Priestly spoke with ET at the Raising The Bar to End Parkinson’s fundraiser benefiting the Michael J. Fox Foundation at Laurel Point in Studio City, California on Wednesday, and he had nothing but love and well-wishes for Doherty.
"What she did the other day, shaving her head and posting the pictures and everything, that was incredibly brave," the Private Eyes star shared.
"Shannen's a strong kid and a tough fighter and I know that she's gonna come through this fight and she's gonna be OK," he added.
The 46-year-old actor also praised the way Doherty has used her illness
and her public platform to "shine a light and help other people."
Actress Tiffani Thiessen, who replaced Doherty on Beverly Hills, 90210 when she left after the fourth season, was also in attendance at the fundraiser. Thiessen told ET, "I wish her all the best, of course."