Vertex, Idenix climb on rival’s stumble

David L Ryan/Globe Staff Photo/File
Vertex Pharmaceuticals’ new headquarters rises along Fan Pier.

Locals Vertex Pharmaceuticals and Idenix Pharmaceuticals climbed after rival Gilead Sciences Inc. plunged after some patients on an experimental hepatitis C medicine relapsed after they stopped therapy. Gilead jumped into the race to develop a hepatitis C drug when it acquired Pharmasset Inc. for $10.8 billion. Gilead shares fell nearly 15 percent to $46.82. Vertex joined Merck & Co. last year in gaining approval for the first new hepatitis C drugs in almost a decade. Idenix also has developed medicines for the disease.