Abstract: An anti-neoplastic stable pharmaceutical composition comprising Temozolomide, high substituted polysaccharide phosphate in salt form, and high substituted polysaccharide phosphate in acidic form, in particular in a weight ratio of from 5 to 20% Temozolomide to 30 to 80% of polysaccharide in salt form, the reminder up to 100% being polysaccharide in acidic form. The level of 5-aminomidazole-4-carboxamide is below 0.5% by weight of Temozolomide in both the composition and the formulation disclosed. Also disclosed is a hydrogel for intrathecal administration obtainable by contacting the composition with sterile water, a method of manufacture of the composition and uses of the composition and the gel.