Phosphorylethanolamine (Phosphoethanolamine)
1. Identity and Chemical Characterization
1.1 Names and Identifiers
Phosphorylethanolamine, also known as phosphoethanolamine, is an ethanolamine derivative that is used to construct two different categories of phospholipids. Its recognized synonyms include 2-aminoethyl dihydrogen phosphate, O-phosphocolamine, O-phosphoethanolamine, colamine phosphate, ethanolamine phosphate, ethanolamine O-phosphate, mono(2-aminoethyl) phosphate, and phosphonoethanolamine, among others. Its Chemical Abstracts Service (CAS) registry number is 1071-23-4.
The compound is also known as 2-aminoethyl dihydrogen phosphate and is particularly valued for its ability to act as a phosphoamino acid, making it a crucial component in the synthesis of phospholipids and other bioactive molecules.
1.2 Molecular Structure and Physical Chemistry
Phosphorylethanolamine is an ethanolamine derivative used to construct two categories of phospholipids: one termed a glycerophospholipid and the other a sphingomyelin — or more specifically within the sphingomyelin class, a sphingophospholipid. It is a polyprotic acid with two pKa values at 5.61 and 10.39. The molecular formula is C₂H₈NO₄P, and the molecular weight is 141.06 g/mol.
Phosphorylethanolamine (O-phosphorylethanolamine) is a phosphomonoester metabolite of the phospholipid metabolism. It is a precursor of phospholipid synthesis and a product of phospholipid breakdown.
1.3 Natural Occurrence and Biological Distribution
Phosphorylethanolamine (monoaminoethyl phosphate) is a membrane phospholipid and an important precursor of phosphatidylcholine. It is found in most animal tissues and various human extracranial tumors, playing a critical role in membrane integrity, cell division, and mitochondrial respiratory function.
Phosphomonoesters, of which phosphoethanolamine is a major component, are present at much higher levels in the brain than in other organs. In the developing brain, phosphomonoesters are normally elevated during the period of neuritic proliferation. This also coincides with the occurrence of normal programmed cell death and synaptic pruning in the developing brain. These findings are consistent with the role of phosphomonoesters in membrane biosynthesis.
Phosphoethanolamine (PE) and phosphocholine (PC) are essential precursors and degradation products of phosphatidylethanolamine (PtE) and phosphatidylcholine (PtC) — the major constituents of membrane phospholipids. PE and PC are also important in cellular neurochemistry by interactions with blood-brain-barrier permeable substrates and cellular signaling molecules.
1.4 Common Forms and Preparations
In practical applications, O-phosphorylethanolamine is utilized in the development of pharmaceuticals, particularly in drug formulation and delivery systems. Its properties enhance the bioavailability of active ingredients, making it a valuable additive in the pharmaceutical industry. In research and experimental contexts it is produced as a synthetic, chemically pure compound. Subsequent pharmacological studies have revealed an oral bioavailability of 6–7%. Pharmacological studies comparing phosphoethanolamine made by the University of São Paulo–São Carlos and by Sigma-Aldrich (standard) found similar absolute bioavailability (6.3% versus 7%), but significant differences in half-life and time to reach maximum concentration (Tmax) when orally administered.
2. Traditional and Historical Use
Phosphorylethanolamine is an endogenous biochemical metabolite rather than a botanical extract or traditional herbal remedy. Accordingly, it does not appear in classical herbal pharmacopeias (such as those of Chinese, Ayurvedic, or European traditions), and no documented historical use of isolated phosphorylethanolamine exists in any pre-modern therapeutic tradition. Its recognition as a discrete chemical entity followed the twentieth-century development of biochemistry and phospholipid research.
The compound became associated with therapeutic claims primarily through the work of a professor at the University of São Paulo, who, according to his own words, had been conducting research on phosphoethanolamine for over 20 years. In Brazil, the distribution by researchers to patients of an investigational agent called phosphoethanolamine (PHOS) led to a widely publicized scientific controversy. PHOS is a precursor to components of the cell membrane, with some published pre-clinical studies suggesting cytotoxic activity in cancer cells. This episode — rather than any formal traditional-medicine heritage — constitutes the origin of the compound's reputation as a potential therapeutic agent.
