Biogen (BIIB) - Company Research

Last Updated: 19 August 2026

Biogen is a company in the middle of a controlled handover. Its legacy multiple sclerosis franchise — TECFIDERA, TYSABRI, AVONEX, PLEGRIDY and VUMERITY — still supplied 40.8 per cent of FY2025 revenue but is shrinking at a double-digit rate, and generic and biosimilar entrants have now reached even TYSABRI. Against that, management has been buying and building a replacement: the $5.6bn Apellis acquisition closed on 14 May 2026 and added SYFOVRE and EMPAVELI; the FDA approved a subcutaneous at-home LEQEMBI autoinjector on 13 July 2026; and a high-dose SPINRAZA regimen was cleared on 30 March 2026. Whether the new portfolio outruns the old decline is the whole question. This report sets out what the filings say, with every figure traced to a company release, a 10-K, a 10-Q or a regulator, and no analyst ratings or price targets anywhere in it.

1. Company Snapshot

Field	Value
Company	Biogen Inc.
Ticker / Exchange	BIIB / NASDAQ
Headquarters	Cambridge, Massachusetts, United States
Founded	1978 (as Biogen N.V.)
Sector	Biotechnology and Pharmaceuticals
CEO / Leadership	Christopher A. Viehbacher, President and Chief Executive Officer (since November 2022). Robin Kramer, Executive Vice President and Chief Financial Officer (since March 2025). Dr Priya Singhal, Executive Vice President and Head of Development.
Employees	Approximately 7,500 as of 31 December 2025, down roughly 105 on the prior year, following net headcount reductions of about 1,400 under the Fit for Growth programme. Excludes staff added with Apellis and RayThera in 2026.
Revenue (FY2025)	$9,890.6m, up 2.2 per cent on FY2024 — the first annual increase since 2019
Net income (FY2025)	$1,292.9m, GAAP diluted EPS $8.79; non-GAAP diluted EPS $15.28
Market cap	Approximately $31.4bn (19 August 2026)
Share price	$212.55 (18 August 2026 close)
Reportable segments	One. Biogen manages the business as a single operating segment and discloses revenue by product category.
Dividend	None. Biogen has never paid a dividend on the common stock and did not initiate one in 2025 or the first half of 2026.

2. Bull and Bear Case

Bull Case

• The growth portfolio has overtaken the legacy book: in Q2 2026 Biogen's stated growth portfolio — EMPAVELI, QALSODY, SKYCLARYS, SPINRAZA, SYFOVRE, VUMERITY, ZURZUVAE plus its 50 per cent LEQEMBI share — reached $1.06bn, up 24 per cent year on year, and is now larger than the legacy multiple sclerosis portfolio at $767m. FY2025 revenue rose for the first time since 2019.
• At-home LEQEMBI dosing removes a real adoption barrier: the FDA approved LEQEMBI IQLIK as an initiation dose on 13 July 2026, following approval of the maintenance dose in August 2025. It is the first and only anti-amyloid therapy anywhere that permits at-home dosing across the entire treatment course, using two 250mg injections of about 15 seconds each. The US launch is set for late August 2026.
• Apellis broadens the base into ophthalmology and nephrology: the acquisition closed on 14 May 2026 for roughly $5.6bn plus a contingent value right of up to $4 per share, adding SYFOVRE and EMPAVELI with $689m of combined 2025 net product revenue and a nephrology commercial platform. Management guides to at least $250m of run-rate synergies exiting 2027 and non-GAAP EPS accretion from 2027.
• A dense catalyst calendar with five registrational readouts inside four quarters: both litifilimab Phase 3 studies in systemic lupus read out by the end of 2026, felzartamab Phase 3 in antibody-mediated rejection and litifilimab in cutaneous lupus in the first half of 2027, and zorevunersen in Dravet syndrome in Q3 2027. Salanersen received FDA Breakthrough Therapy Designation for spinal muscular atrophy on 4 June 2026.

