A disposable cassette (1) for storing and delivering a medical drug, the cassette (1) comprising a cartridge (7) containing the medical drug, a waste reservoir (8) arranged to receive waste liquid and/or gas, an injection needle (9) arranged to deliver the medical drug, and a valve block (10) being movable between a first position and a second position. The first position establishes a fluid passage between the cartridge (7) and the waste reservoir (8), while preventing fluid flow from the cartridge (7) to the injection needle (9), and the second position establishes a fluid passage between the cartridge (7) and the injection needle (9), while preventing fluid flow from the cartridge (7) to the waste reservoir (8). The cartridge (7), the waste reservoir (8), the valve block (10) and at least part of the injection needle (9) are arranged inside a cassette housing (2), and the valve block (10) is operable to be moved between the first position and the second position without a user operating the cassette (1) coming into direct contact with parts arranged inside the cassette housing (2).