Effects of hypertonic buffer composition on lymph node uptake and bioavailability of rituximab, after subcutaneous administration

Comparison of efficacy between subcutaneous and intravenous application of moss-aGal in the mouse model of Fabry disease

Fabry disease (FD, OMIM 301500) is a rare X-linked inherited lysosomal storage disorder associated with reduced activities of α-galactosidase A (aGal, EC 3.2.1.22). The current standard of care for FD is based on enzyme replacement therapy (ERT), in which a recombinantly produced version of αGal is intravenously (iv) applied to Fabry patients in biweekly intervals. Though the iv application is clinically efficacious, periodical infusions are inconvenient, time- and resource-consuming and they negatively impact the patients' quality of life. Subcutaneous (sc) injection, in contrast, is an established route of administration for treatment of chronic conditions. It opens the beneficial option of self-administration, thereby improving patients' quality of life and at the same time reducing treatment costs. We have previously shown that Moss-α-Galactosidase (moss-aGal), recombinantly produced in the moss Physcomitrium patens, is efficient in degrading accumulated Gb3 in target organs of murine model of FD and in the phase I clinical study, we obtained first efficacy evidence in human patients following single iv infusion. Here, we tested the efficacy of subcutaneous administration of moss-aGal and compared it with the results observed following iv infusion in Fabry mice. The obtained findings demonstrate that subcutaneously applied moss-aGal is correctly transported to target organs and efficacious in degrading Gb3 deposits there and thus suggest the possibility of using this route of administration for therapy of Fabry disease.

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.

Morphological, Mechanical and Hydrodynamic Aspects of Diaphragmatic Lymphatics

The diaphragmatic lymphatic vascular network has unique anatomical characteristics. Studying the morphology and distribution of the lymphatic network in the mouse diaphragm by fluorescence-immunohistochemistry using LYVE-1 (a lymphatic endothelial marker) revealed LYVE1⁺ structures on both sides of the diaphragm-both in its the muscular and tendinous portion, but with different vessel density and configurations. On the pleural side, most LYVE1⁺ configurations are vessel-like with scanty stomata, while the peritoneal side is characterized by abundant LYVE1⁺ flattened lacy-ladder shaped structures with several stomata-like pores, particularly in the muscular portion. Such a complex, three-dimensional organization is enriched, at the peripheral rim of the muscular diaphragm, with spontaneously contracting lymphatic vessel segments able to prompt contractile waves to adjacent collecting lymphatics. This review aims at describing how the external tissue forces developing in the diaphragm, along with cyclic cardiogenic and respiratory swings, interplay with the spontaneous contraction of lymphatic vessel segments at the peripheral diaphragmatic rim to simultaneously set and modulate lymph flow from the pleural and peritoneal cavities. These details may provide useful in understanding the role of diaphragmatic lymphatics not only in physiological but, more so, in pathophysiological circumstances such as in dialysis, metastasis or infection.

A Two-Pore Physiologically Based Pharmacokinetic Model to Predict Subcutaneously Administered Different-Size Antibody/Antibody Fragments

Quantitative modeling of the subcutaneous absorption processes of protein therapeutics is challenging. Here we have proposed a "two-pore" PBPK model that is able to simultaneously characterize plasma PK of different-size protein therapeutics in mice. The skin compartment is evolved to mechanistically account for the absorption pathways through lymph and blood capillaries, as well as local degradation at the SC injection site. The model is developed using in-house plasma PK data generated following subcutaneous administration of 6 different-size protein therapeutics (13-150 kDa) in mice. The model was able to capture plasma PK of all molecules following intravenous and subcutaneous administration relatively well. From the observed plasma PK profiles, as well as from the model simulation result, several important PK descriptors were found to be dependent on protein size for FcRn nonbinding molecules. A positive correlation was found between T_max and protein size. A "U" shape relationship was found between C_max and protein size. Negative correlations were observed between bioavailability (F) and local degradation rate (k_deg,SC), and F and protein size. Pathway analysis of the model was conducted for the subcutaneous absorption process, and continuous relationships were established between the percentage of absorption through lymphatic and vascular pathways and protein size. This PBPK model could serve as a platform for the development of different-size protein therapeutics and will be scaled up to humans for translational studies in the future.

