Endoxifen

Endoxifen

Endoxifen, chemically designated as 4-hydroxy-N-desmethyltamoxifen, is a synthetic triphenylethylene derivative and the primary active metabolite of the pioneering selective estrogen receptor modulator (SERM) tamoxifen. In classical endocrine research models, parent tamoxifen requires extensive hepatic bioactivation via the polymorphic cytochrome P450 2D6 (CYP2D6) enzyme pathway to achieve full potency.

Endoxifen completely bypasses this initial enzymatic step. Because it is supplied in its fully bioavailable, post-metabolic configuration, it acts as a direct, high-affinity ligand at both estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ) sites. This makes it an essential reference standard for evaluating hormone-responsive cellular matrices without the confounding experimental variables introduced by genetic CYP450 metabolic variations.

Structural Elements of Interest: Endoxifen retains the characteristic core triphenylethylene framework shared across the tamoxifen family, but features two critical modifications: an added hydroxyl (-OH) group at the para-position of one phenyl ring and the removal of a methyl group from the tertiary amine side chain (N-desmethylation). These optimized functional groups significantly alter its spatial alignment, allowing it to bind to the estrogen receptor pocket with up to 100-fold greater affinity than parent tamoxifen.

Physical & Handling Properties

Research Applications & Mechanism of Interest

The utility of Endoxifen within reproductive biology, oncology cell lines, and molecular endocrinology stems from its strong and predictable competitive target engagement.

Primary fields of preclinical and in vitro laboratory study include:

• Estrogen Receptor Signaling Kinetics: Investigating high-affinity competitive binding profiles at ERα and ERβ receptors to map the comparative displacement rates of endogenous estradiol.

• Transcriptional Inhibition Models: Tracking downstream signaling events where Endoxifen blocks estrogen-mediated gene transcription, suppressing the expression of estrogen-responsive target proteins.

• Tissue-Selective Agonist/Antagonist Profiling: Evaluating the complex structural behavior of coregulator recruitment to observe how the molecule alternates between estrogenic and anti-estrogenic profiles across varying tissue matrices.

• CYP-Independent Experimental Matrices: Serving as a definitive control in hormone-responsive cell line assays (such as MCF-7) to isolate pure SERM activity without the baseline interference of mixed metabolic conversion rates.

Storage & Handling Guidelines

Store at controlled room temperature. Keep tightly closed. Liquid formats: do not refrigerate or freeze. Cold storage may cause the solution to cloud or precipitate. If this occurs, return to room temperature and mix until clear.

Storage guidance is a house recommendation. Analytical documentation is per-lot release testing.

Related Research Compounds

• 4-Hydroxytamoxifen
• Y134
• Arimistane
• Enclomiphene

Analytical Documentation

Purity, identity, and composition vary by manufacturing lot. Kimera Chems does not publish a single fixed purity figure for this item; refer to the batch-specific Certificate of Analysis (COA) issued for the lot received, which reflects third-party analytical testing for that lot. Contact us if a COA for your lot is required.

Research Use Only Disclaimer: This product is labeled and sold "For Research Use Only — NOT FOR HUMAN CONSUMPTION." It is not a drug, dietary supplement, food, cosmetic, or medical device, and it is not approved by the FDA or any other regulator for human or veterinary use. It is supplied to approved account holders as a research chemical for laboratory use and must be handled in accordance with applicable law.