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The state of the art in biopharmaceutical FUSION PROTEIN DESIGN Fusion proteins belong to the most lucrative biotech drugs—with Enbrel® being one of the best-selling biologics worldwide. Enbrel® represents a milestone of modern therapies just as Humulin®, the first therapeutic recombinant protein for human use, approved by the FDA in 1982 and Orthoclone® the first monoclonal antibody reaching the market in 1986. These first generation molecules were soon followed by a plethora of recombinant copies of natural human proteins, and in 1998, the first de novo designed fusion protein was launched. Fusion Protein Technologies for Biopharmaceuticals examines the state of the art in developing fusion proteins for biopharmaceuticals, shedding light on the immense potential inherent in fusion protein design and functionality. A wide pantheon of international scientists and researchers deliver a comprehensive and complete overview of therapeutic fusion proteins, combining the success stories of marketed drugs with the dynamic preclinical and clinical research into novel drugs designed for as yet unmet medical needs. The book covers the major types of fusion proteins—receptor-traps, immunotoxins, Fc-fusions and peptibodies—while also detailing the approaches for developing, delivering, and improving the stability of fusion proteins. The main body of the book contains three large sections that address issues key to this specialty: strategies for extending the plasma half life, the design of toxic proteins, and utilizing fusion proteins for ultra specific targeting. The book concludes with novel concepts in this field, including examples of highly relevant multifunctional antibodies. Detailing the innovative science, commercial realities, and brilliant potential of fusion protein therapeutics, Fusion Protein Technologies for Biopharmaceuticals is a must for pharmaceutical scientists, biochemists, medicinal chemists, molecular biologists, pharmacologists, and genetic engineers interested in determining the shape of innovation in the world of biopharmaceuticals.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in Wuhan, China, at the end of 2019, and there are currently no specific antiviral treatments or vaccines available. SARS-CoV-2 has been shown to use the same cell entry receptor as SARS-CoV, angiotensin-converting enzyme 2 (ACE2). In this report, we generate a recombinant protein by connecting the extracellular domain of human ACE2 to the Fc region of the human immunoglobulin IgG1. A fusion protein containing an ACE2 mutant with low catalytic activity is also used in this study. The fusion proteins are then characterized. Both fusion proteins have a high binding affinity for the receptor-binding domains of SARS-CoV and SARS-CoV-2 and exhibit desirable pharmacological properties in mice. Moreover, the fusion proteins neutralize virus pseudotyped with SARS-CoV or SARS-CoV-2 spike proteins in vitro. As these fusion proteins exhibit cross-reactivity against coronaviruses, they have potential applications in the diagnosis, prophylaxis, and treatment of SARS-CoV-2. SARS-CoV-2 uses ACE2 as the entry receptor. Here, the authors show that an ACE2-Ig fusion protein inhibits entry of virus pseudotyped with the SARS-CoV-2 spike protein, show differential binding kinetics of SARS-CoV and SARSCoV-2 spike proteins to ACE2, and determine pharmakocinetic parameters of ACE2-Ig in mice.

A fusion protein comprising factor IX and the dimeric Fc domain of IgG1 has a half-life that is five times as long as that of native factor IX, allowing prophylactic injections to be spaced as far as 2 weeks apart while maintaining levels of factor IX that are sufficient to prevent bleeding. In patients with severe hemophilia B, recurrent bleeding leads to painful hemarthroses, disabling hemophilic arthropathy, and other sequelae. 1 , 2 Prophylactic replacement of coagulation factor IX is associated with improved clinical outcomes 3 – 7 ; however, the relatively short half-lives of currently available factor IX products necessitate frequent intravenous injections (two or three times weekly) to maintain protective levels (at or above 1 IU per deciliter). 8 , 9 The frequency of injections is a considerable burden, cited by patients as a key deterrent to undertaking prophylactic treatment. 10 Various strategies to reduce this burden and improve the treatment of hemophilia B are under investigation, . . .

