RAD-150 (TLB-150) — Complete Research Guide

Introduction

RAD-150, also designated TLB-150, is a modified ester prodrug of RAD-140 (Testolone), one of the most studied non-steroidal selective androgen receptor modulators (SARMs) in the research literature. The key structural modification in RAD-150 is the addition of a benzoate ester group at the hydroxyl position of the RAD-140 parent molecule, which is designed to modify the compound’s pharmacokinetic profile—specifically to slow hydrolysis and extend the duration of active compound exposure following administration. RAD-150 itself does not bind the androgen receptor with significant affinity; rather, it undergoes enzymatic hydrolysis in vivo to release RAD-140 as the active ligand at the androgen receptor.

This ester prodrug strategy is well-established in pharmaceutical chemistry and has been employed across multiple drug classes to improve bioavailability, extend half-life, or modify tissue distribution. In the context of SARM research, RAD-150’s esterification raises specific questions about hydrolysis kinetics, the pharmacokinetic profile of the released RAD-140, and whether the modified exposure curve produces different tissue-selective effects compared to RAD-140 administered directly.

Mechanism of Action

Prodrug Hydrolysis and AR Binding

Following administration, RAD-150 is hydrolyzed by plasma and tissue esterases to yield RAD-140 (Testolone) as the active moiety, along with benzoic acid as a byproduct. The rate of this hydrolysis determines the pharmacokinetic profile of the active compound—slower hydrolysis produces a more sustained RAD-140 plasma curve compared to direct RAD-140 administration, analogous to the longer-acting profile of testosterone enanthate or cypionate relative to testosterone suspension.

Once liberated, RAD-140 acts as a partial agonist at the androgen receptor (AR) with high binding affinity and selectivity for anabolic tissues (muscle, bone) over androgenic tissues (prostate, sebaceous glands). The tissue selectivity is mediated by differential co-activator recruitment depending on the conformational change induced by RAD-140 binding—a hallmark of the SARM mechanism that distinguishes these compounds from testosterone and DHT, which recruit co-activators more broadly across tissues.

Comparison with Full vs. Partial Agonism

RAD-140 and its prodrug RAD-150 are partial AR agonists in androgenic tissues while producing more complete agonism in anabolic tissues. This partial agonism profile contrasts with LGD-4033 (Ligandrol), which is considered a more complete AR agonist across tissue types. The distinction has practical implications for research into prostate safety endpoints and HPG axis suppression: partial agonists at the AR in gonadotrope cells may produce less LH/FSH suppression than full agonists, though published data on the magnitude of this difference across SARM candidates remains limited.

Research Evidence

The foundational pharmacological characterization of RAD-140 was published by Miller and colleagues (2011, ACS Medicinal Chemistry Letters), which reported high AR binding affinity (Ki ~7 nM), selective anabolic activity in muscle and bone with reduced androgenic activity in prostate tissue in castrated rat models, and a favorable tissue selectivity ratio compared to testosterone. This study established RAD-140 as a lead SARM candidate and forms the pharmacological basis for RAD-150 research, since RAD-150’s activity is mediated through the same RAD-140 active moiety after hydrolysis.

Jayaraman and colleagues (2014) reported neuroprotective properties of RAD-140 in in-vitro models and in vivo, demonstrating activation of neuroprotective signaling cascades including the MAPK/ERK pathway and attenuation of apoptosis in neurons exposed to toxic stimuli. The authors noted that RAD-140 activated pro-survival signaling in hippocampal neurons in an AR-dependent manner, and that this neuroprotection occurred at concentrations below those producing androgenic effects. This finding extended RAD-140/RAD-150 research interest beyond muscle biology into neuroscience and neuroprotection models.

HPG axis suppression studies in non-human primates and rodent models have documented dose-dependent suppression of LH and FSH with RAD-140, consistent with the negative feedback that any AR agonist exerts at the hypothalamus and pituitary. The magnitude and recovery kinetics of this suppression relative to testosterone replacement—and how RAD-150’s extended pharmacokinetic profile affects these dynamics—remains an active area of pre-clinical investigation.

RAD-150 vs. RAD-140 vs. LGD-4033

Researchers choosing between these compounds for study design should understand their key comparative characteristics:

• Active Moiety: RAD-150 and RAD-140 share the same active compound (RAD-140) after RAD-150 hydrolysis; LGD-4033 has a distinct chemical structure and different AR binding conformation.
• Agonism Profile: RAD-140 is a partial AR agonist in androgenic tissues; LGD-4033 behaves as a more complete AR agonist. This affects androgenic side effect profiles and HPG axis suppression magnitude in research models.
• Pharmacokinetics: RAD-150’s benzoate ester is designed to extend the effective half-life of released RAD-140; RAD-140 administered directly has a shorter plasma half-life; LGD-4033 has a reported half-life of approximately 24–36 hours in humans from Phase I trial data.
• HPG Suppression: Both RAD-140 and LGD-4033 suppress LH/FSH in a dose-dependent manner in pre-clinical studies; Phase I data for LGD-4033 documented dose-dependent testosterone suppression in healthy male volunteers; comparable human data for RAD-140/RAD-150 is not yet published.
• Neuroprotection Data: RAD-140 has published neuroprotection data (Jayaraman et al., 2014); LGD-4033 neuroprotection has not been characterized to the same extent.

Research Observations

Pre-clinical studies of RAD-140 (and by extension RAD-150) document dose-dependent increases in lean mass and muscle weight in rodent models, selective anabolic activity in muscle and bone with attenuated prostate stimulation compared to testosterone, HPG axis suppression at pharmacological doses, and neuroprotective activity in hippocampal models. The prodrug modification in RAD-150 is designed to produce a more sustained active compound exposure, which may be relevant for studies examining chronic dosing effects versus acute receptor activation.

Long-term safety data for RAD-150 specifically are not available in the published literature. The compound has not progressed through formal human clinical trials as of the time of writing, and its pharmacokinetics in humans are not characterized. RAD-140 Phase I clinical trial data is limited. Neither compound holds FDA or EMA approval. Researchers should design studies with appropriate safety monitoring protocols consistent with the pre-clinical stage of development.

Sourcing RAD-150 for Research

Researchers sourcing RAD-150 (TLB-150) for laboratory studies can find both solution and powder formats at chemyosarms.us. The RAD-150 solution provides convenient dosing for in-vivo pharmacology studies, while RAD-150 powder offers flexibility for formulation development and in-vitro work. All batches are supplied with third-party certificates of analysis confirming identity and purity.

Researchers comparing RAD-150 with LGD-4033 in receptor pharmacology or in-vivo models can find further details on the LGD-4033 vs. RAD-150 comparison page at chemyosarms.us.

Frequently Asked Questions

For a comprehensive overview of selective androgen receptor modulators including LGD-4033, MK-677, and other compounds under investigation, see the complete SARM research guide at chemyosarms.us.