Investors need to change their approach to investing in pharmaceutical companies that are working to develop life-altering treatments, former Aetna Chairman and CEO Mark Bertolini told CNBC on Friday.
Bertolini, who resigned from his posts at Aetna last year after the insurer's $69 billion merger with CVS Health, said investors currently are trading "on a basis that says, 'does this drug work today? Did this trial pass today?''"
"The investment model in drug development is all wrong," he said in an interview with "Squawk Box." Drugmakers such as Biogen are "doing research, they're doing applied science to try and find a way to commercialization. That's what they should be doing."
Bertolini spoke a day after Biogen's stock posted its worst day in 14 years after the Cambridge, Massachusetts-based biotechnology company terminated the trial of Alzheimer's disease drug aducanumab, which it had been developing in partnership with Japanese pharmaceutical company Eisai.
As many as 5.5 million Americans over the age of 65 suffer from Alzheimer's, a progressive disease that often affects memory, thinking and behavior.
Biogen's experimental drug targeted a compound in the brain known as beta amyloid, which was believed by many scientists and drugmakers to play a role in the devastating disease. An independent audit revealed the drug was unlikely to work.
The biotech company joins a long list of companies that have failed to successfully treat the disease. Wall Street viewed Biogen's setback on Thursday as the industry essentially going back to the drawing board when it comes to curing Alzheimer.
Bertolini called Biogen's stock plummet of more than 29 percent on Thursday "crazy" and not "realistic."
Bertolini joined CNBC to discuss health care and his new book, "Mission-Driven Leadership: My Journal as a Radical Capitalist."