Subcutaneous immunoglobulin therapy: a new option for patients with primary immunodeficiency diseases

Immunoglobulin replacement therapy in patients with primary and secondary immunodeficiencies: impact of infusion method on immunoglobulin-specific perceptions of quality of life and treatment satisfaction

BACKGROUND

Immunoglobulin replacement therapy (IgRT) is the current standard of care for primary antibody deficiency patients (majority of all primary immunodeficiency (PID) diseases), with growing real-world evidence supporting use for secondary immunodeficiency (SID) patients. Infusion methods and practices can affect patients' satisfaction with their treatment and perception of their health-related quality of life.

METHODS

An online survey of US patients with PID and SID was conducted. This research investigates primarily the impact of two IgRT infusion methods, intravenous immunoglobulin therapy (IVIG) and subcutaneous immunoglobulin (SCIG), on the patient reported outcome (PRO) Life Quality Index (LQI) tool. Patient reported infusion time efficiency, physical and mental health (PROMIS GPH-2 and PROMIS GMH-2 respectively), patient acceptability of their symptom state (PASS), upper extremity disability (Quick DASH) and general health perception (via the GHP) are also investigated.

RESULTS

Responses of 990 patients (391 IVIG and 598 SCIG) were analyzed. The median total LQI score amongst SCIG patients (84.7) was higher than IVIG patients (81.9) (p < 0.001), and was significantly higher on 3 out of 4 sub-domains of the LQI. SCIG patients scored higher on items that are related to convenience and reported less interference with everyday life: "Are convenient", "Are scheduled according to my convenience", "Do not interfere with my work/school" and "Require very little time and cost". However, there was no significant difference between the two patient cohorts on other, non-IG specific PROs (PASS, PROMIS GPH-2 and GMH-2 and Quick DASH). Patient reported time per infusion was lower for SCIG infusions than IVIG infusions (pre-infusion time; 22 min vs. 63 min, p < 0.001, infusion time; 120 min vs. 240 min, p < 0.001, post-infusion time; 9 min vs. 31 min, p < 0.001). IVIG patients also reported more interference with everyday life than SCIG patients (82 vs. 86, p < 0.001).

CONCLUSIONS

The significantly higher LQI scores for patients receiving SCIG than those receiving IVIG confirms existing evidence that substitution of SCIG for IVIG may favorably impact immunoglobulin specific perceptions of quality of life and treatment satisfaction for appropriately selected patients. Our evidence on infusion times indicates similar improvement may be possible on infusion time efficiency.

A review of intravenous immunoglobulin in the treatment of neuroimmune conditions, acute COVID-19 infection, and post-acute sequelae of COVID-19 Syndrome

Intravenous immunoglobulin (IVIG) is an immunomodulatory therapy that has been studied in several neuroimmune conditions, such as Guillain-Barré Syndrome, chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy, and multiple sclerosis. It has also been proposed as a potential treatment option for acute COVID-19 infection and post-acute sequelae of SARS-CoV-2 infection (PASC). IVIG is thought to function by providing the recipient with a pool of antibodies, which can, in turn, modulate immune responses through multiple mechanisms including neutralization of cytokines and autoantibodies, saturation of neonatal fragment crystallizable receptors, inhibition of complement activation, and regulation of T and B cell mediated inflammation. In acute COVID-19, studies have shown that early administration of IVIG and plasmapheresis in severe cases can reduce the need for mechanical ventilation, shorten ICU and hospital stays, and lower mortality. Similarly, in PASC, while research is still in early stages, IVIG has been shown to alleviate persistent symptoms in small patient cohorts. Furthermore, IVIG has shown benefits in another condition which has symptomatic overlap with PASC, myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), though studies have yielded mixed results. It is important to note that IVIG can be associated with several potential adverse effects, such as anaphylaxis, headaches, thrombosis, liver enzyme elevations and renal complications. In addition, the high cost of IVIG can be a deterrent for payers and patients. This review provides a comprehensive update on the use of IVIG in multiple neuroimmune conditions, ME/CFS, acute COVID-19, and PASC, as well as covers its history, production, pricing, and mechanisms of action. We also identify key areas of future research, including the need to optimize the use of Ig product dosing, timing, and patient selection across conditions, particularly in the context of COVID-19 and PASC.

Customizing subcutaneous immunoglobulin administration in primary antibody deficiency: patient-centric care perspectives

This report delves into the challenges and potential solutions associated with flexible, customized subcutaneous immunoglobulin (SCIG) infusion regimens for patients with primary antibody deficiency disease (PAD). Advances in the treatment of inborn errors of immunity, particularly PAD, have converted fatal diseases into chronic, complex, long-term conditions that make adherence to treatment a critical issue. Conventional SCIG infusion regimens, while clinically effective, may not always align with the varied lifestyles, changing lifestyles and commitments of patients which can lead to missed doses, diminishing adherence thus posing potential health risks and compromising the overall effectiveness of treatment. For these reasons, it's important to develop flexible infusion regimens tailored to meet individual patient needs. Patient-centric strategies that promote shared decision-making and awareness of patient status not only promote medical efficacy but also enhance the overall patient experience. The authors of this report call attention for a need to shift toward more adaptable and individualized SCIG treatment plans for PAD patients whose needs may change over the long-term course of treatment.

Immunoglobulin therapies for primary immunodeficiency diseases (part 1): understanding the pharmacokinetics

Immunoglobulin G (IgG) therapies have been used for decades as standard treatment for patients with primary antibody deficiencies. Monitoring the pharmacokinetics (PK) of IgG is a key component in guiding treatment regimens. Despite the wealth of clinical experience, substantial gaps exist in our understanding of the true nature of IgGs and their disposition in humans. Furthermore, intrinsic and extrinsic factors may alter the PK of IgG, necessitating an individualized approach for patients. A comprehensive literature review was performed in order to summarize the PK of IgGs, examine the mechanisms of IgG disposition (including catabolism), outline considerations for special patient populations and discuss knowledge gaps and future perspectives for improving our understanding of IgG PK in relation to the individualized treatment paradigm.

