Ocular Pharmacokinetics of Intravitreally Injected Protein Therapeutics: Comparison among Standard-of-Care Formats

Development of DNA aptamers universally bound to single-chain fragment variables and their applications in bioprocess monitoring

Single-chain fragment variables (scFvs), composed of variable heavy and light chains joined together by a peptide linker, can be produced using a cost-effective bacterial expression system, making them promising candidates for pharmaceutical applications. However, a versatile method for monitoring recombinant-protein production has not yet been developed. Herein, we report a novel anti-scFv aptamer-based biosensing system with high specificity and versatility. First, anti-scFv aptamers were screened using the competitive systematic evolution of ligands by exponential enrichment, focusing on a unique scFv-specific peptide linker. We selected two aptamers, P1-12 and P2-63, with KD = 2.1 μM or KD = 1.6 μM toward anti-human epidermal growth factor receptor (EGFR) scFv, respectively. These two aptamers can selectively bind to scFv but not to anti-EGFR Fv. Furthermore, the selected aptamers recognized various scFvs with different CDRs, such as anti-4-1BB and anti-hemoglobin scFv, indicating that they recognized a unique peptide linker region. An electrochemical sensor for anti-EGFR scFv was developed using anti-scFv aptamers based on square wave voltammetry. Thus, the constructed sensor could monitor anti-EGFR scFv concentrations in the range of 10-500 nM in a diluted medium for bacterial cultivation, which covered the expected concentration range for the recombinant production of scFvs. These achievements promise the realization of continuous monitoring sensors for pharmaceutical scFv, which will enable the real-time and versatile monitoring of large-scale scFv production.

Exploring the Spectrum of VEGF Inhibitors' Toxicities from Systemic to Intra-Vitreal Usage in Medical Practice

The use of Vascular Endothelial Growth Factor inhibitors (VEGFi) has become prevalent in the field of medicine, given the high incidence of various pathological conditions necessitating VEGF inhibition within the general population. These conditions encompass a range of advanced neoplasms, such as colorectal cancer, non-small cell lung cancer, renal cancer, ovarian cancer, and others, along with ocular diseases. The utilization of VEGFi is not without potential risks and adverse effects, requiring healthcare providers to be well-prepared for identification and management. VEGFi can be broadly categorized into two groups: antibodies or chimeric proteins that specifically target VEGF (bevacizumab, ramucirumab, aflibercept, ranibizumab, and brolucizumab) and non-selective and selective small molecules (sunitinib, sorafenib, cabozantinib, lenvatinib, regorafenib, etc.) designed to impede intracellular signaling of the VEGF receptor (RTKi, receptor tyrosine kinase inhibitors). The presentation and mechanisms of adverse effects resulting from VEGFi depend primarily on this distinction and the route of drug administration (systemic or intra-vitreal). This review provides a thorough examination of the causes, recognition, management, and preventive strategies for VEGFi toxicities with the goal of offering support to oncologists in both clinical practice and the design of clinical trials.

Development of an Expression Vector Engineering Strategy Based on tDNA Insulator Element for the Stable Expression of Vascular Endothelial Growth Factor Receptor-Fc Fusion Protein

During the past decades, tremendous advances have occurred in manufacturing recombinant therapeutic proteins in Chinese hamster ovary (CHO) cells. Nevertheless, the production of stable high-producing cell lines has remained a major obstacle in the development process of the CHO cell line. It has been shown that genomic regulatory elements can promote cell line development efficiency by improving transgenes' productivity and stability. Such elements include insulators, ubiquitous chromatin opening elements, scaffold/matrix attachment regions, and antirepressors. In addition, tDNA elements are shown to act as insulators in mammalian cells. This study examines the effect of the tDNA insulator on stable expression of a vascular endothelial growth factor receptor-Fc fusion protein.

Faricimab Effectively Resolves Intraretinal Fluid and Preserves Vision in Refractory, Recalcitrant, and Nonresponsive Neovascular Age-Related Macular Degeneration

PURPOSE

To evaluate the functional and anatomic outcomes of faricimab treatment in patients with neovascular age-related macular degeneration (nAMD) who are unresponsive to other anti-vascular endothelial growth factor (VEGF) therapies.

METHODS

A retrospective interventional study was conducted on patients with refractory nAMD who were initially treated with intravitreal bevacizumab, ranibizumab, or aflibercept. These patients were switched to monthly faricimab injections. The central subfield thickness (CST), intraretinal fluid (IRF) or subretinal fluid (SRF) height, and visual acuities were compared before and after faricimab treatment.

