On Thursday, First Republic Bank stock FRC plunged another 15% in premarket trade amid exploration of its strategic options, including a possible sale of the company. Bloomberg reported late Wednesday that the San Francisco-based bank, which was caught in the blow of Silicon Valley Bank’s failure last week and two other lenders, was downgraded Wednesday to junk territory by S&P Global Ratings and Fitch Ratings. Was. Citing concerns about flighting deposits in large banks considered safe. A spokeswoman for First Republic declined to comment to MarketWatch. JP Morgan said early Thursday that…