Semax and Alzheimer's: What the 2025 Amyloid Plaque Study Means

A 2025 study in Acta Naturae reports one of the most striking signals for an intranasal peptide in an Alzheimer's disease model to date. In APPswe/PS1dE9/Blg transgenic mice, a common model of beta-amyloid pathology, 15 doses of Semax at 50 micrograms per kilogram reduced cortical plaques by 2.8-fold and hippocampal plaques by 2.6-fold compared with untreated controls. Cognitive function improved in parallel. The effect persisted into later life stages, from 7.5 to 8.5 months of age.

The finding is a mouse study, not a human trial. It nevertheless rewrites the plausibility case for Semax in neurodegenerative research, especially in light of a second 2025 paper that proposes a concrete molecular mechanism: copper chelation at beta-amyloid.

Semaxcognitive

Brain-boosting nootropic peptide derived from ACTH. Increases BDNF (brain-derived neurotrophic factor), enhances focus, memory, and mental clarity. Widely used in Russian clinical practice for cognitive enhancement.

What the Study Showed (Radchenko 2025)

Study Design

The Radchenko group at the Institute of Molecular Genetics used the APPswe/PS1dE9/Blg transgenic line. This strain co-expresses two human familial Alzheimer mutations, the Swedish APP double mutation and the exon 9 deletion of presenilin-1. The model develops characteristic amyloid plaques and behavioural deficits that track human disease pathology at a reasonable face-validity level.

Animals received Semax at 50 micrograms per kilogram by intranasal administration. Fifteen doses were delivered on an every-other-day schedule across one month. Outcomes were plaque load in the cortex and hippocampus, behavioural cognition and longitudinal persistence into later age.

Results

The headline numbers are unusual for a neurodegeneration intervention. Cortical amyloid plaque density dropped by a factor of 2.8 compared with untreated transgenic controls. Hippocampal plaque density dropped by a factor of 2.6. Both reductions were statistically meaningful and consistent across animals.

Behavioural cognition improved alongside plaque reduction. Treated mice performed better in the cognitive assays used in the paper, which is the pattern expected if amyloid reduction translates to functional benefit rather than being a purely biochemical shift. The durability finding matters as much as the acute effect: the signal persisted at 7.5 to 8.5 months of age, suggesting that the one-month course produced a change that outlasted the dosing window.

Mechanism: How Semax Acts

Two lines of evidence now converge on a dual mechanism for Semax in Alzheimer-adjacent biology. The first is a direct biochemical interaction with the pathological beta-amyloid species. The second is the long-established neurotrophic axis that Semax activates in the hippocampus.

Copper Chelation (Tomasello 2025)

In a separate 2025 paper in Bioinorganic Chemistry and Applications (Tomasello MF et al., PMID 40496623), the authors report that Semax acts as a copper chelator. In vitro, Semax extracts Cu(II) ions from pre-formed Cu(II)-beta-amyloid complexes. This matters because copper binding to beta-amyloid is considered one of the drivers of redox stress, reactive oxygen species generation and oligomer toxicity. By silencing the redox activity of these complexes, Semax would interrupt one of the more damaging downstream consequences of amyloid accumulation, even before the plaques themselves are removed.

The chelation finding is notable because it fits the plaque data. A peptide that removes catalytically active copper from beta-amyloid would be expected to shift the equilibrium toward clearance, reduce secondary oxidative damage and, over weeks, lower plaque burden. Radchenko's in vivo observation and Tomasello's in vitro mechanism are consistent.

BDNF, NGF and the TrkB Pathway (Dolotov 2006)

The neurotrophic arm of Semax is older and better established. The foundational work by Dolotov and colleagues, published in Brain Research in 2006 (PMID 16996037), showed that intranasal Semax upregulates brain-derived neurotrophic factor (BDNF) and its receptor TrkB in the rat hippocampus, while also influencing nerve growth factor (NGF) expression. BDNF/TrkB signalling is central to hippocampal synaptic plasticity, long-term potentiation and memory formation.

This is the second leg of the dual mechanism. In an Alzheimer model that loses hippocampal synaptic integrity over time, a peptide that both reduces amyloid-copper toxicity and re-engages BDNF/NGF-driven plasticity has two independent mechanistic entry points. The cognitive improvement reported by Radchenko in the presence of plaque reduction fits this combination more cleanly than either mechanism alone.

