Drug compound and purification methods thereof

A method of treating a condition, comprising mixing a lyophilized pharmaceutical composition with a pharmaceutically acceptable solvent to provide a mixture, and administering an effective amount of the mixture to a subject in need thereof, wherein the lyophilized pharmaceutical composition is prepared by a process, wherein the process comprises removing a portion of a solvent by a freeze-drying process from a solution, thereby generating the lyophilized pharmaceutical product, wherein the solution comprises:

• a) a compound of Formula (1):
• or a pharmaceutically-acceptable salt thereof;
• and
• b) the solvent, wherein the solvent comprises DMSO, and
• wherein the freeze-drying process comprises:
• (i) a first freezing stage in which the solution is frozen by reducing a temperature of the solution to about −45° C. to form a frozen solution;
• (ii) a first annealing stage in which the temperature of the solution is raised from about −4° C. to about 0° C., Wherein the solution remains frozen when the temperature of the solution is about 0° C.;
• (iii) a second freezing stage in which the temperature of the solution is lowered from about 0° C. to about −45° C.;
• (iv) a primary drying stage in which the temperature of the solution is raised from about −45° C. to about −6° C., wherein the primary drying stage comprises a sublimation step in which the DMSO is removed by sublimation from the solution in a frozen state of the solution under reduced pressure to give a partially dried product;
• and
• (v) a secondary drying stage in which the temperature of the solution is raised from about −6° C. to about 40° C., wherein in the secondary drying stage the DMSO is removed by evaporation from the partially dried product in a non-frozen state under reduced pressure to give the lyophilized pharmaceutical product, wherein the lyophilized pharmaceutical product comprises a compound of formula (2):
• or a pharmaceutically-acceptable salt thereof, wherein:
• R1 is 4-amino-2H-1λ2,3,5-triazin-2-one or a carbamide, each of which is independently substituted or unsubstituted;
• each R2 and R3 is independently alkyl, which is substituted or unsubstituted;
• or hydrogen;
• and
• R4 is hydrogen or an acyl group, each of which is independently substituted or unsubstituted.

A lyophilized pharmaceutical product, wherein the lyophilized pharmaceutical product is prepared by removing a portion of solvent by a freeze-drying process from a solution, wherein the solution comprises:

• a) a compound of Formula (1)
• or a pharmaceutically acceptable salt thereof;
• b) the solvent, wherein the solvent comprises DMSO, and
• c) a nucleotide-based compound that is not a compound of Formula (1),
• wherein in an amount of the lyophilized composition obtained from 1 gram of the solution, a residual DMSO content is no greater than 20 mg.