Development of a robust reporter-based assay for the bioactivity determination of anti-VEGF therapeutic antibodies

Development of bioassay platforms for biopharmaceuticals using Jurkat-CAR cells by AICD

The assessment of bioactivity for therapeutic antibody release assay poses challenges, particularly when targeting immune checkpoints. An in vitro bioassay platform was developed using the chimeric antigen receptor on Jurkat cells (Jurkat-CAR) to analyze antibodies targeting immune checkpoints, such as CD47/SIRPα, VEGF/VEGFR1, PD-1/PD-L1, and CD70/CD27. For CD47/SIRPα, the platform involved a Jurkat-CAR cell line expressing the chimeric SIRPα receptor (CarSIRPα). CarSIRPα was created by sequentially fusing the SIRPα extracellular region with the CD8α hinge region, the transmembrane (TM) and intracellular (IC) domains of CD28, and the intracellular signaling domain of CD3ζ. The resulting Jurkat-CarSIRPα cells can undergo "activation-induced cell death (AICD)" upon incubation with purified or cellular CD47, as evidenced by the upregulation of CD69, IL-2, and IFN-γ. Similar results also appeared in Jurkat CarVEGFR1, Jurkat CarPD1 and Jurkat CARCD27 cells. These cells are perfectly utilized for the bioactivity analysis of therapeutic antibody. Our study indicates that the established in vitro assay platform based on Jurkat-CAR has been confirmed repeatedly and has shown robust reproducibility; thus, this platform can be used for screening or for release assays of given antibody drugs targeting immune checkpoints.

A bioengineered anti-VEGF protein with high affinity and high concentration for intravitreal treatment of wet age-related macular degeneration

Intravitreal (IVT) injection of anti-vascular endothelial growth factor (anti-VEGF) has greatly improved the treatment of many retinal disorders, including wet age-related macular degeneration (wAMD), which is the third leading cause of blindness. However, frequent injections can be difficult for patients and may lead to various risks such as elevated intraocular pressure, infection, and retinal detachment. To address this issue, researchers have found that IVT injection of anti-VEGF proteins at their maximally viable concentration and dose can be an effective strategy. However, the intrinsic protein structure can limit the maximum concentration due to stability and solution viscosity. To overcome this challenge, we developed a novel anti-VEGF protein called nanoFc by fusing anti-VEGF nanobodies with a crystallizable fragment (Fc). NanoFc has demonstrated high binding affinity to VEGF165 through multivalency and potent bioactivity in various bioassays. Furthermore, nanoFc maintains satisfactory chemical and physical stability at 4°C over 1 month and is easily injectable at concentrations up to 200 mg/mL due to its unique architecture that yields a smaller shape factor. The design of nanoFc offers a bioengineering strategy to ensure both strong anti-VEGF binding affinity and high protein concentration, with the goal of reducing the frequency of IV injections.

Highly Responsive Bioassay for Quantification of Glucocorticoids

Measurement of total cortisol levels in serum samples is currently based on immunoassays or liquid chromatography-mass spectrometry (LC-MS/MS). However, measurement of bioavailable cortisol is laborious, unreliable, and inconvenient for the patient. Therefore, a new versatile assay with the ability to measure both total and bioavailable cortisol from serum represents an important supplement to the current methods. We have generated a cell-based glucocorticoid reporter assay (HEK293F-GRE). The assay was validated for cell line stability, accuracy by dilution, precision, repeatability, reproducibility, and specificity. Additionally, the assay was tested for measuring both total and bioavailable cortisol in serum. The assay showed linearity at five dilution levels with R2 = 0.98 and an accuracy between 0.8 and 1.2. Precision (CV < 20%) was validated down to 3-6 nM dexamethasone, and estimation of the total cortisol concentration was comparable to cortisol immunoassay and LC-MS/MS in most serum samples. Moreover, the assay estimated the bioavailable cortisol fraction in serum samples to a level that agreed with the literature. The HEK293F-GRE assay holds the potential to be a complementary method for estimating cortisol in clinical practice. The ability to quantify bioavailable cortisol directly from serum samples is alluring and provides an opportunity for monitored and personal dose regimens of exogenous glucocorticoids.

