S-40503
Encyclopedia
S-40503 is an investigational selective androgen receptor modulator
(SARM) developed by the Japanese company Kaken Pharmaceuticals, which was developed for the treatment of osteoporosis
. SARMs are a new class of drugs which produce tissue-specific anabolic effects in some tissues such as muscle and bone, but without stimulating androgen receptors in other tissues such as in the prostate gland, thus avoiding side effects such as benign prostatic hypertrophy which can occur following treatment with unselective androgens like testosterone
or anabolic steroid
s.
S-40503 is a SARM that shows good functional selectivity
for bone tissue, and has relatively little effect on muscle mass and no observable effect on the prostate gland. In animal studies it was shown to increase both bone mineral density and biomechanical strength of femoral cortical bone, and at low doses showed anabolic effects only on bone tissue, while at higher doses both bone and muscle growth were affected, yet prostate gland enlargement was not seen at any dose tested. The lack of virilizing effects means that S-40503 may even be suitable for use in women, which would be a substantial advantage over existing drugs as women tend to be more likely to suffer from osteoporosis, and are generally contraindicated from taking anabolic steroids due to the risk of side effects such as masculinisation and hirsutism
. Since these promising initial studies, no further data about S-40503 has been published by Kaken, and it is thought that rather than being developed for human use itself, S-40503 may be more likely to be used as a lead compound for the development of novel derivatives with similar bone anabolic effects, but longer in vivo half-life and better bioavailability.
Selective androgen receptor modulators may also be used by athletes to assist in training and increase physical stamina and fitness, potentially producing effects similar to anabolic steroids but with significantly less side effects. For this reason, SARMs have already been banned by the World Anti-Doping Agency
since January 2008 despite no drugs from this class yet being in clinical use, and blood tests for all known SARMs are currently being developed.
Selective androgen receptor modulator
Selective androgen receptor modulators or SARMs are a novel class of androgen receptor ligands. They are intended to have the same kind of effects as androgenic drugs like anabolic steroids but be much more selective in...
(SARM) developed by the Japanese company Kaken Pharmaceuticals, which was developed for the treatment of osteoporosis
Osteoporosis
Osteoporosis is a disease of bones that leads to an increased risk of fracture. In osteoporosis the bone mineral density is reduced, bone microarchitecture is deteriorating, and the amount and variety of proteins in bone is altered...
. SARMs are a new class of drugs which produce tissue-specific anabolic effects in some tissues such as muscle and bone, but without stimulating androgen receptors in other tissues such as in the prostate gland, thus avoiding side effects such as benign prostatic hypertrophy which can occur following treatment with unselective androgens like testosterone
Testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...
or anabolic steroid
Anabolic steroid
Anabolic steroids, technically known as anabolic-androgen steroids or colloquially simply as "steroids", are drugs that mimic the effects of testosterone and dihydrotestosterone in the body. They increase protein synthesis within cells, which results in the buildup of cellular tissue ,...
s.
S-40503 is a SARM that shows good functional selectivity
Functional Selectivity
Functional selectivity is the ligand-dependent selectivity for certain signal transduction pathways in one and the same receptor. This can be present when a receptor has several possible signal transduction pathways...
for bone tissue, and has relatively little effect on muscle mass and no observable effect on the prostate gland. In animal studies it was shown to increase both bone mineral density and biomechanical strength of femoral cortical bone, and at low doses showed anabolic effects only on bone tissue, while at higher doses both bone and muscle growth were affected, yet prostate gland enlargement was not seen at any dose tested. The lack of virilizing effects means that S-40503 may even be suitable for use in women, which would be a substantial advantage over existing drugs as women tend to be more likely to suffer from osteoporosis, and are generally contraindicated from taking anabolic steroids due to the risk of side effects such as masculinisation and hirsutism
Hirsutism
Hirsutism or frazonism is the excessive hairiness on women in those parts of the body where terminal hair does not normally occur or is minimal - for example, a beard or chest hair. It refers to a male pattern of body hair and it is therefore primarily of cosmetic and psychological concern...
. Since these promising initial studies, no further data about S-40503 has been published by Kaken, and it is thought that rather than being developed for human use itself, S-40503 may be more likely to be used as a lead compound for the development of novel derivatives with similar bone anabolic effects, but longer in vivo half-life and better bioavailability.
Selective androgen receptor modulators may also be used by athletes to assist in training and increase physical stamina and fitness, potentially producing effects similar to anabolic steroids but with significantly less side effects. For this reason, SARMs have already been banned by the World Anti-Doping Agency
World Anti-Doping Agency
The World Anti-Doping Agency , , is an independent foundation created through a collective initiative led by the International Olympic Committee . It was set up on November 10, 1999 in Lausanne, Switzerland, as a result of what was called the "Declaration of Lausanne", to promote, coordinate and...
since January 2008 despite no drugs from this class yet being in clinical use, and blood tests for all known SARMs are currently being developed.