NEW YORK (TheStreet) -- Merck's (MRK - Get Report) CEO may say he's against big mergers. But the pharmaceutical giant is clearly open to snapping up medium-sized biotech companies.

Merck proved its willingness to acquire multi-billion-dollar biotechs Monday with its $3.85 billion acquisition of Idenix  (IDIX), a drug company focused on treatments for human viral diseases including hepatitis B and C and HIV/AIDS.

The acquisition undermines comments made by Merck CEO Ken Frazier in an April earnings conference call that Merck would drive shareholder value through "innovation rather than consolidation." And it spurred investors on to debate the next biotech that could be consumed by Merck or another pharma giant.

$IDIX deal has made it clear that pipeline and technology platform are very important. $CLVS $SNTA (HDC platform) $PPHM

? Catalystinvestor (@Catalystinvestor) Jun. 9 at 11:05 AM

Merck entered a definitive agreement to buy Idenix for $24.50 per share in cash. The stock jumped 233.33% Monday morning to $24.10, reflecting the merger costs that could slightly erode the purchase price.

Merck said Idenix's "promising portfolio" of hepatitis C treatment candidates was the main driver of the deal. "Idenix's investigational hepatitis C candidates complement our promising therapies in development and will help advance our work to develop a highly effective, one-daily, all oral, ribavirin-free, pan-genotypic regimen that has a duration of treatment as short as possible for millions of patients in need around the world," said Merck Research Laboratories president Roger Perlmutter.

Merck has its own hepatitis C drugs in development, including two in late-stage trials for FDA drug approval called MK-5172 and MK-8742. About 3.2 million Americans have the disease, which can destroy the liver, according to the U.S. Center for Disease Control.

It's possible that Merck does not consider the acquisition a mega-merger. Merck's Frazier did say in April that the company would pursue "value-added bolt-on opportunities," according to a transcript. For a $169 billion company like Merck, perhaps anything under $10 billion that promises to augment drugs in the current pipeline qualifies as a "bolt-on."

Some investors on believe Merck may consider purchasing another biotech with antiviral vaccines in order to control the space. Inovio Pharmaceuticals  (INO - Get Report) is a name often mentioned. The company, which develops synthetic DNA vaccines to treat hepatitis C, influenza and HIV, has a $621.42 million market cap. It is currently conducting human trials for a hepatitis C drug, influenza vaccines and an HIV vaccine.

Traders betting on Inovio to be next Idenix? $INO (also has hep C treatment) up 5% & top trender on StockTwits. $IDIX up 233% on $MRK deal??

? John L. Bair (@JohnLBair1) Jun. 9 at 11:38 AM

Another name mentioned is MannKind  (MNKD - Get Report). The company, which has an inhaled insulin treatment for diabetics awaiting final approval from the FDA, has run up nearly 166% on speculation of a takeover from the likes of Merck.

$MNKD At shareholders meeting, Al did say "we have not considered trying to market MKND and I don't think we will." Already in negotiations

? Jay Gunn (@paid2win) Jun. 9 at 11:47 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.