Role of Angiogenesis and Its Biomarkers in Development of Targeted Tumor Therapies

Angiogenesis plays a significant role in the human body, from wound healing to tumor progression. "Angiogenic switch" indicates a time-restricted event where the imbalance between pro- and antiangiogenic factors results in the transition from prevascular hyperplasia to outgrowing vascularized tumor, which eventually leads to the malignant cancer progression. In the last decade, molecular players, i.e., angiogenic biomarkers and underlying molecular pathways involved in tumorigenesis, have been intensely investigated. Disrupting the initiation and halting the progression of angiogenesis by targeting these biomarkers and molecular pathways has been considered as a potential treatment approach for tumor angiogenesis. This review discusses the currently known biomarkers and available antiangiogenic therapies in cancer, i.e., monoclonal antibodies, aptamers, small molecular inhibitors, miRNAs, siRNAs, angiostatin, endostatin, and melatonin analogues, either approved by the U.S. Food and Drug Administration or currently under clinical and preclinical investigations.

CRISPR-Cas9 KO Cell Line Generation and Development of a Cell-Based Potency Assay for rAAV-FKRP Gene Therapy

Limb-Girdle Muscular Dystrophy R9 (LGMDR9) is a dystroglycanopathy caused by Fukutin-related protein (FKRP) defects leading to the deficiency of α-DG glycosylation, essential to membrane integrity. Recombinant adeno-associated viral vector (rAAV) gene therapy offers great therapeutic promise for such neuromuscular disorders. Pre-clinical studies have paved the way for a phase 1/2 clinical trial aiming to evaluate the safety and efficacy of FKRP gene therapy in LGMDR9 patients. To demonstrate product activity, quality, and consistency throughout product and clinical development, regulatory authorities request several quality controls, including a potency assay aiming to demonstrate and quantify the intended biological effect of the gene therapy product. In the present study, we generated FKRP knock-out (KO) cells fully depleted of α-DG glycosylation using CRISPR-Cas9 to assess the functional activity of a rAAV-FKRP gene therapy. We then developed a high-throughput On-Cell-Western methodology to evaluate the restoration of α-DG glycosylation in KO-FKRP cells and determine the biological activity of the FKRP transgene. The determination of the half maximal effective concentration (EC50) provides a method to compare the rAAV-FKRP batch using a reference standard. The generation of KO-FKRP muscle cells associated with the high-throughput On-Cell-Western technique may serve as a cell-based potency assay to assess rAAV-FKRP gene therapy products.

Development and application of potency assays based on genetically modified cells for biological products

Potency assays are key to the development, registration, and quality control of biological products. Although previously preferred for clinical relevance, in vivo bioassays have greatly diminished with the advent of dependent cell lines as well as due to ethical concerns. However, for some products, the development of in vitro cell-based assay is challenging, or existing method has limitations such as tedious procedure or low sensitivity. The generation of genetically modified (GM) cell line with improved response to the analyte provides a scientific and promising solution. Potency assays based on GM cell lines are currently used for the quality control of biological products including cytokines, hormones, therapeutic antibodies, vaccines and gene therapy products. In this review, we have discussed the general principles of designing and developing GM cells-based potency assays, including identification of cellular signaling pathways and detectable biological effects, generation of responsive cell lines and constitution of test systems, based on the current research progress. In addition, the applications of some novel technologies and the common concerns regarding GM cells have also been discussed. The research presented in this review provides insights for the development and application of novel GM cells-based potency assays for biological products.

