In the fight to find a cure for osteoarthritis and acute cartilage damage, Merck is now focusing on a human growth factor called “fibroblast growth factor 18” (FGF-18). This biologic stimulates the formation of new cartilage cells. Klaus Flechsenhar is responsible for clinical development of FGF-18 at Merck Serono. As he explains: “This growth factor ensures the replenishment of cartilage cells, so that new cartilage matrix can be formed. This gives the body a chance to replace cartilage damaged as a result of osteoarthritis or acute injury with genuine hyaline cartilage, rather than inferior repair cartilage. This in turn can reverse the imbalance between cartilage depletion and cartilage formation that is typical of osteoarthritis. These are still the early days in the clinical development of FGF-18, however, and it will be a few years before we can safely say whether or not this biologic can live up to our expectations.”

Although FGF-18 may well provide a therapy for all forms of osteoarthritis and acute cartilage injuries, Merck is currently concentrating on damage to the knee joint. It is here that the need for treatment is most acute. The therapy involves injecting FGF-18 into the knee, with a treatment cycle consisting of three injections in all, administered at intervals of one per week. A maximum of two cycles have been tested so far.

To date, Merck has produced three clinical studies: two on osteoarthritis in the knee joint, and one on acute cartilage damage, also in the knee. In one of the osteoarthritis studies, early stages of the disease were treated; in the other, late ones. These clinical trials were Phase I and Phase II trials whose purpose was to verify the safety of FGF-18 and gain an initial impression of its efficacy. By the beginning of the year, only patients for the trial on acute cartilage damage were still being recruited. In the case of the two other trials, this phase had already been completed.

Says Flechsenhar: “We haven’t yet fully evaluated the clinical trials, nor have we published the results, so we still can’t say anything concerning the efficacy of FGF-18. But what we can say with certainty is that there haven’t been any tolerability issues in any of the three trials to date. We’ll be able to say more about the treatment’s effectiveness at a later date.”