Bear Case

• Legacy erosion is severe and now reaching the last defended franchise: Q2 2026 multiple sclerosis product revenue of $963m fell 13 per cent year on year, with TECFIDERA down 53 per cent and PLEGRIDY down 20 per cent. Sandoz launched TYRUKO, the first US TYSABRI biosimilar, in November 2025 at roughly a 20 per cent discount, attacking a $1.67bn franchise that had been the stable part of the base.
• LEQEMBI's commercial ramp is modest relative to the thesis: global in-market sales of $184m in Q2 2026 annualise to roughly $736m after three years on the US market, and Biogen books only its 50 per cent share — $63.7m in the quarter. Uptake remains gated by amyloid confirmation testing, MRI monitoring for amyloid-related imaging abnormalities, ApoE genotyping and the CMS coverage-with-evidence-development registry.
• Earnings quality has deteriorated sharply: the Q2 2026 gap between GAAP diluted EPS of $0.66 and non-GAAP of $3.60 was $2.94 per share, comprising $200.6m of inventory step-up amortisation, $153.6m of intangible amortisation and $170.5m of restructuring. Reported FY2026 non-GAAP guidance was cut to $12.00 to $13.00 from $15.25 to $16.25, on roughly $3.00 of acquired in-process research charges and about $0.85 of Apellis financing dilution.
• The balance sheet is materially more levered and more intangible-heavy: total debt rose from $6.3bn at 31 December 2025 to about $8.1bn at 30 June 2026 while cash fell from $3.0bn to $1.29bn and marketable securities went to zero. Intangible assets of $13.52bn plus goodwill of $6.99bn now stand at $20.5bn against $18.8bn of total equity, so a SYFOVRE or felzartamab disappointment becomes a write-down event as well as a revenue event.

3. Business Segments

Biogen manages and reports the business as a single operating segment, so the table below sets out the disclosed revenue categories for FY2025 rather than reportable segments. Percentages are of total revenue of $9,890.6m. A seventh category, specialised immunology, was added from Q2 2026 following the Apellis acquisition and contributed $127.8m in that quarter.

Segment / category	% of revenue	What it is
Multiple Sclerosis product revenue	40.8% ($4,038.9m)	TECFIDERA, VUMERITY, AVONEX, PLEGRIDY, TYSABRI and FAMPYRA. The historic core of the company, now in structural decline from generic and biosimilar entry.
Rare Disease	21.8% ($2,154.2m)	SPINRAZA for spinal muscular atrophy ($1,546.8m), SKYCLARYS for Friedreich's ataxia ($520.5m) and QALSODY for SOD1-ALS ($86.9m).
Anti-CD20 equity income and royalties	18.8% ($1,860.6m)	Royalties on Roche's OCREVUS ($1,414.9m) plus Biogen's share of US pre-tax profit on RITUXAN, GAZYVA and LUNSUMIO ($420.2m). High-margin income Biogen does not control commercially.
Contract manufacturing, royalty and other	7.4% ($732.9m)	Third-party manufacturing at Biogen's biologics facilities, plus miscellaneous royalty streams.
Biosimilars	7.4% ($729.1m)	BENEPALI, IMRALDI, FLIXABI, BYOOVIZ and TOFIDENCE, sourced through the Samsung Bioepis relationship. Being wound down — US and Canadian rights transferred as of 31 December 2025.
Other product revenue	2.0% ($197.2m)	Principally ZURZUVAE for postpartum depression ($195.1m), plus residual ADUHELM and FUMADERM.
Alzheimer's collaboration revenue	1.8% ($177.7m)	Biogen's 50 per cent share of LEQEMBI net revenue and cost of sales under the Eisai collaboration. Up 197 per cent on FY2024's $59.9m.

