Mizuho analyst Difei Yang says Nightstar Therapeutics is one of her firm's top picks for 2019. The analyst sees an attractive valuation into the mid-2019 data from the Phase 2/3 expansion study in XLRP, which she calls the stock's most important catalyst. If the data are positive, Yang sees "significant upside" of 60% to her $22 price target. Further, downside "appears limited" as the pathway to registration for the Nightstar's most advanced pipeline program in choroideremia is "de-risked" given positive data and alignment with FDA draft guidance on clinical trial design, Yang tells investors in a research note. She reiterates a Buy rating on Nightstar Therapeutics.