YK11 (also known by its chemical name (17α,20E)-17,20-[(1-methoxyethylidene)bis(oxy)]-3-oxo-19-norpregna-4,20-diene-21-carboxylic acid methyl ester) is a promising new research compound found to be an agonist of the androgen receptor (AR) leading it to be classified as a SARM. YK11 research has also found it to possess a great ability to inhibit myostatin. These qualities have led to its growing use in muscle wasting/building research. YK11 activates the AR without causing unwanted side effects commonly associated in anabolic/androgenic research of the past. YK11’s ability to inhibit myostatin plays a major role in its muscle and tissue building qualities. YK11 induces “myogenic differentiation of C2C12 cells and the expression of follistatin”. Follistatin plays a vital role in the tissue building and repair of many species and research notes; “increasing the amount of follistatin, resulted in greatly increased muscle mass”. This is clearly an important aspect to the anabolic effects seen in YK11 research and shows it’s a multifaceted compound with a wide array of research opportunities. YK11 is the latest flavor of the month in the underground gray market bodybuilding supplement world. YK11 is a steroidal molecule that has only been shown to have effects in cellular assays. This means that there are no published results in animals or humans as yet. Even so it has popped up for sale on the internet as an anabolic SARM or Selective Androgen Receptor Modulator.
SARMs are molecules that have the anabolic effects of steroids like testosterone or nandrolone but lack a lot of the negative side effects like hair loss, prostate enlargement and acne. New age SARMs like LGD-4033 and Ostarine are non-steroidal, meaning that they do not have the typical four ring structure of classical androgens like testosterone. Steroids like Nandrolone and perhaps trenbolone can be considered to be SARMs since they convert through 5-alpha reduction to less potent androgens and in reasonable doses show more anabolic than androgenic effects. Steroid has been turned into a bad word so for the most part, companies are developing non-steroidal SARMS. In reality, it makes little difference the shape of the molecule but rather what its effects are.
YK11 is steroidal. In fact, it looks a lot like nandrolone. The two papers that are available show that YK11 can activate the androgen receptor but that it does so only partially. This results in an effect known as partial agonism. This means that YK11 can potentially displace stronger androgens while exerting a lower overall stimulating effect on the receptor. In fact the paper by Kanno et al demonstrates this effect by bathing cells in DHT alone or in DHT + YK11. Those cells that received both DHT and YK11 had less androgenic stimulation than with DHT alone. This is important since, in the presence of stronger androgens, YK11 will actually reduce androgen receptor stimulation. In the case of the prostate or hair follicle, this can be a good thing. In skeletal muscle, this will not be a good thing.