Subcutaneous delivery of monoclonal antibodies: How do we get there?

DeepSP: Deep learning-based spatial properties to predict monoclonal antibody stability

Therapeutic antibody development faces challenges due to high viscosities and aggregation tendencies. The spatial charge map (SCM) and spatial aggregation propensity (SAP) are computational techniques that aid in predicting viscosity and aggregation, respectively. These methods rely on structural data derived from molecular dynamics (MD) simulations, which are computationally demanding. DeepSCM, a deep learning surrogate model based on sequence information to predict SCM, was recently developed to screen high-concentration antibody viscosity. This study further utilized a dataset of 20,530 antibody sequences to train a convolutional neural network deep learning surrogate model called Deep Spatial Properties (DeepSP). DeepSP directly predicts SAP and SCM scores in different domains of antibody variable regions based solely on their sequences without performing MD simulations. The linear correlation coefficient between DeepSP scores and MD-derived scores for 30 properties achieved values between 0.76 and 0.96 with an average of 0.87. DeepSP descriptors were employed as features to build machine learning models to predict the aggregation rate of 21 antibodies, and the performance is similar to the results obtained from the previous study using MD simulations. This result demonstrates that the DeepSP approach significantly reduces the computational time required compared to MD simulations. The DeepSP model enables the rapid generation of 30 structural properties that can also be used as features in other research to train machine learning models for predicting various antibody stability using sequences only. DeepSP is freely available as an online tool via https://deepspwebapp.onrender.com and the codes and parameters are freely available at https://github.com/Lailabcode/DeepSP.

Development and characterization of a first-in-class adjustable-dose gene therapy system

INTRODUCTION

Despite significant potential, gene therapy has been relegated to the treatment of rare diseases, due in part to an inability to adjust dosage following initial administration. Other significant constraints include cost, specificity, antigenicity, and systemic toxicity of current generation technologies. To overcome these challenges, we developed a first-in-class adjustable-dose gene therapy system, with optimized biocompatibility, localization, durability, and cost.

METHODS

A lipid nanoparticle (LNP) delivery system was developed and characterized by dynamic light scattering for size, zeta potential, and polydispersity. Cytocompatibility and transfection efficiency were optimized in vitro using primary human adipocytes and preadipocytes. Durability, immunogenicity, and adjustment of expression were evaluated in C57BL/6 and B6 albino mice using in vivo bioluminescence imaging. Biodistribution was assessed by qPCR and immunohistochemistry; therapeutic protein expression was quantified by ELISA.

RESULTS

Following LNP optimization, in vitro transfection efficiency of primary human adipocytes reached 81.3 % ± 8.3 % without compromising cytocompatibility. Critical physico-chemical properties of the system (size, zeta potential, polydispersity) remained stable over a broad range of genetic cassette sizes (1,871-6,203 bp). Durable expression was observed in vivo over 6 months, localizing to subcutaneous adipose tissues at the injection site with no detectable transgene in the liver, heart, spleen, or kidney. Gene expression was adjustable using several physical and pharmacological approaches, including cryolipolysis, focused ultrasound, and pharmacologically inducible apoptosis. The ability of transfected adipocytes to express therapeutic transgenes ranging from peptides to antibodies, at potentially clinically relevant levels, was confirmed in vitro and in vivo.

CONCLUSION

We report the development of a novel, low-cost therapeutic platform, designed to enable the replacement of subcutaneously administered protein treatments with a single-injection, adjustable-dose gene therapy.

Prediction of subcutaneous drug absorption - Development of novel simulated interstitial fluid media for predictive subcutaneous in vitro assays

Media that mimic physiological fluids at the site of administration have proven to be valuable in vitro tools for predicting in vivo drug release, particularly for routes of administration where animal studies cannot accurately predict human performance. The objective of the present study was to develop simulated interstitial fluids (SISFs) that mimic the major components and physicochemical properties of subcutaneous interstitial fluids (ISFs) from preclinical species and humans, but that can be easily prepared in the laboratory and used in in vitro experiments to estimate in vivo drug release and absorption of subcutaneously administered formulations. Based on data from a previous characterization study of ISFs from different species, two media were developed: a simulated mouse-rat ISF and a simulated human-monkey ISF. The novel SISFs were used in initial in vitro diffusion studies with a commercial injectable preparation of liraglutide. Although the in vitro model used for this purpose still requires significant refinement, these two new media will undoubtedly contribute to a better understanding of the in vivo performance of subcutaneous injectables in different species and will help to reduce the number of unnecessary in vivo experiments in preclinical species by implementation in predictive in vitro models.

Lyophilised protein formulations as a patient-centric dosage form: A contribution toward sustainability paradigm

At present, society has embraced the fact apropos population aging and climate changes, that demand, amongst others, innovative pharmaceutical technologies, emphasising the development of patient-specific delivery systems and thus the provision of efficient and sustainable drugs. Protein drugs for subcutaneous administration, by allowing less frequent application, represent one of the most important parts of the pharmaceutical field, but their development is inevitably faced with obstacles in providing protein stability and suitable formulation viscosity. To gain further knowledge and fill the gaps in the already constructed data platform for the development of monoclonal antibody formulations, we designed a study that examines small model proteins, i.e., bovine serum albumin. The main aim of the presented work is to evaluate the effect of protein concentrations on critical quality attributes of both, pre-lyophilised liquid formulations, and lyophilised products. Through the study, the hypothesis that increasing protein concentration leads to higher viscosity and higher reconstitution time without affecting the stability of the protein was confirmed. The most important finding is that sucrose plays a key role in the lyophilisation of investigated protein, nevertheless, it can be predicted that, to ensure the beneficial effect of mannitol, its amount has to prevail over the amount of sucrose.

Modeling the subcutaneous pharmacokinetics of antibodies co-administered with rHuPH20

Predicting the subcutaneous (SC) pharmacokinetics (PK) of antibodies in humans is challenging, with clinical data currently being the only reliable data source for modeling SC absorption and bioavailability. Recombinant human hyaluronidase PH20 (rHuPH20) is an enzyme that facilitates SC delivery of high-dose, high-volume therapeutics. Numerous monoclonal antibodies have been co-administered SC with rHuPH20 in a clinical setting, establishing an extensive PK database. The goal of this work is to demonstrate how aggregated clinical data can be leveraged in a universal modeling framework for characterizing SC antibody PK, resulting in parameterization that can be used in predictive simulations of new antibodies. Data for 10 individual antibodies co-administered SC with rHuPH20 were obtained from publicly available sources. PK modeling of each antibody was conducted using the same model structure, but uniquely parameterized. The model structure consisted of a two-compartment model to capture linear kinetics, plus a target-binding mechanism to accommodate nonlinear kinetics driven by antibody-target complex formation and elimination. The clinical PK profiles for all antibodies were accurately described using the universal modeling framework. The SC PK parameters of absorption and bioavailability were consistent across the range of antibody and target properties evaluated. SC administration with rHuPH20 yielded a 30% increase in absorption rate on average and similar or better bioavailability. These parameter values can serve as initial conditions for model-based PK predictions for new antibodies co-administered SC with rHuPH20 to enable evaluation of optimal SC dose and schedule regimens prior to and during clinical development.

Key characteristics of anti-CD20 monoclonal antibodies and clinical implications for multiple sclerosis treatment

The recent success of anti-CD20 monoclonal antibody therapies in the treatment of multiple sclerosis (MS) has highlighted the role of B cells in the pathogenesis of MS. In people with MS, the inflammatory characteristics of B-cell activity are elevated, leading to increased pro-inflammatory cytokine release, diminished anti-inflammatory cytokine production and an accumulation of pathogenic B cells in the cerebrospinal fluid. Rituximab, ocrelizumab, ofatumumab, ublituximab and BCD-132 are anti-CD20 therapies that are either undergoing clinical development, or have been approved, for the treatment of MS. Despite CD20 being a common target for these therapies, differences have been reported in their mechanistic, pharmacological and clinical characteristics, which may have substantial clinical implications. This narrative review explores key characteristics of these therapies. By using clinical trial data and real-world evidence, we discuss their mechanisms of action, routes of administration, efficacy (in relation to B-cell kinetics), safety, tolerability and convenience of use. Clinicians, alongside patients and their families, should consider the aspects discussed in this review as part of shared decision-making discussions to improve outcomes and health-related quality of life for people living with MS.

