Horizon Therapeutics plc Announces Phase 2 Trial Evaluating Daxdilimab for the Treatment of Systemic Lupus Erythematosus (SLE) Did Not Meet Primary Endpoint

- The Company continues to assess the full dataset; daxdilimab trials in alopecia areata, discoid lupus erythematosus and lupus nephritis ongoing –

Horizon Therapeutics plc (Nasdaq: HZNP) today announced that its Phase 2 clinical trial evaluating daxdilimab for the treatment of SLE did not show a statistically significant separation between daxdilimab and placebo on the primary endpoint, which was the proportion of patients to achieve a British Isles Lupus Assessment Group (BILAG) 2004 Index-based Combined Lupus Assessment (BICLA) response and an oral glucocorticoid (OGC) dose of ≤7.5 mg/day (prednisone equivalent), which represented a reduction from the Baseline OGC dose at 48 weeks. BICLA is a composite measure indicating low SLE disease activity. Numerical differences were seen in other endpoints. No safety concerns were reported.

“While we are disappointed that the trial did not meet its primary endpoint, we will continue to work with investigators to assess these data to determine next steps for our SLE clinical program,” said Elizabeth H.Z. Thompson, Ph.D., executive vice president, research and development, Horizon. “I would like to thank the patients and investigators for their participation in the trial.”

About the Daxdilimab Phase 2 Clinical Trial in Systemic Lupus Erythematosus

The Phase 2 study enrolled patients with moderate-to-severely active SLE. A total of 214 patients were randomized into three parallel arms: daxdilimab given subcutaneously 200 mg every 4 weeks, 200 mg every 12 weeks or placebo every 4 weeks. Additional trial endpoints included the Systemic Lupus Erythematosus Responder Index of 4 (SRI-4), other measures of lupus disease activity and reduction in OGC.

About Daxdilimab

Daxdilimab is an anti-ILT7 human monoclonal antibody that depletes certain dendritic cells. Depleting these cells may interrupt the cycle of inflammation that causes tissue damage in a variety of autoimmune conditions. Horizon is also investigating daxdilimab in alopecia areata, discoid lupus erythematosus and lupus nephritis and plans to investigate it in dermatomyositis or anti-synthetase inflammatory myositis.

About Horizon

Horizon is a global biotechnology company focused on the discovery, development and commercialization of medicines that address critical needs for people impacted by rare, autoimmune and severe inflammatory diseases. Our pipeline is purposeful: We apply scientific expertise and courage to bring clinically meaningful therapies to patients. We believe science and compassion must work together to transform lives. For more information on how we go to incredible lengths to impact lives, visit www.horizontherapeutics.com and follow us on Twitter, LinkedIn, Instagram and Facebook.

Forward-Looking Statements:

This press release contains forward-looking statements, including statements regarding Horizon’s future development plans for daxdilimab. These forward-looking statements are based on management’s expectations and assumptions as of the date of this press release and other results may differ materially from those in these forward-looking statements as a result of various factors. These factors include, but are not limited to, risks regarding whether future data analyses or clinical trial results will support further clinical development and potential delays in initiating or completing clinical trials. For a further description of these and other risks facing Horizon, please see the risk factors described in Horizon’s filings with the United States Securities and Exchange Commission, including those factors discussed under the caption “Risk Factors” in those filings. Forward-looking statements speak only as of the date of this press release and Horizon undertakes no obligation to update or revise these statements, except as may be required by law.

References

1. Furie RA, Petri MA, Wallace DJ, et al. Novel evidence-based systemic lupus erythematosus responder index. Arthritis Rheum. 2009;61(9):1143-1151.

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