LOS ANGELES (AP) — Andrew Alexander, the CEO and co-owner of famed The Second City improv theater, said he is stepping down after a former performer leveled accusations of racism against the comedy institution.

In a lengthy letter posted on the company's website, Alexander said he "failed to create an anti-racist environment wherein artists of color might thrive. I am so deeply and inexpressibly sorry,"

He vowed Friday that he will be replaced by a person of color.

The originally Chicago- and Toronto-based Second City was an early training ground for "Saturday Night Live" players including Joh...