TREATMENT OF RETT SYNDROME

Abstract

Rett syndrome (RTT), a childhood neurological disorder that affects primarily females, may be treated by use of a galanthamine analog wherein the hydroxy group of galantamine is replaced of a carbarnate, carbonate or ester group and the methoxy group may be replaced by another alkoxy group of from two to six carbon atoms, a hydroxy group, hydrogen, an alkanoyloxy group or 2 to 10 carbon atoms, a benzoyloxy or substituted benzoyloxy group, a carbonate group of 1 to 10 carbon atoms or a carbamate group such as a mono alkyl or dialkyl or an aryl carbamate wherein the alkyl grottos or aryl groups contain from 1 to 10 carbons; and the N-methyl group may be replaced by hydrogen, alkyl of 1 to 10 carbon atoms benzyl, cyclopropylmethyl group or a substituted or unsubstituted benzoyloxy group. Galantamine mon-alkylcarbarnates are particularly useful.

Claims

1. A method for treating patients with Rett Syndrome which comprises administering to a patient in need thereof a therapeutically effective dose of a galanthamine analog wherein the hydroxy group is replaced by a carbamate, carbonate or ester group the methoxy group is optionally replaced by another alkoxy group of from two to six carbon atoms, a hydroxy group, hydrogen, an alkanoyloxy group or 2 to 10 carbon atoms, a benzoyloxy or substituted benzoyloxy group, a carbonate group of 1 to 10 carbon atoms or a carbamate group such as a mono alkyl or dialkyl or an aryl carbamate wherein the alkyl groups or aryl groups contain from 1 to 10 carbons; and the N-methyl group is optionally replaced by hydrogen, alkyl of 1 to 10 carbon atoms, benzyl, cyclopropylmelhyl group or a substituted or unsubstituted benzoyloxy group.

2. A method as claimed in claim 1, wherein the hydroxyl group of galantamine is replaced by an alkanoyloxy group or 2 to 10 carbon atoms, a benzoyloxy or substituted benzoyloxy group, a carbonate group of 1 to 10 carbon atoms or a carbamate group such as a mono alkyl or dialkyl or an aryl carbamate wherein the alkyl groups or aryl groups contain from 1 to 10 carbons.

3. A method as claimed in claim 1, wherein the hydroxy group of galantamine is replaced by a mono alkyl carbamate group of 2 to 8 carbon atoms.

4. A method as claimed in claim 3, wherein the hydroxy group of galantamine is replaced by an n-butyl carbamate group.

5. A method as claimed in claim 1, wherein the methoxy and methyl groups of galantamine are unchanged.

6. A method as claimed in claim 4, wherein the methoxy and methyl groups of galantamine are unchanged.

7. A method as claimed in claim 1, wherein the dose of a galantamine analog is from 0.2 to 100 mg.

8. A method as claimed in claim 4 wherein n-butyl carbamate is administered in dosages of 1 to 10 mg, or 2 to 25 mg, or 5 to 40 mg per dose.

9. A method as claimed in claim 1, wherein the galantamine analog is administered as an oral dosage form in which the particles of the galaniamine analogre coated so as to delay release into the blood stream by coating with a pharmaceutically acceptable polymer that is dissolved in gastric juices.

Description

SUMMARY OF THE INVENTION

[0020] From the first aspect the present invention provides a method treatment of patients with Rett syndrome which comprises administering thereto a therapeutically acceptable dose of a galantamine analog wherein the hydroxy group is replaced by a carbamate, carbonate or ester group and the methoxy group may be replaced by another alkoxy group of from two to six carbon atoms, a hydroxy group, hydrogen, an alkanoyloxy group or 2 to 10 carbon atoms, a benzoyloxy or substituted benzoyloxy group, a carbonate group of 1 to 10 carbon atoms or a carbamate group such as a mono alkyl or dialkyl or an aryl carbamate wherein the alkyl groups or aryl groups contain from 1 to 10 carbons; and the N-methyl group may be replaced by hydrogen, alkyl of 1 to 10 carbon atoms, benzyl, cyclopropylmethyl group or a substituted or unsubstituted benzoyloxy group.

[0021] Typically the group used to replace the hydroxyl group will be an alkanoyloxy group or 2 to 10 carbon atoms, a benzoyloxy or substituted benzoyloxy group, a carbonate group of 1 to 10 carbon atoms or a carbamate group such as a mono alkyl or dialkyl or an aryl carbamate wherein the alkyl groups or aryl groups contain from 1 to 10 carbons. Ester and carbamate groups are particularly useful. Commonly, the methoxy and methyl groups of galantamine will be left unchanged. Mono alkyl carbamates of 2 to 8 carbon atoms may be particularly useful.

