Fusion Molecule Research Articles

Fusion protein of FGF21 and elastin-like peptide improves wound healing in diabetic mice via inflammation modulation, collagen synthesis, and vascular network formation

Chronic-healing skin wounds are a common complication in diabetic individuals. To alleviate patient suffering, there is a pressing demand for more effective strategies to expedite the repair of diabetic wounds. Fibroblast growth factor 21(FGF21) has been proven to accelerate wound healing, but its stability and ability to assist in the healing of diabetic ulcers have not met expectations. Therefore, we have fused FGF21 with an elastin-like peptide (ELP) to create a recombinant fusion protein (abbreviated as “ELF”) to increase the bioactivity and stability in vitro or in vivo. Our results demonstrated that ELF significantly improved the efficiency of FGF21 purification due to the inverse temperature responsive phase transition property of ELP. Meanwhile, the fusion strategy did not impair the structure of FGF21 or diminish its activity, as demonstrated by the highly similar secondary structure of ELF and FGF21, and their considerable inhibitory activity in the glucose consumption experiment of Huh-7 cells. An in vitro migration assay revealed that ELF promoted healing more effectively than either free FGF21 or ELP. Further in vivo study revealed the ability of ELF to improve skin wound healing quality, manifested by lower levels of inflammatory factors, more collagen formation and deposition, and the formation of robust vascular networks, though there was no significant difference in healing rate among the ELF, FGF21, and ELP groups. In conclusion, our study indicated that FGF21 and ELP fusion molecules could be developed as more efficient and cost-effective therapeutic strategies for diabetic wound healing.

A “Prime and Expand” strategy using the multifunctional fusion proteins to generate memory-like NK cells for cell therapy

Adoptive cellular therapy (ACT) using memory-like (ML) natural killer (NK) cells, generated through overnight ex vivo activation with IL-12, IL-15, and IL-18, has shown promise for treating hematologic malignancies. We recently reported that a multifunctional fusion molecule, HCW9201, comprising IL-12, IL-15, and IL-18 domains could replace individual cytokines for priming human ML NK cell programming (“Prime” step). However, this approach does not include ex vivo expansion, thereby limiting the ability to test different doses and schedules. Here, we report the design and generation of a multifunctional fusion molecule, HCW9206, consisting of human IL-7, IL-15, and IL-21 cytokines. We observed > 300-fold expansion for HCW9201-primed human NK cells cultured for 14 days with HCW9206 and HCW9101, an IgG1 antibody, recognizing the scaffold domain of HCW9206 (“Expand” step). This expansion was dependent on both HCW9206 cytokines and interactions of the IgG1 mAb with CD16 receptors on NK cells. The resulting “Prime and Expand” ML NK cells exhibited elevated metabolic capacity, stable epigenetic IFNG promoter demethylation, enhanced antitumor activity in vitro and in vivo, and superior persistence in NSG mice. Thus, the “Prime and Expand” strategy represents a simple feeder cell-free approach to streamline manufacturing of clinical-grade ML NK cells to support multidose and off-the-shelf ACT.

Targeted protein degradation systems to enhance Wnt signaling

Molecules that facilitate targeted protein degradation (TPD) offer great promise as novel therapeutics. The human hepatic lectin asialoglycoprotein receptor (ASGR) is selectively expressed on hepatocytes. We have previously engineered an anti-ASGR1 antibody-mutant RSPO2 (RSPO2RA) fusion protein (called SWEETS) to drive tissue-specific degradation of ZNRF3/RNF43 E3 ubiquitin ligases, which achieved hepatocyte-specific enhanced Wnt signaling, proliferation, and restored liver function in mouse models, and an antibody–RSPO2RA fusion molecule is currently in human clinical trials. In the current study, we identified two new ASGR1- and ASGR1/2-specific antibodies, 8M24 and 8G8. High-resolution crystal structures of ASGR1:8M24 and ASGR2:8G8 complexes revealed that these antibodies bind to distinct epitopes on opposing sides of ASGR, away from the substrate-binding site. Both antibodies enhanced Wnt activity when assembled as SWEETS molecules with RSPO2RA through specific effects sequestering E3 ligases. In addition, 8M24-RSPO2RA and 8G8-RSPO2RA efficiently downregulate ASGR1 through TPD mechanisms. These results demonstrate the possibility of combining different therapeutic effects and degradation mechanisms in a single molecule.

