reviewed april 2026|next review october 2026|88 physicians psi has verified|49054 published studies
Ac-SDKP
Ac-SDKP (N-acetyl-seryl-aspartyl-lysyl-proline) is the N-terminal tetrapeptide released from thymosin beta-4 cleavage, with its own distinct anti-fibrotic research identity across cardiac, renal, and pulmonary fibrosis, and levels raised as an unintended consequence of ACE inhibitor therapy.
Evidence landscape: 49054 published studies
49,054 published items (broad ACE/fibrosis query). 26 human studies and 133 animal studies.
- 26 Human
- 133 Animal
- 41 Reviews
- 48854 Other research
Not FDA-approved as a standalone therapeutic. Ac-SDKP is a naturally occurring (the body's own) tetrapeptide whose levels are incidentally raised by FDA-approved ACE inhibitor medications. No dedicated clinical development program exists for Ac-SDKP itself.
Not available as a therapeutic product. Research-grade material available for laboratory use. Ac-SDKP levels are raised endogenously by ACE inhibitor therapy, which is widely prescribed for hypertension.
Ac-SDKP is the N-terminal fragment of thymosin beta-4 (parent molecule of TB-500). It is released by prolyl oligopeptidase and degraded by ACE. This creates a direct mechanistic link between ACE inhibitor therapy and anti-fibrotic biology.
PSI Assessment
Three biological stories converge in a single tetrapeptide. First, prolyl oligopeptidase cleaves thymosin beta-4 to release Ac-SDKP. Second, Ac-SDKP inhibits collagen deposition and fibroblast proliferation across cardiac, renal, and pulmonary tissue. Third, ACE (angiotensin-converting enzyme) is the primary enzyme that degrades Ac-SDKP, meaning that ACE inhibitors taken by millions for hypertension raise Ac-SDKP levels as an unintended consequence. This may explain part of why ACE inhibitors reduce organ fibrosis beyond simple blood pressure reduction. The anti-fibrotic mechanism is documented across over 200 focused studies and replicated by multiple independent research groups. No controlled human interventional trials of exogenous Ac-SDKP have been conducted.
Released from thymosin beta-4 cleavage. ACE inhibitors raise Ac-SDKP levels as an unintended consequence. May explain part of why ACE inhibitors reduce organ fibrosis.
The mechanism connects three biology stories. First, prolyl oligopeptidase cleaves thymosin beta-4 to release Ac-SDKP in vivo. Second, Ac-SDKP inhibits collagen deposition and fibroblast proliferation in cardiac, renal, and pulmonary tissue, reducing organ fibrosis. Third, ACE (angiotensin-converting enzyme) is the primary enzyme that degrades Ac-SDKP, which means ACE inhibitors (drugs taken by millions for hypertension) raise Ac-SDKP levels as an unintended consequence, potentially contributing to the anti-fibrotic benefits observed beyond blood pressure reduction.
What the evidence supports
Ac-SDKP inhibits collagen deposition and fibroblast proliferation across cardiac, renal, and pulmonary tissue in animal models, replicated by multiple independent groups. ACE is the primary degradative enzyme, establishing the mechanistic link between ACE inhibitor therapy and raised Ac-SDKP levels. The anti-fibrotic mechanism is documented across over 200 focused studies.
What is not yet established
Whether exogenous Ac-SDKP administration produces clinically meaningful anti-fibrotic effects in humans beyond what ACE inhibitors achieve. Controlled human interventional trials are absent. Whether the anti-fibrotic benefits of ACE inhibitors are substantially mediated through Ac-SDKP versus other mechanisms. Optimal dosing and delivery for therapeutic use.
Research Evidence
The findings below cover Ac-SDKP's anti-fibrotic mechanism, the ACE inhibitor connection, and the evidence base across organ systems.
Evidence by condition
Evidence dimensions available for each condition Ac-SDKP has been studied for.
| Condition | Mechanism | Animal evidence | Human evidence | Replication |
|---|---|---|---|---|
| Cardiac Fibrosis | ||||
| Renal Fibrosis | ||||
| Pulmonary Fibrosis | ||||
| Stem Cell Regulation |
Ac-SDKP inhibits collagen deposition and fibroblast proliferation in cardiac, renal, and pulmonary tissue. ACE inhibitors raise Ac-SDKP levels approximately 5-fold, establishing the mechanistic link between ACE inhibitor therapy and anti-fibrotic biology.
The anti-fibrotic effects have been replicated by multiple independent research groups across organ systems. Whether this mechanism explains a clinically meaningful portion of ACE inhibitor organ protection is debated.
26 Human|133 Animal|41 Reviews
View all 49054 indexed studiesHow Ac-SDKP Works
Ac-SDKP (N-acetyl-seryl-aspartyl-lysyl-proline) is a naturally occurring (the body's own) tetrapeptide. It is released from thymosin beta-4 by prolyl oligopeptidase and degraded by ACE. It inhibits TGF-beta/Smad signaling, reducing collagen synthesis by fibroblasts across multiple organ systems.
Tells scar-producing cells to slow down. ACE inhibitors raise levels as an unintended consequence.
For a more detailed view of the biology, here is what researchers have observed at the molecular level.
