Spindle drive for horizontal adjustment of a motor vehicle seat

The drive has an adjusting mechanism containing a drive screw and a spindle nut, where the drive screw is connected with a drive device. An outer toothing of the spindle nut is in engagement with an outer toothing of the drive screw. An inner toothing of the spindle nut is in engagement with an outer thread of a spindle. A hybrid spindle nut (3) is provided with a functional part (7) and fixed parts (8, 8'), where the functional part is arranged in force flow between the drive screw and the spindle. The fixed part deflects crash forces from an adjusting rail into the spindle. The fixed part contains a hard-metallic material i.e. steel.