When it comes to Bristol-Myers Squibb, the rumors are true. Activist investor Starboard Value has indeed taken a stake in the merger-bound pharma—and it’s looking to meddle further.

Starboard has its hands on 1 million shares of Bristol-Myers’ stock, most of which it grabbed on Jan. 31. And the hedge fund has already filed with regulators for permission to pick up more.

Starboard's current stake is just a tiny portion of the 1.63 billion shares Bristol-Myers has outstanding, but the fund isn’t stopping there. It’s also nominated five new board members—its CEO, Jeffrey Smith, along with John Leonard, Steven Shulman, James Tyree and Janet Vergis—for election to BMS’ slate of directors, the New Jersey drugmaker said in a regulatory filing on Wednesday.

And Starboard has engaged directly since. Bristol-Myers executives "subsequently met with Starboard Value on multiple occasions," the filing states.

While Starboard's intentions are as yet unclear, it seems likely the agitator’s plans have something to do with Bristol-Myers’ proposed $74 billion Celgene buyout. Industry watchers have speculated that Starboard could pressure Bristol-Myers to put itself up for sale instead of going through with the merger. Then again, analysts have pointed to a lack of buyers willing and able to swallow such a large deal.

Still, Starboard intervening could please investors who are less than enthused about the Celgene pact. That reportedly includes Dodge & Cox, BMS’ fifth-largest shareholder, CNBC notes, citing a Dow Jones report based on anonymous sources. And Starboard is in search of others: It recently hired a proxy solicitor to survey the level of support for the buy, according to Reuters.

Bristol-Myers, though, seems confident the tie-up will close as planned. It filed a merger update on Wednesday to reiterate an April 12 date for its special meeting to vote on the Celgene buy, adding that "the transaction remains on track to close in the third quarter of 2019."

And analysts have tended to agree, at least so far. BMO's team, for their part, believe the "probability of a third-party buyer for Bristol-Myers Squibb" before the April vote is "very low," according to a note seen by CNBC, adding that "we do not believe a potential activist can change that."

Credit Suisse analysts also wrote this month that "we would be surprised if activists are successful in pushing for a larger change, such as trying to get Bristol to sell itself." CS' Vamil Divan, M.D., said he and his colleagues continue to expect the deal to close.

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