Update (4:35 p.m.): Updated with Monday market close information.
NEW YORK (TheStreet) -- Gilead Sciences (GILD) fell Monday amid news that Merck (MRK) would purchase biotechnology company Idenix Pharmaceuticals (IDIX) for $3.85 billion as it tries to strengthen its position in the increasingly competitive hepatitis C sector.
Gilead is currently the leader in the hepatitis C drug market with its pill Sovaldi. Merck's acquisition of Idenix could provide stronger competition for Gilead.
Merck will pay $24.50 a share in cash for Idenix, more than triple the company's closing price of $7.23 on Friday.
"Idenix has established a promising portfolio of hepatitis C candidates,'' said Dr. Roger Perlmutter, the president of Merck Research Laboratories, in a statement Monday.
Gilead closed down 4.11%, or $3.39, to $79. More than 23.2 million shares changed hands, which beat the average volume of 16,490,200.
For more on this story, read TheStreet's Adam Feuerstein's article here.