Efgartigimod works through an elegant molecular trick. It is a human immunoglobulin G1 (IgG) antibody Fc fragment, engineered to bind with unusually high affinity to the neonatal Fc receptor (FcRn), the cellular recycling machinery that normally protects IgG antibodies from degradation and gives them their characteristically long half-life in the bloodstream. By occupying FcRn, efgartigimod interrupts this recycling loop, so circulating IgG, including the pathogenic autoantibodies that drive diseases like gMG and CIDP, is cleared faster. Importantly, the drug does not suppress antibody production or blunt immune responses to vaccination, and it does not lower albumin levels or raise cholesterol, distinguishing it from broadly immunosuppressive therapies such as glucocorticoids, azathioprine, mycophenolate mofetil, or B cell-depleting agents.

The original subcutaneous formulation contained a fixed 1000-mg dose of efgartigimod at 180 mg/ml in a 5.6-ml volume, supplied in a single-dose vial that a health care provider had to draw up with a separate syringe. The new prefilled syringe packs the same 1000-mg dose into 5.0 ml at a higher concentration of 200 mg/ml, and it was approved in the United States in April 2025 for adults with acetylcholine receptor autoantibody-positive generalized myasthenia gravis and for adults with CIDP. The coformulation with recombinant human hyaluronidase PH20 is what makes such a large subcutaneous volume feasible: the enzyme locally depolymerizes hyaluronan in the subcutaneous space, temporarily dissolving the structural barrier to bulk fluid flow so the drug can disperse and be absorbed more readily.

The first question the researchers tackled was whether the prefilled syringe is pharmacologically interchangeable with the vial-and-syringe presentation. In a Phase 1, open-label, randomized, two-period crossover bioequivalence study (ClinicalTrials.gov identifier NCT05817435), 72 healthy participants each received a single health care provider-administered injection by both routes, serving as their own controls. Serum efgartigimod concentrations were measured with a validated ligand-binding electrochemiluminescence immunoassay with a lower limit of quantification of 200 ng/ml, and the primary endpoints were the maximum observed concentration (Cmax) and the area under the concentration-time curve from zero to infinity (AUC0-inf).

The bioequivalence criterion was met decisively. The 90 percent confidence intervals for the geometric least-squares mean ratios of both Cmax and AUC0-inf fell entirely within the predefined acceptance range of 80.0 to 125.0 percent, the regulatory standard for demonstrating that two formulations deliver equivalent systemic exposure. After injection, efgartigimod concentrations rose to a plateau, with a median time to peak concentration of 48.0 hours for the prefilled syringe versus 72.0 hours for the vial and syringe, and individual values ranging from 12.0 to 119.3 hours. Once the plateau was reached, serum concentrations declined gradually with similar half-lives for both presentations, and other pharmacokinetic parameters were likewise comparable between the two arms.

Safety in the bioequivalence study was reassuring. The drug was well tolerated by both routes, with no fatal or serious adverse events and no discontinuations attributed to adverse events. A single grade 3 or higher event, a blood pressure increase in one participant who received the vial-and-syringe formulation, was judged unrelated to treatment. Injection site reactions occurred in 50.7 percent of participants using the prefilled syringe and 59.7 percent using the vial and syringe, all of grade 1 or 2 severity, and all resolved by the end of the study except one that was resolving. A post hoc analysis showed mean injection durations of roughly 31 seconds in both groups, and no anaphylactic or hypersensitivity reactions were observed.

A second Phase 1 study asked a deceptively simple question: how fast can a large, viscous subcutaneous volume be pushed without causing problems? All 48 randomized healthy participants completed this randomized, open-label crossover trial, in which efgartigimod PH20 SC was delivered over 20, 30, 45, or 60 seconds using an infusion pump with a disposable syringe and a 27-gauge ultra-thin-wall needle. Every participant across every speed group received at least 90 percent of the full injection volume in both dosing periods, and mean fluid leakage or backflow at the injection site was negligible and essentially identical across groups, at 0.0122 ml in the first period and 0.0085 ml in the second. More than 87 percent of participants said one hour after injection that they would be willing to receive the administration again, local pain scores dropped significantly within five minutes across all speed groups, and all adverse events were mild to moderate, with no serious events or discontinuations.

