Amgen’s total revenue shot up 9 percent during the first quarter of this year, the Thousand Oaks-based biotech giant said in an April 24 earnings report.

The biotech company reported revenue of $4 billion, up from $3.7 billion in the first quarter of 2011. Total product sales, which include U.S. and international sales  increased 8 percent, from $3.6 billion in the first quarter of 2011 to $3.9 billion during the same time period this year.

A few key drugs contributed to the company’s increase in sales. Combined sales of Neulasta and Neupogen, which help protect against infection caused by chemotherapy, rose 9 percent to $1.3 billion. Enbrel, a treatment for psoriasis and arthritis, saw its sales go up 7 percent to $938 million.

Adjusted earnings per share were $1.61 for the first quarter of 2012, an increase of about 20 percent compared to $1.34 last year. According to data from Reuters, the average analyst estimate for the biotech company was $1.45 per share as of March.

“We delivered strong sales and earnings during the first quarter, reflecting broad strength across the portfolio,” Kevin Sharer, Amgen’s chairman & CEO, said in the earnings release.  “The pipeline is developing well and the business is in good shape to address the opportunities and challenges ahead.”