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, uncontrolled clinical trial in adolescents (12 to <18 years of age), muscle spasm was reported in 12.5% (1/8) of patients receiving IMAAVY through week 24 and in 16.7% (1/6) of patients in the long-term extension (LTE) phase.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

Ramchandren et al (2022)^7,8 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)³ presented results from Cohort 1 through the active treatment phase (study day 1 through week 24) and 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 every 4 weeks (Q4W; dosing at investigator’s discretion) in addition to SOC.

Results

• A total of 8 adolescents were included in the active treatment phase of the study with a median duration of follow-up of 24 weeks.
• At the time of this analysis, 6 patients had entered the LTE phase with a median duration of follow-up of 44.5 weeks.
• Muscle spasm was reported in 12.5% (1/8) of patients receiving IMAAVY through week 24 and in 16.7% (1/6) of patients in the LTE phase.

Literature Search

A literature search of MEDLINE^®, EMBASE^®, BIOSIS Previews^®, and DERWENT^® (and/or other resources, including internal/external databases) was conducted on 10 December 2025.