Design of yeast-secreted albumin derivatives for human therapy: biological and antiviral properties of a serum albumin-CD4 genetic conjugate

Extension of the circulatory half-life of recombinant ecallantide via albumin fusion without loss of anti-kallikrein activity

Ecallantide comprises Kunitz Domain 1 of Tissue Factor Pathway Inhibitor, mutated at seven amino acid positions to inhibit plasma kallikrein (PK). It is used to treat acute hereditary angioedema (HAE). We appended hexahistidine tags to the N- or C-terminus of recombinant Ecallantide (rEcall) and expressed and purified the resulting proteins, with or without fusion to human serum albumin (HSA), using Pichia pastoris. The inhibitory constant (Ki) of rEcall-H6 or H6-rEcall for PK was not increased by albumin fusion. When 125I-labelled rEcall proteins were injected intravenously into mice, the area under the clearance curve (AUC) was significantly increased, 3.4- and 3.6-fold, for fusion proteins H6-rEcall-HSA and HSA-rEcall-H6 versus their unfused counterparts but remained 2- to 3-fold less than that of HSA-H6. The terminal half-life of H6-rEcall-HSA and HSA-H6 did not differ, although that of HSA-rEcall-H6 was significantly shorter than either other protein. Receptor Associated Protein (RAP), a Low-density lipoprotein Receptor-related Protein (LRP1) antagonist, competed H6-rEcall-HSA clearance more effectively than intravenous immunoglobulin (IVIg), a neonatal Fc receptor (FcRn) antagonist. HSA fusion decreases rEcall clearance in vivo, but LRP1-mediated clearance remains more important than FcRn-mediated recycling for rEcall fusion proteins. The properties of H6-rEcall-HSA warrant investigation in a murine model of HAE.

Genetically Encoded Self-Assembling Protein Nanoparticles for the Targeted Delivery In Vitro and In Vivo

Targeted nanoparticles of different origins are considered as new-generation diagnostic and therapeutic tools. However, there are no targeted drug formulations within the composition of nanoparticles approved by the FDA for use in the clinic, which is associated with the insufficient effectiveness of the developed candidates, the difficulties of their biotechnological production, and inadequate batch-to-batch reproducibility. Targeted protein self-assembling nanoparticles circumvent this problem since proteins are encoded in DNA and the final protein product is produced in only one possible way. We believe that the combination of the endless biomedical potential of protein carriers as nanoparticles and the standardized protein purification protocols will make significant progress in "magic bullet" creation possible, bringing modern biomedicine to a new level. In this review, we are focused on the currently existing platforms for targeted self-assembling protein nanoparticles based on transferrin, lactoferrin, casein, lumazine synthase, albumin, ferritin, and encapsulin proteins, as well as on proteins from magnetosomes and virus-like particles. The applications of these self-assembling proteins for targeted delivery in vitro and in vivo are thoroughly discussed, including bioimaging applications and different therapeutic approaches, such as chemotherapy, gene delivery, and photodynamic and photothermal therapy. A critical assessment of these protein platforms' efficacy in biomedicine is provided and possible problems associated with their further development are described.

Tandem fusion of albumin-binding domains promoted soluble expression and stability of recombinant trichosanthin in vitro and in vivo

Trichosanthin (TCS), as a type 1 ribosome-inactivating protein, has a very high cytoplasmic activity in vitro and can quickly kill cancer cells. However, it is easily filtered and cleared by the kidney, which results in the short half-life and severely limits its application. In this study, we constructed several recombinant proteins by fusing the albumin binding domain mutant ABD035(abbreviated as ABD) to the N- or C-terminus of TCS to endow the recombinant TCS fusion protein with a longer half-life property binding with endogenous human serum albumin (HSA) via ABD to effectively exert its anti-tumor activity in vivo. Pull down, Dynamic light scattering and ELISA assays all showed that TCS fused with two ABD sequences at the C-terminus of TCS, has stronger binding capacity to HSA in vitro than TCS with one ABD. In vivo studies in BALB/C mice were performed and the elimination half-life of TCS-ABD-ABD is about 15-fold longer compared to TCS and anti-tumor activity is about 30% higher than that of TCS alone in BALB/C mouse experiments. Moreover, we found that TCS with two ABDs in tandem have the highest soluble expression level, more than 5 times higher than that of TCS, and the yield of purified protein of TCS-ABD-ABD was as high as 68.9 mg/L culture solution, which was about 7-fold higher than that of TCS. Furthermore, MTT assay showed that the anti-tumor activity of TCS-ABD-ABD was significantly higher than TCS fused with only one ABD sequence, indicating that the repeated ABD sequences facilitated the biological activity of TCS. In this paper, the fusion of the albumin-binding domain in tandem with TCS can effectively improve its stability in vivo and also significantly increase its soluble expression, expanding the application of the albumin-binding domain in the high soluble expression and stability of protein drugs.

A Narrative Review of a Pulmonary Aerosolized Formulation or a Nasal Drop Using Sera Containing Neutralizing Antibodies Collected from COVID-19-Recovered Patients as a Probable Therapy for COVID-19

Coronavirus disease 2019 (COVID-19) emerged as a new contagion during December 2019, since which time it has triggered a rampant spike in fatality rates worldwide due to insufficient medical treatments and a lack of counteragents and prompted the World Health Organization to declare COVID-19 a public health emergency. It is, therefore, vital to accelerate the screening of new molecules or vaccines to win the battle against this pandemic. Experiences from previous epidemiological data on coronaviruses guide investigators in designing and exploring new compounds for a safe and cost-effective treatment. Several reports on the severe acute respiratory syndrome (SARS) epidemic indicate that severe acute respiratory syndrome coronavirus (SARS-CoV) and the novel COVID-19 use angiotensin-converting enzyme 2 (ACE2) as a receptor for binding to the host cell in the lung epithelia through the spike protein on their virion surface. ACE2 is a mono-carboxypeptidase best known for cleaving major peptides and substrates. Its degree in human airway epithelia positively correlates with coronavirus infection. The treatment approach can be the neutralization of the virus entering lung epithelial cells by using sera containing antibodies collected from COVID-19-recovered patients. Hence, we herein propose a pulmonary aerosolized formulation or a nasal drop using sera, which contain antibodies to prevent, treat, or immunize against COVID-19 infection.

