SUMMARY

• In a phase 3, randomized, double-blind, placebo (PBO)-controlled trial, median pre-dose reduction from baseline in total serum immunoglobulin G (IgG) after loading dose was -74.6% at week 2 and -68.8% at week 24 in the IMAAVY group.^1,2
  • Median predose reduction in antibody titers for anti-acetylcholine receptor (AChR) and muscle-specific tyrosine kinase (MuSK) were -65.1% vs -10.1% and -38.8% vs -4.4% for the IMAAVY and PBO groups, respectively.¹ 
  • In the ongoing, open-label extension (OLE) of the study, the mean percent change from baseline in the IgG level was -61.56 in the IMAAVY→IMAAVY+standard of care (SOC) group and -61.96 in the PBO→IMAAVY+SOC group at week 60.³ 
• In a phase 2, randomized, double-blind, PBO-controlled trial, dose-dependent reductions in total serum IgG levels were seen as early as week 1 after the first IMAAVY infusion as summarized below.⁴
• In an ongoing, phase 2/3, open-label, uncontrolled clinical trial in adolescents (12 to <18 years of age), a reduction in median (interquartile range, IQR) serum IgG was observed from baseline (10.7 [8.9-13.1] g/L) to week 24 (3.2 [2.3-3.5] g/L) and week 72 (3.3 [2.8-4.3] g/L).⁵ 

CLINICAL DATA

VIVACITY-MG3

Antozzi et al (2025)² evaluated the efficacy and safety of IMAAVY in adults with generalized myasthenia gravis (gMG) in a phase 3, randomized, multicenter, double-blind, PBO-controlled study.

Study Design/Methods

• Patients (≥18 years of age) with anti- AChR, MuSK or low-density lipoprotein receptor 4 (LRP4) antibody positive or seronegative (in all countries except France) gMG (Myasthenia Gravis Foundation of America [MGFA] class IIa-IVb) were included in the study.^1,2 
  • The safety analysis population included all randomized patients who received ≥1 dose (partial or complete) of any study treatment in the double-blind phase.
  • The efficacy analysis population included all patients from the safety analysis set who had anti-AChR, anti-MuSK or anti-LRP4 antibody positive gMG.
• The study consisted of a ≤4-week screening phase, followed by a 24-week, double-blind, PBO-controlled treatment phase, a variable-duration, open-label extension phase, and a safety follow-up at 8 weeks after the last infusion (included patients who withdrew or discontinued after receiving any amount of the study intervention).^1,2,6 
• 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 every 2 weeks (Q2W) or matching PBO through week 24 in addition to SOC therapy.
• Patients entering the OLE phase continued to receive IMAAVY 15 mg/kg Q2W in addition to SOC.³ 

Results

• Overall, 196 patients (IMAAVY, n=98; PBO, n=98) were included in the safety analysis set.^1,2 
  • Of those patients, 153 patients were included in the primary efficacy analysis set (all antibody positive patients only).
• For baseline demographics, see Table: Baseline Demographics and Characteristics.^1,2 

Pharmacodynamic Activity

• In the full analysis set, the median pre-dose (minimal) reduction in the total serum IgG from baseline after loading dose was -74.6% (IQR, -79.4 to -68.7) at week 2 and
  -68.8% (IQR, -75.3 to -62.2) at week 24 in the IMAAVY group.² 
• In the ongoing OLE, at week 60, the mean (SE) percent change from baseline in the IgG level was -61.56 (2.297) in the IMAAVY→IMAAVY+SOC group and -61.96 (2.686) in the PBO→IMAAVY+SOC group. See Figure: Total IgG Reduction From Baseline (Seropositive Population).³ 

• The median percent change in serum IgG subclass from baseline to week 24 is presented in Table: Median Percent Change in IgG Subclass from Baseline at Week 24.⁶ 

• No changes in total IgM, IgA, or IgE were observed during the double-blind phase.
• The IMAAVY group showed a ~7-fold and ~9-fold greater median pre-dose reduction in anti-AChR (-65.1% vs -10.1%) and anti-MuSK (-38.8% vs -4.4%) antibody titers compared to the PBO group, respectively.See Table: Percent Change in Pathogenic IgG from Baseline to Week 24.¹ 

Phase 2 VIVACITY-MG Study

Antozzi et al (2024)^4,7 conducted a phase 2, randomized, multicenter, double-blind, PBO-controlled clinical trial to evaluate the safety, efficacy, pharmacokinetic (PK), and pharmacodynamic (PD) 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-AChR or anti-MuSK antibody-positive gMG (MGFA class II, III, or IVa) were included in the study.
• The study included a 4-week screening period, followed by an 8-week, double-blind treatment period. Posttreatment follow-up assessment was performed for a period of 8 weeks.
• In addition to SOC therapy, eligible patients were randomized (1:1:1:1:1) to receive intravenous infusions of: IMAAVY 5 mg/kg once every 4 weeks (Q4W), 30 mg/kg Q4W, 60 mg/kg single dose, or 60 mg/kg Q2W or PBO Q2W (5% dextrose in water).
• Exploratory endpoints included PD activity of IMAAVY as measured by changes in concentrations of total IgG, IgG subclasses, IgA, IgM, and IgE, and autoantibodies (anti-AChR and anti-MuSK).

