Process for preparing a crystalline form of fluvastatin sodium salt

A process for preparing a crystalline form of fluvastatin sodium salt of formula (I):

• wherein said crystalline form of fluvastatin sodium salt is characterized by X-ray powder diffraction diagnostical peaks expressed in 2-Theta values (2θ) at 3.7±0.2, 11.2±0.2, 14.9±0.2, 15.9±0.2, 17.9±0.2, 18.4±0.2, 21.8±0.2, 25.7±0.2;
• comprising:
• a) dissolving fluvastatin sodium salt of any crystalline form and/or amorphous form by heating said salt in a mixture of acetonitrile/water 20/1 to 20/2.5 v/v, or alternatively in a mixture of acetonitrile/water from 5/1 to 5/2 v/v followed by dilution with acetonitrile to realize a final solvent ratio acetonitrile/water from 20/1 to 20/2.5 v/v;
• b) cooling the solution of step a) to a temperature of from 65° C. to 35° C. to promote fluvastatin sodium salt crystallization and, optionally, seeding the mixture with the above mentioned crystalline form of fluvastatin sodium salt;
• c) further cooling the mixture obtained in step b) to a temperature of from 35° C. to 15° C. and stirring the slurry at said temperature for a time ranging from 1 hour to 3 days;
• d) isolating the fluvastatin sodium salt wet material by filtration or centrifugation of the slurry of step c), wherein said fluvastatin sodium salt has a crystalline form optionally characterized by X-ray powder diffraction diagnostical peaks expressed in 2-Theta values (2θ) at 6.9±0.2, 8.6±0.2, 12.0±0.2, 13.1±0.2, 17.7±0.2, 18.2±0.2;
• wherein the process further comprises:
• e) washing of the wet material obtained in step d) with acetonitrile, a C1-C4 alcohol solvent or a non-polar solvent;
• f) drying the wet solid obtained in step e) under vacuum with a residual pressure range of from 1 mbar to 500 mbar at a temperature of from 20° C. to 60° C. and for a time ranging from 1 hour to 3 days;
• g) re-equilibrating the crystalline form obtained in step f) by treating the solid for a time of from 1 hour to 11 days at a temperature of from 15° C. to 35° C. under relative humidity (RH) of from 40% and 80% to provide fluvastatin sodium salt in a crystalline form characterized by X-ray powder diffraction diagnostical peaks expressed in 2-Theta values (2θ) at 3.7±0.2, 11.2±0.2, 14.9±0.2, 15.9±0.2, 17.9±0.2, 18.4±0.2, 21.8±0.2, 25.7±0.2.