Eradicating mesothelin-positive human gastric and pancreatic tumors in xenograft models with optimized anti-mesothelin antibody–drug conjugates from synthetic antibody libraries

Abstract

Mesothelin (MSLN) is an attractive candidate of targeted therapy for several cancers, and hence there are increasing needs to develop MSLN-targeting strategies for cancer therapeutics. Antibody–drug conjugates (ADCs) targeting MSLN have been demonstrated to be a viable strategy in treating MSLN-positive cancers. However, developing antibodies as targeting modules in ADCs for toxic payload delivery to the tumor site but not to normal tissues is not a straightforward task with many potential hurdles. In this work, we established a high throughput engineering platform to develop and optimize anti-MSLN ADCs by characterizing more than 300 scFv CDR-variants and more than 50 IgG CDR-variants of a parent anti-MSLN antibody as candidates for ADCs. The results indicate that only a small portion of the complementarity determining region (CDR) residues are indispensable in the MSLN-specific targeting. Also, the enhancement of the hydrophilicity of the rest of the CDR residues could drastically increase the overall solubility of the optimized anti-MSLN antibodies, and thus substantially improve the efficacies of the ADCs in treating human gastric and pancreatic tumor xenograft models in mice. We demonstrated that the in vivo treatments with the optimized ADCs resulted in almost complete eradication of the xenograft tumors at the treatment endpoints, without detectable off-target toxicity because of the ADCs’ high specificity targeting the cell surface tumor-associated MSLN. The technological platform can be applied to optimize the antibody sequences for more effective targeting modules of ADCs, even when the candidate antibodies are not necessarily feasible for the ADC development due to the antibodies’ inferior solubility or affinity/specificity to the target antigen.

Antibody CDR amino acids underlying the functionality of antibody repertoires in recognizing diverse protein antigens

“…The computational methodologies related to ISMBLab-H2O have been published by our lab 48 and are described in detail in Supplemental Methods . The LOGO calculation (see Supplemental Methods ) and all the experimental methodologies have been published by our lab 48 , 55 , 64 , 67 and have been used in this work without modification. Other technical details mentioned in this work are described below.…”

Early Immune Remodeling Steers Clinical Response to First-Line Chemoimmunotherapy in Advanced Gastric Cancer

“…Recently, MUC5AC was observed to be enriched among colorectal cancer patients with peritoneal disease, a particularly poor prognosis and fast progressing clinical subgroup ( 38 ). Similarly, MSLN expression is a poor prognostic feature and an active area of investigation for cellular therapies ( 39, 40 ).…”

Tumour organoids and assembloids: Patient‐derived cancer avatars for immunotherapy

“…185 In 2021, China has also approved a clinical trial application for a CAR-NK injection targeting mesothelin for treating advanced epithelial ovarian cancers. 186 Cell-based strategies focus on improving the weakened immune system against cancers by employing advanced biotechnology to collect, modify and expand a patient's immune cells. However, the clinical application of cell therapy requires extensive trials due to individual differences and the distinct roles of various immune cells in the immune system.…”

“…The FDA in the United States has already approved several NK cell therapies, such as FT536 (Fate Therapeutics 536), which is derived from allogeneic, multiply‐engineered iPSCs 185 . In 2021, China has also approved a clinical trial application for a CAR‐NK injection targeting mesothelin for treating advanced epithelial ovarian cancers 186 …”