Immunoglobulin therapies for primary immunodeficiency diseases (part 2): considerations for dosing strategies

Immunoglobulin G (IgG) dosing in treating primary immunodeficiency diseases (PIDs) is individualized, which often involves regular monitoring of IgG levels, and considers patient experiences with immunoglobulin therapies, their clinical status and physician judgment. The frequency and dose(s) of intravenously (IVIG) and subcutaneously (SCIG) administered IgGs (including hyaluronidase-facilitated SCIG) require rigorous evaluation to maximize therapeutic benefits. Monitoring serum IgG levels represents an integral part of diagnosing primary immunodeficiency diseases and determining or adjusting IgG dosing strategies to meet individual patient needs, but cannot be conducted in isolation. This review discusses the current state and future perspectives on dosing strategies for different types of IgG therapies, as well as dosing considerations for specific patient populations, immunoglobulin-naive patients and patients switching between IVIG and SCIG.

Stability of Protein Pharmaceuticals: Recent Advances

There have been significant advances in the formulation and stabilization of proteins in the liquid state over the past years since our previous review. Our mechanistic understanding of protein-excipient interactions has increased, allowing one to develop formulations in a more rational fashion. The field has moved towards more complex and challenging formulations, such as high concentration formulations to allow for subcutaneous administration and co-formulation. While much of the published work has focused on mAbs, the principles appear to apply to any therapeutic protein, although mAbs clearly have some distinctive features. In this review, we first discuss chemical degradation reactions. This is followed by a section on physical instability issues. Then, more specific topics are addressed: instability induced by interactions with interfaces, predictive methods for physical stability and interplay between chemical and physical instability. The final parts are devoted to discussions how all the above impacts (co-)formulation strategies, in particular for high protein concentration solutions.'

Immunoglobulin replacement therapies in inborn errors of immunity: a review

Immunoglobulins (Ig) were used as a therapeutic modality for the first time in a patient with X-linked agammaglobulinemia in 1952 by Colonel Ogden Bruton, decades before the molecular mechanisms causing the disease were unraveled. In many autoimmune and inflammatory illnesses, human immunoglobulin has been employed as a significant immunomodulatory and immunosuppressive drug. In patients with inborn errors of immunity (IEI), immunoglobulin remains a cornerstone of management. IEIs are notable causes of recurrent infections and autoimmunity due to inheritable single-gene defects in genes encoding for different components of the immune system. As there is decreased immunoglobulin production in IEIs with antibody defects, immunoglobulin replacement is the mainstay of therapy in these disorders. Although serum immunoglobulin levels may not be low in combined immune defects, immunoglobulin replacement is still necessary in these disorders due to a deficiency of functional antibodies and qualitative defects of immunoglobulins. Commercial immunoglobulin preparations are generated from plasma donated by thousands of donors. Immunoglobulin preparations are usually available in two forms: intravenous and subcutaneous immunoglobulins. In the developed world, both intravenous immunoglobulin (IVIg) and subcutaneous immunoglobulin (SCIg) are available, and SCIg is preferred over IVIg for replacement therapy in patients with IEIs. In developing countries, IVIg remains the mainstay of replacement therapy. The rate of adverse events has significantly reduced over the last few years due to advancements in the production process. In this review article, we discuss different aspects of the use of Ig (indications, dosing, mechanism of action, route, adverse effects) in patients with IEIs.

Initiating immunoglobulin replacement therapy helps reduce severe infections and shifts healthcare resource utilization to outpatient services among US patients with inborn errors of immunity

AIMS

Patients with inborn errors of immunity (IEI) are predisposed to severe recurrent/chronic infections, and often require hospitalization, resulting in substantial burden to patients/healthcare systems. While immunoglobulin replacement therapies (IgRTs) are the standard first-line treatment for most forms of IEI, limited real-world data exist regarding clinical characteristics and treatment costs for patients with IEI initiating such treatment. This retrospective analysis examined infection and treatment characteristics in US patients with IEI initiating IgRT with immune globulin infusion (human), 10% (IG10%). Healthcare resource utilization (HCRU) and associated costs before and after treatment initiation were compared. Additionally, the impact of COVID-19 on infection diagnoses was evaluated.

METHODS

Patients with IEI initiating IG10% between July 2012 and August 2019 were selected from Merative MarketScan Databases using diagnosis/prescription codes. Patients were followed 6 months before and after first IG10% claim date. Demographic and clinical characteristics were described. Treatment characteristics and HCRU before and after IG10% initiation were compared. Infection diagnoses during 2020 and 2019 (March-December) were compared.

RESULTS

The study included 1,497 patients with IEI diagnoses (mean age = 43.4 years) initiating IG10%, with frequently reported comorbidities like asthma (32.1%). Following IG10% initiation, fewer severe infection diagnoses (11.6% vs 19.9%), fewer infection-related inpatient (10.8% vs 19.5%) and outpatient services (71.6% vs 79.9%), and lower infection-related total healthcare costs ($7,849 vs $13,995; p < 0.001)-driven by lower inpatient costs ($2,746 vs $9,900)-were observed than before. Fewer patients had infection diagnoses during COVID-19 (22.8%) than the prior year (31.2%).

CONCLUSION

Patients with IEI are susceptible to severe infections leading to high disease burden and treatment costs. Following IG10% initiation, we observed fewer infections, lower infection-related treatment costs, and shift in care (inpatient to outpatient) leading to significant cost savings. Among patients with IEI, 27% fewer infection diagnoses were observed during the early COVID-19 lockdown period than the prior year.

An unsupervised learning approach to identify immunoglobulin utilization patterns using electronic health records

BACKGROUND

Managing Canada's immunoglobulin (Ig) product resource allocation is challenging due to increasing demand, high expenditure, and global shortages. Detection of groups with high utilization rates can help with resource planning for Ig products. This study aims to uncover utilization subgroups among the Ig recipients using electronic health records (EHRs).

METHODS

The study included all Ig recipients (intravenous or subcutaneous) in Calgary from 2014 to 2020, and their EHR data, including blood inventory, recipient demographics, and laboratory test results, were analyzed. Patient clusters were derived based on patient characteristics and laboratory test data using K-means clustering. Clusters were interpreted using descriptive analyses and visualization techniques.

