"Achillion Pharmaceuticals Incs experimental hepatitis C drug when used with Gilead Sciences Incs Sovaldi eradicated signs of the virus in six weeks the shortest duration and highest response achieved by any twodrug treatment.  Achillions shares rose as much as  percent to . on Monday on investors hopes that an allAchillion combination could be as effective as Gileads and AbbVie Incs current therapies.  The estimated  billion market for hepatitis C drugs has developed at a lightning pace in recent years with several companies including Gilead AbbVie and Merck  Co Inc working on faster more potent ways to cure the liverdestroying virus which affects more than  million globally.  The newgeneration hepatitis C regimens use a two to threedrug combination  a nucleotide analog inhibitor or nuke and a NSA inhibitor in Gileads case  to achieves a cure in about eight to  weeks making them faster and more effective than older treatment options.  Gileads regimen Harvoni with its own NSA inhibitor and Sovaldi as the nuke needs to be taken for at least eight weeks. Launched in October its sales touched . billion in the quarter ended Dec. .  AbbVies threedrug cocktail Viekira Pak which won U.S. approval in December must be taken for at least  weeks.  Achillions ongoing midstage study tests its NSA inhibitor ACH with Sovaldi in previously untreated genotype  hepatitis C patients over six and eight weeks of therapy.  The main goal is to achieve a cure or sustained virological response  weeks after the completion of therapy.  Mondays data shows Achillions NSA inhibitor ACH looks bestinclass which could make up for its nuke ACH being perhaps less effective than Sovaldi analysts said.  The question then becomes whether ACH plus ACH  a weaker nuke and a stronger NSA inhibitor  could be a good enough doublet as Harvoni William Blairs Katherine Xu said.  Achillion one of the few companies developing hepatitis C therapies independently plans to begin a midstage study this year to evaluate its proprietary doublet.  The allAchillion regimen could hit the U.S. market by  in a conservative scenario Deutsche Banks Alethia Young estimated. She expects the treatment to cost about  per patient per year assuming a  percent discount.  Harvonis list price is  and Viekira Pak is estimated to cost .  Editing by Ted Kerr and Savio DSouza Our StandardsThe Thomson Reuters Trust Principles. httpthomsonreuters.comenaboutustrustprinciples.html"