Hospital operator Prospect Medical Holdings, a large tenant of the biggest hospital landlord in the U.S., is working with restructuring advisers to explore options to address its financial challenges, according to people familiar with the company. The closely held hospital chain with facilities in states including California, Pennsylvania, Rhode Island and Connecticut has struggled financially for years and recently skipped rent payments owed to landlord Medical Properties Trust, a publicly traded healthcare real-estate investment trust. Prospect faces pressure from regulators in several states over its financial troubles and the deteriorating conditions at its facilities.