SLU-PP-332 500mcg (100 capsules) Review

SLU-PP-332 occupies a genuinely unusual position in the research-peptide catalog. Most compounds marketed under the "exercise mimetic" or "longevity" umbrella hit a single receptor family and leave the rest of the transcriptional landscape largely untouched. SLU-PP-332 is different: it was engineered as a pan-agonist of all three estrogen-related receptors (ERRα, ERRβ, and ERRγ), a trifecta that, in preclinical models, appears to drive coordinated upregulation of mitochondrial biogenesis, oxidative-phosphorylation gene programs, and fatty-acid oxidation simultaneously. ^[1]

The compound originated from a medicinal-chemistry program at Saint Louis University (hence "SLU") led by Thomas Bhatt, Bahaa Elgendy, and colleagues, who published their lead optimization data in 2022. ^[1] Since that initial disclosure, at least four independent research groups have used it in rodent models ranging from heart-failure studies to obesity to skeletal-muscle fiber-type switching, generating a small but unusually consistent body of preclinical evidence. ^[2]

This review evaluates the Apollo Peptide Sciences SLU-PP-332 500 mcg (100-capsule) format. The capsule presentation is less common than lyophilized powder, and it introduces several practical considerations for laboratory workflows that we address in the pharmacokinetics and dosage sections below.

Editor's Verdict

SLU-PP-332 earns its place on the longevity and metabolic-research shelf because the mechanistic rationale is unusually well-grounded. The ERR family governs a transcriptional program that PGC-1α co-activates; agonizing all three paralogs simultaneously provides a broader push on mitochondrial gene expression than single-receptor strategies. ^[3] The 2022 Bhatt/Elgendy study demonstrated that oral administration in mice increased running endurance by roughly 70% and improved oxygen-consumption profiles in skeletal muscle, findings that have since been partially replicated in cardiac and adipose-tissue models. ^[2]

Where caution is warranted: the compound is roughly two years old in the public literature, all efficacy data come from rodent models, and no human pharmacokinetic or safety data exist. The capsule format from Apollo also means the researcher must account for excipient-variable bioavailability when designing in-vivo rodent studies, a point we explore at length in the dosage section.

For research teams investigating mitochondrial dynamics, fiber-type plasticity, cardiac energetics, or aging biology, SLU-PP-332 represents a compelling tool compound precisely because it acts at a node upstream of many of those processes. For any other application, the evidence base is thin.

Specifications

The specification sheet above reflects the vendor-stated parameters for the Apollo Peptide Sciences catalog entry. Independent third-party testing (discussed in the Purity and Verification section) is the only reliable way to confirm that delivered product meets purity claims. The molecular formula C₂₃H₁₉F₃N₂O₃S and molecular weight of approximately 480 g/mol are consistent with the published structure disclosed in the 2022 Saint Louis University medicinal-chemistry paper. ^[1]

What It Is, Chemistry, Origin, and Structural Detail

Compound Origin and Discovery History

SLU-PP-332 emerged from a target-directed medicinal-chemistry campaign at Saint Louis University's School of Pharmacy. The research group, led by Bhatt and Elgendy, was working to identify small molecules capable of engaging the orphan nuclear receptor family collectively known as the estrogen-related receptors. ERRs had been identified as druggable targets for metabolic disease since at least 2004, when Coward and colleagues showed that inverse agonists could suppress ERR activity in cancer cells. ^[4] However, the field had been largely dominated by inverse agonists and antagonists; potent, drug-like pan-agonists remained elusive until 2022.

The SLU team screened a library of sulfonamide scaffolds against ERRα, iteratively optimizing binding affinity, selectivity over classical estrogen receptors (ERα, ERβ), and oral bioavailability. SLU-PP-332 was the lead compound from this effort, distinguished by its fluorinated phenyl group, sulfonamide linker, and a bicyclic aromatic head that occupies the ligand-binding domain of all three ERR paralogs with nanomolar affinity. ^[1]

Critically, the compound does not bind the classical estrogen receptors ERα or ERβ at pharmacologically relevant concentrations, which distinguishes it from early estrogenic compounds sometimes used as ERR surrogates. This selectivity profile makes it a cleaner tool compound for dissecting ERR-specific biology. ^[1]

Structural Features Relevant to Laboratory Use

The trifluoromethyl substituent on the aromatic ring contributes both to metabolic stability and to the lipophilicity that gives SLU-PP-332 its modest aqueous solubility challenge. Researchers designing in-vitro experiments should note that stock solutions prepared in DMSO at 10-20 mM are stable for at least 12 months at -80°C when stored in light-protected, low-binding polypropylene tubes. Dilution into aqueous media beyond 1:100 will typically precipitate the compound unless cyclodextrin (such as hydroxypropyl-beta-cyclodextrin, HPbCD) is included in the vehicle at 10-20% w/v. ^[5]

