Therapeutic efficacy and safety of a human fusion construct targeting the TWEAK receptor Fn14 and containing a modified granzyme B

Development of chimeric Nanobody-Granzyme B functionalized ferritin nanoparticles for precise tumor therapy

T-cell lymphomas (TCLs) are heterogeneous malignancies with limited treatment options and poor outcomes. The efficacy of traditional T-cell therapies, including chimeric antigen receptor (CAR) T cells, is often constrained by immunosuppressive factors and the tumor microenvironment. On the other hand, although direct Granzyme B (GrB) administration can effectively induce tumor cell apoptosis, it lacks universal tumor targeting and efficient cellular entry mechanisms. To address these limitations, we developed a novel nanoparticle-based therapy for the precise targeting of TCL tumor cells and the delivery of GrB. We fused nanobody (Nb) targeting CD30 and CD5 with GrB and coupled them to human ferritin (h-HFn) using the Gv/Sd system, creating a novel therapeutic nanoparticle named BiCD30/5-GF, which specifically targets CD30 and CD5 receptors on TCL tumor cells. The Nb-GrB conjugation enhances tumor targeting, while a Gv/Sd linker coupled to h-HFn further improves cellular transport and targeting. Additionally, the multimerization of GrB enhances its effectiveness. These nanoparticles demonstrated superior binding affinity and cytotoxicity in vitro compared to conventional treatments. In vivo studies on tumor-bearing mice showed significant tumor suppression and prolonged survival following treatment with BiCD30/5-GF nanoparticles. We also extended similar nanoparticle strategies for gastric cancer therapy, targeting FGFR4-expressing tumor cells. Our findings highlight the potential of engineered nanoparticles as effective and targeted therapeutic agents across various tumor types, offering promising prospects for clinical translation in cancer treatment.

GrB-Fc-KS49, an anti-EMP2 granzyme B fusion protein therapeutic alters immune cell infiltration and suppresses breast cancer growth

BACKGROUND

Granzyme B (GrB) is a key effector molecule, delivered by cytotoxic T lymphocytes and natural killer cells during immune surveillance to induce cell death. Fusion proteins and immunoconjugates represent an innovative therapeutic approach to specifically deliver a deadly payload to target cells. Epithelial membrane protein-2 (EMP2) is highly expressed in invasive breast cancer (BC), including triple-negative BC (TNBC), and represents an attractive therapeutic target.

METHODS

We designed a novel fusion protein (GrB-Fc-KS49) composed of an active GrB fused to an anti-EMP2 single-chain antibody tethered through the immunoglobulin G heavy chain (Fc) domain. We assessed the construct's GrB enzymatic activity, anti-EMP2 binding affinity, and cytotoxicity against a panel of BC cells. The construct's pharmacokinetics (PK), toxicity profile, and in vivo efficacy were also evaluated.

RESULTS

GrB-Fc-KS49 exhibited comparable GrB enzymatic activity to commercial GrB, as well as high affinity to an EMP2 peptide, with the dissociation constant in the picomolar range. The fusion protein rapidly internalized into EMP2+cancer cells and showed in vitro cytotoxicity to cell lines expressing surface EMP2, with half-maximal cytotoxicity (IC50) values below 100 nM for most positive lines. Ex vivo stability at 37°C indicated a half-life exceeding 96 hours while in vivo PK indicated a biexponential plasma clearance, with a moderate initial clearance (t1/2α=18.4 hours) and a much slower terminal clearance rate (t1/2β=73.1 hours). No toxicity was measured in a Chem16 panel between the control and the GrB-Fc-KS49. In vivo, the GrB-Fc-KS49 showed efficacy against a TNBC syngeneic (4T1/FLuc) mouse model, reducing tumor volume and cell proliferation and increasing cell death compared with controls. Treatment using an EMT6 mouse model confirmed these results. In addition to a significant impact on cell proliferation, GrB-Fc-KS49 treatment also resulted in a dramatic increase of tumor-infiltrating CD45+ cells and redistribution of tumor-associated macrophages. Transcriptomic analysis of tumors post-treatment confirmed the remodeling of the immune tumor microenvironment by the GrB-Fc-KS49 immunotoxin.

CONCLUSIONS

GrB-Fc-KS49 showed high specificity and cytotoxicity towards EMP2-positive cells. In vivo, it reduced tumor burden and increased the recruitment of immune cells into the tumor, suggesting that GrB-Fc-KS49 is a promising therapeutic candidate against BC.

