The trial will assess the efficacy of Ampion in reducing pain as a single intra-articular injection to the knee in 4ml and 10m doses, as compared to placebo at twelve weeks.
The study, part of the US development programme for Ampion, has exceeded its target of enrolling 320 patients.
Ampio chairman and CEO Michael Macaluso said; "While we set very stringent site criteria to optimise the rate of enrollment, I believe this could indicate the severe degree current therapeutics are not meeting the needs of osteoarthritis sufferers."
The company expects to announce its twelve-week primary endpoint data in the third quarter of 2013.
The study was designed as a run-in to a Phase III trial, which will be commenced by the company upon the determination of the optimal dose.
Ampion is a non-steroidal anti-inflammatory biologic with the potential to be used in a range of inflammatory conditions and autoimmune diseases.