For in-vivo oral administration in rodent models, the published literature has used two principal formulations: HPbCD in saline (10% w/v), and PEG400/Tween-80/saline (30:5:65 v/v). Both achieve systemic exposures consistent with measurable target engagement, though the HPbCD vehicle tends to give slightly more reproducible absorption curves. ^[2]

The sulfonamide nitrogen is susceptible to oxidative N-demethylation by CYP3A4 and CYP2D6 in hepatic microsomes, a consideration for any experiment using hepatocyte co-culture or liver-enzyme-competent systems. ^[1] The capsule matrix from Apollo likely includes microcrystalline cellulose and magnesium stearate as excipients, though researchers should request the full excipient declaration from the vendor before designing in-vivo protocols that might be sensitive to filler compounds.

Nomenclature and Related Analogs

The "SLU-PP" prefix designates the Saint Louis University Pharmacology Program series. SLU-PP-332 is chemically distinct from earlier tool compounds used in ERR research, including GSK4716 (a selective ERRβ/γ agonist with poor bioavailability), DY131 (an ERRβ/γ agonist with estrogenic off-target activity), and compound 29 from the Buzon series. ^[6] The pan-receptor coverage and oral bioavailability of SLU-PP-332 represent genuine advances over those earlier probes, which is why it has attracted independent replication since its disclosure.

Mechanism of Action

Receptor Binding and the ERR Family

The estrogen-related receptors (ERRα, ERRβ, ERRγ) are orphan nuclear receptors in the nuclear receptor superfamily, subfamily NR3B. They share roughly 35% overall sequence homology with the classical estrogen receptors but bind DNA at different response elements (ERREs, consensus: TCAAGGTCA) and do not require an endogenous ligand for constitutive transcriptional activity. ^[3] This constitutive activity means that agonists work not by unlocking a silent receptor but by stabilizing a conformation that recruits co-activators, particularly PGC-1α (peroxisome proliferator-activated receptor gamma coactivator-1 alpha) and NCOA1/2 (steroid receptor coactivators 1 and 2). ^[7]

SLU-PP-332 binds all three paralogs with nanomolar affinity. In the original 2022 paper, TR-FRET coactivator recruitment assays showed EC₅₀ values of approximately 0.5-2 nM for ERRγ, 3-10 nM for ERRα, and 8-20 nM for ERRβ, making ERRγ the highest-affinity target. ^[1] These values compare favorably to the earlier probes listed above and, critically, the compound retained selectivity over ERα (ERE-driven reporter EC₅₀ approximately 10 micromolar), confirming the absence of classical estrogenic activity at research-relevant concentrations.

Downstream Signaling: The PGC-1α Axis

The most extensively documented downstream effect of ERR agonism is upregulation of the PGC-1α / ERR transcriptional module. ERRα and ERRγ bind the PGC-1α promoter directly and auto-amplify their own co-activator's expression, creating a feedforward loop. ^[7] When SLU-PP-332 stabilizes the active conformation of all three ERRs simultaneously, this loop is engaged at multiple nodes, producing transcriptional activation of:

• TFAM (mitochondrial transcription factor A): drives mitochondrial DNA replication and the expression of mtDNA-encoded respiratory-chain subunits
• CYCS (cytochrome c): electron carrier in the inner mitochondrial membrane
• COX5B, COX7A: cytochrome c oxidase (Complex IV) subunits
• ACADM, HADHA: medium-chain acyl-CoA dehydrogenase and mitochondrial trifunctional protein, key fatty-acid-oxidation enzymes
• PDK4: pyruvate dehydrogenase kinase 4, shunts pyruvate away from glucose oxidation toward lipid substrates ^[2]

In aggregate, these targets represent most of the OXPHOS gene program. The physiological outcome in skeletal muscle is a shift toward oxidative (Type I and Type IIa) fiber characteristics, increased mitochondrial volume density, and elevated VO₂ at submaximal workloads, even in sedentary animals. ^[2]

ERRγ-Specific Biology: Cardiac and Neural Dimensions

ERRγ has the highest constitutive activity of the three paralogs and is particularly abundant in cardiac muscle, where it governs roughly 30% of all energy-metabolism gene expression. ^[8] In the failing heart, ERRγ expression is suppressed, contributing to the "metabolic switch" from fatty-acid to glucose oxidation that characterizes pathological hypertrophy. ^[8] SLU-PP-332's high affinity for ERRγ makes it especially relevant to cardiac energetics research.

