MC1R and neoplasm: In addition, [18F]CCZ01096 was considerably stable in vivo with 79.2 ± 1.9% remaining intact in plasma at 15 min p.i. Moreover, co-injection of excess amount of nonradioactive MC1R-taregting peptides abolished uptake of both radiotracers into tumor xenografts, suggesting radioactivity accumulation in SK-MEL-1 tumor xenografts was MC1R mediated.