Speculation on what company will make a bid for beleaguered Bristol-Myers Squibb (BMS) has ramped up since billionaire activist investor Carl Icahn acquired an undisclosed number of shares based on takeover rumors.

Writing in the Motley Fool, analyst Todd Campbell said it’s likely that Icahn will begin "advocating for big changes" at BMS, which could include pressuring the company into making a sale. The next investor’s meeting is set for May and the company has already added three new members to its board of directors based on the urging of another activist investor group, Jana Partners, which has acquired about 1 percent of the company’s stock.

In his column, Campbell lays out five companies that could be possible contenders to snap up BMS and its immuno-oncology pipeline helmed by Opdivo. Some of the names Campbell mentions, including Gilead Sciences (GILD), Roche (RHHBY) and Pfizer (PFE), have been mentioned as possible contenders before. But, he also brings in potential new bidders Amgen (AMGN) and Sanofi (SNY). Each of these companies has the capital to acquire BMS, which could fetch more than $100 billion if it’s bought outright, but for Campbell, a move to acquire BMS by Sanofi "makes the most sense."

1. Sanofi

Although Sanofi (SNY) isn’t much larger than BMS, Campbell noted the company has been aggressive in M&A activity to "boost its growth and sidestep the risk of generic competition to its Lantus, a best-selling diabetes drug." Sanofi has been outbid before in the M&A field, particularly when it lost acquisition of Medivation (MDVN) to Pfizer. Campbell said that was in part due to Sanofi’s unwillingness to pay top-dollar for that company, which could end up becoming a hindrance for any acquisition of BMS.

2. Pfizer

Although Pfizer (PFE) certainly has the financial means to acquire BMS, Campbell said that company has a PD-1 inhibitor awaiting approval from the U.S. Food and Drug Administration in Merkel cell carcinoma and is exploring its use in other cancers. For that, Campbell said Pfizer might not be as interested in pulling the trigger on this deal. That also supports the idea raised by including Deutsche Bank’s Gregg Gilbert and Esther Rajavel, who suggested Pfizer is not a serious candidate for a potential acquisition because of costs and the need for "a more diverse set of value drivers."

3. Amgen

Amgen (AMGN) could be a potential suitor for BMS as that company looks to offset revenue challenges to its top drugs Enbrel, Neupogen and Neulesta, which are all facing competition due to the loss of patents. Campbell said the immuno-oncology drugs in BMS’ pipeline would complement Amgen’s cancer drugs and not be a threat to their existing lines.

4. Gilead Sciences

Gilead (GILD) has been under pressure to make an acquisition to bolster lagging sales in its pipeline. The company’s vaunted hepatitis pipeline is losing revenue in part due to how effective the drug is, but also due to increased competition. Campbell said Gilead needs to "make a splash to reinvigorate growth," but in the same breath said the company has been unwilling to make a big acquisition, despite having $30 billion in cash and management’s push to increase the company’s oncology presence.

5. Roche

Another pharma giant with the resources to make a move on BMS, Campbell said that company is likely to continue to focus on developing its own anti-PD-1 drug, Tecentriq, which won FDA approval last year. Roche (RHHBY) is "knee-deep" in studies that would expand the use of Tecentriq beyond the approved lung cancer therapies.

Two companies that has been mentioned before as a possible contender for BMS, but not by Campbell, are Novartis AG (NVS) and Johnson & Johnson (JNJ).

Regardless of whichever company makes a move, if at all, any bidder will be paying a high price to acquire BMS. Shares of BMS are up slightly in premarket trading this morning at $55.65.