• The maker of Marlboro cigarettes said it plans to make further market purchases of Vectura at 165 pence ($2.27) per share.
• Philip Morris International said on Monday that it had entered a tender period with Vectura shareholders following the unanimous recommendation of the asthma inhaler firm's board.
• Campaign groups have sharply criticized tobacco giants for advocating themselves as part of the transition to a smoke-free world while also continuing to sell and promote cigarettes globally.

LONDON — Tobacco group Philip Morris International on Wednesday said it had bought 22.61% of U.K.-based respiratory drug developer Vectura in a market purchase.

The maker of Marlboro cigarettes said it plans to make further market purchases of Vectura at 165 pence ($2.27) per share.

Philip Morris International said Monday that it had entered a tender period with Vectura shareholders following the unanimous recommendation of the asthma inhaler firm's board.

Vectura's board cited a superior cash price offered to Vectura shareholders by Philip Morris International and said the benefit to stakeholders from the cigarette maker's significant financial resources, commitment to enhanced research and development, and autonomy were factors in their decision.

"PMI's acquisition of Vectura is part of our long-term strategy to transform PMI by investing in scientific excellence and leveraging its capabilities and expertise," PMI CEO Jacek Olczak said in a statement published Monday.

"Our investment will accelerate the development and delivery of inhaled therapeutics to address many of today's unmet medical needs. We look forward to working with Vectura's great people as we embark on the next stage of our transformation."

Earlier this month, an open letter signed by 35 health charities and public health experts urged Vectura board members to reject a takeover bid by Philip Morris International. Signatories of the letter, led by Asthma UK and the British Lung Foundation, said a deal "could significantly hamper Vectura's research and product development capabilities."

Separately, the British Thoracic Society, an anti-smoking charity, called for the deal to be prevented, describing the inappropriateness of the arrangement as an "unresolvable ethical conflict."

Philip Morris International has repeatedly touted its "smoke free" ambitions, although the vast majority of its revenues still derives from cigarettes. Last month, PMI's Olczak reportedly said that the company planned to stop selling cigarettes in the U.K. within 10 years.

Philip Morris International has issued similar statements in the past only for very little to change. The firm's former CEO Andre Calantzopoulos said in 2016 that he hoped the company would stop selling cigarettes entirely.

Campaign groups have condemned tobacco giants, which have a long history of denying the health risks of smoking, for advocating themselves as part of the transition to a smoke-free world while also continuing to sell and promote cigarettes globally.

The World Health Organization describes the tobacco epidemic as "one of the biggest public health threats the world has ever faced." The United Nations health agency says smoking, including second-hand, kills more than 8 million people per year.