1457 patients were randomized to determine the effect of cindunistat hydrochloride maleate (inducible nitric oxide synthase inhibitor) on slowing the progression of knee osteoarthritis. Patients were allocated to receive 50mg cindunistat daily, 200mg cindunistat daily, or a placebo for 96 weeks, and were evaluated on the basis of joint space narrowing and clinical outcome. The results indicated that neither 50mg nor 200mg/day cindunistat regimen significantly reduced the rate of joint space narrowing compared to placebo, and there were no differences found between the two treatment groups.