Bank of America Merrill Lynch on Tuesday named pharmaceutical giant Merck and Co.  (MRK) - Get Merck & Co., Inc. (MRK) Report as its No. 1 top pick in the U.S. pharmaceutical space thanks to what it sees as strong potential upside in sales of one of its key cancer-treatment drugs.

On Friday, Merck reported that one of its key cancer drugs used to treat malignant tumors in lung and renal cancer surpassed $2 billion in its most recent quarter, exceeding analysts' forecasts. The better-than-anticipated numbers pushed Merck shares higher last week, with the stock ending the week up close to 5%.

"The fourth-quarter and full-year results further bolster our confidence in Merck's innovation-based strategy in which our key pillars - oncology, vaccines, animal health, and select hospital and specialty care products - are expected to drive sustainable growth over the long-term," Merck CEO Kenneth Frazier said in Friday's earnings release. "We enter 2019 with good momentum."

Strong Sales Momentum

That momentum is likely to continue, according to Bank of America Merrill Lynch analyst Jason Gerberry.

"Merck looks well positioned to become the preferred PD1 agent in most major tumor markets, and we estimate upcoming data readouts in lung and renal cancer have the potential to add $4 billion in peak sales or 5-10% upside," Gerberry wrote in a note to clients.

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Keytruda blocks a specific kind of protein called programmed death receptor 1, or PD-1, on immune cells, which helps keep the body's cells from attacking other healthy cells. Sales of the drug surged 66% year over year in the fourth quarter, and accounted for nearly 20% of total sales.

Looking into 2019, Merck said it sees non-GAAP earnings of between $4.57 and $4.72 a share on global sales of between $43.2 billion and $44.7 billion, both topping estimates compiled by Refinitiv.

Upbeat on Pharma, Healthcare

Anish Chopra, managing director and portfolio manager with Toronto-based Portfolio Management Corp., said he is partial to U.S. healthcare and related stocks amid the current economic and market uncertainty. 

"Our U.S. healthcare stocks held up well this past fall, especially in December," Chopra said. "They're not going to be shining stars in 'rebound times' like last month, but they're a really good defensive asset in tougher times like we saw in the later part of last year."