Polymorphs of N-methyl-N-(3-{3-[2-thienylcarbonyl]-pyrazol-[1,5-α]-pyrimidin-7-yl}phenyl)acetamide and compositions and methods related thereto

#This invention is directed to polymorphs of N-methyl-N-(3-{3-[2-thienylcarbonyl]-pyrazol-[1,5-α]-pyrimidin-7-yl}phenyl)acetamide having activity over a wide range of indications, and particularly useful for the treatment of insomnia, and to related processes, compositions and methods.

#The term “insomnia” is used to describe all conditions related to the perception of inadequate or non-restful sleep by the patient (Dement, International Pharmacopsychiatry 17:3-38, 1982). Insomnia is the most frequent complaint, being reported by 32% of the adult population surveyed in the Los Angeles area (Bixler et al, Amer. Journal of Psychiatry 136:1257-1262, 1979), and 13% of the population surveyed in San Marino, Italy (Lugaresi et al., Psychiatric Annals 17:446-453, 1987). Fully 45% of the surveyed adult population of Alachua County, Fla., reported trouble getting to sleep or staying asleep (Karacan et al., Social Science and Medicine 10:239-244, 1976). The prevalence of insomnia has also been shown to be related to the age and sex of the individuals, being higher in older individuals and in females.

#Insomnia, if left untreated, may result in disturbances in metabolism and overall body function. Reduced productivity and significant changes in mood, behavior and psychomotor function. Chronic insomnia is associated with a higher incidence of morbidity and mortality. Traditionally, the management of insomnia includes treatment and/or mitigation of the etiological factors, improving sleep hygiene and the administration of hypnotic agents. The early hypnotic agents, such as barbiturates, while effective, elicited a spectrum of unwanted side effects and longer-term complications. For example, barbiturates have the potential to result in lethargy, confusion, depression and a variety of other residual effects many hours post dosing, as well as having a potential for being highly addictive.

#FIG. 1 is a Differential Scanning Calorimetry (DSC) thermogram of (Compound 1) as prepared by conventional techniques.

#FIG. 2 is a DSC thermogram of the “high” melting point polymorph of Compound 1, referred to herein as Form I.

#FIG. 3 is a DSC thermogram of the “low” melting point polymorph of Compound 1, referred to herein as Form II.

#Solids exist in either amorphous or crystalline forms. In the case of crystalline forms, molecules are positioned in 3-dimensional lattice sites. When a compound recrystallizes from a solution or slurry, it may crystallize with different spatial lattice arrangements, a property referred to as “polymorphism,” with the different crystal forms individually being referred to as a “polymorph”. Different polymorphic forms of a given substance may differ from each other with respect to one or more physical properties, such as solubility and dissociation, true density, crystal shape, compaction behavior, flow properties, and/or solid state stability. In the case of a chemical substance that exists in two (or more) polymorphic forms, the unstable forms generally convert to the more thermodynamically stable forms at a given temperature after a sufficient period of time. When this transformation is not rapid, the thermodynamically unstable form is referred to as the “metastable” form. In general, the stable form exhibits the highest melting point, the lowest solubility, and the maximum chemical stability. However, the metastable form may exhibit sufficient chemical and physical stability under normal storage conditions to permit its use in a commercial form. In this case, the metastable form, although less stable, may exhibit properties desirable over those of the stable form, such as enhanced solubility or better oral bioavailability.

#In the practice of this invention, two different polymorphs of the Compound 1 have been discovered and methods of their preparation have been developed. It has surprisingly been found that substantially pure polymorphic forms of Compound 1 are particularly advantageous with regard to use of the same as a pharmaceutical agent.

#The present inventors have discovered the polymorph Form I, which has a “high” melting point of about 196° C., and the polymorph Form II, which has a “low” melting point of about 176° C., as measured by a TA 2920 Modulated Differential Scanning Calorimeter (TA Instruments, New Castle, Del.), at a scan rate of 10° C. per minute.