CLDN6-specific CAR-T cells plus amplifying RNA vaccine in relapsed or refractory solid tumors: the phase 1 BNT211-01 trial

The oncofetal antigen Claudin 6 (CLDN6) is highly and specifically expressed in many solid tumors, and could be a promising treatment target. We report dose escalation results from the ongoing phase 1/2 BNT211-01 trial evaluating the safety and feasibility of chimeric antigen receptor (CAR) T cells targeting the CLDN6 with or without a CAR-T cell-amplifying RNA vaccine (CARVac) at two dose levels (DLs) in relapsed/refractory CLDN6-positive solid tumors. The primary endpoints were safety and tolerability, maximum tolerated dose and recommended phase 2 dose (RP2D). Secondary endpoints included objective response rate (ORR) and disease control rate. We observed manageable toxicity, with 10 out of 22 patients (46%) experiencing cytokine release syndrome including one grade 3 event and 1 out of 22 (5%) with grade 1 immune effector cell-associated neurotoxicity syndrome. Dose-limiting toxicities occurred in two patients at the higher DL, resolving without sequelae. CAR-T cell engraftment was robust, and the addition of CARVac was well tolerated. The unconfirmed ORR in 21 evaluable patients was 33% (7 of 21), including one complete response. The disease control rate was 67% (14 of 21), with stable disease in seven patients. Patients with germ cell tumors treated at the higher DL exhibited the highest response rate (ORR 57% (4 of 7)). The maximum tolerated dose and RP2D were not established as the trial has been amended to utilize an automated manufacturing process. A repeat of the dose escalation is ongoing and will identify a RP2D for pivotal trials. ClinicalTrials.gov Identifier: NCT04503278 .

EXTH-85. TARGETING CLAUDIN 6 WITH CAR T CELL THERAPY FOR ATYPICAL TERATOID/RHABDOID TUMOR

Atypical teratoid/rhabdoid tumor (ATRT) is an aggressive brain tumor that predominantly affects young children and has an average 5-year survival under 50%. Novel, targeted therapies are desperately needed. Claudin 6 (CLDN6) is a tight junction protein present during development and expressed in up to 70% of ATRT specimens but not in normal tissue, making it a promising immunotherapeutic target. CLDN6-targeted chimeric antigen receptor (CAR) T cells in combination with a CAR T cell–amplifying mRNA vaccine have demonstrated antitumor activity against other CLDN6-expressing cancers in pre-clinical and phase I adult trial (NCT04503278; Haanen J et al AACR, 2022). To assess the effectiveness of CLDN6-targeted CAR T cells against ATRT, we utilized a second-generation mRNA CAR with a 4-1BB costimulatory domain and single-chain variable fragment against CLDN6 (Reinhard et al, 2020). Patient-derived ATRT specimens were assessed by RNAseq for CLDN6 expression (mean FPKM= 11.4) and by immunohistochemistry (positive staining in 53% of specimens). Tumor-derived cell lines were validated for CLDN6 expression by flow cytometry. Co-culture of CLDN6-directed mRNA CAR T cells with ATRT cell line 7316-2187 resulted in tumor-specific cytotoxicity compared to CD19-directed control CAR T cells (92% versus 15% at 10:1, p< 0.0001; 86% versus 0% at 5:1, p< 0.0001). Similar results were seen with ATRT cell line 7316-2141 (75% versus 7% at 10:1, p< 0.0001; 53% versus 0% at 5:1, p< 0.0001). Both CLDN6- and CD19-directed CAR T cells showed no cytotoxicity against CLDN6-negative cell line 7316-4149. Patient-derived xenograft models were also created through intracranial injection of multiple ATRT patient cell lines, and ongoing work will evaluate locoregional administration of CLDN6-directed CAR T cells in orthotopic xenograft models to test in vivo efficacy. This work highlights the potential for targeting CLDN6 via CAR T cell therapy in patients with ATRT as a novel therapeutic strategy for these devastating tumors.

