WO2009024324A2 - Treatment of sleep disorders - Google Patents

Abstract

The use of 7-chloro-3-(5-methylaminomethyl-[1,2,4]oxadiazol-3-yl)-5-methyl-4,5-dihydro-imidazo[l,5-a][1,4]benzodiazepine-6-one and/or 7-chloro-3-(5-dimethylaminomethyl-[1,2,4]oxadiazol-3-yl)-5-methyl-4,5-dihydro-imidazo[1,5- a][l,4]benzodiazepine-6-one, or their pharmaceuticallyacceptable salts, for treating various types of insomnia.

Description

TITLE

TREATMENT OF SLEEP DISORDERS

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] Insomnia is one of the most common complaints in general medical practice. Approximately 10% to 15% of adults suffer from chronic insomnia and an additional 25% to 35% have transient or short-term insomnia. Chronic insomnia is typically accepted to involve episodes greater than three (3) weeks in duration. Transient insomnia is an insomnia that is present for one to several days, and is less than one week in duration. Short-term insomnia is an insomnia of one to three weeks in duration (Roth, Int. J. Clin. Pract. 2001; (Suppl.):3-8). [0002] Generally, as discussed in detail by Russell P. Rosenberg in "Sleep Maintenance Insomnia: Strengths and Weaknesses of Current Pharmacologic Therapies," Annals of Clinical Psychiatry, 18[l]:49-56, 2006, which is incorporated herein by reference, patients with insomnia are also categorized according to when their sleep difficulty most often occurs. The three recognized categories of insomnia are (1) sleep onset insomnia (difficulty in falling asleep); (2) sleep maintenance insomnia (difficulty staying asleep); and (3) terminal insomnia (early-morning awakenings coupled with an inability to return to sleep). Terminal insomnia is sometimes referred to as sleep offset insomnia. These symptoms may occur singly or in combination, as is the case in many patients with chronic insomnia, which may result from several different etiologies. Patients often have several sleep complaints simultaneously and experience a gamut of sleep disturbances, including prolonged latency to sleep onset, increased time awake during the sleep period and reduced total sleep time.

[0003] There are various medications that have been used to treat insomnia. The early type of insomnia drugs are what have come to be known as classic benzodiazepines. These benzodiazepines exert their pharmacological actions by interacting with the benzodiazepine binding sites associated with the GABA_A receptor. GABA_A receptors are ligand-gated ion channels, and functional receptors are made up from combinations of different subunit proteins. Subunits are divided in three main classes of alpha (α), beta (β) and gamma (γ) subunits. GABAA receptors that have a benzodiazepine binding site are formed from either cxi, (X₂, (X₃ or as subunits in combination with β and 7₂ subunits (Paul J. Whiting, DDT Vol. 8, No. 10, May 2003).

[0004] The important allosteric modulatory effects of drugs acting at the benzodiazepine site were recognized early and the distribution of activities at different receptor subtypes has been an area of intense pharmacological discovery. Agonists that act at the benzodiazepine site are known to exhibit anxiolytic, sedative, and hypnotic effects. However, while some classic benzodiazepines, which are considered full agonists at the GABA_A receptor benzodiazepine site, are generally regarded as being effective at inducing and maintaining sleep, which is believed to be due to their relatively long half-lives ranging from 10-40 hours, they were found to produce undesirable residual effects. These may include cognitive impairment, excessive sedation, ataxia, potentiation of ethanol effects and a tendency for tolerance and drug dependence. A particular problem with classic benzodiazepines is rebound insomnia, manifested by restlessness and somnipathy, which emerges on withdrawal. Furthermore, the quality of sleep that is induced by these compounds is unphysiological. Classic benzodiazepines typically reduce slow wave sleep (SWS), rapid eye movement (REM) sleep and generally adversely affect sleep architecture. One of the reasons for these undesirable side effects was deemed to be associated with the afore-mentioned relatively long half-life of the classic benzodiazepines.

[0005] In order to overcome these problems, agents with shorter half-lives have been investigated. Examples of such agents include the so-called non- benzodiazepines, such as Zolpidem and zaleplon, that also act as full agonists at the GABA_A receptor benzodiazepine site. However, while these newer agents are generally effective in reducing time to sleep onset (i.e., decreasing sleep latency), they have been found to be less effective at improving sleep maintenance, as well as treating terminal insomnia.

[0006] Sleep maintenance difficulties can be quantified using Polysomnography (PSG). When quantifying sleep maintenance difficulties via PSG, wake after sleep onset (WASO) and number of awakenings (NAW) are the most commonly utilized parameters. WASO is a robust measure of sleep maintenance, as it represents the total amount of time spent awake after the onset of persistent sleep measured over a fixed 8-hour period in bed (captures total duration of lost sleep after at least 1 awakening), while NAW represents only the number of wake periods lasting at least 1 minute occurring after the onset of persistent sleep. Therefore, a person may wake only once during the night (NAW), but may spend 3 hours awake (WASO), so the latter measure more closely reflects the level of disturbance. [0007] Difficulty with maintaining sleep is common in patients with medical and psychiatric disorders, as well as in patients with primary insomnia, and it occurs with more frequency than sleep onset problems in certain population groups. However, it is widely recognized that currently used medications fall short when it comes to safely and effectively addressing sleep maintenance problems. [0008] An additional problem with conventionally known insomnia agents concerns the elderly population (at least 65 years old). The elderly insomnia population represents an important and underserved patient population. Sleep maintenance and terminal insomnia are more prevalent in the elderly population compared to younger patient populations (McCaIl et al. 2005; National Sleep Foundation, Sleep in America Poll 2005). Metabolism of many existing drugs for insomnia shows significant changes with age and so may necessitate a dose adjustment for elderly patients (McCaIl et al 2005). In the case of Zolpidem (Ambien ®) and modified release Zolpidem (zolpidem-MR; Ambien CR ®), indicated doses for the elderly (65 and over) are half those of non-elderly adults (18-64) due to increased exposure in the elderly. In the case of eszopiclone (Lunesta ®), there is prolonged elimination with the half-life increasing from 6 hours in non-elderly adults to 9 hours in the elderly. Such an increase in half-life raises the likelihood of accumulation and carry-over effects after repeat dosing in the elderly. Furthermore, these changes in metabolism with age are gradual and vary between individuals. Therefore, it is more difficult to select an appropriate dose of drugs undergoing metabolism that is sensitive to age-related changes.

SUMMARY OF THE INVENTION

[0009] The present invention provides an effective method for treating sleep maintenance insomnia and/or terminal insomnia, each of which can be associated with transient, short-term, chronic, primary and secondary insomnia. Specifically, the present invention provides a method for decreasing wake after sleep onset (WASO), increasing total sleep time (TST), reducing total wake time, particularly in the second half of the night, and/or reducing early-morning awakenings. Also, the present invention improves daytime function in the elderly. One or more of these advantages can be achieved while reducing latency to sleep onset and/or latency to persistent sleep, thus also effectively treating sleep onset insomnia. Accordingly, the present invention provides an effective compound for treating various types of insomnia, including insomnia in the elderly population. [0010] In one embodiment, the compound is 7-chloro-3-(5-methylaminomethyl- [l,2,4]oxadiazol-3-yl)-5-methyl-4,5-dihydro-imidazo[l,5-a][l,4]benzodiazepine-6- one, which is represented by formula (I) below, or a pharmaceutically acceptable salt thereof:

(I)

[0011] In particular, in one aspect, the present invention provides a use of a compound of formula (I) or a pharmaceutically acceptable salt thereof in the preparation of a medicament for any of treating maintenance insomnia and/or terminal insomnia, as well as sleep onset insomnia, each of which can be associated with transient, short-term, chronic, primary and secondary insomnia by, for example, decreasing wake after sleep onset (WASO), increasing total sleep time (TST), reducing total wake time, particularly in the second half of the night, and/or reducing early-morning awakenings.

[0012] Preferably, the present invention provides a use of a compound of formula (I) or a pharmaceutically acceptable salt thereof in the preparation of a medicament for increasing total sleep time in a period from about four to about eight hours, more preferably from about five to about eight hours, yet more preferably from about six to about eight hours after the administration of the medicament. The start and end of this period are measured from the administration of the effective amount of the medicament or from the administration of a partial amount, presuming that dosing of the effective amount of the medicament is completed. [0013] Preferably, the present invention provides a use of a compound of formula (I) or a pharmaceutically acceptable salt thereof in the preparation of a medicament for decreasing wake after sleep onset in a period from about four to about eight hours, more preferably from about five to about eight hours, yet more preferably from about six to about eight hours after the administration of the medicament. The start and end of this period are measured from the administration of the effective amount of the medicament or from the administration of a partial amount, presuming that dosing of the effective amount of the medicament is completed. [0014] Preferably, the amount of the compound of formula (I) or its pharmaceutically acceptable salt that is administered for the treatment is from about 1 mg to about 20 mg, preferably from about 1.5 mg to about 20 mg. [0015] In another aspect of the present invention, the present invention provides a use of a compound of formula (I) in combination with 7-chloro-3-(5- dimethyiaminomethyi-[ 1 ,2,4]oxadiazol-3-yl)-5-methyl-4,5-dihydro-imidazo[ 1 ,5- a][l,4]benzodiazepine-6-one, which is represented by formula (EI) below, or a pharmaceutically acceptable salt thereof

[0016] The subjects to be treated in accordance with the present invention are humans.

[0017] As used herein, "adults" are humans who are at least 18 years old. The "non-elderly" are adult humans who are 18 to 64 years old. The "elderly" are adult humans who are at least 65 years old.

