Mirum Pharmaceuticals announced on October 12 that Livmarli, its oral IBAT inhibitor maralixibat, met the primary endpoint of the Phase 3 EXPAND study in cholestatic pruritus in patients aged six months or older with ultra-rare cholestatic liver diseases, including biliary atresia. The study also achieved statistical significance across all five prespecified secondary endpoints, including the three endpoints in patients with biliary atresia and a native liver.
EXPAND enrolled 52 patients, 46 of them pediatric and six adult, randomized to maralixibat at 285 micrograms per kilogram twice daily or placebo over a 20-week double-blind period. In the primary analysis population of pediatric patients, itch severity on the observer-reported ItchRO scale improved by 1.81 points from baseline during weeks 13 to 20, against 0.83 points on placebo, a placebo-adjusted difference of 0.98 points with a p value of 0.0004. Serum bile acids fell 70.1 percent from baseline on treatment against 3.5 percent on placebo.
The company said safety findings were consistent with prior experience with maralixibat and that no new safety signals were observed. Livmarli is already approved in the United States for cholestatic pruritus in Alagille syndrome and in progressive familial intrahepatic cholestasis, so EXPAND is a label-expansion study rather than a first approval path.
Mirum said it plans to file a supplemental new drug application with the FDA in the first half of 2027 based on the EXPAND results. For a rare-disease company, each added indication compounds the same commercial infrastructure, and biliary atresia is the largest of the ultra-rare cholestatic populations in the study. The filing timeline, not the readout, is now the catalyst to watch.