Preparation and characterization of a potent, long-lasting recombinant human serum albumin-interferon-alpha2b fusion protein expressed in Pichia pastoris

Challenges and Recent Advances in Erythropoietin Stability

Erythropoietin (EPO) is a pivotal hormone that regulates red blood cell production, predominantly synthesized by the kidneys and also produced by the liver. Since the introduction of recombinant human EPO (rh-EPO) in 1989 through recombinant DNA technology, the therapeutic landscape for anemia has been improved. rh-EPO's market expansion has been substantial, with its application extending across various conditions such as chronic kidney disease, cancer-related anemia, and other disorders. Despite its success, significant concerns remain regarding the stability of EPO, which is critical for preserving its biological activity and ensuring therapeutic efficacy under diverse environmental conditions. Instability issues, including degradation and loss of biological activity, challenge both drug development and treatment outcomes. Factors contributing to EPO instability include temperature fluctuations, light exposure, and interactions with other substances. To overcome these challenges, pharmaceutical research has focused on developing innovative strategies such as stabilizing agents, advanced formulation techniques, and optimized storage conditions. This review article explores the multifaceted aspects of EPO stability, examining the impact of instability on clinical efficacy and drug development. It also provides a comprehensive review of current stabilization strategies, including the use of excipients, lyophilization, and novel delivery systems.

Engineering a New IFN-ApoA-I Fusion Protein with Low Toxicity and Prolonged Action

Recombinant human interferon alpha-2b (rIFN) is widely used in antiviral and anticancer immunotherapy. However, the high efficiency of interferon therapy is accompanied by a number of side effects; this problem requires the design of a new class of interferon molecules with reduced cytotoxicity. In this work, IFN was modified via genetic engineering methods by merging it with the blood plasma protein apolipoprotein A-I in order to reduce acute toxicity and improve the pharmacokinetics of IFN. The chimeric protein was obtained via biosynthesis in the yeast P. pastoris. The yield of ryIFN-ApoA-I protein when cultivated on a shaker in flasks was 30 mg/L; protein purification was carried out using reverse-phase chromatography to a purity of 95-97%. The chimeric protein demonstrated complete preservation of the biological activity of IFN in the model of vesicular stomatitis virus and SARS-CoV-2. In addition, the chimeric form had reduced cytotoxicity towards Vero cells and increased cell viability under viral load conditions compared with commercial IFN-a2b preparations. Analysis of the pharmacokinetic profile of ryIFN-ApoA-I after a single subcutaneous injection in mice showed a 1.8-fold increased half-life of the chimeric protein compared with ryIFN.

Human serum albumin binders: A piggyback ride for long-acting therapeutics

Human serum albumin (HSA) is the most abundant protein in the blood and has desirable properties as a drug carrier. One of the most promising ways to exploit HSA as a carrier is to append an albumin-binding moiety (ABM) to a drug for in situ HSA binding upon administration. Nature- and library-derived ABMs vary in size, affinity, and epitope, differentially improving the pharmacokinetics of an appended drug. In this review, we evaluate the current state of knowledge regarding various aspects of ABMs and the unique advantages of ABM-mediated drug delivery. Furthermore, we discuss how ABMs can be specifically modulated to maximize potential benefits in clinical development.

Recent and future perspectives on engineering interferons and other cytokines as therapeutics

As crucial mediators and regulators of our immune system, cytokines are involved in a broad range of biological processes and are implicated in various disease pathologies. The field of cytokine therapeutics has gained much momentum from the maturation of conventional protein engineering methodologies such as structure-based designs and/or directed evolution, which is further aided by the advent of in silico protein designs and characterization. Just within the past 5 years, there has been an explosion of proof-of-concept, preclinical, and clinical studies that utilize an armory of protein engineering methods to develop cytokine-based drugs. Here, we highlight the key engineering strategies undertaken by recent studies that aim to improve the pharmacodynamic and pharmacokinetic profile of interferons and other cytokines as therapeutics.

Self-fused concatenation of interferon with enhanced bioactivity, pharmacokinetics and antitumor efficacy

We report an easy but universal protein modification approach, self-fused concatenation (SEC), to biosynthesize a set of interferon (IFN) concatemers with improved in vitro bioactivity, in vivo pharmacokinetics and therapeutic efficacy over the monomeric IFN, and the results can be positively enhanced by the concatenated number of self-fused proteins.

