Lucid Diligence Brief: Mirum to acquire Bluejay Therapeutics

Professional audiences only. Not investment research or advice. UK readers: for persons under Article 19(5) or Article 49(2)(a)–(d) of the Financial Promotion Order 2005. Others should not act on this communication.

Dive deeper

Seven questions, 60-second thesis frame.

What changed, and when

Mirum announced on 08 Dec 2025 a definitive agreement to acquire Bluejay Therapeutics, adding worldwide rights to brelovitug for chronic hepatitis D, with top-line Phase 3 results expected in 2H 2026 (Business Wire press release).
Independent coverage reports $620 million upfront, split $250 million cash and $370 million stock, plus up to $200 million in potential sales-based milestones, alongside a ~$200 million concurrent private placement to fund development and launch preparations (Reuters, Fierce Biotech). Where figures differ, we privilege the company release for line-item terms and Reuters for the “up to $820 million” headline value.

60-second thesis frame

Mirum is buying a late-stage, potentially first-in-US therapy for a severe, underserved liver disease, a tight fit for its rare-liver commercial stack of LIVMARLI, CHOLBAM and CTEXLI and its existing hepatology KOL network (Business Wire press release). Brelovitug, a fully human anti-HBsAg monoclonal antibody, holds FDA Breakthrough Therapy and EMA PRIME designations and is in a global registrational AZURE program, including a head-to-head vs bulevirtide, which is approved in the EU but not in the US after an FDA CRL to Gilead in 2022 (Bluejay pipeline, AZURE-2 ClinicalTrials.gov, EMA Hepcludex page, Gilead CRL statement). Funding risk is partially offset by the ~$200 million private placement, but value still hinges on effect size at Week 48 combined virologic plus ALT response, regulatory acceptability, and competitive timing versus bulevirtide (Business Wire press release, Reuters).

The seven diligence questions

Clinical

Will AZURE replicate the Phase 2 signals, namely 100% HDV RNA response with up to ~82% combined virologic response plus ALT normalization at Week 48, and how durable is response off-therapy (Bluejay Phase 2 release, Nov 10, 2025)?
What is the immunogenicity profile and any impact of anti-drug antibodies on sustained response or safety with chronic subcutaneous dosing?

Payer or Access

How will US payers gate a rare infectious-disease therapy with limited HDV testing and specialist capacity, and will prior auth tie to HDV RNA positivity and HBV status in the absence of a US-approved comparator (Quest Diagnostics HDV RNA CPT page, Labcorp HDV RNA test directory)?
Are coding and lab pathways ready at scale for HDV RNA testing and ongoing monitoring in community hepatology, including CPT 87798 or 87523 as used by large reference labs (Quest Diagnostics HDV RNA CPT page, Quest Diagnostics HDV RNA quantitative CPT)?

Ops or Adoption

Can Mirum leverage its LIVMARLI, CHOLBAM and CTEXLI field infrastructure, distribution and patient-services platform to accelerate HDV launch readiness, including diagnostics pull-through (Business Wire press release)?

Competitive

If Gilead advances US resubmission for bulevirtide or expands EU use ahead of brelovitug’s launch, does a clear advantage emerge on efficacy, safety, convenience or durability, and how will guidelines reconcile mAb neutralization versus entry-inhibition (EMA Hepcludex page, Gilead CRL statement)?

Team or Cap table

What are integration and retention plans for Bluejay’s clinical leadership and key trial operations, and do milestone structures align incentives through Phase 3 delivery and launch (Business Wire press release, Reuters)?

Red flags

Phase 3 underperforms Phase 2 magnitude on the combined virologic plus ALT endpoint, weakening the expedited-review case in US and EU filings (Bluejay Phase 2 release).
US regulatory bar shifts toward durability off-treatment or clinical outcomes, extending timelines beyond the 2027 target (Business Wire press release).
Competitive erosion if bulevirtide secures US approval or shows superior real-world effectiveness, compressing unmet-need narrative and payer headroom (EMA Hepcludex page, Gilead CRL statement).