Virion-surface display of a chimeric immunoglobulin Fc domain facilitating uptake by antigen-presenting cells

Antigen-presenting cells (APCs) play an important role in virus infection control by bridging innate and adaptive immune responses. Macrophages and dendritic cells (DCs) possess various surface receptors to recognize/internalize antigens, and antibody binding can enhance pathogen-opsonizing uptake by these APCs via interaction of antibody fragment crystallizable (Fc) domains with Fc receptors, evoking profound pathogen control in certain settings. Here, we examined phagocytosis-enhancing potential of Fc domains directly oriented on a retroviral virion/virus-like particle (VLP) surface. We generated an expression vector coding a murine Fc fragment fused to the transmembrane region (TM) of a retroviral envelope protein, deriving expression of the Fc-TM fusion protein on the transfected cell surface and production of virions incorporating the chimeric Fc upon co-transfection. Incubation of Fc-displaying simian immunodeficiency virus (SIV) with murine J774 macrophages and bone marrow-derived DCs derived Fc receptor-dependent enhanced uptake, being visualized by imaging cytometry. Alternative preparation of a murine leukemia virus (MLV) backbone-based Fc-displaying VLP loading an influenza virus hemagglutinin (HA) antigen resulted in enhanced HA internalization by macrophages, stating antigen compatibility of the design. Results show that the Fc-TM fusion molecule can be displayed on certain viruses/VLPs and may be utilized as a molecular adjuvant to facilitate APC antigen uptake.

QiDongNing induces lung cancer cell apoptosis via triggering P53/DRP1-mediated mitochondrial fission.

Non-small-cell lung cancer (NSCLC) is a major cause of worldwide cancer death, posing a challenge for effective treatment. Our previous findings showed that Chinese herbal medicine (CHM) QiDongNing (QDN) could upregulate the expression of p53 and trigger cell apoptosis in NSCLC. Here, our objective was to investigate the mechanisms of QDN-induced apoptosis enhancement. We chose A549 and NCI-H460 cells for validation invitro, and LLC cells were applied to form a subcutaneous transplantation tumour model for validation in more depth. Our findings indicated that QDN inhibited multiple biological behaviours, including cell proliferation, cloning, migration, invasion and induction of apoptosis. We further discovered that QDN increased the pro-apoptotic BAX while inhibiting the anti-apoptotic Bcl2. QDN therapy led to a decline in adenosine triphosphate (ATP) and a rise in reactive oxygen species (ROS). Furthermore, QDN elevated the levels of the tumour suppressor p53 and the mitochondrial division factor DRP1 and FIS1, and decreased the mitochondrial fusion molecules MFN1, MFN2, and OPA1. The results were further verified by rescue experiments, the p53 inhibitor Pifithrin-α and the mitochondrial division inhibitor Mdivi1 partially inhibited QDN-induced apoptosis and mitochondrial dysfunction, whereas overexpression of p53 rather increased the efficacy of the therapy. Additionally, QDN inhibited tumour growth with acceptable safety invivo. In conclusion, QDN induced apoptosis via triggering p53/DRP1-mediated mitochondrial fission in NSCLC cells.

CD8-Targeted IL2 Unleashes Tumor-Specific Immunity in Human Cancer Tissue by Reviving the Dysfunctional T-cell Pool.

