Technical Field

[0001] The invention relates to treatment of subjects who have Angelman Syndrome (AS) with compounds that ameliorate the cognitive deficits associated with this condition. More particularly, it concerns the use of 2-amino substituted nicotinamides for this purpose.

Background Art

[0002] Angelman syndrome (AS) is a maternally inherited disease in which a proteosomal processing enzyme, Ube3A, that is important for synaptic plasticity during learning and memory in development and in adults, is deleted or mutated, resulting in developmental arrest of CNS functions. The clinical manifestations include severe mental retardation, periods of epileptic seizures, ataxia, hyperactivity, and disordered sleep, which last for life-time. Currently there is no effective treatment to treat the underlying synaptic dysfunction.

[0003] A family of U.S. granted patents, represented by, for example, U.S. 8,362,262, discloses low molecular weight compounds that are capable of stimulating neuronal growth, and are able to permeate the blood-brain barrier (BBB). Subsequently, it was found that certain 2 amino-substituted nicotinamides were useful in treating depression, in particular, major depressive disorder in humans as described in PCT publication WO2015/195567, and corresponding U.S. Patent 9,572,807. Oral administration of these compounds in such treatments is disclosed. However, nothing in these documents suggests that deficits in cognitive function associated with AS can be ameliorated by these compounds despite their known ability to stimulate neuronal growth, and their ability to improve self -perceived cognition in depressed patients.

[0004] In work by applicant, hippocampal slices from normal, healthy, young adult mice were treated with various concentrations of NSI-189 (100 nM to 10 μΜ) for various times up to 3.5 h, before applying theta burst stimulation (TBS) to elicit long-term potentiation (LTP) in field CA1. These treatments resulted in statistically significant enhancement of the normal LTP level. This effect could be inhibited by inhibitors of protein- synthesis or transcription, demonstrating that 189 can directly act on hippocampal excitatory circuitry to enhance its synaptic response to stimuli (Liu et al, Society for Neuroscience Abstract 2016). [0005] Further, in a mouse model of Angelman syndrome, carrying the same maternal Ube3A deletion affected in human AS patients, the normal LTP is absent. Surprisingly, a transient treatment of the hippocampal brain slices prepared from young adult Angelman mice with NSI-189 for 3.5 hours could restore the LTP activity to normal level (Liu et el, Society for Neuroscience Abstract 2016).

Disclosure of the Invention

[0006] It has now been found that certain 2-amino-substituted nicotinamides are especially useful in prevention and/or repair of various aspects of cognitive impairments that associated with AS.

[0007] Accordingly, in one aspect, the invention is directed to a method to ameliorate the cognitive deficiencies associated with AS by administering to a subject in need of such amelioration, a pharmaceutical composition wherein the active ingredient is a 2 amino- substituted nicotinamide or a pharmaceutically acceptable salt thereof. In particular, the 2- amino-substituted nicotinamide is of the formula:

wherein R is an alkyl of 3-8C and ring A is a 5- or 6-membered saturated ring optionally including an additional nitrogen which is unsubstituted or substituted with an additional nitrogen-containing substituent or a ring-opened form thereof.

[0008] Particular exemplified compounds include those of formula (2)

or formula (3)

wherein R ¹ is a branched alk l group of 3-5C or of formula (4)

wherein R is an alkyl group comprising a 5- or 6-membered ring.

[0009] In one embodiment, the compound of formula (2) is employed as a pharmaceutically acceptable salt, in particular the phosphate salt, and also, in particular, wherein R ¹ is isoamyl.

Brief Description of Drawings

[0010] Figure 1 shows the results of administering NSI-189 to AS and wild type mice on performance in a fear-conditioning test.

[0011] Figure 2 shows the results of administering NSI-189 to AS and wild type mice on long-term potentiation (LTP) assay on hippocampal slices post mortem. Modes of Carrying Out the Invention

[0012] The methods of the invention are directed to ameliorating the cognitive deficiencies associated with AS.

[0013] The active agents useful in the method of the invention have the general formula (1) noted above wherein R ¹ is an alkyl of 3-8C and ring A is a 5 or 6 membered saturated ring optionally including an additional nitrogen or a ring-opened form thereof. Thus, R ¹ may be, in formula (1), a straight or branched chain alkyl group of at least 3C, such as isopropyl, secondary butyl, n butyl, isoamyl, sec-amyl, hexyl, isohexyl and the like or comprise a saturated ring. Preferably in formula (2) or (3), R ¹ is a branched alkyl of 3-5C and, in formula (4), R ¹ comprises a 5- or 6-membered saturated ring. Preferred

embodiments of ring A are a piperidine or piperazine ring or ring opened forms thereof or a pyrrolidine ring.

[0014] Ring A may also be substituted with at least an additional nitrogen-containing substituent, including a substituent that comprises an additional pyridine ring such as pyridyl methyl, or pyridyl ethyl or is a simpler substituent such as a carboxamide.