[0018] As used herein, "primary insomnia" is sleeplessness that is not attributable to a medical, psychiatric, or environmental cause. The diagnostic criteria for primary insomnia may be found in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), which is incorporated herein by reference. [0019] As used herein, "secondary insomnia" is insomnia in which a specific medical, psychiatric, or environmental condition can be identified as the cause of the sleep problem. [0020] Transient insomnia is an insomnia that is present for one to several days, and is less than one week in duration. Short-term insomnia is an insomnia of one to three weeks in duration. Chronic insomnia is typically accepted to involve episodes greater than three (3) weeks in duration. (Roth, Int. J. Clin. Pract. 2001; (Suppl.):3-

8).

[0021] Sleep onset or onset insomnia is insomnia, which is characterized by difficulty in falling asleep. Maintenance insomnia is insomnia, which is characterized by difficulty staying asleep. Terminal or offset insomnia is insomnia, which is characterized by early-morning awakenings coupled with an inability to return to sleep.

[0022] As used herein, latency to persistent sleep (LPS) is defined as the time from

"lights out" to the beginning of 10 uninterrupted minutes of sleep.

[0023] Persistent sleep is defined as 10 uninterrupted minutes of sleep after initial sleep onset.

[0024] Wake after sleep onset (WASO) is defined as the total amount of time spent awake after the onset of persistent sleep measured over a fixed 8-hour period in bed

(captures total duration of lost sleep after at least 1 awakening). "sWASO" refers to the subjective WASO as reported by individuals.

[0025] Total wake time (TWT) is defined as the total amount of time spent awake measured over a specific period of time.

[0026] Number of awakenings (NAW) is defined as the return to an awake state

(number of wake periods lasting at least 1 minute occurring after the onset of persistent sleep). "sNAW" refers to the subjective NAW as reported by individuals.

[0027] Total sleep time (TST) is defined as the total time asleep measured over a fixed 8-hour period. "sTST" refers to the subjective TST as reported by individuals.

[0028] Sleep efficiency index is a ratio of TST to total time in bed, i.e., a percentage of time spent asleep. Total time in bed is typically 8 hours for study purposes.

[0029] Sleep architecture refers to the changes in the stages of sleep during the sleep period. Typically, in healthy humans, sleep stages occur in cycles lasting about 90 to about 120 minutes each. Four to five such cycles occur during a typical night of sleep. During the first half of the night, the healthy individual typically passes from wakefulness briefly into stage I sleep and then to stages II, III, and IV. Stages π and III reappear, after which rapid eye movement (REM) sleep is observed for the first time. During the second half of the night, stage II and REM sleep alternate.

[0030J Slow wave sleep (SWS) is stage HI and IV sleep. It is characterized by a transition to an electroencephalogram (EEG) with high amplitude delta EEG waves (1.5 to 3 Hz).

[0031] As used herein, AUC is the area under the drug plasma concentration versus time curve from time zero to infinity. C_max is the maximum observed plasma concentration of the drug from time zero to infinity.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Fig. 1 is a plot showing concentration-dependent stimulation of currents elicited by GABA (EC3-s) by the compound of formula (II) at αiβ₂Y₂,

0C₃β₂γ₂ and

GABAA receptors expressed in Xenopus oocytes. Data is shown as mean ± SEM.

[0033] Fig. 2 is a plot showing concentration-dependent stimulation of currents elicited by GABA (Eds) by the compound of formula (II) at αiβ₂Y₂, 0^₂7₂, 0^₂7₂ and

GABA_A receptors expressed in Xenopus oocytes. Stimulation is standardized to the one observed using 1 μM diazepam in the same batch of oocytes. Data is shown as mean ± SEM.

[0034] Fig. 3 is a plot showing a concentration-dependent stimulation of currents elicited by GABA (EC₃.₅) by the compound of formula (I) at αiβ₂Y₂, 0^₂7₂, 0^₂7₂ and

GABA_A receptors expressed in Xenopus oocytes. Data is shown as mean ± SEM.

[0035] Fig. 4 is a plot showing concentration-dependent stimulation of currents elicited by GABA (EC₃.₅) by the compound of formula (I) at 0:^₂7₂, (^₂7₂, α₃β₂γ₂ and

GABA_A receptors expressed in Xenopus oocytes. Stimulation is standardized to the one observed using 1 μM diazepam in the same batch of oocytes. Data is shown as mean ± SEM. [0036] Fig. 5 is a plot showing concentration-dependent stimulation of currents elicited by GABA (EC_3-5) by Zolpidem at αiβ₂γ2, Ot₂P₂ ¹Yi, α₃β₂γ₂ and α₅β₂γ₂

GABA_A receptors expressed in Xenopus oocytes. Data is shown as mean ± SEM.

[0037] Fig. 6 is a plot showing concentration-dependent stimulation of currents elicited by GABA (EC_3-S) by Zolpidem at αiβ₂γ₂, α₂β₂γ., α₃β₂γ₂ and αsβrø

GABA_A receptors expressed in Xenopus oocytes. Stimulation is standardized to the one observed using 1 μM diazepam in the same batch of oocytes. Data is shown as mean ± SEM.

[0038] Fig. 7 shows the results of a model of the potentiation of the response mediated by GABA_A αi-containing receptors over time for the compound of formula (I) based on measured or predicted plasma concentrations following oral administration of doses of 1 mg, 2.5 mg, 8 mg, 10 mg and 25 mg and for the compound of formula (II) following oral administration of a 1 mg dose in human volunteers (x-axis = time in hours; y-axis = % potentiation of response mediated by cti containing GABAA receptor subtype).

[0039] Fig. 8 shows the study design used in Example 3.

[0040] Fig. 9 is a chart showing LPS in Example 3.

[0041] Fig. 10 is a chart showing TST in Example 3.

[0042] Fig. 11 is a chart showing WASO in Example 3.

[0043] Fig. 12 is a chart showing WASO in the first and second halves of the night in Example 3.

[0044] Fig. 13 is a chart showing the percent reduction (vs. placebo) in WASO in

Example 3.

[0045] Fig. 14 is a chart showing TWT for each hour of the night in Example 3.

[0046] Figs. 15 and 16 are charts showing patient reported sleep quality in

Example 3.

[0047] Fig. 17 is a chart showing sleep architecture in accordance with Example 3.

[0048] Fig. 18 is a chart showing patient reported residual sedation effects in accordance with Example 3.

[0049] Fig. 19 shows the study design used in Example 4.

[0050] Fig. 20 is a chart showing PSG-derived TST (average of nights 1, 6 & 7) in

Example 4. [0051] Fig. 21 is a chart showing PSG-derived LPS in Example 4.

[0052] Fig. 22 is a chart showing WASO (over the whole night, i.e., 0-8 hours) in

Example 4.

[0053] Fig. 23 is a chart showing WASO in the second half of the night (5-8 hours after "lights out") in Example 4.

[0054] Fig. 24 is a chart showing TWT hour by hour in Example 4.

[0055] Fig. 25 is a chart showing average sleep latency over all timepoints tested

(2, 4, 6, 8 & 10 hours post wake time) in Example 4 using the Multiple Sleep

Latency Test (MSLT).

[0056] Fig. 26 is a chart showing subjective sleep quality based on the adjusted probability of good/very good sleep quality in Example 4.

[0057] Fig. 27 shows subject-reported sleep quality during night 1 in accordance with the study in Example 4.

[0058] Fig. 28 is a chart showing subjective (subject-reported) sleep onset latency

(adjusted mean sleep onset latency across all 7 nights) in Example 4.

[0059] Fig. 29 is a chart showing subjective (subject-reported) TST (adjusted mean sTST across all 7 nights) in Example 4.

[0060] Fig. 30 is a chart showing subjective (subject-reported) WASO (sWASO)

(mean sWASO across all 7 nights dosing) in Example 4.

[0061] Fig. 31 shows cumulative adjusted probabilities for patient-reported residual effects in Example 4.

[0062] Fig. 32 is a chart showing an exemplary pharmacokinetic (PK) profile of the compound of formula (II) (free base) in both the non-elderly adults and the elderly. Mean dose adjusted plasma concentrations of the compound of formula

(II) (free base) in non-elderly (open circle) and elderly males (open square) and Ml

(active metabolite of the compound of formula (II) (free base)) in non-elderly adults (filled circle) and the elderly (filled square). Ml corresponds to the compound of formula (I). DETAILED DESCRIPTION OF THE INVENTION

[0063] One of the major challenges in treating insomnia is to develop a drag that induces sleep quickly, helps individuals remain asleep and allows them to awaken feeling refreshed rather than hung over. Furthermore, with respect to the elderly, there is an additional challenge to develop a drag with a metabolism that is largely unaffected by the aging process.

[0064] The present invention addresses one or both of these challenges. In particular, the present invention provides a use of a compound of formula (I) or a pharmaceutically acceptable salt thereof with or without the compound of formula (II) or a pharmaceutically acceptable salt thereof in preparation of a medicament for treating the sleep onset, maintenance and/or terminal insomnia by, for example, decreasing wake after sleep onset (WASO), increasing total sleep time (TST). reducing total wake time (TWT), particularly in the second half of the night, and/or reducing early-morning awakenings, in a human in need thereof:

(I) (H)

[0065] An effective amount of the compound of formula (I) or its pharmaceutically acceptable salt, optionally together with the compound of formula (II) or its pharmaceutically acceptable salt, is administered to the patient in need of the treatment.

