SUMMARY

• In a 24-week, phase 3, randomized, double-blind, placebo (PBO)-controlled trial in adult patients, muscle spasm was reported as an adverse event (AE) in 12.2% (12/98) of patients in the IMAAVY group and 3.1% (3/98) of patients in in the PBO group.^1,2
  • In the ongoing open-label extension (OLE) phase with a median follow-up of 72 weeks, muscle spasm was reported in 6.8% (12/176) of patients in the combined IMAAVY group.
  • During the double-blind and OLE phases, all reports of muscle spasms were considered mild to moderate in severity.
• In an ongoing, phase 2/3, open-label, clinical trial in adolescent patients (12 to <18 years of age), muscle spasm was reported in 14.3% (1/7) of patients receiving IMAAVY through week 24.³ 

CLINICAL DATA

VIVACITY-MG3

Antozzi et al (2025)¹ 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- 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.^1,4 
  • 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 study consisted of a ≤4-week screening phase, followed by a 24-week, double-blind, PBO-controlled treatment phase, a variable-duration, OLE phase, and a 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.⁴ 
• 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 (Q2W), or matching PBO through week 24 in addition to standard of care (SOC) therapy.¹ 
• Patients entering the OLE phase continued to receive IMAAVY 15 mg/kg Q2W in addition to SOC.⁶ 

Results

Double-Blind Phase

• A total of 196 patients (IMAAVY, n=98; PBO, n=98) were included in the safety analysis set.¹ 
• Muscle spasm was reported in 12.2% (12/98) of patients in the IMAAVY group and 3.1% (3/98) of patients in the PBO group; all cases were considered of mild or moderate severity.² 
  • The event/patient-years (P-Y) rate for muscle spasms was 0.3 and 0.07 in the IMAAVY and PBO groups, respectively.

Ongoing OLE Phase

• A total of 176 patients were included in the safety analysis set with a median follow-up of 72 weeks (PBO→IMAAVY, n=88; IMAAVY→IMAAVY, n=88). 
• Muscle spasm was reported in 6.8% (12/176) of patients in the combined IMAAVY group; all cases were considered of mild or moderate severity.
  • The event/P-Y rate for muscle spasm was 0.08 in the combined IMAAVY group.

Phase 2/3 Vibrance-mg Study

Strober et al (2024)³ presented results through the active treatment phase (study day 1 through week 24) in adolescents (aged 12 to <18 years) with gMG who have an insufficient response to ongoing SOC therapy.

Study Design/Methods

• Adolescent patients, all with anti-AChR antibody positive gMG, were included in the analysis.
• The study consists of a screening period of up to 4 weeks, then a 24-week, open-label, active treatment phase where patients will receive 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.

Results

• A total of 7 adolescents were included in the study with an average duration of follow-up of 18.37 weeks.
• Muscle spasm was reported in 14.3% (1/7) of patients receiving IMAAVY through week 24.

Literature Search

A literature search of MEDLINE^®, EMBASE^®, BIOSIS Previews^®, and DERWENT^® (and/or other resources, including internal/external databases) was conducted on 24 June 2025.