RESULTS

Among 4112 recipients, six clusters were identified. Clusters 1 and 2 comprised 408 (9.9%) and 1272 (30.9%) patients, respectively, contributing to 62.2% and 27.1% of total Ig utilization. Cluster 3 included 1253 (30.5%) patients, with 86.4% of infusions administered in an inpatient setting. Cluster 4, comprising 1034 (25.1%) patients, had a median age of 4 years, while clusters 2-6 were adults with median ages of 46-60. Cluster 5 had 62 (1.5%) patients, with 77.3% infusions occurring in emergency departments. Cluster 6 contained 83 (2.0%) patients receiving subcutaneous Ig treatments.

CONCLUSION

The results identified data-driven segmentations of patients with high Ig utilization rates and patients with high risk for short-term inpatient use. Our report is the first on EHR data-driven clustering of Ig utilization patterns. The findings hold the potential to inform demand forecasting and resource allocation decisions during shortages of Ig products.

Mechanisms of Obesity-Induced Changes in Pharmacokinetics of IgG in Rats

PURPOSE

To evaluate how obesity affects the pharmacokinetics of human IgG following subcutaneous (SC) and intravenous (IV) administration to rats and the homeostasis of endogenous rat IgG.

METHODS

Differences in body weight and size, body composition, and serum concentration of endogenous rat IgG in male Zucker obese (ZUC-FA/FA) and control (ZUC-LEAN) rats were measured from the age of 5 weeks up to 30 weeks. At the age of 23-24 weeks animals received a single IV or SC dose of human IgG (1 g/kg of total body weight), and serum pharmacokinetics was followed for 7 weeks. A mechanistic model linking obesity-related changes in pharmacokinetics with animal growth and changes in body composition was developed.

RESULTS

Significant differences were observed in both endogenous and exogenous IgG pharmacokinetics between obese and control groups. The AUC for human IgG was lower in obese groups (57.6% of control after IV and 48.1% after SC dosing), and clearance was 1.75-fold higher in obese animals. The mechanistic population model successfully captured the data and included several major components: endogenous rat IgG homeostasis with age-dependent synthesis rate; competition of human IgG and endogenous rat IgG for FcRn binding and its effect on endogenous rat IgG concentrations following injection of a high dose of human IgG; and the effect of body size and composition (changing over time and dependent on the obesity status) on pharmacokinetic parameters.

CONCLUSIONS

We identified important obesity-induced changes in the pharmacokinetics of IgG. Results can potentially facilitate optimization of the dosing of IgG-based therapeutics in the obese population.

Imaging of large volume subcutaneous deposition using MRI: exploratory clinical study results

Subcutaneous (SC) delivery is a preferred route of administration for biotherapeutics but has predominantly been limited to volumes below 3 mL. With higher volume drug formulations emerging, understanding large volume SC (LVSC) depot localization, dispersion, and impact on the SC environment has become more critical. The aim of this exploratory clinical imaging study was to assess the feasibility of magnetic resonance imaging (MRI) to identify and characterize LVSC injections and their effect on SC tissue as a function of delivery site and volume. Healthy adult subjects received incremental injections of normal saline up to 5 mL total volume in the arm and up to 10 mL in the abdomen and thigh. MRI images were acquired after each incremental SC injection. Post-image analysis was performed to correct imaging artifacts, identify depot tissue location, create 3-dimensional (3D) SC depot rendering, and estimate in vivo bolus volumes and SC tissue distention. LVSC saline depots were readily achieved, imaged using MRI, and quantified via subsequent image reconstructions. Imaging artifacts occurred under some conditions, necessitating corrections applied during image analysis. 3D renderings were created for both the depot alone and in relation to the SC tissue boundaries. LVSC depots remained predominantly within the SC tissue and expanded with increasing injection volume. Depot geometry varied across injection sites and localized physiological structure changes were observed to accommodate LVSC injection volumes. MRI is an effective means to clinically visualize LVSC depots and SC architecture allowing assessment of deposition and dispersion of injected formulations.Trial Registration: Not applicable for this exploratory clinical imaging study.

Subcutaneous immunoglobulin 16.5% for the treatment of pediatric patients with primary antibody immunodeficiency

INTRODUCTION

Human immunoglobulin (IG) administered intravenously (IVIG) or subcutaneously (SCIG) is used to prevent infections in patients with primary immunodeficiency diseases (PIDDs) such as primary antibody immunodeficiencies.

AREAS COVERED

This review provides an overview of PIDD with a focus on SCIG treatment, including the properties and clinical trial results of a new SCIG 16.5% (Cutaquig, Octapharma) in pediatric patients. We also discuss the various benefits of SCIG including stable serum immunoglobulin G levels, high tolerability with fewer systemic side effects, and the flexibility of self-administration.

EXPERT OPINION

Individualized treatment for PIDD in children is necessary given the different factors that affect administration of SCIG. Variables such as the dose, dosing interval, administration sites, and ancillary equipment can be adjusted to impact the long-term satisfaction with SCIG administration in pediatric patients. The successful work that has been conducted by both professional and patient organizations to increase awareness of PIDD, especially in pediatric patients, is substantial and ongoing. The importance of early diagnosis and treatment in the pediatric patient population cannot be overstated. The safety, efficacy, and tolerability of SCIG 16.5% have been demonstrated in pediatric patients with PIDDs providing an additional therapeutic option in this vulnerable population.

A clinician's guide for administration of high-concentration and facilitated subcutaneous immunoglobulin replacement therapy in patients with primary immunodeficiency diseases

Immunoglobulin replacement therapy is the standard-of-care treatment for patients with primary immunodeficiency diseases who have impaired antibody production and function. Clinicians and patients may consider intravenous immunoglobulin (IVIG) or subcutaneous immunoglobulin (SCIG) options, and each route may offer different benefits for the individual. IVIG requires fewer infusion sites and less frequent infusions than some formulations of SCIG. However, SCIG does not require venous access, is associated with fewer systemic adverse infusion reactions than IVIG, and can independently be self-administered at home. Importantly, tailoring treatment experiences to the needs of the individual may improve treatment adherence and quality of life for patients with primary immunodeficiency diseases who often rely on long-term or lifelong treatment. This review aims to educate United States (US) healthcare providers on the administration process of SCIG, with a focus on more concentrated formulations of SCIG and facilitated SCIG. It provides practical guidance on initiating, optimizing, and monitoring SCIG therapy. The advantages and disadvantages of the different treatment options are also presented for discussion between the patient and clinician.

