Targeting Fibroblast Activation Protein with [177Lu]Lu-FAP-2286 in Patients with Advanced Solid Tumors in the Phase I LuMIERE Trial

PURPOSE: Fibroblast activation protein (FAP) is an attractive target for radiopharmaceutical therapy. Phase I of the LuMIERE study (ClinicalTrials.gov, NCT04939610) investigated the safety of [177Lu]Lu-FAP-2286 (177Lu-FAP-2286) in heavily pretreated patients with advanced solid tumors and identified the recommended phase II dosage (RP2D). PATIENTS AND METHODS: LuMIERE is a prospective, open-label, nonrandomized, phase I/II, multicenter study. Phase I followed a Bayesian optimal interval design evaluating four escalating activity levels of 177Lu-FAP-2286 (3.70, 5.55, 7.40, and 9.25 GBq). Patients were selected by positive [68Ga]Ga-FAP-2286 (68Ga-FAP-2286, also known as [68Ga]Ga-HKG301) PET/CT imaging on all target lesions [maximum standardized uptake value (SUVmax) ≥1.5× SUVmean of mediastinal blood pool]. 177Lu-FAP-2286 was administered intravenously every 6 weeks for ≤6 cycles. The primary endpoint was dosage-limiting toxicities (DLT) and treatment-emergent adverse events (TEAE). RESULTS: Of 35 patients imaged with 68Ga-FAP-2286, 27 received 177Lu-FAP-2286 (3.70 GBq, n = 3; 5.55 GBq, n = 6; 7.40 GBq, n = 7; 9.25 GBq, n = 11). Two DLTs were observed: one patient who received 5.55 GBq of 177Lu-FAP-2286 experienced grade 4 lymphopenia, and one patient who received 9.25 GBq experienced grade 3 hemoptysis; these were the only treatment-related grade ≥3 TEAEs. All-cause grade ≥3 TEAEs were reported for 11 patients (40.7%). The RP2D for 177Lu-FAP-2286 monotherapy was determined to be 9.25 GBq. Preliminary Response Evaluation Criteria in Solid Tumors efficacy findings demonstrated a partial response in 1 patient and stable disease in 10 patients (maintained for at least two assessments in 6 patients). CONCLUSIONS: 177Lu-FAP-2286 was well tolerated in patients with advanced solid tumors. The safety and preliminary efficacy findings support its continued development in phase II.