H2O2 down-regulates SIRT7's protective role of endothelial premature dysfunction via microRNA-335-5p

Endothelial senescence is believed to constitute the initial pathogenesis of the atherosclerotic cardiovascular disease (ASCVD). MicroRNA-335-5p (miR-335-5p) expression is significantly up-regulated in oxidative stress-induced endothelial cells (ECs). Sirtuin7 (SIRT7) is considered to prevent EC senescence, yet data on its response to ASCVD risk factors are limited. The present study analyzed the elevated levels of miR-335-5p and the decreased levels of SIRT7 in human umbilical vein endothelial cells (HUVECs), and found that high glucose, tumor necrosis factor-α (TNF-α), and H2O2 are the three contributing factors that induced cellular senescence. The current study also assessed premature endothelial senescence and decreased proliferation, adhesion, migration, and nitric oxide (NO) secretion in HUVECs with these risk factors together with SIRT7-siRNA transfection. It found that the miR-335-5p inhibitor attenuated the down-regulation of SIRT7 expression induced by oxidative stress in HUVECs, and SIRT7 overexpression exerts a rescue effect against miR-335-5p-induced endothelial dysfunction. Furthermore, the direct binding of miR-335-5p to SIRT7 was observed in human embryonic kidney cells 293T (HEK 293T). Therefore, it can be inferred that miR-335-5p down-regulates the expression of SIRT7 in human cells. Current findings may provide deeper insights into the underlying mechanisms of endothelial senescence and potential therapeutic targets of ASCVD as well as other age-related diseases.

Intron-encoded cistronic transcripts for minimally invasive monitoring of coding and non-coding RNAs

Despite their fundamental role in assessing (patho)physiological cell states, conventional gene reporters can follow gene expression but leave scars on the proteins or substantially alter the mature messenger RNA. Multi-time-point measurements of non-coding RNAs are currently impossible without modifying their nucleotide sequence, which can alter their native function, half-life and localization. Thus, we developed the intron-encoded scarless programmable extranuclear cistronic transcript (INSPECT) as a minimally invasive transcriptional reporter embedded within an intron of a gene of interest. Post-transcriptional excision of INSPECT results in the mature endogenous RNA without sequence alterations and an additional engineered transcript that leaves the nucleus by hijacking the nuclear export machinery for subsequent translation into a reporter or effector protein. We showcase its use in monitoring interleukin-2 (IL2) after T cell activation and tracking the transcriptional dynamics of the long non-coding RNA (lncRNA) NEAT1 during CRISPR interference-mediated perturbation. INSPECT is a method for monitoring gene transcription without altering the mature lncRNA or messenger RNA of the target of interest.

The First WHO International Standard for Harmonizing the Biological Activity of Bevacizumab

Several Bevacizumab products are approved for clinical use, with many others in late-stage clinical development worldwide. To aid the harmonization of potency assessment across different Bevacizumab products, the first World Health Organization (WHO) International Standard (IS) for Bevacizumab has been developed. Two preparations of a Bevacizumab candidate and comparator were assessed for their ability to neutralize and bind vascular endothelial growth factor (VEGF) using different bioassays and binding assays in an international collaborative study. Relative potency estimates were similar across different assays for the comparator or the duplicate-coded candidate sample. Variability in relative potency estimates was reduced when the candidate standard was used for calculation compared with various in-house reference standards, enabling harmonization in bioactivity evaluations. The results demonstrated that the candidate standard is suitable to serve as an IS for Bevacizumab, with assigned unitages for VEGF neutralization and VEGF binding activity. This standard coded 18/210 was established by the WHO Expert Committee on Biological Standardization, which is intended to support the calibration of secondary standards for product development and lifecycle management. The availability of IS 18/210 will help facilitate the global harmonization of potency evaluation to ensure patient access to Bevacizumab products with consistent safety, quality and efficacy.

