Polyethylene Glycol in PEGylated Interferon

Interferons (IFNs) are a group of naturally occurring cytokines, originally named for their ability to interfere with viral replication in infected cells. Nowadays, IFNs are used in the treatment of various diseases such as viral infections, multiple malignancies, multiple sclerosis (MS), bacterial infections in chronic granulomatous diseases, rheumatoid arthritis, and more. As research into their mechanisms of action deepens, more clinical applications for IFNs are expected to be approved.

What is Interferon?

Interferons are a class of low molecular weight proteins, primarily glycoproteins, with diverse biological activities. They do not directly kill or inhibit viruses; instead, they work by inducing antiviral proteins in cells through surface receptor interactions, which ultimately suppress viral replication. Interferons are one of the most important immune factors in the fight against viral infections. IFNs were first discovered in 1957 by British virologist Alick Isaacs and Swiss researcher Jean Lindenmann while studying the interference phenomenon of influenza virus replication in chick embryos. They observed that virus-infected cells produced a factor that could act on other cells to interfere with viral replication, thus naming it interferon.

Fig. 1. Interferon structure.

IFNs are mainly produced by monocytes and macrophages, which regulate cell growth, differentiation, and immune response. With advancements in pharmaceutical technology, interferons have become increasingly common in treatments, ranging from flu, hepatitis, and chickenpox to now being applied in cancer and leukemia therapies. Recombinant DNA technology allows the production of recombinant human interferons, such as recombinant human IFN-α-2a, IFN-α-1b, IFN-α-2b, IFN-β, and IFN-γ.

Type 1 vs Type 2 vs Type 3 Interferon

Interferons are categorized into three types (Type I, II, and III) based on their specific receptors. Each type induces a distinct immune response. Additionally, interferon-mediated signaling promotes the upregulation of major histocompatibility complex (MHC) molecules (MHC I and MHC II) and activates downstream signaling cascades, establishing antiviral defense mechanisms. Interferons are used clinically for treating viral infections, such as hepatitis B and C. However, some viruses have evolved mechanisms to resist interferon activity.

Type I Interferons

Type I interferons include IFN-α, IFN-β, IFN-τ, and IFN-ω, which are encoded by chromosome 9 in humans. IFN-α, produced primarily by leukocytes, and IFN-β, produced by fibroblasts, are widely known. When a cell is infected with a virus, it generates viral substances not found in uninfected cells. These substances trigger the production of Type I interferons. Although interferon cannot save the infected cell itself, it alerts neighboring cells to prepare antiviral defenses, often leading to cell sacrifice through T-cell activation. Clinically, IFN-α is the most common form used for antiviral treatments.

Type II Interferon

Type II interferon, also known as IFN-γ, is produced primarily by activated T cells and natural killer (NK) cells. It is a key regulator of immune responses, enhancing the activation of other immune cells and promoting their functions. IFN-γ enhances the phagocytic activity of macrophages, stimulates B lymphocytes, and modulates T cells and antigen-presenting cells, making it crucial in regulating immune responses.

Type III Interferon

Type III interferons include IFN-λ, with subtypes IFN-λ1 (also known as IL-28a), IFN-λ2 (IL-28b), IFN-λ3 (IL-29), and IFN-λ4. These are primarily produced by epithelial cells in non-hematopoietic tissues, and their exact mechanism of production remains under study. Some research suggests that herpes simplex virus (HSV) patterns are recognized by endosomal toll-like receptors (TLR3 and TLR9) and cytoplasmic melanoma differentiation-associated protein 5 (MDA5), leading to the activation of transcription factors such as NF-κB, IRF3, and IRF7, which then stimulate the transcription of IFN-λ genes.

What is Interferon Used For?

In clinical settings, IFNs are available as recombinant formulations. IFN-α and IFN-γ are used to treat viral infections and certain malignancies, while IFN-β is used in the treatment of multiple sclerosis (MS). IFN-γ can also treat bacterial infections associated with chronic granulomatous disease and rheumatoid arthritis.

Antiviral Activity

Interferons' antiviral properties are well-recognized. Upon viral induction, the JAK-STAT signaling pathway is activated, leading to the upregulation of interferon-stimulated genes (ISGs) that help combat the virus. However, some viruses have developed mechanisms to evade interferon's immune regulation. For instance, reports on HIV or SIV infections have shown varying results in IFN-α subtype gene expression depending on tissue type, cells, or stimulation.

Antitumor Activity

Interferons play a role in the three stages of tumor immunoediting: tumor elimination, dormancy, and escape. IFNs help induce apoptosis or slow tumor progression by upregulating tumor suppressor factors like IRF1 and promoting the expression of pro-apoptotic molecules such as Bak while downregulating BCL2. These factors trigger cytochrome c release, activating caspases and leading to tumor cell apoptosis. IFNs are currently being studied in the treatment of leukemia, renal cell carcinoma, malignant melanoma, and hemangiomas.

Multiple Sclerosis

Multiple sclerosis (MS) is a progressive demyelinating neurodegenerative disease characterized by relapsing-remitting episodes. Intramuscular injections of IFN-β reduce MS relapse rates due to their immunomodulatory effects. Combining IFN-β with natalizumab, a recombinant monoclonal antibody, enhances treatment efficacy, reducing MS relapse rates by approximately 50% compared to IFN-β alone.

