Cellular Therapies in Solid Tumors: Are We Ready for Primetime?

Adoptive cellular immunotherapy (ACT) has revolutionized hematologic malignancies, yet translation to solid tumors has historically been limited. This landscape shifted significantly in 2024 with US Food and Drug Administration approvals of lifileucel, a tumor-infiltrating lymphocyte (TIL) therapy for advanced melanoma, and afamitresgene autoleucel, an engineered T-cell receptor (TCR) therapy for synovial sarcoma. These approvals mark the clinical arrival of ACT for solid tumors and highlight a rapidly expanding therapeutic landscape. Beyond these indications, multiple ACT platforms including TIL, TCR, chimeric antigen receptor (CAR) T-cell, CAR-natural killer, and CAR-macrophage therapies are under active clinical investigation across diverse solid tumor indications. Clinical experience to date has defined key barriers to efficacy, including impaired tumor trafficking, antigen heterogeneity, immunosuppressive tumor microenvironment, and limited cellular persistence. In parallel, rapid advances in cellular engineering are reshaping the field, with the development of armored constructs, logic-gated and multiantigen targeting strategies, innate immune-based platforms, and novel manufacturing approaches including allogeneic and in vivo cell engineering. As ACT enters clinical practice for select solid tumors, distinct toxicity profiles and logistical requirements necessitate careful patient selection and multidisciplinary coordination. Early biomarker testing, timely referral to specialized centers, and familiarity with evolving toxicity management frameworks are increasingly critical. Here, we seek to provide a practice-oriented framework for understanding emerging ACT platforms, clinical data, toxicity considerations, and implementation strategies relevant to contemporary solid tumor oncology care.