Asthmatx is now an indirect, wholly-owned subsidiary of Boston Scientific.

Under the terms of the agreement, Boston Scientific purchased all outstanding Asthmatx shares for a total of $193.5m. Additional payments of up to $250m are contingent upon achievement of specified revenue-based criteria through 2019.

Asthmatx designs, manufactures and markets the Alair Bronchial Thermoplasty System, a catheter-based procedure for the treatment of severe persistent asthma in the 6 to 8 million patients 18 years and older worldwide whose asthma is not well controlled with drugs (inhaled medications).

The Alair System has received US Food and Drug Administration (FDA) approval in April, and is the first device-based asthma treatment approved by the FDA.

The clinical data indicate that bronchial thermoplasty is safe and effective in the management of severe asthma and leads to significantly fewer severe asthma exacerbations, an 84% reduction in emergency room visits and a trend toward decreased hospitalisations.