Mirum Pharmaceuticals, Inc. presented new analyses from LIVMARLI™ (maralixibat) oral solution clinical studies during the North American Society for Pediatric Gastroenterology Hepatology and Nutrition Annual Meeting, taking place virtually December 12-18, 2021. These post-hoc analyses assessed the impact of maralixibat treatment response on changes in health-related quality of life (HRQoL) measures among children with Alagille syndrome (ALGS) and progressive familial intrahepatic cholestasis (PFIC) with BSEP deficiency (also known as PFIC2). Response to treatment with maralixibat in Alagille syndrome is associated with improved health-related quality of life: The analysis evaluated 27 patients with ALGS who received 380 µg/kg per day of LIVMARLI and who remained in the ICONIC study1 through Week 48, comparing their HRQoL outcomes as reported at baseline and at Week 48. Treatment response to LIVMARLI was defined as a =1 point reduction in caregiver Itch-Reported Outcome (ItchRO) instrument score from baseline to Week 48. In addition, the Pediatric Quality of Life (PedsQL) questionnaires (Generic Core PedsQL, Family Impact Scale, and Multidimensional Fatigue Scale) were prospectively collected via a caregiver proxy report and analyzed retrospectively. At Week 48, 20 patients (74%) met the definition of ItchRO response. Responders showed improved HRQoL measures compared with non-responders: Multidimensional Fatigue Total Scale Score from baseline to Week 48 (increase of 13.9 points) more than two times the minimal clinically important difference in responders. Six sleep-related items demonstrated significantly larger changes from baseline to Week 48 in responders. PedsQL Generic Core Total Scale Score increased on average by 8.8 points, almost two times the minimal clinically important difference in responders. These data demonstrate that the significant improvements in pruritus seen with LIVMARLI at Week 48 of the ICONIC study are clinically meaningful and are associated with improvements in patients’ quality of life. The analysis examined 22 patients with BSEP deficiency, or PFIC2, following treatment with LIVMARLI as part of the INDIGO study. The dose-escalation study evaluated LIVMARLI at 266 µg/kg per day followed by a long-term stable dosing where patients were allowed to increase to twice-daily dosing from Week 72. The study endpoints were response to treatment with LIVMARLI as defined by a >75% decrease from baseline or reduction below 102 µmol/L in serum bile acid (sBA) at Week 48. HRQoL was assessed using the PedsQL, Family Impact Scale, and Multidimensional Fatigue Scale questionnaires, and all were assessed by caregivers. Overall, patients with PFIC2 who achieved sBA treatment response at Week 48 experienced clinically meaningful improvements in PedsQL Generic Core Total Scale Score and Multidimensional Fatigue Total Scale Score, as well as statistically significant improvements in sleep and fatigue: Responders experienced an improvement from baseline to Week 48 across all HRQoL measures. Statistically significant differences were observed between responders versus non-responders as observed in the PedsQL Generic Core Score and Multidimensional Fatigue Scores. The change in Family Impact Score from baseline to Week 48 for responders was clinically meaningful (>1.5 times the MCID), but the difference between responders and non-responders was not statistically significant. Responders experienced a change of =5 points in the PedsQL Generic Core Total Scale Score compared with non-responders. A =10-point change in PedsQL Multidimensional Fatigue Total Scale Score was experienced by all responders (100%) and two non-responders (16.7%). LIVMARLI™ (maralixibat) oral solution is an orally administered, once-daily, ileal bile acid transporter (IBAT) inhibitor approved by the U.S. Food and Drug Administration for the treatment of cholestatic pruritus in patients with Alagille syndrome (ALGS) one year of age and older and is the only FDA-approved medication to treat cholestatic pruritus associated with Alagille syndrome. LIVMARLI is currently being evaluated in late-stage clinical studies in other rare cholestatic liver diseases including progressive familial intrahepatic cholestasis (PFIC) and biliary atresia. LIVMARLI has received Breakthrough Therapy designation for ALGS and PFIC type 2 and orphan designation for ALGS, PFIC and biliary atresia.