Cost-minimization analysis of immunoglobulin treatment of primary immunodeficiency diseases in Spain

Primary immunodeficiency diseases (PID), which are comprised of over 400 genetic disorders, occur when a component of the immune system is diminished or dysfunctional. Patients with PID who require immunoglobulin (IG) replacement therapy receive intravenous IG (IVIG) or subcutaneous IG (SCIG), each of which provides equivalent efficacy. We developed a cost-minimization model to evaluate costs of IVIG versus SCIG from the Spanish National Healthcare System perspective. The base case modeled the annual cost per patient of IVIG and SCIG for the mean doses (per current expert clinical practice) over 1 year in terms of direct (drug and administration) and indirect (lost productivity for adults and parents/guardians of pediatric patients) costs. It was assumed that all IVIG infusions were administered in a day hospital, and 95% of SCIG infusions were administered at home. Drug costs were calculated from ex-factory prices obtained from local databases minus the mandatory deduction. Costs were valued on 2018 euros. The annual modeled costs were €4,266 lower for patients with PID who received SCIG (total €14,466) compared with those who received IVIG (total €18,732). The two largest contributors were differences in annual IG costs as a function of dosage (- €1,927) and hospital administration costs (- €2,688). However, SCIG incurred training costs for home administration (€695). Sensitivity analyses for two dose-rounding scenarios were consistent with the base case. Our model suggests that SCIG may be a cost-saving alternative to IVIG for patients with PID in Spain.

Granulomatous-Lymphocytic Interstitial Lung Disease Mimicking Sarcoidosis

Common variable immunodeficiency (CVID) is one of the most common primary immunodeficiency disorders characterized by hypogammaglobulinemia and inadequate antibody response to immunizations. The impaired antibody response occurs due to the failure of B cells to differentiate into plasma cells resulting in low immunoglobulins levels and increased frequency of infections. Granulomatous and Lymphocytic Interstitial Lung Disease (GLILD) is a non-infectious complication of CVID that is seen in 10-30% of cases. GLILD is a multisystem inflammatory disease involving the lungs, lymph node, liver, spleen and gastrointestinal tract that mimics sarcoidosis. This report describes a series of cases who presented with dyspnea, recurrent respiratory infections or autoimmunity and on further evaluation revealed features suggestive of GLILD. There is very limited understanding of GLILD in terms of clinical presentation, the histo-pathological logical findings, and the diagnostic criteria by itself are limited. A diagnosis of GLILD is established in cases of CVID when there is evidence of lymphoproliferation, cytopenia, autoimmune processes and a lung biopsy demonstrating lymphocytic interstitial pneumonia, follicular bronchiolitis, lymphoid hyperplasia, and/or non-necrotizing granulomas. We review the treatment strategies, including replacement of immunoglobulin and agents targeting B and T lymphocytes. Systematic characterization of GLILD cases and long term follow up studies are sorely needed to understand the natural history of GLILD.

Steady-State Serum IgG Trough Levels Are Adequate for Pharmacokinetic Assessment in Patients with Immunodeficiencies Receiving Subcutaneous Immune Globulin

Patients with primary immunodeficiency diseases often require lifelong immunoglobulin (IG) therapy. Most clinical trials investigating IG therapies characterize serum immunoglobulin G (IgG) pharmacokinetic (PK) profiles by serially assessing serum IgG levels. This retrospective analysis evaluated whether steady-state serum IgG trough level measurement alone is adequate for PK assessment. Based on individual patient serum IgG trough levels from two pivotal trials (phase 2/3 European [NCT01412385] and North American [NCT01218438]) of weekly 20% subcutaneous IG (SCIG; Cuvitru, Ig20Gly), trough level-predicted IgG AUC (AUC_τ,tp) were calculated and compared with the reported AUC calculated from serum IgG concentration-time profiles (AUC_τ). In both studies, mean AUC_τ,tp values for Ig20Gly were essentially equivalent to AUC_τ with point estimates of geometric mean ratio (GMR) of AUC_τ,tp/AUC_τ near 1.0 and 90% CIs within 0.80-1.25. In contrast, for IVIG, 10%, mean AUC_τ,tp values were lower than AUC_τ by >20%, (GMR [90% CI]: 0.74 [0.70-0.78] and 0.77 [0.73-0.81] for the two studies, respectively). Mean AUC_τ,tp values calculated for 4 other SCIG products (based on mean IgG trough levels reported in the literature/labels) were also essentially equivalent to the reported AUC_τ (differences <10% for all except HyQvia, a facilitated SCIG product), while differences for IVIG products were >20%. In conclusion, steady-state serum IgG levels following weekly SCIG remain stable, allowing for reliable prediction of AUC over the dosing interval using trough IgG levels. These findings indicate that measuring steady-state serum IgG trough levels alone may be adequate for PK assessment of weekly SCIG.

Practical Aspects of Transitioning from Intravenous to Subcutaneous Immunoglobulin Therapy in Neuromuscular Disorders

Recent evidence shows that subcutaneous immunoglobulin (SCIG) is as efficacious as intravenous immunoglobulin (IVIG) and has a better safety profile and acceptance rate among patients with neuromuscular disorders who require maintenance IVIG treatment. Awareness of the practical aspects of patient selection, enrollment, dose calculation, administration, and follow-up would help physicians coordinate a smooth and seamless transition from IVIG to SCIG. SCIG is ideally offered to patients having intolerable side effects during IVIG or wearing-off effect and in those keen for treatment autonomy. The weekly dose of SCIG is calculated by multiplying the maintenance dose of IVIG by the dose adjustment factor and dividing by the interval between IVIG in weeks and is initiated 1 week after the last dose of IVIG. The physician places the order for the SCIG and the clinic nurse or the physician refers the patient to the home care nursing program for further education and training. The necessary supplies are dispatched to the patient who would also collect the SCIG from the transfusion center of the nearest hospital. The patient is educated on assembling and administering the infusion, and home visits are continued until the patient or caregiver is confident. Regular follow-up with the patient is maintained to assess treatment response and side effects if any. With a smooth transition, most patients have excellent tolerance to SCIG and in our experience seldom request switching back to IVIG. Transitioning patients from IVIG to SCIG offers several advantages and thus, in general, is preferable for multiple stakeholders.

