MILAN – A novel topical nonsteroidal treatment for psoriasis showed sufficient efficacy in phase 2b clinical trials to proceed to phase 3 studies, with improvements in severity, pain, and burning in adults with mild to moderate psoriasis.
At the end of 12 weeks of treatment, 29% of patients receiving the medication – which targets nerve pathways – experienced a decrease of at least 2 grades on the 5-point Investigator’s Global Assessment (IGA) scale, compared with 13% of those receiving the topical vehicle only (P = .036). A similar proportion of patients achieved 75% improvement on the Psoriasis Area and Severity Index (PASI-75)compared with those on vehicle alone (27% versus 13%; P = .045).
, said Paul F. Lizzul, MD, PhD, presenting the findings during a late-breaking abstract session at the World Congress of Dermatology.
Pruritus severity also dropped by about 60%, but the decrease did not differ significantly from the change seen with vehicle alone, said Dr. Lizzul, chief medical officer for Sienna Biopharmaceuticals, Westlake Village, Calif., which funded the study. He and his coinvestigators found this “interesting, surprising, and different from what we had seen previously,” he said. “We think a few things happened here,” including intensive querying on itch by means of daily diaries, a different approach than had been taken in the investigator’s earlier SNA-120 trials. “We think in this way we probably biased patients’ expectations, altering reporting on this subjective measure,” he added.
“There’s been really a lack of innovation in the topical world in developing nonsteroidal therapies for the majority of patients who are treated with topicals, said Dr. Lizzul. Keratinocytes within psoriatic plaques are known to have elevated levels of nerve growth factor (NGF), he explained. Together with tropomyosin receptor kinase A (TrkA), NGF is implicated in the pathogenesis of psoriasis; it stimulates keratinocyte hyperproliferation, is a factor in neurogenic inflammation, and contributes to pruritus. Upregulation of TrkA expression is seen in nerve fibers within pruritic psoriasis plaques as well, said Dr. Lizzul, senior author of the study. (The first author was, cochair of the dermatology department at the University of Utah, Salt Lake City.)
In fact, the pruritus that plagues many psoriasis patients, said Dr. Lizzul, may “serve as a clinical biomarker for elevated NGF/TrkA expression.” And certain clinical phenomena observed in psoriasis, such as the Koebner phenomenon and plaque resolution along the path of damaged nerves, provide other clues. “Clearly, astute clinicians going back many, many years have recognized the very important role that nerves and neuropeptides play in psoriasis,” he added.
SNA-120 targets NGF TrKA activity, and “achieves high local drug concentration in the skin, with low systemic availability,” he said.
The randomized, double-blind, vehicle-controlled study enrolled 208 adults with mild to moderate psoriasis (scores of 2 or 3 on the IGA), with pruritus of at least moderate intensity (5 or higher on a 10-point itch numeric rating scale, or I-NRS). The mean age of the patients was 50 years, and about half were male. Most (84%-90% across study arms) were white. At baseline, the mean I-NRS was 7.3-7.4, and the mean PASI score at baseline ranged from 5.9 to 6.5.
Patients were randomized to receive SNA-120 twice daily at either 0.05% (70 patients) or 0.5% (69 patients) in an ointment formulation, or vehicle alone twice daily (69 patients). Efficacy was tracked by measuring decrease in IGA by one or two grades, the number of patients achieving PASI-50 and PASI-75, reduction in itch, and a composite of a decrease of at least 2 grades on the IGA and having clear or almost clear skin.
The investigators also tracked reduction in burning and pain as measured on a 10-point numeric rating scale. Though itch scores didn’t differ significantly from reductions seen with the topical vehicle alone, pain and burning were both reduced significantly compared with vehicle by week 12 of the study (P = .033 for pain; P = .043 for burning).
All improvements were seen only with the lower dose, not the 0.5% dose of SNA-120, noted Dr. Lizzul, adding: “This is not necessarily surprising in the world of kinase inhibitors, where you can see these J-shaped or inverse dose-response curves.”
In addition to recording adverse events, the researchers assessed safety by obtaining laboratory values and electrocardiograms. Plasma SNA-120 levels at study weeks 2, 4, and 8 were obtained for pharmacokinetic analysis. Systemic uptake was virtually nil, and the safety profile overall was good, said Dr. Lizzul.
Next steps are phase 3 clinical trials that will evaluate global improvement as well as pain, burning, and itch in psoriasis, he noted.
Dr. Lizzul is an employee of Sienna Biopharmaceuticals, which is developing SNA-120.