[0022] One particularly useful compound is the n-butylcarbamate derivative of galantamine, having the structure:

##STR00002##

[0023] The IC.sub.50 for galantane n-butylcarbamate is 10.910.sup.7 M as compared to 3.9710.sup.7 M for galantamine.

[0024] This compound was first described in Han et al as a cholinesterase inhibitor in Bioorg. & Medicinal Chemistry Letters 1, 11 579-580 (1991).

[0025] The butylcarbamate differed from galantamine in adverse effects. (Han et al, Eur J Med Chem 1992, 27, 673) Decreased motility which appeared at 5 mg/kg in galantamine-treated animals was not observed up to30 mg/kg of the analog. At doses of 50-100 mg/kg of the n-butylcarbamate, mice were wobbly and off-balance with rapid heart rate still present at 4 hours, but were recovered at 24 hours. There was no lethality up to 100 mg/kg. The LD50 of galantamine is 10 mg/kg. Mice injected IP with 10, 15 and 20 mg/kg galantamine develop seizures at an average of 8, 6 and 4 minutes respectively (Fonck et al, J Neurosci 2003, 23, 7, 2582).

[0026] Galantamine n-butylcarbarmate is predicted to have 80% oral bioavailability, based on in vitro permeability of a layer of CaCo-2 cells, derived from a human colorectal carcinoma, as shown below.

TABLE-US-00001 Assay mean A->B test conc duration P.sub.app.sup.a Client ID (M) (hr) (10.sup.6 cm s.sup.1) comment Ranitidine 50 2 1.1 low permeability control Warfarin 50 2 34.7 high permeability control Galanthamine 50 2 20.8 Carbamate .sup.aApparent permeability

[0027] In an in-vitro preparation of liver microsomes, the half-life of galantamine n-butylcarbamate was greater than 60 minutes.

[0028] Galantamine n-butylcarbamate, based on animal and in-vitro studies, appears to be well tolerated, safe, orally bioavailable, stable in plasma, and effective in enhancing learning at lower doses than galantamine. It enhances neuronal electrophysiological activity via the galantamine positive allosteric modulatory site on nicotinic receptors.

[0029] Diagnosis of Patients For Treatment by the Present Invention May be Effected by Clinical Examination and Genetic Testing.

[0030] RTT is invariably associated with a genetic defect in the MEM gene and treatment may be useful for patients who have been determined to have such a mutation even if no clinical symptoms are displayed.

[0031] Compositions suitable for use in treatments according to the invention are typically suitable for oral administration such as tablets, capsules, or lozenges containing from 0.1 to 40 mg. of the active compound depending upon the activity and half-life of the compound. Compositions using the butylcarbamate will typically contain, for example in the range 1 to 10 mg, or 2 to 25 mg, or 5 to 40 mg per dose.

[0032] Oral dosage forms may be sustained dosage formulations in which the particles of the active compound are coated so as to delay release into the blood stream for example by coating with a pharmaceutically acceptable polymer that is dissolved in gastric juices such as polyvinyl pyrrolidone and then sizing the particles and incorporating specific ratios of particles of particular sizes into a tablet, capsule or lozenge so that particles having different degrees of thickness of coating are released at different times. In the present case, the coating technique will desirably result in most of the active compound being released within twelve hours of administration. Alternative means of application may include for example transdermal patches in which case the objective is to provide administration of a dosage at a rate of . . . to 0.01 to 10 mg per hour.

[0033] Other dosage forms may be used if desired. For example nasal or parenteral including dosage formulations to assist passage of the blood-brain barrier.

[0034] For the purpose of nasal or parenteral therapeutic administration, the active compounds of the invention may be incorporated into a solution or suspension. These preparations typically contain at least 0.1% of active compound, for example between 0.5 and about 30% of the weight thereof. Preferred compositions and preparations according to the present inventions are prepared so that a nasal or parenteral dosage unit contains between 0.1 to 10 milligrams of active compound.

[0035] The solutions or suspensions may also include the following components: a sterile diluent such as water for infection, saline solution, fixed oils, polyethylene glycols, glycerine, propylene glycol or other synthetic solvents; antibacterial agents, such as benzyl alcohol or methyl parabens; antioxidants such as ascorbic acid or sodium bisulfite; chelating agents such as ethylene-diamine tetraacetic acid; buffers such as acetates; citrates or phosphates and agents for the adjustment of tonicity such as sodium chloride or dextrose. Parenteral multiple dose vials may be of glass or plastic.

