Approval Probability
TA Base Rate
Adjusted LOA
ML Risk
Also known as (Z)-endoxifen, Topical endoxifen
endoxifen · 3 trials · 6 indications
Incidence, severity, seriousness, and relationship of TEAEs and SAEs; clinically significant changes in laboratory tests, vital signs, ECGs, physical examinations, growth, pubertal development, and other targeted safety parameters.
(Z)-endoxifen steady-state plasma concentrations (Css) of evaluable subjects who completed at least one cycle of treatment (28 +/- 3 days)
For analysis Cohort A (subjects that have a baseline Ki-67\>10%): the primary objective is to determine whether the Week 4 Ki-67 ≤ 10% rate is at least 65% among premenopausal women with primary estrogen receptor positive (ER+), Human Epidermal Growth Factor Receptor 2 negative (HER2-) breast cancer.
For analysis Cohort B (subjects have baseline Ki-67≤ 10%): the primary objective is to determine the objective tumor response rate at 24 weeks among premenopausal women with ER+, HER2-, Ki-67 ≤ 10% breast cancer receiving (Z) endoxifen plus goserelin.
Change, on an individual level, in mammographic breast density, measured at 6 months or when exiting from the study (baseline screening mammography)
| Arm | Type | Description |
|---|---|---|
| (Z)-endoxifen arm | EXPERIMENTAL | - |
| PK Cohort | EXPERIMENTAL | (Z)-endoxifen capsules orally once daily for 4 weeks. Initial (Z)-endoxifen dose evaluated will be 40 mg with an option to evaluate 20 mg or 80 mg. The PK Cohort participants may extend treatment based on Ki-67% at Week 4. If Ki-67 ≤ 10% at Week 4, participant will be offered option to continue on this treatment for up to 6 cycles/Week 24. Each cycle is 28 days. If Ki-67 \> 10% at Week 4, participant will be withdrawn and go on to surgery. |
| Treatment Cohort - Single Treatment Arm | EXPERIMENTAL | (Z)-endoxifen 40mg capsules orally once daily for 4 weeks + goserelin 3.6 mg by subcutaneous implant approximately every 28 days. (Z)-endoxifen 40mg dose based on results of PK Cohort. If Ki-67 ≤ 10% at Week 4, continue on this treatment for up to 6 cycles/Week 24. Each cycle is 28 days. And then go on to surgery within 3 weeks of Cycle 6 day 26. If Ki-67 \> 10% at Week 4, participant will complete early termination assessments. |
| PK Cohort 80 mg | EXPERIMENTAL | (Z)-endoxifen 80 mg capsules orally once daily for 4 weeks. The PK Cohort participants may extend treatment based on Ki-67% at Week 4. If Ki-67 ≤ 10% at Week 4, participant will be offered option to continue on this treatment for up to 6 cycles/Week 24. Each cycle is 28 days. If Ki-67 \> 10% at Week 4, participant will be withdrawn and go on to surgery. |
| PK Cohort 80 mg + OFS | EXPERIMENTAL | (Z)-endoxifen 80 mg capsules orally once daily for 4 weeks + goserelin 3.6 mg by subcutaneous implant approximately every 28 days. The PK Cohort participants may extend treatment based on Ki-67% at Week 4. If Ki-67 ≤ 10% at Week 4, participant will be offered option to continue on this treatment for up to 6 cycles/Week 24. Each cycle is 28 days. If Ki-67 \> 10% at Week 4, participant will be withdrawn and go on to surgery. |
| Control | PLACEBO_COMPARATOR | Topical Placebo:Transcutol™ (2-(2-Ethoxyethoxy)ethanol); isopropanol, Crodamol™ GTCC (a fully saturated emollient triester) and mineral oil |
| Topical Endoxifen 10mg/breast/day | ACTIVE_COMPARATOR | 10 mg/day topical (Z)-endoxifen; Transcutol™ (2-(2-Ethoxyethoxy)ethanol); isopropanol, Crodamol™ GTCC (a fully saturated emollient triester) and mineral oil |
| Topical Endoxifen 20mg/breast/day | ACTIVE_COMPARATOR | 20 mg/day topical (Z)-endoxifen; Transcutol™ (2-(2-Ethoxyethoxy)ethanol); isopropanol, Crodamol™ GTCC (a fully saturated emollient triester) and mineral oil |
| Name | Type | Description |
|---|---|---|
| (Z)-endoxifen | DRUG | (Z)-endoxifen will be administered once daily via the oral route |
| goserelin | DRUG | goserelin 3.6 mg subcutaneous implant |
| Topical endoxifen | DRUG | topical solution |
| Placebo | DRUG | topical |
Inclusion Criteria: 1. Female child aged ≥ 4 to \< 10 years at the time of informed consent. 2. Body weight ≥ 16 kg. 3. Clinical or molecular diagnosis of McCune-Albright syndrome (MAS), with peripheral precocious puberty and at least one additional characteristic manifestation of MAS other than ca...
Endoxifen is an investigational small molecule being studied in breast neoplasms, mammographic breast density, and gonadotropin-dependent precocious puberty. Atossa Therapeutics is developing it across these indications, with clinical work focused on estrogen receptor positive breast cancer and related conditions. It is not approved for any use and remains in clinical development.
Endoxifen targets the estrogen receptor, or ER. It is a small molecule directed at ER, and the clinical programs are biomarker selected, meaning patients are chosen based on ER status. This target focus underlies its study in estrogen receptor positive breast cancer and in breast density, which is also estrogen driven.
Endoxifen is being developed by Atossa Therapeutics, Inc., which trades under the ticker ATOS. The company sponsors the clinical programs for the drug across breast cancer, mammographic breast density, and precocious puberty indications.
Endoxifen is in Phase 2 clinical development. It is investigational and has not been approved by the FDA for any indication. The Phase 2 programs cover estrogen receptor positive, HER2 negative breast cancer, mammographic breast density, and gonadotropin-dependent precocious puberty associated with McCune-Albright syndrome.
Endoxifen has been studied in three Phase 2 trials. NCT05607004 is evaluating (Z)-endoxifen in premenopausal women with ER+/HER2- breast cancer and is active but not recruiting. NCT04616430 tested topical endoxifen in women with mammographic breast density and is completed. NCT07869732 will study (Z)-endoxifen in girls with MAS-associated peripheral precocious puberty and is not yet recruiting.
Yes. Endoxifen is also known as (Z)-endoxifen and topical endoxifen. The (Z)-endoxifen name appears in the breast cancer and precocious puberty trials, while topical endoxifen refers to the formulation studied in mammographic breast density. All three names refer to the same Atossa Therapeutics drug candidate.