Tumor-specific CD8+ T cells are key effectors of antitumor immunity but are often rendered dysfunctional in the tumor microenvironment. Immune-checkpoint blockade can restore antitumor T-cell function in some patients; however, most do not respond to this therapy, often despite T-cell infiltration in their tumors. We here explored a CD8-targeted IL2 fusion molecule (CD8-IL2) to selectively reactivate intratumoral CD8+ T cells in patient-derived tumor fragments. Treatment with CD8-IL2 broadly armed intratumoral CD8+ T cells with enhanced effector capacity, thereby specifically enabling reinvigoration of the dysfunctional T-cell pool to elicit potent immune activity. Notably, the revival of dysfunctional T cells to mediate effector activity by CD8-IL2 depended on simultaneous antigen recognition and was quantitatively and qualitatively superior to that achieved by PD-1 blockade. Finally, CD8-IL2 was able to functionally reinvigorate T cells in tumors resistant to anti-PD-1, underscoring its potential as a novel treatment strategy for patients with cancer. Significance: Reinvigorating T cells is crucial for response to checkpoint blockade therapy. However, emerging evidence suggests that the PD-1/PD-L1 axis is not the sole impediment for activating T cells within tumors. Selectively targeting cytokines toward specific T-cell subsets might overcome these barriers and stimulate T cells within resistant tumors. See related article by Moynihan et al., p. 1206 (32).

Abstract 2474: Antitumoral efficacy of ASKG812, a Smartkine® based bifunctional PD-1-eIL-2 molecule, through enhancing T effector cis agonism

Abstract Cytokines are potent molecules, yet their broad application as therapeutics has been significantly hampered due to short PK, severe systemic toxicity, and narrow therapeutic window. To improve the developability of cytokines, AskGene has invented a proprietary cytokine platform (Smartkine®) to achieve its overarching objective of modulating immune reactions at a disease site in a selective and controlled manner. Several antibody-cytokine fusion molecules using the SmartKine® platform have been moving into preclinical and clinical development. ASKG812 is a unique fusion molecule composed of anti-PD-1 antibody and engineered IL-2 (eIL-2). The eIL-2 moiety also comprises a specific mask such that the eIL-2 molecule binding biases towards PD-1+ T effector cells in a cis agonism manner for improved efficacy and therapeutic window. In ex vivo human PBMC assays, we demonstrated that ASKG812 significantly reduced activity in PD-1− T and NK cells, and enhanced activity in PD-1+ T cells judged by levels of pSTAT5, Ki67 and Granzyme B. In a cytotoxicity assay, ASKG812 can efficiently induce PBMC-mediated killing of MDA-MB-231 tumor cells in a dose-dependent manner. Moreover, in both anti-PD-1 therapy responsive and non-responsive syngeneic mouse tumor models, ASKG812 showed robust efficacy; without noticeable toxicity compared to a reference anti-PD-1-IL-2v fusion molecule. In conclusion, these findings provide the basis for the development of this new generation of PD-1 cis-targeted IL-2R agonists with enhanced therapeutic potential for the clinical treatment of cancer. Citation Format: Chunxiao Yu, Kurt Shanebeck, Shiguang Yu, Jeanine Ruiz, Shichang Li, Stone D.-H Shi, Hong Ma, Yuefeng Lu. Antitumoral efficacy of ASKG812, a Smartkine® based bifunctional PD-1-eIL-2 molecule, through enhancing T effector cis agonism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2474.

Abstract 4083: Pre-clinical development of IAMA-005, a long-acting cytokine fusion of modified IL-2 and IFN-α

