Fulvestrant

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Cat Number

API129453618

CAS Number

129453-61-8

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Product Detail Description Scientific Support Customer Q&A

CAS Number

129453-61-8

EINECS

642-998-6

Storage

Store at 2-8°C

Synonyms

Faslodex; ICI-182780; ZD-9238; DTXSID4022369; fulvestrantum; ZD9238

Molecular Formula

C32H47F5O3S

Molecular Weight

606.8

Smiles

C[C@]12CC[C@H]3[C@H]([C@@H]1CC[C@@H]2O)[C@@H](CC4=C3C=CC(=C4)O)CCCCCCCCCS(=O)CCCC(C(F)(F)F)(F)F

Appearance

White powder

Melting Point

104-106°C

Boiling Point

674.8±55.0°C at 760 mmHg (Predicted)

Relative Density

1.201±0.06 (Predicted)

General Description

Fulvestrant is a synthetic steroid with a long alkyl side chain, a selective estrogen receptor degrader (SERD), belonging to the class of 7α-alkylestradiol derivatives. Its chemical structure is 7α-[9-(4,4,5,5,5-pentafluoropentylsulfinyl)nonyl]estra-1,3,5(10)-triene-3,17β-diol.

Mechanism of Action

Fulvestrant acts as a pure anti-estrogen by binding to the estrogen receptor with high affinity, and preventing its dimerization and nuclear translocation. It also accelerates the degradation of the estrogen receptor, leading to a complete blockade of estrogen signaling. The drug has no agonist activity, unlike tamoxifen.

Application

Fulvestrant is indicated for the treatment of hormone receptor-positive (HR+) metastatic breast cancer in postmenopausal women who have progressed on prior endocrine therapy, such as tamoxifen or aromatase inhibitors. It is also used for the treatment of breast cancer in men and for the management of breast cancer in patients with resistance to other endocrine agents.

This review of 28 studies on fulvestrant plus targeted therapies for hormone receptor‑positive advanced breast cancer found that combinations with CDK4/6 inhibitors or PI3K/mTOR inhibitors improved progression‑free survival over fulvestrant alone. Toxicities were manageable. Selection should consider prior therapy and tumor mutation status. The data support combining fulvestrant with agents targeting endocrine resistance, with ongoing trials expected to refine treatment choices.

Fig. 1 Growth factor receptor signaling and the PI3K, mTOR, MAPK, ER, and CDK4/6 pathways in ER+ breast cancer. (Sammons S, et al., 2019)

References

Sammons S, et al. Fulvestrant-Based Combination Therapy for Second-Line Treatment of Hormone Receptor-Positive Advanced Breast Cancer. Target Oncol. 2019;14(1):1-12.

Does Fulvestrant require protection from light during long-term storage?

Yes, it is photosensitive. UV exposure can cause photodegradation of the long alkyl side chain. Store in light-resistant containers, preferably amber glass.

What is the recommended storage temperature for Fulvestrant?

Store at 2-8°C (refrigerated). At room temperature, degradation via oxidation and isomerization of the steroid ring occurs.

Is Fulvestrant stable in solution for intramuscular injection?

Formulated solutions are stable when protected from light and stored under refrigeration.

How is the impurity fulvestrant 17β-diol (a degradation product) monitored?

This degradation product is specifically quantified using a stability-indicating HPLC method, ensuring it remains within ICH limits.