Thermosensitive liposomal irinotecan combined with regional hyperthermia and immune checkpoint inhibition in pancreatic ductal adenocarcinoma – a preclinical and translational study
Regional hyperthermia (RHT), the controlled heating of the tumor region to 42-43 °C in combination with chemotherapy or radiotherapy, is a clinically validated treatment modality. In the randomized phase III trial EORTC 62961-ESHO 95, initiated by our group, the addition of RHT to neoadjuvant chemotherapy in localized high-risk soft tissue sarcoma improved local progression-free survival as well as overall survival, with an absolute increase in the 10-year survival rate from 42.7 % to 52.6 % [1]. RHT acts on several levels: it is directly cytotoxic through temperature-dependent induction of apoptosis and necrosis, improves tumor perfusion and vascular permeability and thereby intratumoral drug availability, sensitizes tumors to chemotherapy and radiotherapy, functionally inhibits DNA repair (in particular homologous recombination), and exerts immunomodulatory effects including increased antigen presentation and enhanced T cell infiltration into the tumor microenvironment (TME) [2].
Pancreatic ductal adenocarcinoma (PDAC) is a particularly attractive indication for this approach. PDAC is characterized by a dense desmoplastic stroma, poor intratumoral drug penetration and an immunosuppressive, frequently immune-excluded microenvironment. The consequences are limited chemotherapy efficacy, restricted immune cell infiltration and, so far, disappointing results for immune checkpoint inhibitors (ICI) [3]. Precisely this combination of physical and immunological resistance makes PDAC a highly relevant model for an RHT-based treatment strategy; ongoing clinical trials at our site underline this rationale.
Thermosensitive liposomes (TSL) address the drug delivery barrier mechanistically by enabling selective, temperature-triggered drug release confined to the heated tumor region, with consecutive drug accumulation inside the tumor [4]. Our group has developed phosphatidyldiglycerol (DPPG₂)-based TSL and has translated TSL-doxorubicin from preclinical work into a first-in-human phase I trial at our center (NCT05858710), in which the combination with RHT was well tolerated and temperature-dependent drug release was demonstrated directly in patients [5]. With TSL-irinotecan, a second promising candidate is available: in vivo, TSL-irinotecan plus RHT resulted in up to 36-fold higher intratumoral irinotecan concentrations compared with conventional formulations including liposomal irinotecan (Onivyde®), together with significantly improved antitumor efficacy [6]. In our own recent preliminary work, TSL-irinotecan plus radiofrequency-based RHT has been successfully implemented in a syngeneic C57BL/6 PDAC model and showed first evidence of improved tumor control and histopathological correlates of an enhanced tumor response.
The current two-component approach nevertheless has an important limitation: while local tumor control is effective, systemic antitumor effects outside the heated area remain limited. This is particularly relevant for PDAC, which must be regarded as a systemic disease with early micrometastatic dissemination. At the same time, RHT provides a rational basis for combination with immuno-oncological strategies, since hyperthermia can induce an immunologically “hotter” TME and increase sensitivity to ICI [7, 8]. This leads to a mechanistically well-founded but so far not systematically investigated three-pillar therapeutic platform: RHT-triggered, locally active chemotherapy by TSL-irinotecan, combined with targeted systemic amplification by ICI.
(1) TSL-irinotecan combined with RHT leads to increased intratumoral drug release and accumulation in a syngeneic PDAC mouse model and thereby to improved tumor control compared with control treatments.
(2) The addition of ICI enhances the antitumor efficacy of TSL-irinotecan plus RHT and improves systemic tumor control, including non-heated tumor manifestations (abscopal effect).
(3) Response and resistance are associated with reproducible translational changes and correlate with (i) intratumoral irinotecan and SN-38 concentrations, (ii) histopathological response patterns such as necrosis and apoptosis, and (iii) defined changes of the TME.
The project is organized in five work packages (WP), all carried out under the direct supervision of experienced group members. All experimental prerequisites are fully established: valid animal licences (until 2031), standardised SOPs for tumor implantation, monitoring, RHT delivery and sampling, validated score sheets, defined inclusion criteria and humane endpoints. The candidate can therefore start experimental work without delay.
WP 1 – Training and model consolidation. Structured introduction to animal handling, cell culture, tumour implantation and radiofrequency-based RHT, to the principles of TSL drug delivery systems, and to the syngeneic KPC1050 PDAC model in C57BL/6 mice. Acquisition of the mandatory European animal experimentation certification (FELASA B or equivalent).
WP 2 – Therapeutic core study. Controlled efficacy study with defined treatment arms: control + RHT; ICI monotherapy + RHT; free irinotecan + RHT ± ICI; TSL-irinotecan + RHT ± ICI. TSL-irinotecan and free irinotecan are administered intravenously via the tail vein, ICI (anti-PD-1, clone RMP1-14) intraperitoneally, with RHT applied in parallel to systemic treatment. Primary endpoint is tumor growth under therapy; secondary endpoints are time to progression, overall survival and tolerability assessed by standardized score sheets.
