Development and validation of generic heterogeneous fluoroimmunoassay for bioanalysis of bevacizumab and cetuximab monoclonal antibodies used for cancer immunotherapy

This study describes, for the first time, the development and validation of a highly selective and sensitive heterogeneous fluoroimmunoassay (FIA) for the bioanalysis of two monoclonal antibodies (mAbs) used for cancer immunotherapy: bevacizumab (BEV) and cetuximab (CET). The assay combines reliable non-competitive binding of BEV and CET to their specific cell receptor proteins (human vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFR), respectively) with the highly specific fluorescence activity of the fluorescein isothiocyanate labeled anti-human IgG (FITC-IgG) used as label. The limits of detection were 14.14 and 1.27 × 10³ ng mL^-1 for BEV and CET, respectively. The accuracy and precision of the assay were demonstrated. The assay is simple, convenient, and requires very small volume (~ 5 µL) of plasma sample for analysis. The assay can offer high throughput analysis in clinical settings when modern microplates of multiplies of 96 (up to 6144-wells) are used and/or integrated as a part of automated robotic system. The proposed assay can be used for routine clinical bioanalysis of mAbs with potential application in pharmacokinetics, pharmacodynamics and therapeutic drug monitoring (TDM).

Costs and effects of intra-operative fluorescence molecular imaging - A model-based, early assessment

Introduction

Successful breast conserving cancer surgeries come along with tumor free resection margins and account for cosmetic outcome. Positive margins increase the likelihood of tumor recurrence. Intra-operative fluorescence molecular imaging (IFMI) aims to focus surgery on malignant tissue thus substantially lowering the presence of positive margins as compared with standard techniques of breast conservation (ST). A goal of this paper is to assess the incremental number of surgeries and costs of IFMI vs. ST.

Methods

We developed a decision analytical model and applied it for an early evaluation approach. Given uncertainty we considered that IFMI might reduce the proportion of positive margins found by ST from all to none and this proportion is assumed to be reduced to 10% for the base case. Inputs included data from the literature and a range of effect estimates. For the costs of IFMI, respective cost components were added to those of ST.

Results

The base case reduction lowered number of surgeries (mean [95% confidence interval]) by 0.22 [0.15; 0.30] and changed costs (mean [95% confidence interval]) by €-663 [€-1,584; €50]. A tornado diagram identified the Diagnosis Related Group (DRG) costs, the proportion of positive margins of ST, the staff time saving factor and the duration of frozen section analysis (FSA) as important determinants of this cost.

Conclusions

These early results indicate that IFMI may be more effective than ST and through the reduction of positive margins it is possible to save follow-up surgeries–indicating further health risk–and to save costs through this margin reduction and the avoidance of FSA.

Finger printing of counterfeit bevacizumab and identifying it before clinical use

BACKGROUND

Bevacizumab is widely used for ophthalmic purposes. Recently, counterfeit bevacizumab has become a matter of concern. We analysed samples of suspected counterfeit formulations of bevacizumab and assessed the possibility of using simple tests in the clinic by ophthalmologists to prevent the use of counterfeit preparations in patients.

METHODS

We did a protein analysis using Bradford assay and SDS-PAGE to confirm the presence of bevacizumab in 16 samples - 6 suspected and 10 others. The samples were also subjected to physicochemical analysis such as osmolarity, chloride content and pH. The samples tested negative for protein were analysed by mass spectrometry to detect drugs used in place of bevacizumab. We standardized the method of frothing and precipitation analysis for identifying authentic samples of bevacizumab before their clinical use.

RESULTS

Five of the 16 samples tested were negative for the presence of bevacizumab. The physicochemical parameters also supported the protein analysis test. However, no ionizable organic compound (other drug[s]) was detected by mass spectrometry.

CONCLUSION

Ophthalmic use of counterfeit bevacizumab can be prevented by simple methods such as the frothing and precipitation tests. These can identify the absence of an active drug.

Bevacizumab clearance through the iridocorneal angle following intravitreal injection in a rat model

Antivascular endothelial growth factor (Anti-VEGF) agents have been widely used for a variety of ocular disorders. The etiology of sustained ocular hypertension following intravitreal administration of anti-VEGF agents is yet to be unraveled. Our study investigates and characterizes the presence of intravitreally injected bevacizumab in the aqueous outflow channels of a rat model. Choroidal neovascularization (CNV) was induced by diode laser photocoagulation to the right eye of twelve Brown Norway rats. Bevacizumab (25 mg/ml) was injected intravitreally after 3 days. Immediately after bevacizumab injection, and 3, 6, 24 and 48 h later, animals were euthanized for immunofluorescence staining. Donkey anti-human IgG labeled with Alexa Fluor(®) 488 was used for bevacizumab immunoreactivity detection. Anti-CD31 antibody was used as a marker for Schlemm's canal endothelial cells. Untreated eyes were used as negative controls. The intensity of the immunostaining was analyzed qualitatively. Bevacizumab immunoreactivity was found in the aqueous outflow channels including the trabecular meshwork and Schlemm's canal immediately after injection, and declined incrementally within the following hours. Forty-eight hours after the injection, no bevacizumab staining was detected in the aqueous outflow channel structures. Our manuscript demonstrates the presence of bevacizumab in the trabecular meshwork and Schlemm's canal structures after intravitreal injection in a CNV induced rat model. Bevacizumab molecules passed through the aqueous outflow channels within 48 h after intravitreal bevacizumab injection.