RESULTS

A total of 13 eyes (eight right eyes and five left eyes) from 11 patients were followed for 10.4 ± 6.9 months after bevacizumab treatment and 40.3 ± 28.7 months after aflibercept treatment before switching to faricimab. The follow-up time for patients receiving a mean number of 3.7 ± 1.3 faricimab injections was 3.4 ± 1.2 months. The overall median CST was reduced by 18µm (p=0.001) from 342µm to 318µm, along with a reduction of 89µm (p=0.03) in IRF/SRF height from 97µm to 40µm. Following three consecutive injections, the CST showed a significant reduction of 21.5µm (p=0.004) from 344µm to 322.5µm, and IRF/SRF height was reduced by 89µm (p=0.03) from 104µm to 18.5µm. The intraretinal fluid size decreased and leakage stopped, as seen on fluorescein angiography. Visual acuity remained stable after switching to faricimab treatment (0.59 ± 0.45 logMAR vs 0.58 ± 0.45 logMAR, p=1).

CONCLUSIONS

Faricimab has proven to be an effective treatment for nAMD patients resistant to other anti-VEGF agents. It demonstrates significant anatomical improvement and vision preservation in this challenging patient population.

Ocular therapies with biomacromolecules: From local injection to eyedrop and emerging noninvasive delivery strategies

The last two decades have witnessed a continuously increasing number of biomacromolecules approved for the treatment of ocular diseases. The eye possesses multiple protective mechanisms to resist the invasion of exogenous substances, but meanwhile these physiological defense systems also act as strong barriers, impeding absorption of most biomacromolecules into the eye. As a result, local injections play predominant roles for posterior ocular delivery of biomacromolecules in clinical practice. To achieve safe and convenient application of biomacromolecules, alternative strategies to realize noninvasive intraocular delivery are necessary. Various nanocarriers, novel penetration enhancers and physical strategies have been explored to facilitate delivery of biomacromolecules to both anterior and posterior ocular segments but still suffered difficulties in clinical translation. This review compares the anatomical and physiological characteristics of the eyes from those frequently adopted experimental species and profiles the well-established animal models of ocular diseases. We also summarize the ophthalmic biomacromolecules launched on the market and put emphasis on emerging noninvasive intraocular delivery strategies of peptides, proteins and genes.

Enhanced Biosafety of the Sleeping Beauty Transposon System by Using mRNA as Source of Transposase to Efficiently and Stably Transfect Retinal Pigment Epithelial Cells

Neovascular age-related macular degeneration (nvAMD) is characterized by choroidal neovascularization (CNV), which leads to retinal pigment epithelial (RPE) cell and photoreceptor degeneration and blindness if untreated. Since blood vessel growth is mediated by endothelial cell growth factors, including vascular endothelial growth factor (VEGF), treatment consists of repeated, often monthly, intravitreal injections of anti-angiogenic biopharmaceuticals. Frequent injections are costly and present logistic difficulties; therefore, our laboratories are developing a cell-based gene therapy based on autologous RPE cells transfected ex vivo with the pigment epithelium derived factor (PEDF), which is the most potent natural antagonist of VEGF. Gene delivery and long-term expression of the transgene are enabled by the use of the non-viral Sleeping Beauty (SB100X) transposon system that is introduced into the cells by electroporation. The transposase may have a cytotoxic effect and a low risk of remobilization of the transposon if supplied in the form of DNA. Here, we investigated the use of the SB100X transposase delivered as mRNA and showed that ARPE-19 cells as well as primary human RPE cells were successfully transfected with the Venus or the PEDF gene, followed by stable transgene expression. In human RPE cells, secretion of recombinant PEDF could be detected in cell culture up to one year. Non-viral ex vivo transfection using SB100X-mRNA in combination with electroporation increases the biosafety of our gene therapeutic approach to treat nvAMD while ensuring high transfection efficiency and long-term transgene expression in RPE cells.

