Among 17 evaluable patients in Full-Life Technologies’ ongoing Phase 1 dose-escalation study, every lutetium-177-naive patient hit a PSA50 response at dose levels 6 to 8 MBq, and three-quarters of those who had already received lutetium-177 therapy did the same. That second group is the one worth watching: patients whose disease progresses after Pluvicto represent a population with few good options, and the ProTACT data presented this week at ESMO 2026 in Madrid include a PSMA-PET complete response in one such patient after just two cycles of [²²⁵Ac]Ac-FL-020 at 7 MBq, in someone whose best prior result on lutetium-177 was progressive disease.
The safety picture through 39 patients has not forced any dose-limiting toxicities, and xerostomia, the salivary-gland toxicity that constrains most PSMA-targeted alpha programs, has stayed predominantly Grade 1 with no Grade 3 cases. Three treatment-related serious adverse events were reported: anemia, nausea, and thrombocytopenia. Dose escalation has continued through 10 MBq without hitting a ceiling, which matters practically because the AcTION trial for actinium-225-PSMA-617 identified 10 MBq as its recommended Phase 2 dose, giving the field a rough benchmark for where efficacy and tolerability tend to converge in this class.
Context around PSA response rates matters here. In the VISION trial, Pluvicto produced a PSA50 rate of 46% in heavily pre-treated mCRPC patients. FL-020’s 88.2% PSA50 across both naive and exposed patients at the same dose levels is striking, though cross-trial comparisons are unreliable at Phase 1 scale with 17 evaluable patients, different baseline characteristics, and no control arm. The company’s own disclosures flag that these preliminary findings may change with additional follow-up.
Full-Life is planning a Phase 2 dose optimization study that will randomize patients across two dosing regimens, a design built to satisfy FDA’s draft guidance on radiopharmaceutical dose optimization. The Phase 2 enrollment criteria, and specifically how the trial splits lutetium-177-naive from lutetium-177-exposed patients, will determine whether the signal in the post-Pluvicto population can be confirmed at a scale that supports a regulatory filing.
[225Ac]Ac-FL-020: the facts in one place
- Also written: 225Ac-FL-020
- Sponsor: Full-Life Technologies
- Mechanism: PSMA-targeted alpha radiopharmaceutical delivering Actinium-225 alpha particles to PSMA-expressing tumor cells
- Indication studied: metastatic castration-resistant prostate cancer (mCRPC)
- Phase: Phase 1
- Enrollment: 18
- Headline result: 100% of lutetium-177-naive patients achieved a PSA50 response at dose levels 6 to 8 MBq; 17 patients evaluable for PSA response
- Registry identifier: NCT06492122
- Current status: Ongoing Phase 1 dose-escalation study; Phase 2 study planned
- FDA IND clearance: May 30, 2024
- FDA Fast Track Designation: July 3, 2024
- Preliminary Phase 1 results announced: October 23, 2026
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
