CVS Health CEO Karen Lynch has resigned amid financial struggles and significant declines in stock value, with David Joyner appointed as her successor. The company has faced mounting challenges, including rising medical costs, particularly in its Medicare Advantage plans, and declining quality ratings. CVS has lowered its earnings forecasts multiple times this year, with upcoming third-quarter earnings expected to fall below previous guidance. The company has also been subject to pressure from activist investors and a Federal Trade Commission lawsuit. Joyner, a veteran with deep knowledge of CVS's operations, is expected to lead the company through these turbulent times. The leadership change reflects a broader trend, with CVS and other major pharmacy chains struggling under financial and operational pressures.