# ACTION-1

Source: https://nuclide.cc/trials/action-1/  
Nuclide record `action-1` (Trial). Data CC BY-NC 4.0, attribute "Data from Nuclide (nuclide.cc)"; commercial use needs a licence.

## TL;DR

Tests whether an actinium alpha-radioligand rescues neuroendocrine tumours after lutetium therapy fails.

## Summary

ACTION-1, trial NCT05477576 sponsored by Bristol Myers Squibb through RayzeBio, tests whether the actinium-225 alpha-radioligand RYZ101, or 225Ac-DOTATATE, rescues somatostatin-receptor-positive gastroenteropancreatic neuroendocrine tumours after lutetium-177 somatostatin analogue therapy has failed. Its phase 1b established a fixed dose of 10.2 MBq with encouraging responses, the phase 3 against investigator's choice has closed enrolment (ClinicalTrials.gov status active, not recruiting, 343 participants actual, record updated 5 October 2026; primary completion estimated December 2026), and its dosimetry was published in the Journal of Nuclear Medicine in 2026. Nuclide links it to targeted alpha therapy, actinium-225 DOTATATE, lutetium-177 dotatate and the pairing of beta then alpha PRRT. Whether an alpha emitter can overcome resistance to a beta emitter aimed at the same receptor is the question it will answer.

## Fields

- Kind: Trial
- Status: active
- Last checked: 2026-10-11
- Registry id: NCT05477576
- Phase: 3
- Setting: SSTR-positive GEP-NETs progressing after 177Lu somatostatin-analogue therapy: 225Ac-DOTATATE (RYZ101) vs investigator's choice
- Sponsor: BMS (RayzeBio)
- Enrolled: 343

## Sources

- ClinicalTrials.gov NCT05477576: https://clinicaltrials.gov/study/NCT05477576
- ACTION-1 dosimetry (JNM 2026): https://jnm.snmjournals.org/content/67/8/1239

## Connected records

- isotopes: [Actinium-225](https://nuclide.cc/isotopes/ac-225/), [Lutetium-177](https://nuclide.cc/isotopes/lu-177/)
- indications: [Neuroendocrine tumours](https://nuclide.cc/indications/neuroendocrine/), [Pancreatic neuroendocrine tumours](https://nuclide.cc/indications/pancreatic-net/), [Small intestinal neuroendocrine tumours](https://nuclide.cc/indications/small-intestinal-net/)
- technologies: [Targeted alpha therapy](https://nuclide.cc/technologies/targeted-alpha-therapy/)
- drugs: [Actinium-225 DOTATATE](https://nuclide.cc/drugs/ryz101/), [Lutetium-177 dotatate](https://nuclide.cc/drugs/lutathera/)
- pairings: [Beta PRRT → alpha PRRT](https://nuclide.cc/pairings/prrt-then-alpha-net/)
- bottlenecks: [Actinium-225 supply](https://nuclide.cc/bottlenecks/b-ac225-supply/), [Clinical trial capacity for radioligand therapy](https://nuclide.cc/bottlenecks/b-rlt-trial-capacity/)
- roadmaps: [Alpha-emitter roadmap: radium-223 → 225Ac-PSMA-617 → a phase 3 pipeline](https://nuclide.cc/roadmaps/alpha-therapy-roadmap/), [SSTR theranostics roadmap: octreotide scintigraphy → 68Ga-DOTATATE → 177Lu-DOTATATE → alpha](https://nuclide.cc/roadmaps/sstr-theranostics-roadmap/)

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