The VP1u of Human Parvovirus B19: A Multifunctional Capsid Protein with Biotechnological Applications

The viral protein 1 unique region (VP1u) of human parvovirus B19 (B19V) is a multifunctional capsid protein with essential roles in virus tropism, uptake, and subcellular trafficking. These functions reside on hidden protein domains, which become accessible upon interaction with cell membrane receptors. A receptor-binding domain (RBD) in VP1u is responsible for the specific targeting and uptake of the virus exclusively into cells of the erythroid lineage in the bone marrow. A phospholipase A₂ domain promotes the endosomal escape of the incoming virus. The VP1u is also the immunodominant region of the capsid as it is the target of neutralizing antibodies. For all these reasons, the VP1u has raised great interest in antiviral research and vaccinology. Besides the essential functions in B19V infection, the remarkable erythroid specificity of the VP1u makes it a unique erythroid cell surface biomarker. Moreover, the demonstrated capacity of the VP1u to deliver diverse cargo specifically to cells around the proerythroblast differentiation stage, including erythroleukemic cells, offers novel therapeutic opportunities for erythroid-specific drug delivery. In this review, we focus on the multifunctional role of the VP1u in B19V infection and explore its potential in diagnostics and erythroid-specific therapeutics.

Protection against SIV in Rhesus Macaques Using Albumin and CD4-Based Vector-Mediated Gene Transfer

Antibody-like molecules were evaluated with potent simian immunodeficiency virus (SIV) neutralizing properties (immunoadhesins) that were delivered by a recombinant adeno-associated virus (rAAV) vector in the SIV-infected rhesus macaque model. When injected intramuscularly into the host, the vector directs in vivo production of the transgenes with antibody-like binding properties that lead to serum neutralizing activity against SIV. To extend the half-life of the immunoadhesins, rhesus cluster of differentiation 4 (CD4) and a single-chain antibody (4L6) were fused with albumin molecules, and these constructs were tested in our model of SIV infection. Antibody-based immunoadhesins provided high serum neutralizing titers against the original SIV strain. CD4-based immunoadhesins provided a wider spectrum of neutralization against different SIV strains in comparison to antibody-based therapeutics and had the potential to protect against high viral challenging doses. Although the albumin-antibody fusion immunoadhesin provided strong and prolonged protection of the immunized animals against SIV challenge, the albumin-CD4 fusion altered the specificity and decreased the overall protection effectiveness of the immunoadhesin in comparison to the antibody-based molecules. Albumin-based immunoadhesins increase in vivo longevity of the immune protection; however, they present challenges likely linked to the induction of anti-immunoadhesin antibodies.

Strategies for modifying drug residence time and ocular bioavailability to decrease treatment frequency for back of the eye diseases

INTRODUCTION

Treating posterior eye diseases has become a major area of focus for pharmaceutical and biotechnology companies. Current standard of care for treating posterior eye diseases relies on administration via intravitreal injection. Although effective, this is not without complications and there is great incentive to develop longer-acting therapeutics and/or sustained release delivery systems. Here, we present an overview of emerging technologies for delivery of biologics to the back of the eye.

AREAS COVERED

Posterior eye diseases, intravitreal injection, age-related macular degeneration, anti-VEGF, ocular pharmacokinetics, novel technologies to extend half-life, in vivo models, translation to the clinic, and hurdles to effective patient care.

EXPERT OPINION

Posterior eye diseases are a worldwide public health issue. Although anti-VEGF molecules represent a major advance for treating diseases involving choroidal neovascularization, frequent injection can be burdensome for patients and clinicians. There is a need for effective and patient-friendly treatments for posterior eye diseases. Many technologies that enable long-acting delivery to the back of the eye are being evaluated. However, successful development of novel therapies and delivery technologies is hampered by a multitude of factors, including patient education, translatability of in vitro/in vivo preclinical data to the clinic, and regulatory challenges associated with novel technologies.

HIV Entry and Its Inhibition by Bifunctional Antiviral Proteins

HIV entry is a highly specific and time-sensitive process that can be divided into receptor binding, coreceptor binding, and membrane fusion. Bifunctional antiviral proteins (bAVPs) exploit the multi-step nature of the HIV entry process by binding to two different extracellular targets. They are generated by expressing a fusion protein containing two entry inhibitors with a flexible linker. The resulting fusion proteins exhibit exceptional neutralization potency and broad cross-clade inhibition. In this review, we summarize the HIV entry process and provide an overview of the design, antiviral potency, and methods of delivery of bAVPs. Additionally, we discuss the advantages and limitations of bAVPs for HIV prevention and treatment.

Prediction and characterization of the stability enhancing effect of the Cherry-Tag™ in highly concentrated protein solutions by complex rheological measurements and MD simulations

Solution stability attributes are one of the key parameters within the production and launching phase of new biopharmaceuticals. Instabilities of active biological compounds can reduce the yield of biopharmaceutical productions, and may induce undesired reactions in patients, such as immunogenic rejections. Protein solution stability thus needs to be engineered and monitored throughout production and storage. In contrast to the gold standard of long-term storage experiments applied in industry, novel experimental and in silico molecular dynamics tools for predicting protein solution stability can be applied within several minutes or hours. Here, a rheological approach in combination with molecular dynamics simulations are presented, for determining and predicting long-term phase behavior of highly concentrated protein solutions. A diversity of liquid phase conditions, including salt type, ionic strength, pH and protein concentration are tested in a Glutathione-S-Transferase (GST) case study, in combination with the enzyme with and without solubility-enhancing Cherry-Tag™. The rheological characterization of GST and Cherry-GST solutions enabled a fast and efficient prediction of protein instabilities without the need of long-term protein phase diagrams. Finally, the strong solubility enhancing properties of the Cherry-Tag™ were revealed by investigating protein surface properties in MD simulations. The tag highly altered the overall surface charge and hydrophobicity of GST, making it less accessible to alteration by the chemical surrounding.

