Analog of human relaxin-2 built as a single chain, activating relaxin family peptide receptor 1 (RXFP1) selectively. Where native relaxin-2 depends on two chains, A and B, held together by disulfide bonds in a complex structure, B7-33 achieves the same RXFP1 activation from one simple chain — synthesis is far easier and far cheaper for it. Anti-fibrotic, vasodilatory, and cardioprotective properties are potent in preclinical research, which puts B7-33 forward as a promising therapeutic candidate for heart failure, fibrotic diseases, and vascular dysfunction.