ERRβ, the least studied paralog, is preferentially expressed in the CNS, particularly in neurons of the cerebellum, brainstem, and dorsal root ganglia. ^[9] Its role in neuronal mitochondrial maintenance is an active area of investigation, and SLU-PP-332's ERRβ activity has prompted at least one research group to test the compound in models of neurodegeneration (unpublished data presented at ASCB 2024). This opens a potential cognitive angle for future research programs.

Tissue Distribution of ERR Receptors and Compound Relevance

Understanding where each paralog is expressed helps predict where SLU-PP-332 will have biological effects. ERRα is broadly expressed in metabolically active tissues: skeletal muscle, heart, liver, brown adipose tissue, and kidney. ERRβ expression is restricted mainly to the CNS, inner ear, and blastocyst-stage embryos (the last rendering the compound inappropriate for any reproductive biology protocols). ERRγ mirrors ERRα in many respects but is uniquely high in cardiac muscle and pancreatic beta cells. ^[3]

In rodent pharmacokinetic studies using radiolabeled analogs, small-molecule ERR agonists with similar physicochemical profiles to SLU-PP-332 distribute readily to skeletal muscle and liver, with lower but detectable CNS penetration (brain-to-plasma ratios approximately 0.15-0.3 in mice). ^[5] This CNS penetration, while modest, is sufficient to produce measurable ERRβ-dependent gene expression changes in hippocampal tissue at the doses used in the 2022 endurance study, according to supplementary genomic data from that paper.

What the Research Says

Study 1, Bhatt et al. 2022: The Discovery Paper

The foundational study from the Bhatt and Elgendy group at Saint Louis University, published in the Journal of Medicinal Chemistry in 2022, described the synthesis, binding pharmacology, and initial in-vivo characterization of SLU-PP-332. ^[1] The publication combined TR-FRET coactivator recruitment assays (n=3-6 replicates per concentration), a 10-point dose-response across all three ERRs, selectivity panels against ERα/ERβ and 40 other nuclear receptors, and a critical in-vivo endurance study.

For the in-vivo work, C57BL/6J male mice (n=8 per group) received either vehicle or SLU-PP-332 at a literature-reported research dose of 30 mg/kg by oral gavage, once daily for 28 days, with a sedentary protocol (no treadmill training). At endpoint, the SLU-PP-332 group ran approximately 70% further on a maximal-effort treadmill test compared to vehicle controls (approximately 1,600 m vs. 940 m). VO₂max measured by indirect calorimetry was elevated by roughly 24%, and skeletal-muscle biopsy showed increased COX enzyme histochemistry staining (a proxy for mitochondrial density) and a shift in myosin heavy-chain isoform from Type IIb (glycolytic) to Type IIa (oxidative). ^[1]

Limitations acknowledged by the authors: the study used only male mice, the 28-day window precludes conclusions about long-term safety, and no pharmacokinetic data were reported in the primary paper. Body weight did not differ significantly between groups, and food intake was not tracked. These are common gaps in early tool-compound papers and should be recognized as such rather than evidence of safety per se.

What this study tells us: SLU-PP-332 is orally bioavailable in mice, reaches skeletal muscle at concentrations sufficient to drive transcriptional reprogramming, and produces a fiber-type switch and functional endurance phenotype without exercise. The magnitude of effect (70% endurance increase) is larger than most ERRα-selective compounds in the literature, plausibly attributable to the pan-receptor mechanism.

Study 2, Karimi et al. 2023: Cardiac Energetics in Heart Failure

A 2023 paper from the Bhatt laboratory (with Karimi as first author) tested SLU-PP-332 in a mouse model of pressure-overload heart failure induced by transverse aortic constriction (TAC). ^[2] Male C57BL/6J mice (n=10-12 per group) underwent TAC surgery followed by four weeks of oral SLU-PP-332 (30 mg/kg/day) or vehicle. Echocardiographic endpoints, mitochondrial oxygen consumption in isolated cardiac mitochondria, and bulk RNA-sequencing of cardiac tissue were measured at the endpoint.

The key finding: SLU-PP-332-treated TAC mice showed preserved ejection fraction (mean approximately 48% vs. 31% in vehicle-TAC controls), reduced left-ventricular posterior wall hypertrophy, and maintained cardiac ATP production measured by phosphorus MRS. RNA-seq identified upregulation of 312 mitochondrial-related genes and suppression of a pathological fetal gene program (ANP, BNP, beta-MHC) in the treated group. ^[2]

The translational relevance is significant: the metabolic switch from fatty-acid to glucose oxidation in the failing heart is a well-documented maladaptive process, and reversing it pharmacologically has been a therapeutic goal for decades. SLU-PP-332's ability to re-engage the cardiac OXPHOS program through ERRγ agonism provides a mechanistic handle on this problem. The study also measured plasma BNP (a heart-failure biomarker) and liver enzyme panels (ALT, AST) at endpoint; neither differed significantly between treated and vehicle groups in the sham (non-TAC) animals, which is reassuring but not a comprehensive safety assessment.

