Tissue repair

ARA-290, also called cibinetide, is an 11-amino-acid peptide carved from the three-dimensional structure of erythropoietin - specifically from the face of the molecule that activates tissue repair rather than the face that makes red blood cells. That separation is the whole idea: erythropoietin protects injured tissue in animal models, but raising hematocrit in patients who do not need it causes thrombosis and strokes. ARA-290 has been through several small randomized trials in small fiber neuropathy, where it improved symptoms and increased corneal nerve fiber density, and one in type 2 diabetes where it improved both neuropathic symptoms and HbA1c. The trials are genuinely positive and genuinely small - a few dozen patients each, mostly from one group - and nothing has progressed to a confirmatory phase 3.

BPC-157 is a synthetic 15-amino-acid peptide, a fragment of a protein found in human gastric juice. Clinicians and athletes increasingly use it for musculoskeletal injuries. In rats it consistently speeds healing of many tissues. Human data amount to three small, uncontrolled pilot reports, all by the same first author. It is not approved by the FDA and is banned in professional sport.

Cartalax is the tripeptide Ala-Glu-Asp (AED), one of the short "peptide bioregulators" developed by Vladimir Khavinson's group in St Petersburg and promoted for cartilage. In cell cultures it switched on cartilage-forming genes in aging human stem cells and lowered markers of aging in chondrocytes. There are no published human trials, and almost every study comes from the developers' own group.

GHK-Cu is the copper complex of GHK (glycyl-histidyl-lysine), a tripeptide found in human plasma, saliva and urine whose levels fall with age. In lab studies it raises collagen and elastin production and supports skin cells, and it is a common ingredient in anti-wrinkle products. The best human evidence is one 1994 trial in which a GHK-Cu gel sped the healing of diabetic foot ulcers. The cosmetic studies are described mainly in reviews by the peptide's discoverer, and an independent review found few published clinical studies.

LL-37 is the only cathelicidin humans make - a 37-residue antimicrobial peptide released from the precursor hCAP18 in skin, neutrophils and epithelia, which kills bacteria, recruits immune cells and drives re-epithelialization. It has been through three randomized trials in chronic wounds, and the results run in exactly the direction that should make anyone cautious. A 2014 trial in hard-to-heal venous leg ulcers found the peptide safe and reported a marked effect, with mean ulcer area down 68% at the lower concentration. A 2021 multicenter trial in 148 patients then found no significant improvement in healing across the whole cohort, with benefit only in a post-hoc subgroup with large ulcers. A separate randomized trial in diabetic foot ulcers reported benefit.

TB-500 is a product built on Ac-LKKTETQ, a synthetic, acetylated copy of the seven-amino-acid actin-binding region of thymosin beta-4. It began as a veterinary preparation and is marketed for wound healing and tissue repair. It has never been tested for efficacy in humans. In a lab study, the intact peptide did not speed wound closure; one of its breakdown products did.

Thymosin beta-4 (Tβ4) is a 43-amino-acid protein found in almost every cell, where it is the main store of unused actin, the building block of the cell skeleton. Animal studies report faster skin-wound healing, stronger repaired ligaments and improved recovery after heart or brain injury. Small human trials of topical treatment for venous ulcers and eye disease have encouraging but inconclusive findings. It is not approved as a medicine.