Novel knee osteoarthritis drugs target pain, joint space narrowing

Several early clinical studies have been completed already, noted Yusuf Yazici, MD, chief medical officer of Samumed (San Diego), the California-based company that is developing SMO4690.

SM04690 is a small molecule inhibitor of the Wnt pathway, which is involved in increased bone formation and turnover, he explained. The hypothesis is that by blocking this pathway, the joint can be protected and cartilage could perhaps be regenerated.

Dr. Yazici presented radiographic outcomes at 26 weeks from a 52-week trial that “demonstrated SM04690 treatment maintained or increased medial joint space width compared to placebo.” This is important, as “joint space narrowing is indicative of OA progression and is predictive of knee surgery,” and radiographic progression remains a “gold standard” for assessing potential disease modification in OA, said Dr. Yazici, who is also clinical associate professor and director of the Seligman Center for Advanced Therapeutics at New York University.

In the phase 2 trial he presented, three doses of SM04690 (0.03 mg, 0.07 mg, and 0.23 mg), given as one 2-mL intra-articular injection into a single target knee, were tested and compared against placebo. The target knee was the knee designated as causing the patient the most pain, according to the study investigator.

Radiographs of both knees were taken at the start of treatment, at week 26, and again at week 52, with the change in medial joint space width analyzed. Clinical assessments included changes in WOMAC total, function, and pain subscale scores, and patients’ and physicians’ global assessments.

A total of 455 subjects, mean age 60 years, were randomized into the trial.

Considering all patients, the mean increase in medial joint space width from baseline to 26-week assessment versus placebo was –0.07 mm in the SM04690 0.03-mg group, –0.16 mm in the SM04690 0.07-mg group, and –0.03 mm in the SM04690 0.23-mg group.

An improvement in mean medial joint space narrowing was observed in 47.6% with SM04690 0.03 mg, 40.5% with 0.07 mg, 39.6% with 0.23 mg, and 30.5% with placebo. There was no change in a respective 7.6%, 9%, 17.8%, and 11.4%, and narrowing in the remainder (44.8%, 50.5%, 42,6%, and 58.1%) in this intent-to-treat population.

The investigators conducted prespecified subanalyses in a “unilateral symptomatic” population of 164 patients, and this showed slightly better results, with a higher probability of improved medial joint space width with SM04690 than with placebo (odds ratio, 5.2; 95% confidence interval, 2.1-12.8; P less than .001).

However, an important limitation of the study is that it was not formerly powered to look at radiographic progression, Dr. Yazici said. Nevertheless, radiographs were centrally read and high intra- and inter-observer reproducibility was observed.

Safety and clinical outcomes from the trial, which were reported separately in a poster at the meeting, showed no undue concerns and clinically meaningful improvements in both patients’ and physicians’ global assessments of pain with SM04690 versus placebo.

“Radiographic and clinical outcomes from this 26-week interim analysis of a 52-week trial suggest that SM04690 has potential as a disease-modifying osteoarthritis drug (DMOAD) for knee OA,” Dr. Yazici concluded.

The studies were supported by Samumed and by Centrexion Therapeutics. Dr. Yazici is an employee and shareholder of Samumed. Dr. Stevens is an employee and shareholder of Centrexion Therapeutics.