Population pharmacokinetics of immunoglobulin G after intravenous, subcutaneous, or hyaluronidase-facilitated subcutaneous administration in immunoglobulin-naive patients with primary immunodeficiencies.

Immunoglobulin G (IgG) replacement therapy is the standard of care for patients with primary immunodeficiencies with antibody deficiencies. Intravenous (IVIG), subcutaneous (SCIG), and hyaluronidase-facilitated subcutaneous immunoglobulin (fSCIG) therapies differ in their pharmacokinetic (PK) profiles, administration routes, and dosing regimens. Information on use of subcutaneous therapy in IgG treatment-naive patients is limited. This study used population pharmacokinetic (popPK) model-based simulations to characterize IgG PKs in IgG-naive patients with varying disease severity across several IVIG, SCIG, and fSCIG dosing regimens. An integrated popPK model, developed and validated using data from eight clinical trials, was utilized to simulate scenarios that varied by therapy, loading regimen, maintenance dose (equivalent to 400, 600, or 800 mg/kg every 4 weeks [Q4W]), and baseline endogenous total IgG concentration (1.5 or 4.0 g/L). Simulations were performed for age groups of 2-<6, 6-<12, 12-<18, and ≥18 years. Steady-state serum trough IgG concentrations (Cmin,ss), proportion of patients achieving Cmin,ss ≥ 7 g/L, and days taken to reach this threshold were summarized. SCIG provided greater mean Cmin,ss values than IVIG and fSCIG for any scenario. Across all therapies, Cmin,ss tended to increase with age, dose, and endogenous concentration. Although the findings are model-based and not a summarization of real-world observations, doses ≥ 800 mg/kg Q4W with corresponding loading regimens are likely to be clinically appropriate for achieving target IgG concentrations in treatment-naive patients in a timely manner, especially at low endogenous starting concentrations. Therapy-specific dose adjustment based on baseline endogenous IgG concentration, clinical status, and patient characteristics may be warranted.

Population Pharmacokinetics of Nirsevimab in Preterm and Term Infants.

Nirsevimab, a monoclonal antibody with an extended half-life, is approved for the prevention of respiratory syncytial virus (RSV) disease in all infants in Canada, the EU, Great Britain, and the USA. A population pharmacokinetics (PK) model was built to describe the PK of nirsevimab in preterm and term infants, and to evaluate the influence of covariates, including body weight and age, in infants. Nirsevimab PK was characterized by a 2-compartment model with first-order clearance (CL) and first-order absorption following intramuscular (IM) administration. The typical CL in a 5 kg infant was 3.4 mL/day. Body weight and postmenstrual age were the primary covariates on CL, with minor effects for race, second RSV season, and antidrug antibody status (deemed not clinically relevant). Congenital heart disease (CHD) and chronic lung disease (CLD) did not significantly impact nirsevimab PK. The final population PK model, based on 8987 PK observations from 2683 participants across 5 clinical trials, successfully predicted PK in an additional cohort of 967 healthy infants. Weight-banded dosing (50 mg in infants <5 kg; 100 mg in infants ≥5 kg) was predicted to be appropriate for infants ≥1 kg in their first RSV season. Together, these data support weight-banded dosing of nirsevimab in all infants in their first RSV season, including in healthy infants, infants with CHD or CLD, and in infants born prematurely.

Effects of Body Mass and Age on the Pharmacokinetics of Subcutaneous or Hyaluronidase-facilitated Subcutaneous Immunoglobulin G in Primary Immunodeficiency Diseases.