Machine Learning Attempts for Predicting Human Subcutaneous Bioavailability of Monoclonal Antibodies

PURPOSE

One knowledge gap related to subcutaneous (SC) delivery is unpredictable and variable bioavailability. This study was aimed to develop machine learning methods to predict whether mAb's bioavailability was ≥70% or below, without completely knowing the mechanism and causality between inputs and outputs.

METHODS

A database of mAb SC products was built. The model training and validation were accomplished based on this database and a set of the inputs (product properties) were mapped to the output (bioavailability) using different machine learning algorithms. Dimensionality reduction was undertaken using principal component analysis (PCA).

RESULTS

The bioavailability of the mAb products being investigated varied from 35% to 90%. The tree-based methods, including random forest (RF), Adaptive Boost (AdaBoost), and decision tree (DT) presented the best predictability and generalization power on bioavailability classification. The models based on Multi-layer perceptron (MLP), Gaussian Naïve Bayes (GaussianNB), and k nearest neighbor (kNN) algorithms also provided acceptable prediction accuracy.

CONCLUSION

Machine learning could be a potential tool to predict mAb's bioavailability. Since all input features were acquired using theoretical calculations and predictions rather than experiments, the models may be particularly applicable to some early-stage research activities such as mAb molecule triage, design/optimization, mutant screening, molecule selection, and formulation design.

Predicting bioavailability of monoclonal antibodies after subcutaneous administration: Open innovation challenge

Despite the increasing trend towards subcutaneous delivery of monoclonal antibodies, factors influencing the subcutaneous bioavailability of these molecules remain poorly understood. To address critical knowledge gaps and issues during development of subcutaneous dosage forms for monoclonal antibodies, the Subcutaneous Drug Delivery and Development Consortium was convened in 2018 as a pre-competitive collaboration of recognized industry experts. One of the Consortium's eight problem statements highlights the challenges of predicting human bioavailability of subcutaneously administered monoclonal antibodies due to a lack of reliable in vitro and preclinical in vivo predictive models. In this paper, we assess the current landscape in subcutaneous bioavailability prediction for monoclonal antibodies and discuss the gaps and opportunities associated with bioavailability models for biotherapeutics. We also issue an open challenge to industry and academia, encouraging the development of reliable models to enable subcutaneous bioavailability prediction of therapeutic large molecules in humans and improve translation from preclinical species.

A drug delivery perspective on intratumoral-immunotherapy in renal cell carcinoma

In less than 5years immune checkpoint inhibitors (ICI) went from first FDA approval to become first-line options in advanced renal cell carcinoma. Despite that many patients have benefited from ICI, a significant fraction of individuals are refractory to these new immunological treatments. In this review, we discussed using intratumoral (i.t.) route of drug administration as an alternative to systemic therapy to increase the response rates and to circumvent potential drug-induced systemic adverse events. We provided a historic account of i.t. drug treatments in cancer and reviewed the contemporary experience in local drug delivery. We discussed the potential for enhancing the therapeutic impact of ICI by leveraging hydrogels as drug delivery vehicles and presented an outlook for implementing i.t. in renal cell carcinoma.

