Bristol-Myers Squibb (BMY) reported a stronger-than-expected 10% increase in first-quarter profit, as strong demand for its melanoma and leukemia drugs helped soften the blow as blood pressure treatment Avapro lost patent protection.

However, the company’s so-called patent cliff is only just beginning. Its massive $7 billion-a-year blood clot preventer Plavix is expected to lose exclusivity next month, putting it in the cross hairs of generic competition.

Yet, Bristol-Myers backed its 2012 earnings forecast in the range of $1.90 to $2 a share, excluding items, which is in line with Wall Street expectations of $1.97.

That’s a reflection of continued investments in boosting its product portfolio, including an experimental blood clot preventer Eliquis that could be approved by late June and help offset some of the softened demand for Avapro.

The New York-based drug maker reported net earnings of $1.1 billion, or 64 cents, compared with a year-earlier $986 million, or 57 cents. The results were ahead of average analyst estimates of 63 cents.

Revenue for the three-month period was up 5% to $5.3 billion, beating the Street’s view of $5.26 billion. Sales in the U.S. were up 6% to $3.5 billion, led by its new melanoma drug Yervoy.

Follow Jennifer Booton on Twitter at @Jbooton