Wells Fargo analyst David Maris believes the positive diabetes data reported by Flexion Therapeutics could be a "major differentiation." Flexion this morning announced that the clinical trial evaluating investigational drug candidate Zilretta for osteoarthritis of the knee in diabetes patients achieved its primary endpoint. It is logical for doctors to use Zilretta with all diabetic osteoarthritis patients and the data "will open the market even further to the indeterminate number of diabetic patients who do not get steroid injections because of the impact on glucose," Maris tells investors in a research note. He calls the stock "substantially undervalued" and keeps an Outperform rating on Flexion with a $29-$31 price target range. The stock is up 5% to $20.00 in early trading.