3. Biochemistry: Biosynthesis, Endogenous Role, and Key Mechanisms
3.1 The CDP-Ethanolamine Kennedy Pathway
CTP:phosphoethanolamine cytidylyltransferase (Pcyt2) is the main regulatory enzyme in de novo biosynthesis of phosphatidylethanolamine (PE) from ethanolamine and diacylglycerol by the CDP-ethanolamine Kennedy pathway. Phosphorylation of ethanolamine by ethanolamine kinase (EK) to produce phosphoethanolamine is followed by the Pcyt2-mediated production of CDP-ethanolamine. The final reaction in this pathway is executed by CDP-ethanolamine:1,2-diacylglycerol ethanolaminephosphotransferase (EPT) to produce PE.
The CDP-ethanolamine branch of the Kennedy pathway is the major route for the formation of ethanolamine-derived phospholipids, including diacyl phosphatidylethanolamine and alkenylacyl phosphatidylethanolamine derivatives, known as plasmalogens. In the liver, PE can be transformed into phosphatidylcholine (PC) by the action of phosphatidylethanolamine N-methyltransferase (PEMT).
Phosphatidylethanolamine (PE) is the most abundant lipid on the protoplasmatic leaflet of cellular membranes. It has a pivotal role in cellular processes such as membrane fusion, cell cycle regulation, autophagy, and apoptosis.
3.2 Role as a Phosphomonoester and Precursor/Catabolite
Phosphomonoesters (PME) are composed of phosphocholine (PC) and phosphoethanolamine (PE), reflecting membrane synthesis, whereas phosphodiesters (PDE) are composed of glycerophosphocholine (GPC) and glycerophosphoethanolamine (GPE), which reflect lipid breakdown products. The ratio of PME to PDE is believed to reflect phospholipid turnover, and altered levels of lipids and lipid metabolism have been reported during normal aging and Alzheimer's disease.
3.3 Mitochondrial Involvement and Succinate Dehydrogenase Inhibition
Metabolic profiling has revealed a sharp increase in intracellular levels of phosphoethanolamine as an intermediate in the CDP-ethanolamine Kennedy pathway of phosphatidylethanolamine biosynthesis. Follow-up biochemical experiments confirmed the direct inhibition of CTP:phosphoethanolamine cytidylyltransferase (PCYT2), a rate-limiting enzyme of the CDP-ethanolamine Kennedy pathway. The inhibition of PCYT2 results in the buildup of its substrate (phosphoethanolamine), which itself directly inhibits mitochondrial respiration. This work identifies a novel link between the CDP-ethanolamine Kennedy pathway and mitochondrial respiration.
Mechanistic investigations have identified phosphoethanolamine as a competitive inhibitor of succinate dehydrogenase (complex II and the Krebs cycle), providing molecular rationale for its mitochondrial effects. This discovery opened new therapeutic avenues beyond oncology, particularly in ischemia-reperfusion injury, where phosphoethanolamine's succinate dehydrogenase inhibitory activity could mitigate pathological succinate accumulation.
3.4 PCYT2 Deficiency and Metabolic Consequences
PCYT2 is the key regulatory enzyme in the biosynthesis of phosphatidylethanolamine via the CDP-ethanolamine Kennedy pathway. Deficiencies in this gene have been linked to metabolic, neurological, and cardiac disorders; however, most studies report that PE levels remain unchanged. Physiological consequences of deletion of one Pcyt2 allele include development of symptoms of the metabolic syndrome such as elevated lipogenesis and lipoprotein secretion, hypertriglyceridemia, liver steatosis, obesity, and insulin resistance.
3.5 Structural Similarity to GABA
Phosphorylethanolamine shows a strong structural similarity to the inhibitory neurotransmitter GABA and the GABAB receptor partial agonist, 3-amino-propylphosphonic acid. The functional significance of this similarity in vivo has not been established in clinical studies.
