To assess the feasibility of infusions of facilitated subcutaneous immunoglobulin (fSCIG; immunoglobulin infusion with recombinant human hyaluronidase) at a 1.0g/kg target dose via an abbreviated dose ramp-up or no ramp-up versus conventional ramp-up in healthy participants, based on tolerability and safety outcomes.

When transitioning from intravenous to facilitated subcutaneous dosing, dose ramp-up is used to incrementally increase infusion volumes to achieve target doses, acclimating patients to high-volume infusions.

This phase 1, open-label, single-center trial enrolled healthy adults aged 19–50 years (NCT04578535). Participants were assigned into three fSCIG arms (each with a 1.0g/kg target dose): (1) conventional dose ramp-up (0.25g/kg [Week 1] to 1.0g/kg [Week 8]), (2) abbreviated dose ramp-up (0.50g/kg [Week 1] to 1.0g/kg [Week 5]), or (3) 1.0g/kg without ramp-up. fSCIG tolerability (primary endpoint) was assessed as the proportion of participants completing all initiated infusions without interruptions or infusion rate reduction owing to treatment-emergent adverse events (TEAEs). Safety endpoints included the rates of TEAEs per person-year.

Overall, 27 participants were enrolled (mean age 34.9 years); with 8, 9, and 10 participants in the conventional, abbreviated, and no ramp-up arms, respectively. Participants completed all initiated infusions. No discontinuations due to TEAEs occurred but discontinuations were proportionally highest in the no ramp-up group. In total, 69.7, 74.0 and 99.7 TEAEs occurred per person-year in the conventional, abbreviated and no ramp-up arms, respectively. No serious or severe TEAEs occurred.

fSCIG was well-tolerated in healthy adults with or without dose ramp-up at a 1.0 g/kg target dose, but the higher proportion of discontinuations in the no ramp-up arm may provide indirect evidence of better tolerability with ramp-up. The feasibility of abbreviated ramp-up was demonstrated by the lower TEAE rates seen in the dose ramp-up arms. Therefore, administration schedules can be individualized according to physician discretion based on tolerability.