[0066] The compound of formula (II) can be prepared in accordance with the methods described in U.S. 6,391,873, which is incorporated herein by reference. This compound has been disclosed as useful for treating acute and chronic anxiety disorders. [0067] As disclosed in U.S. Patent No. 5,665,718, this type of compound is deemed to display sedative activity that sets in very rapidly, but lasts only a relatively short period of time. Accordingly, the compound of formula (II) or a pharmaceutically acceptable salt thereof would not be expected to be beneficial in the treatments of maintenance and terminal insomnia, much more so in the elderly who are generally expected to react differently than other adults to insomnia medication.

[0068] Nonetheless, the compound of formula (II) or a pharmaceutically acceptable salt thereof was surprisingly found to be effective for treatment of not only sleep onset insomnia, but also maintenance insomnia and terminal insomnia in humans, including the elderly, even when the administration amount was significantly low, on the order of about 0.5 mg to about 5 mg, particularly from about 1.5 mg to about 2.5 mg. The surprising nature of these results is further supported by the finding that the compound of formula (II) has a relatively short half-life of about 3-4 hours, akin to the conventional insomnia treatment agents having relatively short half-lives, which were found lacking effectiveness in sleep maintenance. The efficacy of the compound of formula (II) for the treatment of various types of insomnia was not found to be improved when the administration amount exceeded about 5 mg, and residual sedation effects were noted at higher doses in non-elderly adults. Conventional insomnia agents, such as Zolpidem, trazodone and zaleplon, were found to be less than effective for treating maintenance and terminal insomnia even when administered in amounts that are at least twice that of the compound of formula (II) or a pharmaceutically acceptable salt thereof.

[0069] One of the metabolites of the compound of formula (II), which metabolite has now been found to be active, is 7-chloro-3-(5-methylaminomethyl- [ 1 ,2,4]oxadiazol-3-yl)-5-methyl-4,5-dihydro-imidazo[ 1 ,5-a][l ,4]benzodiazepine-6- one, which is represented by formula (I):

(I)

[0070] The compound (I) can also be manufactured, for instance, according to the following reaction scheme:

[0071] Reaction conditions for the synthesis are described in Preparation Example

1.

[0072] U.S. Patent No. 5,665,718 discloses that a class of compounds that includes the compound of formula (I) can be used to treat various anxiety disorders. In accordance with the present invention, this compound can be used to treat various types of insomnia, including onset, maintenance and terminal insomnia associated with transient, chronic, primary and secondary insomnia. [0073] Pharmaceutically acceptable salts for either compound of formula (I) or (II) can be prepared by standard techniques that will be familiar to the person skilled in the art. Suitable pharmaceutically acceptable salts are acid addition salts, such as those with inorganic or organic acids. Examples of these salts are the hydrochlorides, hydrobromides, sulfates, nitrates, citrates, acetates, maleates, succinates, methanesulphonates, p-toluenesulphonates and the like. [0074] The compounds of formulas (I) and (II), or their respective pharmaceutically acceptable salts, achieve their sedative effects by positive allosteric modulation of GABA_A receptors via the benzodiazepine site. However, unlike conventional agents for treating insomnia that act at the benzodiazepine site, the compounds of formulas (I) and (II), or their respective pharmaceutically acceptable salts, are only partial agonists, i.e., they produce a lower maximum potentiation of the GABA_A receptor. Thus, unexpectedly, it was found that even a partial agonist can be used for the treatment of maintenance and terminal insomnia. Furthermore, surprisingly, the compound of formula (I) or a pharmaceutically acceptable salt thereof, with or without the compound of formula (II) or a pharmaceutically acceptable salt thereof, can be used to treat insomnia in the elderly within the same dosage range as needed for other adults and improved daytime function for the elderly who suffer from daytime sleepiness. [0075] The ability to allosterically stimulate currents elicited by GABA (EC_3-5) was determined for compound of formula (I), compound of formula (II), Zolpidem and diazepam at the rat GABA_A receptors of the subunit composition (Xip₂Y₂, α3β2Y2 and a₅p2Y2. 7-Chloro-3-(5-dimethylaminomethyl-[l,2,4]oxadiazol-3- yl)-5methyl-4,5-dihydro-imidazol[l,5,-a][l,4]benzodiazepine-6-one was used to test the effects of the compound of formula (II):

(II)

[0076] Similar procedures were chosen as for the investigation of other GABA_A receptor subunit specific substances (e.g., Baur et al., 2005; MoI. Pharmacol. 68, 787-792).

Expression in Xenopus oocytes

[0077] Lobes of the ovary containing the follicles were obtained by surgical procedures from female Xenopus laevis. Follicles were singled out using a platinum loop. Fifty nL of cRNA solution at a ratio of O_x : β₂ : γ₂ of 1 : 1 : 5 (3.3 - 1O nM a_x (X = 1,2,3,5); 3.3 - 10 nM β₂; 16.7 - 50 nM γ₂) (Boileau et al., 2002; Neuropharmacology 43, 695-700) were microinjected into Xenopus follicles. Several hours after microinjection the follicles were freed of follicular layers and adhering connective tissue by a collagenase / hypertonic shock procedure (Sigel, 1987; J. Physiol.(Land) 386, 73-90). Oocytes were kept at constant 18°C until measurement (1 - 4 days) in a modified Barth solution (88 mM NaCl, 1 mM KCl, 2.4 mM NaHCO₃, 10 mM Hepes-NaOH (pH 7.5), 0.82 mM MgSO₄ x 7H₂O, 0.34 mM Ca(NO₃)₂ x 4H₂O, 0.4ImM CaCl₂ x 2H₂O, 100 U Penicillin/mL, 100 μg Streptomycin/mL, sterile filtered).

Electrophysiological investigation

[0078] Currents were measured using a home-built amplifier in combination with a xy-recorder or were digitized using a MacLab/200 (AD Instruments) and stored on a computer. Xenopus oocytes were voltage clamped using the two-electrode voltage clamp technique (electrode resistance about 0.8 MΩ) at -80 mV. The medium contained 90 mM NaCl, 1 mM KCl, 1 mM MgCl₂, 1 mM CaCl₂, 10 mM Na-Hepes (pH 7.4) and 0.5% DMSO.

[0079] GABA was applied for 20-50 seconds without or in combination with other drugs and a washout period of 4 minutes was allowed to ensure full recovery from desensitization, which was experimentally determined. The perfusion solution (6 mL/min) was applied through a glass capillary with an inner diameter of 1.35 mm, the mouth of which was placed about 0.4 mm from the surface of the oocyte. The rate of solution change under our conditions has been estimated 70 % within less than 0.5 s (Sigel et al., 1990; Neuron 5, 703-711). The entire perfusion system and the assay chamber were cleaned between drug applications by washing with DMSO.

Data handling

[0080] Data is given as mean ± SD, except in the figures where data is shown for clarity as mean ± SEM. Current stimulation was calculated as follows: stimulation (%) = ( ( I(GABA+moduiator) - I(GABA) ) / 1(GABA) ) x 100 %, where I is the current amplitude. Where indicated, the stimulation was standardized to the stimulation by 1 μM diazepam (100%). To obtain Figs. 1-6, values for current stimulation obtained at a given concentration of modulator at a given subunit combination were averaged. The data points were fitted with the equation stimulation = efficacy / ( I + (potency / concentration of modulator)). The values given in the Tables (Summary) are obtained by fitting individual curves and subsequently averaging efficacy and potency.

RESULTS

Compound of Formula (II)

[0081] GABA (EC₃-₅) was applied to an oocyte expressing αiβ₂γ₂ GABA_A receptors several times until the current response was stable. The GABA (EC_3-5 ) refers to the effective concentration of GABA, which produces a response that is 3- 5% of the maximal response to high concentrations of GABA. Such a low concentration of GABA is chosen in order to better see the potentiating effect of positive allosteric modulators. [0082] GABA was then applied in combination with various concentrations of the compound of formula (II) between 0.3 nM and 3,000 nM to produce a cumulative concentration response curve. This resulted in a concentration-dependent potentiation of the GABA response as plotted in Figs. 1 and 2. In each batch of oocytes the stimulation by 1 μM diazepam was determined in five oocytes, extent of stimulation averaged and defined as 100 %. Where indicated, stimulation by the compound of formula (II) in each batch of oocytes was expressed as a percentage of this value in the corresponding batch.

[0083] Concentration response curves were also performed with oocytes expressing 0^₂7₂, c^₂Y₂, or α₅β₂Y₂, after establishing the optimal concentration range as indicated above. The compound of formula (II) performed as a partial positive allosteric modulator. At concentrations < 100 nM, the compound of formula (II) showed preference for ctifayi GABAA receptors in comparison to 0t5β2Y2, (Xaβ∑γ. and

Fig. 1 shows the dose dependent stimulation of currents elicited by GABA at (Xiβ∑γ., α₂β2γ2, ct3β₂γ2, and

before and Fig. 2 after standardization to the stimulation by 1 μM diazepam (100%). Averaged data of the individual curves summarizing the effects of the compound of formula (II) are shown below for unstandardized and standardized stimulation.

