Drug maker Amarin (AMRN) is climbing after Germany-based chemical company BASF (BASFY) agreed earlier today to acquire Norway's Pronova BioPharma for $844M. Amarin has developed a prescription fish oil pill used to lower fat in the bloodstream, while Pronova has developed a similar product which it sells to GlaxoSmithKline (GSK). In a note to investors earlier today, research firm Leerink Swann wrote that BASF's acquisition of Pronova is positive for Amarin's stock because the terms of the deal suggest that Amarin is undervalued. BASF bought Pronova for a price equal to three times the amount of Pronova's 2011 sales. At the same multiple, Amarin's current market cap implies that investors expect the company to obtain $667M in revenue from its prescription fish oil pill Vascepa, the firm wrote. Leerink Swann believes that Vascepa's sales will be far above that level, since Pronova's product has had less impressive clinical data but generated $1.3B of revenue last year. The acquisition of Pronova set a high floor value for Vascepa, according to the firm, which reiterated a $27 fair value estimate and Outperform rating on Amarin. In early afternoon trading, Amarin jumped 81c, or 7.72%, to $11.30.