Traders said markets were speculating that GlaxoSmithKline, which has a drug partnership with Actelion, could offer 72 Swiss francs (£47.30) per share. Sanofi-Aventis launched a $18.5bn hostile bid for US biotech Genzyme last week, sparking chatter of more M&A in the sector.
Actelion shares, which had lost nearly a quarter of their value this year, closed up 6.6 per cent at 53 francs, outperforming a 0.5 per cent weaker European healthcare sector index. The stock has gained over 30 per cent this month.
Analysts have cited Amgen, Roche, BristolMyersSquibb, AstraZeneca, Bayer and Novartis as possible buyers.