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Mesothelin/CD3 Half-Life-Extended Bispecific T-Cell Engager Molecule Shows Specific Tumor Uptake and Distributes to
Frans V Suurs1, Grit Lorenczewski2, Julie M Bailis3
1Department of Medical Oncology, University Medical Center Groningen, Groningen, The Netherlands.
Abstract:
Bispecific T-cell engager (BiTE) molecules exert antitumor activity by binding one arm to CD3 on cytotoxic T cells and the other arm to a tumor-associated antigen. Methods: We generated a fully mouse cross-reactive mesothelin-targeted BiTE molecule that is genetically fused to an Fc-domain for half-life extension, and we evaluated the biodistribution and tumor targeting of a 89Zr-labeled mesothelin half-life-extended (HLE) molecule in 4T1 breast cancer-bearing syngeneic mice with PET. The biodistribution of 50 μg of 89Zr-mesothelin HLE BiTE was studied over time by PET imaging in BALB/c mice and revealed uptake in tumor and lymphoid tissues with an elimination half-life of 63.4 h. Results: Compared with a nontargeting 89Zr-control HLE BiTE, the 89Zr-mesothelin HLE BiTE showed a 2-fold higher tumor uptake and higher uptake in lymphoid tissues. Uptake in the tumor colocalized with mesothelin expression, whereas uptake in the spleen colocalized with CD3 expression. Evaluation of the effect of protein doses on the biodistribution and tumor targeting of 89Zr-mesothelin HLE BiTE revealed for all dose groups that uptake in the spleen was faster than in the tumor (day 1 vs. day 5). The lowest dose, 10 μg, of 89Zr-mesothelin HLE BiTE had higher spleen uptake and faster blood clearance than the higher doses, 50 and 200 μg. 89Zr-mesothelin HLE BiTE tumor uptake was similar at all doses. Conclusion: The mesothelin HLE BiTE showed specific tumor uptake, and both arms contributed to the biodistribution profile. These findings support the potential for clinical translation of HLE BiTE molecules.
Insights
A novel mesothelin-targeted bispecific T-cell engager (BiTE) molecule fused to an Fc-domain demonstrated specific tumor uptake in mice. This bispecific T-cell engager molecule shows potential for clinical translation.
Area of Science:
- Immunology
- Oncology
- Biotechnology
Background:
- Bispecific T-cell engager (BiTE) molecules activate T-cells against tumors by targeting CD3 and tumor antigens.
- Mesothelin (MSLN) is a tumor-associated antigen, making it a target for cancer therapy.
- Fc-domain fusion extends the half-life of BiTE molecules, potentially improving their efficacy.
Purpose of the Study:
- To evaluate the biodistribution and tumor targeting of a novel zirconium-89 (89Zr)-labeled mesothelin-targeted half-life extended (HLE) BiTE molecule.
- To assess the impact of different protein doses on the biodistribution and tumor targeting of the 89Zr-MSLN HLE BiTE.
- To investigate the contribution of both arms of the BiTE molecule to its biodistribution profile.
Main Methods:
- Generation of a fully mouse cross-reactive MSLN-targeted BiTE molecule genetically fused to an Fc-domain.
- Radiolabeling of the MSLN HLE BiTE molecule with zirconium-89 (89Zr).
- Positron emission tomography (PET) imaging to study biodistribution and tumor targeting in 4T1 breast cancer-bearing syngeneic mice.
Main Results:
- The 89Zr-MSLN HLE BiTE showed specific uptake in tumors and lymphoid tissues, with an elimination half-life of 63.4 hours.
- Compared to a non-targeting control, the MSLN HLE BiTE exhibited a 2-fold higher tumor uptake.
- Tumor uptake colocalized with MSLN expression, and spleen uptake colocalized with CD3 expression, indicating specific targeting.
- Spleen uptake was faster than tumor uptake across all tested doses (10 µg, 50 µg, 200 µg).
- Tumor uptake was consistent across all doses, while the lowest dose showed faster blood clearance and higher spleen uptake.
Conclusions:
- The MSLN HLE BiTE molecule demonstrates specific tumor targeting and biodistribution influenced by both its CD3 and MSLN-binding arms.
- These preclinical findings support the potential clinical translatability of half-life extended BiTE molecules for cancer therapy.
