Dihexa for Chemo Brain (CICI): Cancer-Related Cognitive Impairment & the 2026 UK Survivorship Review

Around 3.5 million people now live with cancer in the UK, and somewhere between one in three and three in four of them will experience measurable cognitive change during or after treatment — the cluster of symptoms patients call chemo brain and clinicians label cancer-related cognitive impairment (CRCI) or chemotherapy-induced cognitive impairment (CICI). 2026 was the year the donepezil Phase 3 trial reported a clear miss and the Phase 2 EXCAP exercise + low-dose ibuprofen trial reported a positive signal — a turning point that has reframed CRCI as a problem of persistent neuroinflammation, suppressed hippocampal neurogenesis and reduced BDNF/HGF signalling. Within that frame, Dihexa — a synaptogenic peptide that activates HGF/c-Met — is mechanistically interesting. It is also, for cancer survivors specifically, the compound where the safety questions are most difficult and most important. This is the rigorous 2026 UK review.

What Chemo Brain Actually Is in 2026

"Chemo brain" is the survivor-coined name for what oncology now calls cancer-related cognitive impairment (CRCI) — or, when the trigger is specifically cytotoxic chemotherapy, chemotherapy-induced cognitive impairment (CICI). It is not a single deficit. The most consistently affected domains are working memory, verbal learning, attention, processing speed and executive function, with patients typically describing it as "slower thinking", word-finding difficulty, multitasking failure, and the unsettling sense that they cannot retain a meeting agenda the way they used to.

For most of the last twenty years CRCI was treated as a curiosity, frequently dismissed as fatigue, mood, or pre-existing decline. Three things have changed:

• Cancer survival has improved dramatically. Average UK cancer survival is now over ten years from diagnosis according to Cancer Research UK, and 3.5 million people now live with a cancer history ([7] Macmillan). The downstream cognitive problems are now a quality-of-life issue at population scale.
• Functional and structural neuroimaging has demonstrated real, measurable changes — reduced grey-matter volume in frontal and temporal cortices, altered functional connectivity in default-mode and frontoparietal networks, and white-matter integrity changes on diffusion tensor imaging that correlate with the symptom severity patients report.
• Mechanistic neuroscience has caught up. The 2025 ScienceDirect mechanism review and the 2024 Frontiers update converge on a small set of biological drivers ([3][4]): microglial priming, oligodendrocyte progenitor dysfunction, suppressed hippocampal neurogenesis, mitochondrial damage in neurons, and reduced trophic support — especially BDNF and HGF.

In other words, chemo brain in 2026 looks structural, biological, and increasingly tractable. That tractability is the reason interest in synaptogenic compounds has grown — and also the reason careful evidence-checking matters.

Prevalence and the UK Survivorship Picture

The most-cited UK figures come from Cancer Research UK and Macmillan Cancer Support, both of which patient-test their public information against survivor consultation panels:

• Up to 75% of people experience cognitive changes during cancer treatment.
• Up to 35% have cognitive symptoms after treatment finishes.
• Most people improve substantially within a year.
• A meaningful minority — particularly after intensive chemotherapy, CNS-directed treatment, or whole-brain radiotherapy — have symptoms that persist for years.

For breast cancer specifically, the most-studied population, a Nature Scientific Reports systematic review and meta-analysis estimated clinically significant cognitive impairment in approximately one in three survivors after chemotherapy ([8]). The Oxford CICARO observational cohort published in The Oncologist tracked the recovery curve out to 2–3 years and showed substantial improvement on average, with persistent impairment in a sub-group ([9]).

Against the backdrop of 3.5 million UK cancer survivors (and rising), even the conservative 35% post-treatment figure points to over a million people with measurable post-treatment cognitive symptoms. Few of them have access to a dedicated CRCI service. The Royal Marsden's CRCI clinic is the most-cited NHS service in 2026; most areas of the UK have nothing equivalent. That gap matters: it is the reason this article exists, and it is also the reason an unproven compound like Dihexa attracts the attention it does.

