Phase I dose-escalation study of [¹⁷⁷Lu]Lu-LNC1011, a long-circulating dansyl-modified PSMA theranostics, in metastatic castration-resistant prostate cancer.

RATIONALE: [177Lu]Lu-D-Dan-Phe-PSMA ([177Lu]Lu-LNC1011) is a novel long-circulating prostate-specific membrane antigen (PSMA) therapeutic radioligand. This Phase I study aimed to investigate its safety, dosimetry, and initial treatment efficacy in metastatic castration-resistant prostate cancer (mCRPC) patients.

METHODS

This open-label, non-randomized, Phase I dose-escalation trial enrolled mCRPC patients with PSMA-positive lesions confirmed by PSMA PET/CT. A total of nine patients received [177Lu]Lu-LNC1011 at administered activity levels of 1.85 GBq, 2.78 GBq, and 3.70 GBq.

RESULTS

During the dose-limiting toxicity (DLT) observation period, no DLTs occurred in any activity group. The cumulative absorbed dose to organs increased with the injected activity. The effective dose to the whole body was 1.30E-01 ± 1.91E-02 mSv/MBq. The kidneys received the highest radiation dose (3.33 ± 1.09 Gy/GBq), consistent with the expected biodistribution of PSMA-targeted ligands. For salivary glands and red bone marrow, the absorbed doses were 1.70 ± 1.04 Gy/GBq and 0.11 ± 0.03 Gy/GBq, respectively. The mean absorbed dose to tumors was 12.29 ± 6.50 Gy/GBq. The effective half-life of [177Lu]Lu-LNC1011 was 49.44 ± 12.58 h in the whole body and 128.3 ± 62.79 h in tumor lesions. After two treatment cycles, the 3.70 GBq cohort (n = 3) demonstrated 100% PSA reduction (3/3), with 66.7% (2/3) achieving ≥50% PSA decline; simultaneously, Response Evaluation Criteria in PSMA PET/CT (RECIP) 1.0 assessment showed partial response (PR) in 66.7% (2/3) of patients and stable disease (SD) in 33.3% (1/3).

CONCLUSION

[177Lu]Lu-LNC1011 was well tolerated across all dose levels, delivering high tumor-absorbed doses and prolonged tumor retention. The 3.70 GBq cohort demonstrated notable therapeutic efficacy. These favorable safety, dosimetry, and efficacy findings support the investigation of extended multi-cycle treatment with [¹⁷⁷Lu]Lu-LNC1011 at 3.70 GBq per cycle in future clinical studies.