Research and development costs ate into fourth-quarter profits at Amgen Inc., but the biotech giant still beat analysts’ estimates due to increased sales of its bone and arthritis drugs.

The Thousand Oaks company reported net income of $788 million ($1.01 a share), compared with $934 million ($1.08) in the same period a year earlier. Revenue rose 11 percent to $4.42 billion.

Excluding certain items, the company reported earnings of $1.40 a share, which topped analysts’ estimates by a penny, according to Bloomberg News. Revenue also topped estimates of $4.37 billion.

Immune disorder drug Enbrel saw the best gains, with sales up 23 percent to $1.16 billion. Sales of Aranesp, its popular anemia drug, were down 9 percent to $489 million due to marketing changes, which the company was forced to make after it pleaded guilty to off-label marketing tactics of the drug.

The rise in R&D expenses are due to the company’s focus on a broad pipeline of development-stage drugs, said Chief Executive Robert Bradway.

“We enter 2013 with good momentum, a broad late-stage pipeline and a continued focus on building our business internationally,” he said in a statement.

The company said one of its most promising pipeline drugs is AMG 145, which will be a competitor to Pfizer Inc.’s cholesterol-lowering drug Lipitor.

However, the company also has had some notable failures. Earlier this month, it announced the results of a stage III clinical trial that failed to demonstrate its anemia drug Aranesp lengthened the life of cancer patients with anemia.

Shares closed down 22 cents, or less than 1 percent, to $83.07 on the Nasdaq.