To image hypoxia‐inducible factor‐1 (HIF‐1)‐active tumors, we previously developed a chimeric protein probe ([123/125I]IPOS) that is degraded in the same manner as HIF‐1α under normoxic conditions. In the present study, we aim to show that the accumulation of radioiodinated POS reflects the expression of HIF‐1. In vivo single‐photon emission computed tomography (SPECT)/X‐ray CT (CT) imaging, autoradiography, and double‐fluorescent immunostaining for HIF‐1α and pimonidazole (PIMO) were carried out 24 h after the injection of [125I]IPOS. Tumor metabolite analysis was also carried out. A tumor was clearly visualized by multi‐pinhole, high‐resolution SPECT/CT imaging with [125I]IPOS. The obtained images were in accordance with the corresponding autoradiograms and with the results of ex vivo biodistribution. A metabolite analysis revealed that 77% of the radioactivity was eluted in the macromolecular fraction, suggesting that the radioactivity mainly existed as [125I]IPOS in the tumors. Immunohistochemistry revealed that the HIF‐1α‐positive areas and PIMO‐positive areas were not always identical, only some of the regions were positive for both markers. The areas showing [125I]IPOS accumulation were positively and significantly correlated with the HIF‐1α‐positive areas (R = 0.75, P < 0.0001). The correlation coefficient between [125I]IPOS‐accumulated areas and HIF‐1α‐positive areas was significantly greater than that between the [125I]IPOS‐accumulated areas and the PIMO‐positive areas (P < 0.01). These findings indicate that [125I]IPOS accumulation reflects HIF‐1 expression. Thus, [123/125I]IPOS can serve as a useful probe for the molecular imaging of HIF‐1‐active tumors. (Cancer Sci 2011; 102: 2090–2096)

The purpose of making a “biobetter” biologic is to improve on the salient characteristics of a known biologic for which there is, minimally, clinical proof of concept or, maximally, marketed product data. There already are several examples in which second-generation or biobetter biologics have been generated by improving the pharmacokinetic properties of an innovative drug, including Neulasta ® [a PEGylated, longer-half-life version of Neupogen ® (filgrastim)] and Aranesp ® [a longer-half-life version of Epogen ® (epoetin-α)]. This review describes the use of protein fusion technologies such as Fc fusion proteins, fusion to human serum albumin, fusion to carboxy-terminal peptide, and other polypeptide fusion approaches to make biobetter drugs with more desirable pharmacokinetic profiles.

There are many factors that can influence the pharmacokinetics (PK) of a mAb or Fc-fusion molecule with the primary determinant being FcRn-mediated recycling. Through Fab or Fc engineering, IgG-FcRn interaction can be used to generate a variety of therapeutic antibodies with significantly enhanced half-life or ability to remove unwanted antigen from circulation. Glycosylation of a mAb or Fc-fusion protein can have a significant impact on the PK of these molecules. mAb charge can be important and variants with pI values of 1-2 unit difference are likely to impact PK with lower pI values being favorable for a longer half-life. Most mAbs display target mediated drug disposition (TMDD), which can have significant consequences on the study designs of preclinical and clinical studies. The PK of mAb can also be influenced by anti-drug antibody (ADA) response and off-target binding, which require careful consideration during the discovery stage. mAbs are primarily absorbed through the lymphatics via convection and can be conveniently administered by the subcutaneous (sc) route in large doses/volumes with co-formulation of hyaluronidase. The human PK of a mAb can be reasonably estimated using cynomolgus monkey data and allometric scaling methods.

Overexpression of MYC oncogene is highly prevalent in many malignancies such as aggressive triple-negative breast cancers (TNBCs) and it is associated with very poor outcome. Despite decades of research, attempts to effectively inhibit MYC, particularly with small molecules, still remain challenging due to the featureless nature of its protein structure. Herein, we describe the engineering of the dominant-negative MYC peptide (OmoMYC) linked to a functional penetrating ‘Phylomer’ peptide (FPPa) as a therapeutic strategy to inhibit MYC in TNBC. We found FPPa-OmoMYC to be a potent inducer of apoptosis (with IC 50 from 1–2 µM) in TNBC cells with negligible effects in non-tumorigenic cells. Transcriptome analysis of FPPa-OmoMYC-treated cells indicated that the fusion protein inhibited MYC-dependent networks, inducing dynamic changes in transcriptional, metabolic, and apoptotic processes. We demonstrated the efficacy of FPPa-OmoMYC in inhibiting breast cancer growth when injected orthotopically in TNBC allografts. Lastly, we identified strong pharmacological synergisms between FPPa-OmoMYC and chemotherapeutic agents. This study highlights a novel therapeutic approach to target highly aggressive and chemoresistant MYC-activated cancers.

