The announcement comes as regulators investigate the company's handling of sexual harassment claims. Ex-board member Elaine Wynn claimed in legal filings that she told Kim Sinatra about an alleged 2005 incident between Steve Wynn and a manicurist at the resort. Kim disputed Elaine Wynn's account.

David Katz, a Jefferies LLC analyst, said in a note that Sinatra’s exit was “reflective of the pressure the company’s management team is facing in the near term from regulators and shareholders”. 

Six other board members have announced their departure since February. 

Wynn previously served as CEO and Chair of Mirage Resorts before founding Wynn Resorts in 2002, turning the company into a multinational multi-billion dollar enterprise and amassing a personal fortune of over $3.3bn. He has been investigated in relation to the sexual harassment allegations by regulators in Nevada, Massachusetts and Macau, where Wynn operates a number of hotels.

In the wake of Steve Wynn’s resignation, the company appointed Matt Maddox, former President of the company, as its CEO.