Method for treating non-inflammatory musculoskeletal pain

1 . A method for treating non-inflammatory musculoskeletal pain in a subject, the method comprising administering to the subject a compound of Formula (I)

wherein:

R is hydrogen, lower alkyl, lower alkenyl, lower alkynyl, aryl, aryl lower alkyl, heterocyclic, heterocyclic lower alkyl, lower alkyl heterocyclic, lower cycloalkyl or lower cycloalkyl lower alkyl, and R is unsubstituted or is substituted with at least one electron withdrawing group, and/or at least one electron donating group;

R 1 is hydrogen or lower alkyl, lower alkenyl, lower alkynyl, aryl lower alkyl, aryl, heterocyclic lower alkyl, lower alkyl heterocyclic, heterocyclic, lower cycloalkyl, or lower cycloalkyl lower alkyl, and is unsubstituted or substituted with at least one electron-withdrawing group and/or at least one electron-donating group;

R 2 and R 3 are independently hydrogen, lower alkyl, lower alkenyl, lower alkynyl, aryl lower alkyl, aryl, halo, heterocyclic, heterocyclic lower alkyl, lower alkyl heterocyclic, lower cycloalkyl, lower cycloalkyl lower alkyl, or Z-Y, wherein R 2 and R 3 are each independently unsubstituted or substituted with at least one electron-withdrawing group and/or at least one electron-donating group;

Z is O, S, S(O) a , NR 4 , NR′ 6 , PR 4 or a chemical bond;

Y is hydrogen, lower alkyl, aryl, aryl lower alkyl, lower alkenyl, lower alkynyl, halo, heterocyclic, heterocyclic lower alkyl, or lower alkyl heterocyclic, and is unsubstituted or substituted with at least one electron-withdrawing group and/or at least one electron-donating group, provided that when Y is halo, Z is a chemical bond, or

Z-Y taken together is NR 4 NR 5 R 7 , NR 4 OR 5 , ONR 4 R 7 , OPR 4 R 5 , PR 4 OR 5 , SNR 4 R 7 , NR 4 SR 7 , SPR 4 R 5 , PR 4 SR 7 , NR 4 PR 5 R 6 , PR4NR5R7, N + R 5 R 6 R 7 ,

R′ 6 is hydrogen, lower alkyl, lower alkenyl, or lower alkynyl, and is unsubstituted or substituted with at least one electron-withdrawing group or/and at least one electron-donating group;

R 4 , R 5 and R 6 are independently hydrogen, lower alkyl, aryl, aryl lower alkyl, lower alkenyl, or lower alkynyl, and are each independently unsubstituted or substituted with at least one electron-withdrawing group or/and at least one electron-donating group;

R 7 is R 6 , COOR 8 , or COR 8 , and is unsubstituted or substituted with at least one electron-withdrawing group or/and at least one electron-donating group;

R 8 is hydrogen, lower alkyl, or aryl lower alkyl, and is unsubstituted or substituted with at least one electron-withdrawing group or/and at least one electron-donating group;

n is 1-4; and

a is 1-3;

or a pharmaceutically acceptable salt thereof.

2 . The method of claim 1 , wherein, in the compound of Formula (I), one or both of R 2 and R 3 are heterocycles independently selected from the group consisting of furyl, thienyl, pyrazolyl, pyrrolyl, methylpyrrolyl, imidazolyl, indolyl, thiazolyl, oxazolyl, isothiazolyl, isoxazolyl, piperidyl, pyrrolinyl, piperazinyl, quinolyl, triazolyl, tetrazolyl, isoquinolyl, benzofuryl, benzothienyl, morpholinyl, benzoxazolyl, tetrahydrofuryl, pyranyl, indazolyl, purinyl, indolinyl, pyrazolindinyl, imidazolinyl, imidazolindinyl, pyrrolidinyl, furazanyl, N-methylindolyl, methylfuryl, pyridazinyl, pyrimidinyl, pyrazinyl, pyridyl, epoxy, aziridino, oxetanyl, azetidinyl, and when N is present in the heterocycle, N-oxides thereof; said heterocycles being independently unsubstituted or substituted with at least one electron-withdrawing group and/or at least one electron-donating group.

