MIRM · Mirum Pharmaceuticals, Inc. · Stock research

Current Thesis

A commercial-stage rare-disease franchise that ran to an all-time high on best-in-class FOP data, then cooled roughly 9% into a confirmed Q2 print. The base business is compounding — Q1 2026 net product sales of $159.9M (+43% YoY), FY guide lifted to $660–680M — while three discrete regulatory binaries stack into 2H26: a zilurgisertib FOP PDUFA on 2026-09-26, brelovitug HDV Phase 3 topline, and a volixibat NDA. The wrinkle since the stock's early-July peak: sell-side has now caught up (six PT raises already banked), so the frictionless re-rating leg is largely behind it. The immediate gate is the 2026-07-30 earnings print, ahead of the September FOP decision. Theme state is MATURING, not accelerating.

Bullish and bearish views on Mirum Pharmaceuticals, Inc.

The model's bull view on Mirum Pharmaceuticals, Inc. (MIRM), in brief: Guidance raised, not just met. On the 2026-05-06 Q1 print, net product sales were $159.9M (+43% YoY vs $111.6M), Livmarli $113.8M and bile-acid medicines $46.1M; 2026 net-sales guide moved up to $660–680M against FY2025 revenue of ~$521M. Zilurgisertib FOP data is class-leading.… The bear view: The whole 2H26 is binary-stacked. PDUFA 2026-09-26, AZURE-1/AZURE-4 topline, and the volixibat NDA cluster into one window; any single disappointment re-rates a name up ~130% off its 52-week low of $50.25. Momentum is cooling into the print. Price fell from the 2026-07-02… Both cases follow in full.

Bull Case

• Guidance raised, not just met. On the 2026-05-06 Q1 print, net product sales were $159.9M (+43% YoY vs $111.6M), Livmarli $113.8M and bile-acid medicines $46.1M; 2026 net-sales guide moved up to $660–680M against FY2025 revenue of ~$521M.
• Zilurgisertib FOP data is class-leading. PROGRESS Phase 2 results (ENDO 2026, 2026-06-14) showed a 99.9% reduction in new heterotopic-ossification lesion volume, durable through Week 48. FDA granted Priority Review with a PDUFA of 2026-09-26; the NDA covers FOP patients aged 12 and older. FOP is ultra-rare (~300 U.S. patients) — orphan pricing, minimal competition.
• Brelovitug HDV is a de-risking second pillar. AZURE-1 Phase 3 enrollment and AZURE-4 screening are complete (announced July 2026), confirming 24-week topline data timing in 2H26. Phase 2b AZURE-1 hit its primary endpoint on 2026-04-27 (combined virologic response + ALT normalization at Week 24). Breakthrough Therapy designation supports the U.S. BLA these two studies underpin.
• Volixibat optionality. U.S. NDA targeted for H2 2026 in primary sclerosing cholangitis, extending the IBAT franchise beyond Livmarli.
• Sell-side confirmed the move. Six PT raises 2026-06-11 → 2026-07-07 (MS $150, RBC $148, Citizens $146, JPM $125, HC Wainwright $185) landed as price printed new highs.

Bear Case

• The whole 2H26 is binary-stacked. PDUFA 2026-09-26, AZURE-1/AZURE-4 topline, and the volixibat NDA cluster into one window; any single disappointment re-rates a name up ~130% off its 52-week low of $50.25.
• Momentum is cooling into the print. Price fell from the 2026-07-02 all-time high of $125.41 to $114.48 on 2026-07-22 (–2.2% that session); the early-July breakout has stalled rather than extended.
• The easy re-rating is spent. Six PT raises already banked means the narrative is public — further upside now needs fresh data, not analysts catching up.
• Acquisition accounting noise. The Bluejay deal drove a $726.3M in-process R&D charge and a Q1 net loss of $790.2M, or $(13.43)/share.
• Insider stance is neutral-to-soft. Early-July Form 4s show routine 10b5-1 sells (CEO ~20k, CFO ~5k) and 2026-07-13 inducement grants at a $122.13 strike — no insider buying to flag fresh conviction.
• FOP economics are shared with Incyte, so the headline approval's P&L contribution is split.

Setup & Price Structure

Price sits near $114–115 (2026-07-22), roughly 9% below the $125.41 all-time high (2026-07-02), inside a 52-week range of $50.25–$130.00; market cap is ~$5.7B. The breakout to new highs has stopped extending and the tape is digesting into earnings. The June breakout shelf near $100–105 is the structure that matters — holding it on a weekly basis keeps the uptrend alive; losing it voids the momentum leg. With the print 2026-07-30 and roughly three trading days out, buying ahead of it is a guidance coin-flip, not a setup. Cleaner entries are post-print confirmation of the $660–680M FY guide or a controlled pullback that holds the breakout base. Because the sell-side upgrade cycle that powers a first leg has largely fired, the correct stance into the print is to stand aside and let the binary resolve rather than chase a stalling tape.

Catalyst Calendar (next 30 days)

• (Beyond 30 days, flagged for sizing): 2026-09-26 zilurgisertib FOP PDUFA; 2H26 brelovitug AZURE-1/AZURE-4 24-week topline; H2 2026 volixibat NDA submission.

Elapsed catalysts

• 2026-07-30 — Q2 2026 earnings (confirmed). The read on Livmarli/PFIC demand and whether the $660–680M FY guide holds or is raised. Binary; ~3 trading days out — the dominant near-term event. (passed 10d ago)

What Would Change Our Mind

• A weekly close below $100 breaks the post-June breakout structure and voids the momentum leg. Secondary invalidations: a 2026-07-30 Q2 print that cuts the $660–680M FY guide, a zilurgisertib PDUFA setback near 2026-09-26, or an AZURE-1 Phase 3 topline miss in 2H26.
• On the upside, a post-print guide raise plus a reclaim of the $125 all-time high would re-accelerate the story and flip the theme back toward ACCELERATING.

Correlation Notes

• Incyte (INCY): zilurgisertib is licensed from Incyte and FOP economics are shared — INCY headlines around the 2026-09-26 PDUFA read as a same-direction tell.
• Small/mid-cap biotech beta (XBI): binary-event names amplify sector risk-on/off swings; a hostile biotech tape can drag MIRM independent of company news.
• HDV competitive read-through: Gilead's bulevirtide (ex-U.S.) and other HBV/HDV programs frame brelovitug's commercial opportunity and any read-across from competitor data.