Novel knee osteoarthritis drugs target pain, joint space narrowing
AT THE EULAR 2017 CONGRESS
MADRID – Two independently conducted, randomized, phase 2 trials of novel agents for moderate to severe knee osteoarthritis have produced promising results, as reported at the European Congress of Rheumatology.
In the 24-week, dose-ranging TRIUMPH trial involving 175 patients, treatment with the synthetic trans-capsaicin CNTX-4975 was associated with improvements in several clinical parameters, such as pain when walking, knee stiffness, and physical function, as well as being generally well tolerated.
These findings suggest that both could be future alternatives to using nonsteroidal anti-inflammatory drugs (NSAIDs), injected corticosteroids, and opioid analgesics, which are currently used to help manage knee OA.
Synthetic trans-capsaicin CNTX-4975
“Few effective pharmacologic therapies are available to manage the chronic pain of OA,” said Randall Stevens, MD, chief medical officer for Centrexion Therapeutics (Boston), the company developing CNTX-4975. Both NSAIDs and corticosteroids are associated with substantial toxicities, he argued, and opioid analgesics are not ideal to use long term because of the risk of side effects and addiction.
CNTX-4975 is a nonopioid analgesic that acts directly on the pain fibers in the knee, Dr. Stevens explained. Specifically, after a single injection, it targets the capsaicin receptor (transient receptor potential vanilloid 1, TRPV1) to inactivate only the local fibers transmitting pain signals to the brain. It does not affect other sensory fibers involved in sensation to touch or pressure, he said.
The aim of the phase 2b TRIUMPH trial was to examine the efficacy and safety of two doses (0.5 mg and 1.0 mg) of the synthetic trans-capsaicin versus placebo in patients with chronic, stable, moderate to severe knee OA who had been experiencing knee pain for at least 2 months or more. For inclusion, patients could be aged between 45 and 80 years, have a body mass index of up to 45 kg/m2, and had to have failed treatment or not be able to tolerate oral or intra-articular analgesics. Patients who had undergone recent knee surgery were excluded.
The primary endpoint was the change in pain with walking from baseline to week 12 measured as the area under the curve (AUC) for daily Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) A1 score. Significant improvements were seen, with a least squares mean difference (LSMD) of –0.8 (P = .07) and –1.6 (P less than .0001) with the 0.5 mg and 1.0 mg doses of CNTX-4975, respectively, versus placebo.
The effects of CNTX-4975 were maintained to 24 weeks, Dr. Stevens reported, with significant improvements in pain with walking, comparing the 1.0-mg dose with placebo (LSMD, –1.35; P = .0002).
“These are the largest effect sizes I’ve seen with osteoarthritis knee pain,” Dr. Stevens said.
The investigators saw improvements in other efficacy endpoints, such as the weekly pain with walking (WOMAC A1) score and the change in weekly average joint stiffness (WOMAC B subscale, LSMD: −2.5; P = .0013) and physical function (WOMAC C subscale, LSMD: −18.3; P = .004) versus placebo at week 12. Numerically greater improvements occurred at week 24.
A similar percentage of patients experienced any treatment-emergent adverse events in the 1.0-mg (29.6%) CNTX-4975 treated and placebo groups (30%). Although a higher percentage of patients given the lower CNTX-4975 dose reported side effects (47.1%), most were mild to moderate and were considered unrelated to study treatment. Arthralgia was the most common side effect with CNTX-4975 1.0 mg versus placebo (7% vs. 5.7%).
“With these findings, we are moving in to phase 3 with the 1.0-mg dose,” Dr. Stevens said.
Wnt inhibitor SM04690
Promising data from the phase 2 trial of the Wnt inhibitor SM04690 also suggest that it, too, could soon be heading into phase 3 trials.
