(Reuters) - Several large U.S. funds that boosted their stakes in Allergan Plc (>> Allergan, Inc.) in recent months appear to be optimistic about the company's growth prospects, even before Pfizer's reported $150 billion takeover bid for the botox maker.

Pfizer Inc (>> Pfizer Inc.) is negotiating to buy Allergan, which also makes dry eye treatments, for $370 to $380 per share, a person familiar with the discussions said, compared to its current traded value of around $301.

There is some dissatisfaction, however, with that price range, according to a poll by Sanford C. Bernstein research. Its poll of 87 investors showed that 54 percent wanted $390 to $400 a share, but 36 percent were satisfied with the lower reported price range.

Wells Fargo senior portfolio manager Margaret Patel, whose Diversified Capital Builder Fund owned $2.7 million worth of Allergan at the end of September, said on Thursday Pfizer's reported bid is plenty good.

"I think it’s a big premium over the current valuation, and at some point you have to say, 'Is there any more new good news to be uncovered?"

Apparently so.

Third-quarter fund disclosures reveal that existing Allergan shareholders added a net 10.4 million shares to their holdings. There were newcomers, too.

Geode Capital, the hedge fund unit of Boston-based Fidelity Investments, bought 3.1 million Allergan shares, fund disclosures show. Takeovers have been a staple for the pharmaceutical industry, but investors are not necessarily making acquisition premiums a part of their investment thesis.

In a note last month to investors, hedge fund Lone Pine Capital said it expects Allergan's profits to grow at double-digit rates even without acquisitions that have historically been part of their value-creation formulas. At the end of September, Lone Pine reported owning 2.6 million shares worth $709 million.

Polen Capital sold its remaining stake in Allergan at the end of last year, but only after generating a nearly six-fold return for clients, according to analyst Stephen Atkins.

Funds run by Vanguard Group and T. Rowe Price Group Inc (>> T. Rowe Price Group Inc) are among Allergan's largest investors, owning about 6 percent each of the company's outstanding stock, according to Thomson Reuters data.

A takeover deal would redomicile U.S. drug giant Pfizer in Ireland just as the U.S. Treasury is preparing to clamp down on so-called inversions that limit a company's tax liability. Inversions typically involve a U.S. multinational buying a smaller foreign competitor and relocating to its home country, if only on paper, to escape U.S. taxation.

Inversions figure to be a hot topic in 2016 in a national election year that will determine the next U.S. president.

"We shall see whether the administration and Congress are able to block deals that are largely done based on tax inversions," said Michael Arone, chief investment strategist at State Street Global Advisors' U.S. Intermediary Business in Boston.

Mario Gabelli, whose Gamco Investors owned $23 million worth of Pfizer stock at the end of September, said he would commend Pfizer for making a move to get Allergan and lower its tax rate.

"The U.S. corporate tax structure is uncompetitive," Gabelli said.

(Reporting By Tim McLaughlin; additional reporting by Lawrence Delevingne, Rodrigo Campos, Svea Herbst and Ross Kerber in New York; Editing by Richard Valdmanis, Bernard Orr)

By Tim McLaughlin