Enhancement of bioactivity, thermal stability and tumor retention by self-fused concatenation of green fluorescent protein

The widespread application of protein and peptide therapeutics is hampered by their poor stability, strong immunogenicity and short half-life. However, the existing protein modification technologies require the introduction of exogenous macromolecules, resulting in inevitable immunogenicity and decreased bioactivity. Herein, we reported an easy but universal protein modification approach, self-fused concatenation (SEC), to enhance the in vitro thermal stability and in vivo tumor retention of proteins. In this proof of concept study, we successfully obtained a set of green fluorescence protein (GFP) concatemers, monomer (GFP 1), dimer (GFP 2) and trimer (GFP 3) of GFP, and systematically studied the effects of SEC on the biological activity and stability of GFP. Notably, GFP concatemers displayed remarkable improvement in in vitro bioactivity and thermal stability over the monomeric GFP. In a murine tumor model, GFP 2 and GFP 3 exhibited significantly prolonged duration, with increases of 220- and 381-fold relative to GFP 1 in tumor retention 4 h after administration. Furthermore, the biological activity, thermal stability and tumor retention can be enhanced by the concatenated number of self-fused proteins. These findings demonstrate that SEC may be a promising alternative to design advanced protein and peptide therapeutics with enhanced pharmaceutic profiles.

Albumin Fusion at the N-Terminus or C-Terminus of HM-3 Leads to Improved Pharmacokinetics and Bioactivities

HM-3, an integrin antagonist, exhibits anti-tumor biological responses and therefore has potential as a therapeutic polypeptide. However, the clinical applications of HM-3 are limited by its short half-life. In this study, we genetically fused human serum albumin (HSA) to the N or C-terminus of HM-3 to improve HM-3 pharmacokinetics. HM-3/HSA proteins were successfully expressed in Pichia pastoris and displayed improved pharmacokinetic properties and stability. Among them, the half-life of HM-3-HSA was longer than HSA-HM-3. In vitro, the IC₅₀ values of HSA-HM-3 and HM-3-HSA were 0.38 ± 0.14 μM and 0.25 ± 0.08 μM in B16F10 cells, respectively. In vivo, the inhibition rates of B16F10 tumor growth were 36% (HSA-HM-3) and 56% (HM-3-HSA), respectively, indicating antitumor activity of HM-3-HSA was higher than HSA-HM-3. In conclusion, these results suggested that the HM-3/HSA fusion protein might be potential candidate HM-3 agent for treatment of melanoma and when HSA was fused at the C-terminus of HM-3, the fusion protein had a higher stability and activity.

Interferon-Based Biopharmaceuticals: Overview on the Production, Purification, and Formulation

The advent of biopharmaceuticals in modern medicine brought enormous benefits to the treatment of numerous human diseases and improved the well-being of many people worldwide. First introduced in the market in the early 1980s, the number of approved biopharmaceutical products has been steadily increasing, with therapeutic proteins, antibodies, and their derivatives accounting for most of the generated revenues. The success of pharmaceutical biotechnology is closely linked with remarkable developments in DNA recombinant technology, which has enabled the production of proteins with high specificity. Among promising biopharmaceuticals are interferons, first described by Isaacs and Lindenmann in 1957 and approved for clinical use in humans nearly thirty years later. Interferons are secreted autocrine and paracrine proteins, which by regulating several biochemical pathways have a spectrum of clinical effectiveness against viral infections, malignant diseases, and multiple sclerosis. Given their relevance and sustained market share, this review provides an overview on the evolution of interferon manufacture, comprising their production, purification, and formulation stages. Remarkable developments achieved in the last decades are herein discussed in three main sections: (i) an upstream stage, including genetically engineered genes, vectors, and hosts, and optimization of culture conditions (culture media, induction temperature, type and concentration of inducer, induction regimens, and scale); (ii) a downstream stage, focusing on single- and multiple-step chromatography, and emerging alternatives (e.g., aqueous two-phase systems); and (iii) formulation and delivery, providing an overview of improved bioactivities and extended half-lives and targeted delivery to the site of action. This review ends with an outlook and foreseeable prospects for underdeveloped aspects of biopharma research involving human interferons.

