Arrowhead Pharmaceutical’s investigational RNA interference (RNAi) obesity candidate in combination with Eli Lilly’s Zepbound (tirzepatide) has shown benefit in interim data from a Phase I/IIa trial.
In the ongoing study (NCT06700538), Arrowhead’s candidate, called ARO-INHBE, plus Zepbound, doubled weight loss and tripled reductions in visceral fat, total fat, and liver fat versus Zepbound alone in obese patients with type 2 diabetes mellitus.
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Weight loss in the combination group was 9.4% after 16 weeks compared with 4.8% in those treated with Zepbound plus placebo. Total fat reduction at 12 weeks was 15.4% in the combo group compared with 5.3% in those treated with Zepbound alone.
Liver fat reduction was also significant at 12 weeks, with a 76.7% reduction in the treatment cohort compared with 20% in the monotherapy group.
Reduction in weight was also seen in those treated with a single dose of ARO-INHBE alone, with mean visceral fat reduction of 9.9%, liver fat reduction of 38% and a 3.6% increase in total lean tissue.
The drug was well tolerated as both a monotherapy and in combination, with most adverse events being mild in severity.
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By GlobalDataARO-INHBE acts by inhibiting the inhibin subunit beta E (INHBE) gene, as an increase in the INHBE gene causes insulin resistance.
Arrowhead also released data from the Phase I/IIa trial (NCT06937203) of its second candidate, ARO-ALK7, an RNAi designed to silence adipocyte expression of the ACVR1C gene to reduce production of Activin receptor-like kinase 7 (ALK7), in obesity. In the trial, the drug led to dose-dependent reductions in adipose ALK7 mRNA with a mean reduction of 88% in the 200mg dose after eight weeks, with a maximum reduction of 94%.
After releasing the data, Arrowhead’s stock rose by 6% from a $63.88 close on 5 January to a $68.00 open on 6 January; however, the company’s stock continued to rise through the day, hitting a $76.76 high.
Arrowhead’s data comes at a time when the obesity sector is accelerating in growth. As per GlobalData’s The State of the Biopharmaceutical Industry 2026, experts predict obesity medications will remain a key theme in 2026 across the pharmaceutical sector.
GlobalData is the parent company of Clinical Trials Arena.
Lilly’s Zepbound is set to be a major player in the obesity sector in the coming years, with GlobalData’s patient-based forecast predicting sales of the drug in obesity to reach $48.55bn in 2031.
Meanwhile, sales of Novo Nordisk’s Wegovy (semaglutide), the other current major player in the field, are set to reach $23.57bn for the subcutaneous version in 2031, while sales of the oral version are set to reach $4.48bn in the same year.
