Dosimetry Results from the Phase 1b/3 ACTION-1 Trial of [(225)Ac]Ac-DOTATATE (RYZ101) in Patients with Somatostatin Receptor-Expressing, Well-Differentiated GEP-NETs

What Was Tested

The paper reports a study of Octreotide and Somatostatin, published as a randomized controlled trial.

ACTION-1 included a dosimetry substudy to determine the feasibility of obtaining imaging data with 225Ac.

Why It Was Studied

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are biologically and clinically heterogeneous tumors, most of which overexpress somatostatin receptors (SSTRs).

The presence of SSTRs enables staging and allows patient selection for treatment with radiolabeled somatostatin analogs (SSAs), such as DOTATATE. [225Ac]Ac-DOTATATE is an α-emitting radiopharmaceutical in development for the treatment of patients with SSTR2-expressing solid tumors. α particles have a shorter path length and higher linear energy transfer than do β particles, leading to largely irreparable double-strand DNA breaks and cytotoxicity.

Who Took Part

The study group was 4 adults.

The age groups tagged for this paper are adults, middle-aged adults and older adults, both men and women.

How the Study Was Run

The researchers set it up as a randomized and open-label study.

The adults were allocated by chance, so the Octreotide group and the comparison group should start out alike.

Nothing was hidden in this open-label Octreotide study: the adults and staff both knew the treatment.

Dosimetry was assessed after cycles 1 and 4 of [225Ac]Ac-DOTATATE via SPECT/CT of 221Fr (4.8-min half-life), the first daughter and surrogate for 225Ac and 213Bi (46.6-min half-life, surrogate for later daughters).

What Was Measured

Topics PubMed links to this paper include Receptors, Somatostatin, Neuroendocrine Tumors, Octreotide, Radiometry, Stomach Neoplasms, Pancreatic Neoplasms and Intestinal Neoplasms.

Author keywords: 225Ac, DOTATATE, GEP-NETs, RYZ101, dosimetry and targeted α-therapy.

What This Means in Plain Language

The paper is a randomized and open-label study of Octreotide and Somatostatin in 4 adults.

With fewer than 40 people, it is a small study, so it is better read as an early signal for further research than as a settled answer.

The publication is from 2026 (Journal of nuclear medicine : official publication, Society of Nuclear Medicine), a journal based in United States.

More context: the Octreotide compound page and the Somatostatin compound page, all human trials.