UPDATE 2-Alexion's rare blood disorder drug succeeds in late-stage study

(Adds details on Soliris, main goals of trial, updates shares)

March 15 (Reuters) - Alexion Pharmaceuticals Inc said on Thursday its experimental drug to treat patients with a rare blood disorder was shown to be not inferior to its flagship drug, Soliris, which could help the company maintain its lock on that market as competition looms.

Alexion's shares rose as much as 18 percent before settling up nearly 6 percent at $129.70 in premarket trading.

The drugmaker has been under pressure from shareholder Elliott Management and is seeking to restore investor confidence following an exodus of top management and a sales practices scandal related to Soliris, its pricey rare disease treatment.

The future of the company hinges on the successful development of its highly-anticipated drug, ALXN1210, aimed at treating the same rare blood disorder as Soliris.

ALXN1210 could eat into Soliris sales as the experimental drug's dosing schedule is designed to reduce the number of times it needs to be administered to six per year from about 26 with Soliris.

But having two drugs to treat the rare illness could prolong the company's hold on the market and ensure revenue streams.

"This data is consistent with our thesis that ALXN1210 will allow Alexion to extend the IP of their complement franchise from the mid- to late-2020s to 2035", Leerink Partners analysts said, adding the data will likely mitigate many of the competitive concerns.

ALXN1210 was being tested against Soliris in patients with Paroxysmal Nocturnal Hemoglobinuria (PNH) and demonstrated non-inferiority to Soliris on the main goal, as well as four of the key secondary goals.

The main goal of the study was to reduce high levels of cell damage in the blood and lower the use of blood transfusions.

The drug was generally well tolerated with a safety profile that was consistent with that seen for Soliris, the company said.

Soliris, which brought in $3.14 billion in sales in 2017, is already approved for PNH and atypical hemolytic uremic syndrome, and an autoimmune disorder of progressive muscle weakness, generalized myasthenia gravis.

Alexion said it expects to file a marketing application for the drug in the United States, the European Union and Japan in the second half of 2018. (Reporting by Akankshita Mukhopadhyay in Bengaluru; Editing by Maju Samuel, Bernard Orr)