Development of a reporter gene method to measure the bioactivity of anti-CD38 × CD3 bispecific antibody

Background

A T cell-redirecting bispecific antibody (bsAb) consisting of a tumor-binding unit and a T cell-binding unit is a large group of antibody-based biologics against death-causing cancer diseases. The anti-CD38 × anti-CD3 bsAb (Y150) is potential for treating multiple myeloma (MM). When developing a cell-based reporter gene bioassay to assess the activities of Y150, it was found that the expression of CD38 on the human T lymphocyte cells (Jurkat) caused the nonspecific activation, which interfered with the specific T cells activation of mediated by the Y150 and CD38(+) tumor cells.

Methods

Here, we first knocked-out the CD38 expression on Jurkat T cell line by CRISPR-Cas9 technology, then developed a stable monoclonal CD38(−) Jurkat T cell line with an NFAT-RE driving luciferase expressing system. Further based on the CD38(−) Jurkat cell, we developed a reporter gene method to assess the bioactivity of the anti-CD38 × anti-CD3 bsAb.

Results

Knocking out CD38 expression abolished the nonspecific self-activation of the Jurkat cells. The selected stable monoclonal CD38(−) Jurkat T cell line assured the robustness of the report genes assay for the anti-CD38 × anti-CD3 bsAb. The relative potencies of the Y150 measured by the developed reporter gene assay were correlated with those by the flow-cytometry-based cell cytotoxicity assay and by the ELISA-based binding assay.

Conclusions

The developed reporter gene assay was mechanism of action-reflective for the bioactivity of anti-CD38 × anti-CD3 antibody, and suitable for the quality control for the bsAb product.

Local Treatment of Non-small Cell Lung Cancer with a Spray-Dried Bevacizumab Formulation

Local delivery of biotherapeutics to the lung holds great promise for treatment of lung diseases, but development of physically stable, biologically active dry powder formulations of large molecules for inhalation has remained a challenge. Here, spray drying was used to manufacture a dry powder pulmonary formulation of bevacizumab, a monoclonal antibody approved to treat non-small cell lung cancer (NSCLC) by intravenous infusion. By reformulating bevacizumab for local delivery, reduced side effects, lower doses, and improved patient compliance are possible. The formulation had aerosol properties suitable for delivery to the deep lung, as well as good physical stability at ambient temperature for at least 6 months. Bevacizumab’s anti-VEGF bioactivity was not impacted by the manufacturing process. The formulation was efficacious in an in vivo rat model for NSCLC at a 10-fold decrease in dose relative to the intravenous control.

Development and validation of a novel reporter gene assay for determination of recombinant human thrombopoietin

Recombinant human thrombopoietin (rhTPO) was approved by the National Medical Products Administration in 2010 for the treatment of thrombocytopenia in patients with immune thrombocytopenic purpura and chemotherapy-induced thrombocytopenia. Nevertheless, no method for determining rhTPO bioactivity has been recorded in different national/regional pharmacopoeia. Novel methods for lot release and stability testing are needed that are simpler, quicker, and more accurate. Here, we developed a novel reporter gene assay (RGA) for rhTPO bioassay with Ba/F3 cell lines that stably expressed human TPO receptor and luciferase reporter driven by sis-inducible element, gamma response region, and gamma-interferon activated sequence. During careful optimization, the RGA method demonstrated high performance characteristics. According to the International Council for Harmonization Q2 (R1) guidelines and the Chinese Pharmacopoeia 2020 edition, the validation results demonstrated that this method is highly time-saving, sensitive, and robust for research, development, manufacture, and quality control of rhTPO.

