NTRK2 and Rett syndrome: The present study reports on the detailed characterization of one such derivative, PTX-BD4-3, in which the terminal hydroxyl groups in the three side-chain moieties were substituted with methyl groups (Fig. 1), and on the in vivo efficacy of PTX-BD4-3 in a mouse model of RTT, a severe neurodevelopmental disorder characterized by reduced BDNF–TrkB signaling (Katz, 2014).