Quantifying Protein Shape to Elucidate Its Influence on Solution Viscosity in High-Concentration Electrolyte Solutions

Therapeutic proteins with a high concentration and low viscosity are highly desirable for subcutaneous and certain local injections. The shape of a protein is known to influence solution viscosity; however, the precise quantification of protein shape and its relative impact compared to other factors like charge-charge interactions remains unclear. In this study, we utilized seven model proteins of varying shapes and experimentally determined their shape factors (v) based on Einstein's viscosity theory, which correlate strongly with the ratios of the proteins' surface area to the 2/3 power of their respective volumes, based on protein crystal structures resolved experimentally or predicted by AlphaFold. This finding confirms the feasibility of computationally estimating protein shape factors from amino acid sequences alone. Furthermore, our results demonstrated that, in high-concentration electrolyte solutions, a more spherical protein shape increases the protein's critical concentration (C*), the transition concentration beyond which protein viscosity increases exponentially relative to concentration increases. In summary, our work elucidates protein shape as a key determinant of solution viscosity through quantitative analysis and comparison with other contributing factors. This provides insights into molecular engineering strategies to optimize the molecular design of therapeutic proteins, thus optimizing their viscosity.

The medicinal chemistry evolution of antibody-drug conjugates

Antibody-drug conjugates (ADCs) comprise 3 components of wildly differing sizes: antibody (150 000 Da), linker (typically <500 Da) and payload (typically <500 Da). While the drug-linker makes up only a small percent of the ADC it has a disproportionately massive impact on all aspects of the ADC. Replacing maleimide with bromoacetamide (BrAc) affords stable attachment of the linker to the antibody cysteine, supports total flexibility for linker design and affords a more homogenous ADC. Optimisation of the protease cleavable dipeptide reduces aggregation, facilitates moderation of the physicochemical properties of the ADC and enables long-term stability to facilitate subcutaneous self-administration. Payloads are designed specifically to afford the optimal ADC. Structural information and SAR guide design to improve both potency and selectivity to the small molecule target improving the therapeutic index of resulting ADCs. Minimising the solvent exposed hydrophobic surface area improves the drug-like properties of the ADC, the realisation that the attachment heteroatom can be more than just the site for linker attachment as it can also drive potency and selectivity of the payload and the adoption of a prodrug strategy at project initiation are key areas that medicinal chemistry drives. For an optimal ADC the symbiotic relationship of the three structurally disparate components requires they all function in unison and medicinal chemistry has a huge role to ensure this happens.

A compartment model for subcutaneous injection of monoclonal antibodies

Despite the growing popularity of subcutaneous (SC) administration for monoclonal antibodies (mAbs), there remains a limited understanding of the significance of mAb transport rate constants within the interstitial space and the lymphatic system on their pharmacokinetics. To bridge this knowledge gap, we introduce a compartmental model for subcutaneously administered mAbs. Our model differentiates FcRn-expressing cells across various sites, and the model predictions agree with experimental data from both human and rat studies. Our findings indicate that the time to reach the maximum mAb concentration in the plasma, denoted by Tmax, displays a weak positive correlation with mAb half-life and a negligible correlation with bioavailability. In contrast, the half-life of mAbs exhibits a strong positive correlation with bioavailability. Moreover, the rate of mAb transport from lymph to plasma significantly affects the mAb half-life. Increasing the transport rates of mAbs from the injection site to the lymph or from lymph to plasma enhances bioavailability. These insights, combined with our compartmental model, contribute to a deeper understanding of the pharmacokinetics of subcutaneously administered mAbs.

Variable domain mutational analysis to probe the molecular mechanisms of high viscosity of an IgG1 antibody

Subcutaneous injection is the preferred route of administration for many antibody therapeutics for reasons that include its speed and convenience. However, the small volume limit (typically ≤ 2 mL) for subcutaneous delivery often necessitates antibody formulations at high concentrations (commonly ≥100 mg/mL), which may lead to physicochemical problems. For example, antibodies with large hydrophobic or charged patches can be prone to self-interaction giving rise to high viscosity. Here, we combined X-ray crystallography with computational modeling to predict regions of an anti-glucagon receptor (GCGR) IgG1 antibody prone to self-interaction. An extensive mutational analysis was undertaken of the complementarity-determining region residues residing in hydrophobic surface patches predicted by spatial aggregation propensity, in conjunction with residue-level solvent accessibility, averaged over conformational ensembles from molecular dynamics simulations. Dynamic light scattering (DLS) was used as a medium throughput screen for self-interaction of ~ 200 anti-GCGR IgG1 variants. A negative correlation was found between the viscosity determined at high concentration (180 mg/mL) and the DLS interaction parameter measured at low concentration (2-10 mg/mL). Additionally, anti-GCGR variants were readily identified with reduced viscosity and antigen-binding affinity within a few fold of the parent antibody, with no identified impact on overall developability. The methods described here may be useful in the optimization of other antibodies to facilitate their therapeutic administration at high concentration.

Multiphysics Simulation of Local Transport and Absorption Coupled with Pharmacokinetic Modeling of Systemic Exposure of Subcutaneously Injected Drug Solution

INTRODUCTION

Subcutaneous (SC) injectables have become more acceptable and feasible for administration of biologics and small molecules. However, efficient development of these products is limited to costly and time-consuming techniques, partially because absorption mechanisms and kinetics at the local site of injection remain poorly understood.

OBJECTIVE

To bridge formulation critical quality attributes (CQA) of injectables with local physiological conditions to predict systemic exposure of these products.

METHODOLOGY

We have previously developed a multiscale, multiphysics computational model to simulate lymphatic absorption and whole-body pharmacokinetics of monoclonal antibodies. The same simulation framework was applied in this study to compute the capillary absorption of solubilized small molecule drugs that are injected subcutaneously. Sensitivity analyses were conducted to probe the impact by key simulation parameters on the local and systemic exposures.

RESULTS

This framework was capable of determining which parameters had the biggest impact on small molecule absorption in the SC. Particularly, membrane permeability of a drug was found to have the biggest impact on drug absorption kinetics, followed by capillary density and drug diffusivity.

CONCLUSION

Our modelling framework proved feasible in predicting local transport and systemic absorption from the injection site of small molecules. Understanding the effect of these properties and how to model them may help to greatly expedite the development process.

Systemic peptide amphiphile nanofiber delivery following subcutaneous injection

Peptide amphiphile (PA) nanofibers have been shown to target and deliver drugs when administered via an intravenous (IV) injection. Subcutaneous administration can broaden the applicability of PA nanofibers in the medical field. The ability of PA nanofibers to be absorbed into systemic circulation after subcutaneous administration was investigated. Four PA molecules with different amino acid sequences were designed to understand the effect of nanofiber cohesion and charge on uptake. Solution small-angle X-ray scattering confirmed nanostructure morphology and provided characteristic lengths for co-assemblies. Circular dichroism and solution wide-angle X-ray scattering confirmed PA secondary structure and molecular order. PAs were co-assembled in a 95 %:5 % molar ratio of unlabeled PA to fluorescently labeled PA. Male and female Sprague Dawley rats were injected in the nape of the neck with PA co-assemblies. In vivo normalized abdominal fluorescence was measured 1-72 h after injection. PA nanofibers with a negative charge and low internal order showed the highest amount of systemic absorption at 1, 6, and 24 h. At 24 h after injection, white blood cell count decreased and glucose was elevated. Glucose began to decrease at 48 h. These data indicate that PA nanofibers can be absorbed into the systemic circulation after subcutaneous injection.

