ALLSCHWIL, Switzerland, April 13 (Reuters) - Swiss biotech group Actelion has never received a takeover offer but the board would consider a bid for the company at the right price, its chairman told Reuters. Elliott Advisors, a New York-based fund, which holds nearly 6 percent of the $7.5 billion company, has urged Actelion to consider putting itself up for sale after a spate of product setbacks last year and has called on it to disclose any offers it may have received.