ALK and neoplasm: The third-generation inhibitor, lorlatinib, has shown more promising activity, including in ALK-TKI–resistant neuroblastoma tumors (18–20); however, some patients eventually recur, and sequencing of serial circulating tumor DNA (ctDNA) samples obtained during treatment has shown the emergence of resistance mutations, including many alterations predicted to activate the RAS-MAPK pathway (21–23).