MPET2: a multi-network poroelastic and transport theory for predicting absorption of monoclonal antibodies delivered by subcutaneous injection

Subcutaneous injection of monoclonal antibodies (mAbs) has attracted much attention in the pharmaceutical industry. During the injection, the drug is delivered into the tissue producing strong fluid flow and tissue deformation. While data indicate that the drug is initially uptaken by the lymphatic system due to the large size of mAbs, many of the critical absorption processes that occur at the injection site remain poorly understood. Here, we propose the MPET² approach, a multi-network poroelastic and transport model to predict the absorption of mAbs during and after subcutaneous injection. Our model is based on physical principles of tissue biomechanics and fluid dynamics. The subcutaneous tissue is modeled as a mixture of three compartments, i.e., interstitial tissue, blood vessels, and lymphatic vessels, with each compartment modeled as a porous medium. The proposed biomechanical model describes tissue deformation, fluid flow in each compartment, the fluid exchanges between compartments, the absorption of mAbs in blood vessels and lymphatic vessels, as well as the transport of mAbs in each compartment. We used our model to perform a high-fidelity simulation of an injection of mAbs in subcutaneous tissue and evaluated the long-term drug absorption. Our model results show good agreement with experimental data in depot clearance tests.

A comprehensive evaluation of arginine and its derivatives as protein formulation stabilizers

Arginine and its derivatives (such as arginine ethyl ester and acetyl arginine) have varying degrees of protein aggregation suppressor effect across different protein solutions. To understand this performance ambiguity, we evaluated the activity of arginine, acetyl arginine, and arginine ethyl ester for aggregation suppressor effect against human intravenous immunoglobulin G (IgG) solution at pH 4.8. Both arginine and its cationic derivative arginine ethyl ester in their hydrochloride salt forms significantly reduced the colloidal and conformational stability (reduced kd and Tm) of IgG. Consequently, the monomer content was decreased with an increase in subvisible particulates after agitation or thermal stress. Furthermore, compared to arginine, arginine ethyl ester with one more cationic charge and hydrochloride salt form readily precipitated IgG at temperatures higher than 25 °C. On the contrary, acetyl arginine, which mostly exists in a neutral state at pH 4.8, efficiently suppressed the formation of subvisible particles retaining a high amount of monomer owing to its higher colloidal and conformational stability. Concisely, the charged state of additives significantly impacts protein stability. This study demonstrated that contrary to popular belief, arginine and its derivatives may either enhance or suppress protein aggregation depending on their net charge and concentration.

Photoacoustic imaging of the dynamics of a dye-labeled IgG4 monoclonal antibody in subcutaneous tissue reveals a transient decrease in murine blood oxygenation under anesthesia

Significance

Over 100 monoclonal antibodies have been approved by the U.S. Food and Drug Administration (FDA) for clinical use; however, a paucity of knowledge exists regarding the injection site behavior of these formulated therapeutics, particularly the effect of antibody, formulation, and tissue at the injection site. A deeper understanding of antibody behavior at the injection site, especially on blood oxygenation through imaging, will help design improved versions of the therapeutics for a wide range of diseases.

Aim

The aim of this research is to understand the dynamics of monoclonal antibodies at the injection site as well as how the antibody itself affects the functional characteristics of the injection site [e.g., blood oxygen saturation (sO 2 )].

Approach

We employed triple-wavelength equipped functional photoacoustic imaging to study the dynamics of dye-labeled and unlabeled monoclonal antibodies at the site of injection in a mouse ear. We injected a near-infrared dye-labeled (and unlabeled) human IgG4 isotype control antibody into the subcutaneous space in mouse ears to analyze the injection site dynamics and quantify molecular movement, as well as its effect on local hemodynamics.

Results

We performed pharmacokinetic studies of the antibody in different regions of the mouse body to show that dye labeling does not alter the pharmacokinetic characteristics of the antibody and that mouse ear is a viable model for these initial studies. We explored the movement of the antibody in the interstitial space to show that the bolus area grows by ∼ 300 % over 24 h. We discovered that injection of the antibody transiently reduces the local sO 2 levels in mice after prolonged anesthesia without affecting the total hemoglobin content and oxygen extraction fraction.

Conclusions

This finding on local oxygen saturation opens a new avenue of study on the functional effects of monoclonal antibody injections. We also show the suitability of the mouse ear model to study antibody dynamics through high-resolution imaging techniques. We quantified the movement of antibodies at the injection site caused by the interstitial fluid, which could be helpful for designing antibodies with tailored absorption speeds in the future.

A biomimetic chip to assess subcutaneous bioavailability of monoclonal antibodies in humans

Subcutaneous (subQ) injection is a common route for delivering biotherapeutics, wherein pharmacokinetics is largely influenced by drug transport in a complex subQ tissue microenvironment. The selection of good drug candidates with beneficial pharmacokinetics for subQ injections is currently limited by a lack of reliable testing models. To address this limitation, we report here a Subcutaneous Co-Culture Tissue-on-a-chip for Injection Simulation (SubCuTIS). SubCuTIS possesses a 3D coculture tissue architecture, and it allows facile quantitative determination of relevant scale independent drug transport rate constants. SubCuTIS captures key in vivo physiological characteristics of the subQ tissues, and it differentiates the transport behavior of various chemically distinct molecules. We supplemented the transport measurements with theoretical modeling, which identified subtle differences in the local absorption rate constants of seven clinically available mAbs. Accounting for first-order proteolytic catabolism, we established a mathematical framework to assess clinical bioavailability using the local absorption rate constants obtained from SubCuTIS. Taken together, the technology described here broadens the applicability of organs-on-chips as a standardized and easy-to-use device for quantitative analysis of subQ drug transport.

Discovery of ABBV-154, an anti-TNF Glucocorticoid Receptor Modulator Immunology Antibody-Drug Conjugate (iADC)

Stable attachment of drug-linkers to the antibody is a critical requirement, and for maleimide conjugation to cysteine, it is achieved by ring hydrolysis of the succinimide ring. During ADC profiling in our in-house property screening funnel, we discovered that the succinimide ring open form is in equilibrium with the ring closed succinimide. Bromoacetamide (BrAc) was identified as the optimal replacement, as it affords stable attachment of the drug-linker to the antibody while completely removing the undesired ring open-closed equilibrium. Additionally, BrAc also offers multiple benefits over maleimide, especially with respect to homogeneity of the ADC structure. In combination with a short, hydrophilic linker and phosphate prodrug on the payload, this afforded a stable ADC (ABBV-154) with the desired properties to enable long-term stability to facilitate subcutaneous self-administration.

Biophysical Determinants for the Viscosity of Concentrated Monoclonal Antibody Solutions

Monoclonal antibodies (mAbs) are particularly relevant for therapeutics due to their high specificity and versatility, and mAb-based drugs are hence used to treat numerous diseases. The increased patient compliance of self-administration motivates the formulation of products for subcutaneous (SC) administration. The associated challenge is to formulate highly concentrated antibody solutions to achieve a significant therapeutic effect, while limiting their viscosity and preserving their physicochemical stability. Protein-protein interactions (PPIs) are in fact the root cause of several potential problems concerning the stability, manufacturability, and delivery of a drug product. The understanding of macroscopic viscosity requires an in-depth knowledge on protein diffusion, PPIs, and self-association/aggregation. Here, we study the self-diffusion of different mAbs of the IgG1 subtype in aqueous solution as a function of the concentration and temperature by quasi-elastic neutron scattering (QENS). QENS allows us to probe the short-time self-diffusion of the molecules and therefore to determine the hydrodynamic mAb cluster size and to gain information on the internal mAb dynamics. Small-angle neutron scattering (SANS) is jointly employed to probe structural details and to understand the nature and intensity of PPIs. Complementary information is provided by molecular dynamics (MD) simulations and viscometry, thus obtaining a comprehensive picture of mAb diffusion.

