Investors responded favorably Thursday to Eli Lilly and Co.’s surprisingly strong second-quarter revenue, even though its profit fell due to rapid spending on marketing and research.

The Indianapolis-based drugmaker also gave investors a couple hints of growth, even as it nears the October patent expiration of its bestselling drug, the $5 billion-a-year antipsychotic Zyprexa.

Lilly raised its 2011 profit forecast to a range of $4.25 per share to $4.35 per share, excluding special charges. In April, Lilly predicted it would earn $4.15 per share to $4.30 per share for the year.

Lilly saw its stock price rise as much as 1.8 percent Thursday morning after it reported results. Lilly’s stock has risen more than 10 percent this year. The stock traded for $38.77 per share just before midday.

Lilly earned $1.2 billion, or $1.07 per share, in the three months ended June 30, a decline of 11 percent compared with the same quarter a year ago.

The declines were driven mainly by a 16-percent rise in sales and marketing expenses—used to help launch a new diabetes drug Tradjenta, which Lilly is co-marketing with Germany-based Boehringer Ingelheim GmbH. Lilly also suffered increasing costs from the 2010 U.S. health care reform law, which mandated rebates and fees that cost Lilly $110 million in the quarter.

Excluding a $132 million restructuring charge for Lilly’s ongoing layoffs of 5,500 workers, the company would have earned $1.3 billion, or $1.18 per share, which represents a 4-percent decline in profit from the same quarter last year, when all special charges are excluded.

On that basis, analysts were expecting profit of $1.17 per share, according to a survey by Thomson Reuters.

Revenue for the quarter totaled $6.25 billion, up 9 percent from a year earlier. Analysts expected only $6 billion in revenue.

“Slightly better-than-expected revenues, that is the pattern we are seeing,” Tony Butler, an analyst with Barclays Capital in New York, told Bloomberg News.

Lilly achieved double-digit sales growth for seven of its eight best-selling drugs, including 18-percent growth for insulin Humilin, 16-percent for another insulin, Humalog, and 16-percent growth for its anti-depressant Cymbalta.

Cymbalta sales hit $1 billion in the quarter, second only to Zyprexa sales of $1.4 billion.

Sales of Lilly’s cancer drug Gemzar fell 62 percent, to $112.4 million, after generic copies hit U.S. markets in November. Lilly also faces generic competition for Zyprexa when its U.S. and European patents expire in October.

Noting the challenges from generic Gemzar and health care reform, Chief Financial Officer Derica Rice stressed that all other parts of Lilly’s business were performing well.

“We again delivered strong growth in the remainder of our business,” he said.