4. Scientific Evidence by Health Area
4.1 Oncology: Phosphoethanolamine as a Tumor Biomarker
Magnetic resonance spectroscopy (MRS) studies have identified elevated levels of the phospholipid precursor phosphocholine (PC) and phosphoethanolamine (PE) as metabolic hallmarks of cancer. An elevation of PME (phosphomonoesters, which include PE) can often be seen in ³¹P-MR spectra of tumors, mainly because of enhanced cell membrane synthesis and cell proliferation. After proper treatment, a reduction in PME levels has been shown in subsequent studies.
The intra-tumoral content of the phospholipid-related metabolites phosphoethanolamine (Etn-P) and phosphocholine (Cho-P) has been shown to be increased in clinically aggressive malignant disease and to decrease with clinical response to anticancer therapy, suggesting that phospholipid metabolism may be an intrinsic component of oncogenesis.
All cancers tested so far display abnormal choline and ethanolamine phospholipid metabolism, detected with numerous MRS approaches in cells, animal models of cancer, and the tumors of cancer patients. Since the discovery of this metabolic hallmark of cancer, many studies have been performed to elucidate the molecular origins of deregulated choline metabolism, to identify targets for cancer treatment, and to develop MRS approaches that detect choline and ethanolamine compounds for clinical use in diagnosis and treatment monitoring.
Lipid analyses of samples from breast cancer tissue displayed an increase in phospholipid content compared to non-cancerous adjacent healthy breast tissue. Concentrations of the two major phospholipid components phosphatidylcholine and phosphatidylethanolamine increased with increasing breast cancer tumor grade, indicating that the phospholipid synthesis rate increases with oncogenesis and tumor progression.
Unusually, PC and PE levels are reduced in mutant isocitrate dehydrogenase 1 (IDHmut) gliomas that produce the oncometabolite 2-hydroxyglutarate (2-HG) relative to wild-type IDH1 (IDHwt) gliomas. This study identifies a direct role for 2-HG in the downregulation of choline kinase and ethanolamine kinase activity, and thereby PC and PE synthesis in IDHmut gliomas. This illustrates the heterogeneity of PE alterations across tumor subtypes.
Evidence strength (biomarker role): There is robust observational and in vitro/ex vivo evidence supporting elevated PE as a metabolic hallmark of many human cancers, and ³¹P-MRS measurement of PME (including PE) has been investigated in clinical settings as a treatment-response monitor. This constitutes established biochemical science, not a therapeutic claim about supplemental PE.
4.2 Oncology: Synthetic Phosphoethanolamine as a Proposed Anticancer Treatment
This area must be treated with clear distinction between preclinical findings and clinical evidence.
Preclinical Evidence
Phosphoethanolamine (Pho-s) is a compound involved in phospholipid turnover, acting as a substrate for many phospholipids of the cell membranes. Pre-clinical studies have shown that synthetic Pho-s has antitumor effects on several tumor cell lines. In one study, Pho-s was shown to be cytotoxic to MCF-7 breast cancer cells in a dose-dependent manner, while it was cytotoxic to normal MCF10 cells only at higher concentrations. Additionally, Pho-s was shown to induce a disruption in mitochondrial membrane potential and to induce mitochondria aggregates in the cytoplasm and DNA fragmentation of MCF-7 cells.
Pre-clinical studies have suggested that phosphoethanolamine is not toxic to healthy, cancer-free cells and may have some effect on some types of tumors: melanoma, breast, leukemia, liver, lung, kidney, bone, and glioblastoma (brain).
In a preclinical study of a related lipid precursor formulation (monoethanolamine), orally fed compound inhibited tumor growth by approximately 67% in mice bearing human prostate cancer PC-3 xenografts without apparent toxicity. Mechanistically, the compound was proposed to exploit selective overexpression of choline kinase in cancer cells, resulting in accumulation of phosphoethanolamine, accompanied by downregulation of HIF-1α, inducing metabolic stress culminating in cell death.
