What Is RAD-140 (Testolone)?
RAD-140, commonly known as Testolone, is a non-steroidal selective androgen receptor modulator (SARM) first synthesized as an investigational alternative to testosterone therapy. Its defining characteristics — a high binding affinity for the androgen receptor, strong tissue selectivity favoring muscle and bone over reproductive tissues, and oral bioavailability — have made it one of the most studied SARMs in both preclinical and early clinical settings.
RAD-140 was originally developed by Radius Health and has been investigated for its potential in treating breast cancer (ER+/AR+), muscle wasting, and testosterone deficiency. Miller et al. (2011) first characterized RAD-140’s receptor binding profile and tissue-selective activity in preclinical models, demonstrating an anabolic-to-androgenic ratio exceeding 90:1. [PMID: 24900290]
Mechanism of Action
As a full agonist at the androgen receptor in muscle and a partial agonist (or antagonist) in the prostate, RAD-140 achieves a tissue-selective anabolic profile that testosterone lacks. In the classic levator ani assay in rodents, RAD-140 demonstrates an anabolic-to-androgenic ratio estimated above 90:1, making it among the most selective SARMs characterized.
Once bound to the androgen receptor, RAD-140 triggers conformational changes that recruit specific coactivator proteins. The resulting gene expression changes promote protein synthesis, nitrogen retention, and muscle fiber hypertrophy — the same downstream outputs as testosterone but with a more restricted tissue distribution. Research by Jayaraman et al. (2014) demonstrated RAD-140’s neuroprotective properties via AR signaling in hippocampal neurons, opening additional research avenues beyond musculoskeletal applications. [PMID: 24428527]
RAD-140 in Breast Cancer Research
One of the most clinically relevant research areas for RAD-140 is ER+/AR+ breast cancer. Many breast cancers express androgen receptors, and preclinical data have shown that AR agonism can suppress ER-driven proliferation. RAD-140 has been studied in vitro and in xenograft models for its anti-tumor properties, and a Phase 1 clinical trial explored its safety in this patient population. This positions it differently from most other SARMs, which are studied primarily for anabolic and musculoskeletal applications.
Comparison With Related SARMs
- LGD-4033 (Ligandrol) — often compared to RAD-140 for anabolic potency. LGD-4033 completed Phase 2 trials and has more human pharmacokinetic data, but is generally considered less tissue-selective than RAD-140.
- MK-2866 (Ostarine) — a partial AR agonist with lower anabolic potency but the most extensive human data of any SARM to date.
- Andarine (S4) — an earlier-generation partial agonist, used as a historical benchmark in receptor selectivity studies.
- S-23 — a high-affinity, highly androgenic SARM studied for male hormonal contraception.
In dual-mechanism studies, RAD-140 is commonly combined with MK-677 (Ibutamoren) to investigate additive anabolic effects across the androgen receptor and GH/IGF-1 axes simultaneously.
Chemyo RAD-140 Research Formulations
- RAD140 | Testolone RAD-140 Solution (10mg/ml – 50ml) — >99% purity, induction sealed, batch coded.
- Testolone RAD-140 SARM Powder (1g) — for custom formulation work or analytical reference use.
All products are for laboratory research only.
