(Adds CEO's comment, details on Lilly and Eagle Pharma's patent battle, share movement)
Oct 27 (Reuters) - Eagle Pharmaceuticals Inc said on Friday the U.S. Food and Drug Administration tentatively approved its diluted version of Eli Lilly and Co's blockbuster cancer drug Alimta.
The company's shares, which gained as much as 4.8 percent, closed up 2.9 percent at $55.65.
The drug, Pemfexy, aims to treat patients with advanced stage of non-small cell lung cancer and mesothelioma, a rare type of tumor often caused by asbestos..
The company expects to capture about 25 percent or a third of the market, Chief Executive Scott Tarriff said in an interview.
A final approval - which would allow Eagle Pharma to sell the drug in the United States - is subject to resolution of a patent litigation with Lilly.
Lilly sued Eagle Pharma last month for infringing patents protecting Alimta, which raked in sales of $2.28 billion in 2016.
The drugmaker has so far been largely successful in protecting Alimta, known chemically as pemetrexed, from generic competition due to the drug's vitamin regimen patents.
The patents prevent entry of cheaper versions of the drug through June 2021 in Japan and large European countries, and through May 2022 in the United States.
The so-called vitamin regimen patents addresses methods of administering Alimta following pretreatment with folic acid and Vitamin B12, to reduce the drug's toxicity in patients and allow it to interrupt the ability of cancer cells to reproduce.
(Reporting by Divya Grover in Bengaluru; Editing by Sriraj Kalluvila)