Peptide basics

Peptides with falling research activity: where publication counts are dropping

This page counts publications and registrations. A declining literature is not a safety finding, an efficacy finding, or a reason to use or avoid anything, and nothing here should be read as one.

The method, so you can repeat it

Each figure below is a count of PubMed records whose title or abstract contains the compound name, within a three-year publication-date window. In PubMed syntax that is the compound name in quotation marks followed by [tiab], combined with a date range in [dp]. Restricting to title and abstract keeps out records that merely cite the term in a reference list, and comparing equal-length windows removes the growth of the database itself from the picture.¹²

The compounds moving away from zero — downward

Selank: twelve, six, none

Selank returned 12 PubMed records for 2017-2019, six for 2020-2022, and zero for 2023-2025. Three consecutive complete years with no title-or-abstract record at all is the cleanest decline on the site, and it belongs to a compound that draws 6,791 English Wikipedia readers a month.¹⁸

The literature that does exist is largely mechanistic and largely Russian in origin — a 2018 review in Protein and Peptide Letters characterises it in exactly those terms, as molecular aspects of the heptapeptide's biological activity. There is no ClinicalTrials.gov record naming Selank as an intervention, and the FDA's compounding assessment states that it lacks important information regarding any safety issues raised by selank acetate administered to humans.³⁶⁷

Follistatin 344: two, two, none

A small literature that became no literature: two records in each of the first two windows, none in 2023-2025. With counts this low the percentage change is meaningless, but the arrival at zero is not — it means nothing naming this compound reached a title or abstract for three years.¹

The growth hormone releasing peptides

• GHRP-6: 66 records in 2017-2019, 48 in 2020-2022, 35 in 2023-2025.
• Hexarelin: 18, then 12, then 5.
• GHRP-2: 13, then 8, then 5.
• CJC-1295: 3, then 6, then 3 — a small literature with no trend worth naming.
• Ibutamoren (MK-677): 4, then 12, then 6.¹

GHRP-6 is the one to notice. It has the largest literature in this group by a wide margin and it is still shrinking, roughly forty-seven per cent down across the decade. Hexarelin has fallen by around 70% and GHRP-2 by around 60%, both from a much smaller base. None of the five has a registered study naming it as an intervention.¹³

Melanotan II

16 records in 2017-2019, 29 in 2020-2022, 10 in 2023-2025. The middle window is the anomaly rather than the last one, and the shape is a spike and retreat rather than a steady decline. It is included because the endpoint is genuinely lower than the start, and excluded from the strong claims because a single elevated window is not a trend.¹

What a declining count does not establish

The tempting reading is that these compounds were investigated, found wanting, and abandoned. That reading requires a finding, and for every compound on this page there is no registered human trial and therefore no posted human result to have been the finding. Whatever caused researchers to move on, it was not a public negative result about people.³

The ordinary explanations are duller. Funding follows fashion and follows commercial prospects. A compound with no patentable position and no sponsor attracts neither. Laboratories close, principal investigators retire, and small national literatures shrink when the group that sustained them stops. Attrition in drug development is also simply high: an analysis of over 400,000 development-phase records estimated the overall probability of a drug moving from phase 1 to approval in the low double digits, so most things that get studied stop being studied.⁵

The literature is also a partial view

Publication counts undercount research for a well-documented reason: a large share of completed trials never reach a journal. A cross-sectional analysis of NIH-funded trials registered on ClinicalTrials.gov found fewer than half published in a peer-reviewed journal within 30 months of completion. Silence in the literature therefore travels partly under its own power, independent of what anyone found.⁴

That cuts against over-reading a decline, and it also cuts against comfort. If research on a compound had continued out of public view, the compounds on this page would still show these counts. The reader's position is unchanged either way: there is progressively less to read, and there was never a registered human trial to read in the first place.³⁴