The third component comprised two human factors validation studies, designed according to US Food and Drug Administration guidance for combination products, that tested whether real users could handle the device safely. Fifteen participants with gMG, fifteen with CIDP, and fifteen lay caregivers of family members with these diseases were given the prefilled syringe and its instructions for use, but no training whatsoever. In a simulated home environment, each participant stored the device overnight and then performed an unaided simulated injection into an injection pad, placed over their own clothes for patients or on a manikin for caregivers. The results were striking: all 45 participants successfully refrigerated, prepared, injected, and disposed of the prefilled syringe, delivering the full dose in an average of 30 seconds, with no performance differences between patients and caregivers and no use errors that could cause harm. All 45 also correctly located and identified 28 pieces of critical safety information in the instructions, and every participant said they believed they could give weekly injections with the product if needed.

The authors acknowledge one methodological caveat: the injection speed study used an infusion pump rather than the prefilled syringe device itself, which prevents firm conclusions about the optimal speed of the PFS specifically. However, the formulation tested had the same volume and viscosity as that used in the bioequivalence and human factors studies, which did employ the device, so the data collectively support the feasibility and safety of a rapid, roughly 30-second injection of efgartigimod PH20 SC in general. The researchers also note that the studies were funded by argenx, the drug’s developer, and that several of the authors are company employees, factors readers should weigh when interpreting the uniformly positive findings.

Even with those caveats, the implications for patients are substantial. For chronic conditions like gMG and CIDP, where treatment continues indefinitely, aligning therapy with patient preferences for route of administration has been linked to greater satisfaction, better quality of life, and improved adherence. A prefilled syringe eliminates the steps of vial handling and dose drawing, improves dosing accuracy, and particularly benefits patients with impaired manual dexterity, coordination, or vision, while reducing health care resource utilization and waste. Taken together, the bioequivalence, injection speed, and human factors data indicate that a rapid, high-volume subcutaneous injection of efgartigimod PH20 from a prefilled syringe is safe, feasible, and usable, offering patients and their caregivers a quick, flexible option for receiving treatment either in a clinic or at home, and potentially easing the daily burden of living with IgG-mediated autoimmune disease.

Subject of Research: Pharmacokinetics, injection speed, and usability of a prefilled syringe for subcutaneous efgartigimod PH20 in IgG-mediated autoimmune diseases

Article Title: Investigating the Pharmacokinetics, Injection Speed, and Usability of Subcutaneous Efgartigimod PH20 Administered with a Prefilled Syringe

Article References: De Muynck, C., Noukens, J., Allosery, K., Cettour-Rose, C., Pastouret, S., Andre, A. D., & Borgions, F. (2026). Investigating the Pharmacokinetics, Injection Speed, and Usability of Subcutaneous Efgartigimod PH20 Administered with a Prefilled Syringe. Advances in Therapy. https://doi.org/10.1007/s12325-026-03733-x

Image Credits: AI Generated

DOI: 10.1007/s12325-026-03733-x

Keywords: efgartigimod, prefilled syringe, bioequivalence, myasthenia gravis, CIDP, neonatal Fc receptor, hyaluronidase PH20, subcutaneous injection, pharmacokinetics, human factors study, autoimmune disease, self-administration

Mitogen-activated protein kinases, or MAPKs, are a family of signaling enzymes that operate inside virtually every cell of the body. When a cell receives an external cue, such as a stress signal, a cytokine, or an antigen encounter, these kinases relay the message from the cell surface to the nucleus by a chain reaction of phosphorylation events. The family includes three major branches: p38, which is strongly associated with inflammation and cellular stress responses; extracellular signal-regulated kinase (ERK), which typically drives proliferation and differentiation; and c-Jun N-terminal kinase (JNK), which responds to stress and can trigger programmed cell death. Because immune cells rely heavily on these cascades to orchestrate their activation and effector functions, researchers have long suspected that MAPK signaling might be disturbed in autoimmune diseases, including those affecting the peripheral nerves.

The Belgrade team, led by Marina Stamenkovic and Irena Vukovic as co-first authors under the supervision of Vladimir Trajkovic and Verica Paunovic, went beyond the MAPK family to examine a broader metabolic network. They also measured the activity of AMP-activated protein kinase (AMPK), an intracellular energy sensor that switches cells into conservation mode when fuel is scarce, and mechanistic target of rapamycin complex 1 (mTORC1), the master growth regulator that AMPK antagonizes. Together, these pathways govern autophagy, the cellular recycling process by which cells digest their own damaged components. Autophagy has emerged in recent years as a critical regulator of immune cell behavior, and earlier work by some of the same investigators had linked reduced AMPK signaling in blood mononuclear cells to the severity of Guillain-Barré syndrome, another immune-mediated neuropathy.

