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Phase 1b portion of the ACTION-1 phase 1b/3 trial of RYZ101 in gastroenteropancreatic neuroendocrine tumors (GEP-NET) progressing after 177 Lu somatostatin analogue (SSA) therapy: Safety and efficacy findings

J. Strosberg, Michael Morris, G. Ulaner, Daniel Halperin, S. Mehr, Daneng Li, Heloisa P Soares, Lowell B. Anthony et al.

Journal of Clinical Oncology, 2025

15 participants · 4 citations

Abstract

661

Background:

RYZ101 (

225

Ac-DOTATATE) is an alpha-emitting radiopharmaceutical in development for SSTR2+ solid tumors. Alpha-particles have a shorter path length/higher linear energy transfer than beta-particles, causing more frequent double-strand DNA breaks and potentially improving the therapeutic index. ACTION-1 (NCT05477576) is a two-part, global, randomized, controlled, open-label, phase 1b/3 trial of RYZ101 in advanced, well-differentiated SSTR+ GEP-NETs progressing after

177

Lu-SSA therapy. Herein, we report updated results from the phase 1b portion of the trial.

Methods:

The phase 1b portion of the ACTION-1 trial had a dose de-escalation/Bayesian optimal interval design with boundaries based on a dose-limiting toxicity (DLT) rate of 25%. Patients received RYZ101 IV every 8 weeks for 4 cycles. Planned dose levels (n=6/level): Level 0 (starting dose) 120 kBq/kg; Level 1 90 kBq/kg; Level 2 60 kBq/kg. DLTs were assessed for 56 days after the first RYZ101 dose. Treatment-emergent adverse events (TEAEs) were graded by NCI-CTCAE v5.0. A Data Review Committee oversaw dose de-escalation decisions/safety data. Tumor response was assessed locally by RECIST v1.1.

Results:

Seventeen patients received at least one dose of RYZ101 at 120 kBq/kg (4 doses: 15 patients; 2 doses: 2 patients; median 8.3 MBq). Baseline patient characteristics: median age 63 years; male (n=11); ECOG PS 0/1 (n=10/7); primary tumor site GI/pancreas (n=12/5). As of 14 December 2023, the most frequent…

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