Optimizing the design and geometry of T cell engaging bispecific antibodies targeting CEA in colorectal cancer

Metastatic colorectal cancer (mCRC) remains a leading cause of cancer-related deaths, with a 5-year survival rate of only 15%. T cell engaging bispecific antibodies (TCBs) represent a class of biopharmaceuticals that redirect cytotoxic T cells towards tumor cells, thereby turning immunologically "cold" tumors "hot." The carcinoembryonic antigen (CEA) is an attractive tumor-associated antigen (TAA) that is overexpressed in over 98% of CRC patients. In this study, we report the comparison of four different TCB formats employing the antibodies F4 (targeting human CEA) and 2C11 (targeting mouse CD3ε). These formats include both antibody fragment- and IgG-based constructs, with either one or two binding specificities of the respective antibodies. The 2+1 arrangement, using an anti-CEA single-chain diabody (scDbCEA) fused to an anti-CD3 single-chain variable fragment (scFvCD3), emerged as the most potent design, showing tumor killing at subnanomolar concentrations across three different CEA+ cell lines. The in vitro activity was three times greater in C57BL/6 mouse colon adenocarcinoma cells (MC38) expressing high levels of CEA compared to those expressing low levels, highlighting the impact of CEA antigen density in this assay. The optimal TCB candidate was tested in two different immunocompetent mouse models of colorectal cancer and showed tumor growth retardation. Ex vivo analysis of tumor infiltrates showed an increase in CD4+ and CD8+ T cells upon TCB treatment. This study suggests that bivalent tumor targeting, monovalent T cell targeting, and a short spatial separation are promising characteristics for CEA targeting TCBs.

Targeted interleukin-2 enhances the in vivo anti-cancer activity of Pluvicto™

PURPOSE

Pluvicto™ ([177Lu]Lu-PSMA-617), a radioligand therapeutic targeting prostate-specific membrane antigen (PSMA), has been recently approved for the treatment of metastatic castration-resistant prostate cancer (mCRPR). The drug suffers from salivary gland and kidney uptake that prevents its dose escalation to potentially curative doses. In this work, we sought to potentiate the in vivo anti-cancer activity of Pluvicto™ by combining it with L19-IL2, a clinical-stage investigational medicinal product based on tumor-targeted interleukin-2.

METHODS

We established a new PSMA-expressing model (HT-1080.hPSMA) and validated it using a fluoresceine analogue of PSMA-617 (compound 1). The HT-1080.hPSMA model was used to study the saturation and tumor retention of Pluvicto™ (compound 2) and to run combination therapy studies with L19-IL2. To complement our understanding of the mechanism of action of this novel combination, we conducted proteomics experiments on tumor samples after therapy with Pluvicto™ alone or in combination with the immunocytokine.

RESULTS

High, selective, and long-lived tumor uptake was observed for Pluvicto™ (2) in the novel HT-1080.hPSMA model. Therapy studies in HT-1080.hPSMA tumor-bearing mice revealed that the combination of Pluvicto™ (2) plus L19-IL2 mediated curative and durable responses in all animals. Potent in vivo anti-cancer activity was observed solely for the combination modality, at doses that were well tolerated by treated animals. Proteomics studies indicated that L19-IL2 boosts the activation of the immune system in animals pre-treated with Pluvicto™.

CONCLUSION

The therapeutic efficacy of Pluvicto™ at low radioactive doses can be effectively enhanced by the combination with L19-IL2. Our findings warrant further clinical exploration of this novel combination modality.

A novel strategy to generate immunocytokines with activity-on-demand using small molecule inhibitors

Cytokine-based therapeutics have been shown to mediate objective responses in certain tumor entities but suffer from insufficient selectivity, causing limiting toxicity which prevents dose escalation to therapeutically active regimens. The antibody-based delivery of cytokines significantly increases the therapeutic index of the corresponding payload but still suffers from side effects associated with peak concentrations of the product in blood upon intravenous administration. Here we devise a general strategy (named "Intra-Cork") to mask systemic cytokine activity without impacting anti-cancer efficacy. Our technology features the use of antibody-cytokine fusions, capable of selective localization at the neoplastic site, in combination with pathway-selective inhibitors of the cytokine signaling, which rapidly clear from the body. This strategy, exemplified with a tumor-targeted IL12 in combination with a JAK2 inhibitor, allowed to abrogate cytokine-driven toxicity without affecting therapeutic activity in a preclinical model of cancer. This approach is readily applicable in clinical practice.

In vivo activation of FAP-cleavable small molecule-drug conjugates for the targeted delivery of camptothecins and tubulin poisons to the tumor microenvironment

Small molecule-drug conjugates (SMDCs) are increasingly considered as a therapeutic alternative to antibody-drug conjugates (ADCs) for cancer therapy. OncoFAP is an ultra-high affinity ligand of Fibroblast Activation Protein (FAP), a stromal tumor-associated antigen overexpressed in a wide variety of solid human malignancies. We have recently reported the development of non-internalizing OncoFAP-based SMDCs, which are activated by FAP thanks to selective proteolytic cleavage of the -GlyPro- linker with consequent release of monomethyl auristatin E (MMAE) in the tumor microenvironment. In this article, we describe the generation and the in vivo characterization of FAP-cleavable OncoFAP-drug conjugates based on potent topoisomerase I inhibitors (DXd, SN-38, and exatecan) and an anti-tubulin payload (MMAE), which are already exploited in clinical-stage and approved ADCs. The Glycine-Proline FAP-cleavable technology was directly benchmarked against linkers found in Adcetris™, Enhertu™, and Trodelvy™ structures by means of in vivo therapeutic experiments in mice bearing tumors with cellular or stromal FAP expression. OncoFAP-GlyPro-Exatecan and OncoFAP-GlyPro-MMAE emerged as the most efficacious anti-cancer therapeutics against FAP-positive cellular models. OncoFAP-GlyPro-MMAE exhibited a potent antitumor activity also against stromal models, and was therefore selected for clinical development.

Expression of Inflammatory Genes in Murine Lungs in a Model of Experimental Pulmonary Hypertension: Effects of an Antibody-Based Targeted Delivery of Interleukin-9

BACKGROUND

Pathogenesis of pulmonary hypertension (PH) is a multifactorial process driven by inflammation and pulmonary vascular remodeling. To target these two aspects of PH, we recently tested a novel treatment: Interleukin-9 (IL9) fused to F8, an antibody that binds to the extra-domain A of fibronectin (EDA+ Fn). As EDA+ Fn is not found in healthy adult tissue but is expressed during PH, IL9 is delivered specifically to the tissue affected by PH. We found that F8IL9 reduced pulmonary vascular remodeling and attenuated PH compared with sham-treated mice.

PURPOSE

To evaluate possible F8IL9 effects on PH-associated inflammatory processes, we analysed the expression of genes involved in pulmonary immune responses.

METHODS

We applied the monocrotaline (MCT) model of PH in mice (n = 44). Animals were divided into five experimental groups: sham-induced animals without PH (control, n = 4), MCT-induced PH without treatment (PH, n = 8), dual endothelin receptor antagonist treatment (dual ERA, n = 8), F8IL9 treatment (n = 12, 2 formats with n = 6 each), or with KSFIL9 treatment (KSFIL9, n = 12, 2 formats with n = 6 each, KSF: control antibody with irrelevant antigen specificity). After 28 days, a RT-PCR gene expression analysis of inflammatory response (84 genes) was performed in the lung.

RESULTS

Compared with the controls, 19 genes exhibited relevant (+2.5-fold) upregulation in the PH group without treatment. Gene expression levels in F8IL9-treated lung tissue were reduced compared to the PH group without treatment. This was the case especially for CCL20, CXCL5, C-reactive protein, pentraxin related (CRPPR), and Kininogen-1 (KNG1).

CONCLUSION

In accordance with the hypothesis stated above, F8IL9 treatment diminished the upregulation of some genes associated with inflammation in a PH animal model. Therefore, we hypothesize that IL9-based immunocytokine treatment will likely modulate various inflammatory pathways.

Ex vivo mass spectrometry-based biodistribution analysis of an antibody-Resiquimod conjugate bearing a protease-cleavable and acid-labile linker

Immune-stimulating antibody conjugates (ISACs) equipped with imidazoquinoline (IMD) payloads can stimulate endogenous immune cells to kill cancer cells, ultimately inducing long-lasting anticancer effects. A novel ISAC was designed, featuring the IMD Resiquimod (R848), a tumor-targeting antibody specific for Carbonic Anhydrase IX (CAIX) and the protease-cleavable Val-Cit-PABC linker. In vitro stability analysis showed not only R848 release in the presence of the protease Cathepsin B but also under acidic conditions. The ex vivo mass spectrometry-based biodistribution data confirmed the low stability of the linker-drug connection while highlighting the selective accumulation of the IgG in tumors and its long circulatory half-life.

