Tetrapeptide-21 — Safety, Research, Risks & Legal Status

Not medical advice. Tetrapeptide-21 is discussed here for informational and harm-reduction purposes only. We do not endorse use, and any dosing context is informational, not a protocol.

Also known as	GEKG peptide; TEGO Pep 4-17; TEGO Pep 4-17 MB; H-Gly-Glu-Lys-Gly-OH; CAS 960608-17-7
Category	Peptide
Sequence	Gly-Glu-Lys-Gly (GEKG)
CAS Number	960608-17-7
Class	Synthetic matrikine (ECM-derived signaling peptide)
Primary commercial form	TEGO Pep 4-17 MB (Evonik) - aqueous, preservative-free
Key pathway	MAPK / AP-1 transcription factor activation in dermal fibroblasts
Clinical trial status	No registered trials on ClinicalTrials.gov; cosmetic panel studies only
US legal status	Permitted cosmetic ingredient in the United States under FDA cosmetic regulations. Not an FDA-approved drug and no IND application has been identified. Not listed as a restricted or prohibited substance under California Proposition 65. Sold openly as a skincare active/cosmeceutical ingredient; not scheduled or controlled. Not approved for therapeutic pharmaceutical use in any jurisdiction.

What is Tetrapeptide-21?

Tetrapeptide-21 (GEKG) is a synthetic matrikine - a short peptide designed to mimic biologically active fragments generated by extracellular matrix (ECM) degradation. Its four-amino-acid sequence (Gly-Glu-Lys-Gly) is found naturally in collagen types I through V, collagen IV, elastin, and other ECM proteins. It is used as an active ingredient in topical skincare formulations intended to support dermal collagen and hyaluronic acid synthesis. All current positioning and evidence is cosmetic, not pharmaceutical.

How it works

Tetrapeptide-21 binds to fibroblast cell-surface receptors and activates the MAPK signaling pathway and AP-1 transcription factor, stimulating upregulation of procollagen type I mRNA, hyaluronic acid synthase 1 (HAS1), and fibronectin gene expression in dermal fibroblasts. This matrikine mechanism - where ECM-derived peptides signal cells to rebuild matrix - is well established in cell biology; the GEKG sequence was identified via bioinformatic prediction of bioactive ECM breakdown products rather than derived from empirical drug screening.

Background & history

Developed computationally by Evonik (then operating under the Goldschmidt/TEGO brand) as part of a program to identify bioactive ECM-derived peptide sequences. The foundational publication by Farwick et al. (2011) in Experimental Dermatology established in vitro and limited in vivo evidence. Commercialized as TEGO Pep 4-17 and TEGO Pep 4-17 MB. Has since been widely adopted as a cosmetic active by multiple peptide contract manufacturers (Creative Peptides, Spec-Chem, MedChemExpress, others) and incorporated into numerous anti-aging topical formulations. No transition to pharmaceutical development has been documented.

What the research says

Evidence base is limited to in vitro and small-panel cosmetic studies; no registered clinical trials appear on ClinicalTrials.gov as of the knowledge cutoff. In vitro evidence (human dermal fibroblasts, foreskin fibroblasts, dermal papilla cells) shows approximately 2-2.5 fold increases in collagen production relative to controls, with performance described as comparable to the reference matrikine Matrixyl in some assays. The Farwick et al. 2011 study provides the primary peer-reviewed mechanistic and limited clinical proof-of-concept data, including a small panel study showing skin roughness reduction. A 2024 study examined GEKG in combination with injectable platelet-rich fibrin, finding synergistic effects on fibroblast viability and ECM gene expression. A separate 2024 study explored elastin-derived hydrogel delivery systems for sustained topical delivery of Tetrapeptide-21. Overall, the mechanistic story is well-supported in cell culture; clinical efficacy evidence from rigorous controlled human trials is essentially absent.

