Cancer immunotherapy may reshape brain’s barrier to metastasis

13 MAY 2026

Drugs that enhance the body’s immune response against cancer may also be altering one of its most tightly guarded boundaries: the blood-brain barrier (BBB).
A recent study published by Yuval Shaked at the Technion-Israel Institute of Technology and his team, in Cancer Discovery, finds that PD-1 inhibitors, a widely used class of cancer immunotherapy, can prompt immune cells to produce a protein that makes the barrier more permeable.
This could potentially change how cancer and its treatments affect the brain.
Many conventional anti-cancer drugs cannot cross the BBB, which is a tightly packed lining of cells that controls what passes from the bloodstream into brain tissue, limiting their effectiveness against brain tumours.
So the brain was long thought to be largely insulated from the immune system, but growing evidence shows it can mount meaningful immune responses.
In this context, immunotherapy works by activating circulating immune cells that can cross the BBB and target tumour cells within the brain.
A type of immunotherapy called immune checkpoint inhibitors (ICIs) block signals that prevent immune cells from attacking tumours, allowing the body’s natural defences to respond more strongly.
While ICIs have been shown to reduce tumour burden within the brain, responses among patients with brain metastases vary and the reasons remain unclear.