Tumor-Targeted Interleukin 2 Boosts the Anticancer Activity of FAP-Directed Radioligand Therapeutics

We studied the antitumor efficacy of a combination of 177Lu-labeled radioligand therapeutics targeting the fibroblast activation protein (FAP) (OncoFAP and BiOncoFAP) with the antibody-cytokine fusion protein L19-interleukin 2 (L19-IL2) providing targeted delivery of interleukin 2 to tumors. Methods: The biodistribution of 177Lu-OncoFAP and 177Lu-BiOncoFAP at different molar amounts (3 vs. 250 nmol/kg) of injected ligand was studied via SPECT/CT in mice bearing subcutaneous HT-1080.hFAP tumors, and self-absorbed tumor and organ doses were calculated. The in vivo anticancer effect of 5 MBq of the radiolabeled preparations was evaluated as monotherapy or in combination with L19-IL2 in subcutaneously implanted HT-1080.hFAP and SK-RC-52.hFAP tumors. Tumor samples from animals treated with 177Lu-BiOncoFAP, L19-IL2, or both were analyzed by mass spectrometry-based proteomics to identify therapeutic signatures on cellular and stromal markers of cancer and on immunomodulatory targets. Results: 177Lu-BiOncoFAP led to a significantly higher self-absorbed dose in FAP-positive tumors (0.293 ± 0.123 Gy/MBq) than did 177Lu-OncoFAP (0.157 ± 0.047 Gy/MBq, P = 0.01) and demonstrated favorable tumor-to-organ ratios at high molar amounts of injected ligand. Administration of L19-IL2 or 177Lu-BiOncoFAP as single agents led to cancer cures in only a limited number of treated animals. In 177Lu-BiOncoFAP-plus-L19-IL2 combination therapy, complete remissions were observed in all injected mice (7/7 complete remissions for the HT-1080.hFAP model, and 4/4 complete remissions for the SK-RC-52.hFAP model), suggesting therapeutic synergy. Proteomic studies revealed a mechanism of action based on the activation of natural killer cells, with a significant enhancement of the expression of granzymes and perforin 1 in the tumor microenvironment after combination treatment. Conclusion: The combination of OncoFAP-based radioligand therapeutics with concurrent targeting of interleukin 2 shows synergistic anticancer effects in the treatment of FAP-positive tumors. This experimental finding should be corroborated by future clinical studies.

Impact of library input on the hit discovery rate in DNA-encoded chemical library selections

DNA-encoded chemical libraries (DELs) are powerful drug discovery tools, enabling the parallel screening of millions of DNA-barcoded compounds. We investigated how the DEL input affects the hit discovery rate in DEL screenings. Evaluation of selection fingerprints revealed that the use of approximately 105 copies of each library member is required for the confident identification of nanomolar hits, using generally applicable methodologies.

Control of the antitumour activity and specificity of CAR T cells via organic adapters covalently tethering the CAR to tumour cells

On-target off-tumour toxicity limits the anticancer applicability of chimaeric antigen receptor (CAR) T cells. Here we show that the tumour-targeting specificity and activity of T cells with a CAR consisting of an antibody with a lysine residue that catalytically forms a reversible covalent bond with a 1,3-diketone hapten can be regulated by the concentration of a small-molecule adapter. This adapter selectively binds to the hapten and to a chosen tumour antigen via a small-molecule binder identified via a DNA-encoded library. The adapter therefore controls the formation of a covalent bond between the catalytic antibody and the hapten, as well as the tethering of the CAR T cells to the tumour cells, and hence the cytotoxicity and specificity of the cytotoxic T cells, as we show in vitro and in mice with prostate cancer xenografts. Such small-molecule switches of T-cell cytotoxicity and specificity via an antigen-independent 'universal' CAR may enhance the control and safety profile of CAR-based cellular immunotherapies.

A DNA-encoded chemical library based on chiral 4-amino-proline enables stereospecific isozyme-selective protein recognition

DNA-encoded chemical libraries (DELs) consist of large chemical compound collections individually linked to DNA barcodes, facilitating pooled construction and screening. However, screening campaigns often fail if the molecular arrangement of the building blocks is not conducive to an efficient interaction with a protein target. Here we postulated that the use of rigid, compact and stereo-defined central scaffolds for DEL synthesis may facilitate the discovery of very specific ligands capable of discriminating between closely related protein targets. We synthesized a DEL comprising 3,735,936 members, featuring the four stereoisomers of 4-aminopyrrolidine-2-carboxylic acid as central scaffolds. The library was screened in comparative selections against pharmaceutically relevant targets and their closely related protein isoforms. Hit validation results revealed a strong impact of stereochemistry, with large affinity differences between stereoisomers. We identified potent isozyme-selective ligands against multiple protein targets. Some of these hits, specific to tumour-associated antigens, demonstrated tumour-selective targeting in vitro and in vivo. Collectively, constructing DELs with stereo-defined elements contributed to high library productivity and ligand selectivity.

Adapting Neutralizing Antibodies to Viral Variants by Structure-Guided Affinity Maturation Using Phage Display Technology

Neutralizing monoclonal antibodies have achieved great efficacy and safety for the treatment of numerous infectious diseases. However, their neutralization potency is often rapidly lost when the target antigen mutates. Instead of isolating new antibodies each time a pathogen variant arises, it can be attractive to adapt existing antibodies, making them active against the new variant. Potential benefits of this approach include reduced development time, cost, and regulatory burden. Here a methodology is described to rapidly evolve neutralizing antibodies of proven activity, improving their function against new pathogen variants without losing efficacy against previous ones. The reported procedure is based on structure-guided affinity maturation using combinatorial mutagenesis and phage display technology. Its use against the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is demonstrated, but it is suitable for any other pathogen. As proof of concept, the method is applied to CoV-X2, a human bispecific antibody that binds with high affinity to the early SARS-CoV-2 variants but lost neutralization potency against Delta. Antibodies emerging from the affinity maturation selection exhibit significantly improved neutralization potency against Delta and no loss of efficacy against the other viral sequences tested. These results illustrate the potential application of structure-guided affinity maturation in facilitating the rapid adaptation of neutralizing antibodies to pathogen variants.

Erratum: Anti-CD117 CAR T cells incorporating a safety switch eradicate human acute myeloid leukemia and hematopoietic stem cells

[This corrects the article DOI: 10.1016/j.omto.2023.07.003.].

Anti-CD117 CAR T cells incorporating a safety switch eradicate human acute myeloid leukemia and hematopoietic stem cells

Discrimination between hematopoietic stem cells and leukemic stem cells remains a major challenge for acute myeloid leukemia immunotherapy. CAR T cells specific for the CD117 antigen can deplete malignant and healthy hematopoietic stem cells before consolidation with allogeneic hematopoietic stem cell transplantation in absence of cytotoxic conditioning. Here we exploit non-viral technology to achieve early termination of CAR T cell activity to prevent incoming graft rejection. Transient expression of an anti-CD117 CAR by mRNA conferred T cells the ability to eliminate CD117+ targets in vitro and in vivo. As an alternative approach, we used a Sleeping Beauty transposon vector for the generation of CAR T cells incorporating an inducible Caspase 9 safety switch. Stable CAR expression was associated with high proportion of T memory stem cells, low levels of exhaustion markers, and potent cellular cytotoxicity. Anti-CD117 CAR T cells mediated depletion of leukemic cells and healthy hematopoietic stem cells in NSG mice reconstituted with human leukemia or CD34+ cord blood cells, respectively, and could be terminated in vivo. The use of a non-viral technology to control CAR T cell pharmacokinetic properties is attractive for a first-in-human study in patients with acute myeloid leukemia prior to hematopoietic stem cell transplantation.

