BIIB Q2: Growth Portfolio Overtakes MS, Leqembi Hits $184M

Biogen (BIIB) reported second-quarter 2026 revenue of $2.74 billion on July 29, up 3% year over year, with the Growth Portfolio generating $1.06 billion in revenue, up 24% YoY. For the first time, the Growth Portfolio exceeded the Legacy MS portfolio, which brought in $767 million and continues to decline. Shares closed at $205.61, up 2.73%.

The numbers

• Ticker: BIIB
• Stock price: $205.61 (close July 29, 2026)
• Q2 revenue: $2.74 billion (+3% YoY)
• Non-GAAP diluted EPS: $3.60
• Growth Portfolio revenue: $1.06 billion (+24% YoY)
• Legacy MS revenue: $767 million
• Leqembi global in-market sales: $184 million (+15% YoY; US $97 million)
• Syfovre: $97.4 million (first full quarter post-Apellis close)
• EMPAVELI: $30.4 million
• Spinraza: $204.3 million (+37% YoY, driven by high-dose regimen demand)
• Skyclarys: $82.3 million
• Zurzuvae: $70.7 million

Growth Portfolio crosses the line

The Growth Portfolio includes Leqembi, Spinraza, Skyclarys, Zurzuvae, Qalsody, Syfovre, and EMPAVELI. The Legacy MS portfolio (Tecfidera, Vumerity, Avonex, Plegridy, Tysabri) generated $767 million this quarter, down from $963 million a year ago, as generic competition erodes Tecfidera and Vumerity sales.

Leqembi’s $184 million in global in-market sales slightly missed the $186 million consensus but grew 15% YoY. The Leqembi subcutaneous Iqlik approval in July 2026 enables at-home initiation dosing, supporting continued sequential growth. US in-market sales were $97 million. Leqembi’s primary known safety concern is ARIA (amyloid-related imaging abnormalities), which occurred in 12.6 percent of patients in the CLARITY AD trial and requires MRI monitoring during treatment.

The Apellis acquisition, closed May 14 for $5.6 billion, contributed Syfovre ($97.4 million) and EMPAVELI ($30.4 million) to Specialized Immunology. These products added $30 million in revenue recognized since the close date.

Pipeline signals

Three pipeline moves were announced alongside earnings:

1. BIIB091 (BTK inhibitor): Phase 2 FUSION data in relapsing-remitting MS achieved proof of concept. Biogen will explore next steps. BIIB091 is a reversible, non-covalent oral BTK inhibitor that suppresses B-cell activation. Unlike B-cell-depleting therapies, BTK inhibition reduces activation while preserving B-cell viability, avoiding infection risk from chronic depletion.

2. Ionis ALS option exercise: Biogen exercised its option for a worldwide exclusive license to an oligonucleotide targeting stathmin-2 pre-mRNA in broad ALS. Stathmin-2 loss, driven by TDP-43 pathology, is implicated in ALS neurodegeneration.

3. RayThera acquisition: Biogen agreed to acquire private immunology company RayThera for up to $1 billion (upfront plus milestones) on June 17. The lead candidate enters Phase 1 in Q3 2026.

What to watch

Five registrational readouts are expected over the next four quarters. The highest-impact catalysts:

• Litifilimab in cutaneous lupus erythematosus (Phase 3 AMETHYST, data expected 2027, FDA Breakthrough Therapy designation). A separate SLE Phase 3 trial has results expected between 2026 and 2027.
• Felzartamab in antibody-mediated rejection in kidney transplant (Phase 3 TRANSCEND, first readout 2027).
• Zorevunersen in Dravet syndrome (Phase 3 EMPEROR, data mid-2027, rolling NDA submission planned for H1 2027).

The near-term risk is Apellis dilution: the acquisition is expected to have a $0.85 EPS impact in 2026 before turning accretive in 2027. GAAP diluted EPS was just $0.66 this quarter, weighed down by acquisition costs and IPR&D charges. Biogen updated its 2026 outlook to mid-single-digit revenue growth, up from a prior decline projection.

