Comparison of experimental tumor growth curves with model predictions to define baseline values of model parameters.

BACKGROUND:Antibody-drug conjugates (ADCs) and bispecific antibodies represent a rapidly advancing frontier in oncology, yet the abnormal tumor microenvironment (TME) hinders their delivery and reduces efficacy. Emerging immunomodulatory ADCs (IM-ADCs) demand mechanistic mathematical models that couple drug transport with immune dynamics. METHODS:Here, we present a mechanistic framework for the delivery of HE-S2 ADC, an anti-programmed cell death ligand 1 (PD-L1) antibody bearing the bifunctional immunomodulator D18. Our model integrates cancer-immune cells interactions, TME properties, such as dysfunctional vessels, elevated interstitial fluid pressure, tissue hydraulic conductivity, and vascular permeability, spatiotemporal distributions across growing tumor and adjacent host tissue, convective-diffusive transport, ADCs binding and internalization kinetics and tumor-draining lymph node biology governing antigen presentation and the generation of effector CD8+ T cells. Parameters were calibrated simultaneously with the murine MC38 and B16 tumor growth data and effector CD8+T cell data following treatment with D18, anti-PD-L1, and ADC. RESULTS:Our mechanistic spatiotemporal model captures the superior antitumor efficacy of the HE-S2 ADC relative to its individual components and provides mechanistic predictions for unmeasured variables, such as spatiotemporal dynamics of drug/immune-cell distributions. It explains reduced intratumoral D18 exposure via rapid clearance, while antibody/ADC achieves higher tumor retention through leaky tumor vasculature. The model suggests a reinforcing loop in which improved ADC exposure enhances CD8+T cell infiltration, driving tumor shrinkage that lowers fluid pressure and improves drug delivery. Parametric analyses findings support TME normalization strategies that increase functional vessel density prior to ADC administration; however, such approaches should preserve sufficient vascular permeability by maintaining vessel pore radius >~40 nm, ensuring pores remain large enough for ADC extravasation and effective intratumoral delivery. CONCLUSION:The proposed mechanistic model successfully captures how TME properties regulate the delivery and efficacy of IM-ADCs while suggesting TME normalization as a potential strategy to improve treatment outcomes.

PURPOSE:Neurofibromatosis type 2 (NF2) is a tumor predisposition syndrome characterized by bilateral vestibular schwannomas (VSs) resulting in deafness and brainstem compression. This study evaluated efficacy and biomarkers of bevacizumab activity for NF2-associated progressive and symptomatic VSs.PATIENTS AND METHODS:Bevacizumab 7.5 mg/kg was administered every 3 weeks for 46 weeks, followed by 24 weeks of surveillance after treatment with the drug. The primary end point was hearing response defined by word recognition score (WRS). Secondary end points included toxicity, tolerability, imaging response using volumetric magnetic resonance imaging analysis, durability of response, and imaging and blood biomarkers.RESULTS:Fourteen patients (estimated to yield > 90% power to detect an alternative response rate of 50% at alpha level of 0.05) with NF2, with a median age of 30 years (range, 14 to 79 years) and progressive hearing loss in the target ear (median baseline WRS, 60%; range 13% to 82%), were enrolled. The primary end point, confirmed hearing response (improvement maintained ≥ 3 months), occurred in five (36%) of 14 patients (95% CI, 13% to 65%; P < .001). Eight (57%) of 14 patients had transient hearing improvement above the 95% CI for WRS. No patients experienced hearing decline. Radiographic response was seen in six (43%) of 14 target VSs. Three grade 3 adverse events, hypertension (n = 2) and immune-mediated thrombocytopenic purpura (n = 1), were possibly related to bevacizumab. Bevacizumab treatment was associated with decreased free vascular endothelial growth factor (not bound to bevacizumab) and increased placental growth factor in plasma. Hearing responses were inversely associated with baseline plasma hepatocyte growth factor (P = .019). Imaging responses were associated with high baseline tumor vessel permeability and elevated blood levels of vascular endothelial growth factor D and stromal cell-derived factor 1α (P = .037 and .025, respectively).CONCLUSION:Bevacizumab treatment resulted in durable hearing response in 36% of patients with NF2 and confirmed progressive VS-associated hearing loss. Imaging and plasma biomarkers showed promising associations with response that should be validated in larger studies.

Supplementary Fig. S9: Expression levels of Cxcr3 and its ligands are increased in ICC tissues after GC/dual ICB treatment in murine 425-ICC.

Tumors acquire blood vessels primarily via sprouting angiogenesis and co-option of pre-existing host vasculature, but also via intussusception, vasculogenesis from bone-marrow-derived progenitors, vascular mimicry, and endothelial transdifferentiation. The abnormal structure and function of these vessels, resulting from an imbalance between pro- and anti-angiogenic signaling as well as from the physical forces, impair the delivery and efficacy of therapeutics. We review the evolving narrative of targeting angiogenesis from starving tumors to vascular normalization as a therapeutic principle and highlight recent spatial-omics revelations and the emerging role of neural, microbial, hormonal, and chronological factors. We elaborate on the molecular mechanisms of tumor vessel formation, how dysfunctional vessels cause an abnormal tumor microenvironment characterized by hypoxia, low pH, elevated fluid pressure, and immunosuppression, and how vascular normalization enhances the delivery and efficacy of various therapies, including immunotherapies, and has formed the basis of emerging strategies and novel therapeutic agents to improve patient outcomes.

