Moderna’s top leaders sold company stock as the share value skyrocketed. : As shares of biotech firm Moderna soared in May to record highs on news that its novel coronavirus vaccine showed promise in a clinical trial, the nation’s senior securities regulator was asked on CNBC about news reports that top executives had been selling their stock in the company. Jay Clayton, chairman of the Securities and Exchange Commission, responded that companies should avoid even the appearance of impropriety. “Why would you want to even raise the question that you were doing something that was inappropriate?” he said.