Structural insights into the interaction of three Y-shaped ligands with PI3Kα

Class IA phosphoinositide 3-kinase alpha (PI3Kα) is an important drug target because it is one of the most frequently mutated proteins in human cancers. However, small molecule inhibitors currently on the market or under development have safety concerns due to a lack of selectivity. Therefore, other chemical scaffolds or unique mechanisms of catalytic kinase inhibition are needed. Here, we report the cryo-electron microscopy structures of wild-type PI3Kα, the dimer of p110α and p85α, in complex with three Y-shaped ligands [cpd16 (compound 16), cpd17 (compound 17), and cpd18 (compound 18)] of different affinities and no inhibitory effect on the kinase activity. Unlike ATP-competitive inhibitors, cpd17 adopts a Y-shaped conformation with one arm inserted into a binding pocket formed by R770 and W780 and the other arm lodged in the ATP-binding pocket at an angle that is different from that of the ATP phosphate tail. Such a special interaction induces a conformation of PI3Kα resembling that of the unliganded protein. These observations were confirmed with two isomers (cpd16 and cpd18). Further analysis of these Y-shaped ligands revealed the structural basis of differential binding affinities caused by stereo- or regiochemical modifications. Our results may offer a different direction toward the design of therapeutic agents against PI3Kα.

Deep Learning Approach for the Discovery of Tumor-Targeting Small Organic Ligands from DNA-Encoded Chemical Libraries

DNA-Encoded Chemical Libraries (DELs) have emerged as efficient and cost-effective ligand discovery tools, which enable the generation of protein-ligand interaction data of unprecedented size. In this article, we present an approach that combines DEL screening and instance-level deep learning modeling to identify tumor-targeting ligands against carbonic anhydrase IX (CAIX), a clinically validated marker of hypoxia and clear cell renal cell carcinoma. We present a new ligand identification and hit-to-lead strategy driven by machine learning models trained on DELs, which expand the scope of DEL-derived chemical motifs. CAIX-screening datasets obtained from three different DELs were used to train machine learning models for generating novel hits, dissimilar to elements present in the original DELs. Out of the 152 novel potential hits that were identified with our approach and screened in an in vitro enzymatic inhibition assay, 70% displayed submicromolar activities (IC₅₀ < 1 μM). To generate lead compounds that are functionalized with anticancer payloads, analogues of top hits were prioritized for synthesis based on the predicted CAIX affinity and synthetic feasibility. Three lead candidates showed accumulation on the surface of CAIX-expressing tumor cells in cellular binding assays. The best compound displayed an in vitro K_D of 5.7 nM and selectively targeted tumors in mice bearing human renal cell carcinoma lesions. Our results demonstrate the synergy between DEL and machine learning for the identification of novel hits and for the successful translation of lead candidates for in vivo targeting applications.

A Comparative Analysis of Fibroblast Activation Protein-Targeted Small Molecule-Drug, Antibody-Drug, and Peptide-Drug Conjugates

We present the first in vivo comparative evaluation of chemically defined antibody-drug conjugates (ADCs), small molecule-drug conjugates (SMDCs), and peptide-drug conjugates (PDCs) targeting and activated by fibroblast activation protein (FAP) in solid tumors. Both the SMDC (OncoFAP-Gly-Pro-MMAE) and the ADC (7NP2-Gly-Pro-MMAE) candidates delivered high amounts of active payload (i.e., MMAE) selectively at the tumor site, thus producing a potent antitumor activity in a preclinical cancer model.

Targeted delivery of tumor necrosis factor in combination with CCNU induces a T cell-dependent regression of glioblastoma

Glioblastoma is the most aggressive primary brain tumor with an unmet need for more effective therapies. Here, we investigated combination therapies based on L19TNF, an antibody-cytokine fusion protein based on tumor necrosis factor that selectively localizes to cancer neovasculature. Using immunocompetent orthotopic glioma mouse models, we identified strong anti-glioma activity of L19TNF in combination with the alkylating agent CCNU, which cured the majority of tumor-bearing mice, whereas monotherapies only had limited efficacy. In situ and ex vivo immunophenotypic and molecular profiling in the mouse models revealed that L19TNF and CCNU induced tumor DNA damage and treatment-associated tumor necrosis. In addition, this combination also up-regulated tumor endothelial cell adhesion molecules, promoted the infiltration of immune cells into the tumor, induced immunostimulatory pathways, and decreased immunosuppression pathways. MHC immunopeptidomics demonstrated that L19TNF and CCNU increased antigen presentation on MHC class I molecules. The antitumor activity was T cell dependent and completely abrogated in immunodeficient mouse models. On the basis of these encouraging results, we translated this treatment combination to patients with glioblastoma. The clinical translation is ongoing but already shows objective responses in three of five patients in the first recurrent glioblastoma patient cohort treated with L19TNF in combination with CCNU (NCT04573192).

An Antibody Targeting Fibroblast Activation Protein Simultaneously Fused to Interleukin-2 and Tumor Necrosis Factor Selectively Localizes to Neoplastic Lesions

The delivery of specific cytokine payloads to a neoplastic environment employing antibodies able to selectively accumulate at the tumor site represents an attractive strategy to stimulate an immune response to cancer. Whilst conventional antibody-cytokine fusions based on a single payload have shown potent anticancer activity, the concomitant delivery of two cytokine payloads may further improve the therapeutic outcome as the immune system typically adopts multiple signals to reinforce an antitumor strategy. We here describe a potency-matched dual-cytokine antibody fusion protein containing a tumor-targeting antibody fragment specific to human fibroblast activation protein (FAP), simultaneously linked to both interleukin-2 (IL2) and a tumor necrosis factor (TNF) mutant. The resulting fusion protein, termed IL2-7NP2-TNF^mut, formed stable non-covalent trimers driven by the interaction of the tumor necrosis factor subunits. Both cytokine payloads retained their biological activity within the fusion protein, as shown by in vitro cellular assays. The tumor-targeting properties and the anticancer activity of IL2-7NP2-TNF^mut were investigated in vivo in immunocompromised mice bearing SKRC52 cells transduced with human FAP. The fusion protein preferentially localized to the cancer site and induced partial tumor retardation.

Abstract 2838: Tumor-targeted interleukin-2 enhances the anti-cancer activity of multivalent OncoFAP radioligand therapeutics

Radioligand Therapeutics (RLTs) are products composed of a tumor-targeting small organic ligand and a biocidal radioactive payload. The therapeutic potential of RLTs strongly depends on their uptake and residence time in tumors and in the healthy structures after administration. Fibroblast Activation Protein (FAP) is a cell surface antigen abundantly expressed in the microenvironment of the majority of solid human cancers of epithelial origin. We have recently described OncoFAP, an ultra-high affinity ligand of FAP whose targeting performances have been validated by Nuclear Medicine in patients with a wide variety of solid malignancies. Multivalent OncoFAP radioligand therapeutics (OncoFAP-RLTs) show high and prolonged tumor uptake with favorable tumor-to-organ ratios. Here we describe the development of novel multivalent OncoFAP-RLTs and their combination with a clinical-stage tumor-targeted interleukin-2 (L19-IL2). We designed and synthesized a set of multivalent OncoFAP derivatives, aiming at maximizing their affinity for the target protein and their residence time in the catalytic pocket of FAP. The multivalent ligands were coupled to the DOTAGA chelator, suitable for radiolabeling with 177Lu for therapeutic application. The tumor targeting properties of the multivalent OncoFAP ligands were investigated in a comparative biodistribution study in SK-RC-52.hFAP tumor-bearing mice. 177Lu-OncoFAP-23 emerged for its superior uptake and residence time in tumors and for its favorable tumor-to-kidney ratio. Moreover, when administered at very low dose 177Lu-OncoFAP-23 exhibited an enhanced anticancer activity compared to a monovalent (177Lu-OncoFAP-DOTAGA) and bivalent (177Lu-BiOncoFAP-DOTAGA) version of OncoFAP. When OncoFAP-based RLTs were combined with L19-IL2, a strong synergistic anticancer activity was observed. This synergy is driven by NK-cell mediated immune response directed to the tumor, with the concomitant release of granzymes and other pro-apoptotic proteins in the tumor microenvironment. Our findings heighten OncoFAP-based RLTs as promising anti-cancer drugs for treatment of FAP-positive tumors, alone or in combination with targeted interleukin-2.

Citation Format: Andrea Galbiati, Matilde Bocci, Ettore Gilardoni, Aureliano Zana, Dario Neri, Samuele Cazzamalli. Tumor-targeted interleukin-2 enhances the anti-cancer activity of multivalent OncoFAP radioligand therapeutics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2838.

Targeted Interleukin-9 delivery in pulmonary hypertension: Comparison of immunocytokine formats and effector cell study

AIMS

Pulmonary hypertension (PH) is accompanied by pulmonary vascular remodelling. By targeted delivery of Interleukin-9 (IL9) via the immunocytokine F8IL9, beneficial effects could be demonstrated in a mouse model of PH. This study aimed to compare two immunocytokine formats (single-chain Fv and full IgG) and to identify potential target cells of IL9.

