(188)Re-SSS Lipiodol Radioembolization in HCC Patients: Results of a Phase 1 Trial (Lip-Re-01 Study)

SIMPLE SUMMARY: Radioembolization is a kind of internal radiation therapy which is currently used in non-operable HCC. Several radiolabeled product can be used as (90)Y-loaded microspheres or less frequently radiolabeled lipiodol either with iodine 131 (in the past) or currently with rhenium 188 ((188)Re). Currently used (188)Re-labeled compounds are limited by in vivo instability. This study sought to evaluate the safety, bio-distribution, and response to (188)Re-SSS lipiodol, a new and more stable compound. Method: Lip-Re-01 was an activity-escalation Phase 1 study involving HCC patients progressing after sorafenib. The primary endpoint was safety. Secondary endpoints included bio-distribution and response evaluation. Results: Fourteen heavily pre-treated HCC patients were treated in Level 1 (n = 6), Level 2 (n = 6), and Level 3 (n = 2). Safety was acceptable with only 1/6 of Level 1 and 1/6 of Level 2 patients experiencing limiting toxicity. The study was prematurely discontinued unrelated to clinical outcomes. Cumulative urinary elimination and fecal eliminations at 72 h were very low, confirming high in vivo stability. Partial response occurred in 37.5% of the patients receiving 3.6 GBq of (188)Re-SSS lipiodol or more. Conclusion: As the 3.6 GBq activity proved to be safe, it will be used in an ongoing Phase 2 study. ABSTRACT: Background: Despite the wide development of (90)Y-loaded microspheres, (188)Re-labeled lipiodol is still being used for radioembolization of hepatocellular carcinoma (HCC). However, the use of this latter compound is limited by in vivo instability. This study sought to evaluate the safety, bio-distribution, and response to (188)Re-SSS lipiodol, a new and more stable compound. Method: Lip-Re-01 was an activity-escalation Phase 1 study involving HCC patients progressing after sorafenib. The primary endpoint was safety based on Common Terminology Criteria for Adverse Events (AEs) of Grade ≥3 within 2 months. Secondary endpoints included bio-distribution assessed by scintigraphy quantification from 1 to 72 h, tumor to non-tumor uptake ratio (T/NT), as well as blood, urine and feces collection over 72 h, dosimetry, and response evaluation (mRECIST). Results: Overall, 14 heavily pre-treated HCC patients were treated using a whole liver approach. The mean injected activity was 1.5 ± 0.4 GBq for activity Level 1 (n = 6), 3.6 ± 0.3 GBq for Level 2 (n = 6), and 5.0 ± 0.4 GBq for Level 3 (n = 2). Safety was acceptable with only 1/6 of Level 1 and 1/6 of Level 2 patients experiencing limiting toxicity (one liver failure; one lung disease). The study was prematurely discontinued unrelated to clinical outcomes. Uptake occurred in the tumor, liver, and lungs, and only sometimes in the bladder. The T/NT ratio was high with a mean of 24.9 ± 23.4. Cumulative urinary elimination and fecal eliminations at 72 h were very low, 4.8 ± 3.2% and 0.7 ± 0.8%, respectively. Partial response occurred in 21% of patients (0% in the first activity level; 37.5% in the others). Conclusion: The high in vivo stability of (188)Re-SSS lipiodol was confirmed, resulting in encouraging responses for a Phase 1 study. As the 3.6 GBq activity proved to be safe, it will be used in a future Phase 2 study.