A robust reporter assay for the determination of the bioactivity of IL-4R-targeted therapeutic antibodies

Type 2 inflammatory cytokines, including IL-4, IL-5 and IL-13, contribute considerably to the pathogenesis of asthma. Anti-IL-4R monoclonal antibody (mAb) has been approved for the therapeutic treatment of asthma, and many mAbs with the same target are in the different stages of R&D and clinical trials. Bioactivity determination is required to ensure the quality control of mAbs. However, current ELISA and SPR assays or cell-based anti-proliferation assays for IL-4R mAbs are either not mechanism-of-action (MOA) representative or tedious and time consuming. Therefore, we developed a reporter gene assay (RGA) based on the HEK-293 cell line that stably expressed signal transducer and activator of transcription 6 (STAT6) and the luciferase reporter controlled by STAT6 binding elements. Anti-4R mAb could bind to IL-4R, and block the interaction between IL-4 and IL-4R, resulting in the reduction of IL-4 induced STAT6 controlled luciferase expression. After careful optimization of the experiment parameters, the RGA method demonstrated optimal dose-response curve between anti-IL-4R mAb concentration and luciferase expression level. Validation according ICH-Q2 proved the excellent assay performance characteristics of the established RGA, including specificity, accuracy, precision, linearity and range. The established transgenic cell line was stable for the bioactivity determination of anti-IL-4R mAb up to 46 generations, and the RGA was also suitable for the bioactivity determination of anti-IL-4 mAbs, and potentially of anti-IL-13 mAbs. The established RGA could be adopted to determine the bioactivity during the development, characterization, lot release, stability, and comparability studies of anti-IL-4R mAbs.

Light-Controlled Release of Therapeutic Proteins from Red Blood Cells

Protein therapeutics are a powerful class of drugs known for their selectivity and potency. However, the potential efficacy of these therapeutics is commonly offset by short circulatory half-lives and undesired action at otherwise healthy tissue. We describe herein a targeted protein delivery system that employs engineered red blood cells (RBCs) as carriers and light as the external trigger that promotes hemolysis and drug release. RBCs internally loaded with therapeutic proteins are readily surface modified with a dormant hemolytic peptide. The latter is activated via easily assigned wavelengths that extend into the optical window of tissue. We have demonstrated that photorelease transpires with spatiotemporal control and that the liberated proteins display the anticipated biological effects in vitro. Furthermore, we have confirmed targeted delivery of a clot-inducing enzyme in a mouse model. Finally, we anticipate that this strategy is not limited to RBC carriers but also should be applicable to nano- and microtransporters comprised of bilayer lipid membranes.

Development of a robust reporter gene assay for measuring the bioactivity of OX40-targeted therapeutic antibodies

OX40 plays a prominent role in the onset and development of solid tumors, and OX40-targeted monoclonal antibodies (mAbs) have entered clinical trials for various tumors. Bioactivity determination of therapeutic mAbs is of great significance in product quality, however, mechanism of action-based bioassays to determine the bioactivity of anti-OX40 mAbs is still lacking. Here, we established a reporter gene assay system based on two cell lines, namely Jurkat-OX40-NFκB-Luc which stably expresses NFκB-controlled luciferase, and Raji cells which inherently express FcγRs. In the model, FcγRs on Raji cells could crosslink the Fc of anti-OX40 mAbs, which leads to the further crosslinking between Fab of anti-OX40 mAbs and OX40 on Jurkat-OX40-NFκB-Luc cells. OX40 crosslinking could activate Jurkat-OX40-NFκB-Luc cells, and induce the expression of NFκB-controlled luciferase, the extent of which could reflect the bioactivity of anti-OX40 mAbs in a dose-dependent manner. After the optimization of various assay conditions, the validation of the cell-based bioassay showed good assay performance characteristics, including specificity, accuracy, precision, linearity, and stability. This innovative assay that is based on the OX40-NFκB pathway can be a powerful pool to measure the bioactivity of OX40-targeted mAbs.

