What Are Peptide Bioregulators? The Khavinson Short-Peptide Family Explained

Introduction

Peptide bioregulators are a family of research compounds developed at the St. Petersburg Institute of Bioregulation and Gerontology by Vladimir Khavinson and Vyacheslav Morozov from the early 1970s onward. The family has two tiers: organ-extract polypeptide complexes such as Thymalin and Epithalamin, and synthetic di-, tri- and tetrapeptides such as Epithalon (Ala-Glu-Asp-Gly) and Pinealon (Glu-Asp-Arg) that were modeled on those extracts. The term describes a research lineage, not a pharmacological receptor class.

This overview covers the family's classification and history, its naming variants, the mechanism proposed by the originating group, and the regulatory status of each member. Background on peptide chemistry is in the overview of what research peptides are.

Key facts

• The program's English-language reviews date its start to the early 1970s at the Military Medical Academy in Leningrad, with Morozov and Khavinson as the founding investigators [1, 2].
• Morozov and Khavinson used the term "cytomedins" for the extract complexes in a 1985 Russian-language paper, and "bioregulating therapy" appeared in a 1991 paper by Iakovlev, Khavinson, Morozov and Novikov [3, 4].
• Epithalon (also spelled epitalon) is the synthetic tetrapeptide Ala-Glu-Asp-Gly, molecular formula C14H22N4O9, molecular weight approximately 390 daltons; the FDA briefing document of 2026 records it as a synthetic analog of the pineal extract epithalamin [5, 6].
• Pinealon is the synthetic tripeptide Glu-Asp-Arg, molecular weight approximately 418 daltons, first characterized in an English-language journal in 2011 [7].
• Thymogen is the dipeptide Glu-Trp, reported by Anisimov, Khavinson and Morozov in 2000 to have been isolated by HPLC from the thymic extract Thymalin [8].
• Khavinson, Kopylov and colleagues reported in 2017 that the AEDG sequence was detected by mass spectrometry within the epithalamin polypeptide complex [9].
• No peptide bioregulator is approved by the FDA or the EMA; the FDA stated in May 2026 that epitalon is not a component of any FDA-approved drug and has no USP monograph [6].

What are peptide bioregulators?

Peptide bioregulators are the compounds of one research program, the Khavinson and Morozov lineage in St. Petersburg, and the label is defined by that origin rather than by shared structure or receptor. Anisimov and Khavinson's 2010 review described the program as beginning with polypeptide fractions extracted from bovine organs and later moving to defined synthetic sequences of two to four amino acids [1].

The family is therefore heterogeneous: Thymalin is a mixture of many polypeptides, while Vilon is a single dipeptide, Lys-Glu. Peptide bioregulators are not growth-hormone secretagogues, not incretin analogs, and not thymic hormones in the sense of thymosin alpha-1, although the thymic members overlap in origin with the molecules in the thymic peptides overview.

Where did the term come from?

The term traces to Russian-language publications of the 1980s and early 1990s. Morozov and Khavinson published on "cellular mediators (cytomedins)" in 1985, Iakovlev, Khavinson, Morozov and Novikov on "bioregulating therapy" in 1991, and Morozov and Khavinson on "cytomedines" again in 2000 [3, 4, 10].

English-language use followed: Anisimov, Loktionov, Khavinson and Morozov wrote on "low-molecular-weight factors of thymus and pineal gland" in 1989, and Morozov and Khavinson on natural and synthetic thymic peptides in 1997 [2, 11]. By 2010 the program's own reviews used "peptide bioregulation" as the umbrella term [1]. "Khavinson peptides" is an informal synonym used in later literature, including the 2025 review by Araj and colleagues [12].

What is the difference between organ-extract complexes and synthetic short peptides?