Efficient expression of stable recombinant human insulin-like growth factor-1 fusion with human serum albumin in Chinese hamster ovary cells

Insulin-like growth factor-1 (IGF-1) plays a crucial role in cell development, differentiation, and metabolism, and has been a potential therapeutic agent for many diseases. Chinese hamster ovary (CHO) cells are widely used for production of recombinant therapeutic proteins, but the expression level of IGF-1 in CHO cells is very low (1,500 µg/L) and the half-life of IGF-1 in blood circulation is only 4.5 min according to previous studies. Therefore, IGF-1 was fused to long-circulating serum protein human serum albumin (HSA) and expressed in CHO cells. After 8-day fed-batch culture, the expression level of HSA-IGF-1 reached 100 mg/L. The fusion protein HSA-IGF-1 was purified with a recovery of 35% using a two-step chromatographic procedure. According to bioactivity assay, the purified HSA-IGF-1 could stimulate the proliferation of NIH3T3 cells in a dose-dependent fashion and promote the cell-cycle progression. Besides this, HSA-IGF-1 could bind to IGF-1 receptor on cell membrane and activate the intracellular PI3K/AKT signaling pathway. Our study suggested that HSA fusion technology carried out in CHO cells not only provided bioactivity in HSA-IGF-1 for further research but also offered a beneficial strategy to produce other similar cytokines in CHO cells.

Safety and PK/PD correlation of TV-1106, a recombinant fused human albumin-growth hormone, following repeat dose administration to monkeys

PURPOSE

TV-1106 is a recombinant human albumin genetically fused to growth hormone which is intended to reduce the frequency of injections for GH therapy users. We report the safety, tolerability, pharmacokinetics and pharmacodynamics of repeated subcutaneous injections of TV-1106 in Cynomolgus monkeys.

METHOD

Cynomolgus monkeys received four weekly subcutaneous injections of 0, 5, 10 or 20mg/kg TV-1106 and were monitored for safety signals throughout the study. Serum levels of TV-1106 and insulin-like growth factor 1 (IGF-1) were assayed.

RESULTS

Treated animals showed no adverse effects or histopathological changes. TV-1106 serum concentrations showed sustained exposure to the drug. Exposure increased in a dose-dependent manner with peak concentrations at approximately 24h post-dosing and elimination half-lives in the range of 12 to 24h. IGF-1 serum concentrations were elevated throughout the entire study duration, indicative of the pharmacological response. There was a clear correlation between change in IGF-1 levels and dose or exposure to TV-1106.

CONCLUSIONS

The safety, pharmacokinetic and pharmacodynamic findings support the further development of TV-1106 as a once-weekly administered treatment for patients with GHD.

Fusion Proteins for Half-Life Extension of Biologics as a Strategy to Make Biobetters

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.

The role of albumin receptors in regulation of albumin homeostasis: Implications for drug delivery

Albumin is the most abundant protein in blood and acts as a molecular taxi for a plethora of small insoluble substances such as nutrients, hormones, metals and toxins. In addition, it binds a range of medical drugs. It has an unusually long serum half-life of almost 3weeks, and although the structure and function of albumin has been studied for decades, a biological explanation for the long half-life has been lacking. Now, recent research has unravelled that albumin-binding cellular receptors play key roles in the homeostatic regulation of albumin. Here, we review our current understanding of albumin homeostasis with a particular focus on the impact of the cellular receptors, namely the neonatal Fc receptor (FcRn) and the cubilin-megalin complex, and we discuss their importance on uses of albumin in drug delivery.

Identification of the peptide derived from S1 domain that inhibits type I and type II feline infectious peritonitis virus infection

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Feline infectious peritonitis (FIP) is a coronavirus-induced fatal disease in cats.

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We synthesized peptides derived from the S1 domain of the type I FIPV S protein.

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We investigated inhibitory effects of peptides on FIPV infection.

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5 peptides significantly inhibited type I FIPV.

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2 of 5 peptides significantly inhibited not only type I, but also type II FIPV.

Feline infectious peritonitis virus (FIPV) can cause a lethal disease in cats, feline infectious peritonitis (FIP). A therapeutic drug that is effective against FIP has not yet been developed. Peptides based on viral protein amino acid sequences have recently been attracting attention as new antiviral drugs. In the present study, we synthesized 30 overlapping peptides based on the amino acid sequence of the S1 domain of the type I FIPV strain KU-2 S protein, and investigated their inhibitory effects on FIPV infection. To evaluate the inhibitory effects on type I FIPV infection of these peptides, we investigated a method to increase the infection efficiency of poorly replicative type I FIPV. The efficiency of type I FIPV infection was increased by diluting the virus with medium containing a polycation. Of the 30 peptides, I-S1-8 (S461-S480), I-S1-9 (S471-S490), I-S1-10 (S481-S500), I-S1-16 (S541-S560), and I-S1-22 (S601-S620) significantly decreased the infectivity of FIPV strain KU-2 while I-S1-9 and I-S1-16 exhibited marked inhibitory effects on FIPV infection. The inhibitory effects on FIPV infection of these 2 peptides on other type I and type II FIPV strains, feline herpesvirus (FHV), and feline calicivirus (FCV) were also examined. These 2 peptides specifically inhibited type I and type II FIPV, but did FHV or FCV infection. In conclusion, the possibility of peptides derived from the S protein of type I FIPV strain KU-2 as anti-FIPV agents effective not only for type I, but also type II FIPV was demonstrated in vitro.

Co-opting biology to deliver drugs

The goal of drug delivery is to improve the safety and therapeutic efficacy of drugs. This review focuses on delivery platforms that are either derived from endogenous pathways, long-circulating biomolecules and cells or that piggyback onto long-circulating biomolecules and cells. The first class of such platforms is protein-based delivery systems--albumin, transferrin, and fusion to the Fc domain of antibodies--that have a long-circulation half-life and are designed to transport different molecules. The second class is lipid-based delivery systems-lipoproteins and exosomes-that are naturally occurring circulating lipid particles. The third class is cell-based delivery systems--erythrocytes, macrophages, and platelets--that have evolved, for reasons central to their function, to exhibit a long life-time in the body. The last class is small molecule-based delivery systems that include folic acid. This article reviews the biology of these systems, their application in drug delivery, and the promises and limitations of these endogenous systems for drug delivery.

