OnCo
termsTerm

Single-arm trial

aka single-arm, single arm, single-arm trial, single-arm phase 2, single-arm study, uncontrolled, non-randomised, nonrandomized, non-randomized, one-arm, open-label single-arm, basket cohort, expansion cohort, phase 2 cohort

A trial where everyone gets the new drug and there is no comparison group; success is judged by how many tumours shrink. Fast and small, and the basis of many accelerated approvals, but it cannot show that patients live longer.

Single-arm phase 2 trials with objective response rate and duration of response as endpoints supported accelerated approvals for many targeted drugs in rare or heavily pretreated populations (larotrectinib, sotorasib, tarlatamab, most CAR-T products) where randomisation was impractical or considered unethical. Their weaknesses are patient selection, lack of a comparator for time-to-event endpoints, and susceptibility to response-evaluable population definitions; the FDA increasingly asks for a randomised confirmatory trial to be under way at approval and has issued guidance on when single-arm data suffice. External or synthetic control arms are attempts to add a comparator after the fact.

Category
Trials & regulation

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