An organ-extract complex is a mixture of polypeptides isolated from animal tissue, whereas a synthetic short peptide is a single defined sequence made by chemical synthesis. Morozov and Khavinson's 1997 paper described Thymalin as a thymic extract and Thymogen as the synthetic dipeptide Glu-Trp developed from it [11]. Anisimov and Khavinson's 2010 review described the same extract-to-peptide transition for the pineal lineage, from Epithalamin to Epithalon [1].

The two tiers are different substances. The FDA's 2026 briefing document stated that the agency "considers epitalon and epithalamin as different substances," describing epithalamin as a polypeptide complex extracted from the pineal gland and epitalon as a tetrapeptide synthesized on the basis of that extract's amino-acid content [6].

For most members, the extract-to-peptide relationship was asserted before it was analytically demonstrated. For Epithalon, Khavinson, Kopylov and colleagues reported detecting AEDG within the epithalamin complex by mass spectrometry only in 2017 [9]; for Thymalin, Linkova and colleagues reported on the KE and EW dipeptides described as its components in 2023 [13].

Which peptides are classed as bioregulators?

The table lists the members that appear in PubMed-indexed literature, with the earliest report cited in this article and regulatory status as described in the cited sources.

Name	Type	Sequence	Source tissue (bovine)	Earliest report cited here	Regulatory status
Thymalin	Extract complex	Mixture	Thymus	1989 [2]; 1997 [11]	Registered pharmaceutical in Russia per the originating group [1, 11]; no FDA or EMA approval
Epithalamin	Extract complex	Mixture	Pineal gland	1989 [2]; 1994 [14]	Russian pharmaceutical per the program's reviews [1]; no FDA or EMA approval
Cortexin	Extract complex	Mixture	Cerebral cortex	1997 [15]; 2025 [16]	Registered pharmaceutical in Russia [1, 16]; no FDA or EMA approval
Retinalamin	Extract complex	Mixture	Retina	2021 [17]	Russian-market ophthalmic product per Russian-language literature [17]; no FDA or EMA approval
Prostatilen	Extract complex	Mixture	Prostate	2012 [18]	Russian-market product per Russian-language literature [18]; no FDA or EMA approval
Epithalon (epitalon)	Synthetic tetrapeptide	Ala-Glu-Asp-Gly (AEDG)	Modeled on Epithalamin	2001 [19]; 2003 [5]	Not FDA or EMA approved; FDA PCAC evaluation July 2026 [6]; RUO in the US
Pinealon	Synthetic tripeptide	Glu-Asp-Arg (EDR)	Pineal lineage	2011 [7]	Not FDA or EMA approved; RUO in the US
Vilon	Synthetic dipeptide	Lys-Glu (KE)	Modeled on Thymalin	2001 [19]; 2013 [20]	Not FDA or EMA approved
Thymogen	Synthetic dipeptide	Glu-Trp (EW)	Isolated from Thymalin	1997 [11]; 2000 [8]	Russian pharmaceutical per Morozov and Khavinson [11]; no FDA or EMA approval
Cortagen	Synthetic tetrapeptide	Ala-Glu-Asp-Pro (AEDP)	Modeled on Cortexin	2004 [21]	Not FDA or EMA approved
Livagen	Synthetic tetrapeptide	Lys-Glu-Asp-Ala (KEDA)	Liver lineage	2002 [22]	Not FDA or EMA approved
Vesugen	Synthetic tripeptide	Lys-Glu-Asp (KED)	Vascular lineage	2016 [23]	Not FDA or EMA approved

Two members of this family are cataloged by Sparta Labs as research-use-only reference materials: epithalon and pinealon. Their sequences, research records and regulatory positions are compared in the epithalon vs pinealon article.

Is epitalon the same as epithalon?

Yes: epitalon, epithalon and the rarer epithalone are transliterations of one Russian trade name for the tetrapeptide Ala-Glu-Asp-Gly. Both main spellings appear in PubMed-indexed titles from the same group. Khavinson, Bondarev and Butyugov used "Epithalon" in the Bulletin of Experimental Biology and Medicine in 2003, and Anisimov and colleagues used "Epitalon" in Biogerontology the same year [5, 24].

