How do tezacaftor and ivacaftor in Symkevi act on the CFTR protein?

In Symkevi, tezacaftor binds CFTR’s MSD-1 and improves processing and trafficking to increase cell-surface CFTR, while ivacaftor increases opening of CFTR channels already at the cell surface, enhancing chloride transport in vitro; the exact mechanisms for F508del-CFTR are unknown.