TB-4 Fragment (Thymosin Beta-4 17-23) is a short synthetic peptide derived from the thymosin beta-4 protein, investigated for wound healing, skin repair, and hair follicle regeneration. Thymosin beta-4 facilitates actin sequestration, keratinocyte migration, and stem cell recruitment to sites of tissue injury; the 17-23 fragment retains portions of these bioactive properties. Peer-reviewed studies demonstrate that thymosin beta-4 promotes hair follicle stem cell activation and dermal tissue regeneration in preclinical models, providing a mechanistic basis for skin-related applications. TB-4 Fragment is an investigational peptide with limited human clinical data and is not approved by the FDA for any therapeutic use. TB4-Frag vs full-length thymosin beta-4 TB-4 Fragment (residues 17–23 of thymosin beta-4, sequence: Leu-Lys-Lys-Thr-Glu-Thr-Gln) is a distinct, smaller molecule compared to full-length thymosin beta-4 (43 amino acids). The fragment retains the actin-binding motif that drives keratinocyte migration and stem cell recruitment — mechanisms central to the wound healing and hair follicle regeneration research attributed to TB4 — but lacks the full protein's Ac-SDKP-generating and anti-fibrotic properties. The lower molecular weight of the fragment (approximately 870 Da vs ~4,900 Da for full Tb4) is proposed to improve transdermal penetration for topical applications, making TB4-Frag relevant to cosmetic skin and scalp formulations where injectable administration is not used. In the research peptide market, TB4-Frag is positioned as a topical active for skin repair and hair density contexts; full-length thymosin beta-4 (sold as TB-500) is used for systemic/injectable recovery and tissue repair applications. The two should not be conflated — they have different sequences, molecular weights, and proposed application contexts despite sharing a mechanistic origin.