Abstract In 1990s, both IL-2 and IFN-α were approved as the first two immunotherapies for metastatic melanoma and renal cell carcinoma; IFN-α was also approved for hairy cell leukemia. Although the response rates are relatively low, along ~25%, those who responded have long term survival benefits. However, the severe toxicity especially in high dose prohibited their broad use in oncology. Recently, there have been tremendous interests in modifying these two cytokines in the efforts to reduce the toxicity and enhance the activity. One such effort is to enhance the binding of IL-2 to the intermediate affinity β/γ receptors, which are expressed and function on CD8 T cells and NK cells. Another effort is to reduce the binding of IL-2 to high affinity α/β/γ receptors which mostly expressed on Treg and stimulate the growth of Treg cells, which suppress immune responses. Recently, whether it’s better to target intermediate affinity or high affinity for cancer therapy has become controversial with some studies showing that high affinity receptor engagements are required for robust anti-tumor activity while others favoring intermediate affinity receptor engagement for better efficacy; However, the clinical comparison is still lacking to be sure which approach is better. Here we have developed a long-acting novel IL-2-Fc-IFN-α fusion molecule termed IAMA-005 that has mutations to reduce the toxicity effects of IL-2 and IFN-α. We have characterized this molecule preclinically both in vitro and in vivo. IAMA-005 has demonstrated a potent tumor cell killing activities in numerous cancer cell lines including BT-474, SK-OV-3, NCI-N87, OE19, HCC-1954, MDA-MB-231, MDA-MB-468. When combined with IAMA-004 (a Her2-CD47-CD16 tri-specific antibody) in vitro, the tumor cell killing activities were dramatically increased. In addition, IAMA-005 was also tested in patient-derived Ex-Vivo fluids (one malignant pleural effusion and one malignant asities) and demonstrated excellent tumor cell killing efficacies. In addition, the killing activities of IAMA-005 could be attributed to the specific part of the fusion molecule because of the TME immune cell compositions. The in vivo assays to demonstrate efficacy and safety are ongoing and will be presented in the poster. These results suggest that this fusion cytokine molecule may be used in monotherapy in certain indications and an excellent complementary therapeutic to antibody targeted therapies or immunotherapies when used in combination. Citation Format: Liming Liu, Zhen Han, Yang Fan, Qi Pan. Pre-clinical development of IAMA-005, a long-acting cytokine fusion of modified IL-2 and IFN-α [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4083.

Use of a Tissue-Targeting Recombinant Human Interleukin-22 Fusion Molecule (F-652) for the Treatment of Advanced Refractory Lower GI Acute Gvhd

Use of a Tissue-Targeting Recombinant Human Interleukin-22 Fusion Molecule (F-652) for the Treatment of Advanced Refractory Lower GI Acute Gvhd

Mitigating the aggregation challenge in immunocytokine production: Strategies during cell line development and purification optimization

The rapid growth of bispecific antibodies and antibody fusion molecules in biopharmaceuticals necessitates precise process development. The molecular design, the biophysical properties, such as protein hydrophobicity and charge-charge interactions, and the process development workflows are crucial to manage the critical quality attribute (CQA) of development candidates at the development and manufacturing stage. This study focuses on aggregation mitigation for an immunocytokine, HLX101, comprised of an engineered cytokine fused to the knob chain of a Knob-into-Hole IgG. Aggregation and other CQAs were monitored and controlled throughout cell line development (CLD), expression, and purification. Our study effectively identified HLX101 clone #10 as optimal for large-scale manufacturing by demonstrating stable expression and by balancing high yield with low aggregation. This was achieved by using purification process results to guide the selection of the final clone in the cell line development, integrating both processes to optimize overall outcomes in immunocytokine production. Thus, clone #10, with its favorable profile, emerged as more efficient, enhancing overall yield and quality. This underscores the importance of considering both upstream and downstream processes in immunocytokine production.

Gene therapy targeting the blood-brain barrier.

Endothelial cells are the building blocks of vessels in the central nervous system (CNS) and form the blood-brain barrier (BBB). An intact BBB limits permeation of large hydrophilic molecules into the CNS. Thus, the healthy BBB is a major obstacle for the treatment of CNS disorders with antibodies, recombinant proteins or viral vectors. Several strategies have been devised to overcome the barrier. A key principle often consists in attaching the therapeutic compound to a ligand of receptors expressed on the BBB, for example, the transferrin receptor (TfR). The fusion molecule will bind to TfR on the luminal side of brain endothelial cells, pass the endothelial layer by transcytosis and be delivered to the brain parenchyma. However, attempts to endow therapeutic compounds with the ability to cross the BBB can be difficult to implement. An alternative and possibly more straight-forward approach is to produce therapeutic proteins in the endothelial cells that form the barrier. These cells are accessible from blood circulation and have a large interface with the brain parenchyma. They may be an ideal production site for therapeutic protein and afford direct supply to the CNS.

