David Jackson, the American-born CEO of Dubai’s investment arm Istithmar World, is quitting as the company struggles under a mountain of debt and souring investments.

Jackson’s resignation ends months of speculation about his future amid a series of soured investments that have helped contribute to Istithmar parent Dubai World’s financial woes.

Under Jackson’s leadership, critics have argued Istithmar overpaid for assets such as the Mandarin Oriental Hotel and high-end retailer Barneys New York, relying heavily on debt to finance the acquisitions.

Andy Watson, Istithmar World’s chief investment officer, will serve as acting CEO.