Compound Profile
Selank: From an Antibody Fragment to Anxiety Research
Published: August 24, 2026
TL;DR
Selank has an unusual starting point. Its parent sequence, tuftsin, is a four-residue fragment of the heavy chain of immunoglobulin G, an antibody molecule. Selank keeps tuftsin's Thr-Lys-Pro-Arg sequence and adds Pro-Gly-Pro, producing a seven-residue peptide that has been examined primarily in anxiety research. One 2008 randomized study compared participants receiving Selank with a medazepam group. Another study from that year examined immune signaling, including interleukin-6 gene expression and the balance of Th1 and Th2 cytokines.
Curo's research-peptide catalog includes a Selank research-material page. Researchers can match a lot with its record in the certificate of analysis database. All catalog materials are governed by Curo's Research Use Only policy. Selank has no FDA approval for any indication, and a ClinicalTrials.gov intervention search returns no registered Selank studies.
A tuftsin analogue
Tuftsin is not a brain peptide. It is a naturally occurring tetrapeptide with the sequence Thr-Lys-Pro-Arg, derived from the heavy chain of immunoglobulin G. Selank extends that immune-derived sequence at the C-terminus with Pro-Gly-Pro, a synthetic tripeptide added for stability. The full sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro.
A 2016 Frontiers in Pharmacology paper describes Selank as a synthetic tuftsin analogue developed at the Institute of Molecular Genetics of the Russian Academy of Sciences together with the V.V. Zakusov Research Institute of Pharmacology. That lineage matters because it connects the compound's construction directly to an immune molecule, even though much of the published work asks questions about anxiety and the nervous system.
The chemical identity is specific. PubChem lists Selank under CAS number 129954-34-3 and PubChem CID 11765600, with molecular formula C33H57N11O9 and molecular weight of about 751.9 g/mol. FDA's substance registry lists the identifier UNII TS9JR8EP1G. Sequence, formula, mass, CAS number, CID, and UNII provide several ways to confirm that a paper or analytical record refers to the same compound.
The same lab that produced Semax
Selank and Semax came from the same institute. Both are heptapeptides, and both end with the C-terminal Pro-Gly-Pro motif. Their parent sequences differ: Selank derives from tuftsin, while Semax derives from adrenocorticotropic hormone, or ACTH.
A 2020 functional MRI study compared Selank and Semax directly in 52 healthy participants. Curo maintains a separate Semax research-material page, while the Semax ACTH-fragment research overview covers that sibling compound's origin and 2026 regulatory record. The shared tail and institutional origin make the comparison useful, but the two peptides begin from different biological systems.
What the published studies examined
A 2008 randomized study focused on people with generalized anxiety disorder or neurasthenia. The study compared a Selank arm of 30 participants with a medazepam arm of 32 participants, for 62 people in total. The publication reported a direct comparison between the two groups. Its limited sample and diagnostic setting define the scope of the finding; they do not establish Selank as an approved anxiety intervention.
A separate 2008 publication provides the clearest return to Selank's immune-peptide origin. Researchers reported that Selank affected interleukin-6 gene expression and the balance of Th1 and Th2 cytokines in participants with generalized anxiety disorder or neurasthenia. Interleukin-6 and the Th1/Th2 balance are immune-signaling measures. Their inclusion shows that the antibody-fragment lineage and anxiety research were not isolated threads in the published program.
The 2020 functional MRI work asked a different question, comparing brain-connectivity patterns after Selank and Semax in healthy participants. Together, these publications span comparative psychiatric research, immune signaling, and brain imaging. They do not form a large registered development program, and they should not be compressed into a single benefit claim.
Regulatory position in 2026
Selank has no FDA approval for any indication. It was not among the substances reviewed at FDA's Pharmacy Compounding Advisory Committee meeting on December 4, 2024. That meeting covered AOD-9604, CJC-1295, and substances related to thymosin alpha-1.
Selank was also absent from the July 23 and 24, 2026 committee agenda. The 2026 meeting notice listed BPC-157, KPV, TB-500, MOTS-c, emideltide, Semax, and epitalon.
An earlier FDA document mentions the compound in a different context. A November 10, 2021 warning letter to Advanced Nutriceuticals LLC, doing business as the Guyer Institute of Molecular Medicine, stated that a group of substances including Selank "were not nominated for inclusion on the 503A bulks list." The document was a general compliance letter to that firm, not an action over Selank specifically.
A ClinicalTrials.gov search for Selank as an intervention returns no registered Selank studies. The published studies above remain individual literature records rather than entries in a registered Selank study set on that database.
Confirming identity on a Selank lot
A lot record should connect the labeled material to a specific analytical report. Start by matching the lot number on the material with the lot number on the certificate. Then compare the compound name, expected sequence, molecular formula, and expected mass. Curo's guide to verifying a certificate against its lot explains the traceability check.
Curo's testing standard uses exactly three methods: HPLC, LC-MS, and endotoxin testing. HPLC reports chromatographic purity. LC-MS supports identity by comparing observed mass data with the expected compound. Endotoxin testing measures a separate quality attribute. The Curo quality and testing standard explains the role of each method.
For Selank, the expected identity record includes the seven-residue sequence, CAS 129954-34-3, molecular formula C33H57N11O9, molecular weight of about 751.9 g/mol, PubChem CID 11765600, and UNII TS9JR8EP1G. No single identifier replaces lot matching or the three analytical methods. Storage documentation is another part of material handling, covered in the guide to research-peptide and bacteriostatic-water storage.
Further reading
The same Russian research tradition produced Epitalon, a tetrapeptide known for telomere work that was carried out in cultured cells rather than in people. Its evidence is traced in Epithalon's record, from cell culture to rhesus monkeys.
Pinealon comes out of the same peptide-bioregulator programme and shows what a much shorter record looks like: three cell systems, two rodent models, and no UNII on file at FDA. The testing history is set out in Pinealon: where the EDR tripeptide has been tested.
Common questions
Why is tuftsin central to Selank's story?
Tuftsin supplies Selank's first four residues: Thr-Lys-Pro-Arg. Those residues come from the heavy chain of immunoglobulin G. Adding Pro-Gly-Pro creates the seven-residue Selank sequence, linking an antibody fragment to a compound studied across anxiety, immune-signaling, and brain-imaging contexts.
Was Selank compared with medazepam?
Yes. The 2008 randomized publication included 30 participants receiving Selank and 32 receiving medazepam. Reporting that comparison identifies the study design; it does not make Selank an FDA-approved intervention or establish a general advantage over another compound.
Did FDA review Selank at its 2024 or 2026 committee meetings?
No. Selank did not appear among the substances reviewed at the December 4, 2024 meeting or the July 23 and 24, 2026 meeting. It was mentioned in the 2021 compliance letter described above.
What should match on a Selank lot record?
The lot number should connect the material and certificate. The sequence, formula, expected mass, CAS number, CID, and UNII should align with the Selank identity record, while HPLC, LC-MS, and endotoxin testing report three distinct analytical dimensions.