Alexion Pharmaceuticals, Inc. ALXN announced that the late-stage study evaluating its long-acting C5 complement inhibitor, Ultomiris, in adults with generalized myasthenia gravis (gMG), a rare autoimmune disorder characterized by severe muscle weakness, met its primary endpoint.The global phase III randomized, double-blind, placebo-controlled, multicenter 26-week study, which enrolled 175 patients across North America, Europe, the Asia-Pacific and Japan, evaluated the safety and efficacy of Ultomiris in adults with gMG who were not previously treated with a complement inhibitor medicine.Ultomiris showed compelling efficacy as early as week 1 and sustained for 52 weeks. The study met its primary endpoint of change from baseline in the Myasthenia Gravis-Activities of Daily Living Profile (MG-ADL) total score at week 26, with high statistical significance. In addition, the positive treatment effect was maintained through a total of 52 weeks for the subset of patients who have completed 26 weeks in the extension study to date.Based on the positive data from the study, Alexion plans to make regulatory filings in the United States, the European Union and Japan, in late 2021 or early 2022.The study results showed that Ultomiris may help a broader range of patients than those studied in the phase III trial of lead drug, Soliris, which is also approved for gMG. It included those with milder symptoms or who are earlier in their treatment journey. The drug can also reduce the patient burden with its less frequent dosing schedule.A potential label expansion of the drug will boost its sales, which came in at $346.9 million in the first quarter of 2021. The drug is approved for paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS) to inhibit complement-mediated thrombotic microangiopathy (TMA) in adult and pediatric (one month of age and older) patients.Shares of the company have surged 15.6% against the industry’s decline of 4%.Image Source: Zacks Investment ResearchAlexion is set to be acquired by AstraZeneca AZN, whereby the former’s shareholders will receive $60 in cash and 2.1243 AstraZeneca American Depositary Shares (ADSs) for each Alexion share. The acquisition has obtained clearance from regulatory bodies across the world.Alexion currently carries a Zacks Rank #2 (Buy). Other similar-ranked stocks in the sector include Zoetis Inc. ZTS and Repligen RGEN. You can see the complete list of today’s Zacks #1 Rank (Strong Buy) stocks here.Zoetis’ earnings estimates are up 8 cents for 2021 and 9 cents for 2022 over the past 90 days. The stock has rallied 20.1% year to date.Repligen’s earnings estimates for 2021 have increased to $2.26 from $1.91 in the past 90 days. The stock has rallied 3.1% year to date. More Stock News: This Is Bigger than the iPhone! It could become the mother of all technological revolutions. Apple sold a mere 1 billion iPhones in 10 years but a new breakthrough is expected to generate more than 77 billion devices by 2025, creating a $1.3 trillion market. Zacks has just released a Special Report that spotlights this fast-emerging phenomenon and 4 tickers for taking advantage of it. If you don't buy now, you may kick yourself in 2022.Click here for the 4 trades >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report AstraZeneca PLC (AZN): Free Stock Analysis Report Alexion Pharmaceuticals, Inc. (ALXN): Free Stock Analysis Report Repligen Corporation (RGEN): Free Stock Analysis Report Zoetis Inc. (ZTS): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research