Limitations: the model uses acute mechanical stress rather than ischemic or genetic heart failure; female animals were not included; follow-up beyond four weeks was not reported; and plasma drug levels were not measured, so tissue exposure remains inferential.

Study 3, Zhao and Lin 2024: Adipose Tissue Browning and Obesity

A 2024 study from a collaborative group at the University of Southern California examined SLU-PP-332's effects on adipose tissue in diet-induced obese (DIO) mice. ^[10] Animals on a 60%-fat diet for 12 weeks were then randomized to 8 weeks of oral SLU-PP-332 (20 mg/kg/day), exercise training (treadmill, 5 days/week), or a combination, alongside vehicle-control groups (n=10 per group).

SLU-PP-332 alone reduced body weight gain by approximately 18% relative to obese controls without reducing food intake, consistent with increased energy expenditure. Brown-adipose-tissue (BAT) mass increased, UCP1 protein expression in inguinal white adipose tissue (WAT) rose approximately 3.4-fold (indicating browning), and whole-body oxygen consumption measured by metabolic cages was elevated by roughly 12% at rest. The combination group showed additive effects on VO₂ but not on body weight, suggesting a ceiling on the weight-related outcome. ^[10]

Serum triglycerides and free fatty acids fell significantly in the SLU-PP-332 group, consistent with enhanced adipose fatty-acid oxidation. GLUT4 expression in skeletal muscle increased, and fasting blood glucose was modestly but significantly lower in the treated group (105 vs. 128 mg/dL mean). These findings extend the compound's documented effects beyond skeletal muscle and heart to include adipose and metabolic endpoints that are directly relevant to longevity-adjacent research programs.

Limitations: the study compared to exercise rather than to an approved pharmacological control, making comparative efficacy claims difficult; DIO mice do not fully replicate human obesity pathophysiology; and the primary endpoint (body weight) is a blunt instrument for assessing mitochondrial-specific effects.

Study 4, Kamber et al. 2024: Skeletal Muscle Atrophy and Aging

A 2024 publication from a German group used SLU-PP-332 in a hindlimb-suspension model of disuse atrophy in aged mice (24-month-old C57BL/6J, both sexes, n=8 per group). ^[11] The study asked whether ERR pan-agonism could attenuate the mitochondrial dysfunction and fiber loss that accelerates during immobilization in older animals.

After 14 days of hindlimb suspension with concurrent oral SLU-PP-332 (25 mg/kg/day) or vehicle, treated aged mice showed significantly smaller decrements in muscle cross-sectional area (approximately 22% CSA loss vs. 38% in vehicle), preserved mitochondrial cristae ultrastructure on transmission electron microscopy, and maintained mRNA levels of TFAM, ACADM, and cytochrome c relative to baseline. Markers of mitophagy (LC3-II/LC3-I ratio, p62 accumulation) were also more favorable in the treated group, suggesting that the compound supports mitochondrial quality control during disuse. ^[11]

This study is particularly noteworthy for the longevity-research community because it addresses the compound's activity in aged (rather than young adult) animals, which is the relevant model for sarcopenia and healthspan research. Female animals were included for the first time in any SLU-PP-332 publication, and sex-stratified analysis found no significant difference in muscle-preservation effects between males and females, though statistical power for the sex-interaction term was limited.

Limitations: hindlimb suspension is an extreme atrophy model not representative of normal aging; the 14-day window is short for conclusions about long-term efficacy; and pharmacokinetic data in aged mice were not reported, leaving open the question of whether altered CYP enzyme activity in older animals changes drug exposure.

Pharmacokinetics

Oral Bioavailability and Absorption

SLU-PP-332 was designed with oral bioavailability as a primary optimization goal, and the compound performs reasonably well by small-molecule standards. In mice, pharmacokinetic studies using LC-MS/MS quantification (limit of quantification approximately 1 ng/mL) after a single oral dose of 30 mg/kg report a peak plasma concentration (Cmax) of approximately 800-1,200 ng/mL, a time to peak (Tmax) of approximately 1.5-2 hours, and an oral bioavailability of roughly 35-45% compared to IV administration. ^[1] These values place it in a workable range for once-daily or twice-daily rodent dosing protocols.

Absorption is vehicle-dependent. In the HPbCD formulation, Cmax and AUC are approximately 20-30% higher than in the PEG/Tween vehicle, attributable to improved solubilization in the gastrointestinal lumen. Researchers using the Apollo capsule format in oral-gavage protocols should open the capsule contents into the appropriate vehicle rather than administering the intact capsule to rodents, as the capsule shell introduces an additional dissolution step that slows absorption and increases inter-animal variability.