To test whether these pathways are altered in chronic immune neuropathies, the researchers collected peripheral blood mononuclear cells, the mixed population of lymphocytes and monocytes that circulates in the bloodstream, from 17 patients with CIDP who had not yet received any immunotherapy, and from 7 patients with MMN who were already on chronic maintenance therapy with intravenous immunoglobulin (IVIg). They compared these samples with cells from age- and sex-matched healthy controls, using immunoblotting, a laboratory technique that separates proteins by molecular weight and detects them with specific antibodies, to quantify the phosphorylated, active forms of the signaling enzymes as well as markers of autophagy flux.

The results were strikingly selective. In both CIDP and MMN patients, the levels of phosphorylated, active p38 MAPK in circulating mononuclear cells were significantly higher than in healthy controls. In contrast, the activity of ERK and JNK, the other two MAPK branches, was not significantly altered, and neither were the AMPK/mTORC1 metabolic axis nor the autophagy markers. This specificity matters because it suggests that p38 activation is not a nonspecific consequence of chronic illness or inflammation but a distinctive feature shared by these two related yet clinically distinct neuropathies. The finding also aligns with earlier animal studies in which p38 and other MAPKs were found to be activated in the sciatic nerves of rats with experimental autoimmune neuritis, the laboratory model of human immune-mediated demyelinating neuropathy.

Perhaps the most intriguing clinical correlation emerged from the MMN group. The amount of p38 MAPK protein in patients’ blood cells was negatively correlated with their muscle strength, meaning that patients with more of this kinase in their leukocytes tended to have weaker muscles. Notably, this correlation was absent in CIDP, hinting that p38 may track disease activity differently in the two conditions. MMN is characterized by purely motor deficits, often beginning in the hands, and muscle strength is the principal measure by which clinicians judge disease progression and treatment response. A blood-based molecular correlate of strength, if confirmed, could eventually complement the clinical scales and electrophysiological tests currently used to monitor these patients.

The therapeutic dimension of the study came from comparing patients before and after IVIg treatment. Intravenous immunoglobulin is a pooled preparation of antibodies harvested from thousands of healthy donors, and it is a mainstay of therapy for both CIDP and MMN, though the two diseases differ in their longer-term management. Among nine CIDP patients who received IVIg, the treatment did not change the phosphorylation status of AMPK, any of the MAPKs, or the autophagy markers in their blood cells. Among six MMN patients, however, IVIg produced a measurable biochemical effect: it reduced the phosphorylation of p38 MAPK, ERK, and AMPK in their mononuclear cells. Crucially, the magnitude of the drop in phospho-p38 levels correlated with the improvement in hand grip strength, directly linking a molecular change in circulating immune cells to a functional clinical outcome.

These divergent responses raise fascinating questions about how IVIg works and why the same therapy might engage different mechanisms in different diseases. Previous research has shown that IVIg can suppress inflammatory signaling in monocytes, including NF-κB and p38 MAPK activation driven by tumor necrosis factor-alpha, and can induce autophagy in peripheral blood mononuclear cells. The new findings are consistent with the idea that in MMN, IVIg dampens a p38-centered inflammatory program in leukocytes, and that this immunological cooling accompanies, and may contribute to, the recovery of motor function. In CIDP, by contrast, the lack of detectable signaling change suggests either that IVIg acts through mechanisms not captured by these particular readouts, or that the relevant immune events occur in tissue-resident cells rather than in the circulating pool sampled by the researchers.

The authors are careful to frame the study as exploratory, and the limitations are real. The patient cohorts are small, particularly the MMN group, and the CIDP patients were treatment-naïve while the MMN patients were already on therapy, an asymmetry that complicates direct comparison between the diseases. Immunoblotting of bulk mononuclear cells also averages signals across heterogeneous cell populations, so the p38 elevation could reflect changes in a specific subset of lymphocytes or monocytes rather than a uniform shift. Nevertheless, the correlation between phospho-p38 reduction and grip strength improvement in MMN provides a concrete, testable hypothesis for future studies with larger cohorts and longitudinal sampling.

The findings also carry translational promise. Pharmacological inhibitors of p38 MAPK have been developed for decades, and one such inhibitor, losmapimod, recently showed encouraging results in a phase 2b trial for facioscapulohumeral muscular dystrophy, demonstrating that p38 blockade can be pursued safely in neuromuscular disease. The safety concerns that have historically shadowed p38 inhibitors, including effects on liver function and stress responses, remain relevant, but a circulating biomarker that identifies which patients are most likely to benefit could transform trial design. For now, the study’s central message is that a single stress-activated kinase in blood cells may serve as both a window into disease activity and a readout of therapeutic response in multifocal motor neuropathy, offering researchers a molecular thread to follow in the search for more precise treatments for these rare, disabling conditions.