Separation and isolation of fusion protein using a new native preparative PAGE device

A human serum albumin and Thymosin α1 (HSA-Tα1) fusion protein was designed and over-expressed in Pichia pastoris. To purify the fusion protein, a new native preparative electrophoresis system that involved a modified device with a sample receiving chamber, and an assay method with Coomassie Blue G-250 tracing the collection of the protein of interest. In this device, two gels were run in parallel: native vertical collecting polyacrylamide gel electrophoresis (PAGE) and native vertical tracing PAGE. Samples mixed with or without Coomassie Blue G-250 loading buffer were separately loaded to the two aforementioned gels, and the fractions were collected until the tracing protein band combined with dye reached 1 cm from the sample-receiving chamber at the bottom of the gel. Approximately nine fractions were collected at regular intervals of 15 min. HSA-Tα1 fusion protein with 95% relative homogeneity was harvested and manifested similar immunological activities as synthetic Tα1 after a single-step purification of this preparative PAGE. As a result, this system offers a new, rapid and simple method for the purification of the protein of interest.

Therapeutic antibodies for autoimmunity and inflammation

The development of therapeutic antibodies has evolved over the past decade into a mainstay of therapeutic options for patients with autoimmune and inflammatory diseases. Substantial advances in understanding the biology of human diseases have been made and tremendous benefit to patients has been gained with the first generation of therapeutic antibodies. The lessons learnt from these antibodies have provided the foundation for the discovery and development of future therapeutic antibodies. Here we review how key insights obtained from the development of therapeutic antibodies complemented by newer antibody engineering technologies are delivering a second generation of therapeutic antibodies with promise for greater clinical efficacy and safety.

Development, characterization, and evaluation of a fusion protein of a novel glucagon-like peptide-1 (GLP-1) analog and human serum albumin in Pichia pastoris

Glucagon-like peptide-1 (GLP-1) has considerable potential as a possible therapeutic agent for type-2 diabetes. Unfortunately, this glucoincretin is short lived due to degradation by dipeptidyl-peptidase IV and rapid clearance by renal filtration. In this study, we attempted to extend GLP-1 action through the attachment of a lysine residue at the N-terminal of GLP-1 (named KGLP-1), and to make a fusion protein with human serum albumin (HSA) in Pichia pastoris. The protein, designated KGLP-1/HSA, was purified by an immunomagnetic separation technique. High performance liquid chromatography (HPLC) showed that the purified protein had an overall purity of 92.0%, and matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) confirmed the expected molecular mass of 70,297.8 Da. Additionally, the N-terminal sequence of KGLP-1/HSA was confirmed by N-terminal sequencing. The stability and biological activity of KGLP-1/HSA were then evaluated in vitro and in vivo. The findings indicated that fusion KGLP-1/HSA preserved the action of native GLP-1, and the active duration was greatly prolonged.

Improved tumor targeting of anti-epidermal growth factor receptor Nanobodies through albumin binding: taking advantage of modular Nanobody technology

The approximately 15-kDa variable domains of camelid heavy-chain-only antibodies (called Nanobodies) can easily be formatted as multivalent or multispecific single-chain proteins. Because of fast excretion, however, they are less suitable for therapy of cancer. In this study, we aimed for improved tumor targeting of a bivalent anti-epidermal growth factor receptor (EGFR) Nanobody (alphaEGFR-alphaEGFR) by fusion to a Nanobody unit binding to albumin (alphaAlb). Biodistributions of alphaEGFR-alphaEGFR, alphaEGFR-alphaEGFR-alphaAlb ( approximately 50 kDa), alphaTNF-alphaTNF-alphaAlb (control, binding tumor necrosis factor-alpha), and the approximately 150-kDa anti-EGFR antibody cetuximab were compared in A431 xenograft-bearing mice. The proteins were radiolabeled with (177)Lu to facilitate quantification. Tumor uptake of (177)Lu-alphaEGFR-alphaEGFR decreased from 5.0 +/- 1.4 to 1.1 +/- 0.1 %ID/g between 6 and 72 h after injection. Due to its rapid blood clearance, tumor-to-blood ratios >80 were obtained within 6 h after injection. Blood clearance became dramatically slower and tumor uptake became significantly higher by introduction of alphaAlb. Blood levels of alphaEGFR-alphaEGFR-alphaAlb were 21.2 +/- 2.5, 11.9 +/- 0.6, and 4.0 +/- 1.4 and tumor levels were 19.4 +/- 5.5, 35.2 +/- 7.5, and 28.0 +/- 6.8 %ID/g at 6, 24, and 72 h after injection, respectively. Tumor uptake was at least as high as for cetuximab (15.5 +/- 3.9, 27.1 +/- 7.9, and 25.6 +/- 6.1 %ID/g) and significantly higher than for alphaTNF-alphaTNF-alphaAlb. alphaEGFR-alphaEGFR-alphaAlb showed faster and deeper tumor penetration than cetuximab. These data show that simple fusion of alphaEGFR and alphaAlb building blocks results in a bifunctional Nanobody format, which seems more favorable for therapy as far as pharmacokinetics and tumor deposition are concerned.

Circumventing the heterogeneity and instability of human serum albumin-interferon-alpha2b fusion protein by altering its orientation

Albuferon is a novel long-acting interferon resulted from the direct genetic fusion of human albumin and interferon-alpha2b (HSA-IFN-alpha2b). Albuferon, co-developed by Human Genome Sciences Inc. and Novartis, is currently in late stage development for the treatment of hepatitis C. It was unexpected that HSA-IFN-alpha2b secreted from Pichia pastoris migrated as doublets on non-reducing SDS-PAGE and was prone to form covalent aggregates in aqueous solution. The heterogeneity and instability of HSA-IFN-alpha2b lowered its recovery rate to about 10% and necessitated lyophilized formulation. Site-directed mutagenesis revealed that the heterogeneity and instability of HSA-IFN-alpha2b was caused by the incomplete disulfide bridge formation between Cys1 and Cys98 of IFN-alpha2b. To alleviate the structural perturbation of IFN-alpha2b by HSA, IFN-alpha2b-HSA fusion protein, in which IFN-alpha2b was located at the N-terminus, was created. IFN-alpha2b-HSA was shown to be homogeneous and stable at 37 degrees C for at least 10 days. The improved homogeneity and stability of IFN-alpha2b-HSA increased the recovery rate by 2.5-fold and made the development of stable solution formulation possible. In vitro antiviral assays showed that both fusion proteins retained the activity of IFN-alpha2b, and the EC(50) of HSA-IFN-alpha2b, and IFN-alpha2b-HSA was calculated to be 120+/-12.5, and 160+/-1 1.3ng/ml, respectively. The increased recovery rate and the possibility of solution formulation of IFN-alpha2b-HSA may compensate for its slightly decreased in vitro activity, and makes it to be a promising therapeutic agent that deserves further evaluation.

