RESET-Myositis: An Open-Label Study to Evaluate the Safety and Efficacy of CABA-201 in Subjects With Active Idiopathic Inflammatory Myopathy or Juvenile Idiopathic Inflammatory Myopathy

Adult Cohorts

Inclusion Criteria:

• Age ≥18 and ≤75

• A clinical diagnosis of IIM, based on the 2017 The European League AgainstRheumatism/American College of Rheumatology classification criteria

• Diagnosis of DM, ASyS, IMNM based on the presence of serum myositis-specificantibodies

• Evidence of active disease, despite prior or current treatment with standard of caretreatments, as defined by the presence of elevated creatine kinase (CK), DM rash, oractive disease on muscle biopsy, magnetic resonance imaging (MRI), orelectromyography

• Presence of muscle weakness

Exclusion Criteria:

• Contraindication to leukapheresis

• History of anaphylactic or severe systemic reaction to fludarabine, cyclophosphamideor any of their metabolites

• Active infection requiring medical intervention at screening

• Current symptoms of severe, progressive, or uncontrolled renal, hepatic,hematological, gastrointestinal, pulmonary, psychiatric, cardiac, neurological, orcerebral disease, including severe and uncontrolled infections, such as sepsis andopportunistic infections.

• Concomitant medical conditions that, in the opinion of the investigator, might placethe subject at unacceptable risk for participation in this study, interfere with theassessment of the effects or safety of the investigational product or with the studyprocedures

• Significant lung or cardiac impairment

• Previous CAR T cell therapy

• Prior solid organ (heart, liver, kidney, lung) transplant or hematopoietic celltransplant

Juvenile Cohort

Inclusion Criteria:

• Age ≥6 and ≤17 years at enrollment

• A clinical diagnosis of IIM, based on the 2017 The European League AgainstRheumatism/American College of Rheumatology classification criteria

• Presence of serum myositis-specific antibodies or myositis-associated autoantibody

• Evidence of active disease, despite prior or current treatment with standard of caretreatments, as defined by the presence of elevated muscle enzymes, DM rash, oractive disease on muscle biopsy, magnetic resonance imaging (MRI), orelectromyography

Exclusion Criteria:

• Contraindication to leukapheresis

• History of anaphylactic or severe systemic reaction to fludarabine, cyclophosphamideor any of their metabolites

• Active infection requiring medical intervention at screening

• Current symptoms of severe, progressive, or uncontrolled renal, hepatic,hematological, gastrointestinal, pulmonary, psychiatric, cardiac, neurological, orcerebral disease, including severe and uncontrolled infections, such as sepsis andopportunistic infections.

• Concomitant medical conditions that, in the opinion of the investigator, might placethe subject at unacceptable risk for participation in this study, interfere with theassessment of the effects or safety of the investigational product or with the studyprocedures

• Significant lung or cardiac impairment

• Previous CAR T cell therapy

• Prior solid organ (heart, liver, kidney, lung) transplant or hematopoietic celltransplant