4. Business Model and Moat

How it makes money. Biogen sells specialty biologics and small molecules into neurology, rare disease and now ophthalmology and nephrology, largely through specialty pharmacy and hospital channels rather than retail. A meaningful slice of profit is not sold by Biogen at all: 18.8 per cent of FY2025 revenue came from royalties and profit shares on anti-CD20 antibodies commercialised by Roche and Genentech, and the LEQEMBI line is a 50 per cent share of a collaboration in which Eisai leads development, regulatory strategy and final decision-making. That structure is capital-light on the way up and gives Biogen very little control on the way down.

Where the moat comes from. The durable advantage is regulatory and clinical rather than commercial. SPINRAZA, QALSODY and salanersen all depend on antisense oligonucleotide chemistry and intrathecal delivery expertise that took two decades to build. Rare-disease indications carry orphan exclusivity, small and identifiable prescriber bases, and payer dynamics that reward first movers. In Alzheimer's, the diagnostic and monitoring infrastructure that slows LEQEMBI's launch — amyloid confirmation, MRI surveillance, genotyping — is also a barrier to anyone arriving later.

Where the model is exposed. Biogen's central problem is that its highest-margin revenue is either eroding or not under its control. The multiple sclerosis book is being competed away product by product; the anti-CD20 royalty stream belongs to Roche; LEQEMBI is Eisai's to steer; and the biosimilars economics sit with Samsung Bioepis. The replacement portfolio — SYFOVRE, EMPAVELI, felzartamab, litifilimab — has largely been bought rather than discovered, which is why goodwill and intangibles have grown to exceed total equity.

Cost discipline. The Fit for Growth programme targeted roughly $1.0bn of gross operating expense savings with about $300m reinvested, for net savings of around $700m, achieved through a net headcount reduction of approximately 1,400. It is visible in the numbers: FY2025 GAAP research and development spend fell 10 per cent to $1,778.6m. For live pricing and technical context on the shares, see the ChartsView Live Charts page.

5. Financial Health

All figures below are taken from Biogen's quarterly earnings releases and Forms 10-K and 10-Q, cross-checked against the company's XBRL filings with the SEC. Biogen's financial year ends on 31 December.

Fiscal Year	Revenue ($m)	YoY %	GAAP EPS	Adjusted EPS	Dividend/share	Long-term debt (YE)
FY2021	10,981.7	-18.3%	$10.40	$19.22	$0.00	$6,274.0m
FY2022	10,173.4	-7.4%	$20.87	$17.67	$0.00	$6,281.0m
FY2023	9,835.6	-3.3%	$7.97	$14.72	$0.00	$6,788.2m
FY2024	9,675.9	-1.6%	$11.18	$16.47	$0.00	$4,547.2m
FY2025	9,890.6	+2.2%	$8.79	$15.28	$0.00	$6,286.8m

Adjusted EPS is Biogen's reported non-GAAP diluted earnings per share. Long-term debt is the non-current portion of notes payable at each year end, per the SEC XBRL tag LongTermDebt; a further $999.1m, $0m, $150.0m, $1,748.6m and $0m respectively sat in current liabilities at each of those dates. FY2022 GAAP EPS of $20.87 is flattered by a large one-off gain on the sale of Biogen's equity stake in the Samsung Bioepis joint venture.

Quarter / Half	Revenue	Adjusted EPS	GAAP EPS
Q2 2026 (to 30 Jun 2026)	$2,736.0m	$3.60	$0.66
Q1 2026 (to 31 Mar 2026)	$2,477.8m	$3.57	$2.15
Q4 2025 (to 31 Dec 2025)	$2,279.4m	$1.99	-$0.33
Q3 2025 (to 30 Sep 2025)	$2,534.7m	$4.81	$3.17
FY2025 total	$9,890.6m	$15.28	$8.79

Q2 2026 revenue includes SYFOVRE ($97.4m) and EMPAVELI ($30.4m) only from the 14 May 2026 Apellis completion date; on a full-quarter basis those products generated $162m and $46m respectively. Q4 2025 revenue is derived as FY2025 total less the three reported quarters and fell 7 per cent year on year.

