SUMMARY

• The company cannot recommend any practices, procedures, or usage that deviate from the approved labeling.
• In a subgroup analysis of a phase 3 clinical trial in adult patients with antibody-negative generalized myasthenia gravis (gMG)^1,2: 
  • The average (least squares [LS] mean) change from baseline in the Myasthenia Gravis Activities of Daily Living (MG-ADL) total score over weeks 22, 23, and 24 for IMAAVY compared to placebo (PBO) was -3.3 (95% confidence interval [CI], -4.62 to -1.99) vs -3.23 (95% CI, -4.46 to -1.99); the between-group difference was -0.08 (95% CI, -1.87 to 1.71).
  • The average (LS mean) change from baseline in the Quantitative Myasthenia Gravis (QMG) total score over weeks 22 and 24 for IMAAVY compared to placebo (PBO) was -1.92 (95% CI, -3.78 to -0.06) vs -2.15 (95% CI, -3.89 to -0.42); the between-group difference was 0.23 (95% CI, -2.30 to 2.77).

CLINICAL DATA

VIVACITY-MG3

Antozzi et al (2025)¹ evaluated the efficacy and safety of IMAAVY in adults with gMG in a phase 3, randomized, multicenter, double-blind, PBO-controlled study.

Study Design/Methods

• Patients (≥18 years of age) with anti- acetylcholine receptor (AChR), muscle-specific tyrosine kinase (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.^1,3 
  • The safety analysis population included all randomized patients who received ≥1 dose (partial or complete) of either IMAAVY or PBO in the double-blind phase, including antibody-positive and antibody-negative patients.¹ 
  • The primary efficacy analysis population included all patients from the safety analysis dataset who were positive for anti-AChR, anti-MuSK, or anti-LRP4 antibodies, as confirmed prior to randomization.¹
• Seronegative gMG was defined as being triple-antibody-negative for antibodies against AChR, MuSK, and LRP4. Patients who were seronegative were clinically diagnosed with gMG on the basis of investigator clinical examination or electrophysiological studies.
  • Eligibility criteria for the study did not include that patients with seronegative gMG had a diagnosis verified by single fiber electromyography or repetitive nerve stimulation or had demonstrated improvement in MG signs with treatments including oral acetylcholinesterase (AChE) inhibitors, plasma exchange (PLEX), immunoabsorption, or intravenous immunoglobulin (IVIg)/subcutaneous immunoglobulin (SCIg) treatment.^1,2 
• 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.² 
  • 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.
• Eligible patients were randomized (1:1) to receive a loading dose of intravenous IMAAVY 30 mg/kg at week 0, followed by 15 mg/kg every 2 weeks or matching PBO through week 24, in addition to standard-of-care (SOC) therapy.^1,2 
• The primary efficacy endpoint was the average change from baseline in the MG-ADL total score over weeks 22, 23, and 24 in patients with seropositive gMG (anti-AChR+, anti-MuSK+, or anti-LRP4+).^1,2 

Results

• Overall, 196 patients (IMAAVY, n=98; PBO, n=98) were included in the safety analysis set.¹ 
  • Of these, 153 patients were included in the primary efficacy analysis set (patients who were antibody positive only), with 77 patients randomized to receive IMAAVY and 76 patients randomized to receive PBO.
  • Of these, 43 patients were antibody-negative, with 21 patients randomized to receive IMAAVY and 22 patients randomized to receive PBO.

Efficacy

• In patients with antibody-positive gMG, a significantly greater reduction from baseline in the MG-ADL total score over weeks 22, 23, and 24 was observed in the IMAAVY group (LS mean change, -4.70 [standard error (SE) 0.329]) compared to the PBO group (LS mean change, -3.25; SE, 0.335); LS mean difference, -1.45 (95% CI, -2.38 to -0.52; P=0.0024).^1,2 
• Subgroup analysis results of patients with antibody-negative gMG are summarized in Table: Average Change from Baseline in the MG-ADL Total Score Over Weeks 22, 23, and 24 and the QMG Total Score Over Weeks 22 and 24 in Antibody-Negative Patients.^a,2

Safety

• The proportion of patients who reported related adverse events (AEs), per investigator assessment, was 29% in both the IMAAVY (28/98) and PBO (28/98) groups.¹ 
• Any serious adverse events (SAEs) were reported in 9% (9/98) and 14% (14/98) of patients in the IMAAVY and PBO groups, respectively.¹ 
• The most common AEs occurring in ≥10% of patients in the IMAAVY group compared to the PBO group were coronavirus disease 2019 (COVID-19)-associated AEs (15% vs 12%), headache (14% vs 17%), muscle spasms (12% vs 3%), myasthenia gravis (12% vs 12%), and peripheral edema (12% vs 2%).^1,4  

Literature Search

A literature search of MEDLINE^®, EMBASE^®, BIOSIS Previews^®, and DERWENT^® (and/or other resources, including internal/external databases) was conducted on 06 March 2025.