ARA-290 vs Testagen

Non-hematopoietic EPO analogue; activates innate repair receptor (IRR/EPOR/CD131 complex) without erythropoietic effects; promotes tissue repair and nerve healing

ARA 290 (cibinetide) is a synthetic 11-amino-acid peptide derived from the helix B region of erythropoietin (EPO), engineered to activate the innate repair receptor (IRR) — a tissue-protective heteroreceptor complex comprising the EPO receptor and the β-common receptor (CD131) — without engaging the classical erythropoietic EpoR homodimer, thereby separating EPO's tissue-protective signaling from its hematopoietic effects. By selectively engaging the IRR rather than the erythropoietic receptor, cibinetide activates anti-inflammatory and anti-apoptotic intracellular pathways in neurons, endothelium, and other metabolically active tissues without causing erythrocytosis, hypertension, or thrombosis, making it a candidate for neuropathy and inflammatory tissue injury contexts. Randomized, double-blind Phase 2 clinical trials have demonstrated that cibinetide improves metabolic control and neuropathic symptom scores in patients with type 2 diabetes, and a separate study demonstrated improved corneal nerve fiber abundance in patients with sarcoidosis-associated small fiber neuropathy — providing human proof-of-concept for both diabetic and inflammatory peripheral neuropathy applications. Cibinetide (ARA 290) is an investigational compound that has not received FDA approval for any indication; Phase 2 data supports further investigation in peripheral neuropathies, but no Phase 3 completion or regulatory filing has occurred as of 2025.

Khavinson-class tetrapeptide bioregulator derived from testicular tissue; proposed to modulate gene expression in Leydig and Sertoli cells; investigated for age-related testicular function decline

Testagen is a synthetic tetrapeptide and Khavinson-class peptide bioregulator derived from testicular tissue, investigated for regulatory effects on testicular cell function and age-related reproductive hormone decline. Like other Khavinson-class bioregulators, testagen is proposed to act as a short regulatory peptide that modulates gene expression in target organ cells — in this case, testicular Leydig cells responsible for testosterone synthesis and Sertoli cells that support spermatogenesis. The Khavinson bioregulator model posits that short peptides derived from specific tissues preferentially interact with chromatin regulatory elements in homologous tissues, restoring expression of age-downregulated genes and partially reversing organ-level functional decline associated with aging. Research interest in testagen centers on age-associated decline in testicular function, including reduced Leydig cell activity and the associated decline in testosterone biosynthesis that characterizes male aging. Preclinical studies have examined testagen-class peptides for effects on reproductive hormone levels, testicular histomorphology, and markers of gonadal function in aged animal models. Testagen is part of the broader Khavinson bioregulator research program that has also characterized thymalin (thymus), cortagen (cardiovascular/neural), cartalax (cartilage), and pinealon (pineal gland) as organ-specific regulatory peptides. Testagen benefits investigated in preclinical research include support for testosterone biosynthesis pathways, maintenance of Leydig cell populations, and preservation of testicular tissue architecture with aging. These effects are proposed to occur through epigenetic regulatory mechanisms rather than direct hormonal supplementation, distinguishing bioregulator peptides from exogenous testosterone replacement. Testagen is classified as a research compound with no regulatory approval in any jurisdiction. No human clinical trials have established safety or efficacy for testicular support, testosterone augmentation, or reproductive function endpoints. Research protocols have examined testagen primarily via subcutaneous injection, with oral delivery also studied in bioregulator research contexts.