PHOENIX study evaluates the safety, efficacy of ustekinumab in treating plaque psoriasis

July 1, 2008

PHOENIX 1 is a phase 3 study evaluating the efficacy and safety of ustekinumab (Centocor), a fully human interleukin-12/23p40 monoclonal antibody, in patients with moderate-to-severe chronic plaque psoriasis. The study randomized 766 patients to receive ustekinumab 45 mg, ustekinumab 90 mg or placebo at weeks zero and four. Data from 52 weeks and 76 weeks show high proportions of patients are maintaining PASI 75 responses with maintenance injections every 12 weeks.

Key Points

PHOENIX 1 (phase 3, multicenter, randomized, double-blind, placebo-controlled trial, evaluating the efficacy and safety of CNTO 1275 in the treatment of subjects with moderate-to-severe plaque-type psoriasis, followed by long-term extension 1) is evaluating the efficacy and safety of ustekinumab (formerly known as CNTO 1275) in patients with moderate-to-severe chronic plaque psoriasis.

Study parameters

In the ustekinumab groups, treatment continued with the same dose administered every 12 weeks.

Placebo patients were re-randomized to ustekinumab 45 mg or 90 mg at week 12 and received two induction doses followed by treatment every 12 weeks.

At week 40, patients responding to ustekinumab with a 75 percent reduction from baseline Psoriasis Area and Severity Index (PASI) score (PASI 75 response) were randomized to either continue treatment with the same dose of ustekinumab or placebo.

At the primary efficacy endpoint assessment at week 12, two-thirds of patients in both ustekinumab dose groups were PASI 75 responders, compared with only 3 percent of placebo-treated controls.

At one year, 87 percent of patients responding to ustekinumab 45 mg maintenance therapy and 91 percent of patients responding to ustekinumab 90 mg maintenance therapy were still benefiting with a PASI 75 response.

At week 76, the PASI 75 responder rates in the ustekinumab 45 mg and 90 mg groups were 82 percent and 87 percent, respectively.

"With other biologics - some more than others - there is a trend for a slow loss of response after the primary efficacy analysis at 10 to 12 weeks.

"The results of PHOENIX 1 show that over the long term, the vast majority of patients achieving a PASI 75 response to ustekinumab can maintain that benefit with infrequently administered maintenance injections," says Alan Menter, M.D., an investigator in PHOENIX I and director, psoriasis research unit, Baylor Research Institute, Dallas, Texas.

Patients were eligible for PHOENIX 1 if they were 18 years of age or older and had a baseline PASI score of 12 or higher and body surface area involvement of at least 10 percent.

The average patient had psoriasis for almost 20 years with a baseline PASI score of about 20 and almost 25 percent body surface area involvement. More than 40 percent of patients were judged to have marked or severe psoriasis at baseline, according to the physician's global assessment.

Majority essentially clear

The study data showed impressively that 42 percent of patients treated with ustekinumab 45 mg and 37 percent of patients in the ustekinumab 90 mg group achieved a PASI 90 response at week 12. Those proportions increased over time.

At week 76, about half of patients treated with ustekinumab 45 mg and almost two-thirds of patients continuing with ustekinumab 90 mg maintained a PASI 90 response.

"Excluding some smaller studies, this is the first time that we can start talking about PASI 90 responses in a way that is clinically meaningful," Dr. Menter tells Dermatology Times.

Among ustekinumab-treated patients who were crossed over to placebo at week 40, the PASI 90 responder rates fell to just below 40 percent.