Mirum Pharmaceuticals' Phase 3 EXPAND Study Evaluating LIVMARLI Meets Primary Endpoint, Achieves Statistical Significance Across All Secondary Endpoints

- Maralixibat demonstrated a statistically significant reduction in cholestatic pruritus compared with placebo (p=0.0004), and a 69% reduction in serum bile acids versus placebo (p<0.0001)

- In patients with biliary atresia, maralixibat demonstrated a statistically significant reduction in cholestatic pruritus compared with placebo (p=0.0002)

- Mirum plans U.S. sNDA submission in the first half of 2027 based on positive EXPAND results

- Mirum to host conference call to discuss topline results today, October 12, at 8:30 a.m. ET

Mirum Pharmaceuticals, Inc. (NASDAQ:MIRM), a leading rare disease company, today announced topline results from the Phase 3 EXPAND study evaluating LIVMARLI® (maralixibat) for the treatment of cholestatic pruritus in patients aged 6 months or older with ultra-rare cholestatic liver diseases, including biliary atresia. The study met its primary endpoint and achieved statistical significance across all five prespecified secondary endpoints, including the three endpoints in patients with biliary atresia and a native liver.

The Phase 3 EXPAND study enrolled 52 patients, including 46 pediatric and six adult patients, who were randomized during the 20-week double-blind period to treatment with maralixibat 285 µg/kg twice daily (BID) or placebo.

Treatment with maralixibat demonstrated a statistically significant improvement in pruritus compared with placebo in the primary analysis population of pediatric patients. Maralixibat resulted in a mean 1.81-point improvement from baseline in average worst-daily ItchRO(Obs) severity score during Weeks 13-20 compared with a 0.83-point improvement for placebo, corresponding to a placebo-adjusted treatment difference of 0.98 points (p=0.0004). Maralixibat also resulted in a 70.1% reduction from baseline in serum bile acids (sBA), compared with 3.5% for placebo, corresponding to a 69.0% treatment effect versus placebo (p<0.0001). Key efficacy data from the Phase 3 EXPAND study are presented below in the Efficacy Results table.

Safety findings in EXPAND were consistent with prior clinical experience with maralixibat and no new safety signals were observed. Key safety data from the Phase 3 EXPAND study are presented below in the Safety Summary table.