Novel Treatments in Myasthenia Gravis

Myasthenia gravis (MG) is the prototypical autoimmune disorder caused by specific autoantibodies at the neuromuscular junction. Broad-based immunotherapies, such as corticosteroids, azathioprine, mycophenolate, tacrolimus, and cyclosporine, have been effective in controlling symptoms of myasthenia. While being effective in a majority of MG patients many of these immunosuppressive agents are associated with long-term side effects, often intolerable for patients, and take several months to be effective. With advances in translational research and drug development capabilities, more directed therapeutic agents that can alter the future of MG treatment have been developed. This review focuses on the aberrant immunological processes in MG, the novel agents that target them along with the clinical evidence for efficacy and safety. These agents include terminal complement C5 inhibitors, Fc receptor inhibitors, B cell depleting agents (anti CD 19 and 20 and B cell activating factor [BAFF)]inhibitors), proteosome inhibitors, T cells and cytokine based therapies (chimeric antigen receptor T [CART-T] cell therapy), autologous stem cell transplantation, and subcutaneous immunoglobulin (SCIG). Most of these new agents have advantages over conventional immunosuppressive treatment (IST) for MG therapy in terms of faster onset of action, favourable side effect profile and the potential for a sustained and long-term remission.

Long-term efficacy, safety, and tolerability of recombinant human hyaluronidase-facilitated subcutaneous infusion of immunoglobulin (Ig) (fSCIG; HyQvia(®)) in immunodeficiency diseases: real-life data from a monocentric experience

Humoral immunodeficiency diseases represent a heterogeneous group of disorders that require long-term therapies. Thus, the treatment provided must not only be effective but also safe and well tolerated. In this paper, we report our data on the efficacy, safety, and tolerability of recombinant human hyaluronidase-facilitated subcutaneous infusion of immunoglobulin (Ig) (fSCIG; HyQvia(^®)) in immunodeficiency patients. We collected retrospective data from 30 patients with primary and secondary immunodeficiency diseases in therapy with fSCIG from September 2014 to December 2019. We evaluated the efficacy of the therapy, taking into account serum IgG values during follow-up and the number of annual infectious events and serious bacterial infections reported by patients. Safety was assessed on the basis of the number and intensity of adverse events (AEs) and local reactions reported. Our real-life data suggest that long-term repeated self-administration of recombinant human hyaluronidase-facilitated subcutaneous infusion of immunoglobulins results in a reduced rate of infectious events if compared to the pre-treatment rate. Both AEs and local reactions are mild to moderate and were never reasons for treatment discontinuation. Therapy with HyQvia shows prolonged efficacy and good tolerability; these aspects, together with the possibility of self-administration at home, minimize the impact the illness has on patients.

Patient experience with subcutaneous immunoglobulin 20%, Ig20Gly, for primary immunodeficiency diseases: a prespecified post hoc analysis of combined data from 2 pivotal trials

BACKGROUND

Often, patients with primary immunodeficiency diseases (PID), which are marked by the absence or loss of functional antibodies, require lifelong treatment with immunoglobulin (IG) replacement therapy administered either intravenously (intravenous immunoglobulin [IVIG]) or subcutaneously (subcutaneous immunoglobulin [SCIG]). In patients with PID, the 20% SCIG product, Ig20Gly, was shown to be efficacious and well tolerated in 2 phase 2/3 trials conducted in North America and Europe. This analysis evaluated patient satisfaction with Ig20Gly therapy and treatment preferences.

METHODS

This prespecified post hoc analysis showed combined data from 2 Ig20Gly pivotal trials. Treatment satisfaction was assessed in the pre-Ig20Gly period and after ≥11 months of Ig20Gly treatment using the Life Quality Index (LQI; both studies) and the Treatment Satisfaction Questionnaire for Medication-9 (TSQM-9; North American study only). Treatment preference was assessed using a survey at the end of the European study. Median within-patient differences in LQI and TSQM-9 scores between the pre-Ig20Gly period and the end of the Ig20Gly treatment period were assessed using the Wilcoxon signed-rank test.

RESULTS

A total of 113 patients (n = 68 [North American]; n = 45 [Europe]) with PID were included in the analysis. In the combined LQI analysis (n = 110), significant improvements were observed in the treatment interference (median ∆: + 2.8; P = 0.006) and therapy setting (median ∆: + 5.6; P < 0.0001) domains, and in the item-level scores for convenience (median ∆: + 1.0; P < 0.0001) and interference with work/school (median ∆: + 1.0; P = 0.0001) categories. In the subgroup analyses, significant improvements in the treatment interference and therapy setting domains and the convenience and interference with work/school items were observed for those who had previously received treatment outside the home, those who had previously received IVIG, and those in the North American study. Significant improvements were observed in the TSQM-9 treatment convenience domain (median ∆: + 11.1; P < 0.0001) and selected item-level scores in the North American study. In the European study, most (88.9%) patients preferred to continue Ig20Gly versus other IG treatments.

CONCLUSIONS

After ≥11 months of taking Ig20Gly, patients reported high levels of treatment satisfaction, convenience, and preference for Ig20Gly, with consistent results across studies and use of multiple patient-reported outcome measures.

Fatigue and the wear-off effect in adult patients with common variable immunodeficiency

Patients with common variable immunodeficiency (CVID) have increased fatigue compared with the general population. Fatigue is associated with lower quality of life (QoL), which is associated with higher mortality in CVID. This study aimed to determine the prevalence of self-reported fatigue for patients with CVID and to identify its possible drivers and burden on QoL. We analysed data from the 2013 Immune Deficiency Foundation (IDF) treatment survey. Answers were included from 873 CVID patients who responded (respondents). Of the 873 respondents included in the analysis, 671 (76·9%) reported fatigue, of whom 400 (83·7%) were receiving intravenous (i.v.) immunoglobulins (IVIG) and 271 (68·6%) were receiving subcutaneous (s.c.) immunoglobulins. This difference in fatigue between patients receiving IVIG and SCIG was statistically significant (P < 0·001). Dose and frequency of immunoglobulin replacement therapy (IgGRT) did not affect fatigue prevalence. Fatigued patients on IVIG reported greater infection rates and required more anti-microbials during the wear-off period. Fatigued patients reported worse health status than non-fatigued patients, and had lower rates of employment, education, household income and school attendance than their non-fatigued counterparts. Fatigue is increased in CVID, especially among patients receiving IVIG, compared to SCIG. Fatigue has a significant impact on QoL and productivity in patients with CVID. Further studies to identify the mechanisms of fatigue are warranted to help advance therapeutic measures to treat this disease and improve patients' QoL and wellbeing.

