Testolone (RAD-140)

Overview

Testolone (development code RAD-140 or RAD140; International Nonproprietary Name vosilasarm; Ellipses Pharma development code EP0062) is a synthetic, orally active nonsteroidal selective androgen receptor modulator (SARM). It is NOT a peptide and NOT a steroid — it is a small-molecule (oxadiazole-containing) drug designed to activate the androgen receptor in a tissue-selective way.

RAD-140 was designed and characterized by Radius Health (Miller et al., 2011) and later licensed to and advanced by Ellipses Pharmaceuticals as vosilasarm (EP0062). Its lead human program is in oncology: it is being studied for AR+/ER+/HER2- breast cancer, where the androgen receptor can act as a tumor suppressor. It reached Phase 1 under Radius Health and is now in an ongoing Phase 1/2 trial (NCT05573126; an earlier registration is NCT03088527). It appears on this peptide reference because it is frequently discussed, sold, and stacked alongside peptides in the fitness and "research chemical" community — not because it is one.

Chemistry and structure

Testolone is a small-molecule oxadiazole compound — an amino-acid chain it is not.

Mechanism of action

• Androgen receptor (AR) agonism. RAD-140 binds the androgen receptor with high affinity and acts as a nonsteroidal agonist. Because it is not a steroid, it is not a substrate for aromatase or 5α-reductase in the way testosterone is. [In vitro]
• Tissue selectivity ("prostate-sparing"). In gonadectomized male rats, RAD-140 was reported to be both potency- and efficacy-selective: it stimulated muscle at lower doses than were needed to affect the prostate, and was fully anabolic on muscle while showing incomplete efficacy on prostate and seminal vesicles. This is the mechanistic basis for the "selective" in SARM — but it was shown in animals, not established as a clinical safety margin in humans. [Animal]
• Muscle and bone (preclinical). Preclinical work reported increased muscle mass and bone mineral density. [Animal]
• Neuroprotection (preclinical). In cultured hippocampal neurons RAD-140 reduced apoptotic cell death about as effectively as testosterone; the effect was dependent on MAPK/ERK signaling (elevated ERK phosphorylation; blocked by the MEK inhibitor U0126). It was also neuroprotective in the rat kainate-lesion model. This is the basis for early neurodegeneration interest, but it is preclinical only. [Animal] / [In vitro]
• Oncology rationale (AR as tumor suppressor). In AR+/ER+/HER2- breast cancer, the androgen receptor can act as a tumor suppressor; the vosilasarm program is testing selective AR agonism as an anti-tumor strategy. This is the hypothesis under active clinical test. [Hypothesis] / [Human — trial ongoing]

Research and evidence

Human evidence in context. The only controlled human data are from the oncology program — a completed Phase 1 and an ongoing Phase 1/2 trial in breast-cancer patients. There are no completed human trials for muscle-building, athletic performance, or body composition; the anabolic/neuroprotective claims popular in fitness circles rest on animal and in-vitro work. Human efficacy for physique or performance is not established. The grey-market human "evidence" is essentially adverse-event case reports (predominantly liver injury), not efficacy data.

Status and regulation

• Regulatory approval: None. RAD-140 / vosilasarm is not approved by the FDA, the EMA, or any other regulator for any indication. It is investigational — a Phase 1 oncology study completed and a Phase 1/2 trial (NCT05573126) is ongoing under Ellipses Pharma.
• Anti-doping: Prohibited by the World Anti-Doping Agency (WADA) at all times (in- and out-of-competition), listed under S1.2 (Other Anabolic Agents) and named explicitly as RAD140 among the SARMs. Confirmed via the WADA Prohibited List and USADA's SARMs summary. WADA is a sport-eligibility axis and is separate from any question of legality.
• Market reality: Outside the clinical trial, it is sold only as an unregulated "research chemical." Such products are of unknown identity, purity, and potency.

Safety

Documented and expected safety signals (tagged by evidence type):

• Hepatotoxicity / DILI [Human]. See above — trial liver-enzyme elevations (AST 59% / ALT 46% / bilirubin 27% in the first RAD140 trial; transient Grade-3 ALT ~20% for vosilasarm); multiple grey-market case reports; explicit FDA warning about liver injury and acute liver failure with SARM products.
• Testosterone / HPTA suppression [Human — class effect / Hypothesis for RAD-140 specifically]. As an AR agonist, RAD-140 suppresses the hypothalamic-pituitary- testicular axis and lowers endogenous testosterone; suppression is a well-documented effect across the SARM class. No dosing, "cycle," or post-cycle guidance is given here.
• Cardiovascular / other class harms [Human — class-level]. The FDA links SARM products to increased risk of heart attack and stroke, and to other serious effects reported for the class.

Legal status

How it compares

RAD-140 is often grouped with other SARMs and with non-SARM "research chemicals." The honest framing:

• Ostarine, ligandrol (LGD-4033), andarine, YK-11 — other nonsteroidal SARMs that share RAD-140's mechanism (AR agonism), suppression risk, WADA S1.2 status, and lack of approval. RAD-140 stands out for the strength of its liver-injury signal.
• Cardarine (GW-501516) — frequently sold alongside SARMs but is NOT a SARM; it is a PPARδ agonist with an unresolved rodent-cancer signal.
• MK-677 (ibutamoren) — frequently grouped with SARMs but is a GH secretagogue / ghrelin agonist, not a SARM.

The decisive point: RAD-140 is investigational in oncology, not approved for anything, and its most-documented human effect in the grey market is liver injury — not a benchmarked, evidence-backed physique or performance therapy. See the Muscle, growth & hormones overview.

Common misconceptions

• "RAD-140 is a peptide." No. It is a synthetic nonsteroidal small molecule (C20H16ClN5O2, 393.8 g/mol). It is covered here only because it is discussed and stacked with peptides.
• "It's a milder, safer, legal alternative to steroids." No. It is not approved, it suppresses natural testosterone, and it carries the strongest liver-injury signal among common SARMs. "SARM" does not mean "safe."
• "The muscle/performance benefits are proven in humans." No. Controlled human data come from cancer trials. Physique and performance claims rest on animal and in-vitro work.
• "Buying it as a 'research chemical' means it's clean and correctly dosed." No. Independent testing (JAMA 2017) found most products sold as SARMs were mislabeled, contained a different drug, or contained nothing.

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This entry is educational and summarizes published research and public regulatory information as of the "updated" date above. It is not medical advice, not legal advice, a recommendation, or a guide to obtaining or using any substance.