Duration of Vascular Endothelial Growth Factor Suppression After Intravitreal Injection of Brolucizumab and Aflibercept in Macaque Eyes

Purpose: To compare the duration of vascular endothelial growth factor (VEGF) suppression in the aqueous humor of macaque eyes after intravitreal injection of brolucizumab and aflibercept. Methods: Clinical dose of intravitreal brolucizumab (IVBr; 6.0 mg/50 μL) or intravitreal aflibercept (IVA; 2 mg/50 μL) was injected into the right eye of each of 8 macaques. Aqueous humor samples (150 μL) from both eyes were obtained just before injection and on days 1, 3, 7, 14, 21, 28, 42, 56, 84, and 112 after IVBr injection or IVA injection. VEGF concentrations were measured using enzyme-linked immunosorbent assays. Results: In the injected eyes, the mean VEGF suppression durations (range) were 4.9 (3-8) weeks for IVBr injection and 6.8 (6-8) weeks for IVA injection (P = 0.04). The VEGF concentrations returned to the preinjection level in the aqueous humor at 12 weeks both after IVBr and IVA injection. In the noninjected fellow eyes, the aqueous VEGF concentrations had decreased least at 1 day after IVBr injection and at 3 days after IVA injection, but were still detectable. The VEGF concentrations in the fellow eyes returned to the preinjection level in the aqueous humor at 1 week after IVBr injection and at 2 weeks after IVA injection. Conclusions: The duration of VEGF suppression in the aqueous humor after IVBr injection may be shorter than that after IVA injection, which may be related with clinical usage.

Aflibercept versus Faricimab in the Treatment of Neovascular Age-Related Macular Degeneration and Diabetic Macular Edema: A Review

Diabetic macular edema (DME) and neovascular age-related macular degeneration (nAMD) are common retinal vascular diseases responsible for most blindness in the working-age and older population in developed countries. Currently, anti-VEGF agents that block VEGF family ligands, including ranibizumab, bevacizumab (off-label use), brolucizumab, and aflibercept, are the first-line treatment for nAMD and DME. However, due to the complex pathophysiological background of nAMD and DME, non-response, resistance during anti-VEGF therapy, and relapses of the disease are still observed. Moreover, frequent injections are a psychological and economic burden for patients, leading to inadequate adhesion to therapy and a higher risk of complications. Therefore, therapeutic methods are strongly needed to develop and improve, allowing for more satisfactory disease management and lower treatment burden. Currently, the Ang/Tie-2 pathway is a promising therapeutic target for retinal vascular diseases. Faricimab is the first bispecific monoclonal antibody for intravitreal use that can neutralize VEGF and Ang-2. Due to the prolonged activity, faricimab allows extending the interval between successive injections up to three or four months in nAMD and DME patients, which can be a significant benefit for patients and an alternative to implanted drug delivery systems.

Hyaluronic Acid-PEG-Based Diels-Alder In Situ Forming Hydrogels for Sustained Intraocular Delivery of Bevacizumab

Retinal diseases are the leading cause of visual impairment worldwide. The effectiveness of antibodies for the treatment of retinal diseases has been demonstrated. Despite the clinical success, achieving sufficiently high concentrations of these protein therapeutics at the target tissue for an extended period is challenging. Patients suffering from macular degeneration often receive injections once per month. Therefore, there is a growing need for suitable systems that can help reduce the number of injections and adverse effects while improving patient complacency. This study systematically characterized degradable "in situ" forming hydrogels that can be easily injected into the vitreous cavity using a small needle (29G). After intravitreal injection, the formulation is designed to undergo a sol-gel phase transition at the administration site to obtain an intraocular depot system for long-term sustained release of bioactives. A Diels-Alder reaction was exploited to crosslink hyaluronic acid-bearing furan groups (HAFU) with 4 arm-PEG10K-maleimide (4APM), yielding stable hydrogels. Here, a systematic investigation of the effects of polymer composition and the ratio between functional groups on the physicochemical properties of hydrogels was performed to select the most suitable formulation for protein delivery. Rheological analysis showed rapid hydrogel formation, with the fastest gel formation within 5 min after mixing the hydrogel precursors. In this study, the mechanical properties of an ex vivo intravitreally formed hydrogel were investigated and compared to the in vitro fabricated samples. Swelling and degradation studies showed that the hydrogels are biodegradable by the retro-Diels-Alder reaction under physiological conditions. The 4APM-HAFU (ratio 1:5) hydrogel formulation showed sustained release of bevacizumab > 400 days by a combination of diffusion, swelling, and degradation. A bioassay showed that the released bevacizumab remained bioactive. The hydrogel platform described in this study offers high potential for the sustained release of therapeutic antibodies to treat ocular diseases.