The Biology: Microglia, BDNF, Hippocampal Neurogenesis & White Matter

To understand whether a synaptogenic peptide could matter, you need the modern biology of CICI. Five mechanisms recur across recent reviews and converge on the same final-common pathway ([3][4][10]):

1. Persistent microglial activation

Microglia — the brain's resident immune cells — are the central player in CICI. The seminal Gibson et al. work in Cell (2018) showed that even a single course of methotrexate in mice produces persistent microglial activation that drives oligodendrocyte progenitor dysfunction, demyelination of corpus callosum white matter, astrocyte reactivity and measurable cognitive deficit. Critically, depleting microglia with a CSF1R inhibitor reverses the phenotype and restores BDNF expression ([10]). The microglia are the proximate driver; everything downstream — neurogenesis, BDNF, white matter, cognition — rides on them.

2. Suppression of hippocampal neurogenesis

The dentate gyrus of the adult hippocampus continues to generate new neurons throughout life, and that neurogenesis is essential for pattern separation, contextual learning and adaptive forgetting. Chemotherapy and CNS irradiation suppress neurogenesis through inflammatory cytokine signalling (IL-6, TNF-α) and through reduced BDNF availability. Hippocampal-avoidance whole-brain radiotherapy (NRG Oncology CC001) showed measurable cognitive preservation when neurogenic regions are spared ([11]) — biological proof that protecting the neurogenic niche matters clinically.

3. Reduced BDNF and trophic support

Across rodent and human work, chemotherapy reduces BDNF expression in hippocampus and prefrontal cortex. The mechanisms are multiple — direct cytotoxic damage to BDNF-producing neurons, microglia-mediated suppression, and reduced exercise-driven BDNF release in patients who become deconditioned during treatment. BDNF reduction matters because it is the single best-characterised driver of synaptic plasticity in the regions CICI affects most.

4. White-matter injury and oligodendrocyte loss

The processing-speed deficit that survivors report so consistently maps onto white-matter injury. Methotrexate, intrathecal cytarabine and cranial radiotherapy disrupt oligodendrocyte progenitors, and the demyelination that follows slows axonal conduction in long-range cortical-cortical pathways. The Stanford / Monje group's mechanistic work made this concrete: chemotherapy-driven microglial activation arrests oligodendrocyte maturation, and rescuing the microglial phenotype rescues myelination ([10]).

5. Reduced HGF / c-Met signalling

HGF is a pleiotropic growth factor expressed widely in brain, with c-Met receptors on neurons, astrocytes and oligodendrocytes. The Wright laboratory characterised c-Met as a tractable target for cognitive enhancement in Alzheimer's models ([5][6]). In CICI specifically, HGF/c-Met signalling supports oligodendrocyte progenitor survival and remyelination, hippocampal neurogenesis and synaptic plasticity — and chemotherapy reduces all three. This is the mechanistic point at which Dihexa, an angiotensin IV-derived peptide that pharmacologically activates the HGF/c-Met axis ([6]), becomes interesting on paper.

It is also the point where the safety question becomes unavoidable, because c-Met is a proto-oncogene — covered in the dedicated section below.

Where Dihexa Fits the CICI Picture

Dihexa was developed in the Wright laboratory at Washington State University, originally as a small-molecule compound that could survive oral dosing and cross the blood-brain barrier to do what BDNF cannot — reach the brain and drive synaptogenesis. The detailed pharmacology is in the mechanism of action guide; in summary:

• Dihexa pharmacologically activates the HGF/c-Met system, with the synaptogenic effects in primary hippocampal neuron cultures shown to be c-Met dependent (Benoist 2014, [6]).
• Animal cognition models — the Morris water maze, novel object recognition, the radial-arm water maze in scopolamine and ageing rats — show task-relevant cognitive rescue.
• The downstream biology — increased dendritic spine density, restored long-term potentiation, modest pro-neurogenic effects — maps closely onto the deficits CICI produces.

If you took the CICI mechanism diagram and asked "what theoretical pharmacology would address most of this", a c-Met agonist that drove synaptogenesis and supported oligodendrocyte and neurogenic biology would be a coherent answer. That is what Dihexa is, on paper.

What it is not, in 2026, is a tested treatment in cancer survivors. There is:

• No human trial of Dihexa in CICI, CRCI or any oncology indication.
• No published case series of cancer survivors using Dihexa, with or without controls.
• No oncology pharmacovigilance dataset.
• No randomised study of any meaningful size in any neurological indication.
• No safety study in patients on tamoxifen, aromatase inhibitors, immune checkpoint inhibitors or any active anti-cancer therapy.