Table 1 : Summary for Compound of Formula (II)

Receptor Potency Efficacy Standardized Efficacy αiβ₂γ₂ 18 ± 6 nM (n = 4) 123 ± 19 % (n = 4) 62 ± 10 % (n = 4) α₂β₂γ2 62 ± 21 nM (n = 5) 90 ± 16 % (n = 5) 31 ± 6 % (n = 5) α₃β₂γ2 84 ± 15 nM (n = 5) 171 ± 33 % (n = 5) 41 ± 8 % (n = 5) α₅β₂Y2 53 ± 6 nM (n = 5) 135 ± 16 % (n = 5) 69 ± 23 % (n = 5)

Compound of Formula (I)

[0084] GABA (EC₃.₅) was applied to an oocyte expressing a$₂Y₂ GABA_A receptors several times until the current response was stable. Subsequently, GABA was then applied in combination with various concentrations of the compound of formula (I) between 3 nM and 3,000 nM to produce a cumulative concentration response curve. Concentration response curves were performed twice with the same batch of oocytes and twice with an independent batch of oocytes. [0085] In each batch of oocytes the stimulation by 1 μM diazepam was determined in five oocytes, extent of stimulation averaged and defined as 100 %. Where indicated, stimulation by the compound of formula (I) in each batch of oocytes was expressed as percentage of this value in the corresponding batch. [0086] Concentration response curves were also performed with oocytes expressing Ct₂β₂7₂, ^₂7₂, or 0^₂7₂, after establishing the optimal concentration range as indicated above. The compound of formula (I) performed as a weak partial positive aiiosteric modulator. At concentrations < 50 nM, the compound of formula (I) showed preference for αiβ272 and

GABA_A receptors in comparison to

and

Fig. 3 shows the dose dependent stimulation of currents elicited by GABA at αiβ2γ2, Ctøβ∑T., 0C3β272, ^and

before and Fig. 4 after standardization to the stimulation by 1 μM diazepam (100%). Averaged data of the individual curves summarizing the effects by the compound of formula (I) are shown below for unstandardized and standardized stimulation.

Table 2: Summary for the Compound of Formula (I) (n = 5 each) Receptor Potency Efficacy Standardized Efficacy αiβ₂72 19 ± 8 nM 55 ± 5 % 27 ± 5 % α₂β₂72 59 ± 21 nM 49 ± 9 % 17 ± 3 % α₃β₂72 66 ± 14 nM 87 ± 19 % 21 ± 5 % α₅β₂72 31 ± 4 nM 78 ± 6 % 39 ± 11 %

Zolpidem

[0087] GABA (EC3.5) was applied to an oocyte expressing 0Ciβ₂7₂ GABA_A receptors several times until the current response was stable. Subsequently, GABA was applied in combination with various concentrations of Zolpidem between 1 and 10,000 nM. Concentration response curves were performed twice with the same batch of oocytes and twice with an independent batch of oocytes.

[0088] In each batch of oocytes the stimulation by 1 μM diazepam was determined in five oocytes, extent of stimulation averaged and defined as 100%. Where indicated, stimulation by Zolpidem in each batch of oocytes was expressed as percentage of this value in the corresponding batch. [0089] Concentration response curves were also performed with oocytes expressing

ct₃p2Y2, ^or

As expected, Zolpidem showed a higher affinity at <Xiβ2γ2 GABA_A receptors in comparison to

^an<i

Fig. 3 shows the dose dependent stimulation of currents elicited by GABA at <Xiβ₂Ϊ₂, Otøβ_∑Y., α₃β₂γ₂, and α₅β₂γ2 before and Fig. 4 after standardization to the stimulation by 1 μM diazepam (100%). Qualitatively similar data have been published before (Sanna et al. 2002; Eur. J. Pharmacol. 451, 103-110). Averaged data of the individual curves summarizing the effects by Zolpidem are shown below for unstandardized and standardized stimulation.

Table 3: Summary for Zolpidem (n = 5 each)

Receptor Potency Efficacy Standardized Eff ici

OC1P272 1 ? 1 =ε jt iiivi 429 ± i20 Vo 215 ± 74 Vo α₂β2Y2 1135 ± 312 nM 484 ± 60 % 179 ± 23 % α₃β₂γ2 2021 ± 495 nM 691 ± 365 % 166 ± 88 %

1260 ± 744 nM 33 ± 12 % 16 ± 4 %

Diazepam

[0090] Current stimulation by diazepam was determined in each batch of oocytes as follows. GABA (EC₃.₅) was applied until a stable response was obtained. Subsequently, GABA was applied in combination with 1 μM diazepam. Stimulation at the same subunit combination in different batches of oocytes was not statistically different, in each case. Stimulation by 1 μM diazepam at αiβ₂Y₂ amounted to 223 ± 28 % (n = 5) and 178 ± 20 % (n = 5) in two different batches of oocytes. Stimulation at α₂β₂γ₂ amounted to 264 ± 61 % (n = 5), 280 ± 71 % (n = 5) and 318 ± 62 % (n = 5) in three different batches of oocytes. Stimulation at 0^₂7₂ amounted to 417 ± 85 % (n = 5) and 417 ± 144 % (n = 5) in two different batches of oocytes. Stimulation at α₅β₂γ2 amounted to 237 ± 97 % (n = 5) and 160 ± 4 % (n = 5) in two different batches of oocytes.

[0091] The results obtained for Zolpidem are comparable to those achieved by Sanna et al 2002 (referenced above) in previous experiments and show an efficacy of 215% relative to diazepam at αiβ27₂ GABA_A receptors. Zolpidem therefore acts as a positive allosteric modulator with high intrinsic activity, i.e., acts a full agonist. Compounds of formulas (I) and (II) show a lower intrinsic activity, i.e., act as partial agonists.

[0092] Low intrinsic activity of the compounds of formulas (I) and (II) means that potentiation of the response mediated by GABAA receptors is limited even at high levels of receptor occupancy, which could be achieved with high concentrations of the these compounds. PET studies indicate Zolpidem (20 mg) produces receptor occupancy of about 20% in man (Abadie et al., European Journal of Pharmacology, 295 (1996), 35-44), i.e., clinical dose (10 mg) is on the steep inflection part of the dose-response curve. The compounds of formulas (I) and (II), nevertheless, still produce sufficient potentiation of the GABAA receptor to be highly effective for both sleep onset and maintenance. Excessive potentiation at higher doses is limited.

[0093] Producing lower stimulation at the individual receptor level is believed to be advantageous. Since the maximal potentiation of the GABAA response produced by such a low efficacy agonist is limited by its intrinsic efficacy, no further potentiation of the GABA_A response is achieved beyond a certain plasma concentration. In a clinical setting, such a limit on the maximum potentiation of the GABAA receptor mediated response provides an advantageous ability to avoid excess potentiation with increasing plasma concentrations. [0094] As a result of partial agonist activity at the GABA_A receptor benzodiazepine site, the compounds of formulas (I) and (II), or their respective pharmaceutically acceptable salts, can also provide a more restful and improved quality of sleep by generally preserving sleep architecture. Classic benzodiazepines, which act as full agonists, typically reduce SWS and generally adversely affect sleep architecture. This ability to produce improved quality sleep over a sustained period, whilst minimizing side effects leads to the advantageous use of the compounds of formulas (I) and (II), or their respective pharmaceutically acceptable salts, for the treatment of various types of insomnia. In particular, various types of insomnia may be treated advantageously by achieving a maximal potentiation of the response mediated by the cti subunit containing GABA_A receptors from only about 40% to about 90% using the compound of formula (II) or a pharmaceutically acceptable salt thereof or from about 20% to about 60% using the compound of formula (I) or a pharmaceutically acceptable salt thereof. [0095] The potentiation of the GABA_A mediated response over time following the administration (e.g., oral) of the compound of formula (I) and/or (II), or their respective pharmaceutically acceptable salts, may be determined using a model. In this model, measured or predicted free plasma concentration following the dosing of the compound of formula (I) and/or (II), or their respective pharmaceutically acceptable salts (assuming 50% plasma protein binding), as the clinically relevant drug concentration and the in vitro concentration-response data for GABAA receptor potentiation as discussed above can be used to predict the percent potentiation of the response mediated by GABAA otiβ₂Y₂ (oci-containing) receptors over time after the administration. Specifically, the percent potentiation of the GABAA αiβ₂Y₂ receptor mediated response for the compound of formula (I) and/or (II)), or their respective pharmaceutically acceptable salts, can be calculated as follows:

[0096] % potentiation = Efficacy (maximal % potentiation of GABA_A αiβ₂Y₂ receptor) / [1 + (EC50/concentration of the compound of formula (I) and/or (H)), or their respective pharmaceutically acceptable salts)]. [0097] The compounds of formulas (I) and (II) and/or their respective pharmaceutically acceptable salts can be used as medicaments, for example in the form of pharmaceutical preparations. The pharmaceutical preparations are typically administered orally, for example, in the form of tablets, coated tablets, dragees, hard and soft gelatine capsules, solutions, emulsions or suspensions. The administration can, however, also be effected rectally, for example, in the form of suppositories, or parenterally, for example, in the form of injection solutions. [0098] The compounds of formulas (I) and (II) and/or their respective pharmaceutically acceptable salts can be processed with pharmaceutically inert, inorganic or organic carriers for the production of pharmaceutical preparations, and the like. Lactose, corn starch or derivatives thereof, talc, stearic acid or its salts and the like can be used, for example, as carriers for tablets, coated tablets, dragees and hard gelatine capsules. Suitable carriers for soft gelatine capsules are, for example, vegetable oils, waxes, fats, semi-solid and liquid polyols and the like; although carriers are not necessary in the case of soft gelatine capsules. Suitable carriers for the production of solutions and syrups are, for example, water, polyols, sucrose, invert sugar, glucose and the like. Adjuvants, such as alcohols, polyols, glycerol, vegetable oils and the like, can be used for aqueous injection solutions of water- soluble acid addition salts of compounds of formula (I) and (II), but as a rule are not necessary. Suitable carriers for suppositories are, for example, natural or hardened oils, waxes, fats, semi-liquid or liquid polyols and the like. [0099] The pharmaceutical preparations can also contain preservatives, solubilizers, stabilizers, wetting agents, emulsifiers, sweeteners, colorants, flavorants, salts for varying the osmotic pressure, buffers, coating agents or antioxidants. They can also contain other therapeutically valuable substances. [00100] The compound of formula (II) or pharmaceutically acceptable salt thereof is preferably administered in the amount from about 0.5 mg to about 5 mg. More preferably, the administration amount is from about 1 mg to about 3 mg, even more preferably from about 1.5 mg to about 2.5 mg.

