Chimeric antigen receptor (CAR) T cell therapies have demonstrated remarkable efficacy in hematologic malignancies; however, their clinical benefit in solid tumors remains limited. A major barrier is T cell dysfunction, particularly exhaustion and senescence, which impair persistence, effector function, and durable tumor control. Targeting these dysfunctional states is therefore essential in order to improve CAR T cell efficacy in solid tumors.This review summarizes recent preclinical strategies aimed at preventing or reversing CAR T cell exhaustion and senescence in solid malignancies. While both exhaustion and senescence are relevant dysfunctional states, the preclinical evidence summarized in this review is currently more extensive for modulation of exhaustion-associated programs than for direct reversal of canonical T cell senescence. Approaches are organized according to their primary mechanistic focus, including gene editing, metabolic modulation, receptor redesign, and remodeling of the tumor microenvironment.Across these mechanistic categories, reported benefits include enhanced CAR T cell persistence, reduced expression of inhibitory receptors, such as PD-1, LAG-3, and TIM-3, preservation or restoration of memory-like phenotypes, and improved antitumor cytotoxicity. Notably, combinatorial strategies targeting multiple dysfunction pathways consistently demonstrate superior efficacy in preclinical models. Despite these advances, important translational challenges remain, including the limited predictive value of current preclinical systems, potential safety concerns, and the manufacturing complexity associated with increasingly engineered cell products.Collectively, preclinical evidence supports the rational integration of complementary approaches to generate next-generation CAR T cells capable of resisting dysfunction and maintaining activity within immunosuppressive solid tumor microenvironments. Further validation in clinically relevant models will be critical to facilitate translation into safe and durable cancer immunotherapies.

Adoptive T cell therapy holds great promise for the treatment of solid tumors but remains constrained by tumor heterogeneity, inefficient neoantigen targeting, and the complexity of T cell manufacturing. Here, we present a patient-specific, broadly applicable platform using physically inactivated tumor organoids (PIOs) to generate tumor-specific cytotoxic T cells ex vivo. Derived from droplet-engineered tumor organoids (DEOs), PIOs preserve the full antigenic repertoire of the patient's tumor without requiring synthetic peptides, antigen-presenting cells, or neoantigen prediction. Using matched tumor tissue and PBMCs from colorectal and liver cancer patients, we show that PIOs activate and expand tumor-specific T cells with enhanced infiltration, selective cytotoxicity, and robust secretion of IFN-γ and IL-2. Multi-round PIO stimulation achieves 80-400-fold expansion of CD8+CD137+ T cells within two weeks. Transcriptomic and epigenetic profiling suggest that PIOs modulate T cell programs linked to migration and persistence. This work redefines tumor organoids as immunotherapeutic materials and establishes a rapid, cost-effective platform for personalized T cell manufacturing. Our findings provide a new translational route for adoptive cell therapy in solid tumors using patient-derived materials.

Armed oncolytic adenovirus elicits a "self-feeder" effect to supercharge NK cells for solid tumor control.

Chimeric antigen receptor (CAR)-T-cell therapies have shown remarkable clinical efficacy in hematological malignancies. However, objective clinical responses in solid tumors are limited. Various obstacles, such as the lack of ideal tumor-specific antigens and the immunosuppressive tumor microenvironment (TME), which impairs multiple immunological steps required to achieve effective cancer control, compromise the antitumor efficacy of CAR-T-cell therapy in solid tumors. To address this issue, combination treatment with oncolytic viruses (OVs) and CAR-T cells is being explored. OVs can modulate immunosuppression in the TME and invigorate both endogenous and adoptively transferred T cells, in addition to directly killing tumor cells. The immunomodulatory effect is further augmented by the use of OVs with therapeutic transgenes as payloads. Many preclinical evaluations have provided promising evidence for the combination approach, and clinical studies are ongoing. In this review, the mechanisms underlying resistance to CAR-T-cell therapies and recent advances in combination therapy with OVs and CAR-T cells are discussed from the perspective of the cancer-immunity cycle.

Chimeric antigen receptor (CAR) therapies have revolutionized cancer immunotherapy, particularly in hematologic malignancies, but their efficacy in solid tumors remains limited. Key barriers include tumor antigen heterogeneity, on-target/off-tumor toxicity, impaired trafficking, and an immunosuppressive tumor microenvironment. We conducted a narrative review of preclinical and clinical studies investigating CAR-engineered innate and innate-like immune cells, including CAR-natural killer, CAR-γδ T, CAR-natural killer T (NKT), and CAR-macrophages, focusing on their biological features, therapeutic potential, and current clinical development in solid tumors. These alternative platforms exhibit distinct advantages over conventional CAR-T cells, including reduced risk of severe toxicities, improved trafficking, overcoming antigen loss, and higher allogeneic potential. Emerging clinical data suggest favorable safety profiles, although limited persistence and variable efficacy remain key challenges. Advances in cell engineering, such as cytokine armoring and non-viral gene transfer, are further enhancing their therapeutic potential. CAR-engineered innate and innate-like immune cells represent a promising next-generation strategy to overcome the limitations of conventional CAR-T therapies in solid tumors. Among these, CAR-NKT and CAR-γδ T cells may offer particular advantages for clinical translation, warranting further investigation in future trials.

