Achievements and perspectives in formulation of stable immunoconjugate of the HER2-targeting trastuzumab – potential for rapid labelling with Gallium-68
To synthesize and evaluate the immunoconjugate of the HER2-targeting trastuzumab with Galium – 68 using already established method of freeze dried kit formulation.
Trastuzumab (Herceptin®) is a humanized IgG1 monoclonal antibody which is approved for therapy of HER2 positive breast cancer. Good clinical results and improvement of the patient’s general condition makes it interesting for further conjugation, in order to increase the therapeutic effect of trastuzumab.
With the development of radiopharmacy many efforts are made for formulation of stable conjugates with various bifunctional chelators, further labelled with radioisotopes (α, β and γ emitters). According to the literature, successful conjugation of trastuzumab is achieved with DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), DTPA (diethylenetriaminepentaacetic acid), TCMC (1,4,7,10-tetra-(2-carbamoyl methyl)-cyclododecane), HYNIC (succinimidyl-6-hydrazino-nicotinamide) and DTPA derivate 1B4M-DTPA (2-(4-isothiocyanatobenzyl)-6-methyl-diethylene-triaminepentaacetic acid).
Significant radiopharmaceuticals based on peptide and antibody for diagnostic and therapeutical purpose used different radioisotopes (99mTc/188Re, 67Ga, 177Lu, 90Y, 131I).
Several studies have shown that already existing radiolabeled formulations, using beta and alfa emitters (90Y-DTPA-trastuzumab, 86Y-DTPA-trastuzumab, 177Lu-DOTA-trastuzumab, 227Th-DOTA-p-benzil-trastuzumab, 225Ac-trastuzumab) are potent against HER2 positive breast cancer.
Our already obtained and published results related tothe method for ready to use production of freeze dried kit formulation of Rituximab imunnoconjugates for labeling with Lu-177 and Y-90 including preclinical assessment of three imunnoconjugates (p-SCN-Bn-DOTA, p-SCN-Bn-DTPA and 1B4M-DTPA ) including chemical characterization, animal imaging, biodistribution and toxicological studies, were good reason to have an indication to introduce the same approach for labeling HER2-targeting trastuzumab using 68Ga3+ under mild conditions without subsequent purification for PET imaging.
Work progress towards objectives and achievements
Progress results and research outcomes critical to work progress and achievements are listed under our project milestones, and referenced to project aims.
Milestone 1: Standardize previously established method used for freeze dried kit formulation of Rituximab imunnoconjugates for HER2-targeting trastuzumabimunnoconjugates.
Milestone 2: Conjugation of bifunctional chelators to targeting for HER2-targeting trastuzumab, and radiolabeling with Ga-68 (define the most appropriate immunoconjugate).
Milestone 3: In vitro characterization and in vivo biodistribution of 68Ga-labeled conjugates.
Significance: Already established method for freeze dried kit formulation of conjugated Rituximab antibody ready for labeling with Lutetium-177, Yttrium-90 for therapeutical purpose that is under the final phase of the evaluation provide good information to introduce the same method for labeling of for HER2-targeting trastuzumab.
The simplicity and efficiency of labelling and the possibility of kit-based 68Ga tracer production without complex automated synthesis typical of multistep PET radiochemistry will greatly increase 68Ga PET access to hospitals, expanding the use of the 68Ga generator.
In the same time give opportunity to work on the same or similar kit formulation using with Lu-177 for therapy.
Key words:bifunctional chelators, breast cancer, immunoconjugates, radioispotopes, trastuzumab.