Beyond Hematology—Current Insights into Chimeric Antigen Receptor (CAR) T-Cell Therapy for Skin and Connective Tissue Disorders

Chimeric antigen receptor (CAR) T-cell therapy represents a major advance in modern immunotherapy. This narrative review summarizes evidence from the past five years, including case reports, case series, and clinical trials, on its application beyond hematologic malignancies, focusing on autoimmune diseases such as systemic lupus erythematosus (SLE), systemic sclerosis (SSc), as well as solid tumors including melanoma and primary cutaneous lymphomas. CD19-directed CAR T-cells have demonstrated clinical benefits in SLE and SSc, with sustained immune reset, reduced autoreactive antibody levels, and clinical improvement. In melanoma, CAR T-cells targeting GD2, cMET, and CD20 have shown in vivo expansion and tumor infiltration; however, clinical efficacy remains limited, with transient stabilization or disease progression in most patients. In primary cutaneous lymphomas, early-phase studies with anti-CD70 and anti-CCR4.30 CAR T-cells indicate partial tumor regression and disease stabilization, often requiring additional therapy. Key challenges include limited durability of immune reset due to persistent plasma cells in autoimmune disorders, tumor heterogeneity, antigen loss or overlap, infiltration barriers, resistance mechanisms, and T-cell depletion in solid tumors, collectively reducing response durability and safety. The main toxicities include grade 1–2 cytokine release syndrome and rare hematologic complications, while immune effector cell-associated neurotoxicity syndrome is uncommon. Clinical translation remains limited and requires larger studies to improve efficacy and define safety profiles.