A TCR-like CAR Promotes Sensitive Antigen Recognition and Controlled T-cell Expansion Upon mRNA Vaccination

Chimeric antigen receptor (CAR) T cells are efficacious in patients with B-cell malignancies, while their activity is limited in patients with solid tumors. We developed a novel heterodimeric TCR-like CAR (TCAR) designed to achieve optimal chain pairing and integration into the T-cell CD3 signaling complex. The TCAR mediated high antigen sensitivity and potent antigen-specific T-cell effector functions in short-term in vitro assays. Both persistence and functionality of TCAR T cells were augmented by provision of costimulatory signals, which improved proliferation in vitro and in vivo. Combination with a nanoparticulate RNA vaccine, developed for in vivo expansion of CAR T cells, promoted tightly controlled expansion, survival, and antitumor efficacy of TCAR T cells in vivo.

Significance

A novel TCAR is tightly controlled by RNA vaccine-mediated costimulation and may provide an alternative to second-generation CARs for the treatment of solid tumors.

Abstract CT002: BNT211: A Phase I trial to evaluate safety and efficacy of CLDN6 CAR-T cells and CARVac-mediated in vivo expansion in patients with CLDN6-positive advanced solid tumors

Background: BNT211 comprises two drug products, a chimeric antigen receptor (CAR)-T cell product candidate that targets the tumor specific antigen claudin 6 (CLDN6) and a CAR-T cell-Amplifying RNA Vaccine (CARVac). In mice, CARVac mediates expansion of adoptively transferred CAR-T cells, improving their persistence and functionality. BNT211 aims to establish CAR-T cell therapy for CLDN6-positive solid tumors.

Methods: This first-in-human, open label, multi-center trial involves a bifurcated 3+3 design with CLDN6 CAR-T cell dose escalations for both monotherapy (Part 1) and combination with CARVac (Part 2) following lymphodepletion. In Part 2, CARVac is applied q2/3w up to 100 days post CAR-T cell transfer, including a one-step intra-patient dose escalation followed by q6w maintenance dosing. Patients with CLDN6-positive relapsed or refractory solid tumors without further standard treatment options and ECOG 0-1 are eligible for recruitment.

Results: As of 19th Jan 2022, 16 patients have been treated, with CAR-T cell transfer performed at dose levels (DLs) 1 and 2 for parts 1 and 2. In total, 37 ≥G3 AEs related to the drug product (mainly cytopenia, or transaminase and lipase elevations without clinical correlates) and 2 DLTs (G4 cytopenia at DL2, part 1 and G4 hemophagocytic lymphohistiocytosis at DL2, part 2) were reported (all resolved). Pronounced cytopenia occurred in patients with testicular cancer who had recently received high-dose chemotherapy and autologous stem cell transplantation. For these patients a lymphodepletion-free/reduced cohort was recently opened. Analysis of CAR-T cell frequency in peripheral blood revealed robust engraftment in all patients, with peak engraftment around day 17. Manageable cytokine release syndrome (G1-2) without any signs of neurotoxicity was observed in 8 patients. Administration of CARVac resulted in transient flu-like symptoms resolving within 24 h. Preliminary efficacy data of 12 evaluable patients 6 weeks after infusion showed 5 patients with PRs (with 39-49% shrinkage of target lesions), 6 with SD and 1 patient with PD (ORR 42%; DCR 92%), with responses seen in testicular and ovarian cancer patients. At 12 weeks, 5 of the 6 patients with PRs showed deepening of responses (50-73% shrinkage). In addition, one testicular cancer patient was treated with a 50% lymphodepletion regime and showed PR after 6 weeks.

Conclusions: CLDN6 CAR-T cells ± CARVac show an acceptable safety profile at doses tested and encouraging signs of clinical activity. Data from the completed dose escalation phase will be presented. Acknowledgements: BNT211-01 is funded by BioNTech Cell & Gene Therapies GmbH.

Trial registration: Clinicaltrials.gov: NCT04503278.