Inhibits collagen synthesis by blocking Smad2 in TGF-beta signaling. Natural substrate of ACE. Released from thymosin beta-4 by prolyl oligopeptidase.
What is Ac-SDKP being studied for?
Researchers are studying Ac-SDKP across several health conditions. Each condition below is labeled with the strength of evidence that exists for that specific use, not for Ac-SDKP overall. This means a compound can have human studies for one condition but only animal data for another.
Cardiac Fibrosis
·Human TrialsAc-SDKP reduces collagen deposition in cardiac fibrosis models. ACE inhibitor therapy raises Ac-SDKP levels, and this elevation correlates with reduced cardiac fibrosis in human observational data.
Limitations: No controlled human trials of exogenous Ac-SDKP for cardiac fibrosis. The human evidence is observational (from ACE inhibitor studies), not interventional.
Renal Fibrosis
·Animal StudiesAnimal studies demonstrate renoprotective effects against diabetic nephropathy and other forms of kidney fibrosis. The mechanism involves inhibition of TGF-beta/Smad signaling in renal fibroblasts.
Limitations: No human interventional trials. Whether Ac-SDKP mediates the renoprotective effects of ACE inhibitors is suggested but not confirmed.
Pulmonary Fibrosis
·Animal StudiesAnimal models show reduced pulmonary fibrosis with Ac-SDKP administration. The anti-fibrotic mechanism extends across lung tissue similar to cardiac and renal effects.
Limitations: Animal study evidence only for the pulmonary indication. No clinical investigation.
Stem Cell Regulation
·Animal StudiesAc-SDKP promotes hematopoietic stem cell quiescence, potentially protecting bone marrow during chemotherapy.
Limitations: The stem cell regulation effects are characterized in animal models. No clinical investigation of this application.
Safety and Regulatory Status
FDA Status: Not FDA-approved as a standalone therapeutic. Ac-SDKP levels are raised by FDA-approved ACE inhibitor medications as an unintended pharmacological consequence.
Availability: Not available as a therapeutic product. Research-grade material only. Naturally occurring (the body's own) levels are raised by ACE inhibitor therapy.
Class context: Ac-SDKP is a naturally occurring (the body's own) tetrapeptide. It is the N-terminal fragment of thymosin beta-4 and a natural substrate of ACE. No safety concerns from normal physiological activity or from the elevated levels produced by ACE inhibitor therapy.
Ac-SDKP is a naturally occurring (the body's own) tetrapeptide. Elevated levels during ACE inhibitor therapy have been observed for decades with no associated safety signal. Exogenous administration as a standalone therapeutic is investigational.
Peptide Structure
Technical molecular data for researchers and clinicians.
Questions and Comparisons
Questions the evidence raises for a Ac-SDKP discussion.
Comparison and Related Research
Ac-SDKP connects the thymosin beta-4 biology to cardiovascular pharmacology. The comparisons below clarify these relationships.
Related compounds
Frequently Asked Questions
References
Each citation links to the original study on PubMed, the U.S. National Library of Medicine database.
- 1.A study demonstrating the anti-fibrotic properties of Ac-SDKP in experimental hypertension models. The research established that ACE inhibitors raise endogenous Ac-SDKP levels by blocking its degradation, and that this elevation contributes to the anti-fibrotic benefits observed with ACE inhibitor therapy.Rasoul S et al., 2004 in J Hypertens. View on PubMed
- 2.A landmark paper proposing that a significant portion of ACE inhibitor benefit comes from preventing the breakdown of Ac-SDKP. The study demonstrated that ACE is the primary enzyme responsible for Ac-SDKP degradation in vivo, connecting one of the most widely prescribed drug classes to this endogenous anti-fibrotic peptide.Peng H et al., 2005 in Circulation. View on PubMed
- 3.Research showing that reducing endogenous Ac-SDKP levels through inhibition of prolyl oligopeptidase (the enzyme that releases Ac-SDKP from thymosin beta-4) promoted organ fibrosis in the kidneys and heart. The study reinforced the concept that Ac-SDKP serves as a natural brake on fibrotic processes.Cavasin MA et al., 2007 in Hypertension. View on PubMed
- 4.A comprehensive review of Ac-SDKP covering its synthesis from thymosin beta-4, its degradation by ACE, and the cumulative evidence for therapeutic potential in hypertension, cardiac fibrosis, and renal disease. The paper integrated preclinical and clinical pharmacological data on this tetrapeptide.Kumar N et al., 2018 in Pharmacol Res. View on PubMed
- 5.A mechanistic study identifying anti-inflammatory pathways activated by Ac-SDKP in the context of hypertension-induced organ damage. The research documented reductions in macrophage infiltration and inflammatory cytokine expression, expanding the understanding of Ac-SDKP beyond its anti-fibrotic role.Sharma U et al., 2008 in Am J Physiol Heart Circ Physiol. View on PubMed
Medical Disclaimer
This content is for educational and informational purposes only and does not constitute medical advice. The information presented reflects published research as indexed by PSI and should not be used to make treatment decisions. Always consult a qualified healthcare provider before starting, stopping, or modifying any treatment.