IMAAVY - Alternative Dosing for IMAAVY in Patients with Generalized Myasthenia Gravis

SUMMARY

• The company cannot recommend any practices, procedures, or usage of IMAAVY that deviate from the approved labeling.
• IMAAVY is a fully human, aglycosylated, effectorless immunoglobulin G1 (IgG1) anti-neonatal fragment crystallizable receptor (FcRn) monoclonal antibody.^1-3
  • By interfering with the binding of IgG to FcRn, IMAAVY increases the lysosomal degradation of IgG, which reduces serum levels of total IgG and pathogenic IgG autoantibodies that cause myasthenia gravis (MG).
• In an open-label extension (OLE) of the Phase 3 VIVACITY-MG3 study, patients were given the option to switch from 15 mg/kg every 2 weeks (Q2W) to 30 mg/kg every 4 weeks (Q4W).⁴
  • Of 153 patients who entered the OLE, 25 patients switched to IMAAVY 30 mg/kg Q4W dosing, of whom 21 patients were seropositive.
  • No significant difference in Myasthenia Gravis Activities of Daily Living (MG-ADL) total scores was observed before vs after switch to IMAAVY 30 mg/kg Q4W. Mean (standard deviation [SD]) change from baseline was -2.36 (3.15) pre-switch and -2.04 (3.03) post-switch.
• A phase 2, multicenter, randomized, double-blind (DB), placebo (PBO)-controlled clinical trial evaluated the safety and efficacy of IMAAVY in 68 adult patients with generalized myasthenia gravis (gMG) who had an insufficient response to ongoing, stable standard of care (SOC) therapy.²
  • Greater mean improvements in MG-ADL total scores from baseline to day 57 were observed in all continuous IMAAVY dosing groups vs PBO.
  • The proportion of patients with treatment-emergent adverse events (TEAEs) was comparable in the IMAAVY vs PBO groups. No clinically significant safety signals were identified.

CLINICAL DATA

Phase 3 Clinical Trial

Vu et al (2026)⁴ evaluated the efficacy and safety of IMAAVY in patients who switched from 15 mg/kg Q2W to 30 mg/kg Q4W in the OLE phase of the VIVACITY-MG3 study.

Study Design/Methods

• Patients (≥18 years of age) with Myasthenia Gravis Foundation of America [MGFA] class II-IV, MG-ADL score ≥6 were included in the study.
• The study consisted of a ≤4-week screening phase, followed by a 24-week, DB, PBO-controlled treatment phase, a variable-duration, OLE phase, and a safety follow-up at 8 weeks after the last infusion.
• Eligible patients were randomized (1:1) to receive a loading dose of intravenous (IV) IMAAVY 30 mg/kg at week 0, followed by 15 mg/kg Q2W or matching PBO through week 24 in addition to SOC therapy.
• In the OLE period, patients from the DB phase received 15 mg/kg IV Q2W and had the option to switch to 30 mg/kg IV Q4W.

Results

Baseline Demographics

• Overall, 153 patients entered the OLE.
  • A total of 25 patients switched to IMAAVY 30 mg/kg Q4W, of whom 21 patients were seropositive.
• Of the 21 patients who were seropositive:
  • The median age was 48.0 years (range: 26–83), and 61.9% were female.
  • Mean (SD) duration of q4w dosing was 17.7 (15.78) weeks.
  • Mean (SD) baseline MG-ADL and Quantitative Myasthenia Gravis (QMG) total scores were 8.3 (3.50) and 14.8 (6.08), respectively.

Efficacy

• Among seropositive patients who switched to IMAAVY 30 mg/kg Q4W, the mean (SD) baseline MG-ADL and QMG total scores were 8.3 (3.50) and 14.8 (6.08), respectively.
• Mean changes from baseline in efficacy measures are presented in Table: Mean Change from Baseline in MG-ADL and QMG Total Scores Before vs After Switch to 30 mg/kg Q4W.

Safety

• For safety outcomes in the IMAAVY 30 mg/kg Q4W group, see Table: Summary of AEs in Q4W Dosing Group.

Phase 2 Clinical Trial

Antozzi et al (2024)² conducted a phase 2, multicenter, randomized, DB, PBO-controlled clinical trial to evaluate the safety and efficacy of IMAAVY in adult patients with gMG who had an insufficient response to ongoing, stable SOC therapy.

Study Design/Methods

• Patients (≥18 years of age) with anti-acetylcholine receptor (AChR) or anti-muscle-specific tyrosine kinase (MuSK) antibody-positive gMG (MGFA class II, III, or IVa) were included in the study.
• The study consisted of a 4-week screening period, followed by an 8-week, DB treatment period. Post treatment follow-up assessment was conducted over an 8-week period.
• In addition to SOC therapy, eligible patients were randomized (1:1:1:1:1) to receive IV infusions of IMAAVY 5 mg/kg once Q4W, IMAAVY 30 mg/kg Q4W, IMAAVY 60 mg/kg single dose, IMAAVY 60 mg/kg Q2W, or PBO Q2W.
• The primary endpoints was the change in total MG-ADL score from baseline to day 57.
• A secondary endpoint was change in QMG score from baseline to day 57.

Results

Baseline Demographics

• Of the 68 randomized patients, 57 completed the treatment period. Treatment discontinuation occurred in 8 patients in the combined IMAAVY group (COVID-19, n=7; violation of exclusion criteria, n=1) and 3 patients in the PBO group (adverse events [AEs], n=2; withdrawal of consent, n=1). For baseline demographics, see Table: Baseline Demographic Characteristics (ITT Population).

Efficacy

• Mean changes in efficacy measures are presented in Table: Improvement in MG-ADL and QMG Scores from Baseline to Day 57 (ITT Population).

Safety

• The proportion of combined IMAAVY-treated patients with TEAEs (83.3%) was comparable to that of PBO-treated patients (78.6%). No correlation was found in the overall incidence of TEAEs among the 4 IMAAVY dose regimens or for any individually reported preferred terms. See Table: Incidence of TEAEs in the IMAAVY vs PBO Group.

Literature Search

A literature search of MEDLINE^®, EMBASE^®, BIOSIS Previews^®, and DERWENT^® (and/or other resources, including internal/external databases) was conducted on 30 June 2026.