A) PET/CT imaging of tumour cell death using [18F]FPenM-C2Am in a xenograft model of breast cancer. (B) [18F]FPenM-C2Am tracer for detection of cell death. Maximum intensity projection (M.I.P) of PET signal for a representative tumour-bearing mouse, before (left) and 24 hours after (right) drug treatment (0.4 mg/kg, MEDI3039, i.v.). Images shown were acquired 2 hours after the administration of [18F]FPenM-C2Am (0.25 ug/g, ∼5 MBq, i.v.). Tumour (T), kidneys (K), liver (L) and bladder (B) are shown. A human xenograft model of triple-negative breast cancer (MDA-MB-231) was used. [18F]FPenM-C2Am tracer is comprised of a 16 kDa C2Am protein and a fluorinated maleimide conjugated to cysteine through Michael Addition.