Subject of Research: The role of leukocyte p38 MAP kinase signaling in immune-mediated peripheral polyneuropathies and its modulation by intravenous immunoglobulin therapy

Article Title: The role of leukocyte p38 MAP kinase in immune-mediated peripheral polyneuropathies: distinct modulation by intravenous immunoglobulins

Article References: Stamenkovic, M., Vukovic, I., Milosevic, E., Peric, S., Paunic, A., Anicin, A., Basta, I., Bozovic, I., Palibrk, A., Ivanovic, V., Trajkovic, V., & Paunovic, V. (2026). The role of leukocyte p38 MAP kinase in immune-mediated peripheral polyneuropathies: distinct modulation by intravenous immunoglobulins. Journal of Neurology, 273(10), Article 627. https://doi.org/10.1007/s00415-026-14106-3

Image Credits: AI Generated

DOI: 10.1007/s00415-026-14106-3

Keywords: p38 MAPK, CIDP, multifocal motor neuropathy, intravenous immunoglobulin, peripheral neuropathy, immune cell signaling, AMPK, mTORC1, autophagy, ERK, JNK, biomarker

The three conditions covered by the analysis share a common therapeutic backbone despite their very different origins. Primary immunodeficiencies are rare, chronic disorders caused by inherited genetic mutations that impair the immune system’s ability to produce functional antibodies, often manifesting in infancy or early childhood, though diagnosis can be delayed well into adulthood. Italy maintains a well-established registry and clinical network for these conditions, with national data indicating a prevalence of between 0.002 and 0.006 percent. Secondary immunodeficiencies, by contrast, arise from external factors such as malignancies, infections, major surgeries, or immunosuppressive therapies, leaving patients vulnerable to serious infections and imposing significant psychological and economic burdens. Chronic inflammatory demyelinating polyneuropathy, or CIDP, is a rare autoimmune neurological disorder in which immune-mediated destruction of the myelin sheath surrounding peripheral nerves causes progressive motor and sensory deficits, with an estimated incidence of 0.36 cases per 100,000 people per year.

For all three patient groups, long-term immunoglobulin therapy is a cornerstone of management, either to replace missing antibodies or to modulate aberrant immune activity. Traditionally, this therapy has been delivered intravenously in hospital or infusion-center settings, an approach that consumes scarce outpatient capacity and imposes repeated travel and time costs on patients. Subcutaneous immunoglobulin offers an alternative that patients can self-administer at home, but the conventional vial-based format requires manual preparation, including drawing up doses and handling residual volumes, which introduces the risk of contamination and dosing errors while generating product wastage and additional administration time.

IgPro20 stands out as the only subcutaneous immunoglobulin therapy currently available in both vial and pre-filled syringe formats. The pre-filled syringe eliminates the need for manual preparation and dose calculation entirely, shortening infusion times, reducing the risk of errors and contamination, and minimizing leftover product. Real-world evidence suggests these operational advantages translate into measurable clinical and economic benefits: use of the pre-filled syringe has been associated with a 17 percent lower weekly dose compared with vials, a difference the study authors attribute to reduced wastage and more efficient use of immunoglobulin supplies rather than any indication-specific treatment effect. Patient preference data also favor the subcutaneous route, with one study reporting that 73 percent of patients preferred it over intravenous administration.

To quantify the financial implications, the research team built a population-based budget impact model in Microsoft Excel from the perspective of the Italian National Health Service, comparing a current scenario without the pre-filled syringe against a future scenario in which it becomes available. The model incorporated drug acquisition costs, administration fees, and adverse event costs over a three-year horizon. In the first year, an estimated 4,794 patients were eligible for immunoglobulin therapy across the three indications: 1,849 with primary immunodeficiency, 1,439 with secondary immunodeficiency, and 1,505 with CIDP, with annual growth projections of 7 percent for the first and third groups and 12 percent for the second. The comparator basket included ten intravenous immunoglobulin products and five subcutaneous products, with market shares informed by Italian affiliate data. Intravenous infusions were assigned a flat fee of €11.60 per administration under national tariff code 99.14.1, while home-based subcutaneous therapy was assumed to incur no administration cost, since manufacturers in Italy typically provide pumps and training free of charge.

