An email to Amarin's corporate press office requesting comment was not immediately returned.

StockTwits' users also suggested GlaxoSmithKline  (GSK). Like AstraZeneca, GlaxoSmithKline is based in the U.K. However, it is much more expensive, with a $132 billion market cap. That's not too far from Pfizer's valuation.

$PFE if they not take $AZN, they will look for another .... maybe $GSK? Or is that to much?

? Nobody (@JackKu) May. 19 at 06:49 AM

Some StockTwits users said Pfizer's cash would be better spent buying biotech companies with the potential for new blockbuster drugs, rather than focusing on a so-called "inversion transaction" to save on taxes. They said that Pfizer needs more innovative drugs in its pipeline than palbociclib, the breast cancer drug that Pfizer submitted to the FDA last week as part of a combo treatment for post-menopausal women suffering from certain types of breast cancer.

StockTwits users suggested Celgene  (CELG), which has a $58.94 billion market cap and is running more than 300 clinical trials, many for cancer drugs. They also mentioned Gilead Sciences  (GILD), the California-based biotech focused on treatments for HIV, with a $125 billion market cap.

@ctymkiw $PFE should just use their cash and purchase other biotech stocks like maybe a $BMRN $GILD $CELG maybe and forget about $AZN

? BiopharmaPro (@BiopharmaPro) May. 19 at 07:50 AM

Still other StockTwits users doubted Monday that Pfizer's bid for AstraZeneca is really over. They argued that there are additional synergies, besides the tax rate, that make AstraZeneca attractive. Pfizer could come back with an improved deal, despite its "final" language, or AstraZeneca's shareholders could revolt and force the board to reconsider.

$PFE will buy $AZN eventually, they want the tax breaks. Just a matter of when AZN will finally accept a bid

? Jared Cummans (@JaredCummans) May. 19 at 09:24 AM

At the time of publication the author held no positions in any of the stocks mentioned.

This article represents the opinion of a contributor and not necessarily that of TheStreet or its editorial staff.

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