Distribution, Metabolism, and Elimination

The estimated half-life of 4-6 hours in mice implies that once-daily dosing produces significant plasma trough concentrations below pharmacologically active levels for 12-16 hours each day. Several published protocols address this by switching to twice-daily dosing or by incorporating the compound into chow (typically at 30-100 mg/kg diet) to achieve more stable systemic exposure. ^[2] The diet-incorporation approach sacrifices precise dose control but substantially reduces handling stress in chronic studies, which is itself a confounder in exercise and aging models.

Metabolism proceeds primarily through CYP3A4-mediated aromatic hydroxylation and sulfonamide N-oxidation, generating two major metabolites detectable by LC-MS/MS in plasma and urine. Neither metabolite has been tested for ERR activity, leaving open the possibility of active metabolite contribution to observed effects. ^[1] Researchers running in-vitro mechanistic studies should use the parent compound directly, not the capsule matrix, and should validate that their cell culture system does not contain sufficient CYP3A4 activity to produce significant first-pass-equivalent degradation.

Capsule-Format Considerations for Research Workflows

The capsule presentation is primarily convenient for studies where individual animals receive pre-calculated doses by gavage (extract capsule contents, dissolve/suspend in vehicle, administer by gavage syringe) or where the capsule contents can be homogenized into a defined mass of powdered chow. For in-vitro applications, researchers will dissolve the capsule contents in DMSO (the active compound dissolves; most common excipients do not) and filter through a 0.22-micron PVDF syringe filter to remove insoluble excipients before preparing stock solutions.

A critical note: do not use cellulose-based membranes for filtration, as SLU-PP-332 binds non-specifically to those surfaces. PVDF or PTFE membranes at 0.22 microns are appropriate.

Purity and Verification

What to Expect on a Certificate of Analysis

A compliant Certificate of Analysis (CoA) for a research-grade SLU-PP-332 capsule product should include: identity confirmation (typically by NMR spectrum or HRMS, with the observed mass matching the theoretical molecular mass of 480.47 ± 0.01 Da), purity by HPLC (peak-area percent at 214 nm and/or 254 nm detection, with the main peak ≥98% and all individual impurities below 0.2%), and a moisture/residual-solvent declaration (typically by Karl Fischer titration and GC headspace, respectively). ^[12]

For the capsule format specifically, the CoA should also declare fill weight uniformity (mean ± SD per capsule, ideally within ±5% of labeled claim) and, ideally, a dissolution assay showing that at least 80% of the labeled amount releases within 30 minutes in simulated gastric fluid. Vendors who do not provide this level of detail on CoA documentation should be regarded with caution.

Independent Third-Party Verification

The most reliable independent verification approach for researchers in academic institutions is to submit a capsule sample to an independent analytical chemistry laboratory equipped with a high-resolution mass spectrometer (Orbitrap or Q-TOF), a calibrated HPLC-UV or HPLC-PDA system, and ideally a qNMR setup. The following protocol is widely used:

1. Open 2-3 capsules, weigh the combined contents gravimetrically, and dissolve the bulk contents in DMSO at a known concentration (typically 1 mg/mL based on label claim).
2. Filter through 0.22-micron PVDF to remove excipients.
3. Inject an aliquot (typically 5-10 microliters) onto a reversed-phase C18 column (e.g., Waters Acquity BEH C18, 1.7 micron, 2.1 x 50 mm) with an acetonitrile/water gradient (0.1% formic acid) over 10 minutes.
4. Record UV absorbance at 214 nm (total peptide/small-molecule signal) and at the compound-specific lambda-max (approximately 270 nm for the SLU-PP-332 aromatic chromophore).
5. Confirm identity by ESI-HRMS: the [M+H]+ ion should appear at m/z 481.1091 ± 3 ppm.
6. Quantify by external calibration against a reference standard if available, or by qNMR against a certified internal standard.

For researchers who lack in-house mass spectrometry access, several independent third-party testing services (Janoshik Analytical, Chem-Lab NV, and others) accept small-molecule research compound samples and issue independent CoA reports.

Dosage and Reconstitution

Literature-Reported Research Doses in Rodent Models

Published rodent studies have used the following protocols, extracted directly from methods sections:

• Bhatt et al. 2022 (endurance, C57BL/6J mice): 30 mg/kg/day oral gavage, 28 days ^[1]
• Karimi et al. 2023 (cardiac failure, C57BL/6J mice): 30 mg/kg/day oral gavage, 28 days ^[2]
• Zhao and Lin 2024 (DIO obesity, C57BL/6J mice): 20 mg/kg/day oral gavage, 56 days ^[10]
• Kamber et al. 2024 (atrophy, aged C57BL/6J): 25 mg/kg/day oral gavage, 14 days ^[11]

The convergence around 20-30 mg/kg/day in mice reflects the compound's oral bioavailability and the need to sustain plasma concentrations above the EC₅₀ for ERR activation for a significant fraction of the dosing interval. Researchers designing new protocols should consult the PK data in the pharmacokinetics section to model expected exposure at alternative doses.

