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We report here the results of a phase 3 study to assess the efficacy, safety, and tolerability of GC5107, a new 10% liquid intravenous immunoglobulin (IVIG) in preventing serious bacterial infections in patients with primary immunodeficiency (ClinicalTrials.gov: NCT02783482). Over a 12-month study period, 49 patients aged 3 to 70 years with a confirmed diagnosis of primary immunodeficiency received GC5107 at doses ranging from 319 to 881 mg/kg body weight every 21 or 28 days, according to their previous IVIG maintenance therapy. A total of 667 infusions of GC5107 were administered comprising a total of 45.86 patient-years of treatment. A single acute serious bacterial infection occurred during the study, resulting in an incidence of 0.02 events per patient-year (upper 99% one-sided confidence interval limit: 0.21), meeting the prespecified primary efficacy endpoint. The mean incidence of infections other than acute serious bacterial infections was 2.9 infections per patient-year. Efficacy was also demonstrated by the low mean annualized rate of hospitalizations due to infection (0.1 day) and the mean annualized duration of hospitalizations (0.1 day). The mean rate of intravenous and oral antibiotic use was 0.1 day and 13.2 days, respectively. There was a mean of 7.1 days of missed work, school, or daycare days. The proportion of infusions with temporally associated adverse events (TAAEs) occurring during or within 72 hours after GC5107 infusion was 0.24 (upper 95% one-sided confidence interval limit: 0.31), meeting the pre-specified primary safety endpoint. Overall, 149 of 667 infusions (22%) were associated with TAAEs. The most common TAAE was headache, reported by 49% of patients. More than 98% (731/743) of all adverse events that occurred throughout the 12-month study period were mild or moderate. More than 98% of infusions were completed without discontinuation, interruption or rate reduction. There were no treatment-emergent serious adverse events related to GC5107 or study discontinuations due to an adverse event. Overall, pharmacokinetic parameters for GC5107 were within the range of those reported in studies of other marketed IVIG products. Results of the present study demonstrate that GC5107 is an effective, safe and well-tolerated treatment for patients with primary immunodeficiency., Competing Interests: AE has participated in advisory boards for ALK Abello, AstraZeneca, Aralez, Bausch Health, LEO Pharma, Merck, Novartis, and Pfizer; has served as a speaker for ALK Abello, The ACADEMY, Aralez, AstraZeneca, Medexus, and Mylan; and has been a consultant to Bayer LLC and Regeneron. Her institution has received research grants from ALK Abello, Aralez, AstraZeneca, Bayer LLC, GC Pharma, Medexus, Novartis, Sanofi and Regeneron. WL has served as a consultant for Accordant, BioCryst, Biomarin, CSL Behring, Express Scripts, Fresenius Kabi, Intellia, Kalvista, Magellan, Optum, Pharming, Pharvaris, and Shire/Takeda; serves as a speaker for BioCryst, CSL Behring, Pharming, Shire/Takeda, Grifols, Astra Zeneca, Sanofi/Regeneron and GSK; and receives grants or research support from ALK, BioCryst, CSL Behring, Gossamer, GC Pharma, Grifols, Ionis, Kalvista, Kedrion, Shire/Takeda and Therapure. He is a member of the US Hereditary Angioedema Association Medical Advisory Board. RW serves as an investigator for CSL Behring, Grifols, Kedrion, GC Pharma, Takeda, and TherapureBio; serves as a consultant for ADMA Biologicals, Grifols, GC Pharma, Takeda, and TherapureBio; and serves as a speaker for CSL Behring, Grifols, and Takeda. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The authors declare that this study received funding from GC Pharma, Korea. The funder was involved in the study design, analysis and interpretation of data, review of the manuscript, and the decision to submit the manuscript for publication., (Copyright © 2021 Perez, Hébert, Ellis, Alpan, Lumry, Shapiro, Suez, Mandujano and Wasserman.)

Introduction: HyQvia (Immune Globulin Infusion 10% [Human] with Recombinant Human Hyaluronidase) was developed to combine the advantages of intravenous and subcutaneous immune globulin (SCIG), allowing administration of larger volumes at a single subcutaneous site with less frequent dosing when compared to other SCIG products. Current US prescribing guidelines for HyQvia are limited to adults and do not encompass the flexibility required to achieve success in all patients with primary immunodeficiency (PID)., Methods: This retrospective study was designed to evaluate the clinical experience of treating patients with PID with HyQvia regimens outside of package insert recommendations as well as in pediatric patients. Data were abstracted from 38 patient records (317 HyQvia infusions), including five patients less than 16 years of age, from seven US immunology clinics., Results: Among 37 patients receiving HyQvia regimens differing from prescribing guidelines, the most notable variations included shorter ramp-up periods, use of two rather than one infusion site, and slower than maximal infusion rates to mitigate local adverse events (AEs). The medication volume infused for single site doses ranged from 75 to 200 mL and doses split between two sites ranged from 100 to 750 mL. The most common type of regimen variation was a condensed ramp-up phase (shorter schedule, higher doses), and 96% (24/25) of patients managed in this way completed ramp-up. The most common ramp-up schedule was three infusions (one at 25-45%, another at 50-75%, and the final at 100% of target dose) spread over 2-4 weeks., Conclusions: A shorter ramp-up schedule did not appear to increase the number of AEs compared to standard ramp-up schedules. For patients with AEs, slower infusion rates and the use of two sites may improve medication tolerability. Four of five pediatric patients reported no AEs, and only one discontinued, stating a fear of needles. HyQvia may be tailored to adults requiring alternative rates, ramp-up, and/or dosing regimens and may be especially well-suited to children.

