Welcome to the GSK Patient Assistance Program (GSK PAP) Portal for providers and advocates. If you have any questions, please contact the program at 1-866-728-4368 Monday through Friday 8 AM – 8 PM ET. ... GSK Patient Assistance Program. Address: PO Box 220590 Charlotte, NC 28222-0590: Phone: (866) 728-4368: Fax: (855) 474-3063: Hours:.