Descartes-08 in Autoantibody Myositis

Inclusion Criteria:

* Confirmed diagnosis of one of the following:

Dermatomyositis (DM): Probability score ≥55% on the 2017 EULAR/ACR (European Alliance of Associations of Rheumatology/ American College of Rheumatology) criteria for classification of dermatomyositis (corresponding to diagnosis of 'probable or definite' DM). OR Antisynthetase Syndrome (ASyS): Diagnosis based on ACR/EULAR Classification Criteria (1)."

* Participants must have dermatomyositis or antisynthetase syndrome with muscle and/or skin involvement.
* Refractory or intolerance to standard therapy.
* Stable background immunosuppressive therapy for ≥8 weeks.
* Adequate hematologic, renal, hepatic, and pulmonary function (SpO₂ ≥92% on room air).
* Informed consent, compliance with visits, contraception, and vaccinations required.

Exclusion Criteria:

* Isolated interstitial lung disease (ILD) without muscle or skin involvement

  * Severe irreversible muscle damage or advanced weakness (e.g., wheelchair-bound).
  * Interstitial lung disease (ILD) requiring oxygen, severe pulmonary impairment (FVC ≤45%, DLCO ≤40%), or pulmonary hypertension.
  * Other inflammatory myopathies (PM, IMNM, IBM, cancer- or drug-induced myositis, overlap myositis except Sjögren's).
  * Other severe neuromuscular, cardiac, pulmonary, or systemic autoimmune diseases requiring immunosuppression.
  * Significant uncontrolled chronic illnesses or psychiatric conditions interfering with participation.
  * Pregnancy or lactation.
  * Recent use of prohibited immunosuppressants/biologics or investigational agents (per washout periods).
  * Live vaccination within 4 weeks.
  * History of primary immunodeficiency, organ or bone marrow transplant.
  * Active or uncontrolled infections: HBV, HCV, HIV, tuberculosis, or recurrent/severe infections.