Rapid preparation of 1-vinylimidazole based non-affinity polymers for the highly-selective purification of antibodies from multiple biological sources

There is an urgent need for developing advanced purification techniques with the merits of low cost and satisfactory capacity in order to meet the challenges in the current downstream purification of monoclonal antibodies (mAbs). Herein, a simple and inexpensive nitrogen heterocycle molecule, 1-vinylimidazole (VIM), was proposed as the capture ligand of antibodies for the first time. The corresponding VIM-based non-affinity polymeric material (polyVIM) was then fabricated via a one-step polymerization for use in the highly selective purification of antibodies. Compared to the previously reported materials, this novel material exhibited many advantages without clearly sacrificing selectivity, such as a simpler and faster fabrication (within 1.5 h), comparable or even higher binding capacity (saturated static adsorption capacity > 190 mg/g polymer, dynamic binding capacity about 31.62 mg/g polymer), lower non-specific protein adsorption, and much lower cost. Notably, the polyVIM can effectively purify the antibodies from multiple biological sources with high purity (95.4% for mAbs in the cell culture medium, 93.3% for hIgG in the human serum), with an acceptable recovery (91.6% for mAbs, 77.0% for hIgG), and good reusability (> 10 times). Moreover, the target ELISA binding assay and NFAT-luc reporter gene assay demonstrated that the enriched antibodies can well maintain their binding activity and bioactivity during the whole purification process. The excellent performance of the polyVIM material may be attributed to the high recognition ability of VIM for antibodies, as well as the biocompatible and antifouling properties of the porous polymer. This study provides a promising alternative material for the purification of mAbs in downstream processes and the enrichment of hIgG in human serum.

Quantification of Bevacizumab Activity Following Treatment of Patients With Ovarian Cancer or Glioblastoma

Highly sensitive reporter-gene assays have been developed that allow both the direct vascular endothelial growth factor (VEGF) neutralizing activity of bevacizumab and the ability of bevacizumab to activate antibody dependent cellular cytotoxicity (ADCC) to be quantified rapidly and in a highly specific manner. The use of these assays has shown that in 46 patients with ovarian cancer following four cycle of bevacizumab treatment, and in longitudinal samples from the two patients that respond to bevacizumab therapy from a small cohort of patients with glioblastoma, that there is a reasonably good correlation between bevacizumab drug levels determined by ELISA and bevacizumab activity, determined using either the VEGF-responsive reporter gene, or the ADCC assays. One of the two primary non-responders with glioblastoma exhibited high levels of ADCC activity suggesting reduced bevacizumab Fc engagement in vivo in contrast to the other primary non-responder, and the two secondary non-responders with a decreasing bevacizumab PK profile, determined by ELISA that exhibited low to undetectable ADCC activity. Drug levels were consistently higher than bevacizumab activity determined using the reporter gene assay in serial samples from one of the secondary non-responders and lower in some samples from the other secondary non-responder and ADCC activity was markedly lower in all samples from these patients suggesting that bevacizumab activity may be partially neutralized by anti-drug neutralizing antibodies (NAbs). These results suggest that ADCC activity may be correlated with the ability of some patients to respond to treatment with bevacizumab while the use of the VEGF-responsive reporter-gene assay may allow the appearance of anti-bevacizumab NAbs to be used as a surrogate maker of treatment failure prior to the clinical signs of disease progression.

A reporter gene assay for measuring the bioactivity of anti-LAG-3 therapeutic antibodies

Although enormous success has been achieved with anti-PD-1/PD-L1 and anti-CTLA-4 monoclonal antibodies (mAbs), their unsatisfactory response rate in cancer patients has been driving the research and development of novel immune checkpoint inhibitors (ICIs). Anti-LAG-3 mAbs, as one of the most promising candidates, are now being tested for various human cancers at different stages of clinical trials. Here, we describe the development and validation of a reporter gene assay (RGA) to measure the bioactivity of anti-LAG-3 mAbs. We established the bioassay based on parental Raji cells and a Jurkat cell line stably transfected with human LAG-3 gene and luciferase reporter elements controlled by nuclear factor of activated T cell (NFAT) from the IL-2 promoter. After optimization of key parameters, the established RGA showed excellent precision, specificity, accuracy, and stability. The mechanism of action (MOA) relatedness and the excellent assay performance make the RGA suitable for the characterization, lot release, and stability test of anti-LAG-3 mAbs.

