May 21 (Reuters) - GSK's experimental drug met its primary goal of reducing asthma attacks in a late-stage trial, marking a bright spot for a treatment that the British drugmaker expects to make peak annual sales of 3 billion pounds ($3.81 billion).

The drug, called depemokimab, showed "significant and meaningful reductions" in asthma attacks for patients with eosinophilic asthma, GSK said on Tuesday.

This form of asthma is characterised by high levels of eosinophils, which is a type of white blood cell.

The results come as GSK sharpens focus on its respiratory health portfolio, which is currently thriving on the back of back of a strong launch of its respiratory syncytial virus (RSV) vaccine Arexvy.

The company also bought asthma drug maker Aiolos Bio in a deal worth up to $1.4 billion earlier this year.

Depemokimab is one of the 12 major launches that GSK is gearing up for starting in 2025, having said it has the potential to be a major growth driver by the end of the decade.

The drug has the potential to be the first approved ultra-long-acting biologic with a six-month dosing schedule for patients with severe asthma, GSK said.

"Discovered by our scientists in Stevenage, Depemokimab builds on our deep heritage and leadership in respiratory medicine and has the potential to make a real difference to the millions of people whose lives are affected every day by severe asthma," said Tony Wood, GSK's chief scientific officer. ($1 = 0.7867 pounds) (Reporting by Eva Mathews in Bengaluru; Editing by Nivedita Bhattacharjee and Varun H K)