GC012F Injection in Refractory Idiopathic Inflammatory Myopathy

Inclusion Criteria: * 1\) The subject or his/her legally acceptable representative voluntarily signs the written informed consent form and is willing and able to comply with the procedures of this study; 2) Aged 18 to 70 years (inclusive) at the time of signing informed consent, male or female; 3) Patients should meet the following criteria: 1. Subjects with suspected or confirmed idiopathic inflammatory myopathy (IIM) based on the 2017 European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) classification criteria and at least one proximal limb muscle strength of less than or equal to Grade 4; patients with immune-mediated necrotizing myopathy (IMNM) may be included if he/she meets other inclusion criteria and does not meet all exclusion criteria and the investigator assesses that the patient has no safety instability; 2. Active myositis on muscle biopsy or muscle magnetic resonance imaging (MRI) within the screening period or within 6 months prior to screening; 3. Positive (+ or above) for at least one myositis-specific antibody (MSA) or myositis-associated antibody (MAA) (including anti-TIF-1γ, NXP-2, Mi-2α, Mi-2β, MDA-5, SAE-1/2, SRP, HMGCR, Jo-1, PL-7, PL-12, HA, EJ, OJ, KS, Zo, PM-Scl100, PM-Scl75, SSA/Ro-52, SSB/LA, Ku, RNA-PIII, cN1A, etc.); 4. At screening, the subject must have moderate to severe IIM, defined as manual muscle testing (MMT) \< 142 and 2 of the following criteria are met: * PGA (VAS) ≥ 2 cm (VAS 10 cm scale); * PtGA (VAS) ≥ 2 cm (VAS 10 cm scale); * Health assessment questionnaire (HAQ) \> 0.25; * Increase in one or more muscle enzymes (CK, LDH, AST, ALT) is ≥ 1.5 × ULN; * Extramuscular global assessment (Myositis Disease Activity Assessment Tool \[MDAAT\]) ≥ 2.0 cm (VAS 10 cm scale); 4) Muscle enzyme increased (CK) ≥ 2 × ULN; 5) Inadequate response or intolerance to corticosteroids and at least 2 immunosuppressants and/or biologic agents; 6) If the patient is taking corticosteroids, the dose of prednisone should not exceed 40 mg/day (or equivalent dose of other corticosteroids) within 3 weeks before apheresis, and the dose is not uptitrated within 3 weeks before apheresis and not changed within 4 weeks before infusion (Note: under the premise that the subject's disease under study is controlled, the investigator may consider reducing the dose of corticosteroids before apheresis, lymphodepletion, and infusion); 7) Life expectancy ≥3 months; 8) Laboratory test results must meet the following criteria at screening (except for those related to the corresponding disease under study): <!-- --> 1. Neutrophil count \> 1.0 × 10\^9/L, Hemoglobin ≥ 80g/L, platelet count ≥ 50 × 10\^9/L; 2. Alanine aminotransferase ≤ 3 × upper limit of normal (ULN); aspartate aminotransferase ≤ 3 × ULN (unless the increases in alanine aminotransferase and/or aspartate aminotransferase are assessed by the investigator as related to polymyositis \[PM\] or dermatomyositis \[DM\]); total bilirubin (TBIL) \< 2 × ULN (direct bilirubin \[DBIL\] ≤ 1.5 × ULN for subjects with Gilbert's syndrome); 3. Creatinine clearance ≥ 60 ml/min; 4. Activated partial thromboplastin time (aPTT) ≤ 1.5 × ULN, prothrombin time (PT) ≤ 1.5 × ULN; 5. Left ventricular ejection fraction (LVEF) ≥ 50% as diagnosed by echocardiogram, with no evidence of pericardial effusion as determined; 9) Women of childbearing potential must: <!-- --> 1. Have a negative serum β-human chorionic gonadotropin (β-hCG) pregnancy test result at screening as confirmed by the investigator; 2. Agree to avoid breastfeeding during the study period and until at least 2 years after infusion of GC012F Injection, or until two consecutive flow cytometry tests indicate that CAR-T cells are no longer present (whichever occurs later); 10) Male subjects with sexual partners and female subjects of childbearing potential must agree to use highly effective contraception methods (e.g., oral contraceptives, intrauterine devices, or condoms) starting from screening and continuing for at least 2 years after GC012F Injection infusion or until two consecutive flow cytometry tests indicate that CAR-T cells are no longer present (whichever occurs later). Male subjects must agree to use condoms during any sexual contact with pregnant women or women of childbearing potential for at least 2 years after GC012F Injection infusion, even if they have undergone successful vasoligation. 11\) The required venous access for collection can be set up, with no contraindications for leukapheresis. Exclusion Criteria: * 1\) Documented inclusion body myositis (IBM), drug-induced PM or DM, tumor-related PM or DM, amyopathic DM, non-inflammatory myopathy (e.g., muscular dystrophy); for patients with PM or DM, they were \> 40 years of age at onset of PM or DM symptoms and the diagnosis time is less than 3 years, and the investigator considered a possible malignancy based on the patient's clinical presentation; 2) Uncontrolled extramuscular disease impairment associated with PM or DM: 1. Interstitial lung disease (ILD): Forced vital capacity (FVC) \< 55% or requiring oxygen therapy; 2. Severe dysphagia manifestations, that will increase the risk associated with the patient's participation in the clinical trial, as judged by the investigator; 3. Severe cardiac manifestations (e.g., congestive heart failure, arrhythmia, conduction abnormality requiring treatment or myocardial infarction) that, in the judgment of the investigator, will increase the risk associated with the patient's participation in the clinical trial; 3) Patients with severe muscle injury who meet one of the following criteria: <!-- --> 1. Myositis damage index (MDI) ≥ 5; 2. Severe proximal muscle atrophy of the upper or lower extremities as shown on MRI; 3. Severe proximal muscle atrophy of the upper or lower extremities as found by clinical examinations; 4) History of severe hypersensitivity or allergy; 5) Contrain