Background: Antibody-drug conjugates (ADCs) have ushered in a new era of precision oncology by combining the targeting specificity of monoclonal antibodies with the potent cytotoxicity of chemotherapeutic drugs. However, the cellular and molecular mechanisms underlying their dose-limiting ocular toxicity remain unclear. Elahere™, the first FDA-approved ADC targeting folate receptor α (FRα), demonstrates remarkable efficacy in platinum-resistant ovarian cancer but causes keratitis and other ocular toxicities in some patients. Notably, FRα is not expressed in the corneal epithelium—the primary site of damage—highlighting the urgent need to elucidate its underlying mechanisms. The aim of this study was to identify the cell-type-specific molecular mechanisms underlying Elahere-induced ocular toxicity. Methods: Sprague-Dawley rats were treated with intravenous Elahere (20 mg/kg) or vehicle weekly for five weeks. Ocular toxicity was determined by clinical examination and histopathology. Corneal single-cell suspensions were analyzed using the BD Rhapsody single-cell RNA sequencing (scRNA-seq) platform. Bioinformatic analyses to characterize changes in corneal cell populations, gene expression, and signaling pathways included cell clustering, differential gene expression, pseudotime trajectory inference, and cell-cell interaction modeling. Results: scRNA-seq profiling of 47,606 corneal cells revealed significant damage to the ocular surface and corneal epithelia in the Elahere group. Twenty distinct cell types were identified. Elahere depleted myeloid immune cells; in particular, homeostatic gene expression was suppressed in phagocytic macrophages. Progenitor populations (limbal stem cells and basal cells) accumulated (e.g., a ~2.6-fold expansion of limbal stem cells), while terminally differentiated cells decreased in corneal epithelium, indicating differentiation blockade. Endothelial cells exhibited signs of injury and inflammation, including reduced angiogenic subtypes and heightened stress responses. Folate receptor alpha, the target of Elahere, was expressed in endothelial and stromal cells, potentially driving stromal cells toward a pro-fibrotic phenotype. Fc receptor genes were predominantly expressed in myeloid cells, suggesting a potential mechanism underlying their depletion. Conclusions: Elahere induces complex, multi-compartmental ocular toxicity characterized by initial perturbations in vascular endothelial and immune cell populations followed by the arrest of epithelial differentiation and stromal remodeling. These findings reveal a cascade of cellular disruptions and provide mechanistic insights into mitigating Elahere-associated ocular side effects.

Background/Objectives: This study comprehensively characterized the O- and N-glycosylation profiles of bispecific antibodies (BsAbs) via advanced analytical techniques to evaluate their structural and functional implications. Methods: High-resolution MS revealed O-xylosylation at Ser468 within the (G4S)4 linker peptide, which was identified as xylose with a molecular weight of 132.042 Da. HILIC-HPLC analysis of N-glycosylation revealed glycan species engineered to eliminate Fc effector functions. O-glycosylation analysis via β-elimination followed by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) identified xylose as the predominant glycan. Results: O-xylosylation does not affect the binding of BsAbs to either antigen Programmed Death-1 (PD-1) or Vascular Endothelial Growth Factor (VEGF). Notably, O-xylosylation interactions with mannose receptor represent the first discovery highlighting potential immunomodulatory roles. Conclusions: This study highlights the critical importance of monitoring comprehensive glycosylation characterization during the development of BsAb with (G4S)n linkers to ensure optimal therapeutic efficacy, safety, and reduced immunogenic potential.

The identification of the critical quality attributes (CQAs) of monoclonal antibodies (mAbs) is a key component of quality by design. Traditional detection methods for the identification of mAbs, such as peptide mapping and weak cation‐exchange chromatography (WCX‐HPLC), require sophisticated equipment, experienced staff, and a considerable amount of time. In this study, the novel identification of mAbs was performed using Raman spectroscopy, combined with the evaluation of other CQAs, such as the appearance and purity of size‐exclusion high‐performance liquid chromatography(SEC‐HPLC), charge heterogeneity of WCX‐HPLC, and bioassay. Raman spectroscopy achieved comparable results to the conventional, but complex, approach to identifying anti‐vascular endothelial growth factor antibodies. Raman spectroscopy was used to identify and distinguish between different antibody types. Additionally, the Raman technique with principal component analysis of multivariate algorithms is rapid, efficient, and accurate for mAb identification; this technique has great potential to support biopharmaceutical development and counterfeiters.

