Germany's BASF has upped its offer by 8% to buy Pronova BioPharma in a bid to win the backing of investors who have yet to offer up their shares in in the Norwegian drugmaker.

BASF is now offering 13.50 kroner per share, up from its original bid of 12.50 kroner made in November. The new offer values Pronova at just shy of 5 billion kroner (about 684 million euros), representing a premium of 34% over the latter's average share price for the previous six months prior to the initial offer.

The Ludwigshafen-headquartered firm is pursuing the deal in a bid to strengthen our position in the fast-growing market for omega-3 fatty acids. Pronova had third-quarter 2012 sales of 427.9 million kroner (+9%), much of which came from Lovaza (omega-3-acid ethyl esters), sold by GlaxoSmithKline in the USA and by Abbott (as Omacor) in Europe and BASF has previously spoken of Pronova's R&D know-how to develop "the next generation of omega-3 solutions".

The German group noted that 70% of shares have been tendered but some shareholders have held out, believing thecash on the table is not enough. The offer expires on January 18 and will not be extended, so the deal is not a foregone conclusion as BASF insists on  having more than 90% of the total share capital of Pronova by then; the latter's board backed the originals offer.

Michael Heinz, responsible for BASF's performance products segment, which includes the nutrition and health division, said that "following a comprehensive due diligence review and taking into account the opportunities and foreseeable risks in Pronova’s business, this increased offer is our last, best and final offer". He added that "our offer represents the full and fair value to all shareholders and that it provides the best solution for Pronova’s stakeholders".