IMAAVY - Long-term Phase 3 Safety and Efficacy in Adult Patients with Generalized Myasthenia Gravis

SUMMARY

• In an open-label extension (OLE) phase of a 24-week, phase 3, randomized, double-blind (DB), placebo (PBO)-controlled trial in adult patients with generalized myasthenia gravis (gMG)^1,2:
  • The mean (standard error [SE]) from DB baseline in the Myasthenia Gravis Activities of Daily Living (MG-ADL) total score was -6.47 (1.20) in the IMAAVY → IMAAVY + standard of care (SOC) group and -6.69 (0.85) in the PBO → IMAAVY + SOC group at OLE week 96.² 
  • No cases of unexpected adverse events (AEs) were reported during the OLE phase.³

Clinical data

VIVACITY-MG3

Antozzi et al (2025)^1,2 evaluated the efficacy and safety of IMAAVY in adults with gMG in a phase 3, randomized, multicenter, DB, 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-related protein 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.^1,4
  • The safety analysis population included all randomized patients who received ≥1 dose (partial or complete) of any study treatment in the DB phase or of IMAAVY in the OLE phase.^1,3
  • The primary efficacy analysis population included all patients from the safety analysis dataset who were antibody-positive for AChR, MuSK, or LRP4, confirmed prior to randomization.¹
• 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 safety follow-up at 8 weeks after the last infusion.^1,5
  • 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.⁵
• 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.¹
• Patients entering the OLE phase continued to receive IMAAVY 15 mg/kg Q2W in addition to SOC.^2,3
• The primary efficacy endpoint was the average change from baseline in the MG-ADL total score over weeks 22, 23, and 24.¹
• A key secondary endpoint was the average change in the Quantitative Myasthenia Gravis (QMG) score over weeks 22 and 24.¹

Results

• Overall, 176 patients were included in the OLE safety analysis set.³
• Of those patients, 137 patients were included in the primary efficacy analysis set (patients who were antibody-positive only), with 71 patients randomized to IMAAVY and 66 randomized to PBO. See Table: Baseline Demographics and Characteristics (Seropositive Population).

Efficacy

• A total of 137 patients with antibody-positive gMG were treated with IMAAVY in the OLE phase with a follow-up duration of over 96 weeks.² 
• At OLE week 96, the mean (SE) change from DB baseline in the MG-ADL total score was -6.47 (1.20) in the IMAAVY → IMAAVY + SOC group, -6.69 (0.85) in the PBO → IMAAVY + SOC group and -6.58 (0.71) in the overall IMAAVY + SOC group. See Figure: Mean Change in the MG-ADL Total Score from DB Baseline (Seropositive Population).²

• At OLE week 96, the mean (SE) change from DB baseline in the QMG total score was
  -5.97 (1.29) in the IMAAVY → IMAAVY + SOC group, -5.81 (1.03) in the PBO → IMAAVY + SOC group and -5.89 (0.80) in the overall IMAAVY + SOC group. See Figure: Mean Change in the QMG Total Score from DB Baseline (Seropositive Population).²

Safety

• No cases of unexpected AEs were reported during the OLE phase.³ For details, see Table: Safety and Tolerability (Exposure Adjusted Incidence Rate) and Table: AEs by Preferred Term (Exposure Adjusted Incidence Rate).

Pharmacodynamics

• At OLE week 96, the mean (SD) predose (minimal) percent change from DB baseline in the immunoglobulin G (IgG) level was -64.06 (12.91) in the IMAAVY → IMAAVY + SOC group and -63.24 (14.32) in the PBO → IMAAVY + SOC group. See Figure: Total IgG Reduction from Baseline (Seropositive Population).²

Literature Search

A literature search of MEDLINE^®, EMBASE^®, BIOSIS Previews^®, and DERWENT^® (and/or other resources, including internal/external databases) was conducted on 12 March 2026.