The mechanistic story is real. The clinical story does not exist. The most analogous compound that has been tested in humans — fosgonimeton (ATH-1017), also a small-molecule HGF positive modulator — missed its primary endpoint in Alzheimer's (LIFT-AD) and shifted to Parkinson's disease dementia and DLB (SHAPE), with mixed signals. That is the closest a c-Met-axis cognition compound has come to clinical proof; Dihexa is not at that level of evidence.

The 2026 Evidence Landscape: What Worked, What Didn't

Three trials and one repurposing paper define the 2026 CICI conversation.

EXCAP exercise + low-dose ibuprofen (Phase 2, Janelsins, 2026)

Published in Cancer (Wiley, 2026), the Phase 2 trial from the University of Rochester / Wake Forest NCORP base randomised patients on active chemotherapy to a home-based progressive walking-and-resistance programme (EXCAP), low-dose ibuprofen 400 mg twice daily, both, or control. Both interventions independently improved cognitive function compared with control across multiple domains ([1]). The effect sizes were modest but the cohort was on active chemotherapy — the hardest population in which to demonstrate a cognitive signal. Mechanistically the trial supports the BDNF / neuroinflammation pillar of the CICI hypothesis: exercise raises BDNF and IGF-1; low-dose ibuprofen reduces COX-2-driven microglial activation. This is the most important positive trial in CICI in 2026 and it points squarely at the same biology Dihexa engages — without using Dihexa.

Donepezil REMEMBER (Phase 3, WF-97116, 2024 readout, 2025 publication)

The Wake Forest NCORP REMEMBER trial randomised over 270 breast cancer survivors with persistent post-chemotherapy cognitive impairment to donepezil 5 mg titrated to 10 mg, or placebo. The primary endpoint, the Hopkins Verbal Learning Test-Revised total recall at 24 weeks, was no different between arms ([2]). Secondary domains — attention, executive function, verbal fluency, processing speed — were also unimproved. Donepezil was perhaps the most plausible drug-repurposing candidate in CRCI, and it failed cleanly. The implication is that simply boosting cholinergic tone is not enough; the CRCI deficit is downstream of structural / synaptic problems that a cholinesterase inhibitor cannot address.

Imeglimin repurposing (Springer 2026)

Imeglimin is a licensed anti-diabetic drug that improves mitochondrial function. Onyango's 2026 paper in Cellular and Molecular Neurobiology proposes imeglimin repurposing for CICI on the basis that mitochondrial dysfunction and neuroinflammation are central to the syndrome ([12]). It is a position paper, not a trial — but it illustrates how the CICI pharmacology pipeline is now being shaped by the same convergent biology that motivates interest in synaptogenic peptides.

Modafinil and methylphenidate

Stimulants have been studied in cancer-related fatigue and cognition. Modafinil and methylphenidate produce small-to-moderate short-term improvements in attention and processing speed in some trials, particularly in patients with co-existent fatigue. They do not address the underlying biology and are not first-line in UK NHS CRCI care. They are also not a model for what Dihexa does — stimulants modulate dopaminergic and noradrenergic signalling acutely; Dihexa is a slow, structural compound.

The 2026 trial pattern is clear: biology-targeted interventions (exercise, low-dose anti-inflammatory) work modestly; symptomatic monotherapy (donepezil, stimulants) does not. That is a conditional argument for the Dihexa mechanism — and a conditional argument is not the same as evidence.

Cancer-Specific Pictures: Breast, Lymphoma, Brain, Colorectal & Beyond

CICI does not look identical across cancer types, and the implications for any cognitive intervention differ accordingly.

Breast cancer: the dominant evidence base

Breast cancer survivorship is the population in which CICI has been most rigorously studied. The drivers are typically anthracycline / taxane chemotherapy (doxorubicin, paclitaxel) plus, in many cases, years of adjuvant endocrine therapy. The post-treatment phenotype is verbal memory and executive function deficit, often accompanied by fatigue, mood symptoms and sleep disruption — covered separately in the depression and mood, anxiety and stress, and sleep and memory consolidation reviews because they reinforce each other. Critically, adjuvant endocrine therapy is itself contingent on suppressing residual hormone-driven disease, which is the population in whom a c-Met agonist is least appropriate.