METHODS

The Monocrotaline mouse model of PH (PH, n = 12) was chosen to evaluate the treatment effects of F8IL9F8 (n = 12) and F8IgGIL9 (n = 6) compared with sham-induced animals (control, n = 10), the dual endothelin receptor antagonist Macitentan (MAC, n = 12) or IL9-based immunocytokines with irrelevant antigen specificity (KSFIL9KSF, n = 12; KSFIgGIL9 n = 6). Besides comparative validation of treatment effects, the study was focused on the detection and quantification of mast cells (MCs) and regulatory T cells (Tregs).

RESULTS

There was a significantly elevated systolic right ventricular pressure (104 ± 36 vs. 45 ± 17 mmHg) and an impairment of right ventricular echocardiographic parameters (RVbasal: 2.52 ± 0.25 vs. 1.94 ± 0.13 mm) in untreated PH compared with controls (p < 0.05). Only the groups treated with F8IL9, irrespective of the format, showed consistent beneficial effects (p < 0.05). Moreover, F8IL9F8 but not F8IgGIL9 treatment significantly reduced lung tissue damage compared with untreated PH mice (p < 0.05). There was a significant increase in Tregs in F8IL9-treated compared with control animals, the untreated PH and the MAC group (p < 0.05).

CONCLUSIONS

Beneficial treatment effects of targeted IL9 delivery in a preclinical model of PH could be convincingly validated. IL9-mediated recruitment of Tregs into lung tissue might play a crucial role in the induction of anti-inflammatory and anti-proliferative mechanisms potentially contributing to a novel disease-modifying concept.

Cross-reactivity to glutamate carboxypeptidase III causes undesired salivary gland and kidney uptake of PSMA-targeted small-molecule radionuclide therapeutics

PURPOSE

Recently, Pluvicto™ ([177Lu]Lu-PSMA-617), a small-molecule prostate-specific membrane antigen (PSMA) radioligand therapeutic, has been approved by the FDA in metastatic castration-resistant prostate cancer. Pluvicto™ and other PSMA-targeting radioligand therapeutics (RLTs) have shown side effects due to accumulation in certain healthy tissues, such as salivary glands and kidney. Until now, the molecular mechanism underlying the undesired accumulation of PSMA-targeting RLTs had not been elucidated.

METHODS

We compared the sequence of PSMA with the entire human proteome to identify proteins closely related to the target. We have identified glutamate carboxypeptidase III (GCPIII), N-acetylated alpha-linked acidic dipeptidase like 1 (NAALADL-1), and transferrin receptor 1 (TfR1) as extracellular targets with the highest similarity to PSMA. The affinity of compound 1 for PSMA, GCPIII, NAALADL-1, and TfR1 was measured by fluorescence polarization. The expression of the putative anti-target GCPIII was assessed by immunofluorescence on human salivary glands and kidney, using commercially available antibodies.

RESULTS

A fluorescent derivative of Pluvicto™ (compound 1) bound tightly to PSMA and to GCPIII in fluorescence polarization experiments, while no interaction was observed with NAALADL-1 and TfR1. Immunofluorescence analysis revealed abundant expression of GCPIII both in healthy human kidney and salivary glands.

CONCLUSION

We conclude that the membranous expression of GCPIII in kidney and salivary gland may be the underlying cause for unwanted accumulation of Pluvicto™ and other Glu-ureido PSMA radio pharmaceuticals in patients.

An Engineered IFNγ-Antibody Fusion Protein with Improved Tumor-Homing Properties

Interferon-gamma (IFNγ) is one of the central cytokines produced by the innate and adaptive immune systems. IFNγ directly favors tumor growth control by enhancing the immunogenicity of tumor cells, induces IP-10 secretion facilitating (CXCR3+) immune cell infiltration, and can prime macrophages to an M1-like phenotype inducing proinflammatory cytokine release. We had previously reported that the targeted delivery of IFNγ to neoplastic lesions may be limited by the trapping of IFNγ-based products by cognate receptors found in different organs. Here we describe a novel fusion protein consisting of the L19 antibody, specific to the alternatively spliced extra-domain B of fibronectin (EDB), fused to a variant of IFNγ with reduced affinity to its cognate receptor. The product (named L19-IFNγ KRG) selectively localized to tumors in mice, showed favorable pharmacokinetic profiles in monkeys and regained biological activity upon antigen binding. The fusion protein was investigated in two murine models of cancer, both as monotherapy and in combination with therapeutic modalities which are frequently used for cancer therapy. L19-IFNγ KRG induced tumor growth retardation and increased the intratumoral concentration of T cells and NK cells in combination with anti-PD-1.

Generation of a novel fully human non-superagonistic anti-CD28 antibody with efficient and safe T-cell co-stimulation properties

Antibody-based therapeutics represent an important class of biopharmaceuticals in cancer immunotherapy. CD3 bispecific T-cell engagers activate cytotoxic T-cells and have shown remarkable clinical outcomes against several hematological malignancies. The absence of a costimulatory signal through CD28 typically leads to insufficient T-cell activation and early exhaustion. The combination of CD3 and CD28 targeting products offers an attractive strategy to boost T-cell activity. However, the development of CD28-targeting therapies ceased after TeGenero's Phase 1 trial in 2006 evaluating a superagonistic anti-CD28 antibody (TGN1412) resulted in severe life-threatening side effects. Here, we describe the generation of a novel fully human anti-CD28 antibody termed "E1P2" using phage display technology. E1P2 bound to human and mouse CD28 as shown by flow cytometry on primary human and mouse T-cells. Epitope mapping revealed a conformational binding epitope for E1P2 close to the apex of CD28, similar to its natural ligand and unlike the lateral epitope of TGN1412. E1P2, in contrast to TGN1412, showed no signs of in vitro superagonistic properties on human peripheral blood mononuclear cells (PBMCs) using different healthy donors. Importantly, an in vivo safety study in humanized NSG mice using E1P2, in direct comparison and contrast to TGN1412, did not cause cytokine release syndrome. In an in vitro activity assay using human PBMCs, the combination of E1P2 with CD3 bispecific antibodies enhanced tumor cell killing and T-cell proliferation. Collectively, these data demonstrate the therapeutic potential of E1P2 to improve the activity of T-cell receptor/CD3 activating constructs in targeted immunotherapeutic approaches against cancer or infectious diseases.

Generation and in vivo characterization of a novel high-affinity human antibody targeting carcinoembryonic antigen

There are no effective treatment options for most patients with metastatic colorectal cancer (mCRC). mCRC remains a leading cause of tumor-related death, with a five-year survival rate of only 15%, highlighting the urgent need for novel pharmacological products. Current standard drugs are based on cytotoxic chemotherapy, VEGF inhibitors, EGFR antibodies, and multikinase inhibitors. The antibody-based delivery of pro-inflammatory cytokines provides a promising and differentiated strategy to improve the treatment outcome for mCRC patients. Here, we describe the generation of a novel fully human monoclonal antibody (termed F4) targeting the carcinoembryonic antigen (CEA), a tumor-associated antigen overexpressed in colorectal cancer and other malignancies. The F4 antibody was selected by antibody phage display technology after two rounds of affinity maturation. F4 in single-chain variable fragment format bound to CEA in surface plasmon resonance with an affinity of 7.7 nM. Flow cytometry and immunofluorescence on human cancer specimens confirmed binding to CEA-expressing cells. F4 selectively accumulated in CEA-positive tumors, as evidenced by two orthogonal in vivo biodistribution studies. Encouraged by these results, we genetically fused murine interleukin (IL) 12 to F4 in the single-chain diabody format. F4-IL12 exhibited potent antitumor activity in two murine models of colon cancer. Treatment with F4-IL12 led to an increased density of tumor-infiltrating lymphocytes and an upregulation of interferon γ expression by tumor-homing lymphocytes. These data suggest that the F4 antibody is an attractive delivery vehicle for targeted cancer therapy.

Fibroblast Activation Protein Triggers Release of Drug Payload from Non-internalizing Small Molecule Drug Conjugates in Solid Tumors

PURPOSE

Small molecule drug conjugates (SMDC) are modular anticancer prodrugs that include a tumor-targeting small organic ligand, a cleavable linker, and a potent cytotoxic agent. Most of the SMDC products that have been developed for clinical applications target internalizing tumor-associated antigens on the surface of tumor cells. We have recently described a novel non-internalizing small organic ligand (named OncoFAP) of fibroblast activation protein (FAP), a tumor-associated antigen highly expressed in the stroma of most solid human malignancies.