Injectable hydrogel particles for amorphous solid formulation of biologics

The fast pace of breakthroughs in cancer immunotherapy, combined with the new paradigm of moving toward high-concentration dosages and combinatorial treatments, is generating new challenges in the formulation of biologics. To address these challenges, we describe a method of formulation that enables high-concentration injectable and stable formulation of biologics as amorphous solids in aqueous suspension. This technology combines the benefits of liquid formulation with the stability of solid formulation and eliminates the need for drying and reconstitution. This widely applicable formulation integrates the amorphous solid forms of antibodies with the injectability, lubricity, and tunability of soft alginate hydrogel particles using a minimal process. The platform was evaluated for anti-PD-1 antibody pembrolizumab and human immunoglobulin G at concentrations up to 300 mg/mL with confirmed quality after release. The soft nature of the hydrogel matrix allowed packing the particles to high volume fractions.

Concentration-dependent diffusion of unlabeled protein within an in vitro hyaluronic acid matrix

Diffusion and movement of subcutaneously injected biologics and high-concentration immunoglobulin G (IgG) therapeutics away from the injection site and through the subcutaneous (SC) tissue may be concentration dependent. This possibility was confirmed by in situ measurement of diffusion coefficients of unlabeled bovine IgG in phosphate-buffered saline within an in vitro hyaluronic acid matrix that represents the SC electrostatic environment. Diffusion decreased from 2.67 to 0.05 × 10^-7  cm² /s when IgG concentration increased from 25 to 73 mg/mL. The results demonstrated that in situ detection of unlabeled proteins within an in vitro SC environment provides another useful tool for the preclinical characterization of injectable biologics.

A Perspective on Model-Informed IVIVC for Development of Subcutaneous Injectables

Subcutaneously administered drugs are growing in popularity for both large and small molecule drugs. However, development of these systems - particularly generics - is slowed due to a lack of formal guidance regarding preclinical testing and in vitro - in vivo correlations (IVIVC). Many of these methods, while appropriate for oral drugs, may not be optimized for the complex injection site physiologies, and release rate and absorption mechanisms of subcutaneous drugs. Current limitations for formulation design and IVIVC can be supported by implementing mechanistic, computational methods. These methods can help to inform drug development by identifying key drug and formulation attributes, and their effects on drug release rates. This perspective, therefore, addresses current guidelines in place for oral IVIVC development, how they may differ for subcutaneously administered compounds, and how modeling and simulation can be implemented to inform design of these products. As such, integration of modeling and simulation with current IVIVC systems can help in driving the development of subcutaneous injectables.

A safety review of current monoclonal antibodies used to treat multiple sclerosis

INTRODUCTION

Multiple sclerosis (MS) is an autoimmune disease affecting the central nervous system. Monoclonal antibodies (mAbs) have shown efficacy in reducing MS relapse rates, disease progression, and brain lesion activity.

AREAS COVERED

This article reviews the literature on the use of mAbs for the treatment of MS, including their mechanisms of action, clinical trial data, safety profiles, and long-term outcomes. The review focuses on the three main categories of mAbs used in MS: alemtuzumab, natalizumab, and anti-CD20 drugs. A literature search was conducted using relevant keywords and guidelines and reports from regulatory agencies were reviewed. The search covered studies published from inception to 31 December 202231 December 2022. The article also discusses the potential risks and benefits of these therapies, including their effects on infection rates, malignancies, and vaccination efficacy.

EXPERT OPINION

Monoclonal antibodies have revolutionized the treatment of MS, but safety concerns must be considered, particularly with regards to infection rates, malignancy risk, and vaccination efficacy. Clinicians must weigh the potential benefits and risks of mAbs on an individual patient basis, taking into account factors such as age, disease severity, and comorbidities. Ongoing monitoring and surveillance are essential to ensure the long-term safety and effectiveness of monoclonal antibody therapies in MS.

Solute Transport across the Lymphatic Vasculature in a Soft Skin Tissue

Convective transport of drug solutes in biological tissues is regulated by the interstitial fluid pressure, which plays a crucial role in drug absorption into the lymphatic system through the subcutaneous (SC) injection. In this paper, an approximate continuum poroelasticity model is developed to simulate the pressure evolution in the soft porous tissue during an SC injection. This poroelastic model mimics the deformation of the tissue by introducing the time variation of the interstitial fluid pressure. The advantage of this method lies in its computational time efficiency and simplicity, and it can accurately model the relaxation of pressure. The interstitial fluid pressure obtained using the proposed model is validated against both the analytical and the numerical solution of the poroelastic tissue model. The decreasing elasticity elongates the relaxation time of pressure, and the sensitivity of pressure relaxation to elasticity decreases with the hydraulic permeability, while the increasing porosity and permeability due to deformation alleviate the high pressure. An improved Kedem-Katchalsky model is developed to study solute transport across the lymphatic vessel network, including convection and diffusion in the multi-layered poroelastic tissue with a hybrid discrete-continuum vessel network embedded inside. At last, the effect of different structures of the lymphatic vessel network, such as fractal trees and Voronoi structure, on the lymphatic uptake is investigated. In this paper, we provide a novel and time-efficient computational model for solute transport across the lymphatic vasculature connecting the microscopic properties of the lymphatic vessel membrane to the macroscopic drug absorption.

Optimization of Drug-Linker to Enable Long-term Storage of Antibody-Drug Conjugate for Subcutaneous Dosing

To facilitate subcutaneous dosing, biotherapeutics need to exhibit properties that enable high-concentration formulation and long-term stability in the formulation buffer. For antibody-drug conjugates (ADCs), the introduction of drug-linkers can lead to increased hydrophobicity and higher levels of aggregation, which are both detrimental to the properties required for subcutaneous dosing. Herein we show how the physicochemical properties of ADCs could be controlled through the drug-linker chemistry in combination with prodrug chemistry of the payload, and how optimization of these combinations could afford ADCs with significantly improved solution stability. Key to achieving this optimization is the use of an accelerated stress test performed in a minimal formulation buffer.

Topical ocular protein delivery based on protein powder suspensions in semifluorinated alkanes

The field of ocular diseases, specifically retinal diseases is a successful target area for protein drugs with various marketed products. Besides the intraocular treatment of the retina, the topical treatment of corneal or conjunctival diseases is a promising approach. Topical ocular protein formulations face the challenges of poor penetration and potentially low stability. In this study we tested suspensions based on the semifluorinated alkane F6H8 to improve the topical ocular protein delivery. Such suspensions are well known for the increased protein stability compared to aqueous solutions. Furthermore, F6H8 is well known as vehicle for ocular delivery due to its easy spreading on the cornea. Penetration of a model mAb and its Fab fragment was tested in an ex vivo corneal penetration test. The amount of penetrated protein was increased when the protein powder suspensions were used compared to the respective aqueous solutions. Sodium caprate as penetration enhancer at 5mg/ml substantially increased the Fab fragment (7-fold) and the mAB (3-fold) concentration in the corneal tissue when applied as an aqueous solution. The effect was surprisingly more pronounced, when Fab fragment (31-fold) or mAb (13-fold) and the penetration enhancer were formulated as F6H8 suspensions. The same penetration enhancement from suspensions could be achieved with 2.5mg/ml, but the penetration was reduced compared to 2.5 mg/ml in the aqueous solution. A test based on stratified human keratinocytes did not indicate eye irritation by the tested formulations. Furthermore, stability studies for bevacizumab suspensions in semifluorinated alkanes were investigated and showed superior long-term stability compared to the marketed aqueous solution. Overall results demonstrate the high potential of topical ocular protein delivery using powder suspensions in non-aqueous vehicles based on semifluorinated alkanes.