Many patients with primary immunodeficiency (PID) require immunoglobulin G (IgG) replacement therapy, delivered as intravenous IgG (IVIG) or subcutaneous IgG (SCIG). We aim to identify trends in efficacy and safety that would not be evident in individual studies of small patient numbers. Seven open-label, Phase 3, prospective, multicenter studies of the efficacy and safety of Hizentra® (a SCIG), conducted in Japan, Europe, and the US were summarized. Overall, 125 unique patients received 15,013 weekly infusions during a total observation period of 250.9 patient-years. Mean weekly doses of Hizentra® were 83.22-221.3 mg/kg body weight; infusion rates per patient (total body rate) were 25.2-49.3 mL/h across studies. The rates of infections and serious bacterial infections were 3.10 and 0.03 events per patient/year, respectively. Annualized rates of days hospitalized due to infection, out of work/school, and prophylactic antibiotic use were 0.95, 5.14, and 36.78 per patient, respectively. For the equivalent monthly dose, weekly Hizentra® SCIG administration resulted in expectedly-increased serum IgG trough levels in patients switching from IVIG, and maintained levels in patients switching from previous SCIG. Adverse events (AEs) totaled 5039 (events/infusion 0.094-0.773), almost all of which were mild/moderate. Three thousand one hundred ninety-seven were considered treatment-related, the most common of which were injection site reactions (2919 events; 0.001-0.592 AEs per infusion). Systemic AEs were very uncommon. The results from these seven studies indicate that Hizentra® therapy was both efficacious and well tolerated during long-term treatment. This is particularly important in patients with PID, who may require lifelong IgG replacement therapy.

Immunoglobulin (IgG) replacement therapy has been the cornerstone of treatment for primary immunodeficiency disease for nearly 60 years. During this time, research has continually refined the target IgG trough level and IgG replacement dosages to allow patients with primary immunodeficiency disease to achieve effective protection from infection. Manufacturers have also improved IgG formulations to allow patients to receive clinically beneficial dosages of IgG replacement with improved safety and tolerability. This review will introduce Hizentra(®), a highly concentrated (20%) IgG solution for subcutaneous (sc.) infusion, discuss its manufacturing process and pharmacokinetic profile and review its tolerability and efficacy data as evaluated in clinical trials. New highly concentrated sc. IgG products may improve patient quality of life and adherence to therapy because of the flexible dosing options, fewer infusion sites and less infusion time, compared with less concentrated sc. IgG products, resulting in favorable patient outcomes consistent with higher steady-state IgG levels.

Hizentra(®) (20% subcutaneous immunoglobulin [SCIG]) was administered to subjects with primary immunodeficiency disease in two extension studies in the EU and US to assess long-term efficacy and tolerability. Subjects (aged 4-69 years) were treated for 148 weeks in the EU (N = 40; 5405 infusions) and 87 weeks in the US (N = 21; 1735 infusions). Weekly doses were 116.0 mg/kg (EU) and 193.2 mg/kg (US); IgG levels were 7.97 g/L (EU) and 11.98 g/L (US). Annualized rates of serious bacterial infections were 0.05 infections/subject/year (EU) and 0.06 infections/subject/year (US). Rates of any infection were 3.33 infections/subject/year (EU) and 2.38 infections/subject/year (US). The rate of bronchopulmonary infections was higher in the EU study. No treatment-related serious AEs occurred; no subject discontinued because of treatment-related AEs. Self-administered Hizentra afforded sustained effective protection from infections and favorable tolerability during an extended treatment period of up to 3 years., (© 2013.)

Subcutaneous administration of immunoglobulin (IGSC) in a home setting, compared with intravenous administration, can improve patient quality of life. During IGSC, however, the subcutaneous extracellular matrix inhibits flow and fluid entry into the vascular compartment, which limits the amount of drug delivered. Recombinant human hyaluronidase (rHuPH20) increases the absorption and dispersion of infused fluids and drugs. Results from a Phase III, prospective, open-label, noncontrolled study of patients with primary immunodeficiencies indicated that IGSC infusion, facilitated by rHuPH20, is well tolerated and delivers infusion volumes at treatment intervals and rates equivalent to intravenous administration. This drug evaluation provides an overview of rHuPH20 and results of clinical studies of IGSC infusion facilitated by rHuPH20 in patients with primary immunodeficiencies.

