A CHK1 inhibitor that is selected from the group consisting of (R) -N- (4- (3-aminopiperidin-1-yl) -5-bromo-1H-pyrrolo [2,3-b] pyridine- 3-yl) nicotinamide; (R) -N- (4- (3-aminopiperidin-1-yl) -5-bromo-1 H -pyrrolo [2,3-b] pyridin-3- yl) isobutyramide; (R) -N- (5-Bromo-4- (3- (methylamino) piperidin-1-yl) -1 H -pyrrolo [2,3-b] pyridin-3-yl) nicotinamide; (R) -N- (4- (3-aminopiperidin-1-yl) -5-bromo-1 H -pyrrolo [2,3-b] pyridin-3-yl) -5-methylnicotinamide; (R) -N- (4- (3-Aminopiperidin-1-yl) -5-bromo-1 H -pyrrolo [2,3-b] pyridin-3-yl) cyclopropanecarboxamide; (R) -N- (4- (3-aminopiperidin-1-yl) -5-bromo-1 H -pyrrolo [2,3-b] pyridin-3-yl) -3-methylbutanamide and (R) -N - (4- (3-aminopiperidin-1-yl) -5-bromo-1H-pyrrolo [2,3-b] pyridin-3-yl) -2-cyclopropylacetamide; in combination with a WEE1 inhibitor for use in the treatment of cancer.Un inhibidor de la CHK1 que se selecciona de entre el grupo que consiste en (R)-N-(4-(3-aminopiperidin-1-il)-5- bromo-1H-pirrolo [2,3-b] piridin-3-il) nicotinamida; (R)-N-(4-(3-aminopiperidin-1-il)-5-bromo-1H-pirrolo [2,3-b] piridin-3- il) isobutiramida; (R)-N-(5-bromo-4-(3-(metilamino) piperidin-1-il)-1H-pirrolo [2,3-b] piridin-3-il) nicotinamida; (R)-N-(4- (3-aminopiperidin-1-il)-5-bromo-1H-pirrolo [2,3-b] piridin-3-il)-5-metilnicotinamida; (R)-N-(4-(3-aminopiperidin-1-il)-5- bromo-1H-pirrolo [2,3-b] piridin-3-il) ciclopropanocarboxamida; (R)-N-(4-(3-aminopiperidin-1-il)-5-bromo-1 H-pirrolo [2,3-b] piridin-3-il)-3-metilbutanamida y (R)-N-(4-(3-aminopiperidin-1-il)-5-bromo-1H-pirrolo [2,3-b] piridin-3-il)-2- ciclopropilacetamida; en combinación con un inhibidor de la WEE1 para su uso en el tratamiento del cáncer.