Cash generation remains solid and is the counterweight to the earnings-quality complaints. Biogen produced operating cash flow of $2,204.6m in FY2025 against capital expenditure of only $153.8m, giving free cash flow of $2,050.8m — a 20.7 per cent free cash flow margin on revenue. Q2 2026 operating cash flow was $448.9m against $40.9m of capex. What has changed is the balance sheet: to fund Apellis, total debt rose to approximately $8.1bn at 30 June 2026 ($800m current plus $7,290m long-term), cash fell to $1,285.0m and marketable securities were run to zero, leaving net debt of roughly $6.8bn. First-half 2026 investing outflow was $4.05bn against a financing inflow of $1.25bn.

6. Valuation Metrics

Raw metrics, August 2026. Not opinions on whether the stock is cheap or expensive.

Metric	Value
Market cap	Approximately $31.4bn (share price $212.55 × 147,753,998 shares outstanding). Weighted average diluted shares in Q2 2026 were 148.7m.
Trailing P/E (GAAP)	Approximately 37.8x on trailing-twelve-month GAAP diluted earnings per share of $5.63 (Q3 2025 $3.17 + Q4 2025 -$0.33 + Q1 2026 $2.15 + Q2 2026 $0.66). On Biogen's own non-GAAP measure the same four quarters total $13.97, putting the shares on roughly 15.2x adjusted earnings — a gap of well over 2x that reflects acquisition accounting, inventory step-up and restructuring rather than operating performance.
P/E (forward)	Approximately 17.0x on the midpoint of Biogen's own FY2026 reported non-GAAP guidance of $12.00 to $13.00 per share, issued 29 July 2026. On the company's "underlying" guidance of $15.85 to $16.85, which excludes acquired in-process research charges and Apellis financing dilution, the multiple is approximately 13.0x.
P/S (TTM)	Approximately 3.1x (market cap $31.4bn / trailing-twelve-month revenue $10,027.9m, being Q3 2025 $2,534.7m + Q4 2025 $2,279.4m + Q1 2026 $2,477.8m + Q2 2026 $2,736.0m).
EV/EBITDA (TTM)	Approximately 11.4x (enterprise value $38.2bn / trailing-twelve-month EBITDA of approximately $3,359m). Cross-checked on an FY2025 basis: operating income of $2,469.0m plus depreciation and amortisation of $779.9m gives EBITDA of $3,248.9m and a multiple of approximately 11.8x. The FY2025 D&A figure is the SEC tag DepreciationDepletionAndAmortization and ties exactly to depreciation of $272.8m plus intangible amortisation of $507.1m.
P/FCF	Approximately 15.3x on an FY2025 basis (market cap $31.4bn / free cash flow $2,050.8m; FCF = operating cash flow $2,204.6m less capital expenditure $153.8m per the FY2025 cash flow statement). Biogen's capital intensity is unusually low for a large biologics manufacturer, at about 1.6 per cent of revenue.
Enterprise value	Approximately $38.2bn (market cap $31.4bn + total debt $8,090m − cash and equivalents $1,285m; marketable securities were nil at 30 June 2026, having been liquidated to help fund the Apellis acquisition).
52-week high	$219.72
52-week low	$131.52
Short interest (% of float)	Approximately 3.9 to 4.1 per cent. MarketBeat reports 5,723,194 shares short at the 30 June 2026 settlement, or 3.89 per cent of float, up 10.3 per cent from the 15 June reading. Yahoo Finance shows 5,453,901 shares and 4.11 per cent. Short interest has risen roughly 50 per cent from its March 2026 trough of 3.83m shares.
Days to cover	Approximately 3.8 to 4.1 days, on average daily volume of roughly 1.27m to 1.42m shares.