Incretin-FGF21 fusion molecule maximizes metabolic effects in mice.

Incretin-FGF21 fusion molecule maximizes metabolic effects in mice.

A T cell receptor β chain-directed antibody fusion molecule activates and expands subsets of T cells to promote antitumor activity.

Despite the success of programmed cell death-1 (PD-1) and PD-1 ligand (PD-L1) inhibitors in treating solid tumors, only a proportion of patients respond. Here, we describe a first-in-class bifunctional therapeutic molecule, STAR0602, that comprises an antibody targeting germline Vβ6 and Vβ10 T cell receptors (TCRs) fused to human interleukin-2 (IL-2) and simultaneously engages a nonclonal mode of TCR activation with costimulation to promote activation and expansion of αβ T cell subsets expressing distinct variable β (Vβ) TCR chains. In solution, STAR0602 binds IL-2 receptors in cis with Vβ6/Vβ10 TCRs on the same T cell, promoting expansion of human Vβ6 and Vβ10 CD4+ and CD8+ T cells that acquire an atypical central memory phenotype. Monotherapy with a mouse surrogate molecule induced durable tumor regression across six murine solid tumor models, including several refractory to anti-PD-1. Analysis of murine tumor-infiltrating lymphocyte (TIL) transcriptomes revealed that expanded Vβ T cells acquired a distinct effector memory phenotype with suppression of genes associated with T cell exhaustion and TCR signaling repression. Sequencing of TIL TCRs also revealed an increased T cell repertoire diversity within targeted Vβ T cell subsets, suggesting clonal revival of tumor T cell responses. These immunological and antitumor effects in mice were recapitulated in studies of STAR0602 in nonhuman primates and human ex vivo models, wherein STAR0602 boosted human antigen-specific T cell responses and killing of tumor organoids. Thus, STAR0602 represents a distinct class of T cell-activating molecules with the potential to deliver enhanced antitumor activity in checkpoint inhibitor-refractory settings.

A pan-SARS-CoV-2-specific soluble angiotensin-converting enzyme 2-albumin fusion engineered for enhanced plasma half-life and needle-free mucosal delivery.

Immunocompromised patients often fail to raise protective vaccine-induced immunity against the global emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants. Although monoclonal antibodies have been authorized for clinical use, most have lost their ability to potently neutralize the evolving Omicron subvariants. Thus, there is an urgent need for treatment strategies that can provide protection against these and emerging SARS-CoV-2 variants to prevent the development of severe coronavirus disease 2019. Here, we report on the design and characterization of a long-acting viral entry-blocking angiotensin-converting enzyme 2 (ACE2) dimeric fusion molecule. Specifically, a soluble truncated human dimeric ACE2 variant, engineered for improved binding to the receptor-binding domain of SARS-CoV-2, was fused with human albumin tailored for favorable engagement of the neonatal fragment crystallizable receptor (FcRn), which resulted in enhanced plasma half-life and allowed for needle-free transmucosal delivery upon nasal administration in human FcRn-expressing transgenic mice. Importantly, the dimeric ACE2-fused albumin demonstrated potent neutralization of SARS-CoV-2 immune escape variants.

