JPMorgan analyst Jessica Fye downgraded Aptinyx to Underweight from Neutral without a price target. While management is efficiently managing existing cash, cash runway questions "could emerge," Fye tells investors in a research note. Despite the "intriguing" fibromyalgia data, following the large failed phase II study and a lack of meaningful clinical updates over the next 12 months, the shares are likely to underperform, adds the analyst. She believes it would take a positive proof of concept study for NYX-2925, demonstrating clear efficacy on clinical measures, to reverse the negative sentiment on the Aptinyx shares.