Mirum Pharmaceuticals, Inc. (MIRM) experienced a steep 24-hour plunge of 18.07%, driven primarily by a post-market sell-off after the company reported disappointing second-quarter 2026 financial results.

The biopharmaceutical company reported a quarterly adjusted loss of $1.06 per share, which was substantially larger than the analyst consensus estimate of a loss of $0.68 per share. This net loss widened to $67.23 million compared to a $5.86 million loss in the same period last year, largely due to a significant increase in operating expenses to $218.78 million from $132.77 million. Although net product sales rose 37.9% to $176.24 million, beating estimates, the dramatic earnings miss and escalating costs alarmed investors.

The sell-off intensified in after-hours trading, with shares falling 15% following the earnings release, compounding negative intraday sentiment. The report also noted that despite the company raising its full-year 2026 net product sales guidance to $680-$700 million, the market fixated on the widening loss and the missed bottom-line expectations.