amount or the initial dose amount is on a daily basis, and wherein the trihexyphenidyl or its pharmaceutically acceptable salt is administered once, twice, or three times a day to achieve the therapeutically effective amount or the initial dose amount per day.

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