EXPERIMENTAL DESIGN

In this article, we describe a new series of OncoFAP-Drug derivatives based on monomethyl auristatin E (MMAE; a potent cytotoxic tubulin poison) and dipeptide linkers that are selectively cleaved by FAP in the tumor microenvironment.

RESULTS

The tumor-targeting potential of OncoFAP was confirmed in patients with cancer using nuclear medicine procedures. We used mass spectrometry methodologies to quantify the amount of prodrug delivered to tumors and normal organs, as well as the efficiency of the drug release process. Linkers previously exploited for anticancer drug conjugates were used as benchmark. We identified OncoFAP-Gly-Pro-MMAE as the best performing SMDC, which has now been prioritized for further clinical development. OncoFAP-Gly-Pro-MMAE selectively delivered more than 10% injected dose per gram of MMAE to FAP-positive tumors, with a tumor-to-kidney ratio of 16:1 at 24 hours post-injection.

CONCLUSIONS

The FAP-specific drug conjugates described in this article promise to be efficacious for the targeting of human malignancies. The extracellular release of potent anticancer payloads mediates durable complete remission in difficult-to-treat animal models of cancer.

Selection of a PD-1 blocking antibody from a novel fully human phage display library

Programmed cell death protein 1 (PD-1) is an immunoregulatory target which is recognized by different monoclonal antibodies, approved for the therapy of multiple types of cancer. Different anti-PD-1 antibodies display different therapeutic properties and there is a pharmaceutical interest to generate and characterize novel anti-PD-1 antibodies. We screened multiple human antibody phage display libraries to target novel epitopes on the PD-1 surface and we discovered a unique and previously undescribed binding specificity (termed D12) from a new antibody library (termed AMG). The library featured antibody fragments in single-chain fragment variable (scFv) format, based on the IGHV3-23*03 (VH ) and IGKV1-39*01 (Vκ) genes. The D12 antibody was characterized by surface plasmon resonance (SPR), cross-reacted with the Cynomolgus monkey antigen and bound to primary human T cells, as shown by flow cytometry. The antibody blocked the PD-1/PD-L1 interaction in vitro with an EC50 value which was comparable to the one of nivolumab, a clinically approved antibody. The fine details of the interaction between D12 and PD-1 were elucidated by x-ray crystallography of the complex at a 3.5 Å resolution, revealing an unprecedented conformational change at the N-terminus of PD-1 following D12 binding, as well as partial overlap with the binding site for the cognate PD-L1 and PD-L2 ligands which prevents their binding. The results of the study suggest that the expansion of antibody library repertoires may facilitate the discovery of novel binding specificities with unique properties that hold promises for the modulation of PD-1 activity in vitro and in vivo.

A Dimeric FAP-Targeting Small-Molecule Radioconjugate with High and Prolonged Tumor Uptake

Imaging procedures based on small-molecule radioconjugates targeting fibroblast activation protein (FAP) have recently emerged as a powerful tool for the diagnosis of a wide variety of tumors. However, the therapeutic potential of radiolabeled FAP-targeting agents is limited by their short residence time in neoplastic lesions. In this work, we present the development and in vivo characterization of BiOncoFAP, a new dimeric FAP-binding motif with an extended tumor residence time and favorable tumor-to-organ ratio. Methods: The binding properties of BiOncoFAP and its monovalent OncoFAP analog were assayed against recombinant human FAP. Preclinical experiments with ¹⁷⁷Lu-OncoFAP-DOTAGA (¹⁷⁷Lu-OncoFAP) and ¹⁷⁷Lu-BiOncoFAP-DOTAGA (¹⁷⁷Lu-BiOncoFAP) were performed on mice bearing FAP-positive HT-1080 tumors. Results: OncoFAP and BiOncoFAP displayed comparable subnanomolar dissociation constants toward recombinant human FAP in solution, but the bivalent BiOncoFAP bound more avidly to the target immobilized on solid supports. In a comparative biodistribution study, ¹⁷⁷Lu-BiOncoFAP exhibited a more stable and prolonged tumor uptake than ¹⁷⁷Lu-OncoFAP (∼20 vs. ∼4 percentage injected dose/g, respectively, at 24 h after injection). Notably, ¹⁷⁷Lu-BiOncoFAP showed favorable tumor-to-organ ratios with low kidney uptake. Both ¹⁷⁷Lu-OncoFAP and ¹⁷⁷Lu-BiOncoFAP displayed potent antitumor efficacy when administered at therapeutic doses to tumor-bearing mice. Conclusion: ¹⁷⁷Lu-BiOncoFAP is a promising candidate for radioligand therapy of cancer, with favorable in vivo tumor-to-organ ratios, a long tumor residence time, and potent anticancer efficacy.

CTIM-22. THE COMBINATION OF LOMUSTINE AND THE IMMUNOCYTOKINE L19TNF IS A PROMISING TREATMENT FOR RECURRENT GLIOBLASTOMA

Glioblastoma is the most aggressive primary brain tumor and adults and poorly immunogenic. Treatment options for recurrent glioblastoma after standard of care chemoradiation are limited Several immunotherapeutic strategies including peptide vaccination and immune checkpoint inhibition have so far failed to improve survival and except from potentially regorafenib, no other agent has demonstrated superior activity to lomustine. Therefore, there is an urgent need for more effective treatment strategies for recurrent glioblastoma. Here, we investigate a new treatment combination based on the alkylating chemotherapy lomustine and the tumor-stroma targeting antibody-cytokine fusion protein L19TNF in preclinical glioma models and patients with recurrent glioblastoma. The combination treatment with lomustine and L19TNF demonstrated strong synergistic anti-tumor activity in several immunocompetent orthotopic glioma models curing the majority of tumor-bearing mice, whereas other mono- or combination therapies for example with anti-PD1 had only limited anti-glioma activity. Investigations of the mechanism of action revealed that lomustine plus L19TNF led to intratumoral necrosis, DNA damage and triggered a strong local anti-tumor immune response with increased MHC-I expression, presentation of neoepitopes and increased abundance of tumor-infiltrating lymphoid cells. In the first patients treated within a phase I/II clinical trial (NCT04573192), the treatment was well tolerated, and durable objective tumor responses and disease stabilizations could be observed also in patients with an unmethylated MGMT promoter.

Anti-Extra Domain B Splice Variant of Fibronectin Antibody-Drug Conjugate Eliminates Tumors with Enhanced Efficacy When Combined with Checkpoint Blockade

Extra domain B splice variant of fibronectin (EDB+FN) is an extracellular matrix protein (ECM) deposited by tumor-associated fibroblasts, and is associated with tumor growth, angiogenesis, and invasion. We hypothesized that EDB+FN is a safe and abundant target for therapeutic intervention with an antibody-drug conjugate (ADC). We describe the generation, pharmacology, mechanism of action, and safety profile of an ADC specific for EDB+FN (EDB-ADC). EDB+FN is broadly expressed in the stroma of pancreatic, non-small cell lung (NSCLC), breast, ovarian, head and neck cancers, whereas restricted in normal tissues. In patient-derived xenograft (PDX), cell-line xenograft (CLX), and mouse syngeneic tumor models, EDB-ADC, conjugated to auristatin Aur0101 through site-specific technology, demonstrated potent antitumor growth inhibition. Increased phospho-histone H3, a pharmacodynamic biomarker of response, was observed in tumor cells distal to the target site of tumor ECM after EDB-ADC treatment. EDB-ADC potentiated infiltration of immune cells, including CD3+ T lymphocytes into the tumor, providing rationale for the combination of EDB-ADC with immune checkpoint therapy. EDB-ADC and anti-PD-L1 combination in a syngeneic breast tumor model led to enhanced antitumor activity with sustained tumor regressions. In nonclinical safety studies in nonhuman primates, EDB-ADC had a well-tolerated safety profile without signs of either on-target toxicity or the off-target effects typically observed with ADCs that are conjugated through conventional conjugation methods. These data highlight the potential for EDB-ADC to specifically target the tumor microenvironment, provide robust therapeutic benefits against multiple tumor types, and enhance activity antitumor in combination with checkpoint blockade.

OS08.7.A Lomustine and the immunocytokine L19TNF are a promising treatment combination for recurrent glioblastoma

Background

Treatment options for recurrent glioblastoma are limited and with the possible exception of regorafenib, no agent has demonstrated superior activity to lomustine. Therefore, there is an urgent need for more effective treatment strategies for recurrent glioblastoma. Here, we investigated different treatment combinations based on the tumor-stroma targeting antibody-cytokine fusion protein L19TNF in preclinical glioma models and translated the most effective treatment combination to patients with recurrent glioblastoma.