Use of a Tissue-Targeting Recombinant Human Interleukin-22 Fusion Molecule (F-652) for the Treatment of Advanced Refractory Lower GI Acute Gvhd

Background: Steroid-refractory (SR) gastrointestinal acute GVHD (GI aGVHD) is a serious complication after allogeneic hematopoietic transplantation (allo-HCT), and subsequent lines of treatment following steroid failure are often ineffective. The JAK 1/2 inhibitor ruxolitinib is the only FDA-approved treatment for SR aGVHD, and patients for whom ruxolitinib is not effective or not tolerated have limited therapeutic options and high mortality. Interleukin-22 (IL-22) is a tissue-protective IL-10-family cytokine that has been shown to support intestinal mucosa after damage, directly signaling to the intestinal epithelium and promoting its survival, regeneration, and production of innate antimicrobial molecules. F-652, a recombinant human (rh)IL-22 fusion protein composed of an IL-22 dimer and IgG2 Fc fragment, has recently been studied in a phase 2 trial for patients with newly diagnosed lower GI aGVHD, demonstrating a promising day 28 treatment response rate and improved gut microbial health. Given this, we examined F-652 administration in 3 patients with severe SR GI aGVHD. Methods: Three patients with hematologic malignancies underwent MUD allo-HCT with tacrolimus and methotrexate GVHD prophylaxis ( Table). The patients were initially treated for GI aGVHD with methylprednisolone at a dose of 2 mg/kg/day without response. All patients presented with or progressed to stage 4 gut aGVHD and failed several lines of therapy, including ruxolitinib. All patients also had multiple episodes of bacteremia and at least some degree of GVHD-associated GI bleeding. F-652 treatment was initiated under single-patient-use authorization as the 5 th-7 th line of therapy and was administered at a dose of 45 mcg/kg IV weekly. In vitro cultures suggested that rho kinase inhibition did not interfere with trophic effects of IL-22 on intestinal epithelium, so patients were permitted to continue belumosidil upon F-652 initiation. While there was concern that JAK inhibition could compromise the activity of IL-22, continuation of ruxolitinib was considered on a case-by-case basis. C-reactive protein (CRP) is an acute phase reactant induced by IL-22, and circulating CRP levels served as a pharmacodynamic marker of in vivo biologic activity of F-652. Results: Consistent CRP elevations were observed 3 days after F-652 dosing in patients A and C, both of whom demonstrated a reduction in GVHD symptoms following F-652 treatment. These CRP elevations occurred despite concurrent use of belumosidil in Patient A and ruxolitinib in Patient C. CRP levels increased in Patient B after the first two doses, but not the third ( Figure). By day 28 following F-652 initiation, 2-of-3 patients (A and C) achieved a partial response, with decreased stool output and resolution of GI bleeding. Patient A had experienced 21 episodes of bacteremia prior to initiating rhIL-22 therapy but continued to demonstrate a partial response at day 56 and resolutiuon of bacteremias. Further improvement during the continued treatment (12 total doses) allowed for hospital discharge after 14 months of hospitalization. Patient B received 4 failed lines of therapy beyond ruxolitinib and was experiencing GI bleeding necessitating frequent transfusions prior to F-652 initiation. The symptoms persisted following F-652 treatment, and the patient passed at day 149 post-HCT. Patient C continues on active F-652 treatment and remains in a partial response as of this submission (> 50 days after treatment initiation). Overall, F-652 treatment has been well tolerated, and no significant adverse events attributable to the drug were observed. Conclusions: This is the first report of IL-22 therapy in SR aGVHD. Treatment was well tolerated, and 2-of-3 patients achieved a response following rhIL-22 administration after failing multiple previous therapies. Whereas most treatments for GVHD target immune cells and deepen immunosuppression, IL-22 is understood to act directly upon epithelial cells where it can support tissue recovery, improve barrier function, and promote innate antimicrobial immunity. CRP elevations post-treatment suggest that IL-22 administration may be able to exert these effects even with concurrent use of a JAK inhibitor. Our findings support further development of this approach and provide proof-of-concept for the use of tissue-supportive strategies to enhance the recovery of damaged gastrointestinal mucosa in advanced lower GI aGVHD.

Development and characterization of a prototypic pan-amyloid clearing agent - a novel murine peptide-immunoglobulin fusion.

