Canaccord analyst John Newman says one patient at the 375 mg dose of AG-519 experienced grade 2 thrombocytopenia on day 14, an issue not previously seen for AG-348. While today's data is "reasonable," this carries concern, Newman tells investors in a research note after Agios Pharmaceuticals reported multiple ascending dose data for AG-519. Platelet levels began to recover five days after the last dose, and returned to normal seven days after the last dose, but thrombocytopenia could add additional fatigue to pyruvate kinase deficiency patients, complicating treatment, the analyst writes. He keeps a Hold rating on Agios with a $50 price target. The stock is trading down 13%, or $8.50, to $57.59 in morning trading.