Lymphoma and haematological cancers

Methotrexate — particularly intrathecal or high-dose systemic methotrexate — is the most mechanistically problematic chemotherapy for the brain. The Stanford / Monje group's preclinical work was specifically methotrexate-driven ([10]). Patients with primary CNS lymphoma, lymphoma with CNS prophylaxis, and acute lymphoblastic leukaemia have particularly high rates of persistent cognitive symptoms. Lymphoma Action UK has produced some of the most accessible UK patient resources on CRCI.

Brain tumour survivors

Whole-brain radiotherapy, hippocampal-region radiotherapy and post-neurosurgical recovery produce a distinctively severe CRCI picture. The NRG Oncology CC001 trial showed that hippocampal-avoidance radiotherapy preserves cognition ([11]) — clinical proof that the neurogenic niche is functionally critical. This is also the population in whom recurrence surveillance is most acute and any unproven c-Met agonist is most contraindicated.

Colorectal and other solid tumours

Oxaliplatin- and 5-fluorouracil-based regimens (FOLFOX, FOLFIRI) produce a CRCI picture often dominated by peripheral chemotherapy-induced peripheral neuropathy plus subjective cognitive complaints. The cognitive component is real but typically less structurally measurable than in breast or haematological cancers.

Immune checkpoint inhibitors and CAR-T

Newer cancer therapies introduce new cognitive syndromes — immune-related encephalitis with checkpoint inhibitors, immune effector cell-associated neurotoxicity syndrome (ICANS) with CAR-T cell therapy. These are not "chemo brain" in the classic sense and are managed acutely; their late cognitive sequelae are an active research area.

The c-Met Question: Cancer Recurrence Risk

This is the section every cancer survivor reading this article should focus on.

c-Met, encoded by the MET proto-oncogene, is the receptor tyrosine kinase that HGF activates physiologically. It is essential for normal embryonic development, wound healing, and adult tissue repair. It is also one of the most frequently dysregulated oncogenic signalling pathways in human cancer. MET amplification, MET exon 14 skipping mutations, MET overexpression and HGF/MET autocrine loops are documented drivers in non-small-cell lung cancer, gastric cancer, hepatocellular carcinoma, colorectal cancer, glioblastoma, papillary renal carcinoma, head and neck squamous cell carcinoma and a subset of breast cancers.

The pharmaceutical response to that biology is unambiguous: licensed cancer drugs that inhibit c-Met. Capmatinib (Tabrecta) and tepotinib (Tepmetko) are licensed for MET exon 14-altered NSCLC. Savolitinib is approved in some markets. Crizotinib has multitarget MET activity. The drug development direction in oncology is consistently to turn c-Met off.

Dihexa does the opposite. It activates HGF/c-Met. In a healthy nervous system the synaptogenic effect is desirable; in a survivor with residual disease, micrometastatic disease, hereditary cancer predisposition, or a tumour driven by aberrant MET signalling, it is exactly the wrong direction.

The honest position in 2026 is:

• There is no published study of Dihexa exposure and cancer recurrence rates.
• There is no preclinical study in tumour-bearing animals that systematically addresses recurrence under Dihexa.
• The theoretical concern is biologically grounded, not speculative.
• The risk-benefit math for a cancer survivor is structurally different from the math for a healthy adult experimenter.

For that reason, this site does not recommend Dihexa for anyone with active cancer, recent cancer, a strong family history of cancer, hereditary cancer predisposition (BRCA1/2, Lynch, Li-Fraumeni, Cowden), or who is receiving any active anti-cancer therapy. The cognitive symptoms are real; this is not the right tool to address them. Established CICI services and the evidence-based interventions in the next section are the right pathway.

What Actually Works for Chemo Brain in 2026

The evidence-based picture is not perfect — but it is real and accessible.

