MECP2 and Rett syndrome: To evaluate the efficacy of hNGFp as a therapeutic agent for Rett syndrome, 2-month-old female MeCP2+/− mice (i.e. just before the appearance of behavioural deficits) were intranasally treated three times per week with hNGFp or vehicle (PBS) up to a humane sacrifice end point, to determine survival (Fig. 1A).