The competitive risk for BIIB091 is real: Novartis’s remibrutinib and Roche’s fenebrutinib are also oral BTK inhibitors in Phase 3 for MS, ahead of BIIB091. Biogen will need to differentiate on efficacy or safety to justify advancing to Phase 3.

What It Means for the Trade

The crossover line — Growth Portfolio revenue exceeding Legacy MS for the first time — is the single most important fact in this print, and it deserves more weight than the 2.73% stock move gave it. For a decade Biogen’s model has been “declining MS cash cow funding a transition,” and the model has now mechanically flipped: $1.06 billion growing 24% against $767 million declining roughly 20%. The transition is no longer a promise; it’s an accomplished fact on the revenue line. That changes the type of risk in the stock — the question is no longer whether the growth portfolio can scale fast enough, but whether the five registrational readouts over the next four quarters confirm the pipeline behind it.

Read the accounting noise separately from the operational reality. GAAP diluted EPS of $0.66 against non-GAAP $3.60 is the Apellis acquisition costs and IPR&D charges doing their worst quarter — the $0.85 2026 EPS dilution impact was guided and will turn accretive in 2027. The operational signals are better than the GAAP print: mid-single-digit revenue growth guidance is an upgrade from a prior decline projection, and Spinraza’s 37% growth on high-dose regimen demand is a franchise nobody had penciled in for growth. Syfovre at $97.4 million in its first full quarter post-close is the number that will decide whether Apellis was a $5.6 billion mistake or a reasonable buy — one quarter in, the trajectory is intact but unproven.

Pipeline and Catalyst Context

The five registrational readouts are the real reason to hold this stock through the transition. Rank them by market impact: litifilimab in cutaneous lupus (Phase 3 AMETHYST, Breakthrough-tagged, 2027) is the largest TAM — lupus is where the immunology spend is moving; zorevunersen in Dravet syndrome (Phase 3 EMPEROR, mid-2027 data with a rolling NDA in H1 2027) is the highest-probability near-term approval event in a rare disease with high unmet need; felzartamab in antibody-mediated kidney transplant rejection (TRANSCEND, 2027) is the differentiated immunology asset with no clean comparator. BIIB091’s Phase 2 FUSION proof-of-concept is a necessary-but-behind entry into the BTK race — remibrutinib and fenebrutinib are already in Phase 3 — which makes it an option on a differentiated safety profile rather than a franchise anchor.

The Ionis stathmin-2 option exercise and the RayThera acquisition (up to $1 billion, lead candidate in Phase 1 this quarter) are classic Biogen portfolio economics: optioned oligonucleotide science in ALS where the company has deep regulatory experience, plus an early immunology bet to deepen the bench behind litifilimab. Neither moves near-term numbers; both are content for the pipeline narrative the market will re-price only after AMETHYST and EMPEROR read out.

Risks and What Could Go Wrong

1. Leqembi’s $184 million print was a slight miss ($186 million consensus) — if the subcutaneous initiation launch doesn’t accelerate the uptake curve by Q4, the market starts questioning the franchise’s peak-sales math, and Leqembi is the anchor of the growth story.
2. Syfovre’s integration underdelivers: geographic atrophy is competitive and Apellis’s own launch had execution wobbles — Biogen inherits both the asset and the market dynamics.
3. The BTK race is already lost in sequencing: remibrutinib or fenebrutinib winning first with clean Phase 3 data makes BIIB091 a “why bother” candidate regardless of FUSION’s quality.
4. Litifilimab or EMPEROR misses: the growth portfolio crossover was built on commercialized products, but the next leg of the thesis needs the readouts to land — one miss in 2027 resets the multiple story.

Position read: BIIB at $205 is a show-me story with a de-risked floor — the growth portfolio crossover means the decline narrative is over, the pipeline gives five dated catalysts, and the GAAP noise is transitory. Accumulate on weakness into the 2027 readout window; the catalyst density does the work.

Biogen Q2 2026 press release | RayThera acquisition press release | Biogen diranersen CELIA tau analysis