Material and Methods

Orthotopic immunocompetent mouse glioma models were used to study the anti-glioma activity of L19TNF in combination with anti-PD1, bevacizumab or lomustine. Tumor growth was monitored by MRI. Flow cytometry and microscopy were used to characterize tumor-infiltrating-immune cells. MHC immunoaffinity purification and mass spectrometry were used to characterize the MHC immunopeptidome. Genetic mouse models were used to study immune-dependent effects. Subsequently, we translated the most efficient treatment combination to patients with recurrent glioblastoma within a phase I/II clinical trial (NCT04573192).

Results

The combination of L19TNF and lomustine demonstrated strong synergistic anti-tumor activity in two immunocompetent orthotopic glioma models and cured a majority of tumor-bearing mice. In contrast, combinations with anti-PD-1 or bevacizumab had only limited anti-glioma activity. Furthermore, compared to the monotherapies, the combination of L19TNF and lomustine led to the strongest increase in tumor-infiltrating lymphoid cells as demonstrated by flow cytometry and microsopy and to the highest number of peptides presented in the context of MHC-I. The treatment effect was abrograted in different genetic immunodeficient mouse models. The treatment combination of L19TNF and lomustine was well tolerated in the first patients treated within a phase I/II clinical trial and we observed partial tumor responses also in patients with an unmethylated MGMT promoter.

Conclusion

The combination of L19TNF and lomustine demonstrated promising anti-glioma activity and patients are currently recruited within a phase I/II clinical trial for patients with recurrent glioblastoma.

Generation and in vivo validation of an IL-12 fusion protein based on a novel anti-human FAP monoclonal antibody

BACKGROUND

In this study, we describe the generation of a fully human monoclonal antibody (named '7NP2') targeting human fibroblast activation protein (FAP), an antigen expressed in the microenvironment of different types of solid neoplasms.

METHODS

7NP2 was isolated from a synthetic antibody phage display library and was improved by one round of mutagenesis-based affinity maturation. The tumor recognition properties of the antibody were validated by immunofluorescence procedures performed on cancer biopsies from human patients. A fusion protein consisting of the 7NP2 antibody linked to interleukin (IL)-12 was generated and the anticancer activity of the murine surrogate product (named mIL12-7NP2) was evaluated in mouse models. Furthermore, the safety of the fully human product (named IL12-7NP2) was evaluated in Cynomolgus monkeys.

RESULTS

Biodistribution analysis in tumor-bearing mice confirmed the ability of the product to selectively localize to solid tumors while sparing healthy organs. Encouraged by these results, therapy studies were conducted in vivo, showing a potent antitumor activity in immunocompetent and immunodeficient mouse models of cancer, both as single agent and in combination with immune checkpoint inhibitors. The fully human product was tolerated when administered to non-human primates.

CONCLUSIONS

The results obtained in this work provided a rationale for future clinical translation activities using IL12-7NP2.

Isolation of a Natural Killer Group 2D Small-Molecule Ligand from DNA-Encoded Chemical Libraries

Natural Killer Group 2D (NKG2D) is a homo-dimeric transmembrane protein which is typically expressed on the surface of natural killer (NK) cells, natural killer T (NKT) cells, gamma delta T (γδT) cells, activated CD8 positive T-cells and activated macrophages. Bispecific molecules, capable of bridging NKG2D with a target protein expressed on the surface of tumor cells, may be used to redirect the cytotoxic activity of NK-cells towards antigen-positive malignanT-cells. In this work, we report the discovery of a novel NKG2D small molecule binder [K D = (410±60) nM], isolated from a DNA-Encoded Chemical Library (DEL). The discovery of small organic NKG2D ligands may facilitate the generation of fully synthetic bispecific adaptors, which may serve as an alternative to bispecific antibody products and which may benefit from better tumor targeting properties.

Automated Radiosynthesis, Preliminary In Vitro/In Vivo Characterization of OncoFAP-Based Radiopharmaceuticals for Cancer Imaging and Therapy

FAP-targeted radiopharmaceuticals represent a breakthrough in cancer imaging and a viable option for therapeutic applications. OncoFAP is an ultra-high-affinity ligand of FAP with a dissociation constant of 680 pM. OncoFAP has been recently discovered and clinically validated for PET imaging procedures in patients with solid malignancies. While more and more clinical validation is becoming available, the need for scalable and robust procedures for the preparation of this new class of radiopharmaceuticals continues to increase. In this article, we present the development of automated radiolabeling procedures for the preparation of OncoFAP-based radiopharmaceuticals for cancer imaging and therapy. A new series of [⁶⁸Ga]Ga-OncoFAP, [¹⁷⁷Lu]Lu-OncoFAP and [¹⁸F]AlF-OncoFAP was produced with high radiochemical yields. Chemical and biochemical characterization after radiolabeling confirmed its excellent stability, retention of high affinity for FAP and absence of radiolysis by-products. The in vivo biodistribution of [¹⁸F]AlF-NOTA-OncoFAP, a candidate for PET imaging procedures in patients, was assessed in mice bearing FAP-positive solid tumors. The product showed rapid accumulation in solid tumors, with an average of 6.6% ID/g one hour after systemic administration and excellent tumor-to-healthy organs ratio. We have developed simple, quick, safe and robust synthetic procedures for the preparation of theranostic OncoFAP-compounds based on Gallium-68, Lutetium-177 and Fluorine-18 using the commercially available FASTlab synthesis module.

Mass Spectrometry-Based Method for the Determination of the Biodistribution of Tumor-Targeting Small Molecule-Metal Conjugates

Nuclear medicine plays a key role in modern diagnosis and cancer therapy. The development of tumor-targeting radionuclide conjugates (also named small molecule-radio conjugates (SMRCs)) represents a significant improvement over the clinical use of metabolic radiotracers (e.g., [¹⁸F]-fluorodeoxyglucose) for imaging and over the application of biocidal external beam radiations for therapy. During the discovery of SMRCs, molecular candidates must be carefully evaluated typically by performing biodistribution assays in preclinical tumor models. Quantification methodologies based on radioactive counts are typically demanding due to safety concerns, availability of radioactive materials, and infrastructures. In this article, we report the development of a mass spectrometry (MS)-based method for the detection and quantification of small molecule-metal conjugates (SMMCs) as cold surrogates of SMRCs. We applied this methodology for the evaluation of the biodistribution of a particular class of tumor-targeting drug candidates based on ^natLu, ^natGa, and ^natF and directed against fibroblast activation protein (FAP). The reliability of the liquid chromatography-MS (LC-MS) analysis was validated by a direct comparison of MS-based and radioactivity-based biodistribution data. The results show that MS biodistribution of stable isotope metal conjugates is an orthogonal tool for the preclinical characterization of different classes of radiopharmaceuticals.

Abstract LB535: A novel IL12-based immunocytokine targeting fibroblast activation protein (FAP) for the treatment of cancer

Immunocytokines, which consist of the fusion of cytokines to tumor targeting antibodies, represent a novel class of biopharmaceuticals that have great potential for cancer treatment. The use of these products improves the efficacy of the delivered drug by reducing related side effects and significantly enhances the therapeutic index of the payload. Over the past years, nuclear medicine studies have validated the Fibroblast Activation Protein (FAP) as a pantumoral antigen, with more than 28 different cancer types successfully imaged in patients. Since FAP is mostly undetectable in healthy organs, it has been considered as an attractive target for both imaging and therapeutic applications. For this reason, here we describe the generation of a novel fully human monoclonal antibody targeting FAP. The antibody was isolated from a synthetic antibody phage display library and its tumor recognition properties were validated by immunofluorescence performed on a commercial tissue microarray as well as on freshly frozen colon cancer biopsies from human patients. An ex vivo biodistribution analysis in mice confirmed the ability of anti-FAP in IgG1 format to selectively localize to solid tumors while sparing healthy organs. Furthermore, Pharmacokinetics (PK) studies in Cynomolgus Monkey showed no sink effects at early time points and a slow clearance from bloodstream as expected for IgG1 antibodies. Encouraged by these results, an antibody cytokine fusion (mIL12-FAP) based on the novel anti-FAP antibody was generated and characterized in vitro and in vivo, showing activation of the immune system both in immunocompetent and immunodeficient mouse models bearing FAP-positive tumors. mIL12-FAP exhibited strong anticancer activity in mice bearing CT26-FAP colon carcinomas which could be boosted by the combination with immune checkpoint inhibitors, leading to durable cancer eradication. The targeted delivery of mIL12 to the tumor microenvironment increased the infiltrate of tumor-specific lymphocytes and Natural Killer (NK) cells as compared to the control group without apparent evidence of toxicity.

