Use of glutamate 2b receptor antagonists and sigma receptor agonsists as antitussives

Cross-Reference to Related Applications

This application claims the benefits of priority to United States Provisional Patent Application No. 62/926,871, filed October 28, 2019, entitled COMPOSITIONS AND METHODS FOR TREATING COUGH, and United States Provisional Patent Application No. 62/943,537, filed December 4, 2019, entitled COMPOSITIONS AND METHODS FOR TREATING A COUGH, the contents of which are hereby expressly incorporated into the present application by reference in their entirety.

Field of Invention

[0001] The present invention relates to the use of compounds for treating a cough, and in particular, the use of glutamate 2b receptor antagonists such as Ifenprodil and Radiprodil for treating a cough.

Background

[0002] A cough, also referred to as tussis, is a sudden, protective expulsion of air from the lungs that is usually accompanied by a sound. Coughing can be irregular, such as when it occurs to help clear the breathing passages from fluids, irritants, such as air pollution, and/or foreign particles. However, coughing can become repetitive and frequent, which may indicate the presence of a disease, such as a respiratory tract infection or mild bronchitis. Coughing may also be chronic, lasting over several weeks, which may be associated with a more serious underlying medical condition, such as asthma, gastroesophageal reflux disease, nonasthmatic eosinophilic bronchitis, and upper-airway cough syndrome. [0003] A chronic (Persistent) cough is a cough lasting eight weeks or longer in adults, or four weeks in children. Chronic cough can interrupt sleep, cause exhaustion and in severe cases can cause serious vomiting, light-headedness and rib fractures.

[0004] A dry, non-productive cough is a very common symptom of IPF. At least 70%-85% of patients with IPF have a dry cough, which can often get worse on exertion.

[0005] According to a recent report from Research and Markets, in the United States, cough is the most common complaint for which patients seek medical attention and is the second most common reason for a general medical examination, accounting for more than 26 million office visits annually.

[0006] There is currently no known cure for the cough. Conventional treatments tend to focus on easing the symptoms. Such treatment includes home remedies, such as drinking fluids with honey, over-the-counter expectorant medication, and cough suppressants.

[0007] The present invention provides a novel use of existing drugs, typically studied and used as potential therapies for other pathologies, for the treatment and/or alleviation of a cough.

Summary of Invention

[0008] In an embodiment of the invention, a glutamate 2b receptor (Glut2B or GluN2B) antagonist for the treatment or prophylaxis of a cough in a subject. The Glut2B antagonist may be one or more of Ifenprodil, Radiprodil, Traxoprodil, Rislenmdaz, Eliprodil, Ro-25-6981, and BMT-108908, EVT-101, CPlOl-606, MK- 0657, EVT-103, and AZD 6765 (Annual Reports in Medicinal Chemistry (2012) Volume 47: 94-103). Brief DescriDtion of the Figures

[0009] Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.

[00010] Figure 1 is a schematic showing causation and central nervous system receptors and glutamate 2b receptor antagonist relationship with cough.

[00011] Figure 2 is a schematic showing ion channel, receptors and glutamate 2b receptor antagonists relationships.

[00012] Figure 3 is a bar graph summarizing the total number of coughs from groups of guinea pigs in a study during a 10 minute exposure and 5 minute recovery period to citric acid or saline, following treatment with Gefapixant or Ifenprodil, as compared with a vehicle group.

[00013] Figure 4 is a bar graph summarizing the onset of first cough from groups of guinea pigs in a study during a 10 minute exposure and 5 minute recovery period to citric acid or saline, following treatment with Gefapixant or Ifenprodil, as compared with a vehicle group.

Detailed Description

[00014] The inventor has found certain pharmacologic compounds, approved for use in other pathologies, are useful in the prophylaxis and/or treatment of a cough. [00015] Based on the description herein, it is shown that the compounds described are useful in the prophylaxis and/or treatment of a cough. An anti-tussive effect was found when the compounds described herein were given to histamine exposed conscious guinea pigs with citric acid.