Yeast-produced fructosamine-3-kinase retains mobility after ex vivo intravitreal injection in human and bovine eyes as determined by Fluorescence Correlation Spectroscopy

Globally, over 2 billion people suffer from vision impairment. Despite complex multifactorial etiology, advanced glycation end products are involved in the pathogenesis of many causative age- and diabetes-related eye diseases. Deglycating enzyme fructosamine-3-kinase (FN3K) was recently proposed as a potential therapeutic, but for further biopharmaceutical development, knowledge on its manufacturability and stability and mobility in the vitreous fluid of the eye is indispensable. We evaluated recombinant production of FN3K in two host systems, and its diffusion behavior in both bovine and human vitreous. Compared to Escherichia coli, intracellular production in Pichia pastoris yielded more and higher purity FN3K. The yeast-produced enzyme was used in a first attempt to use fluorescence correlation spectroscopy to study protein mobility in non-sonicated bovine vitreous, human vitreous, and intact bovine eyes. It was demonstrated that FN3K retained mobility upon intravitreal injection, although a certain delay in diffusion was observed. Alkylation of free cysteines was tolerated both in terms of enzymatic activity and vitreous diffusion. Ex vivo diffusion data gathered and the availability of yeast-produced high purity enzyme now clear the path for in vivo pharmacokinetics studies of FN3K.

Translating pharmacology models effectively to predict therapeutic benefit

Many in vitro and in vivo models are used in pharmacological research to evaluate the role of targeted proteins in a disease. Understanding the translational relevance and limitation of these models for analyzing the disposition, pharmacokinetic/pharmacodynamic (PK/PD) profile, mechanism, and efficacy of a drug, is essential when selecting the most appropriate model of the disease of interest and predicting clinically efficacious doses of the investigational drug. Here, we review selected animal models used in ophthalmology, infectious diseases, oncology, autoimmune diseases, and neuroscience. Each area has specific challenges around translatability and determination of an efficacious dose: new patient-specific dosing methods could help overcome these limitations.

Pharmacokinetics of Monoclonal Antibody and Antibody Fragments in the Mouse Eye Following Systemic Administration

The ocular pharmacokinetics (PK) of antibody-based therapies are infrequently studied in mice due to the technical difficulties in working with the small murine eye. This study is the first of its kind to quantitatively measure the PK of variously sized proteins in the plasma, cornea/ICB, vitreous humor, retina, and posterior cup (including choroid) of the mouse and to evaluate the relationship between molecular weight (MW) and antibody biodistribution coefficient (BC) to the eye. Proteins analyzed include trastuzumab (150 kDa), trastuzumab-vc-MMAE (T-vc-MMAE, 155 kDa), F(ab)₂ (100 kDa), Fab (50 kDa), and scFv (27 kDa). As expected, ocular PK mirrored the systemic PK as plasma was the driving force for ocular exposure. For trastuzumab, T-vc-MMAE, F(ab)₂, Fab, and scFv, respectively, the BCs in the cornea/ICB were 0.610%, 0.475%, 1.74%, 3.39%, and 13.7%; the BCs in the vitreous humor were 0.0198%, 0.0427%, 0.0934%, 0.234%, and 5.56%; the BCs for the retina were 0.539%, 0.230%, 0.704%, 2.44%, and 20.4%; the BCs for the posterior cup were 0.557%, 0.650%, 1.47%, 4.06%, and 13.9%. The relationship between BC and MW was best characterized by a log–log regression in which BC decreased as MW increased, with every doubling in MW leading to a decrease in BC by a factor of 3.44 × , 6.76 × , 4.74 × , and 3.43 × in cornea/ICB, vitreous humor, retina, and posterior cup, respectively. In analyzing the disposition of protein therapeutics to the eye, these findings enhance our understanding of the potential for ocular toxicity of systemically administered protein therapeutics and may aid in the discovery of systemically administered protein therapeutics for ocular disorders.

Ten years in the making: application of CrossMab technology for the development of therapeutic bispecific antibodies and antibody fusion proteins

Bispecific antibodies have recently attracted intense interest. CrossMab technology was described in 2011 as novel approach enabling correct antibody light-chain association with their respective heavy chain in bispecific antibodies, together with methods enabling correct heavy-chain association using existing pairs of antibodies. Since the original description, CrossMab technology has evolved in the past decade into one of the most mature, versatile, and broadly applied technologies in the field, and nearly 20 bispecific antibodies based on CrossMab technology developed by Roche and others have entered clinical trials. The most advanced of these are the Ang-2/VEGF bispecific antibody faricimab, currently undergoing regulatory review, and the CD20/CD3 T cell bispecific antibody glofitamab, currently in pivotal Phase 3 trials. In this review, we introduce the principles of CrossMab technology, including its application for the generation of bi-/multispecific antibodies with different geometries and mechanisms of action, and provide an overview of CrossMab-based therapeutics in clinical trials.