Novel Perspectives on the Design and Development of a Long-Acting Subcutaneous Raltegravir Injection for Treatment of HIV-In Vitro and In Vivo Evaluation

Antiretrovirals (ARVs) are a highly effective therapy for treatment and prevention of HIV infection, when administered as prescribed. However, adherence to lifelong ARV regimens poses a considerable challenge and places HIV patients at risk. Long-acting ARV injections may improve patient adherence as well as maintaining long-term continuous drug exposure, resulting in improved pharmacodynamics. In the present work, we explored the aminoalkoxycarbonyloxymethyl (amino-AOCOM) ether prodrug concept as a potential approach to long-acting ARV injections. As a proof of concept, we synthesised model compounds containing the 4-carboxy-2-methyl Tokyo Green (CTG) fluorophore and assessed their stability under pH and temperature conditions that mimic those found in the subcutaneous (SC) tissue. Among them, probe 21 displayed very slow fluorophore release under SC-like conditions (98% of the fluorophore released over 15 d). Compound 25, a prodrug of the ARV agent raltegravir (RAL), was subsequently prepared and evaluated using the same conditions. This compound showed an excellent in vitro release profile, with a half-life (t_½) of 19.3 d and 82% of RAL released over 45 d. In mice, 25 extended the half-life of unmodified RAL by 4.2-fold (t_½ = 3.18 h), providing initial proof of concept of the ability of amino-AOCOM prodrugs to extend drug lifetimes in vivo. Although this effect was not as pronounced as seen in vitro-presumably due to enzymatic degradation and rapid clearance of the prodrug in vivo-the present results nevertheless pave the way for development of more metabolically stable prodrugs, to facilitate long-acting delivery of ARVs.

Role of nanotechnology in the prolonged release of drugs by the subcutaneous route

INTRODUCTION

Subcutaneous physiology is distinct from other parenteral routes that benefit the administration of prolonged-release formulations. A prolonged-release effect is particularly convenient for treating chronic diseases because it is associated with complex and often prolonged posologies. Therefore, drug-delivery systems focused on nanotechnology are proposed as alternatives that can overcome the limitations of current therapeutic regimens and improve therapeutic efficacy.

AREAS COVERED

This review presents an updated systematization of nanosystems, focusing on their applications in highly prevalent chronic diseases. Subcutaneous-delivered nanosystem-based therapies comprehensively summarize nanosystems, drugs, and diseases and their advantages, limitations, and strategies to increase their translation into clinical applications. An outline of the potential contribution of quality-by-design (QbD) and artificial intelligence (AI) to the pharmaceutical development of nanosystems is presented.

EXPERT OPINION

Although recent academic research and development (R&D) advances in the subcutaneous delivery of nanosystems have exhibited promising results, pharmaceutical industries and regulatory agencies need to catch up. The lack of standardized methodologies for analyzing in vitro data from nanosystems for subcutaneous administration and subsequent in vivo correlation limits their access to clinical trials. There is an urgent need for regulatory agencies to develop methods that faithfully mimic subcutaneous administration and specific guidelines for evaluating nanosystems.

Accelerating therapeutic protein design with computational approaches toward the clinical stage

Therapeutic protein, represented by antibodies, is of increasing interest in human medicine. However, clinical translation of therapeutic protein is still largely hindered by different aspects of developability, including affinity and selectivity, stability and aggregation prevention, solubility and viscosity reduction, and deimmunization. Conventional optimization of the developability with widely used methods, like display technologies and library screening approaches, is a time and cost-intensive endeavor, and the efficiency in finding suitable solutions is still not enough to meet clinical needs. In recent years, the accelerated advancement of computational methodologies has ushered in a transformative era in the field of therapeutic protein design. Owing to their remarkable capabilities in feature extraction and modeling, the integration of cutting-edge computational strategies with conventional techniques presents a promising avenue to accelerate the progression of therapeutic protein design and optimization toward clinical implementation. Here, we compared the differences between therapeutic protein and small molecules in developability and provided an overview of the computational approaches applicable to the design or optimization of therapeutic protein in several developability issues.

Pharmacokinetics and Pharmacodynamics of Antibody-Drug Conjugates Administered via Subcutaneous and Intratumoral Routes

We hypothesize that different routes of administration may lead to altered pharmacokinetics/pharmacodynamics (PK/PD) behavior of antibody-drug conjugates (ADCs) and may help to improve their therapeutic index. To evaluate this hypothesis, here we performed PK/PD evaluation for an ADC administered via subcutaneous (SC) and intratumoral (IT) routes. Trastuzumab-vc-MMAE was used as the model ADC, and NCI-N87 tumor-bearing xenografts were used as the animal model. The PK of multiple ADC analytes in plasma and tumors, and the in vivo efficacy of ADC, after IV, SC, and IT administration were evaluated. A semi-mechanistic PK/PD model was developed to characterize all the PK/PD data simultaneously. In addition, local toxicity of SC-administered ADC was investigated in immunocompetent and immunodeficient mice. Intratumoral administration was found to significantly increase tumor exposure and anti-tumor activity of ADC. The PK/PD model suggested that the IT route may provide the same efficacy as the IV route at an increased dosing interval and reduced dose level. SC administration of ADC led to local toxicity and reduced efficacy, suggesting difficulty in switching from IV to SC route for some ADCs. As such, this manuscript provides unprecedented insight into the PK/PD behavior of ADCs after IT and SC administration and paves the way for clinical evaluation of these routes.

Predicting Human Bioavailability of Subcutaneously Administered Fusion Proteins and Monoclonal Antibodies Using Human Intravenous Clearance or Antibody Isoelectric Point

There has been an increasing trend towards subcutaneous (SC) delivery of fusion proteins and monoclonal antibodies (mAbs) in recent years versus intravenous (IV) administration. The prediction of bioavailability is one of the major barriers in clinical translation of SC-administered therapeutic proteins due to a lack of reliable in vitro and preclinical in vivo predictive models. In this study, we explored the relationships between human SC bioavailability and physicochemical or pharmacokinetic properties of 19 Fc- or albumin-fusion proteins and 98 monoclonal antibodies. An inverse linear correlation was observed between human SC bioavailability and intravenous clearance (CL) or isoelectric point (pI). Multivariate regression models were developed using intravenous CL and pI of a training set (N = 59) as independent variables. The predictive models of mAbs were validated with an independent test set (N = 33). Two linear regression models resulted in 24 (73%) and 27 (82%) among 33 predictions within 0.8- to 1.2-fold deviations. Due to the small sample size of dataset, regression model validation was not conducted for fusion proteins. Overall, this study demonstrated that CL- and pI-based multivariate regression models could be used to predict human SC bioavailability of mAbs.

Subcutaneous delivery of an antibody against SARS-CoV-2 from a supramolecular hydrogel depot

Prolonged maintenance of therapeutically-relevant levels of broadly neutralizing antibodies (bnAbs) is necessary to enable passive immunization against infectious disease. Unfortunately, protection only lasts for as long as these bnAbs remain present at a sufficiently high concentration in the body. Poor pharmacokinetics and burdensome administration are two challenges that need to be addressed in order to make pre- and post-exposure prophylaxis with bnAbs feasible and effective. In this work, we develop a supramolecular hydrogel as an injectable, subcutaneous depot to encapsulate and deliver antibody drug cargo. This polymer-nanoparticle (PNP) hydrogel exhibits shear-thinning and self-healing properties that are required for an injectable drug delivery vehicle. In vitro drug release assays and diffusion measurements indicate that the PNP hydrogels prevent burst release and slow the release of encapsulated antibodies. Delivery of bnAbs against SARS-CoV-2 from PNP hydrogels is compared to standard routes of administration in a preclinical mouse model. We develop a multi-compartment model to understand the ability of these subcutaneous depot materials to modulate the pharmacokinetics of released antibodies; the model is extrapolated to explore the requirements needed for novel materials to successfully deliver relevant antibody therapeutics with different pharmacokinetic characteristics.