Systemic amyloidosis is a progressive disorder characterized by the extracellular deposition of amyloid fibrils and accessory proteins in visceral organs and tissues. Amyloid accumulation causes organ dysfunction and is not generally cleared by the immune system. Current treatment focuses on reducing amyloid precursor protein synthesis and slowing amyloid deposition. However, curative interventions will likely also require removal of preexisting amyloid deposits to restore organ function. Here we describe a prototypic pan-amyloid binding peptide-antibody fusion molecule (mIgp5) that enhances macrophage uptake of amyloid. The murine IgG1-IgG2a hybrid immunoglobulin with a pan amyloid-reactive peptide, p5, fused genetically to the N-terminal of the immunoglobulin light chain was synthesized in HEK293T/17 cells. The binding of the p5 peptide moiety was assayed using synthetic amyloid-like fibrils, human amyloid extracts and amyloid-laden tissues as substrates. Binding of radioiodinated mIgp5 with amyloid deposits in vivo was evaluated in a murine model of AA amyloidosis using small animal imaging and microautoradiography. The bioactivity of mIgp5 was assessed in complement fixation and in vitro phagocytosis assays in the presence of patient-derived amyloid extracts and synthetic amyloid fibrils as substrates and in the presence or absence of human serum. Murine Igp5 exhibited highly potent binding to AL and ATTR amyloid extracts and diverse types of amyloid in formalin-fixed tissue sections. In the murine model of systemic AA amyloidosis, 125I-mIgp5 bound rapidly and specifically to amyloid deposits in all organs, including the heart, with no evidence of non-specific uptake in healthy tissues. The bioactivity of the immunoglobulin Fc domain was uncompromised in the context of mIgp5 and served as an effective opsonin. Macrophage-mediated uptake of amyloid extract and purified amyloid fibrils was enhanced by the addition of mIgp5. This effect was exaggerated in the presence of human serum coincident with deposition of complement C5b9. Immunostimulatory, amyloid-clearing therapeutics can be developed by incorporating pan-amyloid-reactive peptides, such as p5, as a targeting moiety. The immunologic functionality of the IgG remains intact in the context of the fusion protein. These data highlight the potential use of peptide-antibody fusions as therapeutics for all types of systemic amyloidosis.

Tetanus toxin and botulinum neurotoxin-derived fusion molecules are effective bivalent vaccines.

Tetanus toxin (TeNT) and botulinum neurotoxins (BoNTs) are neuroprotein toxins, with the latter being the most toxic known protein. They are structurally similar and contain three functional domains: an N-terminal catalytic domain (light chain), an internal heavy-chain translocation domain (HN domain), and a C-terminal heavy chain receptor binding domain (Hc domain or RBD). In this study, fusion functional domain molecules consisting of the TeNT RBD (THc) and the BoNT/A RBD (AHc) (i.e., THc-Linker-AHc and AHc-Linker-THc) were designed, prepared, and identified. The interaction of each Hc domain and the ganglioside receptor (GT1b) or the receptor synaptic vesicle glycoprotein 2 (SV2) was explored in vitro. Their immune response characteristics and protective efficacy were investigated in animal models. The recombinant THc-linker-AHc and AHc-linker-THc proteins with the binding activity had the correct size and structure, thus representing novel subunit vaccines. THc-linker-AHc and AHc-linker-THc induced high levels of specific neutralizing antibodies, and showed strong immune protective efficacy against both toxins. The high antibody titers against the two novel fusion domain molecules and against individual THc and AHc suggested that the THc and AHc domains, as antigens in the fusion functional domain molecules, do not interact with each other and retain their full key epitopes responsible for inducing neutralizing antibodies. Thus, the recombinant THc-linker-AHc and AHc-linker-THc molecules are strong and effective bivalent biotoxin vaccines, protecting against two biotoxins simultaneously. Our experimental design will be valuable to develop recombinant double-RBD fusion molecules as potent bivalent subunit vaccines against bio-toxins. KEY POINTS: •Double-RBD fusion molecules from two toxins had the correct structure and activity. •THc-linker-AHc and AHc-linker-THc efficiently protected against both biotoxins. •Such bivalent biotoxin vaccines based on the RBD are a valuable experimental design.