Human / Clinical Evidence
As a potential drug, phosphorylethanolamine has undergone human clinical trials. These were halted when no evidence of benefit was found. No clinical data on this substance have ever been published.
A cross-sectional survey of 1,072 Brazilian oncologists (with 398 responding) found that 115 (28.9%) had followed patients who had used phosphoethanolamine. Most oncologists in Brazil do not believe that synthetic phosphoethanolamine is active in cancer treatment, do not recommend its use without proper evaluation, and state that it should only be available to patients in the context of clinical trials.
Regulatory and Ethical Context
On April 14, 2016, a law was passed in Brazil allowing the use of synthetic phosphorylethanolamine for cancer treatment, despite opposition from the Brazilian Medical Association, the Brazilian Society of Clinical Oncology, and the regulatory agency ANVISA. Shortly after, Brazil's Supreme Court suspended the law.
Synthetic phosphoethanolamine, known as the "cancer pill," was distributed by court orders between 2015 and 2016 despite the absence of scientific proof of its safety and effectiveness. At the time, hundreds of lawsuits ordered cancer patients to be supplied with the drug before clinical trials concluded and without prior ANVISA approval.
ANVISA, the World Health Organization, Brazilian medical associations, clinical oncology researchers, and well-known medical oncologists have stated the experimental nature of phosphoethanolamine and the inappropriateness of its clinical use, as well as the threat posed by legislative action on this matter.
The crowd-pleasing measure overriding the authority of ANVISA was taken despite an absolute lack of any published scientific evidence that phosphoethanolamine was safe or effective for treating any cancer in humans.
Evidence strength (anticancer treatment): Preclinical evidence (cell lines, animal models) is present but limited and not independently replicated at scale. Human clinical trial data were never published. Completed clinical trials were halted without evidence of benefit. The compound is not approved as a cancer treatment by any regulatory authority worldwide. This area must be characterized as having no clinically established therapeutic evidence in humans.
4.3 Neurology: Alzheimer's Disease and Neurodegeneration
Phosphorylethanolamine shows a strong structural similarity to the inhibitory neurotransmitter GABA and the GABAB receptor partial agonist, 3-amino-propylphosphonic acid. Phosphorylethanolamine is a phosphomonoester which is decreased in post-mortem Alzheimer's disease (AD) brain.
In Alzheimer's disease (AD), defects in essential metabolic processes for energy supply and phospholipid membrane function have been implicated in the pathological process. Phosphomonoesters (PME) and phosphodiesters (PDE), components of membrane phospholipids, are quantifiable via ³¹P-MRS. PME are composed of phosphocholine (PC) and phosphoethanolamine (PE), reflecting membrane synthesis, whereas PDE are composed of glycerophosphocholine (GPC) and glycerophosphoethanolamine (GPE), which reflect lipid breakdown products.
The phosphomonoesters-to-phosphodiesters (PME/PDE) ratio in both the hippocampus and prefrontal gray matter exhibited a progressive increase along the healthy control–amnestic mild cognitive impairment–Alzheimer's disease continuum, and further analysis revealed an association between elevated PME/PDE ratios in these brain regions and the decline in cognitive function.
Studies have shown that changes in the abundance of phosphorylethanolamine are associated with Alzheimer's disease and Parkinson's disease.
Alterations of brain membrane phospholipid metabolism and neurochemistry have been associated with brain development, cancer, and a number of neurological disorders such as Alzheimer's disease, Parkinson's disease, schizophrenia, and multiple sclerosis.
Evidence strength (neurological associations): The association between altered phosphoethanolamine levels and neurodegenerative disease is grounded in observational ³¹P-MRS studies and post-mortem analyses. This evidence is biomarker-level and observational; there are no human interventional studies testing supplemental phosphoethanolamine for any neurological condition.
