SUMMARY

• In a phase 3, randomized, double-blind (DB), placebo (PBO)-controlled trial in adult patients with generalized myasthenia gravis (gMG), 61.0% and 71.1% of patients were on concomitant corticosteroid therapy in the IMAAVY and PBO groups, respectively.^1,2 
  • In the ongoing open-label extension (OLE) phase, a total of 45% of patients with antibody-positive gMG who received corticosteroids at OLE baseline either decreased or discontinued steroid use at data cutoff. There was a decrease in mean prednisone dosage from 23 to 10 mg equivalents per day.³
• In a phase 2, randomized, DB, PBO-controlled trial in adult patients with gMG, 68.5% and 78.6% of patients were on concomitant glucocorticoid therapy in the combined IMAAVY and PBO groups, respectively.⁴ 
• In an ongoing, phase 2/3, open-label, uncontrolled clinical trial in adolescents (12 to <18 years of age), 71.4% of patients on IMAAVY treatment were on concomitant corticosteroid therapy.^5,6 

CLINICAL DATA

VIVACITY-MG3

Antozzi et al (2025)^1,3,7 evaluated the efficacy and safety of IMAAVY in adults with gMG in a phase 3, randomized, multicenter, DB, PBO-controlled study with an ongoing OLE phase.

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.
  • The safety analysis population included all randomized patients who received ≥1 dose (partial or complete) of any study treatment in the DB 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, a 24-week, DB, PBO-controlled treatment phase, a variable-duration OLE phase (up to 240 weeks in the European Union), 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.
• 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.
• Patients entering the OLE phase continued to receive IMAAVY 15 mg/kg every 2 weeks in addition to SOC.
  • Tapering one of the patient’s concomitant gMG medications every 4 weeks was allowed in the OLE phase if disease was stable in the past 4 weeks based on MG-ADL scores and on investigator’s discretion.
• The primary efficacy endpoint was the average change from baseline in the Myasthenia Gravis Activities of Daily Living (MG-ADL) total score over weeks 22, 23, and 24 in patients who were seropositive (anti-AChR, anti-MuSK, anti-LRP4) with gMG.
  • The key secondary endpoint in this population was the average change from baseline in the Quantitative Myasthenia Gravis (QMG) total score over weeks 22 and 24.

Results

DB Phase^1,2  

• Overall, 196 patients (IMAAVY, n=98; PBO, n=98) were included in the full analysis set. Of those patients, 153 patients were included in the primary efficacy analysis set (antibody positive patients only) with 77 patients randomized to IMAAVY and 76 patients randomized to PBO.
• A total of 61.0% and 71.1% of patients in the IMAAVY and PBO groups were on stable concomitant corticosteroid therapy, respectively (see Table: VIVACITY-MG3: Concomitant Corticosteroid Therapy). 

Ongoing OLE Phase³ 

• A total of 137 patients with antibody-positive gMG entered the OLE phase.
  • PBO→IMAAVY, n=66 and IMAAVY→IMAAVY, n=71
  • The median treatment duration was 69.1 weeks (range 8-128) and 62.1 weeks (range 8-128) for the PBO→IMAAVY and IMAAVY→IMAAVY groups, respectively.
• 45% (40/89) of patients receiving corticosteroids at OLE baseline were able to decrease or discontinue steroids at data cutoff.
  • Among these patients, the mean dose of prednisone (mg equivalents per day) decreased from 23 to 10.
• MG-ADL and QMG total scores were measured in patients who decreased or discontinued steroids (see Figure: MG-ADL Total Score in Patients who Decreased/Discontinued Steroids – Mean Changes from DB Baseline and Figure: QMG Total Score in Patients who Decreased/Discontinued Steroids – Mean Changes from DB Baseline)

Phase 2 VIVACITY-MG Study

Antozzi et al (2024)^4,8  conducted a phase 2, randomized, multicenter, DB, PBO-controlled clinical trial to evaluate the safety, efficacy, PK, and 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 DB 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).
• Patients were required to continue stable dosing of allowed SOC therapy including acetylcholinesterase inhibitors, glucocorticoids, or nonsteroidal immunosuppressants throughout the study unless safety issues warranted a change.
• The primary efficacy endpoint was change from baseline to day 57 in the total MG-ADL score.

Results

• A total of 68 patients (IMAAVY, n=54; PBO, n=14) were randomized to treatment.
• At baseline, 68.5% and 78.6% of patients were on concomitant glucocorticoid therapy in the combined IMAAVY group and PBO group, respectively (See Table: Baseline Corticosteroid Use in the Safety Population).⁸

Vibrance-mg Study

Ramchandren et al (2022)^6,9 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. 

Study Design/Methods

• Patients with anti-AChR or anti-MuSK antibody positive gMG (MGFA Class IIa-IVb) were included in the study.
• The study consists of a screening period of up to 4 weeks, a 24-week open-label active treatment phase where adolescent (12 to <18 years of age) patients will receive IMAAVY 30 mg/kg intravenous loading dose at week 0 followed by 15 mg/kg Q2W from week 2 to 22 in addition to SOC. Patients will have the option to enroll in a long-term extension phase.
  • A safety follow-up assessment will be conducted 8 weeks after the last dose.
• The primary efficacy endpoint was the effect of IMAAVY on total serum IgG at week 24.

Results

Strober et al (2024)⁵  presented results through the active treatment phase (study day 1 through week 24) in adolescents (aged 12 to <18 years) with a clinical cutoff date of December 15, 2023.

• Seven adolescent patients, all with anti-AChR antibody positive gMG were included in the analysis.
• At baseline, a total of 71.4% (5/7) adolescent patients were on concomitant corticosteroid therapy.

Literature Search

A literature search of MEDLINE^®, EMBASE^®, BIOSIS Previews^®, and DERWENT^® (and/or other resources, including internal/external databases) was conducted on 21 April 2025.