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Published on: September 3, 2013
Bispecific small molecule-antibody conjugate targeting prostate cancer
Chan Hyuk Kim1, Jun Y Axup, Brian R Lawson
1Departments of Chemistry, Immunology and Microbial Science, and Molecular Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037.
Abstract:
Bispecific antibodies, which simultaneously target CD3 on T cells and tumor-associated antigens to recruit cytotoxic T cells to cancer cells, are a promising new approach to the treatment of hormone-refractory prostate cancer. Here we report a site-specific, semisynthetic method for the production of bispecific antibody-like therapeutics in which a derivative of the prostate-specific membrane antigen-binding small molecule DUPA was selectively conjugated to a mutant αCD3 Fab containing the unnatural amino acid, p-acetylphenylalanine, at a defined site. Homogeneous conjugates were generated in excellent yields and had good solubility. The efficacy of the conjugate was optimized by modifying the linker structure, relative binding orientation, and stoichiometry of the ligand. The optimized conjugate showed potent and selective in vitro activity (EC50 ~ 100 pM), good serum half-life, and potent in vivo activity in prophylactic and treatment xenograft mouse models. This semisynthetic approach is likely to be applicable to the generation of additional bispecific agents using drug-like ligands selective for other cell-surface receptors.
Insights
Researchers developed a novel semisynthetic method to create bispecific antibody-like drugs targeting prostate cancer. This approach enables precise conjugation of small molecules to antibodies, yielding potent therapeutics with improved properties.
Area of Science:
- Immunology
- Oncology
- Biotechnology
Background:
- Bispecific antibodies offer a novel therapeutic strategy for hormone-refractory prostate cancer by engaging T cells against cancer cells.
- Targeting prostate-specific membrane antigen (PSMA) is a key strategy in prostate cancer therapy.
Purpose of the Study:
- To develop a site-specific, semisynthetic method for producing bispecific antibody-like therapeutics.
- To create a novel therapeutic agent targeting both CD3 on T cells and PSMA on prostate cancer cells.
Main Methods:
- A semisynthetic approach was employed, conjugating a DUPA derivative (PSMA-binding small molecule) to a mutant αCD3 Fab fragment containing an unnatural amino acid.
- Site-specific conjugation was achieved using p-acetylphenylalanine at a defined site within the antibody fragment.
- The linker structure, binding orientation, and ligand stoichiometry were optimized to enhance conjugate efficacy.
Main Results:
- Homogeneous bispecific conjugates were produced in excellent yields with good solubility.
- The optimized conjugate demonstrated potent and selective in vitro activity with an EC50 of approximately 100 pM.
- The conjugate exhibited a favorable serum half-life and potent in vivo efficacy in both prophylactic and treatment xenograft mouse models.
Conclusions:
- A versatile semisynthetic method for generating bispecific antibody-like therapeutics was established.
- This approach allows for the creation of potent and selective cancer therapeutics by conjugating drug-like ligands to antibody fragments.
- The methodology is adaptable for developing bispecific agents targeting other cell-surface receptors and various cancers.
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