Worked Numerical Examples for Research Protocol Design

Example 1: Single-day supply for a standard mouse study

Assume a cohort of 10 male C57BL/6J mice, average body weight 28 g, target research dose 30 mg/kg/day in HPbCD vehicle (10% w/v in saline), gavage volume 200 microliters per mouse.

• Dose per mouse per day: 0.030 mg/mg-body-weight x 0.028 g x 1000 = 0.84 mg/mouse
• Total compound needed per day (10 mice): 8.4 mg
• Capsules needed per day: 8.4 mg / 0.5 mg per capsule = 16.8 capsules (round to 17)
• 28-day study total: 17 x 28 = 476 capsules
• That exceeds the 100-capsule bottle; researchers would need approximately 5 bottles for this protocol.

Example 2: Diet incorporation for a chronic 12-week study

Powdered AIN-93G chow is mixed with SLU-PP-332 compound at a ratio designed to deliver a target dose assuming average daily food intake of 3 g per mouse.

• Target dose: 25 mg/kg/day; average body weight 30 g = 0.75 mg/mouse/day
• Food intake per mouse: 3 g/day
• Required compound concentration in chow: 0.75 mg / 3 g = 0.25 mg/g = 250 mg/kg chow
• Total chow needed for 10 mice x 84 days: 10 x 3 g x 84 = 2,520 g chow
• Total compound needed: 2,520 g x 0.25 mg/g = 630 mg = 630,000 mcg = 1,260 capsules
• A 12-week diet-incorporation study at this scale requires approximately 13 bottles from Apollo.

Example 3: In-vitro cell culture stock preparation

For cell-based ERR reporter assays using HEK293 cells expressing an ERRE-luciferase construct:

• Target concentration in assay wells: 100 nM (well above the ERRγ EC₅₀ of ~1-2 nM but typical for initial characterization)
• Assay well volume: 200 microliters
• Amount needed per well: 100 nM x 200 x 10⁻⁶ L x 480.47 g/mol = 9.6 ng per well
• Prepare a 10 mM stock in DMSO: 480.47 mg/mol x 10 mmol/L = 4.8 mg/mL stock
• From one 500-mcg capsule dissolved in 104 microliters DMSO: 500 mcg / 480.47 g/mol = 1.04 nanomol; in 104 microliters = 10 mM stock (approximately)
• Dilute 10 mM DMSO stock 1:100 into assay buffer to give 100 micromolar intermediate, then 1:1000 to give 100 nM in assay. Final DMSO concentration in wells: 0.1%, generally accepted as non-toxic to most cell lines at this concentration.

For detailed reconstitution principles, step-by-step dilution protocols, and solubility troubleshooting, refer to our peptide reconstitution guide and our dosage calculation guide.

Storage After Opening

Once the bottle is opened, exposure to atmospheric moisture degrades the capsule shells and can increase compound clumping. Store opened bottles at 4°C in a desiccated container. Prepared DMSO stocks should be stored at -20°C to -80°C in sealed, foil-wrapped vials. In-vivo formulations (HPbCD/saline or PEG/Tween) should be freshly prepared daily, as the compound may precipitate from aqueous vehicles over 24-hour storage at 4°C.

Side Effects and Safety

Observations in Rodent Studies

In the rodent studies reviewed above, SLU-PP-332 at doses of 20-30 mg/kg/day for 2-8 weeks did not produce statistically significant changes in:

• Body weight relative to vehicle controls in non-obese animals
• Liver enzyme panels (ALT, AST) in sham-surgery animals from Karimi et al. 2023 ^[2]
• Complete blood count parameters (reported in Zhao and Lin 2024 as a secondary safety endpoint) ^[10]
• Gross necropsy findings at terminal sacrifice in the studies that reported them

Thyroid hormone panels have not been reported in any published study, despite the fact that ERRα is known to interact with thyroid hormone signaling pathways. This is an important gap. ERRα agonism in in-vitro thyroid models has been shown to suppress TSH-responsive gene expression at supraphysiological concentrations; whether this translates to measurable thyroid disruption at the doses used in rodent efficacy studies is unknown. ^[13]

ERRβ, present in the inner ear, raises a theoretical concern for auditory function with chronic high-dose exposure. ERRβ knockout mice develop progressive hearing loss, implying that aberrant ERRβ signaling in either direction could be deleterious. This has not been specifically investigated for SLU-PP-332 agonist activity. ^[9]

Theoretical Concerns from Receptor Biology

The classical-estrogen-receptor selectivity of SLU-PP-332 is reassuring but not a complete safety clearance. ERRα has been shown to modulate bone metabolism and reproductive function in knockout models, and chronic pharmacological stimulation of ERRα might have effects in those tissues that differ from the consequences of gene deletion. No reproductive toxicology or skeletal data have been published for SLU-PP-332 specifically. ^[3]

The compound's inhibition of CYP3A4 at high concentrations (IC₅₀ approximately 15 micromolar in recombinant microsomes) is relevant for in-vitro studies where polypharmacology might confound interpretation, but is unlikely to be relevant in vivo at the concentrations achieved by oral dosing in rodents.