Results

• A total of 68 patients (IMAAVY, n=54; PBO, n=14) were randomized to treatment.
• For baseline demographics, see Table: Baseline Demographic Characteristics (ITT Population).

Pharmacodynamics

• Dose-dependent reductions in serum total IgG levels were observed with IMAAVY.
  • Maximum IgG reductions observed in the IMAAVY 5 mg/kg Q4W, 30 mg/kg Q4W, 60 mg/kg single-dose, and 60 mg/kg Q2W groups were 42%, 72%, 80%, and 83%, respectively.
  • Mean total IgG reductions from baseline were seen as early as 1 week after the first IMAAVY infusion, ranging from 42% at 5 mg/kg dose to 69% at 30 mg/kg or higher doses.
• Similar reductions were observed with all IgG subclasses, with no changes in total IgM, IgA, and IgE across the IMAAVY treatment groups.
• Dose-dependent reductions in anti-AChR autoantibodies were seen across the IMAAVY treatment groups, corresponding to reductions in total IgG. See Figure: Mean Percentage Change in Baseline IgG and AChR-Binding Antibody by Dosing Arm Over Time.

Vibrance-mg Study

Ramchandren et al (2022)^8,9 is evaluating the safety, efficacy, PK, and PD of IMAAVY in children and adolescents aged 2 to <18 years with gMG who have an insufficient response to ongoing, stable SOC therapy in an ongoing, open-label, uncontrolled multicenter clinical trial. Cohort 1 will consist of adolescents (aged 12 to <18 years), and Cohort 2 will consist of children (aged 2 to <12 years).

Strober et al (2025)⁵ presented results from Cohort 1 through the active treatment phase (study day 1 through week 24) and long-term extension (LTE) phase with a clinical cutoff date of August 23, 2024.

Study Design/Methods

• Adolescent patients, all with anti-AChR antibody positive gMG, were included in this analysis.
• The study consists of a screening period of up to 4 weeks, followed by a 24-week, open-label, active treatment phase, an optional 48-week LTE phase, and a safety follow-up at 8 weeks after the last infusion.  
  • Patients who withdrew or discontinued after receiving any amount of the study intervention were required to complete a safety follow-up assessment at 8 weeks after the last dose.
• All patients will receive an IMAAVY 30 mg/kg IV loading dose at week 0, followed by IMAAVY 15 mg/kg Q2W from week 2 to week 22 in addition to SOC therapy.
• Patients entering the LTE phase will receive IMAAVY 15 mg/kg Q2W or IMAAVY 30 mg/kg Q4W (dosing at investigator’s discretion) in addition to SOC.
• The primary efficacy endpoint is the effect of IMAAVY on the total serum IgG level at week 24.

Results

Baseline Demographics

• Baseline demographics of the 8 adolescent patients (all with anti-AChR antibody-positive gMG) are summarized in Table: Baseline Demographics and Disease Characteristics.

Efficacy

• IgG reduction was observed in adolescent patients treated with IMAAVY.
• At the time of this analysis, of the 8 patients who had been enrolled, 7 completed the AT phase and 6 entered the LTE phase.
  • Reduction in median (IQR) serum IgG was observed from baseline (10.7 [8.9-13.1] g/L) to week 24 (3.2 [2.3-3.5] g/L) and week 72 (3.3 [2.8-4.3] g/L).
  • The median (IQR) percentage change from baseline (CFB) was -72.6% (-79.1 to -70.1) at week 2 and -73.3% (-78.7 to -62.8) at week 24. The effect was generally sustained in the LTE, with a median (IQR) CFB of -60.6% (-72.0 to 48.8) at week 72 (n=3). For details, see Figure: Median (IQR) Total Serum IgG Levels Over Time.

Safety

• During the study, there were no reports of adverse events (AEs) or serious adverse events (SAEs) leading to discontinuation reported in adolescent patients receiving IMAAVY. No treatment emergent adverse events (TEAEs) leading to death or AEs of special interest were reported in the study. For details, see Table: Summary of Treatment-Emergent AEs in AT and LTE Phases.
• One patient reported with a SAE of worsened gMG after week 72 in LTE (at week 84).
• Another patient reported an AE of influenza at ~week 30 that led to temporary treatment discontinuation.

Literature Search

A literature search of MEDLINE^®, EMBASE^®, BIOSIS Previews^®, and DERWENT^® (and/or other resources, including internal/external databases) was conducted on 21 January 2026.