Preferred forms of ring A are shown in formulas (2), (3) and (4) above along with appropriate substituents.

[0015] The compounds of the invention are typically, but not always, administered in the form of their pharmaceutically acceptable salts such as halides, maleates, succinates, nitrates and the like. Particularly favored are phosphate salts.

[0016] The compounds of the invention are formulated in standard pharmaceutical formulations such as those found in Remington's Pharmaceutical Sciences, latest edition, Mack Publishing Co., Easton, Pennsylvania and include formulations for oral

administration and parenteral administration. Typically, the compounds are administered orally in the form of tablets, capsules or in formulations that are administered as syrups or any other standard formulation. In some instances, the formulations may be designed for delayed release or may be designed for more instantaneous delivery. A variety of formulations that would be suitable for the compounds of the invention is known in the art and is subject to the decision of the practitioner with regard to route of administration.

[0017] Dosage levels also depend on the judgment of the practitioner, but are generally in the range of 0.01 mg/kg to 1 2 g/kg.

[0018] In general, the subjects of the treatment will be humans, although it is useful to employ laboratory animals as well in order to assess appropriate dosages, routes of administration and formulations. Thus, the subjects of the invention include not only humans, but laboratory research animals such as rabbits, rats, mice and the like. In some instances, other mammalian subjects may be appropriate such as in veterinary contexts where the subject may be ovine, bovine or equine or the subject may be a companion animal such as dog or cat.

[0019] In some embodiments, the method of treatment further includes a concomitant diagnostic procedure whereby the effect of the treatment is evaluated at various timepoints during administration and/or after administration of the compositions of the invention. These evaluations include evaluation of, for example, novel place recognition, novel object recognition, object and place recognition and recognition of temporal order. The analyses may also include fear conditioning.

[0020] A particularly useful diagnostic is measurement by CogScreen, a computer- administered cognitive test battery required by the U.S. Federal Aviation Administration (FAA) for evaluation of the neurocognitive functioning of pilots and which has also played a key role in the FDA drug approval and labeling process (CogScreen LLC, St Petersburg, FL). This includes analysis of Shifting Attention Test- Arrow Color Accuracy a measure of executive functioning; Shifting Attention Test-Arrow Direction Reaction Time Correct, a measure of attention; Symbol Digit Coding-Delayed Recall Accuracy, a measure of memory and Shifting Attention Test- Instruction Number Incorrect, which is a measure of working memory. One or a combination of these aspects or a subset thereof may be employed.

[0021] The frequency of administration and dosage schedules is also dependent on the practitioner and the dose may be chronic and on a daily basis, weekly basis or more frequent, or a single dosage may suffice. In typical protocols, the compositions of the invention are administered orally daily for a predetermined time period which may be weeks or months or on a chronic basis. Dosage may be altered or stopped depending on evaluation of the subject as described above. The compounds of the invention may also be administered in combination with other active agents either in the same composition or sequentially.

[0022] As shown in the Examples below, the effect of NSI-189 was tested on hippocampal synaptic plasticity. LTP is a widely accepted model of synaptic plasticity. It also serves a biomarker of memory in animal studies intended to model memory formation/processing in human brain. The LTP assay per se does not infallibly represent cognitive functioning of intact brain in a whole live animal, whether normal or diseased. In the Angelman mouse model, for example, genetic replacement of Ube3A protein in the adult brain could restore LTP but not the neurobehavioral deficits. However, while LTP cannot be used alone to predict potential therapeutic efficacy of a drug on cognitive impairment specifically or brain function generally, it shows a probability of this result. Thus, the results in the Example below relating to fear-conditioning are significant.

[0023] The following examples illustrate, but do not limit the invention,

Example 1

Mouse Model of Angelman' s Syndrome

[0024] Four groups (n=4/5 per group) of young adult mice (age ~3 months) were administered 30mg/kg of the phosphate salt of NSI-189 i.p. daily for 13-15 days for behavior assays and for 18 days prior to termination followed by in vitro LTP assays. The groups included

(1) mice with Angelman syndrome (AS) treated with NSI-189,

(2) mice with Angelman syndrome (AS) treated with vehicle,

(3) wild-type littermates treated with NSI-189, and

(4) wild-type littermates treated with vehicle.

[0025] The behavior assay conducted was fear-conditioning test as diagnostic of hippocampal memory function. As shown in Figure 1, AS mice treated only with vehicle exhibited significantly shortened freezing time following ring-tone, a measure of memory deficit, compared to wild-type mice treated with vehicle. After 2 weeks of treatment with NSI-189 this memory deficit was diminished (p<0.01).

[0026] Subsequent analysis of post-mortem hippocampal slices showed restoration of LTP in AS mice treated with NSI-189 vs. vehicle (p<0.05) (Figure 2). LTP was also improved by administration of NSI-189 in wild type mice.