MPO and neoplasm: Specific MPO inhibition with 4‐ABAH significantly reduced tumour burden by 48% after 4 weeks compared to vehicle at tumour end‐point (p = 0.041; mean BLI; vehicle, 3.55 × 107 ± 3 × 106 photons/s, compared with treatment with 4‐ABAH, 1.88 × 107 ± 4.48 × 106 photons/s; Figure 5A).