[00016] One currently used therapy for alleviating cough symptoms is administering the pharmacologic compound Gefapixant, which was used as a positive control in the experimental examples described herein.

[00017] Gefapixant, C14H19N5O4S, is a non-narcotic, selective antagonist of the P2X3 receptor. Recent studies have demonstrated that its application may have some efficacy in patients with chronic cough. Further trials are being conducted to further evaluate the efficacy and safety of Gefapixant in the control of cough in patients with chronic cough. The chemical structure of Gefapixant is:

[00018] The present specification shows the effects of inhibiting or alleviating a cough by administering a therapeutically effective amount of Ifenprodil, Radiprodil, and other glutamate 2b receptor antagonists. These compounds described herein are existing drugs, typically known for treatment of non-pulmonary related conditions.

[00019] The rational behind their efficacy in alleviating or preventing coughing includes the fact that the glutamate receptor and sigma receptor 1 are targets of the above noted compounds. As well, Memantine, a non-specific NMDA inhibitor, has also shown preclinical and clinical efficacy.

Use of Ifenprodil

[00020] Ifenprodil, 4-[2-(4-benzylpiperidin-l-ium-l-yl)-l-hydroxypropyl] phenol; 2,3,4-trihydroxy-4-oxobutanoate, is known in the art as a selective is an N- methyl-d-aspartate (NMDA) receptor glutamate receptor antagonist specifically targeting the NMDA-type subunit 2B (Glu2NB). Ifenprodil also exhibits agonist activity for the Sigma-1 receptor, a chaperone protein up-regulated during endoplasmic reticulum stress. Ifenprodil was originally (in the early 1970's) developed as a vasodilator. Ifenprodil is currently being studied for treatment of adolescent PTSD. The chemical structure is:

[00021] In some embodiments tested in the examples herein, Ifenprodil hemitartrate having the following structure was used: [00022] In one aspect, the present invention provides a use and method of treatment or prophylaxis of a cough in a subject with Ifenprodil or a pharmaceutically acceptable variation thereof.

[00023] In an embodiment, the amount of Ifenprodil used is between 0.6 and 5 mg per kg of the subject per day. In a preferred embodiment, the amount of Ifenprodil used is between 0.8 to 3 mg per kg of the subject per day. In a further preferred embodiment, the amount of Ifenprodil used is about 1.5 mg per kg of the subject per day.

[00024] The Ifenprodil, or pharmaceutically acceptable variation thereof, may be administered to the subject orally, intravenously or in a manner known in the art. The Ifenprodil, or pharmaceutically acceptable variation thereof, may also be administered with one or more pharmaceutically acceptable excipients.

Use of Radiprodil

[00025] Radiprodil, 2-[4-[(4-fluorophenyl)methyl]piperidin-l-yl]-2-oxo-N-(2- oxo-3H-l,3-benzoxazol-6-yl)acetamide, is known in the art as an NMDA receptor antagonist. It has been used in trials studying the treatment of Infantile Spasms (IS) and Diabetic Peripheral Neuropathic Pain. The chemical structure of Radiprodil is:

[00026] In one aspect, the present invention provides a use and method of treatment or prophylaxis of a cough in a subject with Radiprodil or a pharmaceutically acceptable variation thereof. [00027] In an embodiment, the amount of Radiprodil used is between 1.6 and 3.3 mg per kg of the subject per day. In a preferred embodiment, the amount of Radiprodil used is about 2.5 mg per kg of the subject per day. In a further preferred embodiment, the amount of Radiprodil used is about 2.25 mg per kg of the subject par day.

[00028] The Radiprodil, or pharmaceutically acceptable variation thereof, may be administered to the subject orally, intravenously or in a manner known in the art. The Radiprodil, or pharmaceutically acceptable variation thereof, may also be administered with one or more pharmaceutically acceptable excipients.