Enhancing the cytotoxicity of immunotoxins by facilitating their dissociation from target receptors under the reducing conditions of the endocytic pathway

Immunotoxins (ITs) are recombinant chimeric proteins that combine a protein toxin with a targeting moiety to facilitate the selective delivery of the toxin to cancer cells. Here, we present a novel strategy to enhance the cytosolic access of ITs by promoting their dissociation from target receptors under the reducing conditions of the endocytic pathway. We engineered monobodySS, a human fibronectin type III domain-based monobody with disulfide bond (SS)-containing paratopes, targeting receptors such as EGFR, EpCAM, Her2, and FAP. MonobodySS exhibited SS-dependent target receptor binding with a significant reduction in binding under reducing conditions. We then created monobodySS-based ITs carrying a 25 kDa fragment of Pseudomonas exotoxin A (PE25), termed monobodySS-PE25. These ITs showed dose-dependent cytotoxicity against target receptor-expressing cancer cells and a wider therapeutic window due to higher efficacy at lower doses compared to controls with SS reduction inhibited. ERSS/28-PE25, with a KD of 28 nM for EGFR, demonstrated superior tumor-killing potency compared to ER/21-PE25, which lacks an SS bond, at equivalent and lower doses. In vivo, ERSS/28-PE25 outperformed ER/21-PE25 in suppressing tumor growth in EGFR-overexpressing xenograft mouse models. This study presents a strategy for developing solid tumor-targeting ITs using SS-containing paratopes to enhance cytosolic delivery and antitumor efficacy.

The crosstalk between macrophages and cancer cells potentiates pancreatic cancer cachexia

With limited treatment options, cachexia remains a major challenge for patients with cancer. Characterizing the interplay between tumor cells and the immune microenvironment may help identify potential therapeutic targets for cancer cachexia. Herein, we investigate the critical role of macrophages in potentiating pancreatic cancer induced muscle wasting via promoting TWEAK (TNF-like weak inducer of apoptosis) secretion from the tumor. Specifically, depletion of macrophages reverses muscle degradation induced by tumor cells. Macrophages induce non-autonomous secretion of TWEAK through CCL5/TRAF6/NF-κB pathway. TWEAK promotes muscle atrophy by activating MuRF1 initiated muscle remodeling. Notably, tumor cells recruit and reprogram macrophages via the CCL2/CCR2 axis and disrupting the interplay between macrophages and tumor cells attenuates muscle wasting. Collectively, this study identifies a feedforward loop between pancreatic cancer cells and macrophages, underlying the non-autonomous activation of TWEAK secretion from tumor cells thereby providing promising therapeutic targets for pancreatic cancer cachexia.

Modeling antibody drug conjugate potential using a granzyme B antibody fusion protein

BACKGROUND

Antibody drug conjugates (ADCs) constitute a promising class of targeted anti-tumor therapeutics that harness the selectivity of monoclonal antibodies with the potency of cytotoxic drugs. ADC development is best suited to initially screening antibody candidates for desired properties that potentiate target cell cytotoxicity. However, validating and producing an optimally designed ADC requires expertise and resources not readily available to certain laboratories.

RESULTS

In this study, we propose a novel approach to help streamline the identification of potential ADC candidates by utilizing a granzyme B (GrB)-based antibody fusion protein (AFP) for preliminary screening. GrB is a non-immunogenic serine protease expressed by immune effector cells such as CD8 + T cells that induces apoptotic activity and can be leveraged for targeted cell killing.

CONCLUSIONS

Our innovative model allows critical antibody parameters (including target cell binding, internalization, and cytotoxic potential) to be more reliably evaluated in vitro through the creation of an ADC surrogate. Successful incorporation of this AFP could also significantly expand and enhance ADC development pre-clinically, ultimately leading to the accelerated translation of ADC therapies for patients.

Antibody-based soluble and membrane-bound TWEAK mimicking agonists with FcγR-independent activity

