How does ledipasvir + sofosbuvir affect tenofovir exposure, particularly with ritonavir or cobicistat?

Ledipasvir + sofosbuvir increases tenofovir exposure, especially with HIV regimens containing tenofovir disoproxil fumarate and ritonavir or cobicistat; safety of this combination has not been established, and specified boosted regimens require monitoring for tenofovir-associated adverse reactions.