Athira Pharma, a Bothell-based biopharmaceutical company, announced Thursday that CEO and co-founder Leen Kawas has resigned from the company after an internal investigation found that she had altered images in her doctoral dissertation and “at least four research papers” written while she was at Washington State University.

Kawas had been on leave since June, when Athira said it was reviewing her research conduct. Mark Litton, who was chief operating officer and had assumed day-to-day leadership during the investigation, has been appointed CEO.

Athira said in a regulatory filing that the patent for ATH-1017, the company’s leading development candidate for Alzheimer’s disease, does not cite any of Kawas’ papers with altered images. Kawas received her Ph.D. in molecular pharmacology in 2011 from WSU; the company said the papers with altered images were published between 2011 and 2014.

Concerns about Kawas’ work previously have been raised on PubPeer, an online forum that hosts discussions about scientific papers. Commenters on the forum said some images of lab results looked to be copied between experiments.

WSU said in June it was also conducting its own review, but no additional details have since been made public.

Athira completed an initial public offering in 2020, raising $204 million. Its stock plunged nearly 40% the day Kawas was placed on leave, and it has not recovered since. The stock closed at $9.63 on Thursday but following the announcement was up approximately 5% in after-hours trading.