Best practices in bioassay development to support registration of biopharmaceuticals

Biological activity is a critical quality attribute for biopharmaceuticals, which is accurately measured using an appropriate relative potency bioassay. Developing a bioassay is a complex, rigorous undertaking that needs to address several challenges including modelling all of the mechanisms of action associated with the biotherapeutic. Bioassay development is also an exciting and fast evolving field, not only from a scientific, medical and technological point of view, but also in terms of statistical approaches and regulatory expectations. This has led to an industry-wide discussion on the most appropriate ways to develop, validate and control the bioassays throughout the drug lifecycle.

Responsive Cells for rhEGF bioassay Obtained through Screening of a CRISPR/Cas9 Library

Bioassay of recombinant protein products is important tests to ensure protein effectiveness. Some recombinant protein products have no cells used in their bioassay but instead use animal models, while others have no suitable method. Here, we developed a method to obtain responsive cells used in bioassay of proteins. After screening of a CRISPR/Cas9 library, we obtained a responsive cell line that grew faster in the presence of rhEGF (recombinant human epidermal growth factor) than that of control cells. We used this cell line for bioassay of rhEGF. This cell line, compared with the control cells, had a 2 day shorter operation time and had lower interference. The responsive cell line is more suitable for use in bioassay of rhEGF.

Development of a robust reporter gene based assay for the bioactivity determination of IL-5-targeted therapeutic antibodies

Eosinophilic asthma is characterized by the eosinophilic inflammation with the allergen independent activation of Th2 lymphocytes. Since IL-5 plays an important role in the maturation, survival and migration of eosinophils, hence the pathogenesis of eosinophilic asthma, biotherapeutics targeting IL-5/IL-5Rα have been developed and/or marketed, including Mepolizumab, Reslizumab, and Benralizumab. Accurate determination of bioactivity is crucial for the safety and efficacy of therapeutic antibodies. The current mode of action (MOA) based method used in the quality control and stability tests for anti-IL-5 mAbs is anti-proliferation assay, which is tedious with long duration and high variation. We describe here the development and validation of a reporter gene assay (RGA), based on an IL-5-dependent TF-1 cell line variant we established that stably expresses the luciferase reporter under the control of STAT5 response elements. After careful optimization, we demonstrate the excellent specificity, precision, accuracy and linearity of the established RGA. Our study also proves that the assay is superior on precision, sensitivity and assay simplicity to the anti-proliferation assay. The established RGA is also applicable to another anti-IL-5Rα mAb. These results show for the first time that this novel RGA, based on the IL-5-IL-5R-STAT5 pathway, can be a valuable supplement to the anti-proliferation assay and employed in the bioactivity determination of anti-IL-5/anti-IL-5Rα biotherapeutics.

A new paradigm for antiangiogenic therapy through controlled release of bevacizumab from PLGA nanoparticles

Monoclonal antibodies have deserved a remarkable interest for more than 40 years as a vital tool for the treatment of various diseases. Still, there is a raising interest to develop advanced monoclonal antibody delivery systems able to tailor pharmacokinetics. Bevacizumab is a humanized immunoglobulin IgG1 used in antiangiogenic therapies due to its capacity to inhibit the interaction between vascular endothelial growth factor and its receptor. However, bevacizumab-based antiangiogenic therapy is not always effective due to poor treatment compliance associated to multiples administrations and drug resistance. In this work, we show a promising strategy of encapsulating bevacizumab to protect and deliver it, in a controlled manner, increasing the time between administrations and formulation shelf-life. Nanoencapsulation of bevacizumab represents a significant advance for selective antiangiogenic therapies since extracellular, cell surface and intracellular targets can be reached. The present study shows that bevacizumab-loaded poly (lactic-co-glycolic acid) (PLGA) nanoparticles does not impair its native-like structure after encapsulation and fully retain the bioactivity, making this nanosystem a new paradigm for the improvement of angiogenic therapy.