NEW YORK (TheStreet) -- Looks like Pfizer  (PFE) won't be trading its American citizenship for AstraZeneca's  (AZN) U.K. tax rate anytime soon. But investors on say that's just fine. There are plenty of other biotech beauties with attractive foreign tax rates.

$PFE Thank you $AZN for rejecting the offer.

? Jeffrey Pao (@duffryder7) May. 19 at 09:28 AM

AstraZeneca rejected a $118 billion "final offer" from Pfizer Monday morning, sending its shares down 11% in the process and boosting Pfizer's stock about 2%. In a press release, AstraZeneca chairman Leif Johansson said that Pfizer didn't value AstraZeneca's drugs and pipeline as much as its corporate tax rate as a U.K.-based company.

"Pfizer's approach throughout its pursuit of AstraZeneca appears to have been fundamentally driven by the corporate financial benefits to its shareholders of cost savings and tax minimization," Johansson wrote. "From our first meeting in January to our latest discussion yesterday, and in the numerous phone calls in between, Pfizer has failed to make a compelling strategic, business or value case."

Pfizer stood to save a billion dollars a year on taxes by reincorporating in AstraZeneca's home, by some estimates. Britain has an effective 21% corporate tax rate compared to the U.S.'s 40%, according to a KPMG study.

The rejection may be the end of the deal. Pfizer said it will not take its final offer of £55 per share ($93 per share) -- which was increased by $15.3 billion and included 12% more cash than before -- directly to the board in an attempt at a hostile takeover of the company. Pfizer's proposal expires in seven days, at 5 p.m. London time on May 26.

AstraZeneca $AZN Chairman Johansson sees no prospect of Pfizer $PFE deal before May 26th or extension of that deadline

? FinancialJuice (@FinancialJuice) May. 19 at 10:18 AM

If avoiding high U.S. corporate taxes was truly the driving factor for pursuing a merger with a British drug company, there's plenty of foreign biotechs with attractive tax rates that Pfizer -- with its near $189 billion market cap -- could pursue, say StockTwits' users.

One name bandied about is Amarin (AMRN). The biotech firm, which has a $230 million market cap -- a drop in the bucket compared to AstraZeneca's $91.6 billion market cap -- is headquartered in Dublin. The effective corporate tax rate in Ireland is 12.5%.

$AMRN With $AMRN headquarter in Dublin, $PFE Can save a lot of tax after acquiring $AMRN!

? SkyIsLimit (@SkyIsLimit) May. 19 at 08:02 AM

$PFE you can have $AMRN for 8B..:) A savings of $110B plus a potential blockbuster combo therapy with Lipitor+Vascepa..:)

? Andoy Pordoy (@Pordoy) May. 19 at 08:32 AM

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.