[00101] It has now been determined that the compound of formula (II) shows similar pharmacokinetic (PK) profile in both the non-elderly and elderly, and exhibits less increase in exposure in the elderly than seen with Zolpidem, and less increase in half-life than seen with eszopiclone, as shown in Fig. 32. As a result, the same or similar doses of the compound of formula (II), which are effective for non-elderly adults (18-64 years of age), could be effective for the elderly. Fig. 32 also demonstrates that the compound of formula (I) has similar pharmacokinetic profiles in both the non-elderly and the elderly.

[00102] The administration amount of the compound of formula (I) or a pharmaceutically acceptable salt thereof is preferably from about 1 to about 20 mg, preferably from about 1.5 mg to about 20 mg. The drug is preferably administered once daily in an oral dosage form shortly before the patient wants to sleep. The oral dosage may consist of one or more tablets, coated tablets, dragees, hard and soft gelatine capsules, solutions, emulsions or suspensions and the like, so long as the desired amount of the medication is administered. Also, if desired, the daily dose may be administered in parts over a span of up to about 30 minutes. [00103] As an alternative, compounds of formulas (I) and (D), or their pharmaceutically acceptable salts, can be administered in combination. For example, a single medicament may be provided containing both compound of formula (I) and compound of formula (II) (or their salts), or two separate medicaments may be provided. The two separate medicaments may be taken at substantially the same time, or administration may be carried out over a longer period.

[00104] Administration of both drags may ue carried out over a broad range of dosage levels. The particular dosage levels to be used will be varied to fit the individual requirements of the patient. Preferred daily dosage levels for each compound are as discussed above, although lower dosages are preferred since both compounds are being administered.

Preparation Example 1: Preparation of 7-Chloro-3-(5-methylaminomethyl-

[l,2,4]oxadiazol-3-yl)-5-methyl-4,5-dihydroimidazo[l,5-a][l,4]benzodiazepine-6- one

6-Chloro-3,4-dihydro-4-methyl-2H- 1 ,4-benzodiazepine-2,5(lH)-dione

[00105] A 750 mL 4-necked reaction vessel equipped with a mechanical stirrer, a thermometer, a reflux condenser and an argon supply was charged with 2-amino-6- chloro-benzoic acid (75.0 g) and 1,4-dioxane (375 mL). Ethyl chloroformate (45.8 mL) was added to that solution, yielding an off-white suspension, which was heated under reflux for 3 hours. The orange solution so obtained was cooled to 80⁰C and acetyl chloride (37.2 mL) was added, forming again an off-white suspension which was heated for 2 hours under reflux. The resulting suspension was concentrated at

40⁰C under reduced pressure and the residue was heated (with stirring) under reflux for 1 hour in a mixture of tert-butyl-methylether (300 mL) and w-heptane (300 mL).

The suspension was filtered and the crystals were washed with a mixture of tert- butyl-methylether (50 mL) and n-heptane (50 mL) and dried under vacuum at 60⁰C for 18 hours to give 6-chloroisatoic anhydride as an off-white powder (83.7 g). This was used without further purification in the next step.

[00106] A mixture of 6-chloroisatoic anhydride (25.0 g) and sarcosine (12.4 g) were suspended in 100 mL/?-xylene and stirred and heated under reflux for 2 hours.

The resulting suspension was cooled to ambient temperature and stirred for a further 1 hour before collecting the solid by filtration. The filter-cake was washed with 2 x 25 mL /(-xylene and dried at 50⁰C under vacuum. The solid was then suspended in ice-cold deionized water (75 mL) and stirred for 1 hour. The solid was collected by filtration and the filter-cake washed with deionized water (25 mL) and dried under vacuum at 80⁰C for 18 hours to give the title compound as a beige powder (25.2 g) m.p. 230-232⁰C

Ethyl-7-chloro-5.6-dihydro-5-methyl-6-oχo-4H-imidazo[ 1 ,5- a] [ 1 ,4]benzodiazepine- 3-carboxylate

Part i

[00107] 6-Chloro-3,4-dihydro-4-methyl-2H-l,4-benzodiazepine-2,5(lH)-dione (25.Og) was suspended in a mixture of toluene (200 mL) and λπv-dimethyl-;?- toluidine (32.1 mL). This suspension was stirred and heated to 100⁰C before phosphorus oxychloride (11.2 mL) was added drop-wise over 30 minutes. Stirring at 100⁰C was continued for a further 2Vz hours to give a dark-orange solution. This was cooled to 40⁰C and the toluene removed under reduced pressure to give 82 g of a dark-orange oil.

Part 2

[00108] A solution of hexamethyldisilazane (81.2 mL) in anhydrous THF (265 mL) was stirred and cooled to -35°C. H-Butyllithium (229.5 mL of a ca. 1.6M solution in hexanes) was added over 45 minutes. After stirring for 30 minutes at - 35°C, a solution of ethyl(dimethylamino-methyleneamino)acetate (35.2 g) in anhydrous THF (70.4 mL) was added over 30 minutes. The orange solution obtained was stirred for 1 hour at -35⁰C before a solution of the crude iminochloride (prepared in Part 1) in anhydrous THF (100 mL) was added drop- wise over 1 hour whilst maintaining the reaction at -15°C. The resulting dark red solution was stirred 1 hour at -15°C, then 18 hours at ambient temperature. Glacial acetic acid (75 mL) was added drop-wise over 10 minutes, then deionized water (75 mL) was added in one portion and the orange suspension was heated under reflux for 2 hours. The THF was removed under reduced pressure and the residue was partitioned between 200 mL dichloromethane (200 mL) and deionized water (100 mL). The phases were separated and the organic phase was washed with IN hydrochloric acid (2 x 100 mL) and with deionized water (100 mL). The combined aqueous phases were back-extracted with dichloromethane (2 x 100 mL). The organic extracts were combined and dried over anhydrous sodium sulphate, filtered and concentrated in vacuo. The residue was stirred in w-heptane (200 mL) at ambient temperature for 30 minutes and the solid collected by filtration. The sticky crystals so obtained were stirred and heated under reflux for 30 minutes in ethanol (213.5 mL), stirred for 3 hours to ambient temperature and a further 2 hours at - 20⁰C. The solid was collected by filtration, washed with ethanol (3 x 20 mL) and dried at 60°C under reduced pressure for 16 hours to give the title compound as a beige powder (23.4 g) m.p. 225.5-226.5 ⁰C

7-Chloro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo [1,5-a] [l,4]benzodiazepine-3- carboxamide

[00109] A suspension of ethyl 7-chloro-5,6-dihydro-5-methyl-6-oxo-4H- imidazo[l,5-a][l,4]-benzodiazepine-3-carboxylate (22.8 g) in 1,4-dioxane (91.2 mL) was stirred at ambient temperature. Formamide (14.1 mL) and sodium methoxide (13.9 mL of a ca. 5.4M solution in methanol) were successively added to yield a light-orange solution, which became a white suspension after 10 minutes. This suspension was stirred for 2 hours at 30⁰C. Deionized water (200 mL) was added in one portion and the 1,4-dioxane was removed at 40⁰C under reduced pressure. The remaining white suspension was stirred for 2 hours at 0⁰C and the solid collected by filtration. The filter-cake was washed with deionized water (3 x 50 mL) and dried at 80⁰C under reduced pressure for 18 hours to give the title compound as a white powder (19.43 g) m.p.>250°C

7-Chloro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[l,5-a] [l,4]benzodiazepine-3 - carbonitrile

[00110] A stirred suspension of 7-chloro-5,6-dihydro-5-methyl-6-oxo-4H- imidazo[l,5-a][l,4]benzodiazepine-3-carboxamide (19.0 g) in 1,4-dioxane (95 mL) was treated with phosphorous oxychloride (6.58 mL) added as a single portion. The reaction mixture was heated under reflux for 1 hour giving a yellow solution, which was concentrated at 50⁰C under reduced pressure. The residue was stirred at ambient temperature for 2 hours in deionized water (100 mL). The solid was collected by filtration, the filter-cake washed with deionized water (3 x 30 mL) and dried at 80°C under vacuum for 18 hours to give the title compound as a light yellow powder (17.3 g) m.p. 238.5-239.5°C

7-Chloro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[l,5-a][l,4] benzodiazepine-3- carboxamidoxime

[00111] A stirred suspension of 7-chloro-5,6-dihydro-5-rnethyl-6-oxo-4H- imidazo[l,5-a][l,4]benzodiazepine-3-carbonitrile (16.8 g) in DMF (101 mL) was treated with hydroxylamine hydrochloride (13.48 g) added as a single portion. Sodium methoxide (34.2 mL of a ca. 5.4M solution in methanol) was then added drop-wise over 60 minutes to the yellow suspension, which turned to a colorless suspension. The reaction was stirred for ϊ hour at ambient temperature, then cooled to 0-2⁰C before adding deionized water (202 mL) over 30 minutes. After stirring for 1 hour at 0°C, the solid was collected by filtration, the filter-cake washed with deionized water (2 x 40 mL) and dried at 70⁰C under vacuum for 18 hours to afford the title compound &s a white powder (17.84 g) m.p>250°C

