A Liquid Formulation of a Long-acting Erythropoietin Conjugate

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.

Application of SPRA Technology for Delivery of Erythropoietin: Stability Evaluation of Conjugated Erythropoietin with Adamantane and in SPRA Inclusion Complex

Background

As a widely used therapeutic protein, recombinant human erythropoietin (rhEPO) is currently one of the most effective biopharmaceuticals on the market for the treatment of anemia in patients with chronic renal disease. Increasing in vivo rhEPO half-life and its bioactivity is a significant challenge. It was hypothesized that the application of self-assembly PEGylation retaining activity, named supramolecular (SPRA) technology, could prolong the protein half-life without a significant loss of bioactivity.

Objectives

This study aimed to assess the stability of rhEPO during synthetic reactions, including the conjugation with adamantane and the formation of the SPRA complex. To do this, the secondary structure of the protein was also evaluated.

Methods

FTIR, ATR-FTIR, Far-UV-CD, and SDS-PAGE methods were employed. Thermal stability studies of SPRA-rhEPO complex and rhEPO were investigated at 37°C for ten days using a nanodrop spectrophotometer.

Results

The secondary structure of lyophilized rhEPO, AD-rhEPO, and rhEPO (pH 8) was compared to rhEPO. Results showed that the secondary structure of the protein was unaffected by lyophilization, pH change, and the formation of covalent bonds in conjugation reaction. SPRA-rhEPO complex was also stable for seven days in phosphate buffer (pH 7.4) at 37°C.

Conclusions

It was concluded that the stability of rhEPO could increase by complexation using SPRA technology.

Single-and repeat-dose toxicity of HM10760A, a long-acting erythropoietin, in rats and monkeys

Anemia is a frequent complication of chronic kidney disease (CKD) that causes an increase in morbidity and mortality and accelerates the rate of disease progression. Treatment with recombinant human erythropoietin (rhEPO) is a major breakthrough in the therapy of renal anemia. HM10760A, a long-acting EPO, has been developed as a treatment for anemia in CKD patients. A series of preclinical toxicology studies, such as acute, 4 week repeat-dose, and 13 week repeat-dose, was completed to support the safety of human exposure to HM10760A for up to 13 weeks. The rodent and non-rodent species used in the pivotal preclinical general toxicity studies were rats and monkeys, respectively. A once-a-week or once-every-two-week i.v dosing regimen was applied for 4 week and 13 week repeat-dose toxicity studies, respectively, in consideration of the expected administration frequency in humans. Based on the 13 week repeat-dose toxicity studies, 2.61 μg/kg and 22.03 μg/kg can be considered as the NOAELs (no observed adverse effect levels) in rats and monkeys, respectively. Almost all observations recorded at the low- and mid-dose levels are typical pharmacological effects of EPO and not uniquely attributed HM10760A toxicity. To account for the differences between human being and animal physiologies, the safety of HM10760A needs to be further confirmed in future clinical studies.

The Minimal Effect of Linker Length for Fatty Acid Conjugation to a Small Protein on the Serum Half-Life Extension

Conjugation of serum albumin or one of its ligands (such as fatty acid) has been an effective strategy to prolong the serum half-lives of drugs via neonatal Fc receptor (FcRn)–mediated recycling of albumin. So far, fatty acid (FA) has been effective in prolonging the serum half-lives for therapeutic peptides and small proteins, but not for large therapeutic proteins. Very recently, it was reported a large protein conjugated to FA competes with the binding of FcRn with serum albumin, leading to limited serum half-life extension, because primary FA binding sites in serum albumin partially overlap with FcRn binding sites. In order to prevent such competition, longer linkers between FA and the large proteins were required. Herein, we hypothesized that small proteins do not cause substantial competition for FcRn binding to albumin, resulting in the extended serum half-life. Using a small protein (28 kDa), we investigated whether the intramolecular distance in FA-protein conjugate affects the FcRn binding with albumin and serum half-life using linkers with varying lengths. Unlike with the FA-conjugated large protein, all FA-conjugated small proteins with different linkers exhibited comparable the FcRn binding to albumin and extended serum half-life.