KDC-MN-1344 – Kodiac biolabs

Our opinion on this compoundNovel, promising

61/100

First credible pan-ERR tool compound with striking preclinical endurance data but thin replication and no human signal yet

Look, the exercise mimetic space has a complicated history. GW501516 was the one everyone wanted – PPARδ agonism, real endurance gains in animals – and then the carcinogenicity signal killed it. AICAR works through AMPK but bioavailability is terrible for anything beyond acute injection studies. The field needed a different lever, and SLU-PP-332 is the most credible candidate that’s appeared in the past several years.

The mechanism targets the estrogen-related receptor family – ERRα, ERRβ, ERRγ – which are orphan nuclear receptors that don’t bind estrogen but share structural homology with the classical ER. What they actually do is coordinate the transcriptional response to exercise: mitochondrial biogenesis, fatty acid oxidation, oxidative phosphorylation, slow-twitch fiber phenotype. ERR activity is co-induced with PGC-1α, and PGC-1α is itself an ERR coactivator – there’s a feed-forward loop that exercise biology researchers have known about for years but couldn’t pharmacologically access. SLU-PP-332, from the Burris lab at Saint Louis University, is the first credible pan-isoform agonist with low-nanomolar potency across all three ERRs. That’s the differentiation story: hitting the whole family matters because ERRα and ERRγ have partially distinct target gene sets in skeletal muscle and cardiac tissue, and a selective agonist would miss that coverage.

The rodent data is striking. The headline finding – roughly doubled treadmill running time in sedentary mice at 50 mg/kg subcutaneous daily over several weeks – is the kind of number that gets attention, and the supporting gene expression data holds up: elevated COX complex subunit transcripts, mitochondrial content markers up, oxidative fiber type markers elevated. High-fat diet cohorts showed reduced fat accumulation. Older animals showed some protection against age-related muscle changes. These are coherent results that track the mechanism rather than obvious off-target pharmacology.

What we dont like: this is still almost entirely Burris lab work. Replication from independent groups is thin, and no clinical data exists. Clinical development has been announced through partner companies, but Phase 1 readouts arent public. The translational question is genuinely open – exercise transcriptional programs are well-conserved across mammals, but human pharmacokinetics, chronic tolerance windows, and the ERR family’s relationship with estrogen-sensitive tissues in long-term studies are uncharacterized. The carcinogenicity concern that ended GW501516 probably doesn’t apply mechanistically here, but nobody can say that with confidence yet.

As a bench tool, SLU-PP-332 earns its place. If you’re studying mitochondrial biology, skeletal muscle metabolism, or the molecular basis of exercise adaptation, this compound lets you pharmacologically interrogate the ERR/PGC-1α axis in ways that simply weren’t accessible before. The ERR field has been constrained for years by a lack of selective, potent agonists. That gap in the tool kit was real, and this fills it credibly. We think it warrants serious bench attention – with the appropriate skepticism a single-lab preclinical profile deserves and the understanding that the human story hasn’t started yet.

Novelty: 78
Mechanism promise: 78
In-category differentiation: 70
Evidence quality: 35
Translational signal: 28
Research bench value: 65

Rationale SLU-PP-332 occupies a genuinely novel mechanistic niche as a pan-isoform ERR agonist targeting the transcriptional master regulators of exercise adaptation; novelty and mechanism scores are high, but evidence quality and translational signal are constrained by single-lab preclinical origin and an absence of clinical data.

Pan-ERR (estrogen-related receptor) agonist exercise mimetic

A small-molecule pan-agonist of the three estrogen-related receptor isoforms (ERRα, ERRβ, ERRγ), studied as an exercise mimetic for activation of mitochondrial biogenesis and oxidative metabolism.

Abstract

SLU-PP-332 (CAS 2226909-79-9; molecular formula C25H26N2O5S; molecular weight 466.55) is a small-molecule pan-agonist of the estrogen-related receptor (ERR) family of orphan nuclear receptors developed at the Saint Louis University School of Medicine by Thomas Burris and colleagues. The ERR family comprises three isoforms (ERRalpha, ERRbeta, ERRgamma) that share substantial sequence homology with the estrogen receptor but bind distinct ligands and target distinct gene programs; the principal ERR-regulated gene programs include mitochondrial biogenesis, fatty acid oxidation, oxidative phosphorylation, and skeletal muscle oxidative fiber phenotype. ERR activity is induced by exercise and is one of the principal transcriptional drivers of the exercise-induced metabolic adaptation phenotype, alongside PGC-1alpha (which is itself an ERR coactivator). SLU-PP-332 was characterized as an inverse partial agonist or full agonist depending on the assay, with similar potency at all three ERR isoforms (EC50 in the low-nanomolar to mid-nanomolar range). Reported in vivo effects in rodent models include increased exercise endurance (treadmill running time approximately doubled in mice receiving the compound at 50 mg/kg subcutaneous daily for several weeks without exercise training), elevation of mitochondrial gene expression in skeletal muscle, reduction of body fat mass on high-fat diet, and protection against age-related muscle dysfunction. The pharmacological profile has motivated interest in the compound as an exercise mimetic for metabolic and aging indications. The compound is research-grade and not approved by any regulatory authority; clinical development through partner companies has been announced but no Phase 1 readouts have been published as of the most recent monograph revision. Reconstitution requires DMSO or co-solvent owing to limited aqueous solubility; storage of solid material at refrigerated or frozen conditions.

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Tag: KDC-MN-1344

SLU-PP-332

Abstract

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