Citation Format: Lisa Nadal, Frederik Peissert, Abdullah Elsayed, Chiara Libbra, Dario Neri, Roberto De Luca. A novel IL12-based immunocytokine targeting fibroblast activation protein (FAP) for the treatment of cancer [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 LB535.

Abstract LB527: A novel dimeric small molecule-radio conjugate targeting fibroblast activation protein with high and prolonged tumor uptake

Imaging procedures based on small molecule-radio conjugates targeting Fibroblast Activation Protein (FAP) are taking the spotlight in clinical practice for the diagnosis of a wide variety of cancer lesions. However, therapeutic applications of FAP-targeting radioligand therapeutics are limited by their short residence time in tumor lesions. We have recently described the discovery of OncoFAP, a novel ultra-high affinity ligand of FAP which has been already validated for PET imaging applications in more than twenty patients with solid tumors. In this abstract, we describe the development and in vivo characterization of BiOncoFAP, a dimeric FAP targeting small molecule based on OncoFAP. In particular, OncoFAP and BiOncoFAP displayed a superimposable affinity for recombinant human FAP (KD = 970 pM and 993 pM, respectively, measured by Fluorescence Polarization). Moreover, the two ligands exhibited a clear selectivity for the target, without significantly interacting with a wide panel of non-target proteins. BiOncoFAP was coupled to a DOTAGA chelator, suitable for radiolabeling with [177Lu]Lu for therapeutic applications. Cold [natLu]Lu-BiOncoFAP-DOTAGA showed an excellent stability in both mouse and human serum, with half-life longer than 5 days, supporting in vivo investigations. In a head-to-head in vivo biodistribution comparative study against [177Lu]Lu-OncoFAP-DOTAGA, [177Lu]Lu-BiOncoFAP-DOTAGA exhibited a more stable and prolonged residence time in FAP-positive tumors implanted in immunodeficient mice (~20% ID/g and ~200-to-1 tumor-to-blood ratio, 24 h after systemic administration). Notably, [177Lu]Lu-BiOncoFAP-DOTAGA did not significantly accumulate in healthy organs, thus showing an outstanding tumor-to-organ ratio (e.g., 12-to-1 tumor-to-kidney and 34-to-1 tumor-to-liver ratio, at the 24 h time point). These findings heighten BiOncoFAP as promising candidate for the development of anti-cancer radioligand therapeutics towards FAP-expressing tumor lesions.

Citation Format: Samuele Cazzamalli, Andrea Galbiati, Aureliano Zana, Matilde Bocci, Jacopo Millul, Jacqueline Mock, Abdullah Elsayed, Dario Neri. A novel dimeric small molecule-radio conjugate targeting fibroblast activation protein with high and prolonged tumor uptake [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 LB527.

Abstract LB522: Fibroblast activation protein triggers the release of drug payload from non-internalizing small molecule-drug conjugates in solid tumors

Small Molecule-Drug Conjugates (SMDCs) are modular anti-cancer pro-drugs that include a tumor-targeting small ligand, a cleavable linker and a potent cytotoxic agent. SMDC products that have been developed for clinical applications are targeting internalizing tumor-associated antigens expressed on the surface of tumor cells. We have recently developed a novel non-internalizing small organic ligand (named OncoFAP) of Fibroblast Activation Protein (FAP), a tumor-associated antigen highly expressed in the stroma of most of solid human malignancies. The tumor targeting performance of OncoFAP has been validated by nuclear medicine studies in patients with various solid tumors. In a previous study, we showed that OncoFAP can be used to produce non-internalizing SMDCs that are effective and well tolerated. Here, we describe a new series of OncoFAP-Drug derivatives based on the MMAE tubulin poison and dipeptide linkers that are selectively cleaved by FAP in the tumor microenvironment. We benchmarked the new SMDCs against OncoFAP-MMAE conjugates displaying linker modules which are widely used in approved and clinical stage Antibody-Drug Conjugates, including structures cleaved by Cathepsin B and by reducing agents. We selected OncoFAP-GlyPro-MMAE as the most efficacious and safe SMDC for further clinical development after quantitatively analyzing the biodistribution of MMAE released by OncoFAP-MMAE conjugates. OncoFAP-GlyPro-MMAE selectively delivers high amounts of MMAE at the site of disease, with a tumor-to-kidney ratio of 7-to-1 and of 16-to-1 at 6- and 24-hours post-injection, respectively. Our molecules based on the OncoFAP tumor-targeting ligand and FAP-cleavable linkers promise to be safe and effective against most of human malignancies.

Citation Format: Aureliano Zana, Andrea Galbiati, Ettore Gilardoni, Jacopo Millul, Theo Sturm, Riccardo Stucchi, Matilde Bocci, Abdullah Elsayed, Lisa Nadal, Martina Cirillo, Dario Neri, Samuele Cazzamalli. Fibroblast activation protein triggers the release of drug payload from non-internalizing small molecule-drug conjugates in 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 LB522.

Design and Characterization of Novel Antibody-Cytokine Fusion Proteins Based on Interleukin-21

Interleukin-21 (IL21) is a pleiotropic cytokine involved in the modulation of both innate and adaptive immunity. IL21 is mainly secreted by natural killer (NK) and activated CD4+ T-cells. The biology of this cytokine can be associated to proinflammatory responses reflecting its potent stimulatory activity of NK and CD8+ T-cells. Here we describe four formats of novel IL21-based antibody–cytokine fusion proteins, targeting the extra domain A (EDA) of fibronectin and explore their potential for cancer treatment. The fusion proteins were designed, expressed, and characterized. F8 in single-chain diabody (scDb) format fused to IL21 at its C-terminus exhibited a promising profile in size exclusion chromatography (SEC) and SDS-PAGE. The lead candidate was further characterized in vitro. A cell-based activity assay on murine cytotoxic T-cells showed that human IL21, compared to murine IL21 partially cross-reacted with the murine receptor. The prototype was able to recognize EDA as demonstrated by immunofluorescence analysis on tumor sections. In an in vivo quantitative biodistribution experiment, F8(scDb)-murine IL21 did not preferentially accumulate at the site of disease after intravenous injection, suggesting that additional protein engineering would be required to improve the tumor-homing properties of IL21-based product.

Universal encoding of next generation DNA-encoded chemical libraries

DNA-encoded chemical libraries (DELs) are useful tools for the discovery of small molecule ligands to protein targets of pharmaceutical interest. Compared with single-pharmacophore DELs, dual-pharmacophore DELs simultaneously display two chemical moieties on both DNA strands, and allow for the construction of highly diverse and pure libraries, with a potential for targeting larger protein surfaces. Although methods for the encoding of simple, fragment-like dual-display libraries have been established, more complex libraries require a different encoding strategy. Here, we present a robust and convenient "large encoding design" (LED), which facilitates the PCR-amplification of multiple codes distributed among two partially complementary DNA strands. We experimentally implemented multiple coding regions and we compared the new DNA encoding scheme with previously reported dual-display DEL modalities in terms of amplifiability and performance in test selections against two target proteins. With the LED methodology in place, we foresee the construction and screening of DELs of unprecedented sizes and designs.

Identification and Validation of New Interleukin-2 Ligands Using DNA-Encoded Libraries

Interleukin-2 (IL2) is a pro-inflammatory cytokine that plays a crucial role in immunity, which is increasingly being used for therapeutic applications. There is growing interest in developing IL2-based therapeutics which do not interact with the alpha subunit of the IL2 receptor (CD25) as this protein is primarily found on immunosuppressive regulatory T cells (T_regs). Screenings of a new DNA-encoded library, comprising 669,240 members, provided a novel series of IL2 ligands, subsequently optimized by medicinal chemistry. One of these molecules (compound 18) bound to IL2 with a dissociation constant of 0.34 μM was able to form a kinetically stable complex with IL2 in size-exclusion chromatography and recognized the CD25-binding site as evidenced by competition experiments with the NARA1 antibody. Compound 18 and other members of the series may represent the starting point for the discovery of potent small-molecule modulators of IL2 activity, abrogating the binding to CD25.