Ethics approval: Ethics & Institutional Review Board approvals were obtained from the respective participating countries prior to initiation of the trial.

Citation Format: John BAG Haanen, Andreas Mackensen, Christian Koenecke, Winfried Alsdorf, Eva Wagner-Drouet, Daniel Heudobler, Peter Borchmann, Carsten Bokemeyer, Sebastian Klobuch, Alexander Desuki, Florian Lüke, Erol Wiegert, Catrine Schulz, Benjamin Rengstl, Liane Preussner, Özlem Türeci, Ugur Sahin. BNT211: A Phase I trial to evaluate safety and efficacy of CLDN6 CAR-T cells and CARVac-mediated in vivo expansion in patients with CLDN6-positive advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT002.

Abstract LB-383: An RNA vaccine drives expansion and efficacy of claudin-CAR-T cells against solid tumors

Chimeric antigen receptor (CAR)-T cells have shown efficacy in patients with B cell malignancies. Yet, their application for solid tumors has challenges that include limited cancer-specific targets and nonpersistence of adoptively transferred CAR-T cells. Here, we introduce the developmentally regulated tight junction protein claudin 6 (CLDN6) as a CAR target in solid tumors and a strategy to overcome inefficient CAR-T cell stimulation in vivo. We demonstrate that a nanoparticulate RNA vaccine, designed for body-wide delivery of the CAR antigen into lymphoid compartments, stimulates adoptively transferred CAR-T cells. Presentation of the natively folded target on resident antigen-presenting cells promotes cognate and selective expansion of CAR-T cells. Improved engraftment of CAR-T cells and regression of large tumors in difficult-to-treat mouse models was achieved at subtherapeutic CAR-T cell doses.

Citation Format: Katharina Reinhard, Benjamin Rengstl, Petra Oehm, Özlem Türeci, Ugur Sahin. An RNA vaccine drives expansion and efficacy of claudin-CAR-T cells against solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-383.

An RNA vaccine drives expansion and efficacy of claudin-CAR-T cells against solid tumors

Chimeric antigen receptor (CAR)–T cells have shown efficacy in patients with B cell malignancies. Yet, their application for solid tumors has challenges that include limited cancer-specific targets and nonpersistence of adoptively transferred CAR-T cells. Here, we introduce the developmentally regulated tight junction protein claudin 6 (CLDN6) as a CAR target in solid tumors and a strategy to overcome inefficient CAR-T cell stimulation in vivo. We demonstrate that a nanoparticulate RNA vaccine, designed for body-wide delivery of the CAR antigen into lymphoid compartments, stimulates adoptively transferred CAR-T cells. Presentation of the natively folded target on resident antigen-presenting cells promotes cognate and selective expansion of CAR-T cells. Improved engraftment of CAR-T cells and regression of large tumors in difficult-to-treat mouse models was achieved at subtherapeutic CAR-T cell doses.

Ectopic expression of transcription factor BATF3 induces B-cell lymphomas in a murine B-cell transplantation model

The mechanisms involved in malignant transformation of mature B and T lymphocytes are still poorly understood. In a previous study, we compared gene expression profiles of the tumor cells of Hodgkin lymphoma (HL) and anaplastic large cell lymphoma (ALCL) to their normal cellular counterparts and found the basic leucine zipper protein ATF-like 3 (BATF3) to be significantly upregulated in the tumor cells of both entities. To assess the oncogenic potential of BATF3 in lymphomagenesis and to dissect the molecular interactions of BATF3 in lymphoma cells, we retrovirally transduced murine mature T and B cells with a BATF3-encoding viral vector and transplanted each population into Rag1-deficient recipients. Intriguingly, BATF3-expressing B lymphocytes readily induced B-cell lymphomas after characteristic latencies, whereas T-cell transplanted animals remained healthy throughout the observation time. Further analyses revealed a germinal center B-cell-like phenotype of most BATF3-initiated lymphomas. In a multiple myeloma cell line, BATF3 inhibited BLIMP1 expression, potentially illuminating an oncogenic action of BATF3 in B-cell lymphomagenesis. In conclusion, BATF3 overexpression induces malignant transformation of mature B cells and might serve as a potential target in B-cell lymphoma treatment.

