But optimism in biotech abounds. Of 18 chief executives in pharma and biotech interviewed by CNBC at the JPMorgan Health Care Conference this month, only two said the sector is in a bubble. And all said it's likely to outperform the broader market this year.
What's behind that? The same trends that have been driving biotech for the last few years: a record number of new drugs approved by the Food and Drug Administration in 2014, improvements in technology (particularly in genome sequencing, expected to be a large part of President Barack Obama's recently announced precision medicine initiative) and low interest rates, which help drive acquisitions, analysts said.
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"If you have low interest rates, that means cost of capital is relatively cheap," said Funtleyder. "It encourages M&A on the part of large pharma because they're not getting any money on their money, so they may as well put it to work."
Would-be acquirers, though, including Pfizer CEO Ian Read, have noted valuations in some sectors are high.
"The starting points of the prices are somewhat buoyant, shall we say," Read said on Pfizer's Jan. 27 earnings call with analysts. "That does give you some concern when you look at the prices or premiums you need."
Yet deal activity through 2014 was hot, with companies from Idenix to InterMune to Cubist being snatched up at multibillion-dollar prices.
And, noted RBC's Simeonidis, even the boom in offerings last week looks more tempered when one considers half the capital was raised by just two companies: BioMarin and Alnylam.
"There is always great demand for high-quality companies," Simeonidis said in a telephone interview. The fact that many IPOs are still oversubscribed makes him believe the momentum will continue, he said.
"At some point there's an overabundance of offerings," Simeonidis said. The question is: When do we get there?