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[(64) Cu]-labelled trastuzumab: optimisation of labelling by DOTA and NODAGA conjugation and initial evaluation in
Christina Schjoeth-Eskesen1,2, Carsten Haagen Nielsen1,2, Søren Heissel3
1Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen, Denmark.
Abstract:
The human epidermal growth factor receptor-2 (HER2) is overexpressed in 20-30% of all breast cancer cases, leading to increased cell proliferation, growth and migration. The monoclonal antibody, trastuzumab, binds to HER2 and is used for treatment of HER2-positive breast cancer. Trastuzumab has previously been labelled with copper-64 by conjugation of a 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelator. The aim of this study was to optimise the (64) Cu-labelling of DOTA-trastuzumab and as the first to produce and compare with its 1,4,7-triazacyclononane, 1-glutaric acid-5,7 acetic acid (NODAGA) analogue in a preliminary HER2 tumour mouse model. The chelators were conjugated to trastuzumab using the activated esters DOTA mono-N-hydroxysuccinimide (NHS) and NODAGA-NHS. (64) Cu-labelling of DOTA-trastuzumab was studied by varying the amount of DOTA-trastuzumab used, reaction temperature and time. Full (64) Cu incorporation could be achieved using a minimum of 10-µg DOTA-trastuzumab, but the fastest labelling was obtained after 15 min at room temperature using 25 µg of DOTA-trastuzumab. In comparison, 80% incorporation was achieved for (64) Cu-labelling of NODAGA-trastuzumab. Both [(64) Cu]DOTA-trastuzumab and [(64) Cu]NODAGA-trastuzumab were produced after purification with radiochemical purities of >97%. The tracers were injected into mice with HER2 expressing tumours. The mice were imaged by positron emission tomography and showed high tumour uptake of 3-9% ID/g for both tracers.
Insights
Researchers optimized copper-64 labeling of DOTA-trastuzumab for HER2-positive breast cancer imaging. Both DOTA-trastuzumab and NODAGA-trastuzumab showed high tumor uptake in mice, demonstrating their potential for PET imaging.
Area of Science:
- Nuclear medicine
- Oncology
- Radiopharmaceutical chemistry
Background:
- HER2 is overexpressed in 20-30% of breast cancers, driving tumor growth.
- Trastuzumab, a HER2-targeting antibody, is a standard treatment.
- Copper-64 labeled trastuzumab, using DOTA chelators, is used for HER2-positive cancer imaging.
Purpose of the Study:
- Optimize (64)Cu-labeling of DOTA-trastuzumab.
- Produce and compare (64)Cu-NODAGA-trastuzumab with (64)Cu-DOTA-trastuzumab.
- Evaluate tracer uptake in a HER2-positive tumor mouse model.
Main Methods:
- Conjugation of DOTA and NODAGA chelators to trastuzumab via NHS esters.
- Optimization of (64)Cu labeling conditions (amount of antibody, temperature, time).
- Production and purification of radiolabeled tracers.
- Positron Emission Tomography (PET) imaging in HER2-expressing tumor-bearing mice.
Main Results:
- Optimized (64)Cu-DOTA-trastuzumab labeling achieved fastest results with 25 µg at room temperature for 15 min.
- NODAGA-trastuzumab showed 80% (64)Cu incorporation.
- Both tracers achieved >97% radiochemical purity.
- PET imaging revealed high tumor uptake (3-9% ID/g) for both tracers.
Conclusions:
- Efficient labeling protocols were established for both (64)Cu-DOTA-trastuzumab and (64)Cu-NODAGA-trastuzumab.
- Both tracers demonstrate significant tumor uptake in a preclinical HER2-positive breast cancer model.
- These findings support their further investigation for clinical PET imaging of HER2-positive cancers.
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