Progressive aerobic and resistance exercise

The single best-supported intervention. Multiple randomised trials including the 2026 EXCAP study ([1]) show measurable cognitive benefit. The mechanism is the same biology Dihexa engages: BDNF release, reduced systemic inflammation, improved cerebral perfusion, hippocampal volume support. Macmillan's Move More programme and most NHS survivorship pathways now include structured physical activity as a core element.

Cognitive rehabilitation and CRCI clinics

The Royal Marsden CRCI service is the most-cited UK example. Components include neuropsychological assessment, compensatory strategy training (external aids, structured task management, cognitive pacing), and cognitive-behavioural approaches to the secondary anxiety, frustration and demoralisation that CRCI produces.

Treat the comorbid conditions

CRCI very rarely exists in isolation. Cancer-related fatigue, sleep disruption, depression and anxiety all lower cognitive performance independently and are treatable. The sleep and memory consolidation, depression and mood and anxiety and stress reviews on this site cover the relevant biology in detail. The greatest cognitive gains in survivorship often come from sleep, mood and fatigue care — not from any putative pro-cognitive drug.

Diet, vascular health and metabolic control

Mediterranean and MIND-style diets, blood pressure control, glycaemic control and lipid management have small but additive cognitive effects, and matter especially in survivors who are also at elevated cardiovascular risk from anthracycline or radiation exposure.

Pharmacological options

Donepezil missed in Phase 3 (REMEMBER, [2]). Modafinil and methylphenidate have small symptomatic effects in selected patients with prominent fatigue. Antidepressants help when CRCI overlaps with mood; SSRIs are not a CRCI treatment per se but the depression-cognition relationship is bidirectional. None of these are first-line in routine NHS care, and none of them resolve the underlying problem.

Where does Dihexa actually sit?

In a hypothetical world where Dihexa had a controlled human trial in CICI showing clear benefit and no recurrence signal, it would be positioned as a structural-recovery adjunct alongside exercise. We do not live in that world. In 2026, with the evidence base as it stands, the appropriate position is: not a treatment, not a recommendation, and a meaningful safety concern in cancer survivors specifically.

Who Should Not Consider Dihexa for Chemo Brain

The list of contraindications for cancer survivors is broader than for the general population:

• Anyone with active cancer, in any stage.
• Anyone recently treated for cancer (within the recurrence-surveillance window).
• Anyone receiving adjuvant endocrine therapy (tamoxifen, anastrozole, letrozole, exemestane, fulvestrant, GnRH analogues).
• Anyone with a MET-driven tumour or who has had a tumour with documented MET amplification, exon 14 skipping or overexpression.
• Anyone with a hereditary cancer syndrome (BRCA1/2, Lynch, Li-Fraumeni, Cowden, FAP, von Hippel-Lindau).
• Anyone receiving active immune checkpoint inhibitor or CAR-T therapy.
• Anyone with active or recent brain tumour or post-radiotherapy in the recurrence window.
• Anyone with strong family history of breast, ovarian, colorectal or pancreatic cancer in the absence of a clear genetic workup.
• Anyone pregnant, breastfeeding or trying to conceive.
• Anyone whose oncology team has not been consulted — which, candidly, is most people considering this.

For survivors not on this list who still want to engage with the mechanism conceptually, the safer entry point is the lifestyle biology: exercise (which raises BDNF), sleep optimisation, stress reduction and treating co-existing depression or anxiety. Those interventions engage the same final pathway with a much better safety profile.

Community Reports: What Cancer Survivors Actually Say Online

Online reports from cancer survivors who have tried Dihexa for chemo brain are sparse, anecdotal, and uncontrolled. The available pattern across forum posts and personal blogs:

• A small number of breast cancer survivors describe subjective improvement in word-finding and processing speed within four to six weeks.
• A similar small number describe no perceptible benefit, or attribute change to time, exercise, or sleep that improved in parallel.
• Vivid dreams and altered sleep architecture are reported as consistently in cancer-survivor users as in the general user base — covered in the sleep and memory consolidation review.
• A minority report worsened anxiety or paradoxical agitation in the first one to two weeks.
• No recurrence signals or oncology adverse events have been reported in the (very limited) public anecdote pool — but absence of reports in a small uncontrolled population is not the same as safety.

This is not data. It is anecdote. It is included only because it is what readers will find online and we would rather contextualise it honestly than ignore it.