7. What Are They Building

Biogen spent $1,778.6m on research and development in FY2025 on a GAAP basis, down 10 per cent, and $1,730.5m on a non-GAAP basis, down 7 per cent, with the reduction attributed primarily to Fit for Growth and to Royalty Pharma research funding. Separately, acquired in-process research and development, upfront and milestone expense was $471.8m in FY2025 against $61.5m in FY2024, and is guided at $290m to $320m in Q3 2026 alone. Management describes five registrational readouts arriving within four quarters and ten further potentially registrational studies over four years.

Lupus and immunology. Litifilimab is the nearest large catalyst, with both Phase 3 systemic lupus studies due to read out by the end of 2026 and the cutaneous lupus study in the first half of 2027; the FDA granted Breakthrough Therapy Designation in the cutaneous indication in February 2026. Felzartamab, acquired with HI-Bio, is in Phase 3 for antibody-mediated rejection in kidney transplant with a first-half 2027 readout, and a Phase 2 in Graves' disease is planned; Greater China rights were licensed to TJ Biopharma on 20 April 2026. Partner UCB published positive Phase 3 results for dapirolizumab pegol in systemic lupus in The Lancet on 1 June 2026.

Neuromuscular and rare disease. Salanersen received FDA Breakthrough Therapy Designation for spinal muscular atrophy on 4 June 2026, with Phase 1b data expected in Q3 2026, and additional data presented in March 2026 showed new motor milestones in children previously treated with gene therapy. Zorevunersen, partnered with Stoke Therapeutics, is in Phase 3 for Dravet syndrome with a Q3 2027 readout.

Alzheimer's. Diranersen, previously BIIB080, is a tau-targeting antisense oligonucleotide. Its Phase 2 CELIA study read out on 14 May 2026 and missed its primary endpoint of dose-response on change in CDR-SB, but the 60mg arm slowed decline by 0.54 points, or 26 per cent, on CDR-SB with supportive results on ADAS-Cog13, MMSE and modified iADRS and robust reductions in cerebrospinal fluid tau and tau-PET signal. Biogen is proceeding to Phase 3. On LEQEMBI itself, lecanemab is now approved in 53 countries, intravenous maintenance dosing is cleared in eight including the United States, China and the United Kingdom, and subcutaneous filings are pending in Japan and China.

Discontinued. BIIB122, the LRRK2 inhibitor partnered with Denali, failed its Phase 2b LUMA study in early-stage Parkinson's disease and development in idiopathic Parkinson's was discontinued in May 2026. Denali continues the Phase 2a BEACON study in carriers of a pathogenic LRRK2 variant independently. Biogen also added RayThera on 6 August 2026, a small-molecule immunology company whose lead asset entered Phase 1 in July 2026, for up to $1bn largely contingent on milestones.

8. Competitive Landscape

Biogen competes on two distinct fronts: against Eli Lilly in Alzheimer's, where Kisunla is the direct rival to LEQEMBI, and against a broad set of large-cap biopharma companies for the specialty and rare-disease franchises it is building. Eisai appears here as both partner and lead party on lecanemab. Market capitalisations below were retrieved live on 19 August 2026.

Peer	Market cap (August 2026)	Key 2025 metric
Eli Lilly and Company (LLY)	$1,093.0bn	FY2025 revenue of $65.18bn with net income of $20.64bn. Markets Kisunla (donanemab), the principal competitor to LEQEMBI in early symptomatic Alzheimer's disease.
Roche Holding AG (RHHBY)	$354.0bn	FY2025 group sales of CHF 63,356m. Controls OCREVUS, on which Biogen earned $1,414.9m of royalties in FY2025, and is developing trontinemab in Alzheimer's after discontinuing gantenerumab.
Novartis AG (NVS)	$293.8bn	FY2025 revenue of $56.67bn with net income of $13.98bn. Markets Zolgensma, a direct competitor to SPINRAZA in spinal muscular atrophy.
Amgen Inc. (AMGN)	$230.1bn	FY2025 revenue of $36.75bn with net income of $7.71bn. A direct competitor in biosimilars and large-molecule specialty medicine.
Vertex Pharmaceuticals Incorporated (VRTX)	$133.9bn	FY2025 revenue of $12.00bn with net income of $3.95bn. The clearest comparator for a rare-disease-led specialty model at scale.
Eisai Co., Ltd. (4523.T)	¥1,359.2bn	Revenue of ¥825.4bn for the year ended 31 March 2026. Lead partner on lecanemab with final decision-making authority, forecasting ¥143.5bn of LEQEMBI revenue for the year to March 2027, up 63 per cent.