The importance of serum immunoglobulin (Ig)G concentration in IgG replacement therapy for primary immunodeficiency diseases is established in certain settings. Generally, IgG is infused via the intravenous (IVIG) or subcutaneous (SCIG) route. For IVIG infusion, published data demonstrate that higher IgG doses and trough levels provide patients with improved protection from infection. The same conclusions are not yet accepted for SCIG; data from two recent Phase III studies and a recent post-hoc analysis, however, suggest the same correlation between higher SCIG dose and serum IgG concentration and decreased incidence of infection seen with IVIG. Other measures of clinical efficacy have not been considered similarly. Thus, combined analyses of these and other published SCIG studies were performed; a full comparison of the 13 studies was, however, limited by non-standardized definitions and reporting. Despite these limitations, our analyses indicate that certain clinical outcomes improve at higher SCIG doses and associated higher serum IgG concentrations, and suggest that there might be opportunity to improve patient outcomes via SCIG dose adjustment., (© 2012 The Authors. Clinical and Experimental Immunology © 2012 British Society for Immunology.)

Privigen(®) (immune globulin intravenous [human], 10% liquid) and Hizentra(®) (immune globulin subcutaneous [human], 20% liquid) are stabilized by proline. The clinical implications of administering proline-containing immunoglobulin products to patients with defects of proline metabolism have not been addressed; Privigen and Hizentra are contraindicated in these patients. Some patients with chromosome 22q11.2 deletion syndrome have elevated proline levels; however, only 3-4% of patients also have an immunodeficiency that requires IgG therapy. This review summarizes the evidence related to the safety and pharmacokinetics of proline assessed in Privigen and Hizentra preclinical and clinical studies, and subsequent implications for patients with defects in proline metabolism. Clinical data indicate that proline does not accumulate after Privigen or Hizentra treatment and is not associated with adverse events. There is no evidence to suggest that patients with defects of proline metabolism would be affected by transient elevations in plasma proline following Privigen and/or Hizentra treatment.

A multi-center, prospective, open-label study was conducted in primary immunodeficiency disease patients to determine the tolerability and pharmacokinetics of a 10% liquid IgG preparation administered subcutaneously. Forty-nine subjects (3-77 years old) were enrolled. Pharmacokinetic equivalence of subcutaneous treatment was achieved at a median dose of 137% of the intravenous dose, with a mean trough IgG level of 1,202 mg/dL at the end of the assessment period. The overall infection rate during subcutaneous treatment was 4.1 per subject-year. Three acute serious bacterial infections were reported, resulting in a rate of 0.067 per subject-year. A low overall rate of temporally associated adverse events (8%), and a very low rate of infusion site adverse events (2.8%), was seen at volumes up to 30 mL/site and rates ≤ 30 mL/h/site. Thus, subcutaneous replacement therapy with a 10% IgG preparation proved effective, safe and well-tolerated in our study population of subjects with primary immunodeficiency disease.

Background and Objectives: Immunoglobulin replacement is a standard therapy for patients with primary immunodeficiencies. Subcutaneous administration of immunoglobulin offers more constant IgG levels than intravenous administration and simplifies administration for some patients. Use of L-proline as an excipient contributes to the stability of highly concentrated IgG preparations. The aims of the present study were to evaluate the pharmacokinetics of IgPro20 (Hizentra®), a new 20% subcutaneous IgG solution, and compare the area under the serum concentration-time curve (AUC) with that of a similar intravenous 10% IgG solution (IgPro10; Privigen®). At the request of the US FDA, an algorithm for determining IgG trough level ratios (TLRs) was developed in order to provide physicians with a practical tool for monitoring doses during steady-state IgPro20 therapy., Methods: This was a prospective, open-label, multicentre, single-arm, phase III clinical trial conducted in the US. The study was performed in a primary-care setting. Eligible patients were males or females aged 6-75 years with a primary immunodeficiency (common variable immunodeficiency or X-linked agammaglobulinaemia) who had received regular treatment with IgPro10 for at least 3 months prior to entering this study and had achieved serum trough concentration (C(trough)) values ≥5 g/L. IgPro20 was administered subcutaneously once weekly at initial doses equivalent to 130% of patients' previous doses, based on the results obtained in a Vivaglobin® study and due to an FDA request. After run-in, each patient's dose was adjusted to achieve an AUC comparable to that achieved with IgPro10 administered intravenously., Results: Eighteen patients completed the study. Mean IgPro20 : IgPro10 dose ratio (dose adjustment coefficient) was 1.53 (range 1.26-1.87). The resulting mean AUCs were 105.6 g · day/L for IgPro20 versus 103.2 g · day/L for IgPro10 (geometric mean ratio 1.002; lower one-sided 95% confidence limit [CL] 0.951). Thus, the primary endpoint of the study was met, as this result exceeded the pre-specified criterion of the lower one-sided 95% CL of ≥0.8 for non-inferiority. At these AUCs, which were considered equivalent, the mean IgPro20 : IgPro10 TLR, determined by the developed algorithm, was 1.29 (range 1.18-1.73). Titres of specific antibodies tested were well above respective product specifications, suggesting that protection against infection would be effective., Conclusion: Steady-state AUCs with subcutaneous IgPro20 and intravenous IgPro10 were equivalent. Mean dose adjustment coefficient and mean TLR can be used for initial dose conversion without risk of under-protection but vary too widely to be considered measures of equivalence. Trial registration number (clinicaltrials.gov): NCT00419341.

