Susquehanna International and Citadel Securities, the U.S. options market makers acting as plaintiffs, have sharply narrowed the suspected scope of the Futu-Tiger options insider trading case to 47 accounts controlled by 45 people, Caixin reported. After more than a month of collecting brokerage data and reviewing trades account by account, the firms compared metrics including trading profit, return rate, contract volume, expiry dates, brokers, location and position-building timing. The latest review pushed the total alleged illicit profit to $155 million. Most of the 45 people are outside the United States, with many living in mainland China and Hong Kong. One person controlled three accounts. Individual gains ranged from several hundred thousand dollars to tens of millions of dollars. Options contracts, which can magnify gains through leveraged exposure, appear central to why a relatively limited number of accounts could generate such large alleged profits.