Dosing and Practical Context (For the Specific Sub-Group This Applies To)

If, having read the safety section, an adult who is not in any of the contraindicated groups still wants to use Dihexa as a research compound, the general dosing and stacking guidance is on the dedicated dosage and stacking guide pages and is not duplicated here. The points specific to the CICI conversation:

• The therapeutic logic, if any, is structural — weeks-to-months timeframes, not acute symptomatic dosing.
• Cycling matters; sustained continuous c-Met activation is one of the long-term safety unknowns.
• Dihexa-specific symptoms (vivid dreams, altered sleep, occasional headache, transient irritability) are covered on the side effects page.
• Sleep hygiene, dosing earlier in the day, and not stacking with stimulants are particularly relevant in fatigued cancer survivors.
• Anyone considering a peptide stack should treat the recurrence-risk question as overriding any optimisation goal.

None of this constitutes a recommendation. The appropriate clinical pathway for chemo brain is in the evidence-based section above.

The Bottom Line in 2026

Chemo brain is real, mechanistically tractable, and substantially under-served in routine UK care. The biology — persistent microglial activation, suppressed hippocampal neurogenesis, reduced BDNF and HGF signalling, white-matter injury — converges on targets that a synaptogenic peptide could in principle address. The 2026 EXCAP trial is the most important positive signal in the field and points squarely at the same biology Dihexa engages, without using Dihexa. The donepezil REMEMBER failure shows that simple symptomatic monotherapy is not enough. The pharmacology pipeline is moving toward biology-targeted intervention.

None of that constitutes evidence that Dihexa works in chemo brain. There is no human trial, no case series and no oncology safety dossier. The c-Met axis is a recognised oncogenic pathway, the licensed drug-development direction in cancer is c-Met inhibition not activation, and the recurrence-risk concern in survivors is theoretically grounded, not abstract. For survivors on adjuvant endocrine therapy the conflict is sharper still.

The right answer in 2026 is:

1. Recognise CICI as a real and assessable condition.
2. Ask your oncology team or GP for referral to a CRCI service or, where unavailable, to neuropsychology / cognitive rehabilitation.
3. Engage with the strongest evidence-based interventions: progressive exercise, sleep, mood and fatigue management, and cognitive rehabilitation.
4. Use Macmillan, Cancer Research UK and Lymphoma Action UK as starting-point information resources.
5. Treat Dihexa, in the cancer-survivor population specifically, as a compound whose theoretical fit is good and whose safety profile in this population is unestablished — not a treatment.

The bigger conclusion is that the CICI evidence base is moving in a direction where the synaptogenic / HGF-axis hypothesis will eventually be tested cleanly. That work is not yet done. Reading this page, exercising, sleeping, and asking your oncology team about CRCI assessment is the rational 2026 plan.

Frequently Asked Questions

Can Dihexa help chemo brain?

No human trial, no case series, no oncology safety dossier. The mechanistic fit is good; the clinical evidence does not exist. The 2026 EXCAP exercise + low-dose ibuprofen Phase 2 trial is the most relevant positive signal in the field, and it does not involve Dihexa.

Could Dihexa increase the risk of cancer recurrence?

The honest answer is uncertain — and uncertainty is not safety. Dihexa activates c-Met, which is a recognised proto-oncogene and the target of licensed cancer-inhibitor drugs (capmatinib, tepotinib, savolitinib). The theoretical concern is biologically grounded. No human study has resolved it. Dihexa is not appropriate for cancer survivors as currently understood.

How common is chemo brain in the UK?

Up to 75% of people during cancer treatment and up to 35% post-treatment have measurable cognitive symptoms (Cancer Research UK). With 3.5 million UK cancer survivors (Macmillan), that implies well over a million people with persistent post-treatment symptoms.

Did the donepezil trial work?

No. The Phase 3 REMEMBER (WF-97116) trial in breast cancer survivors with persistent post-chemotherapy cognitive impairment missed its primary endpoint. Donepezil was not better than placebo on memory, attention, executive function or processing speed.

What did the 2026 EXCAP trial show?

Home-based progressive walking-and-resistance exercise and low-dose ibuprofen 400 mg twice daily independently improved cognition in patients on chemotherapy. The signal is consistent with the BDNF / neuroinflammation hypothesis of CICI.