7-Chloro-3-(5-chloromethyl-[l,2,4]oxadiazol-3-yl)-5-methyl-4,5- dihydroimidazofl ,5-a][ 1 ,4]benzodiazepine-6-one

[00112] A suspension of 7-chloro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[l,5- a][l,4]benzodiazepine-3-carboxamidoxime (872 mg) and magnesium oxide (109 mg) was stirred under a nitrogen atmosphere in 1,4-dioxane (35 mL). Chloroacetyl chloride (295 μl) was added in one portion and the resulting white suspension was stirred at ambient temperature for 1 hour and then heated under reflux for 16 hours to give a light orange suspension. The reaction was allowed to cool to ambient temperature and the solvent was evaporated at reduced pressure. The resulting pale pink residue was purified by silica gel chromatography. Elution with ethyl acetate and concentration of appropriate fractions furnished the title compound as a white amorphous solid (898 mg) m.p. 234-238⁰C. m/z 364, IvH-H⁺ 7-Chloro-3-(5-methylaminomeΛyl-[l,2,4]oxadiazol-3-yl)-5-methyl-4,5- dihydroimidazo[l,5-a][l,4]benzodiazepine-6-one [00113] A pressure tube was charged with 7-chloro-3-(5-chloromethyl- [ 1 ,2,4]oxadiazol-3-yl)-5-methyl-4,5-dihydroimidazo[ 1 ,5-a] [ 1 ,4]benzodiazepine-6- one (795 mg), 1,4-dioxane (7 mL), methylamine hydrochloride (589 mg) and stirred under a nitrogen atmosphere. To this suspension was added NJV- diisopropylethylamine (1.59 mL). The reaction vessel was sealed and the contents stirred at ambient temperature for 5¹A hours. The solvent was evaporated at reduced pressure and the resulting residue partitioned between dichloromethane (50 mL) and deionized water (40 mL). The organic layer was washed with deionized water (20 mL), brine (20 mL), dried over anhydrous magnesium sulfate, filtered and evaporated at reduced pressure to give crude product (803 mg) as an off-white solid. Purification by silica gel chromatography (eluting with 9:1 ethyl acetate / methanol) gave the title compound (713 mg) as a semi-crystalline white solid, m/z 359, M+H⁺. ¹H NMR (400 MHz, CDCl₃) δ_H 2.60 (3H, s), 3.21 (3H, s), 4.15 (2H, s), 4.51 (IH, d, 7=16), 5.19 (IH, d, 7=16), 7.35 (IH, d, 7=8), 7.52 (IH, dd, 7=8 and 8), 7.60 (IH, d, 7=8), 8.07 (IH, s).

[00114] The present invention is further described by the following Examples. These Examples are indended to illustrate some of the embodiments of the present invention and are not to be construed as limitations thereon.

Example 1

[00115] A placebo controlled, randomized, double-blind, cross-over study of the effects of the compound of formula (II) was conducted using a road noise model using 12 healthy volunteers. Specifically, the volunteers were subjected to road traffic noise to imitate the effects of insomnia, and the medication was orally administered 5 minutes before the 11 pm bed time in 1.0 mg, 1.5 mg, 2 mg and 2.5 mg doses in the form of a hard gelatine capsule containing the powdered compound of formula (II) in free base form. Measurements were then taken at 8, 10 and 12 hours after dosing.

[00116] The results of the study are summarized in Tables 4-6.

Table 4: Objective Efficacy

Table 5: Subjective Efficacy

* The road traffic noise model is considered clinically nondiscriminant for sleep onset measures

Table 6: Objective Residual Effects

* immediate word recall was not tested at 10 and 12 hours [00117] When the data was corrected for multiple companions, mere was no impairment of performance on any of the cognitive or psychomotor tests 8 to 12 hours after the dose was administered. Any residual effects that were observed the morning after dosing were inconsistent. Residual effects did not appear to be dose or time related.

Table 7: Subjective Residual Effects at 2.5 mg

Example 2

[00118] A single and repeat dose pharmacokinetic safety and pharmacodynamic study of the effects of the compound of formula (II) was conducted using healthy volunteers. The compound of formula (II) was administered orally in 1 mg, 1.5 mg, 2 mg and 2.5 mg doses via a hard gelatine capsule containing the compound in powder form.

[00119] The pharmacokinetic analysis of the results showed that the half-life of the compound of formula (II) is about 3.5 hours. There were no significant differences in the pharmacokinetic profile on day 14 after repeat dosing compared to day 1. Food was found to have little or no effect on the extent of the absorption of the compound of formula (II). The half life of the compound of formula (I) was not appreciably different from that of the compound of formula (II), with mean values in the range of 3 to 5 hours. [00120] The analysis of the pharmacokinetic data also shows that onset, maintenance and/or terminal insomnia may be treated by administering the compound of formula (II) or a pharmaceutically acceptable salt thereof to achieve an AUC from about 17.5 ng'h/mL to about 600 ng'h/mL, from about 25 ng'h/mL to about 500 ng'h/mL or from about 25 ng'h/mL to about 400 ng'h/mL. For example, the AUC may be from about 52.5 ng'h/mL to about 360 ng'h/mL, from about 75 ng*h/mL to about 300 ng^#h/mL, from about 75 ng'h/mL to about 240 ng'h/mL, from about 75 ng'h/mL to about 200 ng'h/mL, from about 75 ng'h/mL to about 150 ng'h/mL, from about 105 ng*h/mL to about 120 ng^#h/mL, or any range among all of the above-listed AUC values. Preferably, the AUC is from about 75 ng'h/mL to about 240 ng'h/mL.

[00121] The treatment is also conducted to achieve a C_ma_x from about 2.5 ng/mL to about 125 ng/mL, from about 7.5 ng/mL to about 75 ng/mL, from about 7.5 ng/mL to about 62.5 ng/mL, from about 7.5 ng/mL to about 37.5 ng/mL, from about 10 ng/mL to about 50 ng/mL, from about 12.5 ng/mL to about 45 ng/mL, from about 15 ng/mL to about 40 ng/mL, or any range among all of the above-listed C_max values. Preferably, the C_max is from about 15 ng/mL to about 45 ng/mL.

Example 3

[00122] A randomized, multicenter, double-blind, placebo-controlled crossover study was conducted to assess the efficacy of the 1.5 mg and 2.5 mg doses of the compound of formula (II) in the treatment of primary insomnia in adult patients. Specifically, one of the objectives of the study was to asses the efficacy of 1.5 mg and 2.5 mg doses on PSG and patient-reported measures of sleep. Also, the study was aimed at assessing the safety of 1.5 mg and 2.5 mg doses. [00123] The study in this Example was performed for two consecutive nights with a 5-12 day washout between each period. The dosing was conducted 30 minutes before lights were turned out for the night via oral administration of a hard gelatine capsule containing the compound of formula (II) (free base) in powder form. PSG was taken for 8 hours from "lights out" on nights 1 and 2 of each treatment period. Centralized scoring of PSG was used. Testing for residual effects using the Digit Symbol Substitution Test (DSST) was performed at least 30 minutes after wake time (9 hours post dose). The overall study design is shown in Fig. 8.

[00124] The study was conducted using 67 subjects younger than 65 years of age

(21 males, 46 females; mean age 45.1 yrs, range 23-64 yrs) with a documented diagnosis of primary insomnia (DSM-IV criteria). These subjects' typical bed time was between 9 pm and 1 am with at least 7 hours in bed. These subjects reported sleep latency of at least 45 minutes and TST of not more than 6.5 hours in a sleep diary for at least 3 of 7 nights.

[00125] On screening using PSG for 2 nights, the patients showed latency to persistent sleep (LPS) of more than 20 minutes, with no nights showing LPS of less than 15 minutes. Mean WASO of the patients was at least 40 minutes and mean

TST was 240-420 minutes.

[00126] The top-line efficacy results of the study in Example 3 are shown in Table

Table 8: Top-Line Efficacy Results

[00127] The compound of formula (II) showed robust effects on both sleep onset and sleep maintenance. Specifically, compared to a placebo, the 1.5 mg dose reduced LPS by 17.0 minutes (p<0.0001) and the 2.5 mg dose reduced LPS by 20.7 minutes (p<0.0001), as shown in Fig. 9. The 1.5 mg dose increased TST by 33.1 minutes (pO.0001) and the 2.5 mg dose increased TST by 45.0 minutes (pO.0001), as shown in Fig. 10, compared to a placebo. The 1.5 mg dose reduced WASO by 16.7 minutes (pO.0001) and the 2.5 mg dose reduced WASO by 25.7 minutes (pO.0001), as shown in Fig. 11, compared to a placebo. [00128] Importantly, as shown in Figs. 12 and 13 and Table 8, these doses reduced WASO and TWT in the second half of the night (5-8 hours after "lights out") compared to a placebo. Compared to placebo, TWT in hours 5-8 was reduced by 10.8 minutes with the 1.5 mg dose (p=0.0008) and by 16.2 minutes with the 2.5 mg dose (p<0.0001). This demonstrates that the compound of formula (II) can be used to treat terminal insomnia and reduce early morning awakenings. In fact, a reduction in a total amount of time the subject was awake during each hour after dosing was observed, as shown in Fig. 14, with the 2.5 mg dose producing a statistically significant reduction each hour, except hour 7, where p was 0.0577 for the overall treatment effect (reduction in time awake during hour 7 almost reached statistical significance).