Radionuclide therapy of HER2-positive microxenografts using a 177Lu-labeled HER2-specific Affibody molecule

A radiolabeled anti-HER2 Affibody molecule (Z(HER2:342)) targets HER2-expressing xenografts with high selectivity and gives good imaging contrast. However, the small size (approximately 7 kDa) results in rapid glomerular filtration and high renal accumulation of radiometals, thus excluding targeted therapy. Here, we report that reversible binding to albumin efficiently reduces the renal excretion and uptake, enabling radiometal-based nuclide therapy. The dimeric Affibody molecule (Z(HER2:342))(2) was fused with an albumin-binding domain (ABD) conjugated with the isothiocyanate derivative of CHX-A''-DTPA and labeled with the low-energy beta-emitter (177)Lu. The obtained conjugate [CHX-A''-DTPA-ABD-(Z(HER2:342))(2)] had a dissociation constant of 18 pmol/L to HER2 and 8.2 and 31 nmol/L for human and murine albumin, respectively. The radiolabeled conjugate displayed specific binding to HER2-expressing cells and good cellular retention in vitro. In vivo, fusion with ABD enabled a 25-fold reduction of renal uptake in comparison with the nonfused dimer molecule (Z(HER2:342))(2). Furthermore, the biodistribution showed high and specific uptake of the conjugate in HER2-expressing tumors. Treatment of SKOV-3 microxenografts (high HER2 expression) with 17 or 22 MBq (177)Lu-CHX-A''-DTPA-ABD-(Z(HER2:342))(2) completely prevented formation of tumors, in contrast to mice given PBS or 22 MBq of a radiolabeled non-HER2-binding Affibody molecule. In LS174T xenografts (low HER2 expression), this treatment resulted in a small but significant increase of the survival time. Thus, fusion with ABD improved the in vivo biodistribution, and the results highlight (177)Lu-CHX-A''-DTPA-ABD-(Z(HER2:342))(2) as a candidate for treatment of disseminated tumors with a high level of HER2 expression.

Targeted and shielded adenovectors for cancer therapy

Conditionally replicative adenovirus (CRAd) vectors are novel vectors with utility as virotherapy agents for alternative cancer therapies. These vectors have already established a broad safety record in humans and overcome some of the limitations of non-replicative adenovirus (Ad) vectors. In addition, one potential problem with these vectors, attainment of tumor or tissue selectivity has widely been addressed. However, two confounding problems limiting efficacy of these drug candidates remains. The paucity of the native Ad receptor on tumor tissues, and host humoral response due to pre-existing titers of neutralizing antibodies against the vector itself in humans have been highlighted in the clinical context. The well-characterized CRAd, AdDelta24-RGD, is infectivity enhanced, thus overcoming the lack of coxsackievirus and adenovirus receptor (CAR), and this agent is already rapidly progressing towards clinical translation. However, the perceived host humoral response potentially will limit gains seen from the infectivity enhancement and therefore a strategy to blunt immunity against the vector is required. On the basis of this caveat a novel strategy, termed shielding, has been developed in which the genetic modification of a virion capsid protein would provide uniformly shielded Ad vectors. The identification of the pIX capsid protein as an ideal locale for genetic incorporation of shielding ligands to conceal the Ad vector from pre-existing neutralizing antibodies is a major progression in the development of shielded CRAds. Preliminary data utilizing an Ad vector with HSV-TK fused to the pIX protein indicates that a shield against neutralizing antibodies can be achieved. The utility of various proteins as shielding molecules is currently being addressed. The creation of AdDelta24S-RGD, an infectivity enhanced and shielded Ad vector will provide the next step in the development of clinically and commercially feasible CRAds that can be dosed multiple times for maximum effectiveness in the fight against cancers in humans.

Recombinant Human Serum Albumin Dimer has High Blood Circulation Activity and Low Vascular Permeability in Comparison with Native Human Serum Albumin

PURPOSE

Human serum albumin (HSA) is used clinically as an important plasma expander. Albumin infusion is not recommended for critically ill patients with hypovolemia, burns, or hypoalbuminemia because of the increased leakage of albumin into the extravascular spaces, thereby worsening edema. In the present study, we attempted to overcome this problem by producing a recombinant HSA (rHSA) dimer with decreased vascular permeability and an increased half-life.

METHODS

Two molecules of rHSA were genetically fused to produce a recombinant albumin dimer molecule. The pharmacokinetics and biodistribution of the recombinant proteins were evaluated in normal rats and carrageenin-induced paw edema mouse model.

RESULTS

The conformational properties of this rHSA dimer were similar to those for the native HSA (the HSA monomer), as evidenced by the Western blot and spectroscopic studies. The biological half-life and area under the plasma concentration-time curve of the rHSA dimer were approximately 1.5 times greater than those of the monomer. Dimerization has also caused a significant decrease in the total body clearance and distribution volume at the steady state of the native HSA. rHSA dimer accumulated to a lesser extent in the liver, skin, muscle, and fat, as compared with the native HSA. Up to 96 h, the vascular permeability of the rHSA dimer was less than that of the native HSA in paw edema mouse models. A prolonged plasma half-life of the rHSA dimer was also observed in the edema model rats.

CONCLUSIONS

rHSA dimer has a high retention rate in circulating blood and a lower vascular permeability than that of the native HSA.

A new format of single chain tri-specific antibody with diminished molecular size efficiently induces ovarian tumor cell killing

A combination of bi-specific antibodies (BsAb), anti-tumorxanti-CD3 and anti-tumorxanti-CD28, is effective in vitro and in vivo, whereas production of two kinds of bi-specific antibodies is labor intensive and administration is complicated. Accordingly, we previously developed a new model of single chain tri-specific antibody (scTsAb), sTRI, which linked both the CD3 and CD28 signals for T-cell activation in one molecule, and demonstrated its capacity for triggering T-cells to kill ovary tumor cells. To improve the pharmacokinetics further and decrease the immunogenicity of scTsAb, we have now generated a new format of scTsAb, TR3H, whose molecular size is smaller than sTRI. Here we describe the construction, purification and characterization of TR3H. TR3H scTsAb bound to effector cells and tumor target cells specifically and induced redirected lyses of ovary tumor cells through freshly isolated, unstimulated human peripheral blood lymphocytes (PBLs). This new format of scTsAb possesses properties that support its potential as a new tumor immunotherapeutic agent.

