Why Is Mirum Pharmaceuticals Stock Gaining Monday?

On Monday, Mirum Pharmaceuticals, Inc. (NASDAQ:MIRM) reported topline results from its Phase 3 EXPAND study evaluating LIVMARLI (maralixibat) to treat cholestatic pruritus in individuals aged six months and older suffering from ultra-rare cholestatic liver conditions, including biliary atresia.

Following the announcement, the stock traded higher.

The clinical trial met its primary endpoint while demonstrating statistical significance across all five prespecified secondary measures, including three key outcomes in biliary atresia patients with a native liver.

Key Efficacy Findings From Phase 3 EXPAND Trial

The late-stage study evaluated 52 total participants and received either a twice-daily dose of maralixibat at 285 µg/kg or a placebo.

In the main pediatric analysis population, maralixibat generated a statistically significant reduction in itching compared to placebo.

Between Weeks 13 and 20, patients receiving maralixibat experienced a 1.81-point mean improvement from baseline in their average worst-daily ItchRO(Obs) severity score, compared to a 0.83-point improvement in the placebo group.

This outcome represents a placebo-adjusted treatment difference of 0.98 points (p=0.0004).

Furthermore, maralixibat drove a 70.1% baseline drop in total serum bile acids compared to 3.5% for placebo, achieving a 69.0% treatment effect.

Pediatric patients on maralixibat also achieved pruritus improvement on 86.0% of days versus 49.1% for placebo.

Promising Results In Biliary Atresia Subgroup

Among patients with biliary atresia retaining their native liver, maralixibat delivered substantial clinical improvements. Patients taking maralixibat achieved a 2.16-point reduction in severity score versus a 1.01-point drop for placebo, marking a 1.15-point difference.

These patients experienced pruritus relief on 96.4% of days compared to 52.2% for placebo (p=0.0045). Additionally, maralixibat achieved a 75.5% reduction in total serum bile acids compared to 9.0% for placebo.

Consistent Safety Profile Reported

Safety outcomes mirrored previous clinical trials, and researchers identified no new safety concerns.

Serious adverse events reported in the maralixibat cohort included pneumonia, pyrexia, large intestine infection, acute kidney injury, and viral infection with bronchiolitis, though none were deemed treatment-related.

Placebo group serious adverse events included pneumonia, pancytopenia, sepsis, forearm fracture, and cholangitis.

MIRM Price Action: Mirum Pharmaceuticals shares were up 2.31% at $88.00 during premarket trading on Monday, according to Benzinga Pro data.

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