History

LGD-4033 was originally developed by Ligand Pharmaceuticals and later licensed to Viking Therapeutics as VK5211. It was investigated for muscle-wasting and bone-related indications, reaching a Phase 2 hip-fracture trial, but never completed development and has never been approved as a drug.

Ligandrol (LGD-4033) is a nonsteroidal selective androgen receptor modulator — a SARM, and importantly a small molecule rather than a peptide. It is widely sold online and used in fitness circles as a supposedly “safer” alternative to anabolic steroids, but the actual human evidence is limited to one short Phase 1 study, the documented harms (hormone suppression, adverse lipid changes, multiple published cases of liver injury) are real, and it is an unapproved drug that is illegal to sell as a supplement and banned across sport.

What it is

LGD-4033 is a nonsteroidal selective androgen receptor modulator (SARM) — a small molecule, not a peptide. It binds the androgen receptor (AR) and acts as a tissue-selective partial agonist, designed to stimulate AR signaling in muscle and bone with relatively less activity in prostate and other tissues than testosterone. This selectivity is the theoretical basis for the entire SARM class, but in practice the selectivity is imperfect (see the suppression data below). It is orally active. It was originally developed by Ligand Pharmaceuticals and later licensed to Viking Therapeutics as VK5211. It is not FDA-approved for any indication and has never completed development as a drug.

The claims

LGD-4033 is marketed illegally and used in fitness and biohacking circles for lean muscle gain, strength, body recomposition, and faster recovery, often promoted as a “safer alternative to anabolic steroids” with fewer side effects. It is sold online and in some “bodybuilding supplement” products labeled as research chemicals or, deceptively, as dietary supplements. Legitimate clinical interest historically targeted muscle wasting/cachexia, age-related sarcopenia, and post-hip-fracture recovery — but no approved product resulted.

What the evidence actually shows

The main real human data comes from a single trial. Basaria et al. (2013) was a randomized, double-blind, placebo-controlled ascending-dose Phase 1 trial in 76 healthy young men over 21 days. LGD-4033 was generally well tolerated short-term and produced a dose-dependent increase in lean body mass even over three weeks; fat mass did not change significantly, and PSA did not change significantly over the short window. However, it caused dose-dependent suppression of total testosterone and SHBG, along with reductions in HDL cholesterol and triglycerides. Hormone and lipid levels returned toward baseline after discontinuation. This is a short, small, single-administration-window safety/PK study — not evidence of long-term efficacy or safety.

For cachexia, Viking Therapeutics ran a Phase 2 trial of VK5211 (LGD-4033) in patients recovering from hip fracture (108 patients, 12 weeks), reporting statistically significant dose-dependent increases in lean body mass. This was a company-reported result (top-line release 2017; ASBMR 2018 presentation), the program did not advance to approval, and there is no verified peer-reviewed publication, so it should be weighed accordingly. Preclinical and mechanistic data on AR binding and tissue selectivity exist but are limited. Overall the evidence base is thin: there are no large, long-term, peer-reviewed efficacy or safety trials in humans.

Legal and regulatory status

In the US, SARMs including LGD-4033 are not approved for any use and are not lawful dietary-supplement ingredients. The FDA issued a public warning on October 31, 2017, that bodybuilding products containing SARMs put consumers at risk of heart attack, stroke, and life-threatening liver injury, and it has sent warning letters to companies marketing them. Products sold as supplements that contain SARMs are unapproved/misbranded drugs.

As of June 2026, SARMs (including LGD-4033) are not federally controlled substances under the Controlled Substances Act. SARMs-scheduling legislation has been proposed in past sessions of Congress; passage cannot be confirmed, so SARMs are best treated as legally restricted unapproved drugs rather than scheduled substances. SARMs are distinct from anabolic-androgenic steroids and are not covered by the Anabolic Steroids Control Act (by contrast, oxandrolone is a Schedule III anabolic steroid).

In sport, all SARMs — including LGD-4033 (ligandrol), ostarine/enobosarm (MK-2866), andarine (S-4), RAD140, S-23, and YK-11 — are prohibited at all times (in and out of competition) under Section S1.2 (“Other Anabolic Agents”) of the WADA Prohibited List. LGD-4033 has been the basis of multiple athlete sanctions, sometimes from contaminated supplements.

Safety

Testosterone / HPG-axis suppression: Demonstrated in the Basaria trial (dose-dependent, reversible short-term). Real and expected for an AR agonist.
Lipid changes: HDL and triglyceride reductions were documented in the same trial — a cardiovascular-relevant signal.
Hepatotoxicity (drug-induced liver injury): Multiple published case reports describe cholestatic/hepatocellular liver injury and jaundice associated with LGD-4033 use — for example, Flores et al. (2020) reported severe DILI / cholestatic hepatitis with fibrosis on biopsy in a 32-year-old man, and a 2024 Cureus report described DILI in a 52-year-old man after roughly three months of use. The FDA notes liver injuries requiring hospitalization among SARM users generally. These are case reports and pharmacovigilance signals, not controlled incidence data, but they represent real documented harm.

A note on related but distinct compounds (these are not LGD-4033 effects): andarine (S-4) is anecdotally linked to transient visual disturbances; GW-501516 (Cardarine) is not a SARM but a PPARδ agonist that GlaxoSmithKline discontinued circa 2006–2007 after long-term rodent studies showed tumors in multiple organs; and SR9009 (Stenabolic) is a REV-ERB agonist research chemical, also not a SARM. GW-501516 and SR9009 are banned in sport under WADA Section S4 (Hormone and Metabolic Modulators), with GW-501516 classified specifically as a PPARδ agonist.

Bottom line

The strongest real human evidence for LGD-4033 is a single short 3-week Phase 1 trial showing modest lean-mass gain alongside testosterone, SHBG, HDL, and triglyceride suppression. Long-term efficacy and safety in humans are unproven. The documented harms — testosterone suppression, adverse lipid changes, and multiple published cases of liver injury — are real. It is an unapproved drug, illegal to sell as a supplement, and banned in sport.

Evidence grade: Preliminary human.