ideasIdea
CD8 PET to stop or switch immunotherapy early
Scan for T cells inside the tumour a few weeks after starting immunotherapy. If they have not arrived, change course.
89Zr-crefmirlimab (CD8 minibody) and 18F-AraG image T-cell infiltration and activation. Early increase correlates with response in phase 2 studies.
Confidence
30%–50%likelyOnCo editors (initial estimate), 2026-09-07 · Correlative data are encouraging; prospective switch trials are hard to run.
Hypothesis
Absence of CD8 PET increase at week 4 identifies non-responders with >85% specificity, enabling early switch to alternative therapy.
Rationale
Response to checkpoint blockade requires T-cell infiltration; CT changes lag by months; pseudoprogression confounds RECIST.
What would test it
Run a prospective trial in NSCLC or melanoma with week-4 CD8 PET; randomise PET-non-responders to continue vs switch.
Maturity
early clinical