As previously reported, Morgan Stanley downgraded Dexcom (DXCM) to Equal Weight from Overweight and lowered its price target to $66 from $87. Analyst David Lewis admits January guidance below the Street is somewhat priced in and solid Q4 results could drive a relief rally, but he does not believe performance would be sustainable given increasing competitive risks in 2017. Lewis said the full impact of Medtronic's (MDT) 670G may not be known and will continue to impact Dexcom's growth moving forward, but his main concerns centers on Abbott's (ABT) Libre, which could be more disruptive, as checks indicate 25-30% of CGMS patients could switch to Libre with a dosing claim. The analyst sees very neutral risk/reward until Libre approval and label clarity are certain.