Afimoxifene
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| Drug class: | SERM |
| Route of administration: | Transdermal hydroalcoholic gel, 0.05% w/v[footnote 1][1] |
| Dosage range: | Gel: 2mg - 4mg [2][1] |
| Brand names: | TamoGel (in development) |
Afimoxifene (4-hydroxytamoxifen; TamoGel; ZB497; 4-OHT; BHR-700) is a SERM. It is one of the active metabolites of tamoxifen. It is delivered topically as a gel that is applied directly to the breast. Unlike oral SERMs such as tamoxifen or raloxifene, it is not highly systemic: its effects are mostly local to the breast.[2][footnote 2][1]
Application to non-binary transition
Some non-binary people desire feminization without breast growth, and Afimoxifene may be an option for them. It may allow AMAB people to take an antiandrogen and/or estrogen while preventing breast growth and/or tenderness, and allow the same for AFAB people who would otherwise experience the same due to puberty.
Open question
Does afimoxifene prevent breast growth in people with female-typical estrogen levels? There is some evidence that it might, as it has been shown to effectively treat moderate-to-severe breast pain in premenopausal women.[2][footnote 3][1]
Availability
Not generally available. As of 2018, it is only available from research chemical suppliers.
Safety
Uncertain. As of 2018, no large scale clinical trials have been completed.[3] There is phase-III trial in progress for reduction of breast tissue density in women. It is expected to complete in 2020.[4]
Speculation
The following is speculation. There is no experimental evidence to support this.
It is unlikely to have any side effects that tamoxifen doesn't have, as tamoxifen metabolizes into afimoxifene in the body. Furthermore, because it is not highly systemic, it is unlikely to have side effects in areas other than the breast.
Tamoxifen is a known carcinogen in uterine tissue.[5][6] While the low systemicity of topical afimoxifene suggests that the risk of cancer would be lower than that of tamoxifen, it would be good to exercise caution, especially in those with a uterus.
References
- ↑ 1.0 1.1 1.2 1.3 Mansel, R., Goyal, A., Nestour, E.L. et al. A phase II trial of Afimoxifene (4-hydroxytamoxifen gel) for cyclical mastalgia in premenopausal women. Breast Cancer Res Treat (2007) 106: 389. https://doi.org/10.1007/s10549-007-9507-x
- ↑ 2.0 2.1 2.2 A Goyal, R Mansel, E Le Nestour and V Masini-Etévé. Topical tamoxifen gel (afimoxifene) is associated with low plasma levels of 4-OHT while achieving therapeutic local antiestrogenic effect in premenopausal women with cyclical mastalgia. Cancer Res January 15 2009 (69) (2 Supplement) 2154; https://dx.doi.org/10.1158/0008-5472.SABCS-2154
- ↑ DrugBank. Afimoxifene. https://www.drugbank.ca/drugs/DB04468
- ↑ BHR Pharma, LLC. Trial of 4-OHT Gel in Women Aimed at Reducing Dense Breast Tissue (4WARD). https://clinicaltrials.gov/ct2/show/NCT03199963
- ↑ American Cancer Society. Known and Probable Human Carcinogens. https://www.cancer.org/cancer/cancer-causes/general-info/known-and-probable-human-carcinogens.html
- ↑ David H. Phillips; Understanding the genotoxicity of tamoxifen?, Carcinogenesis, Volume 22, Issue 6, 1 June 2001, Pages 839–849, https://doi.org/10.1093/carcin/22.6.839
Footnotes
- ↑ Weight/volume, i.e., 0.5 mg afimoxifene per 1 mL gel.
- ↑ "Topical application avoids high systemic exposure to 4-OHT compared with oral tamoxifen, a 16-18-fold difference, thus potentially reducing the risk of systemic side-effects."
- ↑ "Afimoxifene is an effective treatment for moderate-to-severe mastalgia in premenopausal women and has the potential to be used for breast cancer chemoprevention/gynecomastia in the future."