PEGylated Interferon

PEGylated interferon (PEG-IFN-α) is a long-acting formulation where polyethylene glycol (PEG), a non-ionic polymer, is covalently attached to IFN-α. This modification extends serum half-life, reduces immunogenicity, and lowers susceptibility to proteolysis, allowing dosing frequency to be reduced from three times per week to once a week, improving patient compliance. PEG also reduces direct interaction between interferon and immune cells, minimizing adverse effects. PEG-IFN-α is mainly used to treat hepatitis B and C. There are two main types of PEGylated interferon:

• PEG-IFN-α2a: Features a larger PEG molecule that provides better protection for interferon, leading to a more stable drug concentration and longer half-life, with distribution mainly in the blood and liver.
• PEG-IFN-α2b: Features a smaller PEG molecule that allows for broader tissue distribution, including muscles and adipose tissue.

Fig. 2. PEGylated Interferon (CNS Drugs. 2012, 26(3): 205-14).

Polyethylene Glycols from BOC Sciences

BOC Sciences offers high-quality PEG derivatives for PEGylated interferon applications, supporting improved drug efficacy and extended circulation time. With a comprehensive portfolio of PEG reagents, we offer customized solutions to meet specific PEGylation needs, ensuring precise control over molecular weight, branching, and functionalization. Our advanced synthetic capabilities enable the production of PEG derivatives that meet stringent pharmaceutical grade standards, making them ideal for modifying interferons to improve their stability and bioavailability.

Advantages of PEGylated Interferon

PEGylation, the process of attaching PEG molecules to interferon, has successfully addressed many of these issues, enhancing its pharmacological properties and expanding its therapeutic potential.

Extended Half-Life

One of the most notable benefits of PEGylating interferon is the significant extension of its half-life in the bloodstream. PEG is a non-ionic, hydrophilic polymer that forms a protective barrier around the interferon molecule, reducing its renal clearance and degradation by proteolytic enzymes. This results in sustained blood levels of the drug, allowing for less frequent dosing. For example, PEGylated interferon can be administered once weekly, compared to three times a week for non-PEGylated interferon, improving patient compliance and convenience.

Reduced Immunogenicity

PEGylation reduces the immunogenicity of interferon by shielding it from direct interactions with immune cells. This protective effect diminishes the likelihood of the immune system recognizing interferon as a foreign protein, thereby reducing the formation of neutralizing antibodies. The reduction in immunogenicity helps minimize adverse immune reactions and allows for prolonged use of PEG-IFN without loss of efficacy due to antibody development.

Enhanced Stability and Distribution

PEGylated interferon exhibits greater stability, resisting thermal and enzymatic degradation. It maintains its bioactivity for a longer duration, allowing it to act continuously over extended periods. The distribution profile of PEG-IFN is also improved. Depending on the molecular weight of the PEG used, the drug can either concentrate more effectively in targeted tissues (such as the liver, in the case of hepatitis treatment) or achieve wider distribution across different tissues, including muscles and adipose tissue. This tunable distribution enhances its therapeutic efficiency.

Lower Dosing Frequency and Improved Patient Adherence

With the extended half-life and reduced immunogenicity, PEGylated interferon can be administered less frequently. This not only reduces the burden of frequent injections but also improves overall patient adherence to treatment regimens. The convenience of once-weekly administration is a significant advantage over non-PEGylated interferon, which requires multiple weekly doses.

What is PEGylated Interferon Used For?

PEGylated interferon is widely used in the treatment of chronic hepatitis B and hepatitis C, as well as cancer and autoimmune diseases. In the treatment of hepatitis, pegylated interferon combined with antiviral drugs can enhance virus clearance and reduce virus replication. Compared with traditional interferon, pegylated interferon can improve the virological response rate and reduce the recurrence rate. The half-life is prolonged and can be administered once a week, thereby improving patient compliance in long-term treatment. In oncology, pegylated interferon has shown good prospects in the treatment of melanoma, renal cell carcinoma and leukemia by enhancing the immune response to tumors. Its improved stability and reduced immunogenicity make it suitable for long-term cancer treatment. In addition, pegylated interferon-β (PEG-IFN-β) is used to treat multiple sclerosis (MS). It regulates the immune response to reduce the frequency of MS recurrence and slow the progression of the disease. Prolonged half-life also helps reduce injection frequency, which is beneficial for lifelong treatment. Overall, pegylation improves the efficacy of interferon, making it a powerful tool for the treatment of viral and autoimmune diseases as well as oncology, providing better patient compliance and treatment outcomes.

BOC Sciences provides comprehensive high-quality PEG derivatives for pegylated interferons to enhance their pharmacological properties, such as stability, solubility, and half-life. Our advanced PEGylation service provides customized solutions for modifying interferon proteins to improve therapeutic effects while reducing immunogenicity and administration frequency. With expertise in the production of various PEG derivatives (including linear PEG and branched PEG), BOC Sciences ensures precise molecular customization to meet specific project requirements. Our strong ability in PEG synthesis and binding supports a wide range of applications from viral therapy to autoimmune therapy, helping to improve drug performance and patient outcomes.

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Reference

1. Kieseier, B.C. Calabresi, P.A. PEGylation of interferon-β-1a: a promising strategy in multiple sclerosis. CNS Drugs. 2012, 26(3): 205-14.