9. Insider Activity

Christopher Viehbacher has been President and Chief Executive Officer since November 2022 and was quoted by name in the Q2 2026 results release on 29 July 2026. The pattern in Biogen's Form 4 filings over the past twelve months is a quiet one: there has been effectively no meaningful open-market insider buying, and the selling that has occurred is small in absolute terms, totalling under $1.3m across the transactions below. Routine tax-withholding and option-award rows, which dominate the filing history, are excluded. The Chief Executive's own 2026 activity — a 38,015-share option award on 13 February and an exercise of 24,461 shares on 6 February with 10,980 withheld for tax — is compensation rather than discretionary dealing.

Name	Date	Type	Shares	Price	Value	Plan Type
Lloyd Minor (Director)	04 Aug 2026	Sale	593	$200.96	$119,169	Rule 10b5-1 plan
Lloyd Minor (Director)	03 Aug 2026	Sale	593	$203.34	$120,581	Rule 10b5-1 plan
Nicole Murphy (Head of Pharmaceutical Operations and Technology)	12 Feb 2026	Purchase	3	$195.03	$585	Not stated, de minimis
Priya Singhal (Head of Development)	09 Feb 2026	Sale	2,660	$199.83	$531,548	Not stated
Priya Singhal (Head of Development)	02 Feb 2026	Sale	748	$179.30	$134,116	Not stated
Priya Singhal (Head of Development)	29 Aug 2025	Sale	517	$133.55	$69,045	Not stated
Rachid Izzar (Head of Global Product Strategy)	08 Jul 2025	Sale	2,223	$135.00	$300,105	Not stated

Biogen's share repurchase authorisation from October 2020 had approximately $2.1bn remaining at 31 December 2025, but treasury stock was unchanged at $2,977.1m at 31 December 2024, 31 December 2025 and 30 June 2026 — meaning effectively nothing was repurchased in 2025 or the first half of 2026. Capital went to acquisitions and debt service instead.

