A (selective) androgen receptor degrader or downregulator (SARD) is a type of drug which interacts with the androgen receptor (AR) such that it causes the AR to be degraded and thus downregulated. [1] They are under investigation for the treatment of prostate cancer and other androgen-dependent conditions. [1]
As of 2017, dimethylcurcumin (ASC-J9), a SARD, is under development for the treatment of acne vulgaris. [2]
In addition, several PROTACs degraders targeting the androgen receptor have been tested in the clinic:
Enzalutamide, sold under the brand name Xtandi, is a nonsteroidal antiandrogen (NSAA) medication which is used in the treatment of prostate cancer. It is indicated for use in conjunction with castration in the treatment of metastatic castration-resistant prostate cancer (mCRPC), nonmetastatic castration-resistant prostate cancer, and metastatic castration-sensitive prostate cancer (mCSPC). It is taken by mouth.
Cabazitaxel, sold under the brand name Jevtana, is a semi-synthetic derivative of a natural taxoid. It is a microtubule inhibitor, and the fourth taxane to be approved as a cancer therapy.
Galeterone is a steroidal antiandrogen which was under development by Tokai Pharmaceuticals for the treatment of prostate cancer. It possesses a unique triple mechanism of action, acting as an androgen receptor antagonist, androgen receptor down regulator, and CYP17A1 inhibitor, the latter of which prevents the biosynthesis of androgens. As a CYP17A1 inhibitor, galeterone shows selectivity for 17,20-lyase over 17α-hydroxylase.
EPI-001 is the first inhibitor of the androgen receptor amino-terminal domain. The single stereoisomer of EPI-001, EPI-002, is a first-in-class drug that the USAN council assigned a new stem class "-aniten" and the generic name "ralaniten". This distinguishes the anitens novel molecular mechanism from anti androgens that bind the C-terminus ligand-binding domain and have the stem class "lutamide". EPI-001 and its stereoisomers and analogues were discovered by Marianne Sadar and Raymond Andersen, who co-founded the pharmaceutical company ESSA Pharma Inc for the clinical development of anitens for the treatment of castration-resistant prostate cancer (CRPC).
Tasquinimod is an experimental drug currently being investigated for the treatment of solid tumors. Tasquinimod has been mostly studied in prostate cancer, but its mechanism of action suggests that it could be used to treat other cancers. Castration-resistant prostate cancer (CRPC), formerly called hormone-resistant or hormone-refractory prostate cancer, is prostate cancer that grows despite medical or surgical androgen deprivation therapy. Tasquinimod targets the tumor microenvironment and counteracts cancer development by inhibiting angiogenesis and metastasis and by modulating the immune system. It is now in phase III development, following successful phase II trial outcomes.
PROSTVAC is a cancer immunotherapy candidate in clinical development by Bavarian Nordic for the treatment of all prostate cancer although clinical trials are focusing on more advanced cases of metastatic castration-resistant prostate cancer (mCRPC). PROSTVAC is a vaccine designed to enable the immune system to recognize and attack prostate cancer cells by triggering a specific and targeted T cell immune response to cancer cells that express the tumor-associated antigen prostate-specific antigen (PSA).
Seviteronel is an experimental cancer medication which is under development by Viamet Pharmaceuticals and Innocrin Pharmaceuticals for the treatment of prostate cancer and breast cancer. It is a nonsteroidal CYP17A1 inhibitor and works by inhibiting the production of androgens and estrogens in the body. As of July 2017, seviteronel is in phase II clinical trials for both prostate cancer and breast cancer. In January 2016, it was designated fast-track status by the United States Food and Drug Administration for prostate cancer. In April 2017, seviteronel received fast-track designation for breast cancer as well.
Darolutamide, sold under the brand name Nubeqa, is an antiandrogen medication which is used in the treatment of non-metastatic castration-resistant prostate cancer in men. It is specifically approved to treat non-metastatic castration-resistant prostate cancer (nmCRPC) in conjunction with surgical or medical castration. The medication is taken by mouth twice per day with food.
Apalutamide, sold under the brand name Erleada among others, is a nonsteroidal antiandrogen (NSAA) medication used for the treatment of prostate cancer. It is an androgen receptor inhibitor. It is taken by mouth.
Vosilasarm, also known by the development codes RAD140 and EP0062 and by the black-market name Testolone or Testalone, is a selective androgen receptor modulator (SARM) which is under development for the treatment of hormone-sensitive breast cancer. It is specifically under development for the treatment of androgen receptor-positive, estrogen receptor-negative, HER2-negative advanced breast cancer. Vosilasarm was also previously under development for the treatment of sarcopenia, osteoporosis, and weight loss due to cancer cachexia, but development for these indications was discontinued. The drug is taken by mouth.
Ralaniten acetate is a first-in-class antiandrogen that targets the N-terminal domain (NTD) of the androgen receptor (AR) developed by ESSA Pharmaceuticals and was under investigation for the treatment of prostate cancer. This mechanism of action is believed to allow the drug to block signaling from the AR and its splice variants. EPI-506 is a derivative of bisphenol A and a prodrug of ralaniten (EPI-002), one of the four stereoisomers of EPI-001, and was developed as a successor of EPI-001. The drug reached phase I/II prior to the discontinuation of its development. It showed signs of efficacy in the form of prostatic specific antigen (PSA) decreases (4–29%) predominantly at higher doses (≥1,280 mg) in some patients but also caused side effects and was discontinued by its developer in favor of next-generation AR NTD inhibitors with improved potency and tolerability.
