The company's operating income increased 13 per cent to $1.4bn (€1bn) in the quarter ending 31 March 2007, from $1.2bn in the same quarter last year. The Californian drug maker generated a total of $3.7bn in sales, a 15 per cent increase from $3.2bn in the previous quarter. Product sales totalled $3.6bn, a 14 per cent jump from last year, largely driven by Aranesp, whose sales increased 14 per cent to $1bn in the first quarter, from $893m during the same quarter last year. The drug stimulates red-blood vessel growth (erythropoiesis). The firm said this growth was principally driven by demand. Sales of Epogen (epoetin alfa), Amgen's older anaemia drug, increased only 3 per cent to $625m in the quarter - a growth "partially offset by changes in customer purchasing patterns", the firm said in a statement. "Our key products delivered good sales growth during the quarter," said Kevin Sharer, Amgen's CEO. "We are confident erythropoiesis stimulating agents (ESAs), including Aranesp and Epogen, maintain a favourable benefit profile when used in accordance with label recommendations." Safety concerns Amgen was expected to announce its first quarter figures last week but delayed the release to include results from a late-stage study of Aranesp that provided some comforting evidence of its safety. The product's reputation took a beating in February after two separate studies found an increased risk of death in patients taking it to counteract side effects caused by chemotherapy for head and neck cancer. Amgen has now disclosed new data from a 600-patient Phase III study of the drug which showed there was not a significant difference in the risk of death in patients with small cell lung cancer receiving chemotherapy when compared with placebo. Aranesp suffered another blow in March along with other erythropietic agents on the market after the US Food and Drug Administration (FDA) demanded that labelling be tightened to warn that the class may increase the risk of heart attack, stroke and death in patients with kidney disease The warning label suggested that doctors should use the lowest possible dose of the drug. Aranesp is approved to treat anemia associated with chronic kidney failure and nonmyeloid cancers and is the company's top-selling drug, generating $4.1bn in sales last year. Meanwhile, Amgen's other drugs also generated higher revenues in the first quarter. Sales of rheumatology and psoriasis drug Enbrel (etanercept) increased 11 per cent to $730m - despite a slower growth in the US due to increased competition - while white blood cell boosters Neupogen (fligrastim) and Neulasta (pegfilgrastim) saw combined sales jump 14 per cent to $1bn. Revenues for Sensipar (cinacalcet) - a treatment for hyperparathyroidism in dialysis patients - rose 72 per cent to $105m, while colorectal cancer therapy Vectibix (panitumumab) generated sales of $51m. Meanwhile, costs of sales were up 7 per cent to $592m while R&D spending increased 30 per cent from $655m in the previous quarter to $851m. Earlier this month, Amgen announced its plans to delay construction of its major new manufacturing plant in Cork, Ireland, part of a $1bn expansion programme announced last year. Originally due to become operational in 2009, the manufacturing facility will now be several years behind the original schedule, following a "global assessment" of manufacturing needs.