Modular assembly and encoding strategies for dual-display DNA-encoded chemical libraries

DNA-encoded chemical libraries (DELs) are increasingly being used for the discovery of protein ligands and can be constructed displaying either one or two molecules at the extremities of the two complementary DNA strands. Here, we describe that DELs, featuring the simultaneous display of two molecules, can be encoded using various types of DNA structures, which go beyond the use of conventional double-stranded DNA fragments. Specifically, we compared dual-display methodologies in hairpin, circular or linear formats in terms of polymerase chain reaction (PCR) amplifiability and performance in affinity capture selections. The methods reported in this article highlight the feasibility and modularity of the described encoding strategies and may thus further expand the scope of DNA-encoded chemistry, particularly for the identification of compounds which recognize adjacent epitopes on the surface of target proteins of interest.

DDRE-21. LOMUSTINE AND TARGETED-CYTOKINE THERAPY: A BENEFICIAL LIAISON FOR RECURRENT GLIOBLASTOMA

Treatment options for recurrent glioblastoma are limited and except from regorafenib (potentially), no other agent has demonstrated superior activity to lomustine. Therefore, there is an urgent need for more effective treatment strategies for recurrent glioblastoma.

We investigated the combination of lomustine or bevacizumab that are frequently used for recurrent glioblastoma with L19TNF (onfekafusp alfa), a systemically administered tumor-stroma targeting antibody-cytokine fusion protein that enables a targeted delivery of tumor-necrosis factor (TNF)a to the tumor. In immunocompetent orthotopic glioma mouse models, the combination of lomustine and L19TNF demonstrated the strongest anti-tumor activity, acted in synergy and cured a majority of tumor-bearing mice, whereas lomustine or L19TNF monotherapy only had only very limited anti-tumor activity. Ex vivo profiling of the tumors and tumor-infiltrating immune cells from immunocompetent or immunodeficient hosts demonstrated immune-dependent cytotoxic and cytostatic effects on the glioma cells, and a strong increase of tumor-infiltrating immune cells upon combination therapy in immunocompetent models. Based on these encouraging results, we translate this combinatorial therapy to patients with recurrent glioblastoma. For the first patients, the treatment with lomustine and L19TNF was well tolerated and led to stable disease with a reduction in tumor perfusion. More patients are recruited in an ongoing phase I/II clinical trial with lomustine and L19TNF for patients with recurrent glioblastoma (NCT04573192).

Specific Inhibitor of Placental Alkaline Phosphatase Isolated from a DNA-Encoded Chemical Library Targets Tumor of the Female Reproductive Tract

Placental alkaline phosphatase (PLAP) is an abundant surface antigen in the malignancies of the female reproductive tract. Nevertheless, the discovery of PLAP-specific small organic ligands for targeting applications has been hindered by ligand cross-reactivity with the ubiquitous tissue non-specific alkaline phosphatase (TNAP). In this study, we used DNA-encoded chemical libraries to discover a potent (IC₅₀ = 32 nM) and selective PLAP inhibitor, with no detectable inhibition of TNAP activity. Subsequently, the PLAP ligand was conjugated to fluorescein; it specifically bound to PLAP-positive tumors in vitro and targeted cervical cancer in vivo in a mouse model of the disease. Ultimately, the fluorescent derivative of the PLAP inhibitor functioned as a bispecific engager redirecting the killing of chimeric antigen receptor-T cells specific to fluorescein on PLAP-positive tumor cells.

Childhood consumption of ultra-processed foods and adiposity trajectories: a UK birth cohort study

Background

Worldwide consumption of ultra-processed foods (UPFs) is continued to rise. Growing evidence has linked higher consumption with elevated risks of obesity and non-communicable diseases in adults. However, the influence of UPFs on long-term adiposity trajectories have not been evaluated in children.

Methods

Prospective birth cohort data were obtained from the Avon Longitudinal Study of Parents and Children. English children with baseline dietary intakes from 3-day food diaries and repeated adiposity measures were followed up from ages 7-24 years. Outcomes included body mass index (BMI), weight, waist circumference (WC), fat mass index (FMI) and body fat percentage. UPFs were identified using the NOVA food classification. Child's consumption of UPFs was derived as a percentage of its weight contribution (gram per day) in the total diet and categorised into quintiles. Longitudinal associations were assessed using linear growth curve models and adjusted for study covariates.

Results

Of the 9025 children followed up over a median (IQR) of 10.2 (5.2-16.4) years. Trajectories of BMI, FMI, weight and WC increased by an additional 0.06 (95% CI, 0.04-0.08) kg/m2, 0.03 (0.01-0.05) kg/m2, 0.20 (0.11-0.28) kg and 0.17 (0.11-0.22) cm per year among those in the highest (vs. lowest) quintile of UPF consumption. Evidence of dose-response relationships were consistently observed with those in the two highest quintiles of UPF consumption showing significantly more rapid progression of BMI, weight, and WC.

Conclusions

Radical and effective public health actions that reduce children's exposure and consumption of UPFs are urgently needed to address the obesity epidemic in England and internationally.

Funding: CM and EV are funded by the National Institute for Health Research (NIHR) School for Public Health Research (SPHR), Grant Reference Number PD-SPH-2015. The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care.

Key messages

Children with highest (vs. lowest) quintile of ultra-processed food consumption had more rapid regression of BMI, FMI, weight and waist circumference from ages 7-24 years. Dose-response relationships were consistently observed in the two highest quintile of ultra-processed food consumption showing more rapid progression of BMI, weight and waist circumference.

SYST-03. A PHASE I/II STUDY TO EVALUATE SAFETY AND PRELIMINARY ACTIVITY OF THE TUMOR-TARGETING ANTIBODY-CYTOKINE FUSION PROTEIN L19TNF IN PATIENTS WITH GLIOBLASTOMA AT FIRST RELAPSE

Treatment options for recurrent glioblastoma are limited and there is a need for novel effective therapies. We previously demonstrated encouraging anti-tumor activity with the targeted delivery of tumor necrosis factor a (TNF) in preclinical orthotopic glioma models. TNF- a is a potent pro-inflammatory cytokine which may trigger strong anti-tumor immunity. However, its systemic administration at therapeutically active doses is hampered by toxic side effects. L19TNF is a fully human antibody-cytokine fusion protein, comprising TNF- a fused to the antibody L19 that binds a tumor-specific epitope of the extracellular matrix protein fibronectin. This allows a targeted delivery of therapeutically relevant doses of TNF to the tumor site upon intravenous administration while sparing healthy tissues. In this phase I/II open label, non-randomized, monocentric study, we investigated the safety and preliminary activity of L19TNF for patients with isocitrate dehydrogenase (IDH) wildtype World Health Organization (WHO) grade III / IV glioma at first relapse. Twenty patients were enrolled from 2019-2020 and treated with intravenous infusions of L19TNF. In the phase I part of the study, 6 patients were assigned to two different dose levels of L19TNF and a dose of 13 µg/kg was established as the recommended dose. In the phase II part 14 patients were treated at the recommended dose. No dose-limiting toxicities were observed and survival follow-up is ongoing. In almost all patients, we observed treatment-associated emerging tumor necrosis. For patients that had re-surgery at progression on or after treatment with L19TNF, we demonstrated increased numbers of tumor-infiltrating lymphocytes compared to the tumor tissue obtained at primary diagnosis. Translational studies to better understand the effects of L19TNF on a molecular and immunophenotypic level are ongoing. ClinicalTrials.gov Identifier: NCT 03779230

An Attenuated Targeted-TNF Localizes to Tumors In Vivo and Regains Activity at the Site of Disease

Antibody-cytokine fusion proteins (immunocytokines) are gaining importance for cancer therapy, but those products are often limited by systemic toxicity related to the activity of the cytokine payload in circulation and in secondary lymphoid organs. Tumor necrosis factor (TNF) is used as a pro-inflammatory payload to trigger haemorrhagic necrosis and boost anti-cancer immunity at the tumor site. Here we describe a depotentiated version of TNF (carrying the single point mutation I97A), which displayed reduced binding affinity to its cognate receptor tumor necrosis factor receptor 1 (TNFR-1) and lower biocidal activity. The fusion of the TNF(I97A) mutant to the L19 antibody promoted restoration of anti-tumor activity upon accumulation on the cognate antigen, the alternatively spliced EDB domain of fibronectin. In vivo administration of high doses (375 μg/Kg) of the fusion protein showed a potent anti-tumor effect without apparent toxicity compared with the wild type protein. L19-TNFI97A holds promise for the targeted delivery of TNF activity to neoplastic lesions, helping spare normal tissues.