Drugmaker Merck reported a better-than-expected first-quarter profit on Tuesday, helped by a more than 150 percent rise in sales of cancer drug Keytruda.
Merck is increasingly reliant on the blockbuster medicine, which is positioned to become the leading player in a new generation of oncology treatments and rival Bristol-Myers Squibb's Opdivo.
Both drugs harness the body's immune system to recognize and fight cancer cells, but last month's survival data from trials of the treatments gave Keytruda an edge over Opdivo, according to industry experts.
Keytruda raked in sales of $1.46 billion in the quarter, ahead of $1.40 billion estimated by analysts, according to Thomson Reuters.
Revenue from the drug accounted for nearly 15 percent of Merck's total sales, helped by its expanded approval to treat various forms of cancer.
Sales of Bristol-Myers Squibb's Opdivo surged 34 percent to $1.51 billion in the latest quarter.
Merck raised its full-year forecast for adjusted earnings to between $4.16 and $4.28 per share from between $4.08 and $4.23 per share estimated previously.
Net income fell 52.5 percent to $736 million, or 27 cents per share, hurt by a $1.4 billion charge related to a collaboration with Eisai Co Ltd, the company said.
Excluding items, Merck earned $1.05 per share, ahead of analysts' estimates of $1 per share .
Revenue rose 6.4 percent to $10.04 billion, but missed estimates of $10.11 billion.
Merck's shares rose 1.1 percent to $59.50 before the bell.