Subcutaneous Administration of Biotherapeutics: An Overview of Current Challenges and Opportunities

Subcutaneous delivery of biotherapeutics has become a valuable alternative to intravenous administration across many disease areas. Although the pharmacokinetic profiles of subcutaneous and intravenous formulations differ, subcutaneous administration has proven effective, safe, well-tolerated, generally preferred by patients and healthcare providers and to result in reduced drug delivery-related healthcare costs and resource use. The aim of this article is to discuss the differences between subcutaneous and intravenous dosing from both health-economic and scientific perspectives. The article covers different indications, treatment settings, administration volumes, and injection devices. We focus on biotherapeutics in rheumatoid arthritis (RA), immunoglobulin-replacement therapy in primary immunodeficiency (PI), beta interferons in multiple sclerosis (MS), and monoclonal antibodies (mAbs) in oncology. While most subcutaneous biotherapeutics in RA, PI, and MS are self-administered at home, mAbs for oncology are still only approved for administration in a healthcare setting. Beside concerns around the safety of biotherapeutics in oncology, a key challenge for self-administration in this area is that doses and dosing volumes can be comparatively large; however, this difficulty has recently been overcome to some extent by the development of high-concentration solutions, the use of infusion pumps, and the coadministration of the dispersion enhancer hyaluronidase. Furthermore, given the increasing number of biotherapeutics being considered for combination therapy and the high dosing complexity associated with these, especially when administered intravenously, subcutaneous delivery of fixed-dose combinations might be an alternative that will diminish these burdens on healthcare systems.

Neonatal Fc receptor antagonist efgartigimod safely and sustainably reduces IgGs in humans

BACKGROUND

Intravenous Ig (IVIg), plasma exchange, and immunoadsorption are frequently used in the management of severe autoimmune diseases mediated by pathogenic IgG autoantibodies. These approaches modulating IgG levels can, however, be associated with some severe adverse reactions and a substantial burden to patients. Targeting the neonatal Fc receptor (FcRn) presents an innovative and potentially more effective, safer, and more convenient alternative for clearing pathogenic IgGs.

METHODS

A randomized, double-blind, placebo-controlled first-in-human study was conducted in 62 healthy volunteers to explore single and multiple ascending intravenous doses of the FcRn antagonist efgartigimod. The study objectives were to assess safety, tolerability, pharmacokinetics, pharmacodynamics, and immunogenicity. The findings of this study were compared with the pharmacodynamics profile elicited by efgartigimod in cynomolgus monkeys.

RESULTS

Efgartigimod treatment resulted in a rapid and specific clearance of serum IgG levels in both cynomolgus monkeys and healthy volunteers. In humans, single administration of efgartigimod reduced IgG levels up to 50%, while multiple dosing further lowered IgGs on average by 75% of baseline levels. Approximately 8 weeks following the last administration, IgG levels returned to baseline. Efgartigimod did not alter the homeostasis of albumin or Igs other than IgG, and no serious adverse events related to efgartigimod infusion were observed.

CONCLUSION

Antagonizing FcRn using efgartigimod is safe and results in a specific, profound, and sustained reduction of serum IgG levels. These results warrant further evaluation of this therapeutic approach in IgG-driven autoimmune diseases.

TRIAL REGISTRATION

Clinicaltrials.gov NCT03457649.

FUNDING

argenx BVBA.

Rapid Push vs Pump-Infused Subcutaneous Immunoglobulin Treatment: a Randomized Crossover Study of Quality of Life in Primary Immunodeficiency Patients

PURPOSE

Subcutaneous immunoglobulin replacement therapy (IgRT) may be administered once a week with a pump or every other day with a syringe (rapid push). The objective of the study was to compare the impact of pump and rapid push infusions on patient's life quality index (LQI).

METHODS

This study was a randomized, crossover, multicenter, non-inferiority trial conducted in adults with primary immunodeficiency (PID) accustomed to weekly infusions at home by pump. Patients used pump or rapid push for 3 months each according to the randomized sequence. Main criterion was PID-LQI factor I (treatment interference). Non-inferiority ratio was set at 90%.

RESULTS

Thirty patients entered the study; 28 completed the two periods. IgRT exposure was similar during each period. At the end of each period, mean LQI factor 1 was 87.0 (IC95% [80.3; 94.3]) and 77.80 (IC95% [71.5; 84.7]) for pump and rapid push, respectively. There was a slightly larger effect of rapid push on treatment interference than with pump so that the primary endpoint could not be met. No difference was found on other LQI components, satisfaction (TSQM), or quality of life (SF36v2). Eight patients declared to prefer rapid push while 19 others preferred pump. Of rapid push infusions, 67.2% led to local reactions vs 71.8% of pump infusions (p = 0.11) illustrating its good tolerance. Rapid push and pump infusions achieved similar trough IgG levels with similar incidence of infections. Rapid push saved 70% of administration cost when compared to pump.

CONCLUSIONS

Since IgRT is a lifelong treatment in PID patients, individualization of treatment is of paramount importance. Rapid push is a new administration method in the physician's armamentarium which is preferred by some patients and is cost-effective. CLINICALTRIALS.

GOV IDENTIFIER

NCT02180763 CLINICAL IMPLICATIONS: Self-administration of small volumes of immunoglobulins at home, every other day, using a syringe (rapid push) is a cost-effective alternative to administration of larger volumes by pump once a week. This study compared subcutaneous infusions of immunoglobulins either weekly via a pump or every other day via a syringe (rapid push). Rapid push is preferred by some patients and is cost-effective, therefore completing a physician's armamentarium.

An evaluation of the budget impact of a new 20% subcutaneous immunoglobulin (Ig20Gly) for the management of primary immunodeficiency diseases in Switzerland

Introduction

While most individual primary immunodeficiency diseases (PID) are rare, the collective prevalence of PID results in a substantial economic and clinical burden. The aim of this study was to evaluate the budgetary implications of Ig20Gly (Immune Globulin Subcutaneous [human] 20% solution; CUVITRU^®, Baxalta US Inc, now part of Shire Plc, Westlake Village, CA, USA) as a treatment for PID relative to intravenous immunoglobulin (IVIG) and other subcutaneous immunoglobulin (SCIG) formulations in the Swiss health care setting.

