Weeks after Jeffrey Epstein died in federal custody in 2019 awaiting prosecution on sex-trafficking charges, JPMorgan Chase filed a report alerting the U.S. government to tens of millions of dollars of potentially suspicious transactions involving him and prominent Wall Street and business figures. The so-called suspicious activity report that JPMorgan filed identified transactions with Leon Black, the co-founder of private equity firm Apollo Global Management; Glenn Dubin, a well-known hedge fund manager; the lawyer Alan Dershowitz; and trusts controlled by Leslie Wexner, the retail tycoon. The nature of the transactions, as well as Mr. Epstein’s role in them, is unclear....