Budget Model Analyzes Formulary Costs for Obesity Drugs

Boston—An understanding of the formulary cost implications associated with the addition of new anti-obesity treatments is important to health plans in determining whether new treatments are cost-effective. Naltrexone/bupropion is 1 of the newer weight management drugs granted FDA approval. A recent study evaluated formulary cost implications associated with the addition of naltrexone/bupropion for the treatment of obesity in the United States. The researchers presented the study’s results at the AMCP meeting during a poster session titled The Economics of Anti-Obesity Treatment: Evaluating the Budget Impact to Payers in the United States Associated with New and Existing Anti-Obesity Medications.

A pharmacy budget impact model was created to estimate the new budget impact associated with the addition of naltrexone/bupropion to a formulary (calculated as the difference in cumulative costs for each year with and without naltrexone/bupropion) over 1, 2, and 3 years for a plan with 1 million members. The researchers also conducted a supplementary analysis of a plan with 500,000 members. Estimation of the number of patients eligible for anti-obesity treatment was derived from the US National Health and Wellness Survey. Naltrexone/bupropion share of market was assumed to be 5.4%, 7.7%, and 8.6% in years 1, 2, and 3, respectively. The medication’s market share was sourced proportionally based on existing market share of phentermine (80.7%), lorcaserin (5.4%), phentermine/topiramate (6.7%), and 7% from other products on the market. The model assumed that patients received 1-year duration of therapy.

The annual acquisition cost of phentermine was based on a current wholesale acquisition cost (WAC) of $128 ($0.35/day), lorcaserin and phentermine/topiramate were priced at $2394 ($199.50/month), and other products were priced based on the WAC of orlistat ($1070/year). Naltrexone/bupropion was priced at parity with lorcaserin, phentermine/topiramate, and other products based on a supply of 70 tablets in month 1 and 120 tablets in subsequent months ($2311/year).

The study’s results indicated that the number of patients estimated to receive an anti-obesity medication was 3360 in year 1 and was projected to grow by 9.6% in year 2 (n=3684) and 11.3% in year 3 (n=4098). The total budget impact to a plan of 1 million members was estimated to be $1,863,877, $2,137,873, and $2,430,471 in years 1, 2, and 3, respectively. With naltrexone/bupropion added to the formula, the resultant budget impact was 21.8%, 33.1%, and 37.8% greater in years 1, 2, and 3, respectively. The net cumulative total budget to a plan of 1 million members was estimated to be $333,925, $865,031, and $1,531,669 in years 1, 2, and 3, respectively.

The corresponding per-member, per-month (PMPM) cost was between $0.03 and $0.04 for a plan size of 1 million and 500,000. Assuming a 50% increase in naltrexone/bupropion market share, the net cumulative total budget impact to a plan of 1 million members was estimated to be $500,887, $1,297,505, and $2,297,231 in years 1, 2, and 3, respectively.

While the addition of naltrexone/bupropion to a formulary was generally associated with a PMPM cost of <$0.05, the researchers noted that the analysis did not consider the implications of therapy discontinuation; therefore, the budget impact
associated with this medication is likely overestimated. They also acknowledged that additional relevant costs to a health plan were not captured in this analysis.—Eileen Koutnik-Fotopoulos

This study was supported by Takeda Pharmaceuticals Ltd.