The present invention provides a pharmaceutical combination comprising the EP4 antagonist of Formula (R)-4-(1-(6-(4-(trifluoromethyl)benzyl)-6-azaspiro[2.5]octane-5-carboxamido)cyclopropyl)-benzoic acid or a pharmaceutically acceptable salt thereof and at least one immune checkpoint inhibitor, preferably the sodium salt of (R)-4-(1-(6-(4-(trifluoromethyl)benzyl)-6-azaspiro[2.5]octane-5-carboxamido)cyclopropyl) benzoic acid. A polymorphic form A of sodium salt of (R)-4-(1-(6-(4-(trifluoromethyl)benzyl)-6-azaspiro[2.5]octane-5-carboxamido)cyclopropyl)benzoate characterized by a powder XRD spectrum with peaks at values of the angle 2θ ±0.2° of 4.3, 5.0, 5.8, 6.4, 7.1, 8.3, 8.7, 12.8, 15.3, 15.9 is also described. The combination and the polymorphic form A are described for use in the treatment of tumours.