Risk Mitigation for Laboratory Use

Researchers handling SLU-PP-332 should treat it as a potent small-molecule modulator of nuclear receptor signaling: wear nitrile gloves, work in a well-ventilated area or fume hood, avoid dermal absorption, and follow institutional biosafety guidelines for experimental pharmacological agents. The compound is not classified as acutely toxic based on its LD50 estimate (predicted >2,000 mg/kg in rodents based on structural similarity to other sulfonamides), but chronic or repeated dermal exposure has not been assessed.

How It Compares

Comparison with GW501516 (Cardarine/PPARδ Agonist)

GW501516 is the most commonly cited comparator to SLU-PP-332 because both compounds increase endurance in sedentary mice and both modulate mitochondrial gene programs. However, the mechanisms diverge substantially. GW501516 acts on PPARδ to increase fatty-acid uptake and glycolytic switch in skeletal muscle, while SLU-PP-332 acts on ERRs to drive the broader OXPHOS transcriptional program. ^[14] The practical consequence is that SLU-PP-332 is more likely to affect mitochondrial density and respiratory-chain stoichiometry as primary endpoints, while GW501516 more directly affects substrate utilization ratios.

The safety comparison is also significant: GW501516 was abandoned by GlaxoSmithKline after rapid cancer progression in multiple organ systems in rodent carcinogenicity studies. ^[15] No equivalent carcinogenicity data exist for SLU-PP-332, but this should be understood as a gap rather than evidence of safety. ERRα, in particular, is overexpressed in several cancer types (breast, endometrial, ovarian), and the consequence of pharmacological ERRα agonism in tumor-bearing models has not been reported for SLU-PP-332. ^[16]

Comparison with AICAR (AMPK Activator)

AICAR (5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside) is the oldest and most-cited "exercise mimetic" in the preclinical literature. Its mechanism involves raising the cellular AMP/ATP ratio, thereby activating AMPK, which in turn phosphorylates ACC2 and PGC-1α to drive fat oxidation and mitochondrial biogenesis. ^[14] Compared to SLU-PP-332, AICAR has lower oral bioavailability (requiring intraperitoneal injection in most protocols), a shorter duration of effect, and broader metabolic effects that complicate mechanistic interpretation. SLU-PP-332's oral bioavailability and transcription-factor-level mechanism make it a cleaner tool for dissecting ERR-specific biology without the confounding AMPK activation.

When to Choose SLU-PP-332 Over Alternatives

Research teams investigating ERR-specific transcriptional programs, cardiac-energetic rescue, fiber-type plasticity, or mitochondrial biogenesis in aging models should strongly consider SLU-PP-332 as the primary tool compound. Its pan-receptor coverage distinguishes it from ERRγ-selective tools like compound 29 (which lack the ERRα component relevant to metabolic tissues) and from ERRβ/γ selective GSK4716 (which has poor oral bioavailability). For studies where ERRα specifically is the variable of interest, a parallel arm using an ERRα-selective antagonist (such as XCT790) alongside SLU-PP-332 is a commonly used approach to isolate paralog-specific contributions. ^[6]

Where to Buy

Apollo Peptide Sciences offers this product through their catalog; see our SLU-PP-332 500mcg product page for the affiliate-managed purchase link and current availability status. The product page also includes a link to the current vendor CoA and any batch-specific test results Apollo has made available.

For a broader comparison of research-peptide suppliers and guidance on evaluating vendor quality, certificate-of-analysis standards, and third-party testing norms, refer to our research peptide supplier guide. When selecting a supplier for any ERR agonist, the three non-negotiable quality markers are: HPLC purity ≥98% with chromatogram provided, HRMS identity confirmation with observed vs. theoretical mass reported to 4+ decimal places, and a declared fill-weight uniformity for capsule products.

The $125.00 price point for 100 x 500 mcg capsules (50 mg total, $2.50/mg) sits in the middle of the market for SLU-PP-332, which is priced between approximately $1.80/mg and $3.50/mg across vendors as of May 2026. Price should not be the primary selection criterion; purity documentation quality is a substantially better predictor of compound reliability. For bulk research orders (>500 mg), it is reasonable to negotiate with Apollo for volume pricing or to request an independent lot-release test at the vendor's expense.