A strong host response and lack of MYC expression are characteristic for diffuse large B cell lymphoma transformed from nodular lymphocyte predominant Hodgkin lymphoma

Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) is an indolent lymphoma, but can transform into diffuse large B cell lymphoma (DLBCL), showing a more aggressive clinical behavior. Little is known about these cases on the molecular level. Therefore, the aim of the present study was to characterize DLBCL transformed from NLPHL (LP-DLBCL) by gene expression profiling (GEP). GEP revealed an inflammatory signature pinpointing to a specific host response. In a coculture model resembling this host response, DEV tumor cells showed an impaired growth behavior. Mechanisms involved in the reduced tumor cell proliferation included a downregulation of MYC and its target genes. Lack of MYC expression was also confirmed in 12/16 LP-DLBCL by immunohistochemistry. Furthermore, CD274/PD-L1 was upregulated in DEV tumor cells after coculture with T cells or monocytes and its expression was validated in 12/19 cases of LP-DLBCL. Thereby, our data provide new insights into the pathogenesis of LP-DLBCL and an explanation for the relatively low tumor cell content. Moreover, the findings suggest that treatment of these patients with immune checkpoint inhibitors may enhance an already ongoing host response in these patients.

CD30-targeted oncolytic viruses as novel therapeutic approach against classical Hodgkin lymphoma

Classical Hodgkin lymphoma (cHL) is a hematopoietic malignancy with a characteristic cellular composition. The tumor mass is made up of infiltrated lymphocytes and other cells of hematologic origin but only very few neoplastic cells that are mainly identified by the diagnostic marker CD30. While most patients with early stage cHL can be cured by standard therapy, treatment options for relapsed or refractory cHL are still not sufficient, although immunotherapy-based approaches for the treatment of cHL patients have gained ground in the last decade. Here, we suggest a novel therapeutic concept based on oncolytic viruses selectively destroying the CD30⁺-positive cHL tumor cells. Relying on a recently described CD30-specific scFv we have generated CD30-targeted measles virus (MV-CD30) and vesicular stomatitis virus (VSV-CD30). For VSV-CD30 the VSV glycoprotein G reading frame was replaced by those of the CD30-targeted MV glycoproteins. Both viruses were found to be highly selective for CD30-positive cells as demonstrated by infection of co-cultures of target and non-target cells as well as through blocking infection by soluble CD30. Notably, VSV-CD30 yielded much higher titers than MV-CD30 and resulted in a more rapid and efficient killing of cultivated cHL-derived cell lines. Mouse tumor models revealed that intratumorally, as well as systemically injected VSV-CD30, infected cHL xenografts and significantly slowed down tumor growth resulting in a substantially prolonged survival of tumor-bearing mice. Taken together, the data support further preclinical testing of VSV-CD30 as novel therapeutic agent for the treatment of cHL and other CD30⁺-positive malignancies.

Concepts in mature T-cell lymphomas - highlights from an international joint symposium on T-cell immunology and oncology<sup/>

Growing attention in mature T-cell lymphomas/leukemias (MTCL) is committed to more accurate and meaningful classifications, improved pathogenetic concepts and expanded therapeutic options. This requires considerations of the immunologic concepts of T-cell homeostasis and the specifics of T-cell receptor (TCR) affinities and signaling. Scientists from various disciplines established the CONTROL-T research unit and in an international conference on MTCL they brought together experts from T-cell immunity, oncology, immunotherapy and systems biology. We report here meeting highlights on the covered topics of diagnostic pitfalls, implications by the new WHO classification, insights from discovered genomic lesions as well as TCR-centric concepts of cellular dynamics in host defense, auto-immunity and tumorigenic clonal escape, including predictions to be derived from in vivo imaging and mathematical modeling. Presentations on novel treatment approaches were supplemented by strategies of optimizing T-cell immunotherapies. Work packages, that in joint efforts would advance the field of MTCL more efficiently, are identified.

