CAMBRIDGE, U.K.: AstraZeneca's experimental drug tozorakimab has shown promising results in late-stage trials, reducing flare-ups in patients with chronic obstructive pulmonary disease and boosting investor optimism.

The drug met its main goal in two clinical studies, lowering the annualised rate of moderate-to-severe COPD flare-ups compared with a placebo, the company said.

Shares in AstraZeneca, Britain's most valuable listed company, rose as much as 3.8 percent following the announcement and were up 3.2 percent by 0945 GMT, making it one of the top gainers on the FTSE-100 index. Jefferies analysts described the outcome as "a positive surprise".

Tozorakimab delivered a "highly clinically meaningful" reduction in flare-ups in the primary trial group of former smokers, as well as across the broader study population, which included both current and former smokers with varying levels of lung damage and differing counts of a type of white blood cell.

COPD is a long-term condition that restricts airflow and causes breathing difficulties. While smoking is a major risk factor, exposure to fumes, chemicals and dust in workplaces can also contribute to the disease. It is the fourth-leading cause of death worldwide, according to the World Health Organization.

AstraZeneca said the drug works by reducing inflammation and interrupting the cycle of mucus dysfunction that can worsen COPD symptoms.

Tozorakimab belongs to a class of treatments known as monoclonal antibodies, which replicate the body's immune response. The therapy targets interleukin-33, a protein involved in inflammation.

Previous attempts by rival drugmakers, including treatments from Sanofi-Regeneron and Roche, have produced mixed or unsuccessful results in this area.

AstraZeneca has projected peak annual sales for tozorakimab of between US$3 billion and $5 billion. The company is counting on a pipeline of more than 20 expected drug launches, alongside continued demand for its cancer treatments, to help it reach a target of $80 billion in annual sales by 2030.

JPMorgan analysts said stronger-than-expected data from the trials could push forecasts for the drug toward the upper end of AstraZeneca's projections.

The company said detailed results from the studies will be presented at an upcoming medical conference.

AstraZeneca is also continuing to evaluate tozorakimab in additional trials exploring different dosing levels and treatment regimens. Bank of America analysts noted that the company may not need to wait for higher-dose data before seeking regulatory approval.