Arrowhead’s RNAi Obesity Drug Boosts Weight Loss When Paired With Zepbound

Arrowhead Pharmaceuticals has reported encouraging interim results from a Phase I/IIa trial evaluating its RNA interference obesity drug, ARO-INHBE, in combination with Eli Lilly’s Zepbound (tirzepatide). In obese patients with type 2 diabetes, the combination delivered significantly greater benefits than Zepbound alone.

After 16 weeks, patients receiving the combination achieved 9.4% weight loss, compared with 4.8% in the Zepbound-only group. The therapy also produced markedly larger reductions in visceral fat, total body fat and liver fat, including a 76.7% drop in liver fat at 12 weeks versus 20% with monotherapy. ARO-INHBE alone also showed meaningful fat reductions while preserving lean tissue. The drug was generally well tolerated, with mostly mild side effects.

Arrowhead also shared early data for its second RNAi candidate, ARO-ALK7, which achieved strong, dose-dependent suppression of its genetic target. The positive updates boosted Arrowhead’s share price and highlight growing momentum in the obesity drug market.

12-01-2026