EPI-X4; a new frontier with potential to treat cancer and inflammatory diseases

Author

Micah Sagini

CXCR4 is a chemokine receptor that is associated with the development of cancer and other inflammatory disorders. The endogenous inhibitor of CXCR4 known as EPI-X4, is a recently discovered peptide from human serum albumin that inhibits C-X-C chemokine receptor type 4 (CXCR4).

Chemokines are small signaling proteins (8–12 kDa) that interact with G-protein-coupled receptors to regulate physiological processes in the body. One of the most studied chemokines is CXCR4, which is widely distributed in various human tissues. Under normal circumstances, CXCR4 plays a pivotal role in guiding cell movement, controlling cell proliferation and survival, and regulating stem cell homing to the bone marrow. However, when it is overexpressed in cells, it can influence cancer development and inflammation. CXCR4 accomplishes these roles by interacting with its natural chemokine ligand known as CXCL12 (SDF-1) [1]. Some of the cancers affected by overexpression of CXCR4 include pancreatic, breast, colorectal, lung, ovarian, and brain cancers, as well as leukemia and lymphoma. Researchers are, therefore, trying to develop therapies that block the interaction of CXCL12 with CXCR4 [2-4].

One of the most studied compounds that inhibit the CXCL12-CXCR4 cascade is plerixafor (AMD3100), also known as Mozobil. To date, plerixafor is the only CXCR4 antagonist approved by the U.S. Food and Drug Administration. Initially, plerixafor was being developed as a therapy for HIV. However, the unexpected finding that it increased leukocytes in the peripheral blood shifted its application focus because its efficacy against HIV was not strong enough for other strains. It is currently approved for mobilizing stem cells from the bone marrow to the peripheral blood, where they are collected for transplantation therapy [5-7].

Apart from plerixafor, a number of CXCR4 inhibitors are being developed. Some of these inhibitors include Mavorixafor, Ulocuplumab (a monoclonal antibody), Burixafor (a small molecule), Peptide R, and EPI-X4, just to mention a few.

The hemofiltrate as a source of therapeutic peptides

Hemofiltration is a blood purification process used for patients with chronic renal failure. During hemofiltration, blood is pumped from the patient through a special filter to remove toxins and waste products before being infused back into the patient. This process differs slightly from hemodialysis, which involves the movement of molecules through diffusion across a concentration gradient. Human hemofiltrate has been used as a valuable source of peptides for therapeutic and diagnostic purposes [8]. For example, a study by Schulz-Knappe et al. in the late 1990s highlighted the significance of human filtrate in peptide research. By isolating peptides through affinity chromatography, they established a comprehensive plasma peptide bank [9]. This study laid the groundwork for the discovery of EPI-X4, a 16-amino acid peptide that inhibits CXCR4.

Human serum albumin is the most abundant protein in human plasma, with a half-life of 19 days, and serves various physiological functions in the body, including being a source of important peptides. Peptides derived from HSA can have antimicrobial properties, modulate the immune system by inducing cytokine release, act as antioxidants by scavenging reactive oxygen species, reduce inflammation, and inhibit cancer cell proliferation [10].

The discovery of EPI-X4 was later identified as a fragment of HSA, generated by the two enzymes: cathepsin D and E. Further experiments revealed that EPI-X4, similar to plerixafor, inhibits the CXCL12–CXCR4 pathway and mobilizes stem cells from the bone marrow to the peripheral blood. With this discovery, attempts have been made to improve its half-life (17 min) and efficacy. Therefore, newer versions of EPI-X4 (containing 12 or fewer amino acids) have been synthesized after sequence optimization [11].

EPI-X4 shows promise in treating cancer and inflammatory diseases

In a recent study evaluating EPI-X4 as a therapy for pancreatic cancer and lymphoma, the peptide demonstrated significant efficacy leading to tumor reduction. In the pancreatic cancer model, three peptides (a, f, & k) inhibited tumor growth by over 99%. A similar effect was observed in the lymphoma model, where three peptide derivatives (b, n, & p) inhibited tumor growth by 75%. These promising results confirmed that EPI-X4 can disrupt the CXCL12–CXCR4 pathway, which is associated with cancer development. Given that pancreatic cancer is a lethal malignancy with limited treatment options, the effectiveness of EPI-X4 offers hope for patients with pancreatic cancer, and those with other malignancies that rely on this pathway for metastasis [11].

In addition to cancer, EPI-X4 and its optimized derivatives, such as EPI-X4 JM#21, have been assessed in animal models of asthma and dermatitis. In atopic dermatitis (skin inflammation), the topical application of optimized EPI-X4 derivatives effectively prevented skin inflammation in mouse models, showcasing its efficacy for localized skin conditions [12, 13].

A similar observation was made in allergic asthma (airway inflammation), where a topical or intranasal administration of EPI-X4 derivatives in a mouse model inhibited the infiltration of inflammatory cells, particularly eosinophils, into the lungs, thereby reducing airway hyper-responsiveness. In these models, EPI-X4 is believed to have interfered with the binding of CXCL12 to the CXCR4 receptor, preventing the migration of inflammatory immune cells like eosinophils to the skin and lungs, consequently reducing inflammation and disease severity.

Therefore, optimized versions of EPI-X4, such as JM#21, with enhanced activity and improved anti-inflammatory effects, are being developed for increased stability and prolonged half-life.

Conclusion

The CXCL12–CXCR4 pathway is a promising drug target for cancer and inflammatory diseases. EPI-X4, a peptide derived from human serum albumin, has emerged as a promising therapy as it inhibits the CXCL12–CXCR4 pathway, blocking downstream signaling. Preclinical studies show that it is well tolerated in animal models with minimal side effects. This novel peptide holds promise for treating various diseases such as pancreatic cancer, lymphoma, asthma, and atopic dermatitis, all of which exhibit abnormal expression of the CXCL12–CXCR4 pathway.

References

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11.       Sagini, M.N., et al., EPI-X4, a CXCR4 antagonist inhibits tumor growth in pancreatic cancer and lymphoma models. Peptides, 2024. 175: p. 171111.

12.       Harms, M., et al., An optimized derivative of an endogenous CXCR4 antagonist prevents atopic dermatitis and airway inflammation. Acta Pharm Sin B, 2021. 11(9): p. 2694-2708.

13.       Sokkar, P., et al., Computational modeling and experimental validation of the EPI-X4/CXCR4 complex allows rational design of small peptide antagonists. Commun Biol, 2021. 4(1): p. 1113.

Assessed and Endorsed by the MedReport Medical Review Board