Conformational characterization of a novel anti-HER2 candidate antibody.

Regulatory agencies establish that a broad physicochemical and biological characterization is necessary for the evaluation of comparability between a biosimilar candidate product and a reference commercial drug. Between them, conformational characterization of proteins is of vital importance to determine its folding and biological functions. In this work, the conformational features of a novel monoclonal antibody (called 5G4) were evaluated by means of circular dichroism spectroscopy and fluorescence. Secondary structure and thermal stability of mAbs were determined by circular dichroism in the far ultraviolet, while three-dimensional folding of proteins was analyzed by both circular dichroism in the near ultraviolet and intrinsic tryptophan fluorescence. In all experiments, Herceptin (Roche) was used as control. Both antibodies showed a composition of secondary structure predominantly of ß-sheets (55-56%) and thermal stability of ~ 75°C, suggesting structural similarity. The three-dimensional folding of proteins was also similar due to the absorption spectra of the aromatic residues and the emission wavelength maxima by fluorescence were comparable. The values of the fluorescence attenuation constant (Stern-Volmer constant) for increasing concentrations of acrylamide were also similar, suggesting a degree of exposure of tryptophan residues similar, although it was slightly decreased for Herceptin. Our data permit to consider that 5G4 monoclonal antibody showed similar conformational characteristics when compared with Herceptin.

Validation of a flow cytometry based binding assay for evaluation of monoclonal antibody recognizing EGF receptor.

An ideal test used to characterize a product must be appropriate for the measurement of product quality, manufacturing consistency, product stability, and comparability studies. Flow cytometry has been successfully applied to the examination of antibodies and receptors on membrane surfaces; however, to date, the analytical validation of cytometry based assays is limited. Here we report on the validation of a flow cytometry-based assay used in the evaluation of nimotuzumab binding to cells over-expressing EGFR on cell surface. The assay was validated by examining, assay robustness, specificity, repeatability and intermediate precision. The assay was highly specific, robust for all studied factors except for cell fixation with 1% paraformaldehyde and met criteria for precision with RSD < 2%. In addition the assay has stability-indicating properties evidenced by the ability to detect changes in mAb degraded samples. Most importantly, the assay demonstrated to be useful for its intended use.

Detección inmunohistoquímica del receptor del factor de crecimiento epidérmico: revisión de algunos aspectos técnicos relacionados / Immunohistochemical detection of the epidermal growth factor receptor: review of some related technical aspects

Introducción: En los últimos años la inmunohistoquímica (IHQ) se ha convertido en el método más usado en la determinación de la expresión del receptor del factor de crecimiento epidérmico (REGF). La falta de control de algunos aspectos técnicos durante su determinación en muestras de tejidos fijados en formol e incluidos en parafina, como por ejemplo, la fijación tisular y el procesamiento de las muestras, la elección de un método adecuado de reanimación antigénica, el empleo de diferentes anticuerpos anti-REGF y sistemas de detección, a llegado a tal punto que la confiabilidad y reproducibilidad de la detección inmunohistoquímica de la sobreexpresión del REGF está siendo fuertemente cuestionada. Objetivo: La estandarización de estos procedimientos constituye una de las metas más perseguidas actualmente, con el objetivo de continuar empleando la sobreexpresión del REGF por IHQ como criterio de elección y predictor de la respuesta al tratamiento, sin necesidad de recurrir a técnicas más complejas para su detección, disminuyendo en gran medida a la variabilidad intra e interlaboratorios. Métodos: Revisión y determinación de la pertinencia en el control de la técnica investigativa y viabilidad de la misma. Conclusiones: La determinación de la sobreexpresión del REGF por IHQ continúa siendo el método más empleado actualmente como predictor de la respuesta a la terapia contra el receptor. La heterogeneidad de las muestras, la falta de estandarización de los procedimientos inmunohistoquímicos empleados, la existencia de numerosos protocolos con un mismo fin, así como otras fuentes de variabilidad, han conducido a la obtención de resultados poco confiables y reproducibles

Background: In recent years, immunohistochemistry (IHC) has become the most widely used method in determining the expression of epidermal growth factor receptor (EGFR). The lack of control of some technical aspects during their determination in formaldehyde fixed and paraffin embedded tissue such as tissue fixation and sample processing, the choice of a suitable antigen retrieval method, the use of different anti-EGFR antibodies and the detection systems have come to the point that the reliability and reproducibility of the imunohistochemical analysis of EGFR overexpression is being seriously questioned. Objective: The standardization of these procedures is one of most pursued goals at present, with the aim to continue using EGFR overexpression by IHC as selection criteria and predictor of treatment response, without resorting to most complex techniques for its detection, greatly diminishing the intra and inter laboratory variation. Methods: A review and determination of the relevance in the control of the investigative technique and its feasibility was made. Conclusions: The determination of EGFR overexpression by IHC continues being the most used method at present as predictor of the response to the therapy against the receptor. The heterogeneity of the samples, the lack of standardization of the most used immunohistochemical procedures, the existence of several protocols with the same goal, as well as other sources of variability have led to obtaining hardly reliable and reproducible results