KENILWORTH, NJ (TheStreet) -- Merck's (MRK) - Get Report new cancer immunotherapy Keytruda posted $83 million in sales during the first quarter, better than expected, although total revenue and drug sales decreased from one year ago.

Keytruda is Merck's checkpoint inhibitor approved last September for advanced melanoma. First quarter sales rose 40% sequentially from $50 million in the fourth quarter. Last week, Merck submitted new data to the U.S. Food and Drug Administration seeking to expand Keytruda's label to cover the treatment of patients with advanced non-small lung cancer patients. Another FDA filing to expand Keytruda use in newly diagnosed melanoma patients will be submitted mid year, the company said.

Bristol-Myers Squibb (BMY) - Get Report reported Tuesday that first-quarter sales of its competing checkpoint inhibitor Opdivo were $40 million, less than the Street expected.

Merck shares were up 5% to $59.74 in pre-market trading.

Overall, total sales in the first quarter were $9.4 million, down 8% year over year but higher than the Street consensus estimate of $9 billion. Merck attributed lower sales in the March quarter to the negative impact of foreign currency exchange and the divestiture of consumer products.

Merck pharmaceutical sales totaled $8.3 billion in the first quarter, a decrease of 2% year over year. Excluding the negative effect of foreign exchange, pharmaceutical sales would have risen 5% in the quarter.

Sales of the diabetes drugs Januvia and Janumet rose 4% year over year to $1.4 billion. On Monday night, Merck announced that an important heart-safety study of Januvia achieved its main goal.

Remicade, Merck's rheumatoid arthritis drug, reported sales of $501 million, down 17% year over year, largely due to the loss of patent protection and the launch of a biosimilar copy of the drug in Europe.

On an adjusted basis, Merck reported first quarter earnings per share of 85 cents, topping the Street consensus of 74 cents per share but down from the year-ago quarter when the company reported adjusted earnings of 88 cents per share.

Including all charges, Merck earned 33 cents per share in the first quarter, down from GAAP earnings of 57 cents per share in the first quarter 2014.

Merck adjusted 2015 adjusted earnings guidance to a range of $3.35 to $3.48 per share versus current consensus estimate of $3.37 per share. The company's 2015 revenue guidance of $38.3 to $39.8 billion brackets current consensus of $39.3 billion.

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