A first aspect of the invention relates to a compound of formula (I), or a pharmaceutically acceptable salt thereof, for use in treating a proliferative disorder, wherein: X is NR7 R1 and R2 are each independently H, alkyl or cycloalkyl R3 is a 6-membered heterocycloalkyl group selected from piperidinyl, piperazinyl, morpholinyl and tetrahydropyranyl, wherein said heterocycloalkyl group is optionally further substituted by one or more (CH2)&mdashR19 groups R4 and R4&prime are each independently H or alkyl or R4 and R4&prime together form a spiro cycloalkyl group Q is CH or N R6 is OR8 or halogen n is 1, 2 or 3 R19 is H, alkyl, aryl or a cycloalkyl group R7 and R8 are each independently H or alkyl and wherein said compound is administered in accordance with a dosing regimen which: (i) maintains a plasma concentration of from about 50 to about 500 nM for a period of up to about 16 hours or (ii) maintains a plasma concentration of from about 0.5 &muM to about 1 &muM for a period of up to about 6 hours or (iii) achieves a maximum plasma concentration (Cmax) of no more than about 500 nM within a period of about 6 hours or (iv) achieves a maximum plasma concentration (Cmax) of no more than about 200 nM within a period of about 16 hours or (v) achieves a maximum plasma concentration (Cmax) of about 0.5 &muM to about 1 &muM within about 6 hours. Further claims relate to a method of treatment based on this dosing regimen, and kits relating to the same.
