On August 17, 2022 Advanced Proteome Therapeutics Corporation (TSXV: APC) (FSE: 0E81) ("APC" or the "Company"), reported that its US subsidiary, Advanced Proteome Therapeutics Inc. ("APTI"), has had its technology featured in a peer-reviewed publication (Press release, Advanced Proteome Therapeutics, AUG 17, 2022, View Source [SID1234622592]).

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The manuscript entitled, "Lysine-Directed Site-Selective Bioconjugation for the Creation of Radioimmunoconjugates" by Sarrett, et al. has been published in the prestigious journal, Bioconjugate Chemistry. Bioconjugate Chemistry is a peer-reviewed journal focused on bioconjugation and published by the American Chemical Society. The manuscript is available online and will be included in a forthcoming issue of the journal. The publication represents the final results of the previously announced collaboration between APTI and the Zeglis lab at the City University of New York to investigate APTI’s site-selective conjugation in the rapidly growing field of radioimmunoconjugates (RICs). The collaboration evaluated APTI’s site-selective conjugation approach using the antibody pertuzumab, an antibody that targets the HER2 receptor, which is overexpressed on many malignancies including breast and gastric cancer. In the study, APTI’s conjugate was compared with conjugates prepared with two of the most common approaches to antibody conjugation – cysteine maleimide and NHS ester. The conjugates were tested in vitro for key characteristics including stability and target binding and in two in vivo models – BT-474 breast cancer (all 3 constructs) and SKOV-3 ovarian cancer (APTI and NHS ester). Key findings from the study include:

APTI’s radioconjugate was >99% stable in human serum over 5 days
APTI’s radioconjugate was >99% free from aggregation over 14 days
APTI’s radioconjugate exhibited higher immunoreactivity (binding) to the HER2 receptor than the cysteine maleimide construct.
APTI’s radioconjugate exhibited no interference with Fc receptor binding
In vivo – BT-474 model, PET biodistribution tumor activity concentrations at 144 h post-injection (%ID/g):
APTI conjugate: 126.9 ± 50.3
Cysteine maleimide control: 86.9 ± 53.2
NHS ester control: 92.5 ± 27.2
In vivo – SKOV-3 model, biodistribution at 144 h post-injection (%ID/g):
APTI conjugate: 34.5 ± 20.0
NHS ester control: 21.5 ± 13.4
Dr. Benjamin Krantz, President and CEO of APTI, commented, "I am thrilled by the publication of the results of our collaboration with the Zeglis lab in Bioconjugate Chemistry. Bioconjugate Chemistry is one of the most important journals in the field of bioconjugation and its publication there provides significant visibility to potential collaborators. Our results speak for themselves. We again demonstrated that our conjugation approach using simple chemistry creates highly homogeneous antibody conjugates that are rock solid stable and maintain the properties of the native antibodies. In vivo, in two challenging models, we demonstrated numerically higher tumor uptake than the comparator molecules made with the most common approaches to antibody conjugate production. It is easy to see why we are excited about our technology, this data, and the opportunities that will come as it is disseminated."

Dr. Brian Zeglis commented, "It has been wonderful working with APTI on this project. I have been impressed with APTI’s highly modular and facile approach to bioconjugate production. It is the easiest approach to site-specific conjugation. The study clearly showed that APTI’s radioimmunoconjugates exhibited exceptional in vitro and in vivo performance and were better-defined and more homogeneous than traditional methods. I also believe that APTI’s strategy holds several key advantages over existing approaches to site-selective bioconjugation including production for the clinic. I look forward to APTI’s continued development of this promising technology."