Cost efficacy

Key Points

Horsham, Pa. - Results of cost-efficacy analyses determining the cost for a successful outcome in the treatment of moderate-to-severe chronic plaque psoriasis show meaningful differences between the two tumor necrosis (TNF)-alpha inhibitors, infliximab (Remicade, Centocor) and etanercept (Enbrel, Amgen/Wyeth), that favor infliximab.

The pharmacoeconomic analysis was presented by Mirza Rahman, M.D., M.P.H., and colleagues from Centocor in a poster at the 65^th Annual Meeting of the American Academy of Dermatology (AAD). It used outcomes data from phase 3 pivotal trials of infliximab and etanercept to determine the incremental benefit of each biologic agent relative to placebo in achieving a 50 percent or 75 percent reduction in Psoriasis Area and Severity Index (PASI) score. From that data, the number needed to treat (NNT) to achieve a successful outcome was determined.

Cost of treatment was calculated for the first year, based on loading and maintenance doses recommended in the prescribing information, medication cost (average whole price – 15 percent) and administration cost ($225 per infliximab infusion). The cost per successful outcome based on a PASI-75 response was $30,959 for infliximab and $40,903 for etanercept. Corresponding costs for a PASI-50 response were $28,737 and $29,801, respectively.

"Nevertheless, we believe these data provide some useful context that should be helpful to administrators in managed care organizations who are involved in making formulary decisions."

STUDY PARTICULARS

Efficacy data for infliximab were derived from the 24-week outcomes of the 46-week European InfliXimab for Psoriasis (Remicade) Efficacy and Safety Study (EXPRESS) where patients were randomized to receive infliximab 5 mg/kg or placebo at weeks zero, two and six, and then every eight weeks to week 24 (Reich K, Nestle FO, Papp K, et al; EXPRESS study investigators. Lancet. 2005; 366:1367-1374).

The efficacy results for etanercept were extracted from a 24-week global study where patients were randomized to etanercept, 25 mg or 50 mg, or placebo twice weekly for 12 weeks, followed by etanercept, 25 mg twice weekly, in all patients (Papp KA, Tyring S, Lahfa M, et al; Etanercept Psoriasis Study Group. Br J Dermatol. 2005; 152:1304-1312). Since patients received placebo only through week 12, the response at that visit was used to estimate the week 24 placebo response considering that in infliximab studies, PASI scores in placebo-treated patients were stable between weeks 12 and 24.

The infliximab and etanercept pivotal trials had similar inclusion and exclusion criteria and enrolled a similar number of patients. Patients in EXPRESS had a greater mean percent body surface area of involvement compared with the etanercept trial population (~34 percent vs. ~23 percent) and a higher mean baseline PASI score (~23 vs. ~16).

At week 24 in EXPRESS, a PASI-75 response was achieved by 82 percent of infliximab patients and 4 percent of placebo patients. Based on the 78 percent difference in responder rates, the NNT for a successful outcome with infliximab was calculated as 1.12.

The week 24 PASI-75 response rate was 54 percent in the etanercept group and 3 percent in the placebo group so that the NNT for etanercept was 1.96.

Using the one-year horizon, it was estimated that infliximab patients would receive 8.75 infusions (three induction doses at weeks zero, two and six followed by maintenance every eight weeks) with an average of 4.5 100 mg vials used per infusion at a cost of $570 per vial plus an administration cost of $225 per infusion. Etanercept cost was based on receipt of a total of 128 25 mg doses using a dosing schedule of 50 mg, twice a week for 12 weeks, followed by 50 mg once a week at a cost of $160 per 25 mg syringe.