Inclusion Criteria:
1. Aged 19 years or older and younger than 80 years at the time of screening (male or female).
2. Diagnosed with Crohn's disease at least 6 months prior to screening, confirmed by imaging, tissue sampling (biopsy), and/or colonoscopy.
3. Have had an inadequate response to at least 6 months of standard treatment for Crohn's disease (such as anti-inflammatory drugs, oral corticosteroids, immunosuppressants, or biologic agents). Inadequate response means failure to achieve ulcer-free endoscopy, defined as an SES-CD Ulcerated Surface Score of 0 or 1.
4. Have active daily symptoms at screening and right before treatment, defined as either an average of 4 or more loose/liquid stools per day or an average daily abdominal pain score of 2 or more, based on the corresponding CDAI components.
5. Meet all of the following colonoscopy findings at screening:
* Have at least one active ulcer in an accessible area of the intestine (such as the colon or ileocecal region).
* Have at least one ulcer with a longest diameter of 5 mm or larger.
* Have an active ulcer segment with an endoscopic severity score (SES-CD) of 6 or higher, with an ulcer size score of 2 or higher and no narrowing or blockage (stricture score of 0) in that area.
6. Meet all required blood test standards for cell therapy donor eligibility.
7. Voluntarily agree to participate and sign the written informed consent form after receiving a full explanation of the study.
Exclusion Criteria:
1. Other Inflammatory Bowel Conditions: Diagnosed with ulcerative colitis or unclassified colitis.
2. Surgical Needs: Require, or are expected to require, surgery for Crohn's disease or its complications.
3. Severe Co-existing Conditions: Have a severe autoimmune disease other than Crohn's disease, or an active abdominal/perianal condition (such as an undrained abscess or active fistula).
4. Recent Surgeries: Had bowel resection within 6 months or intra-abdominal surgery within 3 months prior to screening.
5. Procedure Inability: Unable to safely undergo bowel preparation, colonoscopy, or sedation, or have a known allergy/contraindication to medications used during these procedures.
6. Uncontrolled Medical Issues: Have a clinically significant or poorly controlled medical condition, such as severe heart, bleeding, kidney, or liver disease, or uncontrolled diabetes.
7. Active Severe Infection: Have an active, severe infection requiring ongoing medical treatment.
8. Cancer History: Have a history of cancer (malignancy) within 5 years before screening, except for specific low-risk cancers permitted by the protocol.
9. Allergies to Study Treatment: Have a known severe allergy (hypersensitivity) to ATORM-C, its ingredients, or materials used in its manufacturing.
10. Prohibited Therapies or Transplants: Are taking prohibited medications, have previously received any cell therapy product, or have received an organ transplant (except corneal transplant).
11. Significant Blood Test Abnormalities: Have severe laboratory test abnormalities, including liver function (AST or ALT ≥3 times the upper limit of normal), kidney function (eGFR \<30 mL/min/1.73 m²), bleeding markers (PT INR \>1.5), or low blood platelets (\<50,000/mm³).
12. Pregnancy, Breastfeeding, or Contraception: Are pregnant, breastfeeding, or unwilling to follow the protocol-specified contraception requirements during the study.
13. Recent Clinical Trials: Received another investigational drug or device within 4 weeks prior to screening.
14. Investigator Judgment: Deemed unsuitable for participation by the study investigator for any other safety reason.
