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.