Bevacizumab (Avastin®) ELISA Kit

Enzyme-linked immunosorbent assay (ELISA) for the quantitative determination of Bevacizumab (Avastin®) in serum and plasma. The Assay Genie Bevacizumab (Avastin®) ELISA has been developed for the quantitative analysis of the biologically active form of free Bevacizumab (Avastin®) in serum and plasma samples.

Solid phase enzyme-linked immunosorbent assay (ELISA) based on the double antigen assay principle. Diluted standards and samples (serum or plasma) are incubated in the microtitre plate coated with human vascular endothelial growth factor (VEGF). After incubation, the wells are washed. A biotin conjugated human VEGF is added and binds to bevacizumab (Avastin®) captured by the reactant on the surface of the wells. Following incubation, wells are washed and then HRP conjugated probe (HRP) is added. After incubation, the wells are washed, and the bound enzymatic activity is detected by addition of chromogen-substrate. The colour developed is proportional to the amount of bevacizumab in the sample or standard. Results of samples can be determined directly using the standard curve.

Bevacizumab (Avastin®) is a recombinant human IgG1:k monoclonal antibody specific for all human vascular endothelial growth factor-A (VEGF-A) isoforms. Bevacizumab carrries out anti-VEGF function by binding circulating VEGF, which in-turn inhibits the binding of VEGF to its cell surface receptors. This inhibition results in a decrease in microvascular growth of tumor blood vessels and therefore limits the blood supply to tumor tissues.

In 1997, the humanization of the murine anti-VEGF mAb was reported. Like its murine counterpart, bevacizumab binds to and neutralizes all human VEGF-A isoforms and bioactive proteolytic fragments, but not mouse or rat VEGF. However, bevacizumab was observed to inhibit the growth of human tumor cell lines in nude mice.

The humanized anti-VEGF monoclonal antibody, bevacizumab, has been approved by the FDA as a first-line treatment for metastatic colorectal cancer in combination with chemotherapy. Furthermore, VEGF is implicated in intraocular neovascularization associated with diabetic retinopathy and age-related macular degeneration.

In 1997, Phase I clinical trials with bevacizumab were initiated. These Phase I studies showed that bevacizumab as a single agent was relatively non-toxic and including standard chemotherapy regimens did not significantly exacerbate chemotherapy associated toxicities.

In 1998, several Phase II studies were initiated with bevacizumab in different tumor types, either as a single agent or in combination with chemotherapy. bevacizumab was combined with Standard first-line chemotherapy in metastatic colorectal cancer and stage IIIb/IV non-small cell lung cancer. The potential clinical utility of VEGF inhibition in oncology is not limited to solid tumors. There is growing evidence that VEGF and VEGF receptors are expressed by a variety of leukemias and other hematologic malignancies. This suggests that inhibition of VEGF or VEGFR signaling may have a role in the treatment of such conditions. Several clinical trials are currently testing these hypotheses.

Although bevacizumab was generally well tolerated, some adverse events were noted. Several open-label Phase I and II clinical trials identified thrombosis and bleeding as potential bevacizumab-related toxicities. Typically, adverse reactions include epistaxis, headache, hypertension, rhinitis, proteinuria, taste alteration, dry skin, rectal hemorrhage, lacrimation disorder, back pain and exfoliative dermatitis.

Studies have demonstrated that bevacizumab, in combination with chemotherapy, resulted in increased survival in patients. These were patients with previously untreated metastatic colorectal cancer. The treatment was compared to chemotherapy as a stand-alone treatment. This lead to FDA approval of the first anti-angiogenic agent.

Anti-VEGF monoclonal antibodies and other VEGF inhibitors block the growth of several tumor cell lines in nude mice. Clinical trials with VEGF inhibitors in a variety of malignancies are ongoing. The pharmacokinetic properties of bevacizumab in several species have been previously described and are consistent with a typical humanized monoclonal antibody.

Bevacizumab is administered up to 15 mg/kg (Non- squamous non-small cell lung cancer: 15 mg/kg IV every 3 weeks with carboplatin/paclitaxel) in patients without evidence of dose limiting toxicities.