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Site-Specifically Labeled Antibody–Drug Conjugate for Simultaneous Therapy and ImmunoPET

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journal contribution
posted on 22.01.2018, 00:00 by Pierre Adumeau, Delphine Vivier, Sai Kiran Sharma, Jessica Wang, Terry Zhang, Aimei Chen, Brian J. Agnew, Brian M. Zeglis
The conjugation of antibodies with cytotoxic drugs can alter their in vivo pharmacokinetics. As a result, the careful assessment of the in vivo behavior, and specifically the tumor-targeting properties, of antibody–drug conjugates represents a crucial step in their development. In order to facilitate this process, we have created a methodology that facilitates the dual labeling of an antibody with both a toxin and a radionuclide for positron emission tomography (PET). To minimize the impact of these modifications, this chemoenzymatic approach leverages strain-promoted azide–alkyne click chemistry to graft both cargoes to the heavy chain glycans of the immuoglobulin’s Fc domain. As a proof-of-concept, a HER2-targeting trastuzumab immunoconjugate was created bearing both a monomethyl auristatin E (MMAE) toxin as well as the long-lived positron-emitting radiometal 89Zr (t1/2 ≈ 3.3 days). Both the tumor targeting and therapeutic efficacy of the 89Zr-trastuzumab-MMAE immunoconjugate were validated in vivo using a murine model of HER2-expressing breast cancer. The site-specifically dual-labeled construct enabled the clear visualization of tumor tissue via PET imaging, producing tumoral uptake of ∼70%ID/g. Furthermore, a longitudinal therapy study revealed that the immunoconjugate exerts significant antitumor activity, leading to a >90% reduction in tumor volume over the course of 20 days.