Use of Glutamate 2b Receptor Antagonists

[00029] In an embodiment of the invention, a glutamate 2b receptor (Glut2B or GluN2B) antagonist for the treatment or prophylaxis of a cough in a subject. The Glut2B antagonist may be one or more of Ifenprodil, Radiprodil, Traxoprodil, Rislenmdaz, Eliprodil, Ro-25-6981, and BMT-108908, EVT-101, CPlOl-606, MK- 0657, EVT-103, and AZD 6765 (Annual Reports in Medicinal Chemistry (2012) Volume 47: 94-103).

[00030] In another aspect of the invention, ifenprodil is a known to exhibit NDMA receptor antagonism (GluNl and more specifically GlunN2B subunits) and sigma receptor agonist (more specifically subtype 1) activity. Sigma receptors are intracellular chaperones that reside in the endoplasmic reticulum of a cell. Thus, molecules with similar activity have anti-fibrotic effects and treat IPF. IPF may present with or without cough. Previous studies of ifenprodil and IPF used a mouse bleomycin model. As mice have no cough reflex, nothing was known regarding the effect, if any, of ifenprodil on coughing. Representative sigma receptor agonists include selective serotonin reuptake inhibitors (SSRI) such as fluvoxamine, fluoxetine, excitalpram and donepezil (J. Pharmacological Sciences (2015) 127:6-

9).

Use in Combination

[00031] In another aspect, the present invention provides a use and method of treatment or prophylaxis of a cough in a subject with one or more of Ifenprodil, Radiprodil, Traxoprodil, Rislenmdaz, Eliprodil, Ro-25-6981, and BMT-108908, EVT- 101, CPlOl-606, MK-0657, EVT-103, and AZD 6765, in combination. In another aspect, the present invention provides a use and method of treatment or prophylaxis of a cough in a subject with one or more of Ifenprodil, Radiprodil, Traxoprodil, Rislenmdaz, Eliprodil, Ro-25-6981, and BMT-108908, EVT-101, CP101- 606, MK-0657, EVT-103, and AZD 6765, in combination with one or more of Dexamethasone, pirfenidone and nintedanib.

[00032] The term "therapeutically effective amount" used herein refers to the amount of an active ingredient sufficient to confer a desired prophylactic or therapeutic effect in a treated subject. In some embodiments, the effective amount is determined, for example, based on the administration route and frequency, body weight and species of the subject receiving the pharmacologic compound.

[00033] In some embodiments, an effective amount of the pharmacologic compound is formulated with a pharmaceutically acceptable vehicle and administered to the subject. The term "pharmaceutically acceptable" used herein means that the vehicle is known in the art as compatible with the pharmacologic compound while also being safe to the subject receiving the treatment. In some embodiments, the pharmaceutically acceptable vehicle is determined by persons skilled in the art evaluating, for example, the solubility of the pharmacologic compound in said vehicle. [00034] Embodiments of the present invention are further described with reference to the following examples, which are intended to be illustrative and not limiting in nature.

Example - Materials and Methods

[00035] The guinea pig species used in one study was twenty four Male Dunkin Hartley guinea pigs, each weighing between 300 and 350g, which were supplied by Marshall Bioresources Ltd, UK.

[00036] The guinea pigs were housed in pens (11125 cm ² ) on arrival with a 12 hour light/dark cycle. Room temperature and humidity were maintained within home office guidelines (17-24 C and 40-70% respectively). Environmental enrichment were also provided in all pens. The guinea pigs were given access to standard chow ad libitum. Water was also made available from bottles ad libitum. An acclimatization period of 7 days was allowed before the start of experimental procedures.

[00037] The animals were observed once daily in the morning throughout the study. During the treatment period, the animals were observed every 15-30 min. Any animals showing signs of being unwell beyond the limits of the UK home office project licence, were culled and the sponsor monitor was informed.

