French drugmaker Servier has presented late-stage data on Protelos, which shows that the drug reduced structural progression of osteoarthritis in knee joints by one-third.

The Phase III results, unveiled at the European Congress on Osteoporosis and Osteoarthritis in Bordeaux, come from the first study ever to have demonstrated a disease-modifying effect in OA. Furthermore, investigators showed that Protelos (strontium ranelate), currently licensed for osteoporosis, delivered beneficial effects on pain, function, and mobility.

Cyrus Cooper, of the universities of Southampton and Oxford and the lead investigator on the trial, said that "after years of labouring to manage patients with blunt tools we finally have something that allows us to alter the natural history of the disease". Until now, the only treatment for OA, a condition estimated to affect one in six people, has been life-style changes and symptomatic relief with analgesics.

In the Phase III study, 1,683 patients with knee osteoarthritis (mean age 62.3 years) were randomised to receive Protelos 2g/day, 1g/day or placebo. The primary endpoint was the measurement of narrowing of the medial-tibio femoral compartment of the target joint.

At three years, results show that in comparison with placebo the space between the joints was 33% wider (less narrow) for patients receiving the 1g dose and 23% wider for those on 2g. Both doses significantly decreased the number of patients reaching >0.5mm loss of joint space, a threshold  known to place people at a fivefold increase in the risk of undergoing joint replacement surgery over the next five years. For the 1g dose, the risk of reaching this threshold was reduced by 34%, and by 44% for the 2g dose.

Jean-Yves Reginster from the University of Liege, who presented the study in the scientific session, noted that “such data suggests that strontium ranelate could reduce the number of patients requiring knee surgery". For every three years of treatment, he added, the equivalent of a year of joint space would be saved.

Furthermore, Protelos 2g significantly reduced the WOMAC score (a global score taking into consideration OA pain, function and mobility) in comparison with placebo, while the 1g dose did not produce a statistically significant effect. “Clearly, the 2g dose is needed to obtain the beneficial effects on pain and stiffness,” added Prof Reginster.

Protelos costs less than £1 a day

The study has caused much excitement, not least because Protelos costs less than £1 a day. Prof Cooper added that"for the first time, we have a treatment that can slow the development of this debilitating disease and could reduce or even eliminate the need for expensive and painful joint replacement surgery".

Servier noted that in 2010, over 140,000 hip and knee replacements were carried out in the UK, at a cost of over £1 billion to the National Health Service.