Officially undisclosed, because we have a highly respected whistleblower that even the left loves who is pointing to why Merck's acquisition (Pharmasset) previously dropped it... confirming DNA damage, plus... even the DoD refused to fund it, despite Dr. Fauci's advocacy.
Remember, this is how Pharma works, and we likely won't get Pharmasset's original studies until discovery in a future class action lawsuit. By then Merck will have made tens, if not hundreds, of billions of dollars and their liability will be far less. This is just how this works.
We're entering an age of US FDA, NIH and other resignations and whistleblowing, including -- as
@Boston.Knight also pointed out -- the new Alzheimer drug approved over mass, independent, FDA expert rejections and disapproval, in our 'data-free' world. It's rather sickening the conflicts-of-interest and the 'Do something!' political culture we have entered. Heck, the CDC not actually counting 'breakthrough infections' is just more proof that we don't care about the actual data.