Proteolysis and Oxidation of Therapeutic Proteins After Intradermal or Subcutaneous Administration

The intradermal (ID) and subcutaneous (SC) routes are commonly used for therapeutic proteins (TPs) and vaccines; however, the bioavailability of TPs is typically less than small molecule drugs given via the same routes. Proteolytic enzymes in the dermal, SC, and lymphatic tissues may be responsible for the loss of TPs. In addition, the TPs may be exposed to reactive oxygen species generated in the SC tissue and the lymphatic system in response to injection-related trauma and impurities within the formulation. The reactive oxygen species can oxidize TPs to alter their efficacy and immunogenicity potential. Mechanistic understandings of the dominant proteolysis and oxidative routes are useful in the drug discovery process, formulation development, and to assess the potential for immunogenicity and altered pharmacokinetics (PK). Furthermore, in vitro tools representing the ID or SC and lymphatic system can be used to evaluate the extent of proteolysis of the TPs after the injection and before systemic entry. The in vitro clearance data may be included in physiologically based pharmacokinetic models for improved PK predictions. In this review, we have summarized various physiological factors responsible for proteolysis and oxidation of TPs after ID and SC administration.

Understanding Inter-Individual Variability in Monoclonal Antibody Disposition

Monoclonal antibodies (mAbs) are currently the largest and most dominant class of therapeutic proteins. Inter-individual variability has been observed for several mAbs; however, an understanding of the underlying mechanisms and factors contributing to inter-subject differences in mAb disposition is still lacking. In this review, we analyze the mechanisms of antibody disposition and the putative mechanistic determinants of inter-individual variability. Results from in vitro, preclinical, and clinical studies were reviewed evaluate the role of the neonatal Fc receptor and Fc gamma receptors (expression and polymorphism), target properties (expression, shedding, turnover, internalization, heterogeneity, polymorphism), and the influence of anti-drug antibodies. Particular attention is given to the influence of co-administered drugs and disease, and to the physiological relevance of covariates identified by population pharmacokinetic modeling, as determinants of variability in mAb pharmacokinetics.

Pharmacokinetic and Pharmacodynamic Properties of Drug Delivery Systems

The use of drug delivery systems (DDS) is an attractive approach to facilitate uptake of therapeutic agents at the desired site of action, particularly when free drug has poor pharmacokinetics/biodistribution (PK/BD) or significant off-site toxicities. Successful translation of DDS into the clinic is dependent on a thorough understanding of the in vivo behavior of the carrier, which has, for the most part, been an elusive goal. This is, at least in part, due to significant differences in the mechanisms controlling pharmacokinetics for classic drugs and DDSs. In this review, we summarize the key physiologic mechanisms controlling the in vivo behavior of DDS, compare and contrast this with classic drugs, and describe engineering strategies designed to improve DDS PK/BD. In addition, we describe quantitative approaches that could be useful for describing PK/BD of DDS, as well as critical steps between tissue uptake and pharmacologic effect.

Fluid Osmolarity Acutely and Differentially Modulates Lymphatic Vessels Intrinsic Contractions and Lymph Flow

Lymph formation and propulsion rely on an extrinsic mechanism based on the forces that surrounding tissues exert upon the vessel wall and lumen and an intrinsic mechanism based on spontaneous, rhythmic contractions of the lymphatic muscle layer of collecting vessels. The two spontaneous pacemakers described in literature involve chloride-dependent depolarizations (STDs) and I_f-like currents, both giving rise to a variable contraction frequency (f_c) of lymphatic vessels functional units (lymphangions). Several stimuli have been shown to modulate f_c, such as temperature, shear stress, and several tissue chemical modulators (prostaglandins, norepinephrine, acetylcholine, substance P, and others). However, no detailed description is present in literature on the acute modulation of f_c by means of osmolarity change of the surrounding interstitial space. Using a well-developed ex-vivo rat diaphragmatic preparation, in which osmolarity was changed by varying the concentration of D-mannitol in the perfusing solution and in later experiments the concentration of NaCl and then of Na⁺ and Cl⁻ ions separately by ionic substitution, we provide detailed experimental evidences that a stepwise increase in osmolarity from control value (308 mOsm) up to 324 mOsm caused a reduction of f_c down to ~-70% within the first 14 min, and that a stepwise decrease in osmolarity up to 290 mOsm induced an early f_c increase to ~+34% of control, followed by a decline to an f_c of ~-18% of control value. These variations were more dramatic when the same osmolarity changes were obtained by varying NaCl and/or Na⁺ or Cl⁻ ions concentration, which caused an almost complete arrest of spontaneous contractility within 14 min from the application. Diastolic and systolic diameters and stroke volume were not affected by osmolarity changes, so that modulation of lymph flow closely followed that of f_c. Modulation of lymph flow secondary to osmolarity changes is relevant if one considers that interstitial fluid balance is also dependent upon lymph drainage, and thus it is possible that, at least in the acute phase following variations of interstitial fluid osmolarity, its volume control might eventually be impaired due to the reduced or in the worst scenario null lymph drainage.