Antibody–drug conjugates (ADCs) are a pivotal technology for precision cancer therapy, harnessing the synergistic effects of antibody targeting and toxin delivery. However, traditional ADCs encounter limitations in efficacy that stem from tumor resistance, heterogeneity, and intense target competition. Dual-payload ADCs (DP-ADCs) represent a promising solution to these challenges, as they leverage dual mechanisms of action that mitigate acquired drug resistance and enhance adaptability to tumor heterogeneity. The complex structure of DP-ADCs presents substantial quality control hurdles. In this manuscript, we review the current payload selection and conjugation strategies of DP-ADCs and examine recent advances in quality control research. Specifically, we analyze the analytical challenges related to the quantification of free toxins, the determination of the total antibody content, and the characterization of the drug-to-antibody ratio and its distribution. Ultimately, the aim of this work is to provide valuable guidance for future DP-ADC quality control analyses to facilitate their clinical translation and application.

Background: Therapeutic recombinant biological products are essential in modern medicine, but their immunogenicity remains a major concern for both clinical safety and therapeutic efficacy. Protein aggregation may occur during manufacturing, storage, transportation, and administration, potentially increasing immune recognition. Here, we have reviewed the mechanisms underlying aggregation-associated immunogenicity and summarized strategies for mitigating the associated risks. Methods: We integrated published evidence on therapeutic recombinant proteins, monoclonal antibodies, antibody–drug conjugates, peptide and glycoprotein hormones, and recombinant blood products. We focused on aggregation-induced structural changes, immune activation pathways, differences among product types and aggregation states, and approaches for controlling aggregation and mitigating immunogenicity. Results: Protein aggregation creates or reveals neoepitopes by disrupting the native conformational state, exposing previously buried hydrophobic regions, and generating nonnative interfaces. Aggregates may further promote innate and adaptive immune responses through repetitive epitope presentation, pattern-recognition receptor signaling, complement activation, cytokine release, dendritic-cell maturation, enhanced antigen presentation, and B-cell receptor cross-linking, ultimately increasing the likelihood of anti-drug antibody formation. Aggregate size and morphology, protein characteristics, formulation, storage conditions, administration route, and other biological factors influence the immunogenic potential of aggregates. Thus, effective risk reduction requires integrated control strategies, including molecular and structural optimization, formulation design, manufacturing-process control, appropriate storage and transportation, and sensitive analytical monitoring. Emerging artificial-intelligence approaches may further facilitate the prediction and design of low-immunogenicity biologics. Conclusions: Protein aggregation is a multifactorial determinant of immunogenicity. Controlling aggregation throughout the product lifecycle is essential to reduce immune-mediated risks and maintain safety, stability, and efficacy of therapeutic recombinant biological products.

Anti-CD25 antibodies have been approved for renal transplantation and has been used prior to and during transplantation by the Food and Drug Administration (FDA). However, no reported bioassays have been reflected the mechanism of action (MOA) of anti-CD25 antibodies. Here, we describe the development and validation of a reporter gene assay (RGA) based on the engineered C8166-STAT5RE-Luc cells expressing endogenous IL-2 receptors and a STAT5-inducible element-driven firefly luciferase in C8166 cell lines. The RGA was fully validated according to the International Conference on the Harmonization of Technical Requirements for the Registration of Pharmaceuticals for the Human Use-Q2 (ICH-Q2). After optimization, the assay showed excellent specificity, linearity, accuracy, precision, and robustness. Due to the MOA relatedness and the excellent assay performance, the RGA is suitable for exploring the critical quality attributes (CQAs), release inspection, comparability and stability of anti-CD25 mAbs.