What is the difference between Arimistane and Endoxifen?

Arimistane: Arimistane is a non-peptide C19 steroidal compound (androstane-based) marketed as a mechanism-based aromatase inhibitor and sold as a gray-market bodybuilding supplement ingredient. It is a 7-keto-DHE... Endoxifen: Endoxifen is a non-steroidal triphenylethylene selective estrogen receptor modulator (SERM) and the active secondary metabolite of tamoxifen. It is not FDA-approved and remains investigational, studie...

What does the research say about Arimistane vs Endoxifen?

Arimistane: No registered efficacy or safety clinical trials exist for arimistane. The only human data are two small anti-doping analytical studies: (1) a single 25 mg oral dose in 3 healthy volunteers produced up to 15 novel urinary metabolites, with parent compound detected in the sulfate fraction and no relevant acute effects on the steroid profile; (2) a s… Endoxifen: No FDA approval or approval in any jurisdiction; endoxifen is investigational only. Human trials: Goetz et al. 2017 Phase 1 in endocrine-refractory metastatic ER-positive breast cancer (20–160 mg/day oral, no maximum tolerated dose, 3 partial responses, clinical benefit rate 26.3%); Takebe et al. 2021 Phase 1 in gynecologic, desmoid, and hormone-re…

Arimistane vs Endoxifen

Q: Can you stack Arimistane and Endoxifen?

Arimistane (hormone) and Endoxifen (hormone) are in the same category and may have overlapping mechanisms — researchers should review both profiles carefully before combining. Consult a licensed provider before combining any compounds.

Head-to-head comparison of Arimistane and Endoxifen — mechanism, dosing, side effects, legal status, and pricing.

Arimistane

Arimistane is a non-peptide C19 steroidal compound (androstane-based) marketed as a mechanism-based aromatase inhibitor and sold as a gray-market bodybuilding supplement ingredient. It is a 7-keto-DHEA metabolite/degradation product with no approved therapeutic use. The FDA determined in 2021 that arimistane does not meet the definition of a dietary ingredient and fails GRAS criteria for food use. It is prohibited under the WADA Prohibited List (Section S4, Aromatase Inhibitors) and was added to the list in 2017.

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Endoxifen

Endoxifen is a non-steroidal triphenylethylene selective estrogen receptor modulator (SERM) and the active secondary metabolite of tamoxifen. It is not FDA-approved and remains investigational, studied in multiple Phase 1 and Phase 2 human trials for endocrine-refractory ER-positive breast cancer, desmoid tumors, and other hormone-receptor-positive solid tumors. Endoxifen is sold by research-chemical suppliers labeled for laboratory use only, not for human consumption.

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Arimistane

Endoxifen

Category

Hormone

Legal Status

Research Only

Mechanism

Arimistane is a C19 steroid bearing 7,17-diketone groups on an androsta-3,5-diene core, marketed as a mechanism-based ("suicide") irreversible aromatase inhibitor. Direct enzyme-kinetics data (Ki, kinact) specifically for arimistane were not found in primary literature; the closest sourced data are for near-neighbor steroids: androst-5-ene-7,17-dione (differing only in lacking the 3,4-double bond) acts as a time-dependent, NADPH-dependent suicide substrate of human placental aromatase in vitro (Ki ~0.14–35 µM, kinact ~0.036–0.19/min), and a series of androsta-3,5-dien-7-ones/androst-5-en-7-ones competitively inhibited aromatase with Ki 0.058–45 µM (17-oxo forms more potent than 17-beta-ols). These class data support the aromatase-inhibitor assignment but do not confirm kinetics for arimistane itself.

Endoxifen exerts dual mechanisms: (1) ER-alpha antagonism—binds estrogen receptor alpha at nanomolar concentrations, blocks estrogen-stimulated transcription, and uniquely promotes proteasomal degradation of ER-alpha in MCF7 breast cancer cells in vitro, unlike tamoxifen or 4-hydroxytamoxifen. (2) At clinically relevant concentrations, endoxifen inhibits protein kinase C beta-1 (PKC-beta-1), induces PKC-beta-1 degradation, reduces PKC-beta-1-driven AKT Ser473 phosphorylation, and induces apoptosis in ER-alpha-positive breast cancer cells in vitro—proposed as an ER-alpha-independent second mechanism.

Dose Range

No validated human dose

Where Researchers Are Buying

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Arimistane

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Endoxifen

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$0.062/mg

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Lab Verification

COA corpus from Disclosed Labs — independently tested batches only.

Arimistane

No COA data yet.

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Endoxifen

COAs

99.5%

Avg purity

Labs

Full testing data

Arimistane Research Summary

No registered efficacy or safety clinical trials exist for arimistane. The only human data are two small anti-doping analytical studies: (1) a single 25 mg oral dose in 3 healthy volunteers produced up to 15 novel urinary metabolites, with parent compound detected in the sulfate fraction and no relevant acute effects on the steroid profile; (2) a separate single-dose study (3 volunteers, up to 10 hours) identified 12 additional reduced/hydroxylated urinary metabolites and detected unchanged parent in urine. In vitro (human placental microsomes): the close analog androst-5-ene-7,17-dione is a time-dependent, NADPH-dependent suicide substrate of aromatase; a series of related androsta-3,5-dien-7-ones/androst-5-en-7-ones competitively inhibited aromatase (Ki 0.058–45 µM), with 17-oxo derivatives more potent than 17-beta-hydroxy derivatives. Arimistane itself was not unambiguously confirmed among the specific tested compounds in the latter study.

Key references

Endoxifen Research Summary

No FDA approval or approval in any jurisdiction; endoxifen is investigational only. Human trials: Goetz et al. 2017 Phase 1 in endocrine-refractory metastatic ER-positive breast cancer (20–160 mg/day oral, no maximum tolerated dose, 3 partial responses, clinical benefit rate 26.3%); Takebe et al. 2021 Phase 1 in gynecologic, desmoid, and hormone-receptor-positive solid tumors (20–360 mg/day, no MTD, partial responses in desmoid tumors); Alliance A011203 randomized Phase 2 found Z-endoxifen not superior to tamoxifen overall but showed PFS benefit in CDK4/6-inhibitor-naive patients (HR 0.42). Preclinical: in ovariectomized mice, oral Z-endoxifen increased cancellous and cortical bone mass; in rats, reduced bone turnover and protected against bone loss; in MCF7 xenografts, showed superior antitumor activity versus tamoxifen, letrozole, and exemestane.

Can you stack Arimistane and Endoxifen?

Arimistane and Endoxifen are both in the Hormone category and may have overlapping mechanisms. Researchers should review both profiles carefully, understand the mechanisms of action, and monitor the relevant biomarkers when combining compounds in the same class. As always, consult a licensed healthcare provider before making any decisions about combining research compounds.

Other comparisons

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This platform provides informational tools only, not medical advice. This comparison is for educational purposes only. Consult a licensed provider.