Next catalyst

Transaction close targeted Q1 2026, AZURE top-line readout in 2H 2026, with BLA submission and potential US launch in 2027 if successful, plus the 08 Dec 2025 investor call outlining next steps (Business Wire press release).

FAQ

What exactly changed by Mirum’s “definitive agreement to acquire Bluejay Therapeutics” news on 08 Dec 2025, and why does it matter for HDV?
Mirum agreed to buy Bluejay, adding late-stage brelovitug for chronic hepatitis D, a severe HBV coinfection with no FDA-approved therapies, and guided to 2H 2026 top-line data and a potential 2027 US launch (Business Wire press release, Reuters).
What is the regulatory path after the Mirum and Bluejay Therapeutics deal, and what are the next formal steps in the US, UK and EU?
Brelovitug holds FDA Breakthrough Therapy and EMA PRIME designations, and the global AZURE program is designed to support filings in the US and Europe; EU standard of care includes bulevirtide while the US has no approved HDV therapy following an FDA CRL to Gilead in 2022 (Bluejay pipeline, EMA Hepcludex page, Gilead CRL statement).
Which endpoints in Bluejay Therapeutics’ AZURE shape expectations, and what effect size matters?
AZURE’s primary endpoint is a composite of undetectable HDV RNA and ALT normalization at Week 48, with AZURE-2 providing a head-to-head versus bulevirtide, so replication of Phase 2’s 100% RNA response and ~82% combined endpoint would be viewed as clinically meaningful if durable (AZURE-2 ClinicalTrials.gov, Bluejay Phase 2 release).
What safety and tolerability issues matter post-announcement regarding Mirum’s acquisition of Bluejay Therapeutics, and do they affect real-world use?
Phase 2 described a favorable profile, with injection-site erythema most common, but immunogenicity and off-therapy durability remain watch points for a chronic antibody therapy; EU bulevirtide experience informs injection logistics and monitoring expectations (Business Wire press release, EMA Hepcludex page).
How will payers treat access after the news about Mirum and Bluejay Therapeutics, including prior auth or step edits, and are codes available?
Expect specialist initiation, lab-confirmed HDV RNA, and documentation of HBV coinfection at minimum, with practical gating driven by availability of HDV RNA assays and lab coverage using established CPT pathways at major reference labs (Quest Diagnostics HDV RNA CPT page, Labcorp HDV RNA test directory).

Publisher / Disclosure

Publisher: LucidQuest Ventures Ltd. Produced: 09 Dec 2025, 10:15 London. Purpose: general and impersonal information. Not investment research or advice, no offer or solicitation, no suitability assessment. UK: directed at investment professionals under Article 19(5) and certain high-net-worth entities under Article 49(2)(a)–(d) of the Financial Promotion Order 2005. Others should not act on this. Sources and accuracy: public sources believed reliable, provided “as is,” may change without notice. No duty to update. Past performance is not reliable. Forward-looking statements carry risks. Methodology: questions-first framework using public sources. No conflicts. Authors do not hold positions unless stated. © 2025 LucidQuest Ventures Ltd.

Entities / Keywords

Mirum Pharmaceuticals; Bluejay Therapeutics; brelovitug; BJT-778; chronic hepatitis D; HDV; HBV; HBsAg; AZURE-1; AZURE-2; NCT06907290; NCT07200908; Breakthrough Therapy; PRIME designation; Orphan designation; FDA; EMA; MHRA; Hepcludex; bulevirtide; Gilead Sciences; registrational readout; rare liver disease; maralixibat; LIVMARLI; CHOLBAM; CTEXLI; volixibat; private placement; M&A; payer access; clinical endpoints; ALT normalization; 2H 2026; Q1 2026 closing.

Find more Lucid Diligence Briefs here.

Reach out to info@lqventures.com for a customized / deeper-level analysis.