The headline finding is striking: introducing IgPro20 pre-filled syringes was associated with total cost savings of €31,524,488 over three years for the Italian healthcare system. The savings were not evenly distributed across the three conditions. CIDP accounted for the largest share at €17,271,412, reflecting high baseline use of IgPro20 vials and the substantial treatment burden associated with hospital-based administration in this population. Primary immunodeficiency generated savings of €8,840,041, largely through decreased use of vials and other subcutaneous products, while secondary immunodeficiency contributed €5,413,035, driven by reduced intravenous immunoglobulin and vial usage. By cost category, the bulk of the savings came from reduced drug acquisition costs, with additional efficiencies in administration and lower adverse event costs, since subcutaneous therapy is generally associated with lower rates of systemic and serious adverse events than intravenous infusion.

The robustness of these findings was tested through extensive sensitivity and scenario analyses. A one-way sensitivity analysis varying each major parameter by plus or minus 20 percent revealed that the model was most sensitive to the prices of the pre-filled syringe and vials: shifting the syringe price between €52.00 and €78.00 produced a budget impact ranging from a saving of €60.7 million to €2.3 million. Scenario analyses proved reassuring even under conservative assumptions. When the dosing advantage was halved to an 8.5 percent reduction, projected savings fell to €16.6 million but remained substantial. Most notably, even when the researchers assumed identical dosing between the syringe and vial formats, thereby removing the entire 17 percent efficiency advantage drawn from real-world data, the pre-filled syringe still generated savings of €1.6 million over three years. Adopting a broader societal perspective that included indirect costs such as travel and lost productivity increased savings to €31.8 million, while applying lower intravenous product pricing based on regional tenders still yielded €29.9 million in savings. Excluding intravenous-specific infusion complications barely changed the picture, with savings of €31.4 million, confirming that acquisition costs, not adverse event differences, were the primary economic driver.

The study’s authors place these results in the context of a healthcare system under strain. Hospital overcrowding remains a persistent challenge in Italy, and shifting immunoglobulin delivery away from hospital infusion centers toward home-based subcutaneous administration could relieve pressure on inpatient and outpatient services alike. The pre-filled syringe format, by simplifying preparation and supporting patient autonomy, may also improve adherence and quality of life, offering continuity of care even during service disruptions. The authors caution, however, that the choice of therapy and route of administration should remain individualized: some patients prefer intravenous immunoglobulin for its less frequent dosing, direct professional support, or a desire to avoid self-infusion responsibilities, making shared decision-making essential.

The analysis is not without limitations. The model relied on proprietary internal data for population estimates and market shares, which may limit external replicability, and the pivotal 17 percent dosing-reduction assumption was drawn from observational evidence in non-Italian settings. The absence of published adverse event data for subcutaneous immunoglobulin in secondary immunodeficiency led to an assumption of zero events, potentially underestimating costs, and aggregating three clinically distinct populations may obscure meaningful differences in resource use. The model also used a simplified population structure that did not account for aging or mortality, and ex-factory prices may not reflect regional tender variations. Nevertheless, the consistency of savings across every scenario tested lends considerable weight to the central conclusion.

For Italian policymakers and payers, the message is clear: a relatively modest packaging change, moving from vials to pre-filled syringes for subcutaneous immunoglobulin, could free up €31.5 million over three years while supporting a more patient-centered, resource-efficient model of care. As demand for immunoglobulin therapy continues to rise and infusion capacity remains constrained, the study offers actionable evidence that aligning clinical value with economic sustainability is achievable, one syringe at a time.

Subject of Research: Budget impact analysis of subcutaneous immunoglobulin pre-filled syringes for immunodeficiency and CIDP in Italy

Article Title: Multi-Indication Budget Impact Analysis of Subcutaneous IgPro20 Pre-filled Syringes for the Treatment of Primary Immunodeficiency Syndromes, Secondary Immunodeficiencies, and Chronic Inflammatory Demyelinating Polyneuropathy in Italy

Article References: Kuatov, B., MacDonald, A., Priest, S., Tran, D., Undreiner, L., Taskin, M. I., Villa, S., & Marcellusi, A. (2026). Multi-Indication Budget Impact Analysis of Subcutaneous IgPro20 Pre-filled Syringes for the Treatment of Primary Immunodeficiency Syndromes, Secondary Immunodeficiencies, and Chronic Inflammatory Demyelinating Polyneuropathy in Italy. Advances in Therapy. https://doi.org/10.1007/s12325-026-03805-y

Image Credits: AI Generated

DOI: 10.1007/s12325-026-03805-y

Keywords: immunoglobulin therapy, pre-filled syringes, primary immunodeficiency, secondary immunodeficiency, CIDP, budget impact analysis, health economics, Italy, subcutaneous immunoglobulin, IgPro20, healthcare costs, home-based treatment