Challenges and Opportunities for the Subcutaneous Delivery of Therapeutic Proteins

Biotherapeutics is a rapidly growing drug class, and over 200 biotherapeutics have already obtained approval, with about 50 of these being approved in 2015 and 2016 alone. Several hundred protein therapeutic products are still in the pipeline, including interesting new approaches to treatment. Owing to patients' convenience of at home administration and reduced number of hospital visits as well as the reduction in treatment costs, subcutaneous (SC) administration of biologics is of increasing interest. Although several avenues for treatment using biotherapeutics are being explored, there is still a sufficient gap in knowledge regarding the interplay of formulation conditions, immunogenicity, and pharmacokinetics (PK) of the absorption of these compounds when they are given SC. This review seeks to highlight the major concerns and important factors governing this route of administration and suggest a holistic approach for effective SC delivery.

In vitro model for predicting bioavailability of subcutaneously injected monoclonal antibodies

Monoclonal antibodies (mAbs), which are now more frequently administered by subcutaneous (SC) injection rather than intravenously, have become a tremendously successful drug format across a wide range of therapeutic areas. Preclinical evaluations of mAbs to be administered by SC injection are typically performed in species such as mice, rats, minipigs, and cynomolgus monkeys to obtain critical information regarding formulation performance and prediction of PK/PD outcomes needed to select clinical doses for first-in-human studies. Despite extensive efforts, no preclinical model has been identified to date that accurately predicts clinical outcomes for these SC injections. We have addressed this deficiency with a novel in vitro instrument, termed Scissor, to model events occurring at the SC injection site and now further validated this approach using a set of eight mAbs for which clinical PK/PD outcomes have been obtained. Diffusion of these mAbs from the Scissor system injection cartridge into a large volume physiological buffer, used to emulate mAb movement from the SC injection site into the systemic circulation, provided distinct profiles when monitored over a 6h period. Curve-fitting analysis of these profiles using the Hill equation identified parameters that were used, along with physicochemical properties for each mAb, in a partial least squares analysis to define a relationship between molecule and formulation properties with clinical PK outcomes. The results demonstrate that parameters of protein charge at neutral pH and isoelectric point (pI) along with combined formulation properties such as viscosity and mAb concentration can dictate the movement of the mAb from the injection cartridge to infinite sink compartment. Examination of profile characteristics of this movement provided a strong predictive correlation for these eight mAbs. Together, this approach demonstrates the feasibility of this in vitro modelling strategy as a tool to identify drug and formulation properties that can define the performance of SC injected medicines and provide the potential for predicting clinical outcomes that could be useful for formulation selection and a first-in-human clinical dosing strategy.

Lymphatic transport and lymph node targeting of methotrexate-conjugated PEGylated dendrimers are enhanced by reducing the length of the drug linker or masking interactions with the injection site

Drug conjugation to dendrimer-based delivery systems has been shown to enhance delivery to the lymphatic system after subcutaneous administration. Dendrimer interaction with components of the interstitium at the injection site, however, may prevent drainage from the injection site. The current study sought to vary the length of a linker employed to conjugate methotrexate (MTX) to a PEGylated dendrimer, in an attempt to reduce MTX interaction with interstitial binding sites and enhance lymphatic drainage. Dendrimers with shorter linkers resulted in higher lymphatic drainage, presumably via shielding of interaction sites by the PEG mantle, but were not retained in lymph nodes. Improved drainage of dendrimers with longer linkers was achieved through coadministration with dextran to mask interactions at the injection site while maintaining retention within the node. Enhanced drug exposure to the lymph node has the potential to enhance the treatment of lymph-node resident cancer metastases.

