Mirum Pharma (MIRM) Q4 2025 earnings review
Massive Revenue Beat, But Unprofitability Returns Amid Spending Spike
Mirum Pharmaceuticals concluded a transformational 2025 by obliterating its own revenue guidance. The company posted FY25 net product sales of $521.3M, easily beating the $500-$510M target set in Q3. Q4 revenue accelerated to $148.9M (+50% YoY), driven by LIVMARLI's relentless 69% annual growth. However, management's narrative of 'financial discipline' is contradicted by the bottom line: after achieving its first-ever GAAP profit in Q3 ($2.9M), Mirum suffered a reversing trend in Q4, slipping back to a $5.7M net loss due to a sudden 18% sequential surge in operating expenses. Looking ahead, FY26 revenue guidance of $640M (midpoint) implies a sharp growth deceleration, shifting investor focus to the newly acquired Bluejay Therapeutics pipeline to justify the soaring valuation.
🐂 Bull Case
LIVMARLI FY25 sales hit $360.0M, growing an impressive 69% YoY. The expansion into PFIC and robust international launches have turned this into a reliable, high-margin cash engine.
The Bluejay Therapeutics acquisition brings brelovitug into the fold. Mirum now boasts four potentially registrational clinical readouts in the next 18 months, heavily de-risking the pipeline dependency on volixibat.
🐻 Bear Case
Q3's GAAP profitability was a mirage. Q4 operating expenses spiked sequentially by over $23M, dragging the company back into the red. Integration costs for Bluejay will likely pressure 2026 margins further.
FY25 revenue grew a blistering 55% YoY. FY26 guidance ($630M-$650M) implies only ~23% YoY growth, signaling that the easiest U.S. Alagille syndrome market share has already been captured.
⚖️ Verdict: 🟢
Bullish. While the return to unprofitability and decelerating FY26 growth rate require monitoring, Mirum is successfully transitioning from a single-product success story into a diversified, global rare-disease powerhouse. The January 2026 acquisition of Bluejay Therapeutics perfectly times a pipeline expansion just as LIVMARLI's base growth begins to normalize.
Key Themes
LIVMARLI Outperformance Continues
LIVMARLI remains the undisputed growth engine. Q4 sales hit an estimated $106M, capping off a year that saw 69% YoY growth to $360M. The U.S. market accounted for 68% of these sales ($244.7M), but international expansion is accelerating. The successful U.S. rollout of the new single-tablet formulation and expanding penetration in Progressive Familial Intrahepatic Cholestasis (PFIC) are stabilizing long-term demand.
Financial 'Discipline' Narrative Contradicted by Q4 Spend
Management explicitly touted 'sustained financial strength and capital discipline' in their release. However, the data contradicts this: Total Operating Expenses in Q4 spiked to $153.5M (a reversing trend vs Q3's $130.4M). SG&A alone jumped 20% sequentially to $74.1M. This spending surge entirely erased the operating leverage gained earlier in the year, throwing the company back into a $5.7M net loss and proving that GAAP profitability is not yet sustainable.
Bluejay Acquisition & Brelovitug Innovation
The recently completed acquisition of Bluejay Therapeutics transforms Mirum's pipeline. It brings brelovitug, a pan-genotypic, fully human IgG1 monoclonal antibody targeting anti-HBsAg for Hepatitis Delta Virus (HDV). This represents a major technological step beyond Mirum's traditional IBAT inhibitors. Brelovitug is designed to physically neutralize HDV/HBV virions, and Phase 2 studies showed a 100% HDV RNA response. With Phase 3 (AZURE-1) topline data expected in H2 2026, Mirum has secured a critical, high-value catalyst.
Revenue Growth is Decelerating
The law of large numbers is catching up to Mirum. After delivering a phenomenal 55% YoY total revenue growth in FY25 (and 87% in FY24), management's FY26 guidance of $630M-$650M projects a decelerating growth rate of ~23%. While 23% is healthy for a scaling biopharma, it indicates that the hyper-growth phase of the initial U.S. Alagille rollout is maturing. Future upside must increasingly come from pipeline conversions rather than existing commercial asset beats.
Bile Acid Portfolio Provides Stable Cash Floor
Often overshadowed by LIVMARLI, the Bile Acid Portfolio (CHOLBAM and CTEXLI) continues to perform as a reliable, stable asset. FY25 sales reached $161.3M, accelerating 31% YoY from FY24's $123.1M. The FDA approval of CTEXLI for CTX in early 2025 successfully translated into steady commercial adoption, providing vital non-dilutive cash flow to fund the R&D pipeline.
Other KPIs
A fortress balance sheet. Cash and equivalents grew by nearly $100M YoY. Furthermore, this figure is pre-acquisition; Mirum completed two private placements totaling $268.5M in gross proceeds in January 2026 to fund the Bluejay acquisition, ensuring the company has immense runway to execute its four Phase 3 readouts without near-term dilution anxiety.
Up from $79.4M in FY24. While Mirum frequently touts its 'operating cash flow positive' status, the reality of its GAAP profitability is heavily masked by aggressive equity issuance to employees. Total SBC specifically hit $71.4M for the year.
Guidance
Decelerating. The midpoint of $640M implies a 22.7% YoY growth rate, roughly half the 55% growth achieved in FY25. This sets a highly achievable, arguably conservative baseline that allows management room to beat and raise throughout 2026, a tactic they successfully employed throughout 2025.
Key Questions
The Q4 OpEx Spike
Total operating expenses jumped by $23M sequentially in Q4. How much of this surge was structural versus one-time costs associated with preparing for the Bluejay Therapeutics acquisition?
LIVMARLI Growth Composition
With FY26 top-line growth decelerating to ~23%, what is the assumed mix of US vs International growth, and are you seeing any signs of market saturation in the US Alagille segment?
Integration Risks and Synergies
Following the January 2026 close of the Bluejay acquisition, what are the expected impacts to the R&D and SG&A run rates for 2026 as you absorb the AZURE-1 and AZURE-4 clinical programs?