An engineered human follistatin variant: insights into the pharmacokinetic and pharmocodynamic relationships of a novel molecule with broad therapeutic potential.
Datta-Mannan. Amita A; Yaden. Benjamin B; Krishnan. Venkatesh V; Jones. Bryan E BE; Croy. Johnny E JE
Key Findings
- Native follistatin‑315 has a very short half‑life and low systemic exposure, making it unsuitable as a simple injectable drug.
- Fusing follistatin‑315 to an IgG1 Fc fragment and removing its heparan‑sulfate binding increased its terminal half‑life ~100‑fold and exposure ~1,600‑fold.
- The engineered variant produced a clear, dose‑dependent muscle‑preserving effect when administered subcutaneously once weekly in mouse models of muscle atrophy.
Practical Outcomes
- For now, there’s no ready‑to‑use protocol for humans—these results are limited to mice and rely on a specially engineered protein. The study suggests that plain follistatin supplements are unlikely to be effective for muscle growth because they disappear quickly from the bloodstream. Future therapeutics may need similar Fc‑fusion designs to achieve meaningful benefits, so biohackers should watch for clinical trials of engineered follistatin rather than trying the native protein themselves.
Summary
Scientists made a new version of the protein follistatin by attaching it to an antibody fragment and removing a part that sticks to sugars. This engineered molecule stays in the body much longer (about 100‑times longer) and reaches much higher levels (about 1,600‑times higher) than the natural form. In mice, giving this version under the skin once a week helped prevent muscle loss, something the natural protein couldn’t do when given the same way.
Abstract
Human follistatin is a regulatory glycoprotein with widespread biologic functions, including antiinflammatory activities, wound-healing properties, and muscle-stimulating effects. The role of follistatin in a wide range of biologic activities shows promise for potential clinical application, which has prompted considerable interest in the investigation of the protein as a potential disease-modifying agent. In spite of this potential, the development of follistatin as a broad use biotherapeutic has been severely hindered by a poor understanding and characterization of its pharmacokinetic/pharmacodynamic (PK/PD) relationships. Therefore, to better define these relationships, we performed in-depth analyses of the PK/PD relationships of native follistatin-315 (FST315). Our data indicate that the intrinsic PK/PD properties of native FST315 are poorly suited for acting as a parentally administered biotherapeutic with broad systemic effects. Here, we leveraged protein engineering to modify the PK characteristics of the native molecule by fusing FST315 to a murine IgG(1) Fc and removing the intrinsic heparan sulfate-binding activity of follistatin. The engineered variant molecule had ~100- and ~1600-fold improvements in terminal half-life and exposure, respectively. In contrast to the native FST315, the variant showed a robust, dose-dependent pharmacological effect when administered subcutaneously on a weekly basis in mouse models of muscle atrophy and degeneration. These studies highlight the underappreciated and critical relationship between optimizing multiple physical and chemical properties of follistatin on its overall PK/PD profile. Moreover, our findings provide the first documented strategy toward the development of a follistatin therapeutic with potential use in patients affected with skeletal muscle diseases.
Study Information
pubmed
2012
2012-12-17T00:00:00.000Z
10.1124/jpet.112.201491
31
40