Materials and methods

A budget impact model was developed in Microsoft Excel to capture the estimated prevalence of PID in Switzerland, the proportion of patients treated in different health care settings, and the costs of administering SCIG and IVIG in each setting. Unit costs were based on a recent cost-minimization analysis of SCIG in Lausanne, and drug costs were taken from the Spezialitätenliste. All costs were reported in 2016 Swiss Francs (CHF), and future costs were not discounted.

Results

The total cost of treating PID in Switzerland was estimated to be CHF 11.16 m over 3 years, comprising CHF 9.28 m of drug costs and CHF 1.87 m of ancillary costs, including health care professional time and other administration costs, such as pumps and needle sets. The analysis showed that using Ig20Gly in place of other SCIG formulations would be cost neutral, while using Ig20Gly in place of IVIG would result in savings of 4.0%.

Conclusion

Ig20Gly would be cost neutral relative to existing SCIG products and would result in cost savings relative to IVIG in patients with PID in Switzerland, even with modest uptake.

In-depth interviews of patients with primary immunodeficiency who have experienced pump and rapid push subcutaneous infusions of immunoglobulins reveal new insights on their preference and expectations

PURPOSE

Patients with primary immunodeficiency (PID) often receive immunoglobulin replacement therapy (IgRT). Physicians and patients have the choice between various methods of administration. For subcutaneous immunoglobulin infusions, patients may use an automated pump (P) or push the plunger of a syringe (rapid push [RP]). P infusions are performed once a week and last around 1 hour. RP decreases the duration of administration, but requires more frequent infusions.

PATIENTS AND METHODS

Eight out of 30 patients (coming from a single center) who had participated in the cross-over, randomized, open-label trial comparing P and RP participated in a focus group or underwent in-depth interviews. Patients had a long history of home-based subcutaneous immunoglobulin using P. The trial suggested that RP had slightly greater interference on daily life than P, but similar efficacy and better cost-effectiveness. When asked about the delivery method they had preferred, around one-third of patients pointed out RP rather than P. In-depth interviews may reveal unforeseen reasons for patients' preferences.

RESULTS

Interviews underlined the complexity of the relationship that the patients maintain with their disease and IgRT. Even if they recognized the genetic nature of the disease and claimed PID was a part of them, patients tried not to be overwhelmed by the disease. IgRT by P was well integrated in patients' routine. By contrast, RP too frequently reminded the patients of their disease. In addition, some patients pointed out the difficulty of pushing the plunger due to the viscosity of the product. Coming back too frequently, RP was not perceived as time saving over a week. Long-lasting use of P could partly explain patients' reasonable reluctance to change to RP.

CONCLUSION

In-depth interviews of PID patients highlighted unforeseen reasons for patients' preference that the physician needs to explore during the shared medical decision-making process.

II Brazilian Consensus on the use of human immunoglobulin in patients with primary immunodeficiencies

In the last few years, new primary immunodeficiencies and genetic defects have been described. Recently, immunoglobulin products with improved compositions and for subcutaneous use have become available in Brazil. In order to guide physicians on the use of human immunoglobulin to treat primary immunodeficiencies, based on a narrative literature review and their professional experience, the members of the Primary Immunodeficiency Group of the Brazilian Society of Allergy and Immunology prepared an updated document of the 1^st Brazilian Consensus, published in 2010. The document presents new knowledge about the indications and efficacy of immunoglobulin therapy in primary immunodeficiencies, relevant production-related aspects, mode of use (routes of administration, pharmacokinetics, doses and intervals), adverse events (major, prevention, treatment and reporting), patient monitoring, presentations available and how to have access to this therapeutic resource in Brazil.

Home-Based Subcutaneous Infusion of Immunoglobulin for Primary and Secondary Immunodeficiencies: A Health Technology Assessment

BACKGROUND

There are currently two methods used to administer immunoglobulin: intravenous (IV) infusion, the conventional method, and subcutaneous (SC) infusion, a newer alternative. The aim of this assessment was to compare administration of SC immunoglobulin at home with IV immunoglobulin in hospital with respect to benefits, harm, and costs. We also investigated the lived experiences of patients, looking at their quality of life, satisfaction, opinions, and preferences.

METHODS

We searched the literature for studies that compared home-based SC infusion with hospital- or clinic-based IV infusion of immunoglobulin in the treatment of primary and secondary immunodeficiency in adults and children. Two review authors reviewed the abstracts and full text of the relevant studies, and abstracted the data.We also performed a review of the economic literature comparing SC infusion at home versus IV infusion of immunoglobulin in a hospital or outpatient clinic in patients with primary or secondary immunodeficiency disorders. We also performed a budget impact analysis to estimate the 5-year cost burden of funding home-based SC infusion programs. All costs were reported in 2017 Canadian dollars.This health technology assessment followed a consultation plan for public engagement. We focused on interviews to examine the lived experience of patients with immunodeficiency, including those having experience of intravenous and/or subcutaneous immunoglobulin treatment.

RESULTS

Sixteen studies met the inclusion criteria. The annual rate of serious bacterial infection per patient did not differ. The annual rate of all infections per patient was relatively lower with home-based SC infusion than with hospital-based IV infusion. Both methods provided an adequate blood (serum) level of immunoglobulin and the pooled mean difference in immunoglobulin level favoured home-based SC infusion. Severe adverse reactions were rare with either method. The risk of adverse events such as fever or headache were higher with IV, while SC infusion sometimes caused infusion site reactions such as swelling, redness, or pain. Where reported, incidence of hospitalization, antibiotic use, and missed days from work or school either did not differ or were lower for SC infusion. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) of evidence for these outcomes was determined to be low.The scores for quality of life and treatment satisfaction either did not differ between the two methods or were significantly higher for some domains with home-based SC infusion. The three important concerns of patients in Ontario regarding home-based programs are loss of supervision, cost, and frequent injections.We identified four economic studies with six analyses (five cost-minimization and one cost-utility). All six analyses suggested that home-based infusion has lower costs, with one also showing greater effectiveness. Results of the budget impact analysis suggest that funding home-based SC infusion program would yield savings of about $0.4 million in the first year, and about $1.6 million by year 5. The total savings from funding home-based SC infusion are approximately $5.0 million over 5 years. Greater savings are indicated when the analysis is conducted from the societal perspective.In speaking directly with patients and their caregivers we found that immunodeficiency reduces quality of life. Intravenous treatment was said to be effective but consumed time and induced side-effects.

