SLU-PP-332 Capsules

SLU-PP-332 is a small-molecule pan-agonist of the estrogen-related receptors (ERRα, ERRβ, and ERRγ) developed at Saint Louis University by the laboratory of Thomas Burris and colleagues. It is not a peptide. The molecule is a synthetic organic compound with the reported formula C21H21F3N2O4 and a molecular weight of approximately 422.4 g/mol, which is what makes an oral capsule presentation chemically feasible — unlike peptide-based exercise mimetics, SLU-PP-332 is not immediately degraded by gastrointestinal proteases.

The research significance of SLU-PP-332 lies in its identification as one of the first potent, orally available agonists of the ERR family. The estrogen-related receptors are orphan nuclear receptors — they do not have a known endogenous ligand — and they act as master regulators of oxidative metabolism in skeletal muscle, heart, and brown adipose tissue. For years the ERRs were considered pharmacologically difficult targets. Billon and colleagues reported SLU-PP-332 as a chemical probe that activates all three ERR isoforms, opening the receptor family to in vivo investigation in rodent models of obesity, heart failure, and metabolic disease.

What differentiates SLU-PP-332 from other compounds marketed as "exercise mimetics" is its proposed mechanism. Rather than acting through AMPK activation (as with AICAR) or PPARδ (as with GW501516), SLU-PP-332 is reported to reprogram muscle transcription toward an oxidative, endurance-trained phenotype by directly engaging the ERR nuclear receptor family. In the original preclinical report, treated mice increased running distance and time-to-exhaustion on a treadmill without a change in body weight in the acute setting. It is important to state plainly: no human clinical trials of SLU-PP-332 have been published. All efficacy and safety data currently in the literature derive from rodent studies. Any characterization of SLU-PP-332 as a validated performance or metabolic intervention in humans is not supported by the record.

The compound is offered here strictly as a research chemical for in vitro and preclinical in vivo investigation of ERR biology, mitochondrial biogenesis, and oxidative metabolism.

SLU-PP-332 is a synthetic agonist of the three estrogen-related receptor isoforms — ERRα (NR3B1), ERRβ (NR3B2), and ERRγ (NR3B3). Despite the name, the ERRs do not bind estrogen and are functionally distinct from the classical estrogen receptors ERα and ERβ. They are constitutively active orphan nuclear receptors whose transcriptional output is normally modulated by coactivator recruitment — most notably by PGC-1α, the same coactivator induced by endurance exercise.

Direct ERR engagement. In the Billon et al. characterization, SLU-PP-332 was reported to activate ERRα, ERRβ, and ERRγ in cell-based reporter assays with sub-micromolar potency. The compound is described as an agonist that stabilizes an active receptor conformation and promotes coactivator recruitment, rather than a ligand that displaces an endogenous agonist (there is no established endogenous ERR agonist to displace).

Transcriptional downstream effects. ERR activation in skeletal muscle is reported to upregulate a gene program overlapping with the endurance-training response: mitochondrial biogenesis genes, oxidative phosphorylation subunits, fatty acid oxidation enzymes, and slow-twitch fiber markers. In the murine data, SLU-PP-332 administration produced transcriptomic shifts in gastrocnemius consistent with this program, and mice showed increased treadmill endurance without a training stimulus.

Metabolic effects in obesity models. A follow-up report from the same group (Billon et al., J Pharmacol Exp Ther, 2024) described that SLU-PP-332 administration to diet-induced obese mice reduced fat mass and improved glucose handling without reducing food intake. The proposed mechanism is increased energy expenditure through skeletal muscle and brown adipose oxidative capacity, rather than appetite suppression — a mechanistic profile distinct from GLP-1 receptor agonists.

Comparison with other exercise-mimetic mechanisms. AICAR acts as an AMP-mimetic and activates AMPK, producing an acute energy-stress signal. GW501516 (cardarine) is a PPARδ agonist that shifts substrate use toward fatty acid oxidation and was discontinued from clinical development after rodent carcinogenicity findings. SLU-PP-332 operates one step upstream in transcriptional regulation, directly engaging the nuclear receptor family that PGC-1α coactivates. Whether this upstream position translates to a different safety profile is not established; long-term carcinogenicity, cardiac, and reproductive studies have not been reported.

Limits of the mechanistic picture. The pan-agonist profile means that isoform-specific contributions cannot be dissected pharmacologically with SLU-PP-332 alone — genetic knockouts are required. ERRα is broadly expressed; ERRβ has roles in trophoblast and inner ear development; ERRγ is enriched in heart and slow-twitch muscle. The consequences of chronic simultaneous activation of all three isoforms in adult mammals have not been fully characterized, and no human pharmacokinetic or pharmacodynamic data exist.

SLU-PP-332 is a synthetic small molecule, not a peptide. This is the single most important property to understand about the compound, because it is why an oral capsule format is chemically plausible where it would not be for a peptide of comparable size.

Notes on identity

The molecular formula C21H21F3N2O4 is consistent with the reported molecular weight of 422.40 g/mol. The trifluoromethyl substituent is a common medicinal-chemistry motif used to improve metabolic stability and modulate lipophilicity, and its presence is what distinguishes SLU-PP-332 from earlier ERR ligand scaffolds in the same laboratory's chemistry series.

Because the compound is a small molecule rather than a peptide, the stability considerations differ from most products in this catalog: there is no disulfide bond to worry about, no methionine oxidation to protect against, and no lyophilized-to-solution reconstitution step. The relevant concerns are instead standard for a lipophilic organic solid — protection from light, humidity, and prolonged heat.

SLU-PP-332 capsules should be stored in the sealed original bottle with the desiccant in place. The stability profile of a small-molecule organic solid differs meaningfully from that of a lyophilized peptide, and the following notes apply specifically to this capsule format.

Recommended storage conditions

• Long-term (months): Refrigerated at 2–8°C in the sealed bottle. This is the most conservative option and is appropriate for stock that will not be used quickly.
• Working stock (weeks): Controlled room temperature (15–25°C), away from direct light and heat sources.
• Transit: Ambient temperatures for brief periods (days) are acceptable for a solid organic compound of this class; extended exposure to elevated temperatures (>30°C) should be avoided.

Compound-specific stability notes

The trifluoromethyl group in SLU-PP-332 contributes to metabolic stability but does not change the general handling profile — this is still an organic solid subject to the usual degradation pathways of small molecules: hydrolysis (if moisture ingress occurs), oxidation, and photodegradation. The two most important practical measures are:

1. Keep the desiccant in the bottle. Humidity is the single largest contributor to shelf-life loss for capsule products.
2. Protect from light. The bottle should be opaque or stored inside a closed drawer or cabinet. Do not leave capsules exposed on a benchtop under fluorescent lighting for extended periods.

What is not established

Formal accelerated stability data for SLU-PP-332 in the specific capsule matrix used here has not been published. Recommendations above are general best practices for small-molecule solid-dosage research reagents rather than compound-specific validated shelf-life claims. Users conducting long-duration studies should consider periodic re-analysis (e.g., HPLC) if drift in results is suspected.

The product is supplied for laboratory research use only. It is not intended for human or veterinary use.