FP802 specifically targets the TwinF interface within the NMDAR/TRPM4 death signaling complex. This complex is formed by the physical coupling of the N-methyl-D-aspartate receptor (NMDAR) with the transient receptor potential cation channel subfamily M member 4 (TRPM4). The compound acts as a selective TwinF interface inhibitor, disrupting the pathological toxic signaling cascade initiated by extrasynaptic NMDARs (eNMDARs) while sparing the vital physiological functions of synaptic NMDARs (sNMDARs). FP802 effectively blocks the interaction between specific NMDAR subunits (GluN2B) and TRPM4 without affecting the total protein expression levels of these components. This unique mechanism allows for the safe and selective elimination of excitotoxicity, a primary driver of neurodegeneration in conditions like AD and ALS.

FP802 (8 μM, 24–72 h) effectively disrupts the NMDAR/TRPM4 complex and provides neuroprotection in cell models, but it does not directly promote or inhibit neurite growth [1]. FP802 (10 μM, 30 min) exhibits strong neuroprotective effects, resisting glutamate (20 μM)-mediated toxicity (IC50 = 8.7 µM) and restoring NMDA-inhibited early gene expression to physiological levels [2]. FP802 did not show antagonistic activity against NMDAR in HEK293 cells (IC50 of GluN1/GluN2A and GluN1/GluN2B were both > 250 mM) [2]. FP802 (30 min) was able to dose-dependently block NMDA-induced postmitotic death of neurons in sporadic ALS disease-specific induced pluripotent stem cell (iPSC)-derived forebrain organoids [2].

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In vitro, FP802 demonstrates potent neuroprotective activity by disrupting the NMDAR/TRPM4 complex. At a concentration of 10 uM, it exhibits strong neuroprotection against glutamate-mediated toxicity, with an IC₅0 of 8.7 uM. It was also able to restore NMDA-inhibited early gene expression to physiological levels and did not show direct antagonistic activity against NMDAR (IC₅0 > 250 mM), confirming its non-classical mechanism of action. Furthermore, FP802 dose-dependently blocked NMDA-induced neuronal death in human ALS patient-derived induced pluripotent stem cell (iPSC) forebrain organoids, highlighting its potential therapeutic translatability. An 8 uM concentration was shown to be effective in disrupting the toxic complex and providing neuroprotection without directly influencing neurite growth.

FP802 (10 and 40 mg/kg, epidermal, once daily for 4 months) improved cognitive function, prevented metastructural damage and reduced amyloid pathology in 5xFAD mice[1]. FP802 (40 mg/kg, subcutaneous injection, once daily for 4 weeks starting from week 15) safely prevented ALS motor neuron shortening and prolonged its survival through the NMDAR/TRPM4 complex[2].

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In vivo, FP802 has shown remarkable efficacy in both AD and ALS mouse models. In the 5xFAD Alzheimer's disease model, oral administration of FP802 (10 and 40 mg/kg daily for 4 months) improved cognitive function, prevented neuronal structural damage, reduced beta-amyloid plaque formation, and alleviated mitochondrial pathology. In the SOD1G93A ALS mouse model, FP802 (40 mg/kg, subcutaneous injection daily for 4 weeks) prevented motor neuron loss, reduced serum neurofilament light chain (NfL) levels, improved motor performance, and significantly extended the lifespan of the mice. No apparent adverse effects on major organs like the liver, kidney, or heart were observed.

The non-cellular mechanism-of-action studies for FP802 typically involve evaluating its ability to disrupt the physical interaction between NMDA receptor subunits and the TRPM4 channel. This is often demonstrated through co-immunoprecipitation assays. In such a protocol, protein lysates from treated animals or cells are incubated with antibodies targeting NMDAR subunits (e.g., GluN2B) to pull down the protein complexes. The presence of TRPM4 in these immunoprecipitated complexes is then detected via western blotting. For example, in treated 5xFAD mice, FP802 administration led to a significant reduction in the amount of TRPM4 co-precipitated with GluN2B, indicating a disruption of their physical complex formation.

Real Time qPCR[1]
Cell Types: mouse cortical neurons
Tested Concentrations: 10 μM
Incubation Duration: 30 min
Experimental Results: Eliminated the transcriptional shut-off induced by eNMDARs and boosted the NMDA bath application-induced expression of the immediate-early genes (IEGs) Atf3, Arc, Bdnf, cFos, Inhibin beta A, and Npas4 to reach levels that were comparable to those achieved by Bicuculline induced action potential bursting.

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In vitro cell-based assays use primary cortical neurons or iPSC-derived human brain organoids to model excitotoxicity. In a typical protocol, neuronal cultures are pre-treated with a concentration range of FP802 for 30 minutes, followed by exposure to a neurotoxic insult such as NMDA (e.g., 20 uM for 30-60 minutes) or glutamate to induce excitotoxic cell death. Cellular viability and death are then quantified using assays like lactate dehydrogenase (LDH) release or measures of metabolic activity (e.g., MTT). For gene expression analysis, cells are harvested after treatment and processed for real-time quantitative PCR (qPCR) to measure the expression of immediate-early genes like Atf3, Arc, Bdnf, cFos, and Npas4, which are known to be suppressed by eNMDAR activation.

