AstraZeneca plc (AZN) - Get Report posted stronger-than-expected first quarter earnings and held on to its full-year guidance despite a slowing in sales for some of its key treatments in the face of generic competition.

Core earnings for the first three months of the year rose $0.99 per share, the company said, well ahead of the $0.85 forecast compiled by FactSet and up from $0.92 in the first quarter of 2016. Total revenues for the period were marked at $5.4 billion, largely in-line with the FactSet forecast but down 11.5% from the first quarter of last year.

"Our good start to the year supported our guidance for 2017. Notably, Emerging Markets became our largest region, representing 32% of sales. The pipeline continued to deliver in what we expect will be a pivotal year for AstraZeneca as we announced important developments, in particular in Oncology," said CEO Pascal Soriot. "In addition to the availability of positive data for Lynparza in ovarian and breast cancer, we also received full approvals in the US and Europe for Tagrisso in lung cancer and launched this important medicine in record time in China. While we were disappointed to receive the Complete Response Letter for ZS-9, we remain confident in this treatment for hyperkalaemia."

However, AstraZeneca's key cholesterol treatment, which is facing stiff competition from generic rivals, saw sales fall 45% from the same period last year to $631 million while sales of Onglyza, its oral diabetes drug, fell 27% to $154 million.

Nonetheless, AstraZeneca held to its previous gudiance of a "low to mid single-digit percentage decline in revenues" and a "low to mid teens percentage decline in core EPS for the full year.

"Variations in performance between quarters can be expected to continue, with year-on-year comparisons expected to ease in the second half of FY 2017, when the impact of the entry of Crestor generic medicines in the US will annualise," the company said..

AstraZeneca shares slipped 1.4% in early London trading to change hands at 4,618 pence each, trimming the year-to-date advance to around 4.2% this year, a gain that is largely in-line with the Stoxx Europe TMI Pharmaceuticals index.