The therapeutic application of transforming growth factor-β (TGF-β) ligands, despite having potential in numerous human diseases, is currently restricted by their short half-lives. All TGF-β ligands are made as large precursor proteins, with N-terminal prodomains and C-terminal mature domains. During ligand biosynthesis, the prodomains are enzymatically removed but appear to remain non-covalently associated with the mature dimer. The mature ligands mediate receptor contacts, and are solely responsible for activity. Currently, all commercially available forms of TGF-β ligands comprise only mature active dimer. These preparations have half-lives of only minutes and are unsuitable for therapeutic treatment in humans. The pro:mature non-covalent complex, in which the mature active ligand is shielded by its prodomains, it predicted have greater in vivo stability than the mature ligands. To address, we firstly generated the pro:mature activin A complex. To favour the production of pro:mature activin A, we enhanced the native furin cleavage site. This modification increased the processing of the activin A precursor, as evidence by increased levels of mature activin A, and reduction in activin precursor. Pro:mature activin A complexes were successfully isolated from stable HEK-293E cell lines by immunoaffinity using an antibody targeted to the prodomain. Importantly, the purified activin A complex had bioactivity comparable to the commercially available mature preparations, supporting that the presence of the prodomains does not hinder bioactivity. An analysis of the activin-induced SMAD-signalling pathway in LbT2 cells suggested that the activin complex may have an extended signaling capacity in vitro relative to the mature form. These studies reveal a new means to generate bioactive TGF-b ligands, with anticipated improved stability in vitro.