Optimizing the Bioavailability of Subcutaneously Administered Biotherapeutics Through Mechanochemical Drivers

The subcutaneous route offers myriad benefits for the administration of biotherapeutics in both acute and chronic diseases, including convenience, cost effectiveness and the potential for automation through closed-loop systems. Recent advances in parenteral administration devices and the use of additives which enhance drug dispersion have generated substantial additional interest in IV to SQ switching studies. Designing pre-clinical and clinical studies using SQ mediated delivery however requires deep understanding of complex inter-related physiologies and transport pathways governing the interstitial matrix, vascular system and lymphatic channels. This expert review will highlight key structural features which contribute to transport and biodistribution in the subcutaneous space and also assess the impact of drug formulations. Based on the rapidly growing interest in the SQ delivery route, a number of potential areas for future development are highlighted, which are likely to allow continued evolution and innovation in this important area.

Pharmacokinetic and pharmacodynamic considerations for the next generation protein therapeutics

Increasingly sophisticated protein engineering efforts have been undertaken lately to generate protein therapeutics with desired properties. This has resulted in the discovery of the next generation of protein therapeutics, which include: engineered antibodies, immunoconjugates, bi/multi-specific proteins, antibody mimetic novel scaffolds, and engineered ligands/receptors. These novel protein therapeutics possess unique physicochemical properties and act via a unique mechanism-of-action, which collectively makes their pharmacokinetics (PK) and pharmacodynamics (PD) different than other established biological molecules. Consequently, in order to support the discovery and development of these next generation molecules, it becomes important to understand the determinants controlling their PK/PD. This review discusses the determinants that a PK/PD scientist should consider during the design and development of next generation protein therapeutics. In addition, the role of systems PK/PD models in enabling rational development of the next generation protein therapeutics is emphasized.

Anatomical, physiological, and experimental factors affecting the bioavailability of sc-administered large biotherapeutics

Subcutaneous route of administration is highly desirable for protein therapeutics. It improves patient compliance and quality of life (McDonald TA, Zepeda ML, Tomlinson MJ, Bee WH, Ivens IA. 2010. Curr Opin Mol Ther 12(4):461-470; Dychter SS, Gold DA, Haller MF. 2012. J Infus Nurs 35(3):154-160), while reducing healthcare cost (Dychter SS, Gold DA, Haller MF. 2012. J Infus Nurs 35(3):154-160). Recent evidence also suggests that sc administration of protein therapeutics can increase tolerability to some treatments such as intravenous immunoglobulin therapy by administering it subcutaneously (subcutaneous immunoglobulin therapy SCIG), which will reduce fluctuation in plasma drug concentration (Kobrynski L. 2012. Biologics 6:277-287). Furthermore, sc administration may reduce the risk of systemic infections associated with i.v. infusion (McDonald TA, Zepeda ML, Tomlinson MJ, Bee WH, Ivens IA. 2010. Curr Opin Mol Ther 12(4):461-470; Dychter SS, Gold DA, Haller MF. 2012. J Infus Nurs 35(3):154-160). This route, however, has its challenges, especially for large multidomain proteins. Poor bioavailability and poor scalability from preclinical models are often cited. This commentary will discuss barriers to sc absorption as well as physiological and experimental factors that could affect pharmacokinetics of subcutaneously administered large protein therapeutics in preclinical models. A mechanistic pharmacokinetic model is proposed as a potential tool to address the issue of scalability of sc pharmacokinetic from preclinical models to humans.