[00129] These results are particularly unexpected for an agent such as the compound of formula (II). Since it is only a partial agonist at the GABA_A receptor benzodiazepine site and its half-life is similar to some insomnia agents acting as full agonists at this site, which were found ineffective for the treatment of maintenance and terminal insomnia even when used in substantially larger amounts, the compound of formula (II) would be expected to be even less effective than these other agents. It has now been unexpectedly found that this is not the case.

[00130] In addition to the improvements in the quantity of sleep, the subjects of the study also reported a marked improvement in sleep quality for both 1.5 and 2.5 mg doses, which is demonstrated in Figs. 15 and 16. In particular, the compound of formula (II) was found to produce sleep architecture, which is equivalent to the natural sleep architecture (i.e., when no medicaments are administered). There was no impairment of slow wave sleep, and only a small effect on REM sleep was observed. These results are demonstrated by the chart in Fig. 17. [00131] Maintaining normal sleep architecture is a very important component of getting a good night rest. Some conventional insomnia medications, such as classic benzodiazepines, may have the ability to induce and maintain sleep, but they do so by considerably altering the normal sleep architecture, which results in unrefreshing sleep and other side effects.

[00132] The results of the study conducted in accordance with Example 3 showed that the compound of formula (II) produces no patient-reported residual sedation effects at either the 1.5 mg dose or the 2.5 mg dose compared with the placebo. This is demonstrated by the chart in Fig. 18. [00133] The objective residual effects of the administration of the compound of formula (II) were also evaluated. The scores on the DSST taken by the subjects 9 hours after administering the dose were only slightly lower than those obtained from the subjects who were administered the placebo.

[00134] The results also showed that the compound of formula (II) was safe and well-tolerated at 1.5 mg and 2.5 mg doses. No serious side effects, and only a low incidence of adverse events, were reported. These results are summarized in Table

9.

Table 9: Safety Results

* "n" refers to the total number of patients enrolled in the study

* - reported at any time in the study irrespective of whether these events were considered related to the medication

Example 4

[00135] A randomized, double-blind, placebo-controlled parallel group design was used to assess the hypnotic efficacy of 1.5 mg and 2.5 mg doses of the compound of formula (II) following 7 nights dosing using 149 subjects. The study was conducted in 20 sleep laboratories in the United States using both objective and subjective measures. PSG data was collected on nights 1, 6 and 7 and results are based on the mean data from these three nights. The compound of formula (TI) was administered in free base form as a powder in a capsule. The details of the study design are shown in Fig. 19.

[00136] The subjects were males and females at least 65 years old with a documented diagnosis of primary insomnia (DSM-IV criteria). These subjects' typical bed time was between 9 pm and 1 am with at least 7 hours in bed. These subjects reported five nights or more in seven days with TST of not more than 6.5 hours with at least 7 hours in bed. The subjects had a history of sleepiness, tiredness, or unintentional napping during the daytime, which the subjects attribute to poor sleep at night. On screening using PSG for 2 nights, mean TST was 240- 420 minutes. Mean latency in Multiple Sleep Latency Test (MSLT) was at least 5.5 minutes and not more than 14 minutes.

[00137] PSG was used to obtain TST (average of nights 1, 6 and 7). The daytime function (day 8) was measured using Psychomotor Vigilance Task (PVT), MSLT (MSLT Clinical Guidelines; Sleep, 1(3): 260-276 (1992)), Karolinska Sleepiness Scale (KSS); and objective measures Rey Auditory Verbal Learning Test (RAVLT) (day 8) (assessed 30 ± 10 minutes after ϋghts-on). Sleep architecture, subject reported sleep variables and categorical rating of sleep quality and safety endpoints including the Benzodiazepine Withdrawal Questionnaire were also determined. [00138] This study showed a highly significant improvement between both doses of the compound of formula (II) and placebo in the primary endpoint of PSG- derived TST. Compared to placebo, mean TST increased by 30.9 minutes (9%) at 1.5 mg and 56.4 minutes (17%) at 2.5 mg (p= 0.0001 and p= < 0.0001 respectively).

[00139] Significant improvements were also seen across key PSG-derived secondary endpoints, including WASO and LPS. The 2.5 mg dose also showed a significant effect on WASO during the second half of the night, indicating that compound of formula (II) is highly effective in maintaining sleep throughout the night. This was further confirmed by the hour-by-hour analysis of TWT. Treatment with compound of formula (II) produced a statistically significant reduction in TWT for all hours of the night apart from hour 7.

[00140] Table 10 below shows the results for the primary and key secondary PSG endpoints (average of nights 1, 6 and 7). Table 10: Primary And Key Secondary PSG Endpoints

"n" - number of subjects that were randomized into the study

[00141] Table 11 shows non-PSG efficacy measures. These results were supported by subject-reported measures including sTST, sSOL (subjective sleep onset latency) and sWASO.

Table 11: Non-PSG Efficacy Measures

[00142] Overall, the results showed no significant differences between placebo and either dose of the compound of formula (II) in the PVT or RAVLT. Also, overall, no significant difference was seen subjectively in the KSS. No significant difference was seen in the Benzodiazepine Withdrawal Questionnaire. [00143] The specific results are shown in Figs. 20-31 and discussed below. [00144] Fig. 20 shows that both 1.5 mg and 2.5 mg doses increased TST in the elderly compared to the placebo. Fig. 21 shows that the 1.5 mg dose decreased LPS by 34% and the 2.5 mg dose decreased LPS by 43% compared to the placebo. Fig. 22 shows that the 1.5 mg dose decreased WASO by 15% and the 2.5 mg dose decrease WASO by 36% compared to the placebo. Fig. 23 shows that there was a significant decrease in WASO in the second half of the night (5-8 hours after "lights out") when the dose was 2.5 mg. Fig. 24 shows that the 2.5 mg dose significantly reduced TWT every hour, except hour 7, where the overall treatment effect was not statistically significant. The 1.5 mg dose significantly reduced total wake time each hour up to hour 6.

[00145] Daytime function (daytime sleepiness) was measured using the MSLT, as shown in Fig. 25. The average sleep latency over all timepoints tested (2, 4, 6, 8 & 10 hours post wake time) was increased, demonstrating that the compound of formula (II) improves daytime function by reducing daytime sleepiness. [00146] As demonstrated by the chart in Fig. 26, subjective sleep quality showed sustained improvement over all 7 nights of dosing. Subject-reported sleep quality during night 1 is shown in Fig. 27, where both doses markedly improved categorical ratings of sleep quality (pO.OOOl) on night 1. [00147] The subjects spent nights 1, 6 and 7 in the sleep laboratory and were at home on nights 2-5. They were asked to rate their sleep quality as very poor, poor, good or very good. Fig. 28 shows that both the 1.5 mg dose and the 2.5 mg dose produced a significant reduction in subject-reported sleep onset latency. Fig. 29 shows that both of these doses also produced a significant increase in sTST, and Fig. 30 shows that these doses produced a significant decrease in sWASO. [00148] The subjects were also asked to report their residual sedation. As can be seen in Fig. 31 , neither the administration of the 1.5 mg dose or the 2.5 mg dose produced residual sedation effects, since the results are comparable to those of a placebo.

[00149] The results also showed that the compound of formula (II) was safe and well-tolerated at 1.5 mg and 2.5 mg doses. No serious treatment emergent adverse events were reported during the study. The majority of adverse events reported were mild and infrequent. The most common adverse events were dizziness, headache and somnolence and the percentage of patients reporting these events is shown in the table below. These results are summarized in Table 12. Table 12: Safety Results

"n" - number of subjects that were randomized into the study

* - reported at any time in the study irrespective of whether these events were considered related to the medication

[00150] Overall, the study in this Example showed that the compound of formula (II) has robust effects on both sleep onset and sleep maintenance. The PSG analysis showed that the compound of formula (II) generally preserved sleep architecture. These PSG results were supported by subject-reported measures, including sTST, sSOL and sWASO. Subjectively, sleep quality was improved on all nights and there was no residual sedation assessed 30-minutes post wake time (approximately 9 hours post dose).

[00151] An additional element of the study design was to assess daytime function on Day 8. This included the MSLT, which is an objective assessment of daytime sleepiness. Initial analyses showed that both doses of the compound of formula (II) produced a statistically significant overall improvement in the MSLT across the day compared to placebo indicating that the subjects were more alert following treatment with the compound of formula (II). This is particularly surprising since many conventional insomnia agents not only fail to improve daytime activity in the elderly, but some, particularly those with longer half-lives, exacerbate the already existing daytime sleepiness.

[00152] Daytime function was further assessed objectively using the RAVLT and PVT and subjectively using the KSS. Initial analyses suggest overall that there was no significant difference between the compound of formula (II) and placebo. [00153] No significant difference was seen between either dose of the compound of formula (II) and placebo in the Benzodiazepine Withdrawal Questionnaire. [00154] The results in Example 4 demonstrate the effects of the compound of formula (II) on sleep onset and sleep maintenance in the elderly population and indicate that the 1.5 mg and 2.5 mg doses have hypnotic efficacy in the elderly with no significant residual effects.

[00155] While the invention has been described in conjunction with the detailed description thereof and the accompanying figures, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. Use of a compound of formula (I) or a pharmaceutically acceptable salt thereof in the preparation of a medicament for treating maintenance insomnia and/or treating terminal insomnia in a human in need thereof

(I)

2. Use of a compound of formula (I) or a pharmaceutically acceptable salt thereof in the preparation of a medicament for treating insomnia in a human in need thereof

(I)

wherein the human is at least 65 years old.

3. The use according to claim 1 or 2, wherein the medicament is such as to decrease wake after sleep onset and/or increase total sleep time after sleep onset.

