NTRK1 and hepatocellular carcinoma: Herein, a disulfide bond-contained polypeptide nanogel, methoxy poly(ethylene glycol)−poly(l-phenylalanine-co-l-cystine) [mPEG−P(LP-co-LC)] nanogel, which could be responsive to the intracellular reduction microenvironments, was developed to deliver lenvatinib (LEN), an inhibitor of multiple receptor tyrosine kinases, for HCC therapy.