Amgen's $400M Eczema Drug Achieves Phase 3 Success, Dupixent Rivalry Uncertain

Amgen has revealed the initial findings from its phase 3 trial concerning rocatinlimab, a drug for eczema developed through a $400 million deal with Kyowa Kirin. The trial aimed to determine the efficacy of this anti-OX40 antibody in alleviating symptoms of moderate to severe atopic dermatitis, a type of eczema. Despite achieving the primary endpoints, Amgen faces the challenge of justifying rocatinlimab's place in a market already dominated by Dupixent.

The HORIZON phase 3 trial involved 726 participants with moderate to severe atopic dermatitis who were randomized to receive either rocatinlimab or a placebo. After 24 weeks, 32.8% of those receiving rocatinlimab showed a 75% improvement in the eczema area and severity index (EASI-75), compared to just 13.7% in the placebo group, meeting one of the trial's primary endpoints.

Furthermore, Amgen reported notable differences in the proportion of patients who were assessed as clear or almost clear using the clinician evaluation scales vIGA-AD and rIGA. Specifically, 19.3% of the rocatinlimab group met the vIGA-AD criteria compared to 6.6% of the placebo group, while 16.4% of the rocatinlimab group met the rIGA criteria, against 4.9% of the placebo group. All measurements were recorded after a 24-week treatment period.

However, the success of rocatinlimab must be viewed in the context of existing treatments. For instance, Regeneron and Sanofi's Dupixent, another eczema medication, demonstrated greater efficacy in its phase 3 trials, with 51% and 44% of patients achieving a 75% improvement in eczema severity, compared to 15% and 12% for placebos, respectively. This has led analysts to critically compare Amgen's data with that of its competitors.

William Blair analysts noted that although rocatinlimab met the trial's endpoints, the results fell short of expectations, prompting questions about its competitive position in an increasingly crowded market. During a discussion about the data, Amgen's Executive Vice President of Global Commercial Operations, Murdo Gordon, highlighted the unmet needs in the atopic dermatitis market that rocatinlimab might address due to its distinct mechanism of action.

Gordon pointed out that many patients change their treatment plans within the first few months and often discontinue therapy within a year, suggesting a dynamic market with room for new treatment options. Notably, Amgen's study included participants who had previously used biologics like Dupixent, although the company did not disclose how many of these patients had such prior exposure. Analyzing the results for biologic-experienced patients separately could provide a clearer comparison between rocatinlimab and Dupixent.

Amgen has withheld some specific details, such as the breakdown of prior therapies and full data on the rate of side effects like fever and chills. In a preceding phase 2b trial, 17% of patients experienced fever, and 11% had chills. While Amgen stated that rocatinlimab's side effects were manageable, the lack of detailed safety data has left some analysts seeking more information.

Jay Bradner, M.D., Amgen’s Executive Vice President of R&D, explained the benefits of targeting the OX40 molecule directly rather than its ligand. He suggested that OX40-directed therapies could potentially offer broader benefits by rebalancing T cells, which might not only impact atopic dermatitis but also other related inflammatory conditions.

Amgen’s strategic partnership with Kyowa Kirin, which involved a $400 million upfront payment, is part of a comprehensive development plan featuring eight critical trials for atopic dermatitis. The company aims to gather the data necessary to establish rocatinlimab as a significant player in the eczema treatment landscape, with more trial results expected by late 2024 or early 2025.