Entrenching and Leveraging Market Dominance in the 2023 Merger Guidelines: Insights from Amgen/Horizon


The authors explore relevant factors in the Amgen/Horizon merger challenge as an illustration of the analytical framework for the theory of leveraging market dominance via bundling in the new Merger Guidelines

The Agencies’ new Merger Guidelines (December 2023) include some novel theories, such as the theory in Guideline 6 of leveraging market dominance in one market into another market by linking the sale of products in the two markets. Guideline 6 does not provide an analytical framework for evaluating competitive harm under this theory of leveraging market dominance into another market.

The Amgen/Horizon merger challenge included allegations about leveraging market power in the market for blockbuster drugs to block entry in markets for rare diseases drugs by bundling the two sets of drugs and offering bundled discounts and, in turn, harming competition. The analysis of the theory in Amgen/Horizon illustrates the factors relevant for an analysis of a theory of leveraging via bundling.

This article was originally published The Antitrust Source in April 2024.


  • Los Angeles

James Lee


  • Chicago

Ana McDowall


Darius Lakdawalla

Quintiles Chair in Pharmaceutical Development and Regulatory Innovation, School of Pharmacy,
Professor, Sol Price School of Public Policy,
Director of Research, Leonard D. Schaeffer Center for Health Policy and Economics,
University of Southern California