Ac-SDKP vs Dalargin

Inhibits hematopoietic stem cell entry into S-phase. Blocks TGF-β1-mediated fibroblast activation, reducing collagen deposition. Promotes angiogenesis via VEGF upregulation. Regulated in vivo by ACE enzyme.

Ac-SDKP (N-acetyl-seryl-aspartyl-lysyl-proline) is an endogenous tetrapeptide generated from the N-terminus of thymosin beta-4 by the enzyme prolyl oligopeptidase, with further regulation by angiotensin-converting enzyme (ACE), and is characterized by roles in hematopoietic progenitor regulation and anti-fibrotic signaling in renal, cardiac, and vascular tissue. Ac-SDKP inhibits collagen synthesis and fibroblast proliferation, reduces TGF-beta-1-mediated fibrotic signaling, and promotes anti-inflammatory macrophage polarization in preclinical models, suggesting a role in tissue homeostasis downstream of the thymosin beta-4 pathway. Preclinical studies in rodent models of renal fibrosis and systemic lupus erythematosus — predominantly from the NIH-funded Rhaleb and Carretero laboratory at Henry Ford Health — have demonstrated that exogenous Ac-SDKP reduces collagen deposition and inflammatory infiltrate; no human clinical trials have been completed or indexed in PubMed. Ac-SDKP has no FDA approval and no approved indication in any jurisdiction; it is studied as a research compound with a plausible anti-fibrotic mechanism and consistent preclinical evidence, but extrapolation of rodent findings to human therapeutic outcomes has not been validated by any clinical investigation.

Binds delta and mu opioid receptors with peripheral preference due to limited CNS penetration. Reduces gastric acid secretion, promotes mucosal blood flow, and inhibits ulcer formation via prostaglandin-mediated pathways.

Dalargin (D-Ala2-Leu5-Arg6-enkephalin) is a synthetic hexapeptide opioid receptor agonist developed in the Soviet Union as a stable enkephalin analog, designed with D-amino acid substitution to resist enzymatic degradation, and investigated for gastroprotective and analgesic properties in animal models and limited Russian clinical use. Dalargin binds mu and delta opioid receptors and is proposed to exert gastroprotective effects through opioid receptor-mediated suppression of gastric acid secretion, stimulation of mucosal prostaglandin synthesis, and promotion of epithelial repair, with additional central analgesic activity demonstrated in preclinical studies. Published evidence in Western PubMed-indexed journals is limited to animal studies demonstrating gastroprotective activity against NSAID-induced mucosal damage; the compound has been used in Russian clinical practice for peptic ulcer disease, but no randomized controlled trials meeting current methodological standards have been published in English-language indexed journals. Dalargin has no FDA approval and no regulatory approval in any Western jurisdiction; it is an obscure research compound whose evidence base is largely confined to Soviet-era and Russian-language literature, and its safety and efficacy profile in humans has not been validated by independent clinical investigation.