Port Washington-based drugmaker Aceto Corp. said Wednesday it had replaced its CEO, effective immediately.

Salvatore Guccione, 53, CEO since 2013 and company president since 2011, resigned from those positions and gave up his seat on the board of directors.

Board member William C. Kennally III was appointed CEO and president, effective Monday. He is a retired executive who worked for 37 years at pharmaceutical giant Pfizer.

Kennally, 60, has served on the Aceto board for about a year.

Aceto board chairman Albert Eilender, in a statement, recognized Guccione’s leadership in transforming Aceto from a chemicals seller to a manufacturer of generic drugs.

Guccione could not be reached for comment Wednesday night, and a company spokeswoman didn’t immediately respond to a voicemail message seeking comment.

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In a securities filing on Wednesday, Aceto said, “there were no disagreements between the company and Mr. Guccione on any matter relating to the company’s operations, policies or practices.

Guccione will receive nearly $2 million in severance and job performance awards, according to the filing. His 2016 compensation was $2.5 million.

Guccione’s sudden resignation comes after Aceto’s stock fell 29 percent on Aug. 25 after it reported a profit of $2 million in the April-June period, down 71 percent from a year earlier.

Guccione blamed the decline on competition among manufacturers of generic drugs. He predicted drug prices would continue to fall in the company’s 2018 fiscal year, which began July 1, but also said new drugs would be introduced.

Kennally, the new CEO, said Aceto wouldn’t retreat from its strategy to be a drug manufacturer.

“Aceto has successfully laid the foundation for its transition to a human health company,” he said in a statement on Wednesday. “I expect to build on that success while exploring and introducing new capabilities to strengthen the company’s competitive position in the generics drug industry.”

Aceto’s announcement came after the stock market closed.

In after-hours trading, the company’s shares were $11.11, unchanged from Wednesday’s close, which was up 6 cents, or less than 1 percent, from Tuesday on the NASDAQ Stock Market. The stock is down 43 percent in the past 12 months.