A catalyst article for the treatment of an exhaust gas, the catalyst article comprising: a wall-flow filter substrate having inlet channels open at an inlet-end of the substrate and closed at an outlet-end of the substrate, the inlet channels adjacent outlet channels which are closed at the inlet-end of the substrate and open at the outlet-end of the substrate, the wall-flow filter comprising at least first, second and third catalytic layers, wherein: (i) the first catalytic layer extends from the inlet-end of the substrate and comprises a first SCR composition; (ii) the second catalytic layer is provided in or on the walls of the inlet channels, extending from the inlet-end of the substrate, and comprises a PGM-containing composition, wherein: when the second catalytic layer is provided on the walls of the inlet channel, the first catalytic layer is provided on the second catalytic layer, and when the second catalytic layer is provided in the walls of the inlet channels, the first catalytic layer is provided on the walls of the inlet channels; and (iii) the third catalytic layer is provided in or on the walls of the outlet channels, extending from the outlet-end of the substrate, and comprises a second SCR composition; wherein a ratio of the PGMs in the second catalytic layer in g per ft 3 to the total amount of the first and second SCR compositions in the first and third catalytic layers in g per in 3 is from 1.5:8 to 5:8, preferably 2:8 to 4:8, and more preferably 2:8 to 3:8. a wall-flow filter substrate having inlet channels open at an inlet-end of the substrate and closed at an outlet-end of the substrate, the inlet channels adjacent outlet channels which are closed at the inlet-end of the substrate and open at the outlet-end of the substrate, the wall-flow filter comprising at least first, second and third catalytic layers, wherein: (i) the first catalytic layer extends from the inlet-end of the substrate and comprises a first SCR composition; (ii) the second catalytic layer is provided in or on the walls of the inlet channels, extending from the inlet-end of the substrate, and comprises a PGM-containing composition, wherein: when the second catalytic layer is provided on the walls of the inlet channel, the first catalytic layer is provided on the second catalytic layer, and when the second catalytic layer is provided in the walls of the inlet channels, the first catalytic layer is provided on the walls of the inlet channels; and (iii) the third catalytic layer is provided in or on the walls of the outlet channels, extending from the outlet-end of the substrate, and comprises a second SCR composition; (i) the first catalytic layer extends from the inlet-end of the substrate and comprises a first SCR composition; (ii) the second catalytic layer is provided in or on the walls of the inlet channels, extending from the inlet-end of the substrate, and comprises a PGM-containing composition, wherein: when the second catalytic layer is provided on the walls of the inlet channel, the first catalytic layer is provided on the second catalytic layer, and when the second catalytic layer is provided in the walls of the inlet channels, the first catalytic layer is provided on the walls of the inlet channels; and when the second catalytic layer is provided on the walls of the inlet channel, the first catalytic layer is provided on the second catalytic layer, and when the second catalytic layer is provided in the walls of the inlet channels, the first catalytic layer is provided on the walls of the inlet channels; and (iii) the third catalytic layer is provided in or on the walls of the outlet channels, extending from the outlet-end of the substrate, and comprises a second SCR composition; wherein a ratio of the PGMs in the second catalytic layer in g per ft 3 to the total amount of the first and second SCR compositions in the first and third catalytic layers in g per in 3 is from 1.5:8 to 5:8, preferably 2:8 to 4:8, and more preferably 2:8 to 3:8.