LGD-4033

LGD-4033, designated Ligandrol, is a non-steroidal selective androgen receptor modulator developed by Ligand Pharmaceuticals and subsequently licensed to Viking Therapeutics for clinical advancement. It is among the most thoroughly studied SARMs in clinical settings, with published Phase I and Phase II human trial data — a level of clinical evidence that few research compounds in this class possess. Structurally, LGD-4033 features a pyrrolidinyl-benzonitrile scaffold optimized for high AR binding affinity and oral activity.

LGD-4033 binds to the androgen receptor with a Ki of approximately 1 nM — affinity comparable to that of dihydrotestosterone — and activates AR-dependent transcriptional programs in skeletal muscle and bone. Its tissue selectivity arises from differential co-regulator recruitment: in muscle, LGD-4033-bound AR preferentially recruits anabolic co-activators, while in prostate tissue, the conformational change induced by LGD-4033 binding favors interaction with co-repressors. The result is robust anabolic signaling in target tissues with minimal androgenic activity in reproductive organs.

In published human trials, LGD-4033 produced statistically significant dose-dependent increases in lean body mass — up to 1.21 kg (2.67 lbs) in 21 days at 1mg/day, the highest dose tested — with no significant changes in prostate-specific antigen, hematocrit, or liver enzymes. This positions LGD-4033 as the SARM with the strongest clinical evidence for lean mass efficacy. Additional research highlights its potential for bone density preservation and muscle wasting prevention.

LGD-4033 is ideal for researchers pursuing clean, clinical-grade lean mass accrual with predictable, well-characterized pharmacology. Its extensive human data provides a level of dosing confidence that more novel compounds lack. It is suited for intermediate researchers — those who have experience with milder SARMs like Ostarine and are seeking greater anabolic potency. Commonly run as the centerpiece of bulking or lean-gaining protocols, and frequently stacked with MK-677 for enhanced recovery and appetite support.

LGD-4033 has an elimination half-life of 24–36 hours, supporting once-daily dosing. Oral bioavailability is high. Testosterone suppression is dose-dependent and clinically documented: at 1mg/day, free testosterone and SHBG were significantly reduced by Day 21 but recovered to baseline within 35 days of cessation (56 days from cycle start) without PCT intervention. At standard research doses of 5–10mg, suppression is more pronounced and PCT with a SERM (Nolvadex 20mg or Clomid 25mg for 4 weeks) is prudent for cycles exceeding 6 weeks. No significant hepatotoxicity has been observed. Typical protocols range from 5–15mg daily for 8–12 weeks.