The board of OSI Pharmaceuticals has once again rejected a takeover bid from Astellas in Japan, saying its offer of US$3.5bn undervalued the company.

Astellas said it will now take its offer directly to shareholders of the US-based biotechnology company, which focuses on molecular-targeted therapies.

Astellas says it will offer $52 a share in cash for outstanding common shares – news that sent shares of OSI above the offered price to $56.25 on Monday, with the offering being 40% over Friday’s close.

Astellas, which is responsible for the anti-cancer drug Tarveva, says the acquisition could help it become a global leader in oncology.