Tumor-infiltrating HLA-matched CD4(+) T cells retargeted against Hodgkin and Reed-Sternberg cells

Hodgkin lymphoma (HL) presents with a unique histologic pattern. Pathognomonic Hodgkin and Reed-Sternberg (HRS) cells usually account for less than 1% of the tumor and are embedded in a reactive infiltrate mainly comprised of CD4(+) T cells. HRS cells induce an immunosuppressive microenvironment and thereby escape antitumor immunity. To investigate the impact of interactions between HRS cells and T cells, we performed long-term co-culture studies that were further translated into a xenograft model. Surprisingly, we revealed a strong antitumor potential of allogeneic CD4(+) T cells against HL cell lines. HRS and CD4(+) T cells interact by adhesion complexes similar to immunological synapses. Tumor-cell killing was likely based on the recognition of allogeneic major histocompatibility complex class II (MHC-II) receptor, while CD4(+) T cells from MHC-II compatible donors did not develop any antitumor potential in case of HL cell line L428. However, gene expression profiling (GEP) of co-cultured HRS cells as well as tumor infiltration of matched CD4(+) T cells indicated cellular interactions. Moreover, matched CD4(+) T cells could be activated to kill CD30(+) HRS cells when redirected with a CD30-specific chimeric antigen receptor. Our work gives novel insights into the crosstalk between HRS and CD4(+) T cells, suggesting the latter as potent effector cells in the adoptive cell therapy of HL.

On the origin of giant cells in Hodgkin lymphoma

Multinucleated giant tumor cells are frequently observed in tissue sections of lymphoma patients. In Hodgkin lymphoma (HL), these cells are pathognomonic for the disease and named Reed-Sternberg (RS) cells. Despite the well-described disease-promoting functions of RS cells, their development has remained obscure. We addressed this open question by continuous live cell imaging to observe the generation of RS cells. Single-cell tracking of HL cell lines revealed that RS cells develop from mononucleated progenitors that divide and subsequently re-fuse, before they grow and become multinucleated giant cells. Thus, RS cell generation is neither due to cell fusion of unrelated Hodgkin cells nor to endomitosis, as previously suggested. In the majority of cases, re-fusion of daughter cells was preceded by an incomplete cytokinesis, visualized by a persistent microtubule bridge connecting the cells. This surprising finding describes a novel mechanism for the formation of multinuclear giant cells with potential relevance beyond HL.

Expression and functional relevance of cannabinoid receptor 1 in Hodgkin lymphoma

Background

Cannabinoid receptor 1 (CB₁) is expressed in certain types of malignancies. An analysis of CB₁ expression and function in Hodgkin lymphoma (HL), one of the most frequent lymphomas, was not performed to date.

Design and Methods

We examined the distribution of CB₁ protein in primary cases of HL. Using lymphoma derived cell lines, the role of CB₁ signaling on cell survival was investigated.

Results

A predominant expression of CB₁ was found in Hodgkin-Reed-Sternberg cells in a vast majority of classical HL cases. The HL cell lines L428, L540 and KM-H2 showed strong CB₁-abundance and displayed a dose-dependent decline of viability under CB₁ inhibition with AM251. Further, application of AM251 led to decrease of constitutively active NFκB/p65, a crucial survival factor of HRS-cells, and was followed by elevation of apoptotic markers in HL cells.

Conclusions

The present study identifies CB₁ as a feature of HL, which might serve as a potential selective target in the treatment of Hodgkin lymphoma.

