Ben Stiller and Christine Taylor Honor Friend Who Died of 'Devastating' ALS: 'We All Were So Shocked By What Happened to Her'

The actor and his wife cohosted an event for the 25th anniversary of Project A.L.S., founded by late friend Jennifer Estess, who died of the disease

Ben Stiller and wife Christine Taylor made a rare public appearance with their 18-year-old son Quinlin Dempsey Thursday for a cause dear to the family.

Stiller, 57, and Taylor, 52, cohosted a gala in celebration of the 25th anniversary of Project ALS., founded by close friend Jennifer Estess, who died of the disease at age 40.

“I think we all were so shocked by what happened to her. And it's such a devastating disease. It's one of those diseases where there is no real cure for it,” Stiller told PEOPLE about Estess, whom he said “was a really good friend of mine in the theater community.”

Her friends were on-hand to celebrate Project ALS’s 25th anniversary, held at Jazz at Lincoln Center, Stiller told PEOPLE.

“All the people who are part of Project ALS go that far back with her,” Stiller told PEOPLE. “Everyone’s here on a personal level.”

ALS — or amyotrophic lateral sclerosis — is a fatal, progressive nervous system disease, affecting nerve cells in the brain and spinal cord, according to the Mayo Clinic.

Often called Lou Gehrig’s disease, after the baseball star who was diagnosed with it in 1939, ALS “often begins with muscle twitching and weakness in an arm or leg, trouble swallowing or slurred speech,” the Mayo Clinic explains. 

Related: Young Father Defying the Odds of His ALS Diagnosis Says the Disease Is 'No Longer Hopeless'

Estess was first diagnosed with the disease in 1997, according to the Project ALS. site, which said that her doctor told her to “max out her credit cards and eat junk food.”

Instead, she founded Project ALS, which has since raised more than $90 million to fund its search for a cure.

Stiller praised Project ALS, telling PEOPLE it’s an “amazingly effective organization.”

“It's hard to deal with because [there’s] not a lot of hope for people, when there isn't actually a cure. But what Project ALS has done is created hope,” Stiller told PEOPLE.

Related: Roberta Flack Has ALS, Making It 'Impossible to Sing'

He added that the foundation has "worked so hard to get money to get funding for the research and they're making real progress. So that's what it's about.”

The cause of the disease is unknown, and 90% of cases occur without any known history or genetic cause, according to the ALS Association. Most people who develop ALS are between the ages of 40 and 70, with an average age of 55 at the time of diagnosis, but there are cases of ALS in people in their twenties and thirties. Men are 20% more likely than women to be diagnosed, although the incidence is more equal as age increases.

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