Enhancing exposure of protein therapeutics

Therapeutic proteins have made a major impact on medicine, with significant expansion in the past two decades. The medicinal attributes of these agents, particularly their efficacy and often their safety profile, make protein therapeutics attractive, despite the general necessity of invasive (parenteral) delivery. This perceived hurdle has been a primary component in limiting expansion of this class of drug therapies. Strategies that reduce the frequency of administration directly provide greater convenience to the patient, and potentially greater efficacy, that can yield a significant treatment advantage.:

Effects of Tween 20® and Tween 80® on the Stability of Albutropin During Agitation

The objectives of this work were to determine the effects of nonionic surfactants (Tween 20 and Tween 80) on agitation-induced aggregation of the recombinant fusion protein, Albutropintrade mark (human growth hormone genetically fused to human albumin), and to characterize the binding interactions between the surfactants and the protein. Knowing the binding stoichiometry would allow a rational choice of surfactant concentration to protect the protein from surface-induced aggregation. Fluorescence spectroscopy and isothermal titration calorimetry (ITC) were employed to study Albutropin surfactant binding. Albutropin was agitated at 25 +/- 2 degrees C to induce aggregation, and samples were taken during a 96-h incubation. Size-exclusion chromatography (SEC-HPLC) (HPLC, high-performance liquid chromatography) was used to detect and quantify the extent of protein aggregation. The effect of surfactants on the protein's free energy of unfolding was determined using guanidine HCl as a denaturant. Tween 20 and Tween 80 had saturable binding to Albutropin with a molar binding stoichiometry of 10:1 and 9:1 (surfactant:protein), respectively. Binding of the surfactants to Albutropin increased the free energy of unfolding by over 1 and 0.6 kcal/mol, respectively. In protein samples that were agitated in the absence of surfactant, soluble aggregates were detected within 24 h, and there was almost complete loss of monomer to soluble aggregates by the end of the 96-h experiment. At the molar binding stoichiometry, Tween 20 and Tween 80 prevented the formation of soluble aggregates, even though the concentrations of surfactants were well below their critical micelle concentrations (CMC). Tween 20 and Tween 80 protected Albutropin against agitation-induced aggregation, even at concentrations below the CMC. Equilibrium unfolding data indicate that Tween confer protection by increasing the free energy of unfolding of Albutropin.

Pharmacokinetics and in vitro and in vivo anti-tumor response of an interleukin-2-human serum albumin fusion protein in mice

PURPOSE

Albuleukin fusion protein is a recombinant human interleukin-2 (rIL-2) genetically fused to recombinant human serum albumin (rHSA). The pharmacokinetics and pharmacologic activity of Albuleukin were examined in mice to determine whether the fusion protein had the immunomodulatory and anti-tumor properties of rIL-2 as well as a prolonged serum half-life due to the rHSA.

METHODS

The effect of Albuleukin on lymphocyte proliferation, IL-2 receptor binding, and release of IFN-gamma from human NK cells were examined in vitro. For the pharmacokinetic analysis, Albuleukin and rIL-2 were administered intravenously (i.v.) and subcutaneously (s.c.) to BALB/c mice, both at a single dose of 500 microg/kg. The anti-tumor properties of Albuleukin were evaluated in a Renca tumor model in BALB/c mice and in a metastatic liver model of B16F10 melanoma in C57B1/6 mice. In the Renca tumor model, BALB/c mice were dosed intraperitoneally (i.p.) and s.c. with Albuleukin on days 12, 14, 16, 19, 21, and 23 and i.p. with rIL-2 daily for two periods of 5 days (days 10-14 and 17-21). In the B16 melanoma model, C57B1/6 mice were dosed s.c. with rIL-2 twice daily or Albuleukin every 48 h for 14 days.

RESULTS

In vitro, Albuleukin induced the proliferation of primary human and mouse T cells and B cells and primary human NK cells, competed with rIL-2 for binding to the IL-2 receptors, and induced the production of IFN-gamma from primary human NK cells. The s.c. bioavailability of Albuleukin was about 45% relative to the i.v. dose. Plasma half-life was prolonged and ranged from 6 to 8 h with Albuleukin, compared to 19-57 min with rIL-2. Total clearance of Albuleukin was about 50-fold slower than that of rIL-2 after i.v. dosing. In vivo, Albuleukin suppressed the growth of Renca tumors and induced a dense infiltration of CD4+ and CD8+ T cells. Both Albuleukin and rIL-2 significantly reduced the tumor burden in mice with hepatic B16F10 metastases. Albuleukin significantly reduced the incidence of residual macroscopic hepatic tumors, resulting in improved survival relative to controls and rIL-2.

CONCLUSION

Results from these studies suggest that the therapeutic efficacy of rIL-2 is improved in mice by prolonging its in vivo half-life through genetic fusion to albumin. Albuleukin, the fusion protein, had pronounced anti-tumor effects in Renca and hepatic melanoma tumor models without an increase in mortality. On the basis of its preclinical effects, Albuleukin was brought to the clinic to assess its therapeutic benefit in a variety of cancers.

Improvement of Fc–erythropoietin structure and pharmacokinetics by modification at a disulfide bond

Erythropoietin (Epo) is a cytokine that controls the production of red blood cells (RBCs). Epo acts continuously on RBC precursors to prevent apoptosis, so it is important to maintain high levels of Epo activity when treating anemic patients. We describe here modified human Epo [Epo(NDS)] with mutations His32Gly, Cys33Pro, Trp88Cys and Pro90Ala that result in the rearrangement of the disulfide bonding pattern from Cys29-Cys33 to Cys29-Cys88 and that, in the context of an Fc-Epo(NDS) fusion protein, lead to significantly improved properties. Fc-Epo was secreted from NS/0 myeloma cells as about 35% high molecular weight aggregates, was unstable upon removal of N-linked oligosaccharides and showed poor pharmacokinetics and little efficacy in mice. In contrast, a corresponding Fc-Epo(NDS) was secreted almost exclusively as a unit dimer, was relatively stable to removal of N-linked oligosaccharides, had much improved pharmacokinetic properties and had a significantly improved effect on RBC production. These results indicate that rearrangement of the disulfide bonding pattern in a therapeutic protein can have a significant effect on pharmacokinetics and, potentially, the dosing schedule of a protein drug.