Schematic of the mathematical model of tumor-immune system interactions, highlighting key immune components, their activation and cytolytic functions, and modulation by PD-1/PD-L1 signaling. The model also incorporates cytokine effects and the influence of immunosuppressive cells like M2 macrophages and Tregs.

Supplementary Fig. S8: Bulk tissue RNA sequencing analysis of ICC after GC/dual ICB combination therapy in orthotopic murine 425-ICC model.

Supplementary raw data of the results of the paper

Global sensitivity analysis. The coefficients of significant predictors (p-value<0.05 ANOVA) on the tumor volume before treatment in equation (3) of the main paper.

Supplementary Fig. S12: Effect of ICB treatment scheduling on efficacy and toxicity.

Supplementary Table S1: Antibody list.

Comparison of the components incorporated in our modeling framework with those incorporated in previously published pertinent models.

Supplementary Fig. S2: Standard chemotherapy converts ICB-resistant ICCs to ICB-responsive tumors, significantly delays tumor progression and increases survival in mice.

Supplementary Fig. S10: Schematic of the animal experiment design.

Supplementary Fig. S6: CTLA-4 blockade mediates the efficacy of GC/ICB therapy in ICC and increases CD8+CTL frequency in murine ICC.

Local sensitivity analysis. The logarithm of total variance for each parameter and treatment.

Model validation with clinical dataset.

Abstract Introduction: Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer-related death in the United States, with a 5-year overall survival of ∼13%. Delayed diagnosis, limited response to current treatments, and the predominance of locally advanced or metastatic disease contribute to poor outcomes. Leveraging our preclinical findings in PDAC murine models, we showed that adding losartan—an angiotensin II type-1 receptor (AT1) blocker—to FOLFIRINOX followed by chemoradiation doubled R0 resection rates to ∼70% in locally advanced PDAC in a phase II trial (NCT01821729) (PMID: 31145418). However, the patient-response was variable. Here we recapitulated this variability in orthotopic PDAC mouse models and revealed the underlying mechanism. Methods and Results: To investigate potential causes of the variable response, we mapped AT1 expression using light-sheet microscopy in AT1 reporter mice bearing orthotopic PDAC. We observed abundant AT1 throughout the tumor microenvironment. To define its functional relevance, we generated Agtr1a knockout (KO) PDAC cell lines and inducible KO mouse models. AT1 deletion in either cancer cells or stromal cells (but not α-SMA+ myCAFs or pericytes) significantly reduced tumor growth. Because losartan is a pro-drug that needs activation by liver enzymes CYP3A4 and CYP2C9, we next examined its metabolism. We subcutaneously administered two major losartan metabolites, EXP3179 and EXP3174, to orthotopic PDAC-bearing mice and found that EXP3174 mediated the anti-tumor effects of losartan. Mass spectrometry of plasma samples revealed that while some tumor-bearing mice efficiently converted losartan to its active metabolite, others showed limited or no conversion. To determine the cause, we assessed CYP2C9 and CYP3A4 activity in liver microsomes from non-metastatic PDAC-bearing mice. CYP2C9 activity was markedly reduced and inversely correlated with tumor burden, providing a mechanistic basis for differential losartan activation. Ongoing work aims to determine whether PDAC patients likewise display variable plasma levels of losartan and EXP3174. Conclusion: These findings identify impaired hepatic metabolism as a key driver of variable losartan responses in locally advanced PDAC. Mass-spectrometry-based assessment of losartan and EXP3174 levels may help determine which patients can effectively activate the drug. Given losartan’s safety and low cost, its oral administration remains appropriate for most patients; however, in individuals with compromised CYP2C9 activity, administration of the active metabolite — EXP3174 may represent a more effective therapeutic option. Citation Format: Heena Kumra, Ryo Morisue, Benjamin E. Wolf, Vasiliki Salameti, Sonu Subudhi, Nilesh P. Talele, Eric F. Zaniewski, Robert Morris, Tsion H. Tale, Karim El-Marouk, Cora Schueller, Mariagiovanna Barresi, Jennifer Schulz, Halil I. Corbali, Rieke Schleinhege, Peigen Huang, Pascal Bernatchez, Wilhelm Haas, Yves Boucher, Dai Fukumura, Rakesh K. Jain. Improving response of pancreatic cancer to losartan: Mechanistic insights and implications for personalized therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 1781.

Abstract Group 3 medulloblastomas (G3MB) carry the worst prognosis among medulloblastoma subtypes, yet molecularly targeted therapies remain elusive. Standard treatments cause severe long-term morbidity in survivors. Here, we identify tumor-derived sphingosine kinase 2 (SPHK2) as an essential driver of G3MB initiation and progression. SPHK2 exacerbates local immunosuppression by suppressing cytotoxic T-cell and NK-cell activity while promoting regulatory T-cell infiltration. Genetic or pharmacologic SPHK2 inhibition using Opaganib attenuates pro-survival tumor signaling and restores anti-tumor immunity, significantly improving survival in syngeneic G3MB mouse models. Combining Opaganib with fractionated low-dose radiation (f-LDRT) further enhances antigen presentation and reprograms tumor-associated myeloid cells toward an anti-tumor phenotype. This combination therapy markedly prolongs survival without inducing significant toxicity. Overall, our study establishes SPHK2 as a previously unrecognized therapeutic target and presents a safe, effective, microenvironment-reprogramming regimen for G3MB. One Sentence Summary Direct inhibition of tumor-derived SPHK2 overcomes local immunosuppression and downregulates pro-survival signaling in Group 3 medulloblastoma, while combination with fractionated low-dose radiation further enhances anti-tumor immunity and significantly improves survival.