CONCLUSIONS

The best available evidence suggests that home-based SC infusion is safe and effective, with clinical outcomes that are comparable to the clinical outcomes of hospital IV infusion. The quality of evidence is low, however, meaning that we cannot be certain about these findings. The shift from hospital-based IV to home-based SC has the potential to reduce the health care costs due to savings in nursing time in Ontario. Patients and caregivers expressed preference for home-based SC treatment as it reduces treatment burden and improves overall quality of life.

Immune Gamma Globulin Therapeutic Indications in Immune Deficiency and Autoimmunity

Immune gamma globulin (IgG) has a long history in the treatment of both primary immune deficiency and autoimmune disorders. Disease indications continue to expand and new-generation products increase the versatility of delivery. This review encompasses a historical perspective as well as current and future implications of human immune globulin for the treatment of immune-mediated illness.

A cohort of French pediatric patients with primary immunodeficiencies: are patient preferences regarding replacement immunotherapy fulfilled in real-life conditions?

OBJECTIVE

To assess quality of life and satisfaction regarding immunoglobulin-replacement therapy (IgRT) treatment according to the route (intravenous Ig [IVIg] or subcutaneous Ig [SCIg]) and place of administration (home-based IgRT or hospital-based IgRT).

SUBJECTS AND METHODS

Children 5-15 years old treated for primary immunodeficiency disease (PIDD) with IgRT for ≥3 months were included in a prospective, noninterventional cohort study and followed over 12 months. Quality of life was assessed with the Child Health Questionnaire - parent form (CHQ-PF)-50 questionnaire. Satisfaction with IgRT was measured with a three-dimensional scale (Life Quality Index [LQI] with three components: factor I [F_I], treatment interference; F_II, therapy-related problems; F_III, therapy settings).

RESULTS

A total of 44 children (9.7±3.2 years old) receiving IgRT for a mean of 5.6±4.5 years (median 4.1 years) entered the study: 18 (40.9%) were receiving hospital-based IVIg, two (4.6%) were receiving home-based IVIg, and 24 (54.6%) were treated by home-based SCIg. LQI F_III was higher for home-based SCIg than for hospital-based IVIg (P=0.0003), but there was no difference for LQI F_I or LQI F_II. LQI F_III significantly improved in five patients who switched from IVIg to SCIg during the follow-up when compared to patients who pursued the same regimen (either IVIg or SCIg). No difference was found on CHQ-PF50 subscales, LQI F_I, or LQI F_II.

CONCLUSION

Home-based SCIg gave higher satisfaction regarding therapy settings than hospital-based IVIg. No difference was found on other subscales of the LQI or CHQ-PF50 between hospital-based IVIG and home-based SCIG.

Sustained Release of Protein Therapeutics from Subcutaneous Thermosensitive Biocompatible and Biodegradable Pentablock Copolymers (PTSgels)

Objective. To evaluate thermosensitive, biodegradable pentablock copolymers (PTSgel) for sustained release and integrity of a therapeutic protein when injected subcutaneously. Materials and Methods. Five PTSgels with PEG-PCL-PLA-PCL-PEG block arrangements were synthesized. In vitro release of IgG from PTSgels and concentrations was evaluated at 37°C. Released IgG integrity was characterized by SDS-PAGE. In vitro disintegration for 10GH PTSgel in PBS was monitored at 37°C over 72 days using gravimetric loss and GPC analysis. Near-infrared IgG in PTSgel was injected subcutaneously and examined by in vivo imaging and histopathology for up to 42 days. Results. IgG release was modulated from approximately 7 days to more than 63 days in both in vitro and in vivo testing by varying polymer composition, concentration of PTSgel aqueous solution, and concentration of IgG. Released IgG in vitro maintained structural integrity by SDS-PAGE. Subcutaneous PTSgels were highly biocompatible and in vitro IgG release occurred in parallel with the disappearance of subcutaneous gel in vivo. Conclusions. Modulation of release of biologics to fit the therapeutic need can be achieved by varying the biocompatible and biodegradable PTSgel composition. Release of IgG parallels disappearance of the polymeric gel; hence, little or no PTSgel remains after drug release is complete.

Efficacy, Safety, and Pharmacokinetics of a Novel Human Immune Globulin Subcutaneous, 20 % in Patients with Primary Immunodeficiency Diseases in North America

Patients with primary immunodeficiency disease (PIDD) typically require life-long intravenous (IV) or subcutaneous (SC) immunoglobulin (Ig) replacement therapy to prevent recurrent infections. The efficacy, safety, and pharmacokinetics of a highly concentrated (20 %) Ig preparation for SC administration (IGSC 20 %) were evaluated in a prospective trial in patients with PIDD. A total of 74 patients (aged 3-83 years) received 4327 IGSC 20 % infusions over a median of 380.5 days. The rate of validated serious bacterial infections was 0.012 event/patient-year (p < 0.0001 compared with the historical control), and the annualized rate of infection was 2.41 events/patient. Median IgG trough levels were >14.5 g/l. The median maximum infusion rate was 60 ml/h/site (range 4.4-180), resulting in a median infusion duration of 0.95 h. A volume ≥30 ml was infused per site in 74.8 % of IGSC 20 % infusions. Most (84.9 %) infusions were administered using ≤2 infusion sites; for 99.8 % of infusions, there was no need to interrupt/stop administration or reduce the infusion rate. No related serious adverse event (AE) occurred during IGSC 20 % treatment; related non-serious AEs occurred at a rate of 0.036 event/infusion. The incidence of related local AEs was 0.015 event/infusion and of related systemic AEs was 0.021 event/infusion; most were mild in severity, none severe. Increased infusion rates or volumes were not associated with higher AE rates. The investigated IGSC 20 % treatment was shown to be effective and safe, enabling higher infusion rates and volumes per site compared to conventional SC treatments, resulting in fewer infusion sites and shorter infusion durations.

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.