4.4 Metabolic Disorders and Insulin Signaling
Lowering the ratio of phosphorylethanolamine to phosphatidylcholine in the liver can improve insulin signaling. This finding is derived from pre-clinical (animal) models linked to PCYT2 regulation.
Consequences of deletion of one Pcyt2 allele in mice include development of symptoms of the metabolic syndrome such as elevated lipogenesis and lipoprotein secretion, hypertriglyceridemia, liver steatosis, obesity, and insulin resistance. These findings from Pcyt2 heterozygous knockout mouse models underscore the importance of the PE Kennedy pathway in metabolic homeostasis but do not directly translate to therapeutic effects of oral phosphoethanolamine supplementation.
Evidence strength (metabolic): Mechanistic and genetic animal data only; no human clinical trials of phosphoethanolamine supplementation for metabolic conditions have been reported.
4.5 Ischemia-Reperfusion Injury
Mechanistic discoveries regarding phosphoethanolamine have opened new therapeutic avenues beyond oncology, particularly in ischemia-reperfusion injury, where phosphoethanolamine's succinate dehydrogenase inhibitory activity could mitigate pathological succinate accumulation associated with tissue damage. This area remains at the preclinical, mechanistic stage.
Evidence strength: Preliminary, mechanistic, preclinical only.
5. Body Systems and Health Areas of Association
- Cell membranes (universal): Phosphorylethanolamine is a membrane phospholipid and an important precursor of phosphatidylcholine, playing a critical role in membrane integrity, cell division, and mitochondrial respiratory function.
- Central nervous system: Phosphomonoesters, including phosphoethanolamine, are present at much higher levels in the brain than in other organs. In the developing brain, phosphomonoesters are normally elevated during the period of neuritic proliferation.
- Oncological metabolism: All cancers tested so far display abnormal choline and ethanolamine phospholipid metabolism, detected with numerous MRS approaches in cells, animal models of cancer, and tumors of cancer patients. Many studies have been performed to elucidate the molecular origins of deregulated choline and ethanolamine metabolism, to identify targets for cancer treatment, and to develop MRS approaches for clinical use in diagnosis and treatment monitoring.
- Hepatic and metabolic systems: In the liver, PE can be transformed into phosphatidylcholine by the action of phosphatidylethanolamine N-methyltransferase (PEMT). Disruption of PCYT2-mediated PE synthesis in animal models leads to liver steatosis and dyslipidemia.
- Mitochondria: Accumulation of phosphoethanolamine directly inhibits mitochondrial respiration. This links the CDP-ethanolamine Kennedy pathway to mitochondrial respiration.
- Cardiovascular system: Deficiencies in PCYT2 — the key enzyme of the PE Kennedy pathway — have been linked to metabolic, neurological, and cardiac disorders.
6. Dosage Forms and Doses Reported in Studies
Phosphorylethanolamine is not an approved drug or licensed dietary supplement in any major jurisdiction. Dosage information below is drawn exclusively from reported research contexts.
- Oral administration (human, Phase 1 and Phase 2 safety studies, Brazil): Professor Paulo Marcelo Gehm Hoff led the first controlled studies of orally administered phosphoethanolamine salt, sponsored by the São Paulo State Government at the Cancer Institute of São Paulo State (ICESP). The salt was considered safe and proceeded to Phase 2. Together with phase two adverse events data, it can be concluded that oral administration of the salt was considered safe in humans at the tested dosages of 1.5 g/day, and no adverse effects were attributed to the use of phosphoethanolamine.
- Preclinical (animal) maximum tolerated dose: On the maximum dosage tolerated test, all dosages tested were safe and the animals showed no weight or nourishment pattern alteration; no significant hematological and biochemical alterations were noted. Overall, phosphoethanolamine oral supplementation was reported to be safe in pre-clinical assays.
- Genotoxicity panel (preclinical): In vitro genotoxicity evaluated with Salmonella typhimurium showed a mutagenic index less than 2 (not mutagenic). Micronucleus genotoxicity tests in accordance with OECD 471 guidelines did not observe genotoxicity at 8, 50, 320, and 2,000 mg/kg dosage. In vivo evaluation of cardio- and neurotoxicity of orally supplemented phosphoethanolamine showed neurological and cardiological safety.
