SARMs: The Potential and Controversy of Selective Androgen Receptor Modulators
Selective androgen receptor modulators (SARMs) are emerging as one of the most promising drug candidates for the treatment of muscle atrophy, osteoporosis, and cancer cachexia. Compared to traditional synthetic androgens, SARMs aim to retain potent anabolic effects while significantly reducing androgen-related side effects. This article, drawing on cutting-edge research, provides an in-depth analysis of the scientific nature, research progress, and practical challenges of SARMs.
SARMs' Core Design Philosophy
The development of SARMs stemmed from a key need: to overcome the double-edged sword dilemma of traditional steroidal androgens. While natural androgens like testosterone promote muscle growth and improve bone health (anabolism), they also cause side effects such as benign prostatic hyperplasia and hirsutism (androgenic effects).
Borrowing the tissue-selective mechanism of selective estrogen receptor modulators (SERMs), SARMs are based on non-steroidal structures, such as quinolinones and arylpropionamides. Their goal is to enhance anabolism in target tissues like muscle and bone, while mitigating adverse effects on tissues like the prostate and skin. Ideally, this could provide a safer treatment option for diseases such as sarcopenia, osteoporosis, and advanced breast cancer.
Mechanism of Action
The core advantage of SARMs is tissue selectivity. Upon binding to the androgen receptor (AR), they induce the receptor to form a specific three-dimensional conformation different from testosterone or conventional synthetic androgens. This conformational change determines the types of coactivators and co-inhibitors subsequently recruited—for example, preferentially recruiting factors that promote muscle protein synthesis, such as SRC-1 and SRC-3, while avoiding factors associated with prostate hyperplasia and hair growth, such as ARA70. This results in a potent agonist effect on skeletal muscle and bone tissue, and a weaker or even antagonistic effect on tissues such as the prostate and skin.
Furthermore, some SARMs can also act rapidly through non-genomic pathways: without relying on classic nuclear translocation and gene transcription, they directly activate signaling pathways such as MAPK and PI3K/Akt within the cell membrane or cytoplasm, promoting protein synthesis and inhibiting protein degradation within minutes.
Clinical Research: Efficacy and Limitations Coexist
Currently, several SARMs (such as Enobosarm, PF-06260414, and MK-0773) have entered clinical research stages, demonstrating certain application potential. In healthy individuals and cancer patients, SARMs can dose-dependently increase lean body mass and improve physical performance. In the treatment of androgen receptor-positive advanced breast cancer, Enobosarm resulted in clinical benefit (disease stabilization or partial remission) in 29%-32% of patients, providing a new direction for patients who have failed traditional treatments.
However, clinical data has significant limitations: existing studies are mostly placebo-controlled trials, lacking head-to-head comparisons with traditional androgens (such as oxandrolone), thus failing to confirm their superior efficacy; short-term trials show that SARMs may lead to decreased HDL cholesterol and increased liver enzymes, and long-term safety data are lacking; furthermore, due to the absence of estrogenic activity, long-term use may increase the risk of osteoporosis and decreased sexual function in men, an issue that still needs to be addressed in clinical applications.
Regulatory Status and Future Outlook
As of December 2025, no SARMs have received formal approval from the FDA or EMA, primarily due to insufficient "head-to-head comparative studies with existing standard treatments." Despite the controversy, SARMs still offer a new direction for androgen therapy. Future research needs to focus on three core areas:
l Conducting head-to-head clinical trials to clarify the differences in efficacy and safety compared to traditional androgens.
l In-depth exploration of the mechanisms of action of core regulatory factors and non-genomic pathways to optimize compound design.
l Developing precision indications for specific populations (such as elderly patients with sarcopenia or breast cancer patients).
For professionals, SARMs represent a research area that is "theoretically feasible but requires further evidence." For the general public, the risk of misuse of unapproved products should be carefully considered. As research progresses, if the bottleneck of tissue selectivity in clinical translation can be overcome, SARMs have the potential to truly become "precision tools" for disease treatment, rather than the misunderstood "performance enhancers."
Read More: https://doi.org/10.3389/fendo.2025.1634799