U.S.-listed shares of AstraZeneca /zigman2/quotes/200304487/composite AZN -0.39% were up 2.5% in trading on Tuesday after the company said an experimental therapy for hereditary transthyretin-mediated amyloid polyneuropathy met its primary endpoints in a Phase 3 clinical trial. AstraZeneca is developing eplontersen with Ionis Pharmaceuticals Inc. /zigman2/quotes/201272020/composite IONS +5.57% ; shares in Ionis were up 5.1% on Tuesday. The rare disease can cause nerve damage and motor disability and affects about 40,000 people worldwide, the companies said. They also said they plan to seek Food and Drug Administration approval for eplontersen this year. AstraZeneca's stock has gained 7.5% so far this year, while the broader S&P 500 /zigman2/quotes/210599714/realtime SPX -0.16% is down 22.9%.