Vitamin retail giant GNC has filed for bankruptcy protection and may close as many as 1,200, or a fifth, of its U.S. stores. The company, which is now seeking a buyer, had faced financial troubles since before the coronavirus pandemic, seeing declining sales and holding almost $1 billion of debt. But widespread lockdowns prevented the company from following through with its refinancing plans. GNC officials say they plan to emerge from bankruptcy this fall, with $130 million in financing from vitamin supplier IVC.