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Facilitated subcutaneous immunoglobulin (fSCIG) 10% is an immunoglobulin replacement therapy that utilizes recombinant human hyaluronidase (rHuPH20) to enhance immunoglobulin dispersion and absorption, allowing for longer treatment intervals similar to intravenous immunoglobulin (up to once monthly). fSCIG 10% is indicated in the USA for treating adults and children aged ≥ 2 years with primary immunodeficiency diseases (PIDs). This prospective, non-interventional, open-label, multicenter, post-authorization safety study (NCT02593188) was conducted in the USA from November 2015 to October 2021 to assess the long-term safety of fSCIG 10% in routine clinical practice. Patients with PIDs aged ≥ 16 years who were prescribed and/or had started fSCIG 10% treatment were enrolled. In total, 253 patients were enrolled and included (full analysis set). Participants received fSCIG 10% treatment for a median (interquartile range) of 10.0 (3.5-11.8) months, with the majority of infusions administered every 4 weeks (54.4% [1197/2201 infusions]) and at home (62.6% [1395/2230 infusions]). Overall, 98.5% of infusions were administered without rate reduction, interruption, or discontinuation due to adverse events (AEs). Treatment-related, non-serious AEs were experienced by 52 patients (20.6%, 284 events). Two patients (0.8%) each experienced one treatment-related serious AE (aseptic meningitis and deep vein thrombosis). Development of antibodies against rHuPH20 was uncommon; 14/196 patients (7.1%) tested positive for binding antibodies (titer ≥ 1:160) with no neutralizing antibodies detected. There was no relationship between anti-rHuPH20 antibody positivity and the occurrence of treatment-related serious or non-serious AEs. Long-term, repeated self-administration of fSCIG 10% was well tolerated in US clinical practice by patients with PIDs.

OBJECTIVE: Multifocal motor neuropathy is a rare chronic immune-mediated neuropathy with impaired grip strength representing a common symptom. While intravenous immunoglobulin G is an effective treatment for the disease, significant variation in treatment response has been observed but not well understood. This analysis characterized dose-exposure-response relationships in multifocal motor neuropathy, using grip strength as a clinical efficacy measure. METHODS: Serum immunoglobulin G trough concentrations and grip strength data for the more affected hand from a Phase 3, randomized, double-blind, placebo-controlled, crossover trial of intravenous immunoglobulin 10% in 44 patients with multifocal motor neuropathy (NCT00666263) were used to develop a population pharmacokinetic-pharmacodynamic model. RESULTS: The model adequately described the observed pharmacokinetic and pharmacodynamic data and relationships between intravenous immunoglobulin 10% dose, serum immunoglobulin G trough levels, grip strength, and inter-patient variabilities in multifocal motor neuropathy. Model-based simulations for various dosing regimens (0.4-2.0 g/kg every 2-4 weeks) indicated that ≥1.6 g/kg/month would achieve clinically meaningful improvements in grip strength (≥4 kg) in ≥70% of patients. More frequent dosing at an equivalent monthly dose led to a more consistent response in grip strength. Furthermore, splitting the dose over multiple days for high doses (>1 g/kg) did not impact grip strength. INTERPRETATION: These findings suggest that the majority of patients with multifocal motor neuropathy would respond rapidly to intravenous immunoglobulin 10% with a range of dosing regimens. Shorter dosing intervals may avoid the diminishing response seen with longer dosing intervals. Dose-splitting provided similar outcomes while offering flexibility and convenience.

PURPOSE: Facilitated subcutaneous immunoglobulin (fSCIG; immune globulin infusion 10% [human] with recombinant human hyaluronidase [rHuPH20]) permits high-volume subcutaneous immunoglobulin (SCIG) infusion, shorter infusion times and reduced dosing frequency relative to conventional SCIG. It is initiated by gradually increasing infusion volumes over time (dose ramp-up) to achieve target dose level (TDL). Whether ramp-up strategies have tolerability or safety advantages over direct initiation at full TDL has not been evaluated clinically. METHODS: This phase 1 open-label study assessed tolerability and safety of fSCIG 10% with accelerated or no ramp-up compared with conventional ramp-up in healthy adults (NCT04578535). Participants were assigned to one of the three ramp-up arms to achieve TDLs of 0.4 or 1.0 g/kg/infusion. The primary endpoint was the proportion of infusions completed without interruption or infusion rate reduction owing to treatment-emergent adverse events (TEAEs). Safety was assessed as a secondary endpoint. RESULTS: Of 51 participants enrolled, 50 (98.0%) tolerated all fSCIG 10% infusions initiated (n = 174). Infusion rate was reduced in one participant owing to headache in the 0.4 g/kg/infusion conventional ramp-up arm. Study discontinuations were higher in the no ramp-up arm (70%) versus the conventional (0%) and accelerated (22%) arms at the 1.0 g/kg/infusion TDL. Safety outcomes did not substantially differ between treatment arms. CONCLUSION: The favorable tolerability and safety profiles of fSCIG 10% in healthy participants support initiating treatment with fSCIG 10% with accelerated ramp-up at TDLs up to 1.0 g/kg. Data support no ramp-up at TDLs close to 0.4 g/kg but additional data are needed for higher doses.