[00038] The following guidelines (provided by the UK Home Office) were used to assess non-specific or unexpected adverse effects in the animals undergoing regulated procedures in this study. They relate to either the procedure, test compound, or control drug dosing. Animals showing two or more of any of the following limiting clinical signs in the category equivalent to the protocol severity limit were removed from the study and euthanized using a schedule 1 method (usually cervical dislocation) at the establishment. Where an animal reached the limit of either, or both, of the first two signs with or without any other signs, that animal was removed from the study and killed by a schedule 1 method at the establishment. Animals exposed to severe fight injuries were also removed from the study and killed by a schedule 1 method at the establishment.

[00039] The limiting clinical signs include:

• Body weight loss greater than 20% of the highest measured individual body weight.

• Food and water consumption less than 40% of normal for 3 days or anorexia (total inappetence for 72 hrs).

• Marked piloerection with other signs of dehydration such as skin tenting.

• Unresponsive to activity and provocation.

• Hunched persistently (frozen).

• Distressed- persistent vocalization.

• Oculo-nasal discharge persistent and copious.

• Laboured respiration.

• Persistent tremors.

• Persistent convulsions.

[00040] In this study, no animals were removed due to fight injuries or the above severity limits being exceeded.

[00041] A test compound, Ifenprodil, and Gefapixant (in powder form) were prepared and formulated by initially adding 100% propylene glycol at the required volume for the final treatment buffer. The additional buffer ingredients were added in a stepwise fashion, initially solutol and then captisol. Each ingredient was added in a volume equivalent to that which is required for the final volume of treatment buffer for the stock formulation. [00042] In particular, for Gefapixant, this was 0.7 mg/mL, a concentration that delivers 3.5 mg/Kg in a dose volume of 5 mL/Kg. For Ifenprodil, this was 0.3 mg/mL, a concentration that delivers 1.5 mg/Kg in a dose volume of 5 mL/Kg.

[00043] Prior to the addition of each buffer ingredient, the test compound formulations were sonicated for 15 min using a Branson 1510 Sonicator.

Afterwards, the initial formulation of the test compound and Gefapixant were diluted with a prepared buffer vehicle to provide additional dosing formulations.

This was 0.01 to 0.2 mg/ml, preferably 0.06 mg/mL, a dose that delivers 0.3 mg/Kg in a dose volume of 5 mL/Kg.

[00044] The final test compound buffer vehicle comprised of 10:10:80 mix of propylene glycol : 20% Solutol in PBS : 5% Captisol in PBS.

[00045] The vehicle was formulated by adding 20% Solutol in PBS to 100% propylene gycol followed by adding 5% Capitisol in PBS. The final vehicle preparation was a 10:10:80 mix of propylene glycol, 20% Solutol and 5% Captisol. Thus, in every 1 mL of vehicle, there will be O.lmL of 100% propylene glycol, 0.1 mL of 20% Solutol and 0.8 mL of 5% Captiosol.

[00046] All final test and control formulations were sonicated for 30 min prior to dosing to generate an even suspension or to ensure that the formulation had visibly dissolved.

[00047] The animals were first pre-treated (5 mL/Kg, p.o.) with the vehicle, the test compound, or Gefapixant prior to tussive agent (citric acid) exposure, using the amounts set out in Table 1 below. In each case, the route of administration of the treatment was oral.

[00048] Table 1

[00049] Animals receiving Gefapixant (3.5 mg/Kg) were dosed 2 hours prior to tussive agent exposure. Animals receiving Ifenprodil (1.5 mg/Kg) were dosed 30 minutes prior to tussive agent exposure.

[00050] 10 min prior to the tussive evaluation, each animal was individually placed into a purpose built exposure chamber with a supplied airflow through a nebuliser of 2 L/min, and allowed to settle into its new environment.

[00051] Following the acclimatisation period, each animal was then exposed for 10 min to an aerosol of 1M citric acid using an ultrasonic nebuliser (Aerogen) set at a nominal liquid consumption rate of 0.6 mb/min.