10. Key Risks

• Legacy multiple sclerosis erosion: Q2 2026 MS product revenue of $963m fell 13 per cent year on year, and MS was still 40.8 per cent of FY2025 revenue. TECFIDERA has faced US generics since August 2020 and fell 53 per cent year on year in Q2 2026. Sandoz launched the first US TYSABRI biosimilar in November 2025 at roughly a 20 per cent discount, putting a $1.67bn franchise into the same trajectory.
• SPINRAZA competition: FY2025 revenue of $1,546.8m was broadly flat to down and Q4 2025 fell 15 per cent year on year, against Roche's Evrysdi and Novartis's Zolgensma. The high-dose regimen approved on 30 March 2026 is the principal defence and is only two quarters into its conversion, so the durability of that fix is unproven.
• LEQEMBI safety and label risk: lecanemab carries a boxed warning for amyloid-related imaging abnormalities, with symptomatic ARIA in 3 per cent of patients, serious ARIA in 0.7 per cent, and intracerebral haemorrhage greater than 1cm in 0.7 per cent against 0.1 per cent on placebo, including fatal cases. ApoE e4 homozygotes, roughly 15 per cent of Alzheimer's patients, show ARIA rates of about 45 per cent. Any post-marketing signal arising from unsupervised at-home subcutaneous dosing would be material given the IQLIK launch is imminent.
• Intangible and goodwill impairment exposure: intangible assets of $13.52bn and goodwill of $6.99bn at 30 June 2026 total $20.5bn against total equity of $18.8bn. FY2025 already carried $11.4m of intangible impairment plus a $52.9m right-of-use asset impairment on the inherited Reata lease in Plano, Texas, and FY2024 carried $60.2m of acquired-intangible impairment. A clinical or commercial setback at SYFOVRE or felzartamab becomes a write-down as well as a revenue miss.
• Leverage and financing cost: total debt roughly tripled relative to net cash position in six months, from $6.3bn of debt against $3.0bn of cash and $1.24bn of securities at 31 December 2025, to about $8.1bn of debt against $1.29bn of cash and nil securities at 30 June 2026. Q2 2026 non-GAAP other expense rose to $60m driven primarily by net interest, and Apellis financing accounts for roughly $0.85 of FY2026 EPS dilution. $800m of notes payable now sits in current liabilities.
• Dependence on partners Biogen does not control: Eisai holds final decision-making authority over lecanemab; Roche and Genentech control OCREVUS, whose royalties were 14.3 per cent of FY2025 revenue and are the fastest-growing large line in the accounts; Samsung Bioepis controls the biosimilars economics, to which Biogen paid $219m of profit-sharing expense in FY2025; and Supernus co-commercialises ZURZUVAE.
• Pipeline attrition: two of Biogen's three highest-profile 2026 readouts disappointed. The diranersen CELIA study missed its primary endpoint on 14 May 2026, and BIIB122 failed the Phase 2b LUMA study and was discontinued in idiopathic Parkinson's disease in May 2026. The litifilimab Phase 3 lupus readouts due by the end of 2026 are correspondingly higher stakes.
• Litigation: on 30 September 2025 the US District Court for the Northern District of California ordered Biogen to pay Genentech $88,348,123 in unpaid Cabilly-patent royalties, with a further $35,903,701 of interest stipulated on 3 October 2025. This flowed through FY2025 as a $104.8m GAAP cost-of-sales charge plus $131.0m within GAAP other expense, roughly $236m in total.

