Akcea Therapeutics (AKCA) - Get Report shares on Monday sank more than 20% after the biopharma said three top executives, including Chief Executive Paula Soteropoulos, would step down.

Akcea went public in July 2017 at $8 a share. The stock on Monday was down 23% at $17.29 on the Nasdaq Stock Market.

Soteropoulos, President Sarah Boyce and Chief Operating Officer Jeff Goldberg are all departing, Akcea said in a statement. The majority-owned affiliate of Ionis Pharmaceuticals (IONS) - Get Report  said it named Damien McDevitt interim CEO.

McDevitt, a board member at Boston-based Akcea, had been chief business officer at Ionis, leading its corporate-development activities.

Akcea develops and commercializes rare-disease drugs, including Tegsedi (inotersen), which treats a condition called hattr amyloidosis, a gene mutation that causes certain types of proteins to clump together and damage organs.

In early August Akcea reported that its first-half loss narrowed to 26 cents a share from $1.33 in the year-earlier period. Shares outstanding rose 4.8% to 22.4 million. Revenue leaped more than five-fold to $190.4 million from $35.4 million.