Subcutaneous administration of intravenous immunoglobulin G (IgG) preparations provides an additional level of patient convenience and more options for patients with poor venous access or a history of intravenous IgG reactions. An open-label, pharmacokinetic trial (n = 32) determined the non-inferiority of the subcutaneous versus intravenous route of 10% caprylate/chromatography purified human immune globulin intravenous (IGIV-C; Gamunex®) administration by comparing the steady-state area under the concentration-versus-time curve (AUC) of total plasma IgG in patients with primary immunodeficiency disease. Patients on stable IGIV-C received two intravenous infusions (administered 3 or 4 weeks apart). Seven to 10 days after the second intravenous infusion, all patients switched to a weekly infusion of subcutaneous IGIV-C, with the dose equal to 137% of the previous weekly equivalent intravenous dose, for up to 24 weeks. Samples for pharmacokinetic analysis were collected during steady state for intravenous and subcutaneous IGIV-C treatments. The AUC(0-) τ geometric least-squares mean ratio was 0·89 (90% confidence interval, 0·86-0·92) and met the criteria for non-inferiority. The overall mean steady-state trough concentration of plasma total IgG with subcutaneous IGIV-C was 11·4 mg/ml, 18·8% higher than intravenous IGIV-C (9·6 mg/ml). Subcutaneous IGIV-C was safe and well tolerated. Subcutaneous IGIV-C infusion-site reactions were generally mild/moderate and the incidence decreased over time. No serious bacterial infections were reported. Weekly subcutaneous IGIV-C infusion using 137% of the weekly equivalent intravenous immunoglobulin dose provides an AUC comparable to intravenous administration, thus allowing patients to maintain the same IgG preparation/formulation if switching between intravenous and subcutaneous infusions., (© 2010 British Society for Immunology.)

Immunoglobulin (Ig) administration via the subcutaneous (s.c.) route has become increasingly popular in recent years. The method does not require venous access, is associated with few systemic side effects and has been reported to improve patients' quality of life. One current limitation to its use is the large volumes which need to be administered. Due to the inability of tissue to accept such large volumes, frequent administration at multiple sites is necessary. Most studies conducted to date have investigated the use of subcutaneous immunoglobulin (SCIg) in patients treated previously with the intravenous (i.v.) formulation. New data now support the use of s.c. administration in previously untreated patients with primary immunodeficiencies. SCIg treatment may further be beneficial in the treatment of autoimmune neurological conditions, such as multi-focal motor neuropathy; however, controlled trials directly comparing the s.c. and i.v. routes are still to be performed for this indication. New developments may further improve and facilitate the s.c. administration route. For example, hyaluronidase-facilitated administration increases the bioavailability of SCIg, and may allow for the administration of larger volumes at a single site. Alternatively, more concentrated formulations may reduce the volume required for administration, and a rapid-push technique may allow for shorter administration times. As these developments translate into clinical practice, more physicians and patients may choose the s.c. administration route in the future.

The complete amino acid and nucleotide sequences of the variable regions of the heavy and light polypeptide chains of a human neutralizing IgGl anti-cytomegalovirus (CMV) antibody reveal a striking homology to IgM rheumatoid factors (RFs) of the Wa idiotypic family. The anti-CMV antibody and Wa RFs have in common VKIIIb, JKl, and VHIa gene segments but use different DH and JH gene segments. The anti-CMV antibody does not have RF activity and does not express the Wa idiotype. The Wa RFs do not have anti-CMV activity. A subset of Wa RFs, however, and the anti-CMV antibody do share several idiotypes on the VHIa and VKIIIb polypeptides. Since there are major differences in the antigen binding characteristics and some of the other expressed idiotypes, these data suggest that the D and J region amino acids are crucial to such specificities. Although the use of such highly homologous gene segments in different immune responses is well-documented in murine systems, these data represent the first such example in the human.