Reported effects

Upregulation of procollagen type I gene expression in human dermal fibroblasts (in vitro)
Increased hyaluronic acid synthase 1 (HAS1) expression in fibroblasts (in vitro)
Increased fibronectin production in fibroblast models (in vitro)
Skin surface roughness reduction in small cosmetic panel studies (limited, uncontrolled data)
Synergistic ECM gene upregulation when combined with platelet-rich fibrin in cell culture (single 2024 study)
No established systemic or pharmacological effects - all evidence is topical/local

Dosing & administration (informational)

Published cosmetic formulation literature references use concentrations in the range of 0.001% to 0.1% active peptide in topical formulations, consistent with other synthetic matrikines in skincare. These figures are drawn from supplier technical documentation and the Farwick et al. (2011) study and are provided here as informational literature context only - they do not constitute a dosing protocol. There are no established pharmaceutical dosing parameters. Anyone considering use should consult a licensed clinician or dermatologist.

This is general research/context information, not medical advice or a recommended protocol.

Safety & side effects

No adverse effects reported in cosmetic use literature
Not listed on EWG Skin Deep Restricted or Unacceptable lists
No identified skin or eye irritation in available data
Theoretical acute toxicity studies at doses 5,000-fold above cosmetic exposure levels showed no toxicity; subacute/chronic at 100-1,000x showed no reported side effects
No carcinogenic, mutagenic, or developmental toxicity signals identified in available data
California Prop 65 compliance noted by at least one supplier - not known to cause cancer, birth defects, or reproductive harm
No long-term human safety data exists; all safety information is from in vitro, theoretical modeling, or short-term cosmetic use

Drug & supplement interactions

Who should avoid it

No specific contraindications established in available literature
Standard caution applies for any topical peptide in individuals with known hypersensitivity to protein-derived ingredients
Formulation excipients (preservatives, carriers) may present their own sensitization profiles independent of GEKG itself

How it is commonly combined

No clinical stacking data exists. In vitro research has examined GEKG alongside platelet-rich fibrin components, suggesting additive or synergistic ECM gene upregulation in that context. Many commercial formulations combine Tetrapeptide-21 with other matrikines (e.g., palmitoyl pentapeptide-4/Matrixyl, acetyl hexapeptide-3) and antioxidants, though no controlled comparative or combination efficacy data is available.

Legal & regulatory. Permitted cosmetic ingredient in the United States under FDA cosmetic regulations. Not an FDA-approved drug and no IND application has been identified. Not listed as a restricted or prohibited substance under California Proposition 65. Sold openly as a skincare active/cosmeceutical ingredient; not scheduled or controlled. Not approved for therapeutic pharmaceutical use in any jurisdiction.

Quality & harm reduction

C
o
m
m
e
r
c
i
a
l
l
y
a
v
a
i
l
a
b
l
e
a
s
a
c
o
s
m
e
t
i
c
i
n
g
r
e
d
i
e
n
t
f
r
o
m
E
v
o
n
i
k
(
T
E
G
O
P
e
p
4
-
1
7
M
B
,
a
p
r
e
s
e
r
v
a
t
i
v
e
-
f
r
e
e
a
q
u
e
o
u
s
s
o
l
u
t
i
o
n
)
a
n
d
m
u
l
t
i
p
l
e
p
e
p
t
i
d
e
c
o
n
t
r
a
c
t
m
a
n
u
f
a
c
t
u
r
e
r
s
.
P
u
r
i
t
y
a
n
d
s
p
e
c
i
f
i
c
a
t
i
o
n
v
a
r
y
b
y
s
u
p
p
l
i
e
r
;
c
o
s
m
e
t
i
c
-
g
r
a
d
e
m
a
t
e
r
i
a
l
i
s
n
o
t
s
u
b
j
e
c
t
t
o
p
h
a
r
m
a
c
e
u
t
i
c
a
l
c
G
M
P
r
e
q
u
i
r
e
m
e
n
t
s
.
R
e
s
e
a
r
c
h
-
g
r
a
d
e
G
E
K
G
p
e
p
t
i
d
e
i
s
a
v
a
i
l
a
b
l
e
f
r
o
m
s
u
p
p
l
i
e
r
s
s
u
c
h
a
s
M
e
d
C
h
e
m
E
x
p
r
e
s
s
a
n
d
C
r
e
a
t
i
v
e
P
e
p
t
i
d
e
s
f
o
r
i
n
v
i
t
r
o
w
o
r
k
.
N
o
s
t
a
n
d
a
r
d
i
z
e
d
p
o
t
e
n
c
y
o
r
p
u
r
i
t
y
b
e
n
c
h
m
a
r
k
s
a
p
p
l
y
i
n
t
h
e
c
o
s
m
e
t
i
c
c
o
n
t
e
x
t
.