No dosages have been established for any indication in approved clinical or pharmacopeial monographs.
7. Safety Considerations and Interactions
7.1 Preclinical Safety Profile
Pharmacological studies have revealed favorable safety profiles for phosphoethanolamine in preclinical settings, with an oral bioavailability of 6–7%. The low oral bioavailability means that most orally administered compound is not absorbed systemically.
Pre-clinical studies have suggested that phosphoethanolamine is not toxic to healthy, cancer-free cells and may have some selective effect on certain tumor cell types. However, it should be noted that "many compounds that produce good results in in vitro experiments do not have the same effect when tested on people."
7.2 Established Interaction: Mitochondrial Respiration
The inhibition of PCYT2 results in the buildup of phosphoethanolamine, which itself directly inhibits mitochondrial respiration. This mechanism — identified in the context of the antiemetic drug meclizine — highlights that pharmacological accumulation of phosphoethanolamine has the capacity to impair cellular energy production, an effect that would be relevant to any context in which intracellular phosphoethanolamine levels are substantially elevated.
7.3 Interaction with PCYT2 Inhibitors
Meclizine, an FDA-approved antiemetic drug, directly inhibits PCYT2 activity in a dose-dependent, non-competitive manner. This inhibition leads to a significant accumulation of the substrate phosphoethanolamine. This indicates a pharmacokinetic interaction: individuals taking meclizine would be expected to show altered phosphoethanolamine metabolism.
7.4 Regulatory and Clinical Status
The substance is not permitted or registered as a food supplement or medicine in Brazil. ANVISA informs the population that phosphoethanolamine is not authorized or registered as a food supplement or medicine in Brazil. The use of products not registered by ANVISA for cancer treatment is considered extremely risky; these products can negatively interfere with conventional therapies and pose a risk of contamination.
The manufacture and distribution of unproven drugs to patients outside the framework of a clinical trial, with proper study design, approval by IRB/EC, and with informed consent, infringes the ethical principles of clinical research and puts the health of patients at risk.
7.5 Interference with Conventional Cancer Treatment
The practice of using alternative therapies alongside conventional cancer treatment is risky as it can interfere with and hamper the effects of conventional treatment. No peer-reviewed data specifically quantify the interaction risk between oral phosphoethanolamine supplementation and conventional oncology agents. Given its mechanism of action on membrane phospholipid metabolism and mitochondrial respiration, interactions with agents affecting similar pathways cannot be excluded.
7.6 Summary of Evidence Quality
Most oncologists in Brazil do not believe that synthetic phosphoethanolamine is active in cancer treatment, do not recommend its use without proper evaluation, and state that it should only be available to patients in the context of clinical trials. As of the time of writing, the compound remains without regulatory approval in any jurisdiction for therapeutic use, and the halted clinical trials produced no published efficacy data.
8. Current Research Directions
Phosphoethanolamine, an endogenous metabolite in the Kennedy pathway for membrane phospholipid synthesis, gained clinical attention following reports of Brazilian cancer patients with phosphoethanolamine-containing products. Subsequent pharmacological studies revealed favorable safety profiles in preclinical and clinical settings.
Phosphorylethanolamine holds promise for research in the fields of cancer, neurodegenerative disorders, and metabolic diseases. Active research directions include its use as a quantitative ³¹P-MRS biomarker of tumor proliferation and treatment response, investigation of the PE Kennedy pathway as a target in cancer combination therapy (for example, through PCYT2 inhibition), and preliminary study of its role in ischemia-reperfusion injury models.
Data from preclinical studies indicate that phosphatidylethanolamine biosynthesis is a targetable pathway for cancer; meclizine may have clinical efficacy as a repurposed anti-cancer drug when used as part of a new combination therapy. This remains at an early experimental stage.
References
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