Pharmacokinetic characterization, benefits and barriers of subcutaneous administration of monoclonal antibodies in oncology

OBJECTIVE

Therapeutic monoclonal antibodies in oncology are slowly becoming the dominant treatment option for many different cancer types. The main route of administration, infusion, requires extensive product preparations, patient hospitalization and close monitoring. Patient comfort improvement, staff workload reduction and cost savings dictated the development of subcutaneous formulations. The aim of this review is to present pharmacokinetic characteristics of subcutaneous products, discuss the differences between intravenous and subcutaneous routes and to point out the advantages as well as challenges of administration route shift from the formulation development and pharmacometric angle.

DATA SOURCES

Food and Drug administration's Purple book database and electronic medicines compendium were used to identify monoclonal antibodies in oncology approved as subcutaneous forms. Using keywords subcutaneous, monoclonal antibodies, pharmacokinetics, model, as well as specific drugs previously identified, both PubMed and ScienceDirect databases were researched.

DATA SUMMARY

There are currently six approved subcutaneous onco-monoclonal antibodies on the market. For each of them, exposure to the drug was similar in relation to infusion, treatment effectiveness was the same, administration was well tolerated by the patients and costs of the medical service were reduced.

CONCLUSION

Development of subcutaneous forms for existing and emerging new monoclonal antibodies for cancer treatment as well as shifting from administration via infusion should be encouraged due to patient preference, lower costs and overall lack of substantial differences in efficacy and safety between the two routes.

Prediction of subcutaneous drug absorption - characterization of subcutaneous interstitial fluids as a basis for developing biorelevant in vitro models

Unlike orally administered drugs, the absorption profile of subcutaneously injectable drugs in humans is difficult to predict from preclinical studies. Since the subcutaneous interstitial fluid (ISF) is the first fluid interacting with the administered formulation before the respective drug is absorbed, it could critically affect bioavailability. The aim of the present study was to gain a better understanding of the similarities and differences of ISF of different species. For this purpose, ISF was isolated from subcutaneous tissues of five preclinical animal species, i.e., mice, rats, minipig, landrace pig, non-human primates, and humans, using a centrifugation method, and characterized with respect to its major constituents and physicochemical properties. The results show trends between animal species, with ISF from non-human primates differing significantly from that of the other preclinical species for most parameters analyzed and showing similarities to ISF of human origin. Although from a statistical point of view it will be necessary to further increase the existing data sets, the presented data provide valuable information for the development of biorelevant in vitro models to predict the in vivo performance of subcutaneously administered formulations, as they provide fundamental information for the design of biorelevant ISF media for both preclinical species and humans.

An Intercompany Perspective on Practical Experiences of Predicting, Optimizing and Analyzing High Concentration Biologic Therapeutic Formulations

Developing high-dose biologic drugs for subcutaneous injection often requires high-concentration formulations and optimizing viscosity, solubility, and stability while overcoming analytical, manufacturing, and administration challenges. To understand industry approaches for developing high-concentration formulations, the Formulation Workstream of the BioPhorum Development Group, an industry-wide consortium, conducted an inter-company collaborative exercise which included several surveys. This collaboration provided an industry perspective, experience, and insight into the practicalities for developing high-concentration biologics. To understand solubility and viscosity, companies desire predictive tools, but experience indicates that these are not reliable and experimental strategies are best. Similarly, most companies prefer accelerated and stress stability studies to in-silico or biophysical-based prediction methods to assess aggregation. In addition, optimization of primary container-closure and devices are pursued to mitigate challenges associated with high viscosity of the formulation. Formulation strategies including excipient selection and application of studies at low concentration to high-concentration formulations are reported. Finally, analytical approaches to high concentration formulations are presented. The survey suggests that although prediction of viscosity, solubility, and long-term stability is desirable, the outcome can be inconsistent and molecule dependent. Significant experimental studies are required to confirm robust product definition as modeling at low protein concentrations will not necessarily extrapolate to high concentration formulations.

Lymphatic uptake of biotherapeutics through a 3D hybrid discrete-continuum vessel network in the skin tissue

Subcutaneous administration is a common approach for the delivery of biotherapeutics, which is achieved mainly through the absorption across lymphatic vessels. In this paper, the drug transport and lymphatic uptake through a three-dimensional hybrid discrete-continuum vessel network in the skin tissue are investigated through high-fidelity numerical simulations. We find that the local lymphatic uptake through the explicit vessels significantly affects macroscopic drug absorption. The diffusion of drug solute through the explicit vessel network affects the lymphatic uptake after the injection. This effect, however, cannot be captured using previously developed continuum models. The lymphatic uptake is dominated by the convection due to lymphatic drainage driven by the pressure difference, which is rarely studied in experiments and simulations. Furthermore, the effects of injection volume and depth on the lymphatic uptake are investigated in a multi-layered domain. We find that the injection volume significantly affects the rate of lymphatic uptake through the heterogeneous vessel network, while the injection depth has little influence, which is consistent with the experimental results. At last, the binding and metabolism of drug molecules are studied to bridge the simulations to the drug clearance experients. We provide a new approach to study the diffusion and convection of drug molecules into the lymphatic system through the hybrid vessel network.

Random Heteropolymer Excipients Improve the Colloidal Stability of a Monoclonal Antibody for Subcutaneous Administration

PURPOSE

Developing stable high concentration monoclonal antibody (mAb) formulations is increasingly important to move toward subcutaneous (SC) administration for better patient experience. Challenges stemming from protein-protein interactions in these crowded solutions, such as colloidal instability, limit the feasibility of some formulations because of concerns of safety, product quality, and/or manufacturability. Herein, we report novel random heteropolymer excipients that improve the colloidal stability of a high concentration mAb formulation for SC administration.

METHODS

A library of polymers was synthesized and screened by a high-throughput, absorbance-based assay. The lead polymers were selected and characterized for their ability to alter the precipitation kinetics of a mAb in physiologically relevant conditions using two model systems.

RESULTS

Biophysical testing via surface tension measurements, isothermal titration calorimetry (ITC), microscale thermophoresis (MST), and intrinsic fluorescence quenching indicated that the polymers delayed onset of mAb precipitation from a combination of surfactant behaviour and interactions with the protein to prevent protein-protein interactions leading to colloidal instability.

CONCLUSIONS

The random heteropolymers described are a new class of excipients that may enable development of SC mAb formulations previously inaccessible to patients.

Understanding patient preferences for handheld autoinjectors versus wearable large-volume injectors

OBJECTIVE

While interest in the use of wearable large-volume injectors for subcutaneous drug delivery is increasing, it remains unclear whether and under what conditions these emerging dosing options are preferred over more frequent but shorter administration of smaller doses using handheld autoinjectors. Therefore, the objective of this study was to examine the characteristics of patients diagnosed with cancer, diabetes, inflammatory and cardiovascular diseases, and treatment attributes that determine device preferences.

METHODS

Based on a cross-sectional online choice experiment, 191 participants expressed their preferences without being physically exposed to the devices or performing injections. Logistic hierarchical regression models were used to assess which patient characteristics, and how changes in treatment attributes, drive device preferences.

RESULTS

Participant quality of life reduced the likelihood of preferring wearable large-volume injectors to handheld autoinjectors. Moreover, reducing injection frequency from biweekly to monthly to quarterly injections, and shortening injection duration from 33 to 8 min, significantly increased the likelihood of patients preferring large-volume injectors to autoinjectors (p < 0.001).

CONCLUSION

The study revealed patient quality of life as predictor of device preference and identified critical inflection points in injection duration and injection frequency, at which patient preferences shift from handheld autoinjectors to wearable large-volume injectors.