Effects of genetic fusion of factor IX to albumin on in vivo clearance in mice and rabbits

Individuals with haemophilia B require replacement therapy with recombinant or plasma-derived coagulation factor IX (fIX). More benefit per injected dose might be obtained if fIX clearance could be slowed. The contribution of overall size to fIX clearance was explored, using genetic fusion to albumin. Recombinant murine fIX (MIX), and three proteins with C-terminal epitope tags were expressed in HEK 293 cells: tagged MIX (MIXT), tagged mouse serum albumin (MSAT) and MFUST, in which MIX and MSAT were fused in a single polypeptide chain. Proteins MFUST and MIXT were two- to threefold less active in clotting assays than MIX. In mice, the area under the clearance curve (AUC) was reduced for MFUST compared with MSAT or plasma-derived MSA (pd-MSA); the terminal catabolic half-life (t(0.5)) did not differ amongst the three proteins. Two minutes after injection, >40% of the injected MFUST was found in the liver, compared with <10% of either MSAT or pd-MSA. In rabbits, the AUC for MFUST was reduced compared to MIXT, MSAT, or pd-MSA, while the t(0.5) of the fusion protein fell between that of MIXT and MSAT or pd-MSA. Similar results were obtained with non-radioactive fused or non-fused recombinant human fIX in fIX knockout mice. The clearance behaviour of the fusion protein thus more closely resembled that of fIX than that of albumin despite a modest increase in terminal half-life, suggesting that fIX-specific interactions that are important in determining clearance were maintained in spite of the increased size of the fusion protein.

Improved production of heterologous proteins by a glucose repression-defective mutant of Kluyveromyces lactis

The secreted production of heterologous proteins in Kluyveromyces lactis was studied. A glucoamylase (GAA) from the yeast Arxula adeninivorans was used as a reporter protein for the study of the secretion efficiencies of several wild-type and mutant strains of K. lactis. The expression of the reporter protein was placed under the control of the strong promoter of the glyceraldehyde-3-phosphate dehydrogenase of Saccharomyces cerevisiae. Among the laboratory strains tested, strain JA6 was the best producer of GAA. Since this strain is known to be highly sensitive to glucose repression and since this is an undesired trait for biomass-oriented applications, we examined heterologous protein production by using glucose repression-defective mutants isolated from this strain. One of them, a mutant carrying a dgr151-1 mutation, showed a significantly improved capability of producing heterologous proteins such as GAA, human serum albumin, and human interleukin-1beta compared to the parent strain. dgr151-1 is an allele of RAG5, the gene encoding the only hexokinase present in K. lactis (a homologue of S. cerevisiae HXK2). The mutation in this strain was mapped to nucleotide position +527, resulting in a change from glycine to aspartic acid within the highly conserved kinase domain. Cells carrying the dgr151-1 allele also showed a reduction in N- and O-glycosylation. Therefore, the dgr151 strain may be a promising host for the production of heterologous proteins, especially when the hyperglycosylation of recombinant proteins must be avoided.

A covalently linked recombinant albumin dimer is more rapidly cleared in vivo than are wild-type and mutant C34A albumin

Mammalian albumins are abundant plasma proteins that exhibit a relatively slow terminal clearance. For this reason they have been fused to potentially therapeutic proteins with rapid terminal clearance to produce fusion proteins with more desirable clearance profiles. A disulfide-linked albumin dimer has been described, but its abundance and stability in plasma are uncertain. To determine whether an obligatory albumin dimer incapable of dissociation would clear less rapidly than monomeric albumin, we expressed 3 recombinant rabbit serum albumin (RSA) polypeptides: H6RSA, RSA modified by the addition of an N-terminal hexahistidinyl tag; H6RSA(C34A), H6RSA with a single cysteine (Cys) 34-to-alanine (Ala) substitution (C34A); and DiRSA, H6RSA(C34A) joined by way of its C-terminus to RSA(C34A) through an intervening hexaglycine spacer. The C34A mutation was introduced to eliminate the possibility of disulfide bond-mediated dimerization. We expressed the proteins with the use of the yeast Pichia pastoris and purified them using nickel-chelate, ion exchange, and gel-filtration chromatography. After radioiodination and injection into rabbits, H6RSA and H6RSA(C34A) exhibited indistinguishable terminal catabolic half-lives (4.9 +/- 0.7 and 4.8 +/- 0.5 days, mean +/- SD), whereas that of DiRSA was reduced to 3.0 +/- 0.3 days (p<.05). The three proteins circulated in intact form, and their distributions in liver, lung, kidney, heart, and spleen did not differ 24 hours after injection. Although more DiRSA than H6RSA(C34A) was present in urine, in both cases it was in acid-soluble form. Ethyl palmitate treatment reduced the relative acceleration of DiRSA clearance compared with that of H6RSA(C34A), suggesting a role for the reticuloendothelial system in the differential clearance of the larger protein. Our results suggest that an albumin fusion protein should include only a single copy of albumin; that if the fusion protein exceeds a certain size, it may not acquire the slow clearance profile of native albumin; and that albumin dimerization through Cys34 probably does not contribute substantially to albumin metabolism in vivo.

In vivo adenovirus-mediated delivery of a uPA/uPAR antagonist reduces retinal neovascularization in a mouse model of retinopathy

Diabetic retinopathy and retinopathy of prematurity are among the leading causes of vision impairment throughout the world. Both diseases are characterized by pathological angiogenesis, which severely impairs vision. Extracellular proteinases play important roles in endothelial cell migration during angiogenesis. Amino-terminal fragment (ATF) is an angiostatic molecule that targets the uPA/uPAR system and inhibits endothelial cell migration. The angiostatic effect of ATF has been demonstrated in models of cancer, but has never been assessed in pathological retinal neovascularization. Endostatin also has angiostatic effects on tumor growth and retinal neovascularization. We used an adenoviral vector carrying the murine ATF (AdATFHSA) or endostatin gene coupled to human serum albumin (HSA) (AdEndoHSA) to increase the half-life of the therapeutic protein in the circulation. We induced retinopathy by exposing 7-day-old mice to high levels of oxygen. They were intravitreally injected with the vectors. Local injection of AdATFHSA or AdEndoHSA reduced retinal neovascularization by 78.1 and 79.2%, respectively. Thus, the adenovirus-mediated delivery of ATFHSA or EndoHSA reduces retinal neovascularization in a mouse model of hypoxia-induced neovascularization.