Safer, legal alternative we recommend

Liver Let Live. For liver and metabolic support, our Liver Support formula is a legal supplement option covering a similar goal.

See our recommended pick

Find Tetrapeptide-21 →

Know your numbers before you research

Order your own bloodwork online — hormone, metabolic and inflammation panels, no doctor visit needed. Know your baselines before and during any protocol. Independent bloodwork is the cheapest insurance there is.

Get tested with Ulta Lab Tests →

Frequently asked questions

Is Tetrapeptide-21 a drug or a cosmetic ingredient?

It is a cosmetic ingredient, not a pharmaceutical drug. No IND application or drug development program has been identified. It is sold and regulated as an active skincare cosmeceutical ingredient in the United States and has no approved therapeutic indication.

How strong is the clinical evidence for anti-aging effects?

The mechanistic and in vitro evidence is reasonably well-established - cell culture studies consistently show upregulation of collagen and hyaluronic acid synthase gene expression in human fibroblasts. Clinical evidence is modest: the primary reference is a small panel study in the Farwick et al. 2011 paper showing skin roughness improvement. No large, randomized, placebo-controlled clinical trials are registered or published as of available data.

What is the recommended dose or concentration to use?

This reference does not provide dosing protocols. Published cosmetic literature references concentrations in a low percentage range in topical formulations, but these are informational only. Anyone seeking guidance on use should consult a licensed dermatologist or clinician.

Is it safe for topical use?

Available data suggests a favorable safety profile for cosmetic topical use. No skin irritation, carcinogenicity, or systemic toxicity signals have been identified in the literature. That said, long-term controlled human safety studies do not exist, and all safety information derives from in vitro work, supplier toxicology testing, and post-market cosmetic experience.

How does Tetrapeptide-21 differ from Matrixyl (palmitoyl pentapeptide-4)?

Both are synthetic matrikines that act on dermal fibroblasts to stimulate ECM protein production, and the Farwick 2011 study describes GEKG as performing comparably to Matrixyl in some in vitro assays. Matrixyl has a longer body of published cosmetic research. Neither has robust large-scale randomized clinical trial data supporting efficacy claims.

Is Tetrapeptide-21 available for purchase, and for what use?

Yes, it is commercially available from multiple cosmetic ingredient suppliers (Evonik, Creative Peptides, MedChemExpress, others) for incorporation into topical skincare formulations or for in vitro research. It is not approved or intended for internal or injectable use.

References & further reading

PubMed: Farwick M et al. 'Bioactive tetrapeptide GEKG boosts extracellular matrix formation: in vitro and in vivo molecular and clinical proof' Experimental Dermatology 2011 PMID 21692860
PubMed: 'Elastin-derived peptide hydrogels for sustained dermal delivery of tetrapeptide-21' 2024 PMID 41421628
PubMed: 'Synergistic Effects of Injectable Platelet-Rich Fibrin and Bioactive Peptides on Dermal Fibroblast Viability and Extracellular Matrix Gene Expression' 2024 PMC12388378
PubMed: 'Skin rejuvenation using cosmetic products containing growth factors cytokines and matrikines a review' PMC5108505
ClinicalTrials.gov: tetrapeptide-21 GEKG (search returns no registered trials as of available data)