3 . The method of claim 1 , wherein the compound is of Formula (III)

wherein:

R 4 is one or more substituents independently selected from the group consisting of hydrogen, halo, alkyl, alkenyl, alkynyl, nitro, carboxy, formyl, carboxyamido, aryl, quaternary ammonium, haloalkyl, aryl alkanoyl, hydroxy, alkoxy, amino, alkylamino, dialkylamino, aryloxy, mercapto, alkylthio, alkylmercapto and disulfide;

R 3 is selected from the group consisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, aryl, N-alkoxy-N-alkylamino and N-alkoxyamino; and

R 1 is alkyl.

4 . The method of claim 3 , wherein, in the compound of Formula (III),

R 4 is one or more substituents independently selected from the group consisting of hydrogen and halo;

R 3 is selected from the group consisting of lower alkoxy lower alkyl, aryl, N-lower alkoxy-N-lower alkylamino, and N-lower alkoxyamino; and

R 1 is lower alkyl.

5 . The method of claim 4 , wherein, in the compound of Formula (III), R 3 is lower alkoxy lower alkyl.

6 . The method of claim 3 , wherein, in the compound of Formula (III),

no more than one R 4 substituent is fluoro and all others are hydrogen;

R 3 is selected from the group consisting of methoxymethyl, phenyl, N-methoxy-N-methylamino, and N-methoxyamino; and

R 1 is methyl.

7 . The method of claim 3 , wherein, in the compound of Formula (III),

R 4 is hydrogen;

R 3 is methoxymethyl; and

R 1 is methyl.

8 . The method of claim 3 , wherein the compound of Formula (III) is selected from the group consisting of

(R)-2-acetamido-N-benzyl-3-methoxy-propionamide;

(R)-2-acetamido-N-benzyl-3-ethoxy-propionamide;

O-methyl-N-acetyl-D-serine-m-fluorobenzylamide;

O-methyl-N-acetyl-D-serine-p-fluorobenzylamide;

N-acetyl-D-phenylglycinebenzylamide;

D-1,2-(N,O-dimethylhydroxylamino)-2-acetamide acetic acid benzylamide; and

D-1,2-(O-methylhydroxylamino)-2-acetamide acetic acid benzylamide.

9 . The method of claim 3 , wherein the compound of Formula (III) is substantially enantiopure.

10 . The method of claim 3 , wherein the compound of Formula (III) is lacosamide.

11 . The method of claim 10 , wherein the lacosamide is administered at a dose of about 50 mg to about 6 g/day.

12 . The method of claim 10 , wherein the lacosamide is administered at a dose of about 100 to about 1000 mg/day.

13 . The method of claim 10 , wherein the lacosamide is administered at a dose of about 200 to about 600 mg/day.

14 . The method of claim 10 , wherein the lacosamide is administered at a dose resulting in a plasma concentration of about 0.1 to about 15 μg/ml (trough) and about 5 to about 18.5 μg/ml (peak), calculated as an average over a plurality of treated subjects.

15 . The method of claim 3 , wherein the compound of Formula (III) is administered according to a regimen wherein daily doses are increased until a predetermined daily dose is reached which is maintained during further treatment.

16 . The method of claim 3 , wherein the compound of Formula (III) is administered in one to three doses per day.

17 . The method of claim 3 , wherein the compound of Formula (III) is administered orally or intravenously.

18 . The method of claim 1 , wherein the musculoskeletal pain is associated with fibromyalgia, myofascial pain syndrome or back pain.

19 . The method of claim 1 , further comprising administering a further active agent effective for treating non-inflammatory musculoskeletal pain.

20 . The method of claim 19 , wherein the further active agent comprises an analgesic, an anticonvulsant, an antidepressant or an NMDA receptor antagonist.

21 . The method of claim 19 , wherein the further active agent comprises an anticonvulsant selected from the group consisting of carbamazepine, phenyloin, gabapentin, pregabalin, lamotrigine, levetiracetam, pharmaceutically acceptable salts thereof, and combinations thereof.

22 . The method of claim 19 , wherein the further active agent comprises at least one analgesic agent selected from the group consisting of opioid and non-opioid analgesic, steroidal anti-inflammatory agents, NSAIDs and COX-2 selective inhibitors.