Improving protein pharmacokinetics by genetic fusion to simple amino acid sequences

The role of primary amino acid sequences in protein pharmacokinetics, an issue of relevance in both basic knowledge and biotechnology, was addressed here using as a starting point two repetitive antigens from the hemoflagellate Trypanosoma cruzi that are known to stabilize their associated proteins in the bloodstream. A major drawback to their pharmacological application is that these repetitive sequences are highly immunogenic, being therefore the deletion of this characteristic desirable. Based on sequence homology and epitope mapping analyses, an artificial repetitive sequence (PSTAD) was engineered. This motif was tested by genetic fusion to the C terminus of both the trypanosomal trans-sialidase and the rat tyrosine aminotransferase and found to produce a 4.5-6-fold increase in the half-life of the associated proteins in blood while displaying significantly lower immunogenicity. Residues involved in the stabilizing properties of the novel peptide were mapped by a site-directed mutagenesis approach, allowing us to successfully identify another two motifs. Searching databases for sequences displaying some homology, embedded in proline frameworks and associated to shed virulence factors from unrelated microorganisms, resulted in the identification of four other protein extensions. Remarkably, three of them (from Streptococcus pneumoniae, Actinomyces viscosus, and Escherichia coli) revealed similar pharmacokinetic features, suggesting therefore an analogous evolutionarily acquired mechanism to ensure the biodistribution of their corresponding proteins. Our findings indicate that the insertion of defined motifs into a proline-rich framework constitutes a suitable alternative to construct a chimeric protein with extended half-life in blood.

Systemic administration of a recombinant adenovirus encoding a HSA-Angiostatin kringle 1-3 conjugate inhibits MDA-MB-231 tumor growth and metastasis in a transgenic model of spontaneous eye cancer

We previously reported that intratumoral injection of AdK3, a recombinant adenovirus encoding human angiostatin kringle (K) 1 to 3, inhibits tumor vascularization and tumor growth. To reduce the serum clearance of this factor, we constructed an adenovirus (AdK3-HSA) that carries a chimeric gene encoding a fusion protein between angiostatin K1-3 and human serum albumin (HSA). This conjugate inhibited endothelial cell proliferation as efficiently as K1-3. K3-HSA serum concentrations in immunodeficient mice systemically injected with AdK3-HSA were dramatically higher than in AdK3-injected mice. Furthermore, the growth of MDA-MB-231 tumors grafted into nude mice that had been injected intravenously with AdK3-HSA was inhibited by 79% (versus 17% with AdK3). In TRP-1/SV40 Tag transgenic mice, which spontaneously develop eye tumors with brain metastases, intravenous injections of AdK3-HSA in newborn mice blocked metastatic dissemination efficiently and significantly, and prolonged survival by 3 weeks. After 2 months, only 46% of AdK3-HSA-treated animals developed micrometastases, whereas 94% of the AdCO1-injected group displayed numerous macrometastases. Nevertheless, ocular tumor growth was not modified because of impaired diffusion of the conjugate in the eye compartment. Our results show that HSA genetic coupling is an efficient way to increase the pharmacokinetics of circulating angiogenic inhibitors and thus their antitumoral activity.

Albugranin, a recombinant human granulocyte colony stimulating factor (G-CSF) genetically fused to recombinant human albumin induces prolonged myelopoietic effects in mice and monkeys

PURPOSE

Albugranin fusion protein is recombinant granulocyte colony stimulating factor (rG-CSF) genetically fused at its N-terminus to the C-terminus of recombinant serum human albumin and is expected to have a relatively long half-life compared with rG-CSF alone. In this study, the pharmacodynamics and pharmacokinetics of Albugranin were evaluated in BDF1 mice and cynomolgus monkeys.

METHODS

Single doses of Albugranin (0.25-5 mg/kg) or Filgrastim (methionyl rG-CSF, 0.25, or 1.25 mg/kg) were administered subcutaneously (SC) to mice and multiple doses of Albugranin (25-100 microg/kg every 4 or 7 days) or Filgrastim (5 microg/kg daily) were administered SC for 14 days to monkeys for hematologic evaluation. For pharmacokinetics studies, mice were injected intravenously (IV) or SC with single doses of Albugranin (0.25-1.25 mg/kg) or Filgrastim (0.25 mg/ kg) and monkeys were injected SC with multiple doses of Albugranin (100-1,000 microg/kg once weekly for 5 weeks). Plasma levels of Albugranin and Filgrastim were measured by enzyme-linked immunosorbent assay.

RESULTS

In mice, administration of Albugranin effectively increased the number of peripheral granulocytes and mobilized hematopoietic progenitor cells for up to 5 days. The magnitude and duration of this effect were dose-dependent. In contrast, administration of Filgrastim resulted in a small increase in both cell types on day 1 only. Albugranin administered to cynomolgus monkeys caused an increase in peripheral neutrophils, with a less prominent increase in peripheral monocytes. Albugranin-induced neutrophilia peaked 24 h following each dose administration. Administration of Filgrastim daily in monkeys resulted in moderate increases in neutrophils that were maximal on days 8-12 during the course of treatment. Compared with Filgrastim, Albugranin had a longer terminal half-life (t(1/2,term)) and mean residence time (MRT), and slower clearance (CL/F) in mice. The t(1/2,term), MRT, and CL/F of Albugranin following SC administration to BDF1 mice were 5.6-5.7 h, 16.7-20.7 h, and 6.37-12.2 mL/h/kg, respectively, compared with 2.54 h, 4.9 h, and 164 mL/h/kg, respectively for Filgrastim. In cynomolgus monkeys, the corresponding values of t(1/2,term), MRT, and CL/F for Albugranin were 7.73-133 h, 19.4-27.3 h, and 7.90-27.5 mL/h/kg, respectively, for doses of 100-1000 microg/kg. An exposure-response relationship that could be empirically described with a simple Emax model with baseline was found between day 15 absolute neutrophil count and area under the curve following the first dose in cynomolgus monkeys.

CONCLUSION

The sustained activity of Albugranin in mice and monkeys demonstrated in these studies suggests that this agent could be given less frequently than Filgrastim to achieve similar therapeutic effects in patients.