Amgen's lupus bets continue to flounder, even those on the Horizon

Amgen’s lupus pursuits have encountered another pitfall, this time via potential acquisition of Horizon Therapeutics. 

Horizon reported that its lupus candidate daxdilimab did not produce a meaningful difference in assessment of disease activity compared to placebo, according to results announced late Friday. The biotech said “numerical differences” were identified in other endpoints in the phase 2 trial and that no safety concerns were reported. 

The study recruited 214 patients who were randomized across three arms: 200 mg of daxdilimab given subcutaneously every four weeks, 200 mg given every 12 weeks or placebo given every four weeks. Horizon is also studying the drug in other forms of lupus and alopecia, with plans to widen the potential use into myositis, a condition where a patient’s immune cells attack their muscles. 

Horizon’s research chief Elizabeth Thompson, Ph.D., said in a release that the company would work with investigators to comb through the data and “determine next steps for our [systemic lupus erythematosus] clinical program.” 

What may be a trip up for Horizon is also a gut punch for Amgen, in light of the fact that the California pharma’s lupus ambitions have yet to pan out. After the first quarter of the year, Amgen cut two lupus programs due to futility. 

“SLE remains a challenging area for drug development, one that will be an area of focus for us as we further explore these datasets to advance our knowledge in the field,” David Reese, M.D., Amgen’s head of R&D, said on a first-quarter earnings call in April. He referenced the company’s excitement to weave in Horizon’s meds to help make a breakthrough in immunology diseases. 

Amgen announced late last year that it planned to buy Horizon for just under $28 billion but the U.S. Federal Trade Commission sued to block the deal in May. 

Lupus has been a tough nut to crack for the biopharmaceutical industry due to the heterogeneous nature of the disease. One person’s immune system—and associated defects—may look much different than someone else's. The difficulty was succinctly set out by Roivant CEO Matt Gline in a previous interview with Fierce Biotech, as his own company awaits a midstage lupus readout from brepocitinib later this year.

“Anybody who is not afraid of a lupus study is an idiot, you shouldn’t trust them,” Gline said at the time.

Editor's note: This story was updated to reflect that Amgen's deal with Horizon has yet to close after the U.S. FTC intervened.