Which chemotherapy drugs cause the most cognitive impairment?

Methotrexate (especially intrathecal or high-dose), the breast-cancer CMF and taxane regimens, doxorubicin, oxaliplatin and 5-fluorouracil are the most-implicated cytotoxic agents. Cranial radiotherapy and intrathecal cytarabine add further specific risks. Endocrine therapies (tamoxifen, aromatase inhibitors) add a separate hormonal-cognitive picture in breast cancer survivors.

Is exercise really the best intervention for chemo brain?

In the current evidence base, yes. Multiple randomised trials including the 2026 EXCAP study show measurable cognitive benefit. The mechanism (BDNF, reduced neuroinflammation, hippocampal support) is exactly the biology any pro-cognitive intervention is trying to engage. No peptide currently has comparable evidence in oncology.

Can I take Dihexa with tamoxifen or an aromatase inhibitor?

No. The pharmacological direction conflicts with the recurrence-suppression goal of adjuvant endocrine therapy. There are no safety studies. Anyone on tamoxifen, anastrozole, letrozole or exemestane should not consider Dihexa.

Is chemo brain permanent?

For most people, no. Substantial recovery typically occurs within a year of finishing treatment. A meaningful minority have symptoms that persist for years — the population in whom the treatment gap is sharpest.

Is Dihexa legal in the UK as a chemo brain treatment?

Dihexa is not a licensed medicine and is not approved by the MHRA. It is not a controlled drug under the Misuse of Drugs Act, but marketing or supplying it as a chemo brain treatment would breach UK medicines and advertising regulation. See the UK legal status page for the full position.

Selected References & Outbound Sources

1. Janelsins MC et al. Phase 2 trial of exercise and low-dose ibuprofen for cancer-related cognitive impairment in patients receiving chemotherapy (EXCAP). Cancer, 2026.
2. Wake Forest NCORP Research Base. Phase 3 randomized placebo-controlled trial of donepezil for late cancer-related cognitive impairment in breast cancer survivors exposed to chemotherapy (REMEMBER / WF-97116). 2024 readout.
3. Onzi GR et al. Chemotherapy-induced cognitive impairment: mechanisms, emerging biomarkers, and therapeutic interventions. Biochem Biophys Res Commun, 2025.
4. Frontiers in Oncology review. Cancer related cognitive impairment: a downside of cancer treatment. 2024.
5. Wright JW, Harding JW. The brain hepatocyte growth factor / c-Met receptor system: a new target for the treatment of Alzheimer's disease. J Alzheimers Dis, 2015.
6. Benoist CC et al. The procognitive and synaptogenic effects of angiotensin IV-derived peptides are dependent on activation of the hepatocyte growth factor / c-Met system. J Pharmacol Exp Ther, 2014.
7. Macmillan Cancer Support. UK cancer statistics fact sheet — 3.5 million people living with cancer.
8. Maeda S et al. Prevalence of cognitive impairment following chemotherapy treatment for breast cancer: a systematic review and meta-analysis. Scientific Reports, 2022.
9. CICARO study group. Chemotherapy-induced cognitive impairment and its long-term development in patients with breast cancer (CICARO). The Oncologist, 2025.
10. Gibson EM et al. Methotrexate chemotherapy induces persistent tri-glial dysregulation that underlies chemotherapy-related cognitive impairment. Cell, 2018.
11. Gondi V et al. Hippocampal avoidance whole-brain radiotherapy preserves cognition: NRG Oncology CC001. JCO, 2020.
12. Onyango AN. Repurposing imeglimin for chemotherapy-induced cognitive impairment: targeting mitochondrial dysfunction and neuroinflammation. Cell Mol Neurobiol, 2026.
13. Cancer Research UK. What are cognitive changes (chemo brain)?
14. Macmillan Cancer Support. Cognitive changes (chemo brain) — patient information.
15. The Royal Marsden NHS Foundation Trust. What is cancer-related cognitive impairment (CRCI)?
16. Lymphoma Action UK. Chemo brain (cancer-related cognitive impairment) — UK patient guide.
17. Cancer Research UK. Research looking at cognitive changes (chemo brain).