Mature T-cell lymphomagenesis induced by retroviral insertional activation of Janus kinase 1

Retroviral vectors (RVs) are powerful tools in clinical gene therapy. However, stable genomic integration of RVs can be oncogenic, as reported in several animal models and in clinical trials. Previously, we observed that T-cell receptor (TCR) polyclonal mature T cells are resistant to transformation after gammaretroviral transfer of (proto-)oncogenes, whereas TCR-oligoclonal T cells were transformable in the same setting. Here, we describe the induction of a mature T-cell lymphoma (MTCL) in TCR-oligoclonal OT-I transgenic T cells, transduced with an enhanced green fluorescent protein (EGFP)-encoding gammaretroviral vector. The tumor cells were of a mature T-cell phenotype and serially transplantable. Integration site analysis revealed a proviral hit in Janus kinase 1 (Jak1), which resulted in Jak1 overexpression and Jak/STAT-pathway activation, particularly via signal transducer and activator of transcription 3 (STAT3). Specific inhibition of Jak1 markedly delayed tumor growth. A systematic meta-analysis of available gene expression data on human mature T-cell lymphomas/leukemias confirmed the relevance of Jak/STAT overexpression in sporadic human T-cell tumorigenesis. To our knowledge, this is the first study to describe RV-associated insertional mutagenesis in mature T cells.

T-cell receptor diversity prevents T-cell lymphoma development

Mature T-cell lymphomas (MTCLs) have an extremely poor prognosis and are much less frequent than immature T-cell leukemias. This suggests that malignant outgrowth of mature T lymphocytes is well controlled. Indeed, in a previous study we found that mature T cells are resistant to transformation with known T-cell oncogenes. Here, however, we observed that T-cell receptor (TCR) mono-/oligoclonal mature T cells from TCR transgenic (tg) mice (OT-I, P14) expressing the oncogenes NPM/ALK or ΔTrkA readily developed MTCLs in T-cell-deficient recipients. Analysis of cell surface markers largely ruled out that TCR tg lymphomas were derived from T-cell precursors. Furthermore, cotransplanted non-modified TCR polyclonal T cells suppressed malignant outgrowth of oncogene expressing TCR tg T lymphocytes. A dominant role of an anti-leukemic immune response or Tregs in the control of MTCLs seems unlikely as naïve T cells derived from oncogene expressing stem cells, which should be tolerant to leukemic antigens, as well as purified CD4 and CD8 were resistant to transformation. However, our results are in line with a model in which homeostatic mechanisms that stabilize the diversity of the normal T-cell repertoire, for example, clonal competition, also control the outgrowth of potentially malignant T-cell clones. This study introduces a new innate mechanism of lymphoma control.

Multiple restrictions of human immunodeficiency virus type 1 in feline cells

The productive replication of human immunodeficiency virus type 1 (HIV-1) occurs exclusively in defined cells of human or chimpanzee origin, explaining why heterologous animal models for HIV replication, pathogenesis, vaccination, and therapy are not available. This lack of an animal model for HIV-1 studies prompted us to examine the susceptibility of feline cells in order to evaluate the cat (Felis catus) as an animal model for studying HIV-1. Here, we report that feline cell lines harbor multiple restrictions with respect to HIV-1 replication. The feline CD4 receptor does not permit virus infection. Feline T-cell lines MYA-1 and FeT-1C showed postentry restrictions resulting in low HIV-1 luciferase reporter activity and low expression of viral Gag-Pol proteins when pseudotyped vectors were used. Feline fibroblastic CrFK and KE-R cells, expressing human CD4 and CCR5, were very permissive for viral entry and HIV-long terminal repeat-driven expression but failed to support spreading infection. KE-R cells displayed a profound block with respect to release of HIV-1 particles. In contrast, CrFK cells allowed very efficient particle production; however, the CrFK cell-derived HIV-1 particles had low specific infectivity. We subsequently identified feline apolipoprotein B-editing catalytic polypeptide 3 (feAPOBEC3) proteins as active inhibitors of HIV-1 particle infectivity. CrFK cells express at least three different APOBEC3s: APOBEC3C, APOBEC3H, and APOBEC3CH. While the feAPOBEC3C did not significantly inhibit HIV-1, the feAPOBEC3H and feAPOBEC3CH induced G to A hypermutations of the viral cDNA and reduced the infectivity approximately 10- to approximately 40-fold.