[0036] Typical dosage rates in administration of the active ingredients depend on the nature of the compound that is used and in intravenous administration are in the range of 0.01 to 2.0 mg per day and per kilogram of body weight based on the physical condition and other medications of the patient.

[0037] Liquid formulations for nasal or intra-cerebroventricular administration at a concentration of 0.1 to 5 mg of active ingredient/ml. The compounds according to the invention can also be administered by a transdermal system, in which 0.1 to 10 mg/day is released. A transdermal dosage system may consist of a storage layer that contains 0.1 to 30 mg of the active substance as a free base of salt, in case together with a penetration accelerator, e.g., dimenyl sulfoxide, or a carboxylic acid, e.g., octanoic acid, and a realistic-looking polyacrylate, e.g., hexylacrylate/vinyl acetate/acrylic acid copolymer including softeners, e.g., isopropylmyristate. As a covering, an active ingredient-impermeable outside layer, e.g., a metal-coated, siliconized polyethylene patch with a thickness of for example, 0.35 mm, can be used. To produce an adhesive layer, e.g., a dimethytarnino-methacrylaternethacrylate copolymer in an organic solvent can be used.

[0038] The determination of a particular dose for any given patient will be a matter for the judgment of the physician treating the patient. However, suitable dosages may be determined by starting with a low dose and increasing if there is insufficient response.

[0039] As noted above, these dosages may be considerably lower than the typical 0.2 to 100 mg, such as 0.2 to 10 mg, or 1 to 50 mg.

[0040] Cognitive deficits are particularly resistant to amelioration in RTT and in animal models of RYE Given galantamine butyl carbamate's ability to enhance cognitive performance in mice, and its potential to stimulate nicotinic receptors, which are reduced in RTT [Yasui 2011], it is likely to ameliorate the cognitive deficits in this disorder. Potentiation of nicotinic receptors facilitates release of a number of different neurotransmitters including dopamine, glutamate, and GABA. Given that dopaminergic neurotransmission is decreased in RTT and that abnormal functioning of MeCP2 in GABAergic neurons alone recapitulates most RTT symptoms, administration of galantamine butyl carbamate has the potential to improve the clinical outcome of RTT girls by enhancing synaptic function in cholinergic, dopaminergic, and GABAergic pathways.

[0041] Potentiation of nicotinic receptors facilitates release of a number of different neurotransmitters including dopamine, glutamate, and GABA. Given that dopaminergic neurotransmission is decreased in RTT and that abnormal functioning of MeCP2 in GABAergic neurons alone recapitulates most RTT symptoms, administration of galantamine butyl carbamate has the potential to improve the clinical outcome of RTT girls by enhancing synaptic function in cholinergic, dopaminergic, and GABAergic pathways.

[0042] Compositions suitable for use in treatments according to the invention are typically suitable for oral administration such as tablets, capsules, or lozenges containing from 0.1 to 40 mg. of the active compound depending upon the activity and half-life of the compound. Compositions using the butylcarbamate will typically contain, for example in the range 1 to 10 mg, or 2 to 25 mg, or 5 to 40 mg per dose.

[0043] Oral dosage forms may be sustained dosage formulations in which the particles of the active compound are coated so as to delay release into the blood stream for example by coating with a pharmaceutically acceptable polymer that is dissolved in gastric juices such as polyvinyl pyrrolidone and then sizing the particles and incorporating specific ratios of particles of particular sizes into a tablet, capsule or lozenge so that particles having different degrees of thickness of coating are released at different times. In the present case, the coating technique will desirably result in most of the active compound being released within twelve hours of administration. Alternative means of application may include for example transdermal patches in which case the objective is to provide administration of a dosage at a rate of 0.01 to 10 mg per hour.

[0044] Other dosage forms may be used if desired. For example nasal or parenteral including dosage formulations to assist passage of the blood-brain barrier.

[0045] For the purpose of nasal or parenteral therapeutic administration, the active compounds of the invention may be incorporated into a solution or suspension. These preparations typically contain at least 0.1% of active compound, for example between 0.5 and about 30% of the weight thereof. Preferred compositions and preparations according to the present inventions are prepared so that a nasal or parenteral dosage unit contains between 0.1 to 10 milligrams of active compound.

