A selective estrogen receptor degrader or downregulator (SERD) is a type of drug that selectively binds to the estrogen receptor (ER) and induces its degradation, and thus causes its downregulation. [1] SERDs are used in the treatment of estrogen receptor-positive breast cancer, particularly in cases where tumors have developed resistance to other forms of endocrine therapy, such as selective estrogen receptor modulators (SERMs) or aromatase inhibitors. [1]
The mechanism of action of SERDs involves binding to the estrogen receptor, leading to a conformational change that facilitates recruitment of cellular machinery to degrade the receptor protein. By promoting degradation of the estrogen receptor, SERDs effectively inhibit estrogen signaling within cancer cells, thereby suppressing tumor growth.
A common SERD used in clinical practice is fulvestrant. Fulvestrant is administered as an intramuscular injection and is indicated for the treatment of advanced breast cancer in postmenopausal women whose cancer has progressed following anti-estrogen therapy.
As of 2016 the only marketed SERD was fulvestrant (brand name Faslodex). [1] As of November 2016 other SERDs under development include brilanestrant and elacestrant. [2] The clinical success of fulvestrant led to efforts to discover and develop a parallel drug class of selective androgen receptor degraders (SARDs). [2]
Fulvestrant requires large-volume and frequently painful intramuscular injections. [3] In response, pharmaceutical companies are currently developing oral SERDs. Among products in development are: [4]
Monofunction (ER ligand) hydrophobic tag degradation:
Modality | INN | Research Code | Sponsor | Comment |
---|---|---|---|---|
hydrophobic tag | Amcenestrant | SAR 439859 | Sanofi | |
" | Bexirestrant | Menarini | ||
" | Brilanestrant | Genentech | ||
" | Camizestrant | AZD9833 | AstraZeneca | |
" | Elacestrant | Radius | ||
" | Etacstil | GW-5638 | Bristol Myers-Squibb | combined SERM and SERD |
" | Giredestrant | Roche | ||
" | Imlunestrant | LY3484356 | Eli Lilly | |
" | Palazestrant | OP-1250 | Olema Pharmaceuticals | |
" | Rintodestrant | G1T48 | G1 Therapeutics | |
" | Taragarestrant | D-0502 | Inventisbio | |
" | LSZ102 | Novartis | ||
" | SHR9549 | Jiangsu Hengrui | ||
" | H3B-6545 | Eisai Co Ltd | SERCA | |
" | ZB716 | EnhancedBio/Zenopharm | Fulvestrant boronic acid | |
" | ZN-c5 | Zentalis | ||
Vepdegestrant | ARV-471 | Arvinas | ||
" | AC 699 | Accutar Biotechnology |
The oral SERDs target ER-positive/HER2-negative breast cancer and are tested as monotherapy and in combination with other drugs such as the CDK inhibitor palbociclib (Ibrance). [5] [6] [7]
Fulvestrant, sold under the brand name Faslodex among others, is an antiestrogenic medication used to treat hormone receptor (HR)-positive metastatic breast cancer in postmenopausal women with disease progression as well as HR-positive, HER2-negative advanced breast cancer in combination with abemaciclib or palbociclib in women with disease progression after endocrine therapy. It is given by injection into a muscle.
Lapatinib (INN), used in the form of lapatinib ditosylate (USAN) is an orally active drug for breast cancer and other solid tumours. It is a dual tyrosine kinase inhibitor which interrupts the HER2/neu and epidermal growth factor receptor (EGFR) pathways. It is used in combination therapy for HER2-positive breast cancer. It is used for the treatment of patients with advanced or metastatic breast cancer whose tumors overexpress HER2 (ErbB2).
Formestane, formerly sold under the brand name Lentaron among others, is a steroidal, selective aromatase inhibitor which is used in the treatment of estrogen receptor-positive breast cancer in postmenopausal women. The drug is not active orally, and was available only as an intramuscular depot injection. Formestane was not approved by the United States FDA and the injectable form that was used in Europe in the past has been withdrawn from the market. Formestane is an analogue of androstenedione.
Hormonal therapy in oncology is hormone therapy for cancer and is one of the major modalities of medical oncology, others being cytotoxic chemotherapy and targeted therapy (biotherapeutics). It involves the manipulation of the endocrine system through exogenous or external administration of specific hormones, particularly steroid hormones, or drugs which inhibit the production or activity of such hormones. Because steroid hormones are powerful drivers of gene expression in certain cancer cells, changing the levels or activity of certain hormones can cause certain cancers to cease growing, or even undergo cell death. Surgical removal of endocrine organs, such as orchiectomy and oophorectomy can also be employed as a form of hormonal therapy.
Breast cancer management takes different approaches depending on physical and biological characteristics of the disease, as well as the age, over-all health and personal preferences of the patient. Treatment types can be classified into local therapy and systemic treatment. Local therapy is most efficacious in early stage breast cancer, while systemic therapy is generally justified in advanced and metastatic disease, or in diseases with specific phenotypes.