Leading Edge: Intratumor Delivery of Monoclonal Antibodies for the Treatment of Solid Tumors

Immunotherapies based on immune checkpoint blockade have shown remarkable clinical outcomes and durable responses in patients with many tumor types. Nevertheless, these therapies lack efficacy in most cancer patients, even causing severe adverse events in a small subset of patients, such as inflammatory disorders and hyper-progressive disease. To diminish the risk of developing serious toxicities, intratumor delivery of monoclonal antibodies could be a solution. Encouraging results have been shown in both preclinical and clinical studies. Thus, intratumor immunotherapy as a new strategy may retain efficacy while increasing safety. This approach is still an exploratory frontier in cancer research and opens up new possibilities for next-generation personalized medicine. Local intratumor delivery can be achieved through many means, but an attractive approach is the use of gene therapy vectors expressing mAbs inside the tumor mass. Here, we summarize basic, translational, and clinical results of intratumor mAb delivery, together with descriptions of non-viral and viral strategies for mAb delivery in preclinical and clinical development. Currently, this is an expanding research subject that will surely play a key role in the future of oncology.

Stable High-Concentration Monoclonal Antibody Formulations Enabled by an Amphiphilic Copolymer Excipient

Monoclonal antibodies are a staple in modern pharmacotherapy. Unfortunately, these biopharmaceuticals are limited by their tendency to aggregate in formulation, resulting in poor stability and often requiring low concentration drug formulations. Moreover, existing excipients designed to stabilize these formulations are often limited by their toxicity and tendency to form particles such as micelles. Here, we demonstrate the ability of a simple "drop-in", amphiphilic copolymer excipient to enhance the stability of high concentration formulations of clinically-relevant monoclonal antibodies without altering their pharmacokinetics or injectability. Through interfacial rheology and surface tension measurements, we demonstrate that the copolymer excipient competitively adsorbs to formulation interfaces. Further, through determination of monomeric composition and retained bioactivity through stressed aging, we show that this excipient confers a significant stability benefit to high concentration antibody formulations. Finally, we demonstrate that the excipient behaves as an inactive ingredient, having no significant impact on the pharmacokinetic profile of a clinically relevant antibody in mice. This amphiphilic copolymer excipient demonstrates promise as a simple formulation additive to create stable, high concentration antibody formulations, thereby enabling improved treatment options such as a route-of-administration switch from low concentration intravenous (IV) to high concentration subcutaneous (SC) delivery while reducing dependence on the cold chain.

Monoclonal antibody and protein therapeutic formulations for subcutaneous delivery: high-concentration, low-volume vs. low-concentration, high-volume

Biologic drugs are used to treat a variety of cancers and chronic diseases. While most of these treatments are administered intravenously by trained healthcare professionals, a noticeable trend has emerged favoring subcutaneous (SC) administration. SC administration of biologics poses several challenges. Biologic drugs often require higher doses for optimal efficacy, surpassing the low volume capacity of traditional SC delivery methods like autoinjectors. Consequently, high concentrations of active ingredients are needed, creating time-consuming formulation obstacles. Alternatives to traditional SC delivery systems are therefore needed to support higher-volume biologic formulations and to reduce development time and other risks associated with high-concentration biologic formulations. Here, we outline key considerations for SC biologic drug formulations and delivery and explore a paradigm shift: the flexibility afforded by low-to-moderate-concentration drugs in high-volume formulations as an alternative to the traditionally difficult approach of high-concentration, low-volume SC formulation delivery.

A systematic review of commercial high concentration antibody drug products approved in the US: formulation composition, dosage form design and primary packaging considerations

Three critical aspects that define high concentration antibody products (HCAPs) are as follows: 1) formulation composition, 2) dosage form, and 3) primary packaging configuration. HCAPs have become successful in the therapeutic sector due to their unique advantage of allowing subcutaneous self-administration. Technical challenges, such as physical and chemical instability, viscosity, delivery volume limitations, and product immunogenicity, can hinder successful development and commercialization of HCAPs. Such challenges can be overcome by robust formulation and process development strategies, as well as rational selection of excipients and packaging components. We compiled and analyzed data from US Food and Drug Administration-approved and marketed HCAPs that are ≥100 mg/mL to identify trends in formulation composition and quality target product profile. This review presents our findings and discusses novel formulation and processing technologies that enable the development of improved HCAPs at ≥200 mg/mL. The observed trends can be used as a guide for further advancements in the development of HCAPs as more complex antibody-based modalities enter biologics product development.

Monoclonal Antibody Pharmacokinetics in Cynomolgus Monkeys Following Subcutaneous Administration: Physiologically Based Model Predictions from Physiochemical Properties

An integrated physiologically based modeling framework is presented for predicting pharmacokinetics and bioavailability of subcutaneously administered monoclonal antibodies in cynomolgus monkeys, based on in silico structure-derived metrics characterizing antibody size, overall charge, local charge, and hydrophobicity. The model accounts for antibody-specific differences in pinocytosis, transcapillary transport, local lymphatic uptake, and pre-systemic degradation at the subcutaneous injection site and reliably predicts the pharmacokinetics of five different wild-type mAbs and their Fc variants following intravenous and subcutaneous administration. Significant associations were found between subcutaneous injection site degradation rate and the antibody's local positive charge of its complementarity-determining region (R = 0.56, p = 0.0012), antibody pinocytosis rate and its overall positive charge (R = 0.59, p = 0.00063), and antibody paracellular transport and its overall charge together with hydrophobicity (R = 0.63, p = 0.00096). Based on these results, population simulations were performed to predict the relationship between bioavailability and antibody local positive charge. In addition, model simulations were conducted to calculate the relative contribution of absorption pathways (lymphatic and blood), pre-systemic degradation pathways (interstitial and lysosomal), and the influence of injection site lymph flow on antibody bioavailability and pharmacokinetics. The proposed physiologically based modeling framework integrates fundamental mechanisms governing antibody subcutaneous absorption and disposition, with structured-based physiochemical properties, to predict antibody bioavailability and pharmacokinetics in vivo.

Advanced Formulations/Drug Delivery Systems for Subcutaneous Delivery of Protein-Based Biotherapeutics

Multiple advanced formulations and drug delivery systems (DDSs) have been developed to deliver protein-based biotherapeutics via the subcutaneous (SC) route. These formulations/DDSs include high-concentration solution, co-formulation of two or more proteins, large volume injection, protein cluster/complex, suspension, nanoparticle, microparticle, and hydrogel. These advanced systems provide clinical benefits related to efficacy and safety, but meanwhile, have more complicated formulations and manufacturing processes compared to conventional solution formulations. To develop a fit-for-purpose formulation/DDS for SC delivery, scientists need to consider multiple factors, such as the primary indication, targeted site, immunogenicity, compatibility, biopharmaceutics, patient compliance, etc. Next, they need to develop appropriate formulation (s) and manufacturing processes using the QbD principle and have a control strategy. This paper aims to provide a comprehensive review of advanced formulations/DDSs recently developed for SC delivery of proteins, as well as some knowledge gaps and potential strategies to narrow them through future research.

