Source: Gilead Sciences.

Gilead Sciences' (GILD 0.91%) long-standing CEO, John Martin, has handed over the reins to his longtime ally John Milligan, and that's raised questions over whether Milligan could kick off his era at the helm by making a big M&A splash. Although there's no telling what Milligan may do this year, his comments during the company's recent fourth-quarter earnings conference call indicates deal-making is a strong possibility.

Right off the bat
"I will continue to work hard to help Gilead's business grow beyond antivirals and into new therapeutic areas for the betterment of patients," Milligan said.

Milligan's comments, which were made when Martin introduced him at the start of the company's conference call, show he's committed right out of the gate to growing the company's pipeline beyond its core HIV and hepatitis C drugs.

Last year, sales of antiviral therapies used to treat those indications accounted for a whopping $30.2 billion of the company's $32.1 billion in revenue, and thus, antivirals are going to remain a key driver of the company's sales for a long time. However, expanding into new markets and reducing the company's reliance on those drugs is critical to the company's future growth, because emerging threats from ViiV Healthcare in HIV and from AbbVie (ABBV 1.06%) and Johnson & Johnson (JNJ 1.49%) in HCV could mean stiff headwinds are up ahead.

Picking a direction
When Milligan was asked about Gilead Sciences' plans in oncology, Milligan suggested the company is OK with doubling down on the indication despite lackluster results so far. "It's pretty clear we have to do additional partnerships or find other avenues to broaden the revenue stream there for the future," he said.

Sales of the company's first cancer drug, Zydelig, have been slow to materialize, and at $132 million last year, sales remain a far cry south of the billion dollar-plus run-rate of AbbVie's Imbruvica, a drug that launched around the same time and that competes against Zydelg in chronic lymphoblastic leukemia.

Gilead Sciences is studying Zydelig in hope of expanding its use, and it's working on other oncology therapies, too, including promising kinase inhibitors, but a deal may be necessary if the company really wants to be a big player in this huge and growing market.

Accelerating the timeline
Milligan knows the the company has a bit of a problem on its hands. Gilead Sciences' rapid sales and profit growth is slowing as the market for hepatitis C therapy matures, and as a result, moving the needle isn't going to be easy now that sales are above $30 billion and competitors are vying for market share.

This year, the company thinks sales will slip to between $30 billion and $31 billion, and while Gilead Sciences' management is famous for sandbagging results to rein in analyst expectations, it's likely that its track record of double-digit top-line sales growth ended in 2015.

Given investors reward growth and punish stagnation, figuring out a way to spark sales has got to be on Milligan's radar. That's why Milligan had this to say:

"We're very interested in acquiring assets through partnerships or potentially acquisition that could help us grow in those areas. And with the tripling of our revenue over the last few years, the need to do so sooner rather than later is heightened."

Fool-worthy bottom line
Gilead Sciences' success is remarkable, but it also sets the bar high for Milligan, who will need to demonstrate a long-haul ability to out-compete and out-maneuver competitors if he wants to surpass Martin's achievements. Doing so will probably require Martin to orchestrate some savvy and transformative deal-making, but he's got plenty of financial flexibility at his fingertips. Gilead Sciences' cash war chest totaled an envy-inspiring $26.2 billion in December.