A former partner of Kenneth Griffin, the founder of Citadel Investment Group, has dropped a lawsuit accusing him of fraud, breach of a partnership agreement and misappropriation of trade secrets.

Rush Simonson, a former business partner of Griffin, filed a suit in June claiming the hedge fund mogul stole trading software and strategies the two developed for two hedge funds they managed in the 1980s. The proprietary software and strategies have been used to drive Citadel's success, Simonson alleged in the suit.