Background Actinium-225 (225Ac) based targeted alpha therapies (TAT) have emerged as a promising strategy for the treatment of several cancer types due to its favourable decay properties, including high linear energy transfer and short particle range, which enable precise tumour targeting. However, there are limited bifunctional chelators (BFCs) available for 225Ac. In this study, we aim to evaluate the potential of DEPA-based chelators for 225Ac-labelling. Results The BFCs 3p-C-DEPA-NO2, 3p-C-DEPA-NCS, and 3p-C-DEPA-TFP-PEG4 were synthesized with high yield (≥ 86%) and purity (> 96%). Excellent radiochemical conversions (RCCs) were achieved for [225Ac]Ac-3p-C-DEPA-NO2 across a range of concentrations (0.7- 13.4 µg) with high RCC’s (93.7 to 96.8%) after 1 h at room temperature. Stability studies demonstrated that over 95% of this 225Ac-labelled complex remained intact after 6 days in human serum. The HPLC and bioanalyzer analysis of the immunoconjugates 3p-C-DEPA-TFP-PEG4-trastuzumab, DOTA-trastuzumab, 3p-C-DEPA-trastuzumab and macropa-trastuzumab showed 98% purity with less than 2% impurities. A RCC of 94.6% was obtained for [225Ac]Ac-3p-C-DEPA-trastuzumab, 93.5% for [225Ac]Ac-3p-C-DEPA-TFP-PEG4-trastuzumab, 80.9% for [225Ac]Ac-DOTA-trastuzumab, and 96.5% for [225Ac]Ac-macropa-trastuzumab after 2 h incubation at 37 °C. In PBS, high stability of [225Ac]Ac-3p-C-DEPA-TFP-PEG4-trastuzumab was observed (91.3 ± 4.3%), which is comparable to that of [225Ac]Ac-macropa-trastuzumab (81.9 ± 5.6%). In contrast, [225Ac]Ac-3p-C-DEPA-trastuzumab and [225Ac]Ac-DOTA-trastuzumab were less stable in PBS with only 48.3 ± 1.2% and 60.1 ± 0.6% intact tracer left after 10 d. There were no major significant differences between the biodistribution profile of [225Ac]Ac-3p-C-DEPA-trastuzumab, [225Ac]Ac-3p-C-DEPA-TFP-PEG4-trastuzumab, [225Ac]Ac-DOTA-trastuzumab and [225Ac]Ac-macropa-trastuzumab in all organs of interest (p > 0.05 for all organs). Conclusions 3p-C-DEPA-TFP-PEG₄ demonstrated excellent potential as a bifunctional chelator for 225Ac, showing high radiolabelling efficiency under mild conditions and outstanding in vitro stability of the resulting 225Ac-labelled bioconjugate. Further preclinical studies are warranted to validate its therapeutic potential.

Preclinical characterization of 3p-C-DEPA_-NCS and 3p-C-DEPA_-TFP-PEG₄ as potential Actinium-225 bifunctional chelators using DOTA_-NCS and macropa_-NCS as benchmarks

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2025年12月22日

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Jessica Pougoue Ketchemen,
Stephen Ahenkorah,
Emmanuel Nwangele,
Siphelele Siphesihle Pearl Malaza,
Maarten Ooms,
Thomas Cardinaels,
Simon Leekens,
Frederik Cleeren,
Humphrey Fonge

摘要

Background

Actinium-225 (²²⁵Ac) based targeted alpha therapies (TAT) have emerged as a promising strategy for the treatment of several cancer types due to its favourable decay properties, including high linear energy transfer and short particle range, which enable precise tumour targeting. However, there are limited bifunctional chelators (BFCs) available for ²²⁵Ac. In this study, we aim to evaluate the potential of DEPA-based chelators for ²²⁵Ac-labelling.

Results

The BFCs 3p-C-DEPA-_NO2, 3p-C-DEPA-_NCS, and 3p-C-DEPA_-TFP-PEG₄ were synthesized with high yield (≥ 86%) and purity (> 96%). Excellent radiochemical conversions (RCCs) were achieved for [²²⁵Ac]Ac-3p-C-DEPA-_NO2 across a range of concentrations (0.7- 13.4 µg) with high RCC’s (93.7 to 96.8%) after 1 h at room temperature. Stability studies demonstrated that over 95% of this ²²⁵Ac-labelled complex remained intact after 6 days in human serum. The HPLC and bioanalyzer analysis of the immunoconjugates 3p-C-DEPA_-TFP-PEG₄-trastuzumab, DOTA-trastuzumab, 3p-C-DEPA-trastuzumab and macropa-trastuzumab showed 98% purity with less than 2% impurities. A RCC of 94.6% was obtained for [²²⁵Ac]Ac-3p-C-DEPA-trastuzumab, 93.5% for [²²⁵Ac]Ac-3p-C-DEPA_-TFP-PEG₄-trastuzumab, 80.9% for [²²⁵Ac]Ac-DOTA-trastuzumab, and 96.5% for [²²⁵Ac]Ac-macropa-trastuzumab after 2 h incubation at 37 °C. In PBS, high stability of [²²⁵Ac]Ac-3p-C-DEPA_-TFP-PEG₄-trastuzumab was observed (91.3 ± 4.3%), which is comparable to that of [²²⁵Ac]Ac-macropa-trastuzumab (81.9 ± 5.6%). In contrast, [²²⁵Ac]Ac-3p-C-DEPA-trastuzumab and [²²⁵Ac]Ac-DOTA-trastuzumab were less stable in PBS with only 48.3 ± 1.2% and 60.1 ± 0.6% intact tracer left after 10 d. There were no major significant differences between the biodistribution profile of [²²⁵Ac]Ac-3p-C-DEPA-trastuzumab, [²²⁵Ac]Ac-3p-C-DEPA_-TFP-PEG₄-trastuzumab, [²²⁵Ac]Ac-DOTA-trastuzumab and [²²⁵Ac]Ac-macropa-trastuzumab in all organs of interest (p > 0.05 for all organs).

Conclusions

3p-C-DEPA_-TFP-PEG₄ demonstrated excellent potential as a bifunctional chelator for ²²⁵Ac, showing high radiolabelling efficiency under mild conditions and outstanding in vitro stability of the resulting ²²⁵Ac-labelled bioconjugate. Further preclinical studies are warranted to validate its therapeutic potential.

Preclinical characterization of 3p-C-DEPA-NCS and 3p-C-DEPA-TFP-PEG4 as potential Actinium-225 bifunctional chelators using DOTA-NCS and macropa-NCS as benchmarks

摘要

Preclinical characterization of 3p-C-DEPA_-NCS and 3p-C-DEPA_-TFP-PEG₄ as potential Actinium-225 bifunctional chelators using DOTA_-NCS and macropa_-NCS as benchmarks