Background Data comparing systemic exposure and systemic vascular endothelial growth factor (VEGF) suppression of ranibizumab, bevacizumab and aflibercept following intravitreal injection are lacking. Methods Fifty-six patients with wet age-related macular degeneration received intravitreal ranibizumab (0.5 mg), bevacizumab (1.25 mg), or aflibercept (2.0 mg). Serum pharmacokinetics and plasma free VEGF were evaluated after the first and third injections. Results Following the first dose, systemic exposure to aflibercept was 5-, 37-, and 9-fold higher than ranibizumab, whereas, bevacizumab was 9-, 310-, and 35-fold higher than ranibizumab, based on geometric mean ratio of peak and trough concentrations and area under the curve, respectively. The third dose showed accumulation of bevacizumab and aflibercept but not ranibizumab. Aflibercept substantially suppressed plasma free VEGF, with mean levels below lower limit of quantitation (10 pg/mL) as early as 3 h postdose until ≥7 days postdose. Mean free (unbound) VEGF levels with ranibizumab were largely unchanged, with mean trough level of 14.4 pg/mL compared with baseline of 17 pg/mL. Conclusions There are notable differences in systemic pharmacokinetics and pharmacodynamics among anti-VEGF treatments after intravitreal administration. All three agents rapidly moved into the bloodstream, but ranibizumab very quickly cleared, whereas bevacizumab and aflibercept demonstrated greater systemic exposure and produced a marked reduction in plasma free VEGF. Trial registration number NCT02118831.

Fc fusion proteins, formed by fusing an active protein to the Fc region of immunoglobulin G, are a validated strategy for extending the half-life of therapeutic proteins. Human growth hormone (hGH) Fc fusion proteins exhibit longer circulation half-lives than hGH, reducing injection frequency and improving convenience for hGH replacement therapy. Most approved Fc fusion proteins involve directly attaching the active protein to the hinge region of IgG Fc; however, few reports have described the effects of structural variations on these characteristics in detail. We analyzed pharmacokinetic and pharmacodynamic properties of various hGH-Fc fusion constructs differing in linker type, hGH valency, and fusion position to investigate the structure-function relationships of these proteins in cell-based assays and animal models, including normal and hypophysectomized rats. Monovalent hGH-Fc fusion variants and those with hGH fused to the C-terminal of IgG Fc exhibited higher in vitro and in vivo activity than bivalent hGH-Fc. However, these variants also exhibited accelerated clearance in rat pharmacokinetic experiments. The linker connecting the hGH moiety to the Fc domain significantly influenced in vitro activity and pharmacokinetics. Constructs with a rigid alpha-helical A(EAAAK) 5 A linker showed greater in vitro activity than those with a flexible (GGGGS) 3 linker but exhibited accelerated clearance in rats. To a lesser extent, linker length influenced activity and pharmacokinetics. Bivalent hGH-Fc constructs with shorter linkers (0–1 GGGGS repeats) exhibited higher in vivo exposure (AUC) but lower in vitro activity than those with longer linkers (2–3 repeats). In vitro activity did not correlate linearly with linker length, as constructs with no linker (n = 0) showed reduced activity, while no consistent trend was observed for n = 1–3. These findings provide valuable insights into the design of hGH-Fc fusion proteins, offering a framework for systematically improving their potency and longevity and supporting the development of long-acting hGH therapies.

ObjectiveFibroblast growth factor 15/19 (FGF15/19), an enterokine that regulates synthesis of hepatic bile acids (BA), has been proposed to influence fat metabolism. Without FGF15/19, mouse liver regeneration after partial hepatectomy (PH) is severely impaired. We studied the role of FGF15/19 in response to a high fat diet (HFD) and its regulation by saturated fatty acids. We developed a fusion molecule encompassing FGF19 and apolipoprotein A-I, termed Fibapo, and evaluated its pharmacological properties in fatty liver regeneration.Design Fgf15−/− mice were fed a HFD. Liver fat and the expression of fat metabolism and endoplasmic reticulum (ER) stress-related genes were measured. Influence of palmitic acid (PA) on FGF15/19 expression was determined in mice and in human liver cell lines. In vivo half-life and biological activity of Fibapo and FGF19 were compared. Hepatoprotective and proregenerative activities of Fibapo were evaluated in obese db/db mice undergoing PH.ResultsHepatosteatosis and ER stress were exacerbated in HFD-fed Fgf15−/− mice. Hepatic expression of Pparγ2 was elevated in Fgf15−/− mice, being reversed by FGF19 treatment. PA induced FGF15/19 expression in mouse ileum and human liver cells, and FGF19 protected from PA-mediated ER stress and cytotoxicity. Fibapo reduced liver BA and lipid accumulation, inhibited ER stress and showed enhanced half-life. Fibapo provided increased db/db mice survival and improved regeneration upon PH.ConclusionsFGF15/19 is essential for hepatic metabolic adaptation to dietary fat being a physiological regulator of Pparγ2 expression. Perioperative administration of Fibapo improves fatty liver regeneration.