One-month zero-order sustained release and tumor eradication after a single subcutaneous injection of interferon alpha fused with a body-temperature-responsive polypeptide

Upon a single subcutaneous injection, IFN-ELP in situ forms a depot, leading to one-month sustained release and dramatically enhanced tumor therapy.

Preventing the N-terminal processing of human interferon α-2b and its chimeric derivatives expressed in Escherichia coli

We have previously shown that human interferon α-2b (IFN) produced in Escherichia coli (E. coli) is heterogeneous at the N-terminal, with three major species (Ahsan et al., 2014). These are: (a) the direct translation product of the gene retaining the N-terminal methionine, (b) a species from which the methionyl residue has been removed by E. coli methionyl aminopeptidase to give the native interferon α-2b and (c) in which the N-terminal Cys residue of the latter contains an acetyl group. In this paper we overcome this heterogeneity, using engineered interferon derivatives with phenylalanine residue directly downstream of the N-terminal methionine (Met-Phe-IFN). This modification not only prevented the removal of the N-terminal methionine by E. coli methionyl aminopeptidase but also the subsequent N-acetylation. Critically, Met-Phe-IFN had enhanced activity in a biological assay. N-terminal stabilization was also achieved by fusing human cytochrome b₅ at the N-terminal of interferon (b₅-IFN-chimera). In this case also, the protein was more active than a reciprocal chimera with cytochrome b₅ at the C-terminal of interferon (Met-IFN-b₅-chimera). This latter protein also had a heterogeneous N-terminal but addition of phenylalanine following Met, (Met-Phe-IFN-b₅-chimera), resolved this problem and gave enhanced biological activity.

Enhancing Pharmacokinetics, Tumor Accumulation, and Antitumor Efficacy by Elastin-Like Polypeptide Fusion of Interferon Alpha

Genetic fusion of elastin-like polypeptide (ELP) to the C-terminus of interferon alpha (IFN) generates a well-defined IFN-ELP fusion protein with high yield and well-retained bioactivity. The fusion protein significantly enhances pharmacokinetics, tumor accumulation, and antitumor efficacy of interferon alpha in a murine cancer model.

Enhanced Anti-Tumor (Anti-Proliferation) Activity of Recombinant Human Interleukin-29 (IL-29) Mutants Using Site-Directed Mutagenesis Method

Interferon (IFN)-λ, also known as IL-28A, IL-28B, or IL-29, is a new type III IFN, which shares many functional characteristics with type I IFN (α/β). Currently, IFN-α is used in the treatment of certain forms of cancer with severe adverse effects. Some researches had stated that IFN-λs induced a similar but restricted growth inhibition of tumor cells relative to IFN-α; moreover, mutations of IFN-λs could strongly impact its biological properties. In this study, three hIL-29 mutants (K33R, R35K, and K33R/R35K) were generated by site-directed mutagenesis and efficiently expressed in Pichia pastoris GS115, which have considerable abilities to inhibit the growth of BEL-7402, HCT-8, and SGC-7901 tumor cells in vitro. The results showed that these mutants (K33R, R35K, and K33R/R35K) exhibited a significantly enhanced anti-proliferation activity against these tumor cells, compared with native hIL-29 in vitro. Further assay in vitro indicated that superior to K33R and R35K, K33R/R35K had a significant increase in anti-tumor activity compared with IFN-α2b, which suggested that the K33R/R35K could make improvement for the effectiveness of native hIL-29 in clinic and could be used as a potentially powerful candidate for cancer immunotherapy.

