(Adds comments from Merck research chief, analysts, details on drugs)
By Ransdell Pierson
June 9 (Reuters) - Merck & Co Inc said Monday it would buy Idenix Pharmaceuticals Inc for $3.85 billion and plans to combine the two companies' most promising drugs to produce a faster, more effective cure for hepatitis C.
Merck said it would pay $24.50 per share, more than three times Idenix's Friday closing price of $7.23.
The payoff for Merck could come from a triple therapy that may cure patients with all genotypes, or strains, of the hepatitis C virus in as little as four to six weeks, its research chief, Roger Perlmutter, said in an interview.
"An ideal therapy means something that works in every hepatitis C-infected patient, irrespective of which genotype," Perlmutter said. "Our goal is to cure everyone quickly using an oral regimen."
The deal comes as drugmakers aim to better compete with Gilead Sciences Inc's Sovaldi, an $84,000 treatment approved in December that generated an unprecedented $2.3 billion in sales in the first few months on the market.
The cost of Sovaldi, which cures well in excess of 90 percent of patients in as little as 8 weeks of treatment, has drawn sharp criticism from insurers and government officials.
Idenix has three drugs in development to treat hepatitis C, most notably a pill in early-stage trials called IDX21437. Like Sovaldi, it is a nucleotide inhibitor - or "nuc" - that blocks a protein needed by the hepatitis C virus to replicate.
Merck hopes to combine IDX21437 with its two high-profile experimental oral treatments, a protease inhibitor called MK-5172 and a so-called NS5A inhibitor called MK-8742 that together received a "breakthrough therapy" designation from the U.S. Food and Drug Administration.
In a recent mid-stage trial, Merck's two-drug combo cured 98 percent of previously untreated patients with genotype 1, the most common and hardest to treat variant of hepatitis C.
The Idenix drug in earlier studies has shown effectiveness against all six main genotypes of hepatitis C, without raising serious safety concerns that have dogged other drugs in its class. Bristol Myers paid $2.5 billion for Inhibitex to get its nuc, but scrapped the drug in 2012 after serious side effects were seen in trials.
Hepatitis C drugs have a history of being expensive, largely because some 170 million people worldwide have the often-fatal liver disease and have not had good treatment options.
Bristol paid a 163 percent premium for Inhibitex. Gilead acquired Sovaldi by agreeing in 2011 to pay $11 billion in cash for biotech company Pharmasset, an 89 percent premium for a company with no marketed products.
Perlmutter said Merck hopes the triple combination will cure patients in 4 to 6 weeks, substantially more quickly than current treatments and those in clinical trials.
LARGER MARKET OPPORTUNITY
Leerink Partners analyst Seamus Fernandez said IDX21437 has not shown any of the skeletal or cardiac toxicity signals that were seen with Bristol's failed drug. Moreover, he said safety of the Idenix drug, at least from preclinical studies, looks very similar to Sovaldi.
"Merck's presentation supports a much larger and longer market opportunity in hepatitis C" than expected, justifying the price of the deal, Baird Equity Research analyst Brian Skorney said in a research note.
Merck and Cambridge, Massachusetts-based Idenix said they expected the transaction to close in the third quarter.
Idenix said in March it was involved in a patent dispute with Gilead related to its hepatitis C treatment in Oslo, Norway.
Credit Suisse acted as the financial adviser to Merck, while Hughes Hubbard & Reed LLP was its legal adviser.
Centerview Partners was Idenix's financial adviser and Sullivan & Cromwell acted as its legal adviser.
Idenix's shares soared 232 percent to $24.03 on Monday. Shares of Achillion Pharmaceuticals, another maker of hepatitis C drugs, jumped 42 percent. Merck's shares were down slightly.
(Additional reporting by Natalie Grover in Bangalore and Bill Berkrot in New York; Editing by Maju Samuel, Kirti Pandey and Nick Zieminski)