A major limitation in applying chimeric antigen receptor (CAR) T cells to solid tumors is toxicity in healthy tissues caused by a lack of tumor-specific targets. A promising strategy to overcome this deleterious cytotoxicity is to engineer control into CAR T cells beyond that conferred by antigen recognition alone. In a recent issue of Nature Chemical Biology, Scheller and colleagues report the development of a CAR that is inactivated through introducing the small molecule, venetoclax, which is a clinically approved targeted Bcl-2 inhibitor. The authors design venetoclax-dependent release of the CAR extracellular binding domain, thereby disrupting T cell contact with tumor cells and suppressing cytotoxicity. Furthermore, they demonstrate the reversibility of this approach, as withdrawal of the drug restores CAR T cell function. This work establishes a foundation for clinically translatable remote-controlled CAR T cell therapy for solid tumors.

One recurring challenge in cell therapy for solid tumors is poor tumor infiltration of adoptively transferred T cells. We previously showed that a subablative dose of tumor-targeted radiation generates a chemokine gradient that promotes infiltration, proliferation, and a memory phenotype of chimeric antigen receptor (CAR) T cells in solid tumors. However, radiation is cytotoxic to infiltrating CAR T cells, limiting its repeated use. We hypothesized that irreversible electroporation could generate a chemokine gradient that promotes CAR T-cell infiltration into solid tumors and that selective irreversible electroporation (sIRE) tuned for selective cancer cell lysis (thus, sparing infiltrating CAR T cells) can be used in a repeated fashion. Using experimental screening and simulation models, we optimized sIRE parameters to kill cancer cells while sparing T cells. Using 3D tumor mimics and mouse models of malignant pleural mesothelioma, we confirmed the therapeutic benefit of repeated sIRE. Chemokine secretion by cancer cells injured by sIRE promoted migration and tumor infiltration of systemically administered CAR T cells and facilitated sustained immunity in a tumor-rechallenge model. By leveraging a dual-purpose translational strategy-through direct cancer cell-targeted cytotoxicity and augmented CAR T-cell infiltration-sIRE can reduce cancer burden while preserving and enhancing CAR T-cell function.

Adoptive T cell therapy (ACT) remains limited in solid tumors by poor T cell persistence within the metabolically hostile tumor microenvironment (TME). Although IL-9-producing CD8+ T cells (Tc9) consistently demonstrate superior antitumor efficacy compared with conventional Tc1 cells, the selective pressures that shape their functional advantage remain unclear. Here, we show that effective ACT-mediated tumor control is accompanied by a marked increase in intratumoral extracellular ATP (eATP), representing a common metabolic consequence of tumor cell destruction. Despite comparable ATP accumulation following Tc1 or Tc9 treatment, these subsets exhibit strikingly distinct responses to ATP stress. Tc1 cells are highly susceptible to ATP-induced apoptosis, whereas Tc9 cells display intrinsic resistance, resulting in superior in vivo persistence. Mechanistically, Tc9 cells actively convert ATP signaling into enhanced mitochondrial fitness, characterized by increased oxidative phosphorylation and spare respiratory capacity. ATP exposure further drives Tc9 cells toward a tissue-resident memory (TRM) phenotype through activation of the TGF-β signaling axis. Transcriptomic and molecular analyses reveal that purinergic signaling pathways, including elevated expression of the ATP receptor P2RX7, are intrinsically enriched in Tc9 cells and are further amplified upon ATP stimulation. Collectively, our findings identify extracellular ATP as a metabolic lineage selection signal in ACT, demonstrating that ATP stress preferentially stabilizes metabolically resilient Tc9 cells by linking purinergic sensing to mitochondrial remodeling and TRM programming, thereby providing a conceptual basis for enhancing the persistence and efficacy of engineered T cell therapies in solid tumors.

