Shares of Icahn Enterprises fell nearly 10% in premarket trading after Hindenburg alleged that the valuation of IEP units was inflated by more than 75% and that "IEP trades at a 218% premium to its last reported net asset value (NAV), vastly higher than all comparables." Icahn Enterprises did not immediately respond to a request for comment and Reuters could not independently verify the claims the short-seller has made in its report. Based in Sunny Isles Beach, Florida, Icahn Enterprises is one of the most successful activist investment firms and the chief investment vehicle of Icahn, who is known for his face-offs with several high-profile firms.