Fibroblast growth factor (FGF)-inducible 14 (Fn14) activates the classical and alternative NFκB (nuclear factor 'kappa-light-chain-enhancer' of activated B-cells) signaling pathway but also enhances tumor necrosis factor (TNF)-induced cell death. Fn14 expression is upregulated in non-hematopoietic cells during tissue injury and is also often highly expressed in solid cancers. In view of the latter, there were and are considerable preclinical efforts to target Fn14 for tumor therapy, either by exploiting Fn14 as a target for antibodies with cytotoxic activity (e.g. antibody-dependent cellular cytotoxicity (ADCC)-inducing IgG variants, antibody drug conjugates) or by blocking antibodies with the aim to interfere with protumoral Fn14 activities. Noteworthy, there are yet no attempts to target Fn14 with agonistic Fc effector function silenced antibodies to unleash the proinflammatory and cell death-enhancing activities of this receptor for tumor therapy. This is certainly not at least due to the fact that anti-Fn14 antibodies only act as effective agonists when they are presented bound to Fcγ receptors (FcγR). Thus, there are so far no antibodies that robustly and selectively engage Fn14 signaling without triggering unwanted FcγR-mediated activities. In this study, we investigated a panel of variants of the anti-Fn14 antibody 18D1 of different valencies and domain architectures with respect to their inherent FcγR-independent ability to trigger Fn14-associated signaling pathways. In contrast to conventional 18D1, the majority of 18D1 antibody variants with four or more Fn14 binding sites displayed a strong ability to trigger the alternative NFκB pathway and to enhance TNF-induced cell death and therefore resemble in their activity soluble (TNF)-like weak inducer of apoptosis (TWEAK), one form of the natural occurring ligand of Fn14. Noteworthy, activation of the classical NFκB pathway, which naturally is predominately triggered by membrane-bound TWEAK but not soluble TWEAK, was preferentially observed with a subset of constructs containing Fn14 binding sites at opposing sites of the IgG scaffold, e.g. IgG1-scFv fusion proteins. A superior ability of IgG1-scFv fusion proteins to trigger classical NFκB signaling was also observed with the anti-Fn14 antibody PDL192 suggesting that we identified generic structures for Fn14 antibody variants mimicking soluble and membrane-bound TWEAK.

Proteolytically generated soluble Tweak Receptor Fn14 is a blood biomarker for γ-secretase activity

Fn14 is a cell surface receptor with key functions in tissue homeostasis and injury but is also linked to chronic diseases. Despite its physiological and medical importance, the regulation of Fn14 signaling and turnover is only partly understood. Here, we demonstrate that Fn14 is cleaved within its transmembrane domain by the protease γ‐secretase, resulting in secretion of the soluble Fn14 ectodomain (sFn14). Inhibition of γ‐secretase in tumor cells reduced sFn14 secretion, increased full‐length Fn14 at the cell surface, and enhanced TWEAK ligand‐stimulated Fn14 signaling through the NFκB pathway, which led to enhanced release of the cytokine tumor necrosis factor. γ‐Secretase‐dependent sFn14 release was also detected ex vivo in primary tumor cells from glioblastoma patients, in mouse and human plasma and was strongly reduced in blood from human cancer patients dosed with a γ‐secretase inhibitor prior to chimeric antigen receptor (CAR)‐T‐cell treatment. Taken together, our study demonstrates a novel function for γ‐secretase in attenuating TWEAK/Fn14 signaling and suggests the use of sFn14 as an easily measurable pharmacodynamic biomarker to monitor γ‐secretase activity in vivo.

Fn14-targeted BiTE and CAR-T cells demonstrate potent preclinical activity against glioblastoma

T cell-engaging therapies involving bispecific T cell engager (BiTE) and chimeric antigen receptor T (CAR-T) cells have achieved great success in the treatment of hematological tumors. However, the paucity of ideal cell surface molecules that can be targeted on glioblastoma (GBM) partially reduces the immunotherapeutic efficacy. Recently, high expression of Fn14 has been reported in several solid tumors, so the strategy of exploiting this specific antigen for GBM immunotherapy is worth studying. Consequently, we constructed Fn14× CD3 BiTE and Fn14-specific CAR-T cells and investigated their cytotoxic activity against GBM in vitro and in vivo. First, expression of Fn14 was confirmed in glioma tissues and GBM cells. Then, we designed Fn14-specific BiTE and CAR-T cells and tested their cytotoxicity in GBM cell cultures and mouse models of GBM. Fn14 was highly expressed in GBM tissues and cell lines, while it was undetectable in normal brain samples. Fn14× CD3 BiTE, Fn14 CAR-T cells and Fn14 CAR-T/IL-15 cells were antigen-specific and highly cytotoxic, showing good antitumor activity in vitro and causing significant regression of established solid tumors in xenograft models. However, the xenografts treated with Fn14 CAR-T cells regrew, whereas xenografts treated with Fn14 CAR-T/IL-15 cells did not. IL-15 engineering augmented the antitumor activity of Fn14 CAR-T cells and resulted in significant antitumor effects similar to those of Fn14× CD3 BiTE. Our results suggest that Fn14 is an appropriate target for GBM. Anti-Fn14 BiTE and Fn14-specific CAR-T/IL-15 cells may be exciting immunotherapeutic options for malignant brain cancer.