Creatine prodrugs, compositions and methods of use thereof

A method for treating creatine deficiency in a patient in need thereof, comprising administering to the patient a therapeutically effective amount of a compound of Formula (I):

• or a pharmaceutically acceptable salt or solvate thereof;
• wherein:
• R is —CH3, —CH2D, —CHD2, or —CD3;
• R2 is hydrogen, —C(O)NHR5, —C(O)OR5, —C(O)(linear or branched alkyl), or —C(O)(linear or branched alkenyl);
• R3 is —C(O)OR6;
• R4 is halogen, —OH, —OR5, oxo, —NH2, —NHR5, —N(R5)2, —NO2, —CF3, —C1-C6 alkyl, or —C1-C6 haloalkyl;
• R5 is linear or branched alkyl;
• R6 and R1 together is an alkylene group or an alkenylene group which with the atoms which they are each bonded to, forms a 12 to 25 membered ring, wherein 1, 2, 3, or 4 —CH2-units making up the alkylene group or the alkenylene group is optionally replaced with a heteroatom selected from —O—, —S—, or —N—, provided that no adjacent —CH2— is replaced;
• wherein the alkylene group or the alkenylene group is optionally substituted with one or more R4;
• and
• wherein, two R4 on the same or adjacent carbon can form a 3 to 6 membered fused or spiro cycloalkyl ring or a 3 to 6 membered fused or spiro heterocyclic ring.