Exemestane is a steroidal, irreversible aromatase inactivator (type I AI). Its androst-1,4-diene-3,17-dione backbone allows it to bind the substrate-binding site of CYP19A1 and form a covalent adduct — permanently inactivating that aromatase molecule. New enzyme synthesis is required for oestrogen production to recover. Suppresses oestradiol ~85% at standard doses. Unlike anastrozole (reversible, type II), exemestane’s inactivation is permanent per enzyme molecule — different pharmacodynamic profile for research.
Also Known As
Aromasin, FCE 24304
Compound Class
Steroidal aromatase inactivator (type I AI)
Molecular Formula
C₂₀H₂₄O₂
Molecular Weight
296.40 Da
CAS Number
107868-30-4
Half-Life
~24 hours
Research Applications
Irreversible Aromatase Inactivation Research
Exemestane is the reference steroidal, irreversible AI. Used to study permanent vs reversible aromatase inhibition pharmacodynamics — enzyme activity recovery kinetics after discontinuation, residual activity, and dose-response are distinct from non-steroidal AIs.
Breast Cancer Research
TEAM trial, IES trial: exemestane in ER+ postmenopausal BC after 2-5 years tamoxifen. Provides distinct PD profile vs anastrozole/letrozole. Also studied in combination with everolimus (mTOR inhibitor) in advanced ER+ BC.
Androgen Precursor Activity
Unlike anastrozole, exemestane is itself a substrate analog. Its metabolite 17-hydroexemestane has mild androgenic activity at AR — relevant for bone density research (less bone loss than non-steroidal AIs in some studies). Unique dual mechanism research model.
Prevention Research
MAP.3 trial: exemestane 25mg/day in postmenopausal women at elevated BC risk — 65% relative risk reduction in ER+ invasive BC. Prevention-focused research model distinct from treatment models.
Key Research Data
Study / Source
Key Findings
IES Trial 2004 NEJM
N=4,742: switching to exemestane after 2-3y tamoxifen improved DFS vs continued tamoxifen — sequential AI therapy model
TEAM Trial 2011 Lancet Oncol
Exemestane vs tamoxifen upfront: comparable efficacy, different side effect profile — comparative endocrine therapy data
MAP.3 Prevention Trial 2011 NEJM
Exemestane 65% reduction in invasive ER+ BC vs placebo — prevention research reference
Specifications
Format
Oral tablet — 25mg per tablet
Purity
≥99% HPLC
Identity
MS confirmed
Storage
Room temperature
Inhibition type
Irreversible, steroidal (type I, vs anastrozole: reversible, type II)
Frequently Asked Questions
What is Exemestane (Aromasin)?
Exemestane (Aromasin) is a Steroidal aromatase inactivator (type I AI). Exemestane is a steroidal, irreversible aromatase inactivator (type I AI). Its androst-1,4-diene-3,17-dione backbone allows it to bind the substrate-binding site of CYP19A1 and form a covalent adduct — permanently inactivating that aromatase molecule…
How does Exemestane work in research models?
Exemestane is the reference steroidal, irreversible AI. Used to study permanent vs reversible aromatase inhibition pharmacodynamics — enzyme activity recovery kinetics after discontinuation, residual activity, and dose-response are distinct from non-steroidal AIs….
What makes Exemestane different from similar compounds?
TEAM trial, IES trial: exemestane in ER+ postmenopausal BC after 2-5 years tamoxifen. Provides distinct PD profile vs anastrozole/letrozole. Also studied in combination with everolimus (mTOR inhibitor) in advanced ER+ BC….
Does QSC ship Exemestane to the USA?
Yes. QSC Exemestane ships domestically across the USA and internationally to EU, UK, Canada, and Australia. Every batch carries a Janoshik third-party COA confirming ≥99% HPLC purity and MS identity verification.
