* Asahi awarded up to $547 mln in case against Actelion
* Decision puts Actelion under more pressure ahead of AGM
* Actelion facing fire from big holder Elliott Advisors
* Shares tumble over 8 percent, underperform sector index (Adds Elliott statement)
By Katie Reid
ZURICH, May 2 (Reuters) - Shares in Actelion Ltd ATLN.VX tumbled on Monday after a jury decided Asahi Kasei Pharma Corp (3407.T) should be awarded up to $547 million in a licensing dispute, dealing Europe's largest biotech company a hefty blow.
Actelion has said it may appeal against the jury's decision in the Superior Court of the State of California, which concerns a licensing and development dispute with Actelion's unit CoTherix. Actelion bought CoTherix for $420 million in cash in 2007.
The decision puts Actelion under even more pressure ahead of its annual general meeting on Thursday when it will square up to largest shareholder Elliott Advisors, which has accused the $7.7 billion company of squandering shareholder value through its high-risk strategy. [ID:nLDE7400HX]
Elliott suggested late on Monday that the annual meeting should be postponed to give shareholders more time to consider the future of the company in the light of the Asahi case.
Actelion shares closed 8.7 percent lower at 46.51 francs, underperforming a 0.4 percent rise in the Stoxx Europe 600 healthcare sector index .SXDP.
Elliott, which has urged Actelion to consider putting itself up for sale, has proposed its own slate of six drug industry and M&A experts for the company's board, including former Novartis NOVN.VX executive James Shannon, who it wants to chair Actelion.
"The news is a clear negative for Actelion both sentiment-wise and fundamentally. Without the activist process we would struggle to keep the 'buy' rating," Kepler Capital Markets analyst Tero Weckroth said.
"However, we retain our view that Actelion is a logical takeover target. With new board members likely to be elected in the AGM, we retain a 'buy' rating," Weckroth said. <^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Factbox on the Actelion-Asahi case [ID:nLDE74119I]
Preview on shareholder meeting [ID:nLDE73S0I3] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^>
The amount being awarded to Asahi is considerably higher than expected and could further rattle shareholders after a string of product setbacks for Actelion last year.
In a letter to the Actelion board, Elliott repeated its call for a board shake-up and said the case raised questions about Chief Executive Jean-Paul Clozel's leadership going forward.
In a statement later on Monday, Elliott said it believed shareholders needed more clarity and time after the Asahi case to decide on the future of the company and postponing the annual general meeting would be prudent.
"In particular, shareholders need to consider the adequacy of board oversight, the competence of the management, and the use of capital in light of the proposed share buyback," Elliott said.
"At a minimum, this requires a full disclosure of the findings and the potential liability from the Asahi trial and other outstanding legal events."
Two other large shareholders are backing Actelion, which also has support from investor group Ethos, which can be influential in Switzerland, Germany-based independent proxy voting service IVOX and proxy firm Glass Lewis.
"We are not sure that this ongoing legal dispute will prompt several proxy institutions to change their views," said Helvea analysts Olav Zilian.
Actelion said on Monday the criticisms had no factual basis and that it would be able to respond to the letter once the jury had concluded its deliberations on Tuesday.
The jury is set to continue deliberations regarding punitive awards on Tuesday.
At the end of March, Actelion had cash and cash equivalents of 1.4 billion francs.
An arbitration panel in California has already ruled Actelion should pay Asahi $91 million plus interest after the Japanese group disputed the basis for CoTherix's termination of a development agreement. (Additional reporting by Sam Cage; Editing by Greg Mahlich)