This clinical trial is designed as a single-arm, open-label, single-center investigator-initiated early-phase study, with the primary objective of evaluating the safety of UTAA91 injection in subjects with refractory moderate-to-severe active systemic sclerosis.

Inclusion Criteria:

• Aged ≥18 years (inclusive of the boundary value), with no restriction on gender.
• Expected survival time of ≥3 months.
• Refractory moderate - to - severe active systemic sclerosis that has failed standard treatment or lacks effective therapeutic options.
• Meets the requirements for liver and kidney function, as well as cardiopulmonary function.
• Free from severe psychiatric disorders.
• Able to understand the trial and has signed the informed consent form.

Exclusion Criteria:

• A history of malignant tumors other than relapsed/refractory autoimmune diseases (R/R AID) within 5 years prior to screening.
• Positive results in virology/syphilis tests.
• Severe cardiac diseases or unstable systemic diseases.
• Presence of active or uncontrollable infections requiring systemic treatment, or evidence of central nervous system invasion.
• Pregnant or breastfeeding women, female subjects planning to become pregnant within 2 years after cell infusion, or male subjects whose partners plan to become pregnant within 2 years after their cell infusion.
• Subjects who have received CAR - T therapy or other gene - modified cell therapies prior to screening.
• Subjects who participated in other clinical studies within 1 month prior to screening.
• Other conditions deemed unsuitable for enrollment by the investigator.