Ketodarolutamide is a nonsteroidal antiandrogen (NSAA) and the major active metabolite of darolutamide, an NSAA which is used in the treatment of prostate cancer in men. Similarly to its parent compound, ketodarolutamide acts as a highly selective, high-affinity, competitive silent antagonist of the androgen receptor (AR). Both agents show much higher affinity and more potent inhibition of the AR relative to the other NSAAs enzalutamide and apalutamide, although they also possess much shorter and comparatively less favorable elimination half-lives. They have also been found not to activate certain mutant AR variants that enzalutamide and apalutamide do activate. Both darolutamide and ketodarolutamide show limited central nervous system distribution, indicating peripheral selectivity, and little or no inhibition or induction of cytochrome P450 enzymes such as CYP3A4, unlike enzalutamide and apalutamide.
Dimethylcurcumin is a nonsteroidal antiandrogen and a synthetic curcuminoid which is under development by AndroScience Corporation as a topical medication for the treatment of acne vulgaris. It has also been under investigation for the treatment of male pattern hair loss, spinal muscular atrophy, and wounds, but no development has been reported for these indications. There has been interest in the drug for the potential treatment of prostate cancer as well. As of 2017, it is in phase II clinical trials for acne vulgaris.
BMS-641988 is a nonsteroidal antiandrogen which was developed by Bristol-Myers Squibb for the treatment of prostate cancer but was never marketed. It acts as a potent competitive antagonist of the androgen receptor (AR) (Ki = 10 nM; IC50Tooltip half-maximal inhibitory concentration = 56 nM). The drug was found to have 20-fold higher affinity for the AR than bicalutamide in MDA-MB-453 cells, and showed 3- to 7-fold the antiandrogenic activity of bicalutamide in vitro. It may have some weak partial agonist activity at the androgen receptor. BMS-641988 is transformed by CYP3A4 into BMS-570511, and this metabolite is then reduced to BMS-501949 by cytosolic reductases. All three compounds show similar antiandrogenic activity. In addition to its antiandrogenic activity, BMS-641988 shows activity as a negative allosteric modulator of the GABAA receptor, and can produce seizures in animals at sufficiently high doses. It also shows some drug-induced QT prolongation. BMS-641988 reached phase I clinical trials prior to the discontinuation of its development. The clinical development of BMS-641988 was terminated due to the occurrence of a seizure in a patient during a phase I study.
Masofaniten, also known by its developmental code name EPI-7386, is an N-terminal domain antiandrogen, or antagonist of the N-terminal domain (NTD) of the androgen receptor (AR), which is under development for the treatment of prostate cancer. The compound was developed as a successor of previous drugs in the EPI series such as EPI-001, ralaniten (EPI-002), and ralaniten acetate (EPI-506). Masofaniten shows 20-fold higher antiandrogenic potency than ralaniten in vitro (IC50Tooltip Half-maximal inhibitory concentration = 535 nM vs. 9,580 nM, respectively), as well as greater stability in human hepatocytes. It was planned to enter phase I clinical trials in 2020. Preliminary results of a phase I/II clinical trial were published in 2023.
Chimeric small molecule therapeutics are a class of drugs designed with multiple active domains to operate outside of the typical protein inhibition model. While most small molecule drugs inhibit target proteins by binding their active site, chimerics form protein-protein ternary structures to induce degradation or, less frequently, other protein modifications.
Bavdegalutamide is an experimental proteolysis targeting chimera that functions as a androgen receptor degrader. It is being developed to treat metastatic castration-resistant prostate cancer.
Luxdegalutamide, also known as ARV-766, is an investigational oral androgen receptor (AR) degrader being developed by Arvinas for the treatment of metastatic castration-resistant prostate cancer (mCRPC). It belongs to a class of drugs called proteolysis targeting chimeras (PROTACs), which are designed to selectively degrade specific proteins by hijacking the ubiquitin-proteasome system. Luxdegalutamide is a second-generation PROTAC AR degrader that has demonstrated a broader efficacy profile and better tolerability compared to its predecessor, ARV-110, in clinical settings. It has shown promise in overcoming resistance associated with certain AR mutations, including the L702H mutation, which is prevalent in up to 24% of treated mCRPC patients. As of 2024, luxdegalutamide is being evaluated in phase I/II clinical trials for prostate cancer.
Gridegalutamide is an investigational oral androgen receptor (AR) degrader being developed for the treatment of metastatic castration-resistant prostate cancer (mCRPC). It belongs to a class of drugs called proteolysis targeting chimeras (PROTACs), which are designed to selectively degrade specific proteins by hijacking the ubiquitin-proteasome system. CC-94676 employs a unique dual mechanism of action, combining AR degradation with AR antagonism, potentially offering advantages over traditional AR inhibitors in overcoming resistance mechanisms. Initially developed by Celgene and now under Bristol Myers Squibb, CC-94676 has demonstrated AR protein degradation and suppression of tumor growth in CRPC mouse models. As of 2024, CC-94676 is being evaluated in phase I clinical trials for patients with mCRPC who have progressed on androgen-deprivation therapy and at least one prior secondary hormonal therapy.