PURPOSE: To assess the pharmacokinetics (PK) of subcutaneous immunoglobulin (SCIG) and hyaluronidase-facilitated SCIG (fSCIG) therapy across body mass index (BMI) and age categories in patients with primary immunodeficiency diseases (PIDD) previously treated with intravenous immunoglobulin (IVIG). METHODS: Using our previously published integrated population PK model based on data from eight clinical trials, simulations were conducted to examine the effects of BMI and age on serum immunoglobulin G (IgG) PK after administration of SCIG 0.15 g/kg weekly or fSCIG 0.6 g/kg every 4 weeks in patients switching from stable IVIG. Patients were assumed to have baseline IgG trough concentrations of 7 g/L (hypothetical protective threshold). RESULTS: Mean steady-state serum IgG trough values (Cmin,ss or trough) increased with BMI and age. Mean Cmin,ss was 18% (SCIG) and 16% (fSCIG) higher in the obese than the healthy BMI group. Pediatric patients aged < 18 years had 8-22% (SCIG) and 4-20% (fSCIG) lower mean Cmin,ss values than adults, with the youngest group (2- < 6 years) having the lowest Cmin,ss. All patients across populations maintained Cmin,ss IgG concentrations of ≥ 7 g/L after switching to SCIG or fSCIG. CONCLUSION: Both SCIG and fSCIG successfully maintained trough values at or above the hypothetical protective threshold after switching from stable IVIG, irrespective of BMI or age. Differences in trough values between BMI groups and age groups (≤ 22%) may not warrant SCIG or fSCIG dose adjustments based on BMI or age alone; instead, the dosing paradigm should be guided by prior IVIG dose, individual IgG monitoring, and clinical findings.

Integrated population pharmacokinetics of immunoglobulin G following intravenous or subcutaneous administration of various immunoglobulin products in patients with primary immunodeficiencies.

Plasma-derived immunoglobulin G (IgG) replacement therapy represents the current standard of care for patients with primary or secondary antibody deficiencies, and includes intravenous (IVIG), subcutaneous (SCIG) and facilitated subcutaneous (fSCIG) immunoglobulin products. A holistic understanding of the pharmacokinetics (PK) of IgG for these therapies is key to optimizing their clinical use. We developed an integrated population PK model using non-linear mixed-effects modeling based on data from eight clinical trials (each ≥ 1 year duration; n = 384 patients), which simultaneously characterized IgG PK profiles of IVIG, SCIG or fSCIG in patients with primary immunodeficiencies and identified covariate effects. The final model was a two-compartment turnover model incorporating: the endogenous production of IgG with linear subcutaneous absorption and a product effect on bioavailability; additive and proportional error; between-patient variability on clearance and central volume of distribution; and allometric scaling with lean body mass on clearance, intercompartmental clearance and central and peripheral volumes of distribution. Overall, the model adequately described IgG PK profiles, with residual standard error values < 28 % for all PK parameters. Goodness-of-fit plots and prediction-corrected visual predictive checks indicated a good fit of the observed IgG PK profiles. This integrated PK model has enabled a comprehensive understanding of IgG PK profiles for various immunoglobulin products, and will provide a framework for future investigations of IgG PK with different dosing regimens and in special or wider patient populations of interest.

Off camera.

Wearing body cameras at work is a terrible idea, especially in settings where establishing a trusting therapeutic relationship is vital (readers' panel, 14 June).

Shetland is where it's at.

There are so many challenges facing nurses and healthcare. From funding cuts to public health, the picture is dishearteningly complex. No wonder many would be tempted to disappear to a remote island.

A final reflection on my time as a nursing student.

In his final Student Column, Ed Freshwater looks back over the 3 years of his degree considering the things that went well, and the things he might have done differently.

Saying the wrong thing.

Ed Freshwater discusses the perils of social media and the boundaries that separate compassion and professionalism. Whatever you do, he says, never add patients as friends on Facebook!

Students: you are the future of nursing.

Now that his BSc in Mental Health Nursing is drawing to a close, Ed Freshwater considers his options, from professional development to a Master's degree.

Keeping an eye on things.

Whether you're steering clear of buses, watching your children play, or measuring the weight of your patients, there's no substitute for the power of observation, writes Ed Freshwater.