Engineering of a Pichia pastoris expression system for high-level secretion of HSA/GH fusion protein

Human serum albumin (HSA) and human growth hormone (hGH) fusion protein [HSA/GH] is a promising long-acting form of GH to treat GH deficiency. This study attempted to engineer a P. pastoris strain for high-level production of HSA/GH to be used in basic research and clinical application. Strains contained two, three, and seven copies of HSA/GH gene were screened by selecting against Zeocin resistance. The results revealed that introducing two to three copies of HSA/GH gene was sufficient to give a significant increase in secretion level, compared with one copy of HSA/GH gene. No significant differences were observed between two to three copies and seven copies. Co-expression with either one copy of exogenous ERO1 or PDI in a strain carrying multicopies of HSA/GH gene led to varying degrees of increase in HSA/GH secretion. The effect of introducing multicopies of PDI was similar to that of one copy of PDI, but introducing excess copies of ERO1 reduced HSA/GH secretion. Simultaneous co-expression with PDI and ERO1 was less effect than either PDI co-expression or ERO1 co-expression. A strain showing higher secretion level was successfully applied to large-scale fermentation with the productivity of 3-4 g/l.

IL-1Ra and its delivery strategies: inserting the association in perspective

Interleukin-1 receptor antagonist (IL-1Ra) is a naturally occurring anti-inflammatory antagonist of interleukin-1 family of pro-inflammatory cytokines. The broad spectrum anti-inflammatory effects of IL-1Ra have been investigated against various auto-immune diseases such as diabetes mellitus, rheumatoid arthritis. Despite of its outstanding broad spectrum anti-inflammatory effects, IL-1Ra has short biological half-life (4-6 h) and to cope with this problem, up till now, many delivery strategies have been applied either to extend the half-life and/or prolong the steady-state sustained release of IL-1Ra from its target site. Here in our present paper, we have provided an overview of all approaches attempted to prolong the duration of therapeutic effects of IL-1Ra either by fusing IL-1Ra using fusion protein technology to extend the half-life and/or development of new dosage forms using various biodegradable polymers to prolong its steady-state sustained release at the site of administration. These approaches have been characterized by their intended impact on either in vitro release characteristics and/or pharmacokinetic and pharmacodynamic parameters of IL-1Ra. We have also compared these delivery strategies with each other on the basis of bioactivity of IL-1Ra after fusion with fusion protein partner and/or encapsulation with biodegradable polymer.

Albumin fusion of interleukin-28B: production and characterization of its biological activities and protein stability

The cytokine interleukin-28B (IL-28B) has potential antiviral properties and regulatory roles in adaptive cellular immunity. A genome-wide association study identified a single nucleotide polymorphism near the IL-28B gene that strongly predicts response to hepatitis C treatment with interferon and ribavirin. In this study, we produced human serum albumin (HSA) fused to interleukin-28B (HSA-IL28B) in an attempt to determine the effects of albumin fusion on anti-Hepatitis C virus (HCV) activity and protein stability. HSA-IL28B was expressed at high levels in the yeast expression system we used and was easily purified. The biological activities of IL-28B were only retained when HSA was fused at the N-terminus. Compared with the native IL-28B, HSA-IL28B showed improved protein stability. HSA-IL28B inhibited HCV infection through the membrane receptors IL28R1 and IL10R2. Additionally, we demonstrated that HSA-IL28B was able to induce interferon-stimulated genes, phosphorylate intracellular STAT1, and act in restricted cell types. Our findings highlight the potential clinical applications of the fusion protein during virus infection and for immune regulation.

The effect of gene copy number and co-expression of chaperone on production of albumin fusion proteins in Pichia pastoris

Interleukin-1 receptor antagonist (IL1ra) is known to treat a number of diseases such as rheumatoid arthritis and type 2 diabetes. However, the biological half-life of IL1ra is very short due to its rapid renal clearance. Our present study aimed to increase the biological half-life of IL1ra through fusion with human serum albumin (HSA), and then augmented expression of the IL1ra and HSA fusion protein (IH) in Pichia pastoris strain by increasing IH gene copy number or was co-expressed with chaperone. By comparing clones containing varying copy numbers of IH fusion gene, it was observed that higher levels of secretory IH fusion protein was produced in strain with higher IH gene copy number. In addition, IH protein yield was further improved after being co-expressed with protein disulfide isomerase (PDI). Conversely, it was significantly decreased (i.e., secretory IH in the culture medium) by co-expression of immunoglobulin binding protein. We have also discussed whether the multi-copy strain and co-expressed of PDI could enhance the levels of other secretory albumin fusion protein (e.g., HSA and human growth hormone fusion protein). Interestingly, the level of this fusion protein was apparently also increased by these approaches. In conclusion, our results have demonstrated that increasing copy number and co-expression of PDI may raise yield of albumin fusion protein in P. pastoris, which might probably contribute to the industry for the development of proteinous drugs.