[0046] The solutions or suspensions may also include the following components: a sterile diluent such as water for injection, saline solution, fixed oils, polyethylene glycols, glycerine, propylene glycol or other synthetic solvents; antibacterial agents, such as benzyl alcohol or methyl parabens; antioxidants such as ascorbic acid or sodium bisulfite; chelating agents such as ethylene-diamine tetraacetic acid; buffers such as acetates; citrates or phosphates and agents for the adjustment of tonicity such as sodium chloride or dextrose. Parenteral multiple dose vials may be of glass or plastic.

[0047] Typical dosage rates in administration of the active ingredients depend on the nature of the compound that is used and in intravenous administration are in the range of 0.01 to 2.0 mg per day and per kilogram of body weight based on the physical condition and other medications of the patient.

[0048] Liquid formulations for nasal or intra-cerebroventricular administration at a concentration of 0.1 to 5 mg of active ingredient/ml. The compounds according to the invention can also be administered by a transdermal system, in which 0.1 to 10 mg/day is released. A transdermal dosage system may consist of a storage layer that contains 0.1 to 30 mg of the active substance as a free base of salt, in case together with a penetration accelerator, e.g., dimenyl sulfoxide, or a carboxylic acid, e.g., octanoic acid, and a realistic-looking polyacrylate, e.g., hexylacrylate/vinyl acetate/acrylic acid copolymer including softeners, e.g., isopropylmyristate. As a covering, an active ingredient-impermeable outside layer, e.g., a metal-coated, siliconized polyethylene patch with a thickness of, for example, 0.35 mm, can be used. To produce an adhesive layer, e.g., a dimethylamino-methacrylate/methacrylate copolymer in an organic solvent can be used.

[0049] The determination of a particular dose for any given patient will be a matter for the judgment of the physician treating the patient. However, suitable dosages may be determined by starting with a low dose and increasing if there is insufficient response. As noted above, these dosages may be considerably lower than the typical 0.2 to 100 mg, such as 0.2 to 10 mg, or 1 to 50 mg with appropriate adjustment for body weight if the patient is not an adult.

[0050] The Mecp2 R168X and Mecp2J mouse models of RTT are excellent animal model in which to test the efficacy of galantamine n-butylcarbamate in Rett Syndrome. R168X is the most common point mutation in humans, and the Mecp2J mouse model is a deletion mutation. These mouse models exhibit phenotypes that are highly reminiscent of the human condition [Stearns 2007 PMID: 17383101]. Using both male and female mutant mice on a battery of behavioral and physiological tasks, as described previously [in Stearns 2007 PMID: 17383101] will allow us assess the preclinical potential of this compound, including an assessment of the efficacy of galantamine n-butylcarbamate in acute and chronic dosing schemes to improve the RTT-related phenotype. Suggested guidelines for preclinical trials in RTT [Katz 2012 PMID: 23115203] outline the methodologies, protocols, and rigorous standards to ensure that preclinical experiments in mouse models of RTT are likely to translate into clinical success.

[0051] Galantamine n-butylcarbamate affects cardiac and motor functions at very high doses (50 and 100 mg/kg). These negative side effects could be especially detrimental in WIT girls who have cardiac abnormalities and pronounced motoric impairments. Because the cholinergic system (which is modulated by galantamine n-butylcarbamate) affects both motor and respiratory functions, we monitored locomotor and respiratory functions in response to the drug treatment. In order to assess cognitive function in response to the drug treatment, we used a novel object recognition task because this task is one of the most consistent tasks in which female Mecp2 mice show significant deficits (Stearns et al. 2007 Neuroscience 146: 907-921 PMID 17383101; Katz, Berger-Sweeney et al., 2012 Disease Model Mech 5: 733-45. PMID 23115203).

[0052] Locomotor activity was monitored using methods described previously (Shaevitz et al. 2013 Genes Brain Behav. 12(7): 732-40. doi: 1111111./gbb,12070). Mecp2 mutant males (between 1 and 3 months old) and females (between 3 and 6 months old) and age-matched controls were monitored for one-hour prior to and 12 hours after drug (or vehicle: 20% DMSO in saline) administration (one set of mice received IP injections and one set of mice received oral gavage) in doses that ranged from 0.1-20 mg/kg). Activity was measured across the 12-h dark cycle using a photobeam activity system (San Diego Instruments, San Diego, Calif., USA). Mice were placed individually into a cage (472521 cm) inside a rectangular arena equipped with a 38 array of photobeams. The average number of ambulatory (two adjacent) and fine (repeated single) beam breaks per hour over the 12 h was compared. [N=2 mice/group at each dose and each administration route; for the vehicle controls, N=6 WT/group; N=6 Mecp2/group]. Data were analyzed using repeated measures analysis of variance.