Antiestrogens, also known as estrogen antagonists or estrogen blockers, are a class of drugs which prevent estrogens like estradiol from mediating their biological effects in the body. They act by blocking the estrogen receptor (ER) and/or inhibiting or suppressing estrogen production. Antiestrogens are one of three types of sex hormone antagonists, the others being antiandrogens and antiprogestogens. Antiestrogens are commonly used to stop steroid hormones, estrogen, from binding to the estrogen receptors leading to the decrease of estrogen levels. Decreased levels of estrogen can lead to complications in sexual development.
Antihormone therapy is a type of hormone therapy that suppresses selected hormones or their effects, in contrast with hormone replacement therapy, which encourages hormone activity.
A hormone-receptor-positive (HR+) tumor is a tumor which consists of cells that express receptors for certain hormones. The term most commonly refers to estrogen receptor positive tumors, but can also include progesterone receptor positive tumors. Estrogen-receptor-positive tumors depend on the presence of estrogen for ongoing proliferation.
A CDK inhibitor is any chemical that inhibits the function of CDKs. They are used to treat cancers by preventing overproliferation of cancer cells. The US FDA approved the first drug of this type, palbociclib (Ibrance), a CDK4/6 inhibitor, in February 2015, for use in postmenopausal women with breast cancer that is estrogen receptor positive and HER2 negative. While there are multiple cyclin/CDK complexes regulating the cell cycle, CDK inhibitors targeting CDK4/6 have been the most successful; four CDK4/6 inhibitors have been FDA approved. No inhibitors targeting other CDKs have been FDA approved, but several compounds are in clinical trials.
Palbociclib, sold under the brand name Ibrance among others, is a medication developed by Pfizer for the treatment of HR-positive and HER2-negative breast cancer. It is a selective inhibitor of the cyclin-dependent kinases CDK4 and CDK6. Palbociclib was the first CDK4/6 inhibitor to be approved as a cancer therapy.
Buparlisib is an experimental anti-cancer medication. It is a small molecule orally-available pan-class I phosphoinositide 3-kinase (PI3K) inhibitor. Buparlisib was under investigation as a treatment for advanced breast cancer but was abandoned due to negative results. It is still under investigation as a potential treatment for head and neck squamous cell carcinoma (HNSCC).
Abemaciclib, sold under the brand name Verzenio among others, is a medication for the treatment of advanced or metastatic breast cancers. It was developed by Eli Lilly and it acts as a CDK inhibitor selective for CDK4 and CDK6.
Ribociclib, sold under the brand name Kisqali, is a medication used for the treatment of certain kinds of breast cancer. Ribociclib is a kinase inhibitor. It was developed by Novartis and Astex Pharmaceuticals.
Brilanestrant (INN) is a nonsteroidal combined selective estrogen receptor modulator (SERM) and selective estrogen receptor degrader (SERD) that was discovered by Aragon Pharmaceuticals and was under development by Genentech for the treatment of locally advanced or metastatic estrogen receptor (ER)-positive breast cancer.
Elacestrant, sold under the brand name Orserdu, is a selective estrogen receptor degrader (SERD) used in the treatment of breast cancer. It is taken by mouth.
Etacstil is an orally active, nonsteroidal, combined selective estrogen receptor modulator (SERM) and selective estrogen receptor degrader (SERD) that was developed for the treatment of estrogen receptor-positive breast cancer. It was shown to overcome antiestrogen resistance in breast cancer by altering the shape of the estrogen receptor, thus exhibiting SERD properties. Etacstil is a tamoxifen derivative and one of the first drugs to overcome tamoxifen-resistance. It is the predecessor of GW-7604, of which etacstil is a prodrug. This is analogous to the case of tamoxifen being a prodrug of afimoxifene (4-hydroxytamoxifen).
ZB716, also known as fulvestrant-3-boronic acid, is a synthetic, steroidal, orally active antiestrogen which is under development for the treatment of estrogen receptor (ER)-positive metastatic breast cancer. The drug is a silent antagonist of the ERα (IC50 = 4.1 nM) as well as a selective estrogen receptor degrader (SERD). It is an analogue and prodrug of fulvestrant in which the C3 hydroxyl group has been replaced with a boronic acid moiety. In accordance, the two drugs have similar pharmacodynamic properties. However, whereas fulvestrant is not orally active and must be administered via intramuscular injection, ZB716 is less susceptible to first-pass metabolism, and in relation to this, is orally active.
Endocrine therapy is a common treatment for estrogen receptor positive breast cancer. However, resistance to this therapy can develop, leading to relapse and progression of disease. This highlights the need for new strategies to combat this resistance.
Inavolisib, sold under the brand name Itovebi, is an anti-cancer medication used for the treatment of breast cancer. It is a inhibitor and degrader of mutant phosphatidylinositol 3-kinase (PI3K) alpha. The PI3K-mediated signalling pathway has shown to play an important role in the development of tumours as dysregulation is commonly associated with tumour growth and resistance to antineoplastic agents and radiotherapy.
Giredestrant is an investigational oral selective estrogen receptor degrader (SERD) being developed for the treatment of estrogen receptor-positive (ER+) breast cancer. It is a potent, nonsteroidal compound that antagonizes estrogen effects by competitively binding to both wild-type and mutant estrogen receptors with nanomolar potency. Giredestrant works by inducing an inactive conformation of the estrogen receptor ligand-binding domain and promoting proteasome-mediated degradation of the receptor protein.