Characterization of a long-acting recombinant human serum albumin-atrial natriuretic factor (ANF) expressed in Pichia pastoris

The cardiac hormone atrial natriuretic factor (ANF) combines pharmacological properties of drugs used to treat essential hypertension (EH), congestive heart failure (CHF) and acute myocardial infarction (AMI). Treatment of CHF or AMI patients with an intravenous (iv) infusion of the circulating form of ANF (ANF(99-126)) produces significant clinical improvement. The short half-life (5 min) and peptide nature of ANF impose logistic restrictions for chronic administration. To increase its half-life, we fused ANF and human serum albumin (HSA) mini-genes by recombination in Pichia pastoris. The activity of three configurations of the fusion protein was tested in vitro and in vivo. The fusion protein that comprised of C-terminus HSA connected to N-terminus ANF via a hexaglycine linker showed the best outcome; it increased cGMP production in vitro. In vivo an iv bolus of HSA-ANF into mice increased significantly plasma cGMP levels and lowered blood pressure (BP) for up to 6 h hence successfully extended ANF half-life in plasma while retaining its biological activity. HSA-ANF represents the basis for development in the chronic therapeutic use of ANF.

Modulation of immunogenicity and immunoprotection of mucosal vaccine against coxsackievirus B3 by optimizing the coadministration mode of lymphotactin adjuvant

Induction of potent mucosal immune response is a goal of current vaccine strategies against mucus-infectious pathogens such as Coxsackievirus B3 type (CVB3). We previously showed that administration of lymphotactin (LTN) as an adjuvant could enhance the specific immune responses against a mucosal gene vaccine, chitosan-pVP1, against CVB3. To optimize the coadministration mode of the mucosal adjuvant, we compared the mucosal immune responses induced by chitosan-DNA vaccine with different combinations of the target VP1 antigen gene and the adjuvant LTN gene. The two genes were either cloned in separate vectors or coexpressed as a fusion or bicistron protein in the same vector before encapsulation in chitosan nanoparticles. Four doses of various adjuvant-combined chitosan-DNA were intranasally administrated to mice before challenge with CVB3. The results indicated that chitosan-formulated pVP1-LTN fusion plasmid exhibited very weak improvement of CVB3-specific immune responses. Although the bicistronic coexpression of LTN with VP1 was expected to be powerful, this combination had enhanced effects on serum IgG and systemic T cell immune responses, but not on mucosal T cell immunity. Coimmunization with VP1 and LTN as separate chitosan-DNA formulation remarkably enhanced antibody and T cell immune responses both in systemic and mucosal immune compartments, leading to the most desirable preventive effect on viral myocarditis. Taken together, how the adjuvant is combined with the target antigen has a strong influence on the mucosal immune responses induced by mucosal DNA vaccines.

Strategies to maximize expression of rightly processed human interferon alpha2b in Pichia pastoris

The human interferon alpha 2b (IFN alpha2b) belongs to the interferon family of cytokines that exerts many biological functions like inhibition of virus multiplication, repression of tumour growth and other immunological functions. Herein, a synthetic gene coding for human IFN alpha2b was cloned and integrated into a methylotropic yeast-Pichiapastoris. The recombinant human IFN alpha2b protein (approximately 19kDa) could be successfully expressed in Pichiapastoris to a level of nearly 300mg/L with nearly 93% recovery on purification using a single anion exchange chromatography step. A novel media component dimethyl sulphoxide (DMSO) was found to aid in expression of rightly processed IFN alpha2b form with dramatic reduction in the expression of a 20kDa IFN isoform contaminant frequently observed by other workers. The identity of the 20kDa isoform was confirmed by N terminal sequencing which showed extra eleven amino acids at the N terminal portion of the IFN molecule obtained due to incorrect processing by the host KEX2 protease. The purified IFN alpha2b (19kDa) preparation was confirmed by N terminal sequencing, and characterized by MALDI-TOF and Agilent 2100 Bioanalyzer. The bioassay of the recombinant protein gave a specific activity of >2x10(8)IU/mg.