4. Use of a compound of formula (I) or a pharmaceutically acceptable salt thereof in the preparation of a medicament for (i) increasing total sleep time in a period from about four to about eight hours after administration of the medicament and/or (ii) decreasing wake after sleep onset in a human in need thereof

(I)

5. The use according to any of claims 1-4, wherein the amount of the compound of formula (I) is from about 1 mg to about 20 mg.

6. The use according to any of claims 1-5, wherein the medicament is such as to reduce latency to sleep onset and/or latency to persistent sleep.

7. The use according to any of claims 1-6 for increasing total sleep time in the period from about five to about eight hours after administration of the medicament.

8. The use according to any of claims 1-7 for increasing total sleep time in the period from about six to about eight hours after administration of the medicament.

9. The use according to any of claims 1-8 for decreasing wake after sleep onset in a period from about four to about eight hours after administration of the medicament.

10. The use according to any of claims 1-9 for decreasing wake after sleep onset in a period from about five to about eight hours after administration of the medicament.

11. The use according to any of claims 1 - 10 for decreasing wake after sleep onset in a period from about six to about eight hours after administration of the medicament.

12. The use according to any of claims 1-11, wherein the medicament is such as to achieve a maximal potentiation of a response mediated by GABA_A receptors containing an αi-subunit of from about 20% to about 60%.

13. The use according to any of ciaims 1-12, wherein the medicament is also for treating sleep onset insomnia.

14. The use according to any of claims 1-13, wherein the compound of formula (I) or the pharmaceutically acceptable salt thereof is in a pharmaceutical composition.

15. The use according to any of claims 1 and 3-14, wherein the human is at least 65 years old.

16. A pharmaceutical composition suitable for treating maintenance and/or terminal insomnia in a unit dosage form comprising from about 1.5 mg to about 20 mg of a compound of formula (I) or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier or diluent

(D

17. A pharmaceutical composition for treating maintenance and/or terminal insomnia comprising a compound of formula (I) or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier or diluent

(I)

18. A pharmaceutical composition for treating insomnia in a human who is at least 65 years old comprising a compound of formula (I) or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier or diluent

(I)

19. The pharmaceutical composition according to any of claims 16-18, which is also tor decreasing waKc aucf siccp ousel.

20. The pharmaceutical composition according to any of claims 16-19, which is also for increasing total sleep time after sleep onset.

21. The pharmaceutical composition according to any of claims 17-20, wherein the amount of the compound of formula (I) is from about 1 mg to about 20 mg.

22. Compound of formula (I) or a pharmaceutically acceptable salt thereof for use in treating maintenance insomnia and/or treating terminal insomnia in a human

(I)

23. Compound of formula (I) or a pharmaceutically acceptable salt thereof for use in treating insomnia in a human

(!)

wherein the human is at least 65 yeαis old.

24. The compound according to claim 22 or 23, which is also for decreasing wake after sleep onset.

25. The compound according to any of claims 22-24, which is also for increasing total sleep time after sleep onset.

26. The compound according to any of claims 22, 24 and 25, wherein the human is at least 65 years old.

27. Use of a compound of formula (I) or a pharmaceutically acceptable salt thereof and a compound of formula (II) or a pharmaceutically acceptable salt thereof in the preparation of medicaments for treating insomnia in a human in need thereof

28. The use according to claim 27, wherein a single medicament comprising the compounds (I) or its said pharmaceutically acceptable salt and (II) or its said pharmaceutically acceptable salt is prepared.

29. The use according to claim 27, wherein separate medicaments are prepared comprising compound (I) or its said pharmaceutically acceptable salt and (II) or its said pharmaceutically acceptable salt respectively.

30. The use according to any of claims 27-29, wherein the human is at least 65 years old.

31. A product comprising a compound of formula (I) or a pharmaceutically acceptable salt thereof and a compound of formula (II) or a pharmaceutically acceptable salt thereof

32. A pharmaceutical composition comprising a compound of formula (I) or a pharmaceutically acceptable salt thereof and a compound of formula (II) or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier or diluent

33. A method for treating maintenance insomnia in a human in need thereof comprising administering to the human an amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof effective to treat the maintenance insomnia

(I)

34. The method according to claim 33, wherein the amount of the compound of formula (I) is from about 1 mg to about 20 mg.

35. The method according to claim 33, which is also for treatment of sleep onset insomnia, comprising administering to a human in need of such treatment an amount of the compound of formula (I) or the pharmaceutically acceptable salt thereof also effective to treat the sleep onset insomnia.

36. The method according to claim 33, wherein the administration of the compound of formula (I) or the pharmaceutically acceptable salt thereof is such as to reduce latency to sleep onset and/or latency to persistent sleep.

37. The method according to claim 33, wherein the administration of the compound of formula (I) or the pharmaceutically acceptable salt thereof is such as to achieve a maximal potentiation of a response mediated by GABA_A receptors containing an cti-subunit of from about 20% to about 60%.

38. The iiictliυu according io ciaim 33, wherein the human is at least 65 years old.

39. A method for decreasing wake after sleep onset in a human in need thereof comprising administering to the human an amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof effective to decrease the wake time after sleep onset

(I)

40. The method according to claim 39, wherein the amount of the compound of formula (I) is from about 1 mg to about 20 mg.

41. The method according to claim 39, which is also for treatment of sleep onset insomnia, comprising administering to a human in need of such treatment an amount of the compound of formula (I) or the pharmaceutically acceptable salt thereof also effective to treat the sleep onset insomnia.

42. The method according to claim 39, wherein the administration of the compound of formula (I) or the pharmaceutically acceptable salt thereof is such as to reduce latency to sleep onset and'or latency to persistent sleep.

43. The method according to claim 39, wherein the administration of the compound of formula (I) or the pharmaceutically acceptable salt thereof is such as to achieve a maximal potentiation of a response mediated by GABA_A receptors containing an ui-subuniι of from about 2U% to about 60%.

44. The method according to claim 39, wherein the human is at least 65 years old.

45. The method according to claim 39, wherein the administration of the compound of formula (I) or the pharmaceutically acceptable salt thereof is such as to decrease the wake after sleep onset in a period from about four to about eight hours after administration.

46. The method according to claim 45, wherein the period is from about five to about eight hours after administration.

47. The method according to claim 45, wherein the period is from about six to about eight hours after administration.

48. A method for treating terminal insomnia in a human in need thereof comprising administering to the human an amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof effective to treat the terminal insomnia

(D

49. The method according to claim 48, wherein the amount of the compound of formula (I) is from about 1 mg to about 20 mg.

50. The method according to claim 48, which is also for treatment υf sleep onset and/or maintenance insomnia, comprising administering to a human in need of such treatment an amount of the compound of formula (I) or the pharmaceutically acceptable salt thereof also effective to treat the sleep onset insomnia and/or the maintenance insomnia.

51. The method according to claim 48, wherein the administration of the compound of formula (I) or the pharmaceutically acceptable salt thereof is such as to reduce latency to sleep onset, latency to persistent sleep and/or wake after sleep onset.

52. The method according to claim 48, wherein the administration of the compound of formula (I) or the pharmaceutically acceptable salt thereof is such as to achieve a maximal potentiation of a response mediated by GABA_A receptors containing an αi-subunit of from about 20% to about 60%.

53. The method according to claim 48, wherein the human is at least 65 years old.

54. A method for increasing total sleep time in a period in a human in need thereof comprising administering to the human an amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof effective to increase total sleep time in the period, which is about four to about eight hours after administration

(I)

55. The method accordine to claim 54. wherein the amount of the compound of formula (I) is from about 1 mg to about 20 mg.

56. The method according to claim 54, which is also for treatment of sleep onset insomnia, comprising administering to a human in need of such treatment an amount of the compound of formula (I) or the pharmaceutically acceptable salt thereof also effective to treat the sleep onset insomnia.

57. The method according to claim 54, wherein the administration of the compound of formula (I) or the pharmaceutically acceptable salt thereof is such as to reduce latency to sleep onset, latency to persistent sleep and/or wake after sleep onset.

58. The method according to claim 54, wherein the administration of the compound of formula (I) or the pharmaceutically acceptable salt thereof is such as to achieve a maximal potentiation of a response mediated by GABA_A receptors containing an αi-subunit of from about 20% to about 60%.

59. The method according to claim 54, wherein the human is at least 65 years old.

60. The method according to claim 54, wherein the period is from about five to about eight hours after administration.

61. The method according to claim 54, wherein the period is from about six to about eight hours after administration.

62. A method for treating insomnia in a human in need thereof comprising administering to the human an effective amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof

(!) wherein the human is at least 65 years old.

63. The method according to claim 62, wherein the amount of the compound of formula (I) is from about 1 mg to about 20 mg.

64. The method according to claim 62, wherein the compound of formula (I) or the pharmaceutically acceptable salt thereof is administered in a pharmaceutical composition.

65. A method for treating insomnia in a human in need thereof comprising administering to the human a compound of formula (I) or a pharmaceutically acceptable salt thereof and a compound of formula (II) or a pharmaceutically acceptable salt thereof, wherein a total amount of the compounds of formulas (I) and (II) or their said pharmaceutically acceptable salts administered to the human is effective to treat the insomnia

66. The method according to claim 65, wherein a single medicament comprising the compounds (I) or its said pharmaceutically acceptable salt and (II) or its said pharmaceutically acceptable salt is administered to the human.

67. The method according to claim 65, wherein the compounds (I) or its said pharmaceutically acceptable salt and (II) or its said pharmaceutically acceptable salt are administered to the human separately.

68. The method according to claim 65, wherein the human is at least 65 years old.