The family of transforming growth factor - β (TGF-β) proteins are master regulators of tissue homeostasis. Consequently, their deregulated activities are associated with a multitude of human disorders including, infertility, cancer, obesity, tissue degeneration, and fibrosis. Correcting TGF-β activity is an attractive approach to restore tissue homeostasis, but is limited by the poor in vivo stability of TGF-b proteins. The active proteins are derived from large Pro-TGF-β forms that undergo proteolytic maturation, yielding a pro:mature non-covalent complex, with pro and mature (active) domains. Prodomains are removed during commercial preparation, leaving only mature active ligand. These preparations, having half-lives of minutes, are unsuitable for therapeutic treatment in humans. The pro:mature non-covalent complex, in which the mature active ligand is shielded by its prodomains, is predicted have greater in vivo stability than the mature ligands. In this study, we examined whether the prodomain could reduce the clearance rate and increase activity in vivo for a well characterised member of the TGF-β family, activin A. To address this, we aimed to generate a pro:mature complex. To favour production of the Pro-activin complex, the native cleavage site was enhanced by site-directed mutagenesis. This modification improved the processing of activin precursor. Pro-activin complexes were isolated from stable HEK-293E cell lines by immunoaffinity using an antibody targeted to the prodomain. Importantly, the purified Pro-activin complex had comparable in vitro bioactivity to the commercially available mature preparations, supporting that the prodomain does not perturb activin bioactivity. In vivo work determined that the half-life of activin was improved two-fold, compared to the mature alone, and biological activity was also improved. Ongoing studies aim to further improve the half-life of activin A. The outcomes of this work will provide a blueprint for generating long-acting TGF-β ligands, which would benefit the treatment of human conditions associated with altered TGF-β signalling.