Achillion Pharmaceuticals, Inc. (Achillion) is a biopharmaceutical company primarily focused on the development and marketing of innovative drug products for the infectious disease market. It develops clinical compounds and pre clinical compounds for treating HIV infections, chronic hepatitis C and hospital-based bacterial infections. The company has developed a HIV Capsid Program which will help to prevent HIV replication through interactions with the capsid protein. It is headquartered at Connecticut, the US.

The company inked a license agreement with GCA Therapeutics for elvucitabine, its nucleoside reverse transcriptase inhibitor (NRTI), for the treatment of both hepatitis B virus (HBV) infection and human immunodeficiency virus (HIV) infection.The company reported revenues of (U.S. Dollars) USD 0.23 million during the fiscal year ended 2008, a decrease of 105.79% from 2007. The operating loss of the company was USD 27.93 million during the fiscal year 2008, as compared to an operating loss of USD 30.56 million during 2007. The net loss of the company was USD 28.15 million during the fiscal year 2008, as compared to a net loss of USD 28.10 million during 2007.