Engineering a pharmacologically superior form of granulocyte-colony-stimulating factor by fusion with gelatin-like-protein polymer

The plasma half-life of therapeutic proteins is a critical factor in many clinical applications. Therefore, new strategies to prolong plasma half-life of long-acting peptides and protein drugs are in high demand. Here, we designed an artificial gelatin-like protein (GLK) and fused this hydrophilic GLK polymer to granulocyte-colony-stimulating factor (G-CSF) to generate a chimeric GLK/G-CSF fusion protein. The genetically engineered recombinant GLK/G-CSF (rGLK/G-CSF) fusion protein was purified from Pichia pastoris. In vitro studies demonstrated that rGLK/G-CSF possessed an enlarged hydrodynamic radius, improved thermal stability and retained full bioactivity compared to unfused G-CSF. Following a single subcutaneous administration to rats, the rGLK/G-CSF fusion protein displayed a slower plasma clearance rate and stimulated greater and longer lasting increases in circulating white blood cells than G-CSF. Our findings indicate that fusion with this artificial, hydrophilic, GLK polymer provides many advantages in the construction of a potent hematopoietic factor with extended plasma half-life. This approach could be easily applied to other therapeutic proteins and have important clinical applications.

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.

Preparation and characterization of a novel exendin-4 human serum albumin fusion protein expressed in Pichia pastoris

A novel recombinant exendin-4 human serum albumin fusion protein (rEx-4/HSA) expressed in Pichia pastoris was prepared and characterized. Ex-4 is a 39-amino acid peptide isolated from the salivary gland of the lizard Heloderma suspectum and is thought to be a novel therapeutic agent for type 2 diabetes. But to gain a continued effect, the peptide has to be injected twice a day owing to its short plasma half-life (t(1/2) = 2.4 h). To extend the half-life of Ex-4 molecule in vivo, we designed a genetically engineered Ex-4/HSA fusion protein. Between Ex-4 and HSA, a peptide linker GGGGS was inserted and the fusion protein was expressed in methylotrophic yeast P. pastoris with native HSA secretion signal sequence. The recombinant protein was secreted correctly and was obtained with high purity (typically > 98%) by a three-step purification procedure. cAMP assay demonstrated that the fusion protein had a bioactivity similar to Ex-4 for interaction with GLP-1 receptors in vitro. Results from oral glucose tolerance test indicated that rEx-4/HSA could effectively improve glucose tolerance in diabetic db/db mice. Pharmacokinetics studies in cynomologus monkeys also showed that rEx-4/HSA had a much longer plasma half-life. Therefore, rEx-4/HSA fusion protein could potentially be used as a new recombinant biodrug for type 2 diabetes therapy.

Expression, purification, and characterization of recombinant human serum albumin fusion protein with two human glucagon-like peptide-1 mutants in Pichia pastoris

Glucagon-like peptide-1 (GLP-1) is a 30-residue peptide hormone secreted by intestinal L-cells in response to nutrient ingestion. In the present study, overlapping PCR technology was employed to construct two GLP-1 mutants (GLP-1(A2G))2 and human albumin (HSA) genes in vitro without linker. The spliced gene, (GLP-1(A2G))2-HSA, was over expressed under the control of promoter AOX1 and Mat alpha signal peptide in Pichia pastoris. SDS-PAGE and Western blotting were applied to assay the recombinant fusion protein in the culture broth. The results demonstrated that the recombinant (GLP-1(A2G))2-HSA concentration in the broth could reach a level of 245.0 mg/L and the expressed fusion protein was capable of cross-reacting with anti-human GLP-1 and anti-human albumin antibody. The recombinant (GLP-1(A2G))2-HSA protein was purified by ultrafiltration, columns of Q-sepharose fast flow and Superdex 75 size-exclusion. The recombinant (GLP-1(A2G))2-HSA protein obtained could lower in vivo glucose concentration in blood and stimulate in vitro islet cell proliferation. In mouse model, the fusion protein was detectable in plasma even 308 h after a single subcutaneous dose of 1.25 mg/kg. The result showed that the terminal biological half-time of the protein was about 54.2 h which is 650-fold longer than that of GLP-1. The pharmacokinetic analysis of the protein suggests its promising application in clinical medicine.