CVS has been struggling after it repeatedly missed profit targets and said third-quarter earnings would be well below Wall Street's expectations. The stock price has fallen more than 26% since the start of the year and fell more than 8% following news of Lynch's departure.

“The board believes this is the right time for change and we are confident that David is the right person to lead our company for the benefit of all stakeholders, including customers, employees, patients and shareholders,” said Roger Farah. who was named executive chairman of CVS after previously serving as chairman of the board.

When the Fortune 500 list was released in June of this year, only 10.4%, or 52 CEOs, were women. While that's a big jump from the 24 female leaders who made the list in 2018, overall progress has stalled and Lynch's departure is a setback for a group that was small to begin with. This slowdown could be due to a decline in executive turnover since the pandemic.

Today, 55 women lead Fortune 500 companies — mining company Freeport-McMoRan and trucking company JB Hunt Transport both hired female CEOs this year. Oil giant Marathon Petroleum and financial consultancy Freddie Mac also recently appointed female CEOs.