Development of an In Vitro System To Emulate an In Vivo Subcutaneous Environment: Small Molecule Drug Assessment

A reliable in vitro system can support and guide the development of subcutaneous (SC) drug products. Although several in vitro systems have been developed, they have some limitations, which may hinder them from getting more engaged in SC drug product development. This study sought to develop a novel in vitro system, namely, Emulator of SubCutaneous Absorption and Release (ESCAR), to better emulate the in vivo SC environment and predict the fate of drugs in SC delivery. ESCAR was designed using computer-aided design (CAD) software and fabricated using the three-dimensional (3D) printing technique. ESCAR has a design of two acceptor chambers representing the blood uptake pathway and the lymphatic uptake pathway, respectively, although only the blood uptake pathway was investigated for small molecules in this study. Via conducting a DoE factor screening study using acetaminophen solution, the relationship of the output (drug release from the "SC" chamber to the "blood circulation" chamber) and the input parameters could be modeled using a variety of methods, including polynomial equations, machine learning methods, and Monte Carlo simulation-based methods. The results suggested that the hyaluronic acid (HA) concentration was a critical parameter, whereas the influence of the injection volume and injection position was not substantial. An in vitro-in vivo correlation (IVIVC) study was developed using griseofulvin suspension to explore the feasibility of applying ESCAR in formulation development and bioequivalence studies. The developed LEVEL A IVIVC model demonstrated that the in vivo PK profile could be correlated with the in vitro release profile. Therefore, using this model, for new formulations, only in vitro studies need to be conducted in ESCAR, and in vivo studies might be waived. In conclusion, ESCAR had important implications for research and development and quality control of SC drug products. Future work would be focused on further optimizing ESCAR and expanding its applications via assessing more types of molecules and formulations.

Technology development to evaluate the effectiveness of viscosity reducing excipients

Addition of pharmaceutical excipients is a commonly used approach to decrease the viscosity of highly concentrated protein formulations, which otherwise could not be subcutaneously injected or processed. The variety of protein-protein interactions, which are responsible for increased viscosities, makes a portfolio approach necessary. Screening of several excipients to develop such a portfolio is time and money consuming in industrial settings. Responsible protein-protein interactions were investigated using the interaction parameter k_D obtained from dynamic light scattering measurements in the studies presented herein. Together with in-silico calculated excipient parameter, k_D could be used as a screening tool accelerating screening and formulation development as k_D is suitable to high-throughput formats using small quantities of protein and low concentrations. A qualitative correlation between k_D and high-concentration viscosity behavior could be shown in our case.

Application of physiologically-based pharmacokinetic models for therapeutic proteins and other novel modalities

The past two decades have seen diversification of drug development pipelines and approvals from traditional small molecule therapies to alternative modalities including monoclonal antibodies, engineered proteins, antibody drug conjugates (ADCs), oligonucleotides and gene therapies. At the same time, physiologically-based pharmacokinetic (PBPK) models for small molecules have seen increased industry and regulatory acceptance.This review focusses on the current status of the application of PBPK models to these newer modalities and give a perspective on the successes, challenges and future directions of this field.There is greatest experience in the development of PBPK models for therapeutic proteins, and PBPK models for ADCs benefit from prior experience for both therapeutic proteins and small molecules. For other modalities, the application of PBPK models is in its infancy.Challenges are discussed and a common theme is lack of availability of physiological and experimental data to characterise systems and drug parameters to enable a priori prediction of pharmacokinetics. Furthermore, sufficient clinical data are required to build confidence in developed models.The PBPK modelling approach provides a quantitative framework for integrating knowledge and data from multiple sources and can be built on as more data becomes available.

Responsive Hyaluronic Acid–Ethylacrylamide Microgels Fabricated Using Microfluidics Technique

Volume changes of responsive microgels can probe interactions between polyelectrolytes and species of opposite charges such as peptides and proteins. We have investigated a microfluidics method to synthesize highly responsive, covalently crosslinked, hyaluronic acid microgels for such purposes. Sodium hyaluronate (HA), pre-modified with ethylacrylamide functionalities, was crosslinked in aqueous droplets created with a microfluidic technique. We varied the microgel properties by changing the degree of modification and concentration of HA in the reaction mixture. The degree of modification was determined by 1H NMR. Light microscopy was used to investigate the responsiveness of the microgels to osmotic stress in aqueous saline solutions by simultaneously monitoring individual microgel species in hydrodynamic traps. The permeability of the microgels to FITC-dextrans of molecular weights between 4 and 250 kDa was investigated using confocal laser scanning microscopy. The results show that the microgels were spherical with diameters between 100 and 500 µm and the responsivity tunable by changing the degree of modification and the HA concentration. Microgels were fully permeable to all investigated FITC-dextran probes. The partitioning to the microgel from an aqueous solution decreased with the increasing molecular weight of the probe, which is in qualitative agreement with theories of homogeneous gel networks.

An overview of biomedical applications of choline geranate (CAGE): a major breakthrough in drug delivery

A number of studies are on the way to advancing the field of biomedical sciences using ionic liquids (ILs) and deep eutectic solvents (DESs) in view of their unique properties and inherent tunability. These significant solvents tend to enhance the physical properties of the drug, increase their bioavailability and promote the delivery of recalcitrant drugs to the body. One such widely investigated tempting multipurpose IL/DES system is choline geranate (CAGE), which has gained significant interest due to its biocompatible and highly potent antiseptic behavior, which also facilitates its sanitizing ability to combat the coronavirus. This review focuses on total advancements in biomedical applications of CAGE. This biocompatible IL/DES has made facile the solubilization of hydrophobic and hydrophilic drugs and delivery of intractable drugs through physiological barriers by stabilizing proteins and nucleic acids. Therefore, it has been used as a transdermal, subcutaneous, and oral delivery carrier and as an antimicrobial agent to treat infectious diseases and wounds as approved by laboratory and clinical translations. Moreover, current challenges and future outlooks are also highlighted to explore them more purposefully.

Nanomedicine and versatile therapies for cancer treatment

The higher prevalence of cancer is related to high rates of mortality and morbidity worldwide. By virtue of the properties of matter at the nanoscale, nanomedicine is proven to be a powerful tool to develop innovative drug carriers with greater efficacies and fewer side effects than conventional therapies. In this review, different nanocarriers for controlled drug release and their routes of administration have been discussed in detail, especially for cancer treatment. Special emphasis has been given on the design of drug delivery vehicles for sustained release and specific application methods for targeted delivery to the affected areas. Different polymeric vehicles designed for the delivery of chemotherapeutics have been discussed, including graft copolymers, liposomes, hydrogels, dendrimers, micelles, and nanoparticles. Furthermore, the effect of dimensional properties on chemotherapy is vividly described. Another integral section of the review focuses on the modes of administration of nanomedicines and emerging therapies, such as photothermal, photodynamic, immunotherapy, chemodynamic, and gas therapy, for cancer treatment. The properties, therapeutic value, advantages, and limitations of these nanomedicines are highlighted, with a focus on their increased performance versus conventional molecular anticancer therapies.

Real-world experience of switching from intravenous to subcutaneous vedolizumab maintenance treatment for inflammatory bowel diseases

BACKGROUND

Subcutaneous (SC) vedolizumab is effective in inflammatory bowel diseases (IBD) when administered after induction with two infusions.

AIM

To assess the effectiveness, safety and pharmacokinetics of a switch from intravenous (IV) to SC maintenance vedolizumab in patients with IBD METHODS: In this prospective cohort study, patients with IBD who had ≥4 months IV vedolizumab were switched to SC vedolizumab. We studied the time to discontinuation of SC vedolizumab, adverse events (AEs), changes in clinical and biochemical outcomes and vedolizumab concentrations at baseline, and weeks 12 and 24.

RESULTS

We included 82 patients with Crohn's disease (CD) and 53 with ulcerative colitis (UC). Eleven (13.4%) patients with CD and five (9.4%) with UC discontinued SC vedolizumab after a median of 18 (IQR 8-22) and 6 weeks (IQR 5-10), respectively. Four patients with CD switched to a different drug due to loss of response, nine switched back to IV vedolizumab due to adverse events, and three due to needle fear. Common AEs were injection site reactions (n = 15) and headache (n = 6). Median clinical and biochemical disease activity remained stable after the switch. Median serum vedolizumab concentrations increased from 19 μg/ml at the time of the switch to 31 μg/ml 12 weeks after the switch (p < 0.005).

CONCLUSIONS

Switching from IV to SC vedolizumab maintenance treatment is effective in patients with CD or UC. However, 9% of patients were switched back to IV vedolizumab due to adverse events or fear of needles.