11. Recent Developments

• 06 Feb 2026 — Q4 and full year 2025 results beat guidance but Q4 was weak. FY2025 revenue of $9,890.6m rose 2.2 per cent and non-GAAP EPS of $15.28 exceeded the $14.50 to $15.00 guidance range, but Q4 revenue fell 7 per cent and Q4 GAAP EPS was negative $0.33. Initial FY2026 guidance called for a mid-single-digit revenue decline.
• 30 Mar 2026 — FDA approves the high-dose SPINRAZA regimen. This followed an earlier FDA rejection and is the key defence of a $1.5bn franchise. Conversion has since been described by management as running ahead of company expectations in all launched geographies.
• 31 Mar 2026 — Biogen agrees to acquire Apellis Pharmaceuticals. $41 per share in cash, roughly $5.6bn, plus a contingent value right of up to $4 per share tied to SYFOVRE sales thresholds. Adds SYFOVRE in geographic atrophy and EMPAVELI in paroxysmal nocturnal haemoglobinuria and C3 glomerulopathy, with $689m of combined 2025 net product revenue.
• 14 May 2026 — Diranersen Phase 2 CELIA results miss the primary endpoint. The tau antisense oligonucleotide failed on dose-response in CDR-SB change from baseline, but the 60mg arm slowed decline by 26 per cent on CDR-SB with supportive secondary results and clear tau-pathology reduction. Biogen is advancing to Phase 3 regardless.
• 14 May 2026 — Apellis acquisition completes. 105,687,831 shares, or 82.4 per cent, were tendered; the merger closed under DGCL section 251(h) and Apellis was delisted from Nasdaq.
• 21 May 2026 — BIIB122 discontinued in idiopathic Parkinson's disease. The Phase 2b LUMA study of the LRRK2 inhibitor, partnered with Denali Therapeutics and enrolling 648 patients, missed both its primary and secondary endpoints and did not slow disease progression versus placebo. Denali continues the Phase 2a BEACON study in LRRK2 variant carriers independently.
• 04 Jun 2026 — Salanersen receives FDA Breakthrough Therapy Designation in spinal muscular atrophy, following March 2026 data showing new motor milestones in children previously treated with gene therapy.
• 17 Jun 2026 — Biogen agrees to acquire RayThera. Up to $1bn, predominantly contingent on clinical and regulatory milestones, adding multiple small-molecule immunology programmes. The transaction completed on 6 August 2026.
• 13 Jul 2026 — FDA approves LEQEMBI IQLIK as an initiation dose. The regimen is 500mg once weekly as two 250mg subcutaneous injections of roughly 15 seconds each, and patients may switch between intravenous and subcutaneous at any point. It is the first anti-amyloid therapy anywhere permitting at-home dosing across the entire treatment course. US launch is set for late August 2026.
• 14 Jul 2026 — Real-world LEADER study presented at AAIC. More than 75 per cent of early Alzheimer's patients remained stable and approximately 7 per cent improved over an average of 17 months of LEQEMBI treatment. Subcutaneous autoinjector data showed efficacy and safety similar to intravenous dosing.
• 29 Jul 2026 — Q2 2026 results raise revenue guidance but cut reported EPS guidance. Revenue of $2,736.0m rose 3 per cent and the growth portfolio reached $1.06bn, up 24 per cent and now larger than legacy MS. FY2026 revenue guidance moved from a mid-single-digit decline to a mid-single-digit increase and underlying EPS guidance rose $0.60 to $15.85 to $16.85, but reported guidance fell to $12.00 to $13.00 on roughly $3.00 of acquired in-process research charges and $0.85 of Apellis dilution. Biogen also announced Phase 2 proof of concept for BIIB091 in relapsing-remitting multiple sclerosis.
• 06 Aug 2026 — RayThera acquisition completes. The lead asset had entered Phase 1 in July 2026.

12. Key Dates and Catalysts

• Expected August 2026 — US commercial launch of the LEQEMBI IQLIK initiation dose through specialty pharmacy, guided by the company to late August 2026.
• Expected September 2026 — Phase 1b salanersen data in spinal muscular atrophy, guided to Q3 2026.
• Expected September 2026 — the guided $290m to $320m of acquired in-process research and milestone expense, worth roughly $1.75 to $1.95 per share, lands in Q3 2026 reported earnings.
• Expected October 2026 — Q3 2026 results. Biogen's investor relations events page listed no upcoming events as of 19 August 2026. Precedent: Q3 2025 was reported on 30 October 2025 and Q2 2026 on 29 July 2026. Track confirmed release dates on the ChartsView Economic Calendar.
• Expected December 2026 — registrational Phase 3 readouts from both litifilimab studies in systemic lupus erythematosus. This is the single largest binary event on the four-quarter calendar.
• Expected June 2027 — Phase 3 felzartamab readout in antibody-mediated rejection, and Phase 3 litifilimab readout in cutaneous lupus erythematosus, both guided to the first half of 2027.
• Expected September 2027 — Phase 3 zorevunersen readout in Dravet syndrome, guided to Q3 2027.
• Expected December 2027 — Apellis run-rate synergies of at least $250m to be achieved exiting 2027, with the acquisition guided to be accretive to non-GAAP earnings per share in that year.

No PDUFA dates are currently outstanding: the two 2026 action dates, on high-dose SPINRAZA and the LEQEMBI IQLIK initiation dose, resolved in approval on 30 March and 13 July 2026 respectively. Subcutaneous lecanemab filings are pending in Japan and China with no disclosed action dates. No investor day is scheduled. Readers comparing notes on biopharma names can do so in the ChartsView Forum.

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