The most relevant in vivo study demonstrated that 177Lu-labeled anti-HER2 nanobody efficiently targeted HER2pos s.c. xenografts in a 5-day follow-up study, while radioactivity levels in normal organs were low (Figure 2(b)).[109] Weekly i.v. administrations of 177Lu-labeled anti-HER2 nanobody in mice with small HER2pos tumors completely prevented tumor growth, while tumors grew exponentially in untreated mice or in mice receiving a control, nontargeting nanobody. The gene discussed is ERBB2; the disease is neoplasm.