WP 3 – Local versus systemic (abscopal) efficacy. A bilateral subcutaneous tumor model, in which only one tumor is heated, is used to dissect the local effect of RHT-triggered drug release from the systemic, immune-mediated effect of the combination with ICI, including analysis of the non-heated contralateral tumor.
WP 4 – Translational deep profiling. Systematic sampling (tumor, plasma, liver, kidney) at early time points for PK/PD analysis and at terminal time points. Quantification of irinotecan and its active metabolite SN-38 by LC-MS/MS in cooperation with the Department of Clinical Chemistry, Heidelberg University Hospital; histopathological quantification of necrosis and apoptosis and immunohistochemical characterization of the TME (CD8⁺ T cells, FOXP3⁺ regulatory T cells, myeloid populations, PD-L1) in cooperation with the Institute of Pathology, Technical University of Munich; complementary immune phenotyping by multiparameter flow cytometry.
WP 5 – Data integration, biomarkers and translation. Integrative analysis linking treatment, drug exposure and biological response: correlation of tumor response with intratumoral drug concentration, linkage of histopathological patterns with immunological changes, and identification of resistance markers (e.g. absent CD8⁺ T cell infiltration despite high drug exposure). The aim is to derive translationally relevant biomarkers and an optimized dose and scheduling concept as the basis for a subsequent clinical trial.
Cell culture (murine and human tumor cell lines, S2 level), syngeneic subcutaneous and bilateral tumor models, radiofrequency-based small-animal regional hyperthermia, intravenous and intraperitoneal drug administration, tumor growth and toxicity monitoring, characterization of liposomal formulations, tissue and plasma sampling and processing, histology and immunohistochemistry, multiparameter flow cytometry, LC-MS/MS-based pharmacokinetic and pharmacodynamic analysis, biostatistics and scientific writing.
The work is performed entirely in the laboratories of the research group at Campus Grosshadern, where a fully equipped bench is reserved for the doctoral candidate for the whole project period. The infrastructure comprises S2 cell culture facilities, approved animal facilities for murine models, an established radiofrequency-based small-animal hyperthermia platform and laboratories for tissue, blood and organ analysis. Day-to-day experimental guidance is provided by a postdoctoral researcher and an experienced scientist; two Clinician Scientists accompany the in vivo work and the translational analyses; technical support is provided by an experienced technician. The supervisor accompanies the project closely through weekly meetings, journal clubs and structured progress reports, and active participation in international conferences and research retreats is strongly encouraged. Consumables, animal costs and analytical costs are covered by ongoing third-party funding and institutional funds.
The project is a consistent extension of an already successfully established preclinical and translational platform with proven clinical translation. It is expected to result in at least two first-author publications in international peer-reviewed journals, presentations at international conferences (e.g. ESHO, CTOS, AACR), and a comprehensive preclinical data package supporting a subsequent early-phase clinical trial of TSL-irinotecan plus RHT ± ICI in pancreatic cancer.
[1] Issels RD, Lindner LH, Verweij J, et al. JAMA Oncol. 2018;4(4):483–492.
[2] Issels R, Kampmann E, Kanaar R, Lindner LH. Int J Hyperthermia. 2016;32(1):89–95.
[3] Yu S, Zhang C, Xie KP. Biochim Biophys Acta Rev Cancer. 2021;1875(1):188461.
[4] Kneidl B, Peller M, Winter G, Lindner LH, Hossann M. Int J Nanomedicine. 2014;9:4387–4398.
[5] Di Gioia D, Reichardt P, Güler SE, … Berclaz LM, … Lindner LH. Manuscript in preparation.
[6] Wedmann B, Kort S, Pointner L, Winter G, Lindner LH, Hossann M. Int J Pharm. 2025;681:125862.
[7] Liu P, Ye M, Wu Y, et al. Cancer Med. 2023;12(3):3201–3221.
[8] Berclaz LM, Burkhard-Meier A, Lechner A, et al. Cancer Immunol Immunother. 2025;74(6):174.
| Timeline: | Progress: |
|---|---|
| Years 1-2 (months 1-24) | induction and training (WP 1); animal experimentation certification; establishment of the PDAC model and the RHT protocol by the candidate; pilot experiments and finalization of the experimental design; start of the doctoral program curriculum. Therapeutic core study with all treatment arms (WP 2); continuous tumor and tolerability monitoring; systematic sampling; start of PK/PD and histopathological analyses (WP 4); first conference abstract. |
| Year 3 (months 25-36) | bilateral tumor model addressing local versus systemic efficacy (WP 3); completion of translational profiling including immunohistochemistry, flow cytometry and LC-MS/MS (WP 4); research stays with the cooperation partners in Munich and Heidelberg; first manuscript. |
| Year 4 (months 37-48) | integrative data analysis and biomarker identification (WP 5); confirmatory experiments; second manuscript; writing and defence of the doctoral thesis. |