Crystalline form of pemirolast

1. A hemihydrate form of the sodium salt of pemirolast with 2-Theta values (in degrees) of 13.0±10%, 15.3±10%,18.2±10%, 25.3±10%, 26.6±10%, and 28.4±10%.

2. A compound as claimed in claim 1 , which is substantially crystalline.

3. A process for the preparation of a hemihydrate form of the sodium salt of claim 1 , wherein the process comprises crystallisation from a solvent comprising a lower alkyl alcohol.

4. A process as claimed in claim 3 which further comprises reacting pemirolast with a sodium-containing base prior to the crystallisation.

5. A process as claimed in claim 4 wherein the base is sodium hydroxide or a sodium alkoxide.

6. A process as claimed in claim 3 , wherein the lower alkyl alcohol is methanol or ethanol.

7. A process as claimed in claim 3 , wherein the crystallisation comprises partial dissolution of pemirolast sodium in the solvent, in the presence of no more than about 10% (w/w, as a proportion of the solvent) of water.

8. A process as claimed in claim 7 , which is carried out at a temperature of less than about 70° C.

9. A process as claimed in claim 3 , wherein the crystallisation comprises partial dissolution of pemirolast sodium in an aqueous lower alkyl alcohol at about 72° C. or above.

10. A process for the preparation of a compound as claimed in claim 1 , which comprises dehydration of a higher hydrate of pemirolast sodium.

11. A pharmaceutical formulation comprising a compound as claimed in claim 1 in admixture with a pharmaceutically acceptable adjuvant, diluent or carrier.

12. A combination product comprising:

(a) a compound as defined in claim 1 ; and

(b) one or more active ingredient that is useful in the treatment of an inflammatory disorder, or a pharmaceutically-acceptable salt or solvate thereof.

13. A compound according to claim 1 which is substantially crystallographically pure.