Context: The Amyloid Hypothesis and Other Approaches

The amyloid hypothesis has dominated Alzheimer research for three decades, with uneven clinical results. Passive immunotherapy with aducanumab (Aduhelm) was FDA approved in 2021 under significant controversy and subsequently withdrawn. Lecanemab (Leqembi) received traditional approval in 2023 and demonstrated modest cognitive slowing with a notable rate of amyloid-related imaging abnormalities (ARIA). Donanemab added a further data point. GLP-1 agonists as a non-amyloid approach were tested in EVOKE and EVOKE+ in 2025 and failed to meet primary endpoints.

Against this backdrop, a small Russian heptapeptide with a plaque-reduction signal in the low-single-digit microgram range and no reported ARIA is unusual. The Radchenko and Tomasello findings do not overturn the amyloid hypothesis. They extend it in a direction that has been under-explored in the West: metal-mediated toxicity as a therapeutic target, combined with neurotrophic restoration.

What This Does Not Mean

Honest framing matters here more than enthusiasm. The Radchenko 2025 data are preclinical. They are the strongest published plaque-reduction signal for Semax to date, but they are mouse data. A number of amyloid-modifying approaches have produced encouraging rodent data without successful human translation. The APPswe/PS1dE9 model captures some but not all features of human Alzheimer disease, and clinical Alzheimer is a multi-decade process that no mouse model fully reproduces.

There is no human randomised controlled trial of Semax in Alzheimer disease. The clinical Russian data on Semax focus on post-stroke recovery, cognitive disorders in a broader sense, and short-term cognitive performance in healthy adults. An Alzheimer RCT would require at minimum a biomarker-driven Phase 2 programme, likely with PET amyloid imaging, CSF tau measurements or plasma phospho-tau endpoints, alongside established cognitive scales.

Implications for Further Research

The Radchenko and Tomasello findings define a clear research agenda. Four questions stand out.

First, does the plaque-reduction signal replicate across independent laboratories, alternative Alzheimer models (e.g. 5xFAD, 3xTg-AD) and different dosing intervals? Replication is the weak point of most rodent neurodegeneration literature, and Semax is not an exception.

Second, does the copper chelation mechanism translate from in vitro extraction of Cu(II) from Cu(II)-amyloid complexes to the intact rodent brain under in vivo redox conditions? Metal-chelation therapy has a long and mixed history in Alzheimer research, from clioquinol to PBT2, and mechanism-level work matters.

Third, how do the plaque and cognition signals interact with the BDNF/NGF arm? Separating the chelation contribution from the neurotrophic contribution is difficult in a model where both mechanisms operate. Combination designs or pathway-specific knockouts could resolve this.

Fourth, the intranasal route deserves continued attention. Semax reaches the brain via the olfactory pathway and bypasses the blood-brain barrier, which is one of the longstanding obstacles for peptide therapeutics in neurodegeneration. The APPswe/PS1dE9 data were generated with a practical, non-invasive protocol that is closer to what a human trial might use than a stereotactic injection.

The 2025 results do not mean Semax will work in Alzheimer patients. They do mean that the research programme around Semax has produced a hypothesis that is no longer dismissible without data. For researchers interested in peptide approaches to neurodegeneration, that is a meaningful shift.

For qualified laboratories and researchers in the European Union, research-grade Semax is available for in vitro and preclinical work. It is not an Alzheimer therapy, and it is not a clinical product. It is the same molecule the Radchenko group dosed into their transgenic mice, supplied in the same form.

References

1. Radchenko AI, et al. Intranasal Semax in APPswe/PS1dE9/Blg transgenic mice. Acta Naturae, 2025. PMID 41479572. https://pmc.ncbi.nlm.nih.gov/articles/PMC12755871/
2. Tomasello MF, et al. Semax as a copper chelator: extraction of Cu(II) from Cu(II)-Abeta complexes. Bioinorganic Chemistry and Applications, 2025. PMID 40496623.
3. Dolotov OV, et al. Semax, an ACTH(4-10) analog with nootropic effects, regulates BDNF and TrkB expression in the rat hippocampus. Brain Research, 2006. PMID 16996037.
4. Filippenkov IB, et al. ACTH-like peptides normalise gene expression after transient middle cerebral artery occlusion. Biomedicines, 2024. PMID 39767736.
5. Kaplan AY, et al. Semax in healthy human volunteers. Neuroscience Research Communications, 1996.