Chimeric antigen receptor (CAR)-T cell therapy faces significant challenges in treating solid tumors, primarily due to the immunosuppressive tumor microenvironment (TME) and rapid T-cell exhaustion mediated by cytokines such as transforming growth factor-β (TGF-β). Developing strategies to remodel the TME and sustain T-cell function is critical. In this study, we investigated a pharmacological strategy using Asiaticoside (AC), a natural compound, as an adjuvant to enhance the efficacy of mesothelin (MSLN)-targeting CAR-T cells in ovarian cancer. We engineered MSLN-specific CAR-T cells and evaluated their therapeutic efficacy in combination with AC using in vitro co-culture assays and in vivo xenograft models. Transcriptional changes were analyzed via RNA sequencing (RNA-seq), while the underlying molecular mechanism was investigated by focusing on the TGF-β/SMAD signaling axis. In vivo efficacy and safety were evaluated in NCG mice bearing subcutaneous or intraperitoneal metastatic SKOV-3-luc ovarian tumors, treated with the combination of CAR-T cells and AC. AC treatment significantly potentiated CAR-T cell cytotoxicity and reduced the expression of exhaustion markers (PD-1, TIM-3, and LAG-3) upon continuous antigen exposure. Mechanistically, AC functioned as an inhibitor of TGF-β signaling, effectively suppressing TGF-β1-induced phosphorylation of SMAD2/3. In mouse models, the combination of AC and CAR-T therapy exerted superior antitumor activity compared to CAR-T monotherapy, significantly suppressing tumor growth without inducing systemic toxicity or organ damage. Our findings demonstrate that AC alleviates CAR-T cell exhaustion and antagonizes TGF-β-mediated immunosuppression. AC represents a promising, clinically translatable pharmacological adjuvant to overcome the bottlenecks of CAR-T cell therapy in solid tumors.

CDK4/6 inhibitors promote anti-tumor immunity through diverse mechanisms, positioning them as promising adjuvants to cancer immunotherapies. While CDK4/6 inhibitors have demonstrated strong synergy with immune checkpoint inhibitors across numerous preclinical cancer models, their combination with CAR-T cell therapy remains unexplored. In this study, we examined the efficacy of combined CDK4/6 inhibition (trilaciclib) and CAR-T therapy across a range of preclinical blood and solid cancer models. In vitro, trilaciclib enhanced human CAR-T cell cytotoxicity and metabolic fitness while reducing expansion. In vivo, the combination outperformed single agents against retinoblastoma protein (RB)-proficient, trilaciclib-sensitive CD19+ leukemia. However, in an equivalent RB-deficient model, the combination therapy was no more effective than CAR-T cells alone, suggesting that enhanced CAR-T cell function may be offset by reduced expansion. In contrast, in solid cancer models the combination was consistently more efficacious than either monotherapy. Notably, combination effects were most pronounced in immunocompetent mouse models, including a model with poor sensitivity to trilaciclib as a monotherapy. Mechanistically, CDK4/6 inhibition reduced tumor-infiltrating T-regulatory cells while enhancing CD8+ CAR-T cell persistence, tumor trafficking, and cytotoxic function within the tumor. Together, these findings suggest that trilaciclib and CAR-T cell therapy may be an effective combinatorial treatment for solid cancers.

Engineering optimal CAR constructs for allogeneic mesothelin-directed CAR-NKT cells in solid tumor immunotherapy

Chimeric antigen receptor (CAR) T cell therapy for solid tumors remains challenging. This phase 1, open-label, dose-escalation and expansion study (ClinicalTrials.gov registration: NCT05396300 ) evaluated the safety and efficacy of PC13, a hypoxia-responsive, carcinoembryonic antigen (CEA)-targeted CAR T cell therapy, in persons with CEA-positive solid tumors. The primary endpoint was safety; secondary endpoints included efficacy, pharmacokinetics and pharmacodynamics. A total of 43 heavily pretreated participants (46.5% with ≥4 prior lines) were assigned to receive PC13 through intraperitoneal (I.P., n = 17) or intravenous (I.V., n = 26) infusion on the basis of predominant metastatic sites. Grade 3 diarrhea occurred in 20.9% of participants and 76.7% experienced grade 1 or 2 cytokine release syndrome. Disease control rates were 82.4% in the I.P. group and 68.0% in the I.V. group, with objective response rates (ORRs) of 23.5% and 8.0%, respectively. In post hoc analyses, ORRs reached 57.1% (4/7) in the I.P. group with peritoneal metastases and 40.0% (2/5) in the I.V. group without liver metastases, both among participants with CEA immunohistochemistry expression ≥ 90%. The predefined safety endpoint was met. PC13 demonstrated manageable toxicity and promising efficacy, supporting further investigations.

Chimeric antigen receptor (CAR) T-cell therapy has achieved significant success in hematologic malignancies, but its efficacy in solid tumors remains limited, primarily due to the immunosuppressive tumor microenvironment (TME) that hinders CAR-T cell trafficking and function. NKG2D CAR-T cells, which target stress-induced NKG2D ligands (NKG2DLs) broadly expressed on tumor cells, have shown promising potential in overcoming the immunosuppressive barriers of the solid TME. This review highlights recent advances in NKG2D CAR-T cell strategies for solid tumors, including innovations in CAR architecture, signaling pathway engineering, combination immunotherapy, and the development of armored CAR constructs. We further discuss the therapeutic potential, current challenges, and future directions of these approaches to inform the design of more effective and durable CAR-T cell therapies for solid tumors.