[00052] Coughs and sneezes elicited during the 10 minute aerosol of 1M citric acid, and a subsequent 5 minute observation period, were recorded manually to monitor the animal's welfare. This data also served to provide a back-up data set to that obtained from the airflow pressure changes that were recorded on a data acquisition system (Powerlab), which was used to ensure accurate differentiation between coughs and sneezes. The data was analysed for onset of cough, cough numbers and frequency, and sneezes. [00053] At the end of each experiment, the animals were immediately euthanized with overdose to pentobarbitone.

[00054] The following measurements and assessments were taken for each guinea pig:

• Mean total number of coughs evoked in each treatment group

• Mean onset of first cough in each group

• Mean number of coughs per minute during citric acid exposure in each treatment group

[00055] Inter-group deviations were statistically analyzed by a one-way analysis of variance (ANOVA). In the case of significant difference in the mean values among the different levels of treatment, comparisons versus the citric acid vehicle group were carried out using the Dunnett's test. p< 0.05 was considered statistically significant.

Results

[00056] Total Number of Coughs

[00057] Figure 3 summarizes the total number of coughs from guinea pigs during the 10 minute exposure and 5 minute recovery period to citric acid (1M) or saline, following treatment with Gefapixant (3.5 mg/Kg, p.o.) Ifenprodil (1.5 mg/Kg, p.o.) or vehicle (5 mL/Kg, p.o.).

[00058] Each column represents the mean and the vertical bars the s.e. mean (n = 6 per group). Total cough numbers in test compound treated animals were compared to the vehicle control animals that received citric acid exposure (*), using ANOVA followed by Dunnett's post hoc test, where *P<0.05, **P<0.01. [00059] The raw data is set out in Appendix A below. The vehicle group had an average of 29.5 coughs per animal. The group treated with Gefapixant had an average of 23.67 coughs per animal. Notably, the group treated with Ifenprodil had an average of 17.17 coughs per animal.

[00060] Onset of First Cough

[00061] Figure 4 summarizes the amount of time for the onset of first coughs from the guinea pigs during a 10 minute exposure and 5 minute recovery period to citric acid (1M) or saline, following treatment with Gefapixant (3.5 mg/Kg, p.o.) Ifenprodil (1.5 mg/Kg, p.o.) or vehicle (5 mL/Kg, p.o.).

[00062] Each column represents the mean and the vertical bars the s.e. mean (n = 6 per group). Onsets of first cough in test compound treated animals were compared to the vehicle control animals that received citric acid exposure (*), using ANOVA followed by Dunnett's post hoc test.

[00063] The raw data is set out in Appendix A below. The first onset of cough in the vehicle group was 34.2 seconds. The first onset of cough in the group treated with Gefapixant was 49.7 seconds. Notably, the first onset of cough in the group treated with Ifenprodil was 59.8 seconds.

[00064] Total Number of Sneezes

[00065] The raw data is set out in Appendix B below. The vehicle group had an average of 5.17 sneezes per animal. The group treated with Gefapixant had an average of 3.17 sneezes per animal. The group treated with Ifenprodil had an average of 3.33 sneezes per animal.

Conclusions [00066] In conclusion, oral administration of Radiprodil, and/or other glutamate 2b receptor antagonists, and especially Ifenprodil, shows efficacy in preventing and/or alleviating coughing.

[00067] In particular, Ifenprodil (1.5 mg/kg) showed a reduction of 42% in mean cough frequency vs untreated control (p <0.01). Gefapixant (3.5 mg/kg) showed a 20% reduction in mean cough frequency vs untreated control (p <0.05). Ifenprodil (59.8 seconds) and Gefapixant (49.7 seconds) both showed a delay in the onset of the first cough when compared to control (34.2 seconds).

[00068] Throughout the following description, specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense.

[00069] While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are consistent with the broadest interpretation of the specification as a whole.

Appendix A



ADDendix B