Merck & Co. posted higher-than-expected second-quarter results on Tuesday on strong growth of its blockbuster cancer immunotherapy Keytruda, the world's best-selling prescription medicine.

New Jersey-based Merck slightly raised its full-year sales projections, following other big pharmaceutical companies like Roche, Johnson & Johnson and Bristol Myers Squibb, which lifted their forecasts when they reported earnings earlier this month.

Merck posted a profit of $5.5 billion, or $2.14 per share, for the quarter, compared with a loss of $6 billion, or $2.35 a share, a year earlier, when it took a large acquisition-related charge.

Excluding one-time items, Merck said it earned $2.28 per share. Analysts, on average, expected $2.15 a share, according to LSEG data.

Sales in the quarter were $16.1 billion, up 7% from last year and above analysts' expectations of $15.8 billion.

Keytruda has been Merck's most important revenue driver for years with annual sales expected to rise well above $30 billion before the drug loses patent protection toward the end of the decade.

Sales of Keytruda, which is approved to treat many types of cancer, hit $7.3 billion for the quarter, up 16% from a year ago. Analysts had expected sales of around $7.1 billion.

Merck said it now expects full-year sales of $63.4 to $64.4 billion, up from its prior view of $63.1 to $64.3 billion. Analysts have forecast 2024 sales of $64.3 billion.

But the company cut its full-year earnings forecast mainly due to one-time charges from its acquisition of eye-focused drug developer EyeBio.

Merck now expects 2024 earnings of $7.94 to $8.04 per share, down from its earlier forecast of $8.53 to $8.65. Analysts had previously been looking for 2024 earnings of $8.15 a share.

The company's shares, which closed at $127.78 on Monday, are up more than 17% this year.