Last week, Aspen Investment disclosed a 9.65% stake in VIVUS (NASDAQ:VVUS) and said it's considering a $640 million purchase, which would be made definitive by June 13.

As senior biotech specialist Brian Orelli and health-care analyst David Williamson discuss in the following video, the key word there is "considering." By the size of its investment, it's clear Aspen thinks VIVUS is undervalued, but it's not clear whether the potential bid is a serious one or just a ploy to try to get the shares higher.

If it is a serious bid, it might not be the best news for Arena Pharmaceuticals (NASDAQ:ARNA) and Orexigen (NASDAQ: OREX), as it would put a floor on the potential price for obesity drugmakers. Arena Pharmaceuticals and Orexigen would be better off if VIVUS was being pursued by a large pharma, as it would give investors confidence that Arena and Orexigen might eventually be taken out by their respective partners, Eisai and Takeda.