[0053] Respiratory function was monitored in a plethysmograph (EMKA Technologies) for 30 minutes prior to and 1 hour after drug administration (one set of mice received IP injections and one set of mice received oral gavage). [N=2 mice/group at each dose and each administration route; for the vehicle controls, N=6 WT/group; N=6 Mecp2/group]. Data were analyzed using repeated measures analysis of variance.

[0054] Doses of the drug that did not impair motor or respiratory functions were then considered to be safe and well tolerated.

[0055] Cognitive function was assessed using the novel object recognition (NOR) task using methods previously described (Schaevitz et al. 2013). Female mice were tested because best practice suggests that pre-clinical trials of drugs should emphasize results in female models given that RTT is most prevalent in girls (Katz, Berger-Sweeney et al., 2012 Disease Model Mech. 5:733-45. PMD: 23115203). Novel object memory was assessed. during three sessions. This task relies on the innate tendency of a mouse to explore unfamiliar objects vs. familiar objects. Testing was performed in an open-field arena. Twenty-four hours prior to training, mice were habituated to the arena for 10 min. Ninety minutes before training, the mice were administered drug or vehicle (0.1, 0.5, 1.0, 2.5 and 5.0 mg/kg IP). During training, mice were given 10 min to explore two identical Lego Objects (A +A). Short- and long-term object memory were assessed in two subsequent sessions (24 h after the completion of training) during which mice were given 10 min to explore the familiar (A) or a novel (B or C) object. The duration of exploration (defined as the mouse's snout or forelimbs physically touching or approaching within 1 cm of an object) of familiar and novel objects was measured. The amount of time spent exploring the novel object over the total time exploring both novel and familiar objects in each session was used to measure object memory. [N==6/dose of 0.1, 0.5 and 1.0; N=1/dose of 2.5 and 5.0 mg/kg; for vehicle N=6 WT and N=6 Mecp2 mice.] Given the small number of mice tested at each dose, we combined mice into groups of Mecp2 or controls, and vehicle or drug-treated Mecp2 mice and analyzed data the using Chi-squared analyses to determine whether there were differences amongst group of those that learned the NOR task and those that did not.

Results

[0056] Ambulatory and fine motor movements were not significant altered at any of the doses of the drug tested. We have shown previously (Schaevitz et al. 2013) that ambulatory movements in Mecp2 males is significantly lower than in wildtype mice; in Mecp2 females were also significantly lower than wildtype, but the impairment was milder. Doses of the drug (administered either IP or by gavage between 0.1 and 20 mg/kg) did not impair locomotor activity in the Mecp2 mice of either sex. Also, the same doses and administration routes of the drug did not affect respiratory activity. Therefore, the drug was safe and well tolerated at doses between 0.1 and 20 mg/kg in Mecp2 mice of both sexes, as well as controls.

[0057] For the novel Objection recognition task data, we created a matrix of all wildtype and. Mecp2 females who were administered the vehicle and a second matrix comparing Mecp2 females with and without the drug (all doses combined). Mice were divided into two categories: those who learned the novel object task (had object recognition scores above chance level >0.5) and those that did not learn the novel object task (had object recognition scores at or below chance levels 0.5). We asked two questions: [0058] 1) Do the Mecp2 females (administered vehicle) perform significantly worse than WT controls on the task?

TABLE-US-00002 NOR scores = or below 0.5 NOR scores above 0.5 Mecp2 83% 17% WT 33% 67% The wildtype mice learned the NOR task but the Mecp2 mice did not learn the task [Chi square, (df = 1, N = 12) = 6.75, p = 0.0094]. [0059] 2) Does galantamine n-butylcarbamate improve performance in the Mecp2 mice on the task?

TABLE-US-00003 NOR scores = or below 0.5 NOR scores above 0.5 Mecp2 83% 17% (Vehicle) Mecp2 65% 35% (drugs) The Mecp2 mice treated with galantamine n-butylcarbamate learned the NOR task significantly better than vehicle-injected Mecp2 mice [Chi square, (df = 1, N = 12) = 4.592, p = 0.0321].

[0060] Therefore, our data show that galantamine n-butylcarbamate improves memory for a novel object and cognitive performance in a female mouse model of RTT syndrome at doses that do not impair locomotor activity or respiratory functions.