It took four tries over four years, but Perrigo has finally gotten over the finish line with its generic of Teva’s tricky-to-make ProAir HFA inhaler for chronic obstructive pulmonary disease and asthma.

Perrigo and its manufacturing partner Catalent touted the news jointly today, saying they are releasing a limited supply now of the generic albuterol sulfate inhalation aerosol and ramping up production for a steady supply by the fourth quarter of 2020.

The inhaler is approved for patients four years of age and older for the treatment or prevention of bronchospasm with reversible obstructive airway disease and for the prevention of exercise-induced bronchospasm.

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"This is a significant technical achievement for both parties, as it is the first generic metered-dose inhaler to be approved by the FDA in over 20 years," Jonathan Arnold, Catalent president of oral and specialty delivery, said in a statement.

The product is being produced at Catalent’s North Carolina inhaler plant.

Perrigo said drug tracker IQVIA measured ProAir HFA gross sales for the previous 12 months at $1.4 billion, although Teva reported (PDF) 2019 sales of only $274 million, down 23%. Teva has two other ProAir products including one with a mobile app, the ProAir Digihaler, approved a year ago.

Teva settled a patent challenge by Perrigo over ProAir HFA in 2014, allowing it to launch its generic. But it wasn’t that simple. Perrigo received three complete response letters, one each in 2016, 2017 and 2018, during its journey to get its product up to FDA expectations. The last rejection forced Perrigo to restate earnings.

Teva in 2017 also settled a patent fight with Lupin for the inhaler product, but the Indian company has yet to get its effort to the FDA.