The FDA briefing document of 2026 used "epitalon" throughout and noted that it is a common name rather than a United States Adopted Name, adding that the agency had "encountered multiple salts, and derivatives, including different active moieties, sold commercially under the same common name" [6]. Epithalamin is not a spelling variant; it is the parent extract, a different substance [6]. The compound's timeline is in the epithalon history article.

What mechanism has been proposed for short peptide bioregulators?

The Khavinson group has proposed that short peptide bioregulators enter the cell nucleus and interact directly with DNA or chromatin proteins, altering gene expression; this remains a hypothesis advanced mainly by that group. Fedoreyeva, Kireev, Khavinson and Vanyushin reported in 2011 that fluorescence-labeled short peptides, including EDR, were detectable in the nuclei of HeLa cells and bound deoxyribooligonucleotides in vitro [25]. Khavinson, Lin'kova and Tarnovskaya summarized the position as "short peptides regulate gene expression" in 2016, and the group published a systematic review of its own gene-expression data in 2021 [26, 27].

Telomerase-related findings belong to this literature and are reported here only as attributed in vitro observations. Khavinson, Bondarev and Butyugov reported in 2003 that AEDG addition to telomerase-negative human fetal fibroblast cultures was associated with telomerase activity and telomere elongation [5]. In 2025, Al-Dulaimi, Thomas, Matta and Roberts, a group unconnected to the St. Petersburg institute, reported telomere-length changes in human cell lines exposed to epitalon and proposed that different pathways were involved in normal and cancer cell lines [28].

The replication gap is the central caveat. Most of the family's literature comes from one institute, much of it in Russian-language journals, and the docking-based mechanism has not been confirmed by structural biology; the 2025 review by Araj and colleagues identified the clinical-trial gap as the main open question [12]. Compound-level detail is in the epithalon mechanism of action and pinealon mechanism of action articles.

What is the regulatory status of peptide bioregulators?

No peptide bioregulator, extract or synthetic, is approved by the FDA or the European Medicines Agency. The originating group's reviews describe several organ-extract complexes, including Thymalin and Cortexin, as pharmaceuticals registered in Russia [1, 11, 16]. A Russian registration confers no status in the United States or the European Union.

In the United States, epitalon was one of seven substances considered by the FDA Pharmacy Compounding Advisory Committee on July 23 and 24, 2026, for possible inclusion on the 503A Bulks List [29]. The FDA briefing document stated that there is no USP or NF monograph for epitalon (free base) or epitalon acetate, that neither is a component of an FDA-approved drug, and that the evaluation criteria "weigh against" listing them [6]. Pinealon has no equivalent listing in Western-accessible regulatory records.

Research-grade Epithalon and Pinealon sold by chemical suppliers are laboratory reference materials, not pharmaceutical products, and are strictly for research use only.

How is the identity of a synthetic peptide bioregulator confirmed?

Identity is confirmed by mass spectrometry, which detects the intact peptide at its expected mass (approximately 390 daltons for Epithalon, 418 for Pinealon), by tandem mass spectrometry or amino-acid analysis for residue order, and by reversed-phase HPLC for purity. The FDA briefing document shows why batch-level data matter: no USP monograph exists for epitalon, and inconsistent naming makes it hard to know which substance a reference standard refers to [6].

Summary

Peptide bioregulators are the compounds of one research lineage, the Khavinson and Morozov program in St. Petersburg: organ-extract complexes such as Thymalin, Epithalamin and Cortexin, and synthetic short peptides derived from them such as Epithalon, Pinealon, Vilon and Thymogen. Epitalon and epithalon are the same tetrapeptide, Ala-Glu-Asp-Gly; epithalamin is the parent extract. The originating group has proposed a direct peptide-DNA mechanism, with limited independent replication. No member of the family is approved by the FDA or the EMA, and the synthetic peptides are research-use-only materials in the United States.

References

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