Animal/Disease Models: 5xFAD transgenic mice and wild-type littermates[1]
Doses: 10 and 40 mg/kg
Route of Administration: p.o., daily for 4 months
Experimental Results: Showed no apparent adverse effects on the liver, kidney, or heart. Reduced the complex formation of GluN2B with TRPM4 in the 5xFAD mice at both 10 and 40 mg/kg. Reduced complex formation of GluN2A with TRPM4 at 40 mg/kg. Significantly decreased the interaction between NMDAR and TRPM4 without affecting the total protein levels of GluN2A, GluN2B, or TRPM4. Led to a significant increase in the time 5xFAD mice spent in the target quadrant and the frequency with which they crossed the platform's prior location at the dose of 40 mg/kg, compared to vehicle. Increased the time 5xFAD mice spent exploring the novel object in the Novel Object Recognition (NOR) test and the displaced object in the Novel Location Recognition (NLR) test relative to vehicle treatment. Prevented the shift of mitochondrial morphologies from normal to pathological phenotypes in both CA1 and CA3. Effectively preserved dendritic trees in 5xFAD mice as compared to controls, as demonstrated by increased total dendritic length and numbers of crossings in the Sholl analysis. Prevented the increase in the density of 'apparent orphaned synapses' in both stratum oriens (CA1 basal dendrites) and stratum radiatum (CA1 apical dendrites) of 5xFAD mice. Prevented the loss of excitatory and inhibitory synapses and the associated structural deterioration of postsynaptic densities (PSD) in the basal and apical dendrites of CA1 neurons, thereby preserving synaptic integrity in 5xFAD mice. Led to a 25-40% reduction in Aβ plaque load, significantly limiting plaque development without completely preventing its formation.

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Animal/Disease Models: Male SOD1G93A transgenic mice and wild-type littermates[2]
Doses: 40 mg/kg
Route of Administration: s.c., daily from ~week 15 for 4 weeks
Experimental Results: Disrupted he interaction of TRPM4 with the NMDAR subunit GluN2B in mice spinal cord. Significantly better neurological scores and less body weight loss than vehicle-treated controls. Significantly improved motor performance (increased total distance traveled and rearing frequency in the open field). Significantly extended the lifespan of SOD1G93A mice (survival median increased from 151 to 164 days). Preserved larger soma sizes of lumbar spinal motor neurons compared to the control group at week 19. Significantly reduced serum NfL levels while showing no effect on spinal microglial response or EAAT2 expression. Showed no adverse effects on liver, kidney, heart, or blood counts.

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The primary in vivo animal studies for FP802 are conducted using two established disease models. For ALS research, the SOD1G93A transgenic mouse model is used, where disease onset begins around 15 weeks of age. Treatment is administered subcutaneously at a dose of 40 mg/kg once daily for four weeks starting from week 15. Endpoints include histopathological analysis of motor neuron counts, measurement of serum neurofilament light chain (NfL) levels via immunoassay, assessment of motor performance, and overall survival analysis. For AD research, the 5xFAD transgenic mouse model is used. FP802 is administered orally at doses of 10 or 40 mg/kg once daily for 4 months. Endpoints include cognitive behavioral tests, histopathological analysis of amyloid plaque burden and mitochondrial morphology, and protein biochemistry to measure complex formation.

Pharmacokinetic data from publicly available sources are limited, but FP802 is described as an orally effective compound in animal models, confirming its oral bioavailability. Its molecular weight of 212.72 g/mol and its chemical properties suggest it is likely to cross the blood-brain barrier, a critical requirement for a CNS-active drug. The compound has shown a favorable safety profile in murine studies, with no reported adverse effects on vital organs at therapeutic doses of up to 40 mg/kg. For long-term storage, the compound should be kept at -20degC as a powder, and solutions should be stored at -80degC to maintain stability.

The Safety Data Sheet for FP802 indicates that the compound is classified under GHS as Acute Toxicity Category 4 for oral exposure (H302: Harmful if swallowed). It also presents environmental hazards, classified as Acute Aquatic Toxicity Category 1 (H400) and Chronic Aquatic Toxicity Category 1 (H410: Very toxic to aquatic life with long-lasting effects). Precautionary statements include washing skin thoroughly after handling (P264), not eating, drinking, or smoking when using the product (P270), avoiding release to the environment (P273), and collecting spillage (P391). In case of accidental ingestion, do not induce vomiting and call a physician immediately.

[1]. The NMDAR/TRPM4 death complex is a major promoter of disease progression in the 5xFAD mouse model of Alzheimer's disease. Mol Psychiatry. 2025 Aug 26.

[2]. TwinF interface inhibitor FP802 stops loss of motor neurons and mitigates disease progression in a mouse model of ALS. Cell Rep Med. 2024 Feb 20;5(2):101413.

FP802 is a research-grade compound and has not yet been approved by any regulatory authority (FDA, EMA, etc.) for human therapeutic use. It is an investigational new drug that has successfully completed preclinical proof-of-concept studies and is being prepared for entry into human clinical trials. Its mechanism of action is through selective TwinF interface inhibition, a unique class of neuroprotection that does not block the NMDAR channel directly but instead disrupts its pathological coupling with TRPM4. This mechanism was pioneered by Professor Hilmar Bading and is being developed by the biotech company FundaMental Pharma GmbH for the treatment of neurodegenerative diseases. The compound is available from various chemical suppliers solely for laboratory research purposes and is not for clinical use.

C11H17CLN2

212.72

212.108

61694-81-3

FP802 dihydrochloride

12861871

Typically exists as solids at room temperature

1

5

14

152

0

CCN(CCN)CC1=CC(=CC=C1)Cl

CEGPYWJJEVYOQS-UHFFFAOYSA-N

InChI=1S/C11H17ClN2/c1-2-14(7-6-13)9-10-4-3-5-11(12)8-10/h3-5,8H,2,6-7,9,13H2,1H3

N'-[(3-chlorophenyl)methyl]-N'-ethylethane-1,2-diamine

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)