Characterization of a recombinant factor IX molecule fused to coagulation factor XIII-B subunit.

Severe haemophilia B (HB) is characterized by spontaneous bleeding episodes, mostly into joints. Recurrent bleeds lead to progressive joint destruction called haemophilic arthropathy. The current concept of prophylaxis aims at maintaining the FIX level >3-5IU/dL, which is effective at reducing the incidence of haemophilic arthropathy. Extended half-life FIX molecules make it easier to achieve these target trough levels compared to standard FIX concentrates. We previously reported that the fusion of a recombinant FIX (rFIX) to factor XIII-B (FXIIIB) subunit prolonged the half-life of the rFIX-LXa-FXIIIB fusion molecule in mice and rats 3.9- and 2.2-fold, respectively, compared with rFIX-WT. However, the mechanism behind the extended half-life was not known. Mass spectrometry and ITC were used to study interactions of rFIX-LXa-FXIIIB with albumin. Pharmacokinetic analyses in fibrinogen-KO and FcRn-KO mice were performed to evaluate the effect of albumin and fibrinogen on in-vivo half-life of rFIX-LXa-FXIIIB. Finally saphenous vein bleeding model was used to assess in-vivo haemostatic activity of rFIX-LXa-FXIIIB. We report here the key interactions that rFIX-LXa-FXIIIB may have in plasma are with fibrinogen and albumin which may mediate its prolonged half-life. In addition, using the saphenous vein bleeding model, we demonstrate that rFIX-FXIIIB elicits functional clot formation that is indistinguishable from that of rFIX-WT.

A simplified function-first method for the discovery and optimization of bispecific immune engaging antibodies.

Bi-specific T-cell engager antibodies (BiTEs) are synthetic fusion molecules that combine multiple antibody-binding domains to induce active contact between T-cells and antigen expressing cells in the body. Blinatumomab, a CD19-CD3 BiTE is now a widely used therapy for relapsed B-cell malignancies, and similar BiTE therapeutics have shown promise for treating various other forms of cancer. The current process for new BiTE development is time consuming and costly, requiring characterization of the individual antigen binding domains, followed by bi-specific design, protein production, purification, and eventually functional screening. Here, we sought to establish a more cost-efficient approach for generating novel BiTE sequences and assessing bioactivity through a function first approach without purification. We generate a plasmid with a bi-modular structure to allow high-throughput exchange of either binding arm, enabling rapid screening of novel tumour-targeting single chain variable (scFv) domains in combination with the well-characterized OKT3 scFv CD3-targeting domain. We also demonstrate two systems for high throughput functional screening of BiTE proteins based on Jurkat T cells (referred to as BiTE-J). Using BiTE-J we evaluate four EGFRvIII-scFv sequenced in BiTE format, identifying two constructs with superior activity for redirecting T-cells against the EGFRvIII-tumour specific antigen. We also confirm activity in primary T cells, where novel EGFRvIII-BiTEs induced T cell activation and antigen selective tumor killing. We finally demonstrate similar exchange the CD3-interacting element of our bi-modular plasmid. By testing several novel CD3-targeting scFv elements for activity in EGFRvIII-targeted BiTEs, we were able to identify highly active BiTE molecules with desirable functional activity for downstream development. In summary, BiTE-J presents a low cost, high-throughput method for the rapid assessment of novel BiTE molecules without the need for purification and quantification.

Antibody-cytokine fusion breathes new life into glioblastoma therapy

An antibody-cytokine fusion molecule combined with chemotherapy induces tumor regression in mice and patients with recurrent glioblastoma by boosting antitumor immunity (Look etal.).