British drugmaker GlaxoSmithKline on Wednesday said its net profit sank in the first quarter on higher exceptional costs compared with a year earlier, but that underlying earnings jumped.

Profit after tax dropped 23 percent to £1.08 billion ($1.35 billion), GSK said in an earnings statement.

However core operating profit excluding exceptional items rallied 27 percent to £2.4 billion, while revenues swelled 10 percent to £7.4 billion.

GSK chief executive Emma Walmsley said the quarter saw further progress in final trials of new drugs.

"We have made a strong start to 2024, with another quarter of excellent performance and continued pipeline progress," she said in the statement.

"We have strengthened prospects for growth in all of our key therapeutic areas this quarter: infectious diseases, HIV, respiratory/immunology and oncology."

The group's share price rose 2.3 percent in early afternoon trading on London's top-tier FTSE 100 index, lifted by the upgraded full-year outlook.

"GSK has started 2024 in rude health. Strong growth in vaccine and speciality medicines drove a double digit rise in group sales," said Derren Nathan, head of equity research at Hargreaves Lansdown.

The first quarter saw GSK agree to buy Aiolos Bio for up to $1.4 billion, with a focus on an asthma medication still at the testing stage.