(Reuters) - AstraZeneca Plc beat first-quarter sales and earnings expectations on Friday as the British drugmaker benefited from a push into cancer drugs and emerging markets including China.

FILE PHOTO: The company logo for pharmaceutical company AstraZeneca is displayed on a screen on the floor at the New York Stock Exchange (NYSE) in New York, U.S., April 8, 2019. REUTERS/Brendan McDermid

Newer treatments such as lung cancer drug Tagrisso, now the company’s top selling medicine, have helped the drugmaker’s return to growth after years of crumbling sales due to patent losses on older drugs.

Sales in China have shown explosive growth, more than doubling since 2012, but AstraZeneca executives on Friday said that may not be sustained.

“The enormous growth you currently see in China, 28 percent, probably is not sustainable, but we feel very bullish that the growth will continue to be at a pace of between 15 percent and 20 percent,” Ruud Dobber, executive vice president, BioPharma, told Reuters.

Shares of the company were down 0.2 percent at 5,878 pence at 1031 GMT.

The turnaround in AstraZeneca’s fortunes has been powered by a push into cancer treatments led by Chief Executive Pascal Soriot, who saw off a 2014 takeover bid from Pfizer in part by promising annual sales of $45 billion by 2023.

In the first quarter, sales from its oncology unit rose 59 percent to $1.89 billion, accounting for 35 percent of total product sales.

The company has moved deeper into cancer therapy market through wide-ranging deals, including those for immunotherapy and targeted therapy. Last month, it agreed a multi-billion dollar oncology deal with Japan’s Daiichi Sankyo Co Ltd.

Interactive graphic on AZN's top 10 drugs by sales - tmsnrt.rs/2W5XIRX

“We’re reaching that point where after years of having to keep faith, we have actually got something tangible to believe in,” Hargreaves Lansdown analyst Nicholas Hyett said.

AstraZeneca also backed its annual sales and earnings forecast and said it has extensively prepared for UK’s anticipated exit from the European Union, even in the event of a no-deal exit.

The company has already spent more than 40 million pounds ($52 million) on Brexit preparations, including stockpiling six weeks’ worth of drugs in the UK and four weeks in continental Europe to guard against shortages.

AstraZeneca said product sales rose 14 percent at constant currency to $5.47 billion in the quarter, led by its lung cancer drug Tagrisso and respiratory treatment Pulmicort.

Interactive graphic on AZN's quarterly oncology sales - tmsnrt.rs/2W9tbCD

China sales increased by 28 percent to $1.24 billion in the quarter, accounting for nearly a quarter of overall product sales.

Core earnings came in at 89 cents per share in the quarter. Analysts on average were expecting core earnings of 85 cents per share and product sales of $5.29 billion, according to a company provided consensus of 19 analysts.