CAR-T cell therapy, which genetically modifies a patient’s T cells to express chimeric antigen receptors (CARs), has shown remarkable efficacy in treating blood cancers. However, its application to solid tumors is hindered by challenges such as inadequate tumor infiltration, an immunosuppressive microenvironment, and metabolic obstacles. This review explores potential targets for CAR-T cells in solid tumors and examines innovative strategies to enhance their tumor penetration, survival, and cytotoxicity. These include advanced CAR designs, combination therapies, and methods to improve CAR-T cell function amidst metabolic competition. As research and technology progress, CAR-T therapy holds promise as a viable option for solid tumor treatment, with future efforts emphasizing interdisciplinary collaboration to unlock its full potential.

Antigen heterogeneity remains a major obstacle to the effective application of chimeric antigen receptor (CAR)-T cell therapy in solid tumors. We investigated the potential of epitope spreading as a strategy to overcome this limitation and examined whether CAR-T cells concomitantly producing IL-7 and CCL19 (7 × 19 CAR-T cells) could act as potent inducers of epitope spreading, as well as the underlying mechanisms. We used a murine model inoculated with a mixture of cancer cell lines—genetically modified to express the CAR target antigen—and their respective parental lines lacking target expression. Following administration of 7 × 19 CAR-T cells, flow cytometry and peptide stimulation assays were performed to evaluate the induction of tumor antigen-specific T cells and dendritic cells within tumor-draining lymph nodes and tumor tissues. We also evaluated the antitumor efficacy of 7 × 19 CAR-T cells derived from an allogeneic donor and their capacity to induce epitope spreading in vivo and ex vivo. In multiple tumor mixture models, 7 × 19 CAR-T cells demonstrated marked antitumor activity and promoted epitope spreading in murine solid tumor models, enabling endogenous T cells to recognize and target tumor-associated antigens. This response was dependent on cross-presentation by defined dendritic cell subsets in both the tumor microenvironment and tumor-draining lymph nodes within 2 weeks of 7 × 19 CAR-T cell administration. Notably, 7 × 19 CAR-T cells derived from allogeneic donors also induced epitope spreading in tumor-bearing hosts, thereby increasing survival. The 7 × 19 CAR system is a promising strategy for overcoming antigen heterogeneity in solid tumors by promoting epitope spreading.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00262-026-04316-z.

Adoptive natural killer (NK) cell therapy for solid tumors faces critical challenges, including tumor antigen heterogeneity, impaired tumor infiltration, and suboptimal activation imposed by the immunosuppressive microenvironment. Here we developed an engineered nanoplatform featuring transmembrane DNA nanochannel-engineered artificial receptors (NCAR) to direct NK cells against solid tumors through two synergistic mechanisms: 1) Tumor Microenvironment (TME) Reprogramming: leveraging cholesterol-mediated insertion, NCAR incorporates into tumor membranes to disrupt phospholipid bilayers, inducing immunogenic cell death with the release of damage-associated molecular patterns (DAMPs; e.g., HMGB1, CRT), which remodels immunosuppression TME and recruits/activates NK cells. 2) Precision Targeting: NCAR forms programmable synthetic immune synapses with DNA nanoartificial ligands (NAL) engineered on NK cells via base-pairing. This antigen-independent assembly network establishes a universal membrane interface, enabling sustained tumor-targeted NK cell activation. The dual-component system enables sustained intratumoral accumulation of NK cells (>96 h), with a 15.1-fold increase in activated NKP46+GZB+ NK cells compared to controls. By bridging DNA nanotechnology with cell immunotherapy, our nanoplatform provides a universal strategy for navigating tumor-immune interactions, addressing key limitations of adoptive NK cell immunotherapy in solid tumors.

Advancing Cell Therapies for Solid Tumors: A Pathway to Overcome Biological, Operational, and Regulatory Hurdles.

Current state of CAR-T cell therapies for solid tumors.

IMPACTFUL Adoptive T Cell Therapy In their Research Article (DOI: 10.1002/adma.202510842), Mingqiang Li, Yu Tao, Haochen Yao, and co-workers present an immuno-packed T-cell-fusogenic liposome (IMPACTFUL) that enables T-cell engineering through membrane fusion. This approach facilitates concurrent targeting across multiple cellular compartments, including the cell membrane and cytoplasm. By leveraging this dual-targeting strategy, T cells acquire enhanced functionalities, such as improved tumor infiltration, overcoming immune tolerance, and reversing the immunosuppressive tumor microenvironment. This versatile platform offers a promising approach to enhance the therapeutic efficacy of adoptive T cell therapies for solid tumors.

Engineering a fifth-generation CAR T cells to overcome PD-L1-mediated immunosuppression in lung cancer.