There is provided a compound of formula (I): or a pharmaceutically acceptable salt thereof, wherein Y, Z and R 1 to R 6 have meanings given in the description, for use in the treatment of melanoma or renal cancer by administration of said compound, in the same or separate pharmaceutical composition, with paclitaxel or a paclitaxel analog. There is also provided the use of a compound of formula (I) for the production of a medicament for administration, in the same or separate pharmaceutical composition, with paclitaxel or a paclitaxel analog, for treating melanoma or renal cancer.