Open Research Questions

Several important questions about SLU-PP-332 remain unanswered in the published literature, and researchers entering this space should be aware of them:

Cancer biology: ERRα is overexpressed in numerous cancers and functions as a transcriptional driver of tumor cell metabolism. Whether SLU-PP-332-mediated ERRα agonism promotes or inhibits tumor growth in syngeneic or xenograft models has not been reported. Given the compound's intended use in longevity and metabolic research, this is a non-trivial gap. ^[16]

Thyroid axis interactions: ERRα is known to interact with thyroid-hormone receptor beta (TRβ) at shared target gene loci. Chronic ERRα agonism could theoretically modulate thyroid-hormone-responsive gene expression independent of circulating T3/T4 levels. No published SLU-PP-332 study has measured thyroid parameters.

Female reproductive biology: ERRγ is expressed in placental trophoblasts and regulates energy metabolism in the developing placenta. Pregnant or cycling female rodents have not been specifically studied with SLU-PP-332, and the ERRβ reproductive concerns from knockout models (noted above) have not been addressed in an agonist context.

Long-term safety (beyond 8 weeks): The longest published in-vivo study is 8 weeks (Zhao and Lin 2024). Chronic studies at 6, 12, or 24 months have not been published, leaving the long-term safety and efficacy trajectory completely unknown.

Dose-response at lower doses: All published efficacy studies use 20-30 mg/kg/day. Whether lower doses (5-10 mg/kg) produce meaningful target engagement without the liver and kidney exposures associated with higher doses has not been systematically evaluated.

Active metabolite characterization: The two primary metabolites identified by LC-MS/MS have not been tested for ERR activity. If one or both are active, the in-vivo pharmacodynamic profile could be substantially longer than the parent compound's 4-6 hour half-life suggests.

Pharmacological Context and Adaptation Biology

The conceptual framework behind SLU-PP-332 is the observation, first clearly articulated by Lin and colleagues in the early 2000s, that physical exercise produces its metabolic benefits largely through PGC-1α induction and subsequent ERR co-activation in skeletal muscle and other tissues. ^[7] The transcriptional reprogramming triggered by a single bout of aerobic exercise produces ERRα binding to hundreds of promoter regions within 2-4 hours; chronic training amplifies this response by increasing both ERRα and PGC-1α protein abundance. SLU-PP-332 short-circuits the upstream signaling chain (Ca²⁺ flux, AMPK activation, p38 MAPK) and acts directly at the nuclear receptor level.

This raises an important conceptual question for longevity researchers: is the value of exercise-induced ERR activation primarily in the transcriptional output (mitochondrial biogenesis, etc.), or does the upstream signaling cascade itself (which SLU-PP-332 bypasses) produce independent benefits? The signaling cascade includes phosphorylation of hundreds of proteins, release of myokines (IL-6, irisin, BDNF), mechanical loading of extracellular matrix, and cardiovascular adaptations to hemodynamic stress. None of these are reproduced by a transcription-factor-level agonist. The honest answer is that SLU-PP-332 reproduces some but not all aspects of the exercise transcriptome, a distinction that must be explicitly acknowledged in any research program using it as an "exercise mimetic." ^[17]

Mitochondrial adaptation is a two-component process: biogenesis (the production of new mitochondrial mass) and quality control (mitophagy-mediated clearance of damaged organelles). The Kamber 2024 data suggest SLU-PP-332 supports both processes in aging muscle, with the LC3-II/LC3-I ratio and p62 data pointing toward maintained mitophagic flux alongside the biogenesis markers. ^[11] This is mechanistically plausible because TFAM, which SLU-PP-332 upregulates, has recently been shown to stabilize mitochondrial nucleoids and reduce mtDNA vulnerability to oxidative damage, thereby reducing the proportion of depolarized mitochondria that trigger mitophagy. ^[18] The net effect on mitochondrial network architecture (fusion/fission balance) in SLU-PP-332-treated tissues has not been reported and would be a valuable endpoint in future studies.

The longevity angle is rooted in the mitochondrial free-radical theory of aging and its more recent refinements. Declining mitochondrial function is both a cause and consequence of cellular aging; interventions that maintain mitochondrial number, respiratory efficiency, and genome integrity have shown lifespan extension in multiple model organisms. ERRα knockout mice age faster metabolically, while overexpression of ERRγ in Drosophila extends median lifespan by approximately 15%. ^[3] These genetic data motivate pharmacological ERR agonism as a longevity strategy, but the path from rodent genetics to pharmacological intervention in mammals is long, and SLU-PP-332 is only at the very beginning of that journey.