#AANAM – Under-the-Skin Immunoglobulin Treatment Maintains Stable Disease Activity, Study Reports

Treatment with subcutaneous immunoglobulin (SCIg) — a new formulation given as an under-the-skin injection — enabled people with myasthenia gravis (MG) to maintain stable disease activity while transitioning from intravenous immunoglobulin (IVIg), according to a study in the U.S. and Canada.

The findings of the study, “Subcutaneous Immunoglobulin in Myasthenia Gravis: Results of a North American Open Label Study,” were presented by researcher Mazen Dimachkie at the 2019 American Academy of Neurology (AAN) Annual Meeting, taking place through May 10 in Philadelphia.

MG treatment with IVIg has led to improvements (reductions) in the Quantitative MG (QMG) score in comparison with placebo, and has shown efficacy compared with plasma exchange (PLEX).

The research team assessed the effectiveness, safety and tolerability of SCIg in the treatment of people with MG who are on IVIg — immunoglobin administered as a slow infusion into the patient’s bloodstream over several hours — as part of routine clinical care. Many people with other chronic autoimmune diseases, including CIDP, have found subcutaneous treatment to be easier than IVIg.

“In CIDP, SCIg is preferred in 69% of cases due to increased flexibility, more stable strength, milder side effects and time saving,” the presentation read.

The subcutaneous route may be easier, and faster, for immunoglobulin administration than intravenous delivery, and is safe and efficacious in MG, the scientists said.

The multi-center, open label, and prospective study had two parts: an IVIg screening phase (ISP), between 10 weeks and one week prior to therapy, followed by the experimental treatment phase (ETP) between weeks 0 and 12. The researchers hypothesized that more than 80% of patients who started the ETP would have stable (less than 3 points increase) QMG scores at week 12 — the study’s primary outcome.

The secondary endpoints were differences from week 0 to week 12 in the Myasthenia Gravis Activities of Daily Living Profile (MG-ADL); the MG-QOL-15, measuring quality of life; the MG Composite (MGC); and the Treatment Satisfaction Questionnaire for Medication (TSQM).

All but one of the 23 patients in the screening stage entered the experimental phase. Among those 22 participants, 12 (54.5%) were women and 18 (78%) were white. The mean age was 51.4 years.

For the primary endpoint, 19 patients had complete QMG data during ETP. One of the remaining three withdrew from the ISP due to worsened condition, while the other two quit before week 4 due to discomfort with the needle.

The results of the primary statistical analysis showed stable QMG scores, or “treatment success,” in 19 of the 22 patients (86.4%), while a sensitivity analysis resulted in 17 participants (77.3%) with similar findings.

Then, a subsequent analysis in 20 patients confirmed treatment efficacy in 17 (85%) patients.

Secondary measures MG-ALD, MG-QOL-15, and TSQM, comparing week 0 to week 12, showed no significant differences, as the levels remained stable. Results of the MG Composite scale , however, showed a positive trend at week 12. “Composite [MGC] at least stable if not slightly better,” the presenter said. IgG level analysis showed a stable trend from week 0 to week 12.

The investigators further found that SCIg was safe and well-tolerated, with mostly local skin reactions.

In conclusion, “most MG patients who were doing well on IVIg maintained disease stability for another 12 weeks once transitioned to SCIg,” the researchers concluded.