RAD-140 (Testolone) is widely regarded as the most potent and tissue-selective SARM (Selective Androgen Receptor Modulator) in the current research literature. With a reported anabolic:androgenic ratio of approximately 90:1 (compared to testosterone’s 1:1), RAD-140 represents the theoretical ideal of SARM pharmacology — maximum anabolic tissue stimulation with minimal androgenic side effects. It has advanced to Phase I and Phase II clinical trials, giving it one of the strongest human safety data sets in the SARM class.
What Is RAD-140?
RAD-140 (2-chloro-4-((S)-3-(4-cyanobenzyl)-1-(2H-tetrazol-5-yl)-4-(trifluoromethyl)pyrrolidin-1-yl)-N-(5-cyanopyridin-3-yl)benzamide-2-d) is a non-steroidal SARM developed by Radius Health. It selectively binds the androgen receptor (AR) and produces tissue-selective anabolic effects — stimulating AR in muscle and bone while producing minimal androgenic stimulation in prostate and skin. It has been studied in Phase I safety trials and Phase II trials for breast cancer (ER+/AR+) and muscle wasting.
Mechanism of Action
Selective Androgen Receptor Binding: RAD-140 binds the androgen receptor with high affinity and selectivity. Upon binding, it induces a distinct AR conformation compared to testosterone — a conformation that recruits coactivators associated with anabolic (muscle, bone) gene programs while failing to recruit coactivators required for androgenic (prostate, sebaceous gland, hair follicle) gene programs.
Tissue Selectivity Mechanism: The differential coactivator recruitment is the molecular basis of tissue selectivity. In muscle and bone, the AR-RAD-140 complex activates anabolic gene networks (IGF-1, follistatin, myosin heavy chain). In prostate and other androgenic tissues, the complex has reduced transcriptional activity because it cannot recruit the same coactivators that testosterone-AR complex uses.
Neuroprotection: A distinctive and underappreciated aspect of RAD-140 research is its neuroprotective activity. RAD-140 has been shown to protect neurons from beta-amyloid toxicity and apoptosis in brain tissue — through an AR-mediated mechanism involving Akt and Bcl-2 pro-survival pathways. This neuroprotective profile makes it relevant to Alzheimer’s disease research.
Key Research Findings
Anabolic:Androgenic Ratio: In castrated rat models — the standard assay for comparing anabolic vs. androgenic activity — RAD-140 produced levator ani (anabolic) muscle mass gains comparable to testosterone at doses that produced significantly less prostate weight gain. The reported anabolic:androgenic ratio of ~90:1 compares favorably to even the most anabolic steroidal androgens.
Phase I Clinical Safety: Phase I trials in healthy volunteers demonstrated RAD-140 was well-tolerated at multiple dose levels, with predictable pharmacokinetics and dose-dependent testosterone and LH suppression (confirming androgen axis activity) — the primary expected effect of AR agonism via negative feedback.
Breast Cancer Research: Phase II trials are studying RAD-140 in ER+/AR+ breast cancer — cancers that express androgen receptors and may be inhibited by AR activation, similar to the mechanism of enzalutamide in prostate cancer. Early Phase II data showed clinical activity in this indication.
Neuroprotection: Animal research at USC demonstrated RAD-140 protected hippocampal neurons from beta-amyloid toxicity, and showed neuroprotective and neurogenesis-promoting effects in TBI models — a research application distinct from its anabolic profile.
RAD-140 vs. Other SARMs
| SARM | Anabolic:Androgenic Ratio | Clinical Trials | Key Application |
|---|---|---|---|
| RAD-140 | ~90:1 | Phase I + II | Muscle, bone, breast cancer, neuroprotection |
| LGD-4033 | ~10:1 | Phase I + II | Muscle wasting, hip fracture |
| Ostarine (MK-2866) | ~3:1 | Phase I–III | Muscle wasting, most clinical data |
| S23 | Very high | Preclinical | Muscle, bone, male contraception |
Conclusion
RAD-140’s exceptional anabolic:androgenic selectivity ratio, Phase II clinical data in breast cancer, neuroprotective activity, and pharmacological elegance make it the most scientifically advanced SARM in the research literature. For researchers studying androgen receptor biology, muscle wasting, bone density, breast cancer biology, or neuroprotection, RAD-140 is an essential research compound. Combat Research provides research-grade RAD-140 for qualified research applications.
Shop RAD-140 at Combat Research
Related Research Articles
For research purposes only. Not for human therapeutic use.
One Response