B7-33 is a synthetic 26-amino acid peptide with the sequence VIKLSGRELVRAQIAISGMSTWSKRSL or Val-Ile-Lys-Leu-Ser-Gly-Arg-Glu-Leu-Val-Arg-Ala-Gln-Ile-Ala-Ile-Ser-Gly-Met-Ser-Thr-Trp-Ser-Lys-Arg-Ser-Leu. It is an N-terminal truncated, C-terminal extended fragment from the B chain of human relaxin-2, and has similar anti-fibrotic effects to the full length peptide. It has been researched for conditions where excess fibrosis plays a role, such as cardiac fibrosis and pulmonary fibrosis.