A drug used to treat solid tumors that have spread to other parts of the body or cannot be removed by surgery and that got worse after other treatment or cannot be treated with other therapies. It is used in patients whose disease has the NTRK gene fusion but does not have certain mutations (changes) in the TRK protein. It is also being studied in the treatment of other types of cancer. Larotrectinib sulfate blocks the TRK protein, which is involved in cell signaling and cell growth. TRK may be found in a mutated (changed) form or at high levels in some types of cancer cells. Blocking this protein may help keep cancer cells from growing and may kill them. Larotrectinib sulfate is a type of tyrosine kinase inhibitor and a type of targeted therapy. Also called LOXO-101, Trk inhibitor LOXO-101, and Vitrakvi.