AstraZeneca, the British pharmaceutical giant, announced on Thursday a halving of net profits in the first quarter, hit by generic competition following the loss of exclusivity for key drugs. Profit after tax slumped to $504 million (365 million euros) in the three months to the end of March compared with $1.011 billion during the first quarter of 2013, AstraZeneca said in an earnings statement. The company, which is looking to push ahead with new treatments for cancer and respiratory disease, made no comment regarding weekend reports that US pharmaceutical giant Pfizer is considering a $100 billion takeover of AstraZeneca. On Thursday, the British group added that its pre-tax profits more than halved to £638 million in the first quarter. Revenues edged up 0.5 percent to $6.416 billion but by 3.0 percent at constant exchange rates. AstraZeneca added that the impact of losses from major patent expiries, including for anti-cholesterol drug Crestor, totalled almost $150 million in the first quarter. In a bid to turn around the firm's fortunes, AstraZeneca is investing in its "rapidly progressing pipeline" of cancer drugs, chief executive Pascal Soriot said in Thursday's statement. It is also shedding around 5,000 jobs under a three-year cost-cutting programme due to end in 2016. The global pharmaceutical sector has undergone a huge shake-up this week after drugmakers Novartis and GlaxoSmithKline unveiled multi-billion-dollar deals also involving US group Eli Lilly. The string of takeovers and ventures by the three giant healthcare groups will see Novartis sharpen its focus on the high-grossing cancer sector, GSK boost its share in vaccines and Eli Lilly strengthen its animal health unit. The mega deals come as the global pharmaceutical industry is quickly shifting to deal with a raft of challenges, in particular patents expiring on key brands and deep cuts to government healthcare spending worldwide.