What happened

Having dropped from the lofty heights it reached only a few short months ago, Alector (ALEC -5.13%) stock was having another bad day on Wednesday. The biotech's shares were down nearly 17% in mid-afternoon trading following some news from the C-suite.

So what

After market hours on Tuesday, Alector announced the departure of two high-level executives. It said that chief operating officer Shehnaaz Suliman and chief medical officer Robert Paul will step down following a "transition period," and should continue to serve as advisors to the company until the end of this year.

Roadside exit sign.

Image source: Getty Images.

Suliman has ambitions to head a company. She said in a statement she is "looking forward to pursuing a future chief executive leadership role with a focus on advancing groundbreaking scientific insights into viable treatments" that can improve the lives of patients.

The company didn't provide any reasons for Paul's departure. His interim replacement will be the company's current senior vice president of clinical sciences, Sam Jackson. No replacement for Suliman has yet been named.

Alector is a busy company. The clinical-stage biotech currently has four immuno-neurology treatments in development. In July, Alector signed a splashy co-development deal with big pharmaceutical company GlaxoSmithKline that could be worth up to $2.2 billion.

Now what

Alector still feels like a company well on the move, which is why the latest news was so disquieting. It's always a concern when a business that seems destined for success is hit by more than one executive departure in a short span of time. Hopefully for Alector and its investors, this is not indicative of deep problems with the company's corporate culture or morale.