BIOGEN INC.
boothcheck covers BIOGEN INC. (BIIB) but does not put one priced-in number on it: here the defensible answer is the evidence rather than a point estimate. boothcheck publishes no house fair value, target price, or buy/sell rating. Narrative composed July 25, 2026.
• The multiple sclerosis franchise that built this company is eroding on schedule rather than collapsing: TYSABRI revenue ⟦"decreased $49.6 million, from $1,715.0 million in 2024 to $1,665.4 million in 2025, or 2.9%, primarily due to increased competition in rest of world, including the impacts from a biosimilar entrant of TYSABRI in Europe."⟧ • Close to a fifth of revenue is a share of drugs Biogen does not sell, booked as its cut of pre-tax profits on RITUXAN, GAZYVA and LUNSUMIO plus a ⟦"gros
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971 institutional managers reported holding BIIB in 13F filings for the quarter ended 2026-03-31. Together they hold about 89% of the company; the top 10 hold 55%. 112 opened new positions that quarter. Held by Vanguard Group, BlackRock, PRIMECAP Management, among others. On the short side, 5.2M shares were sold short as of the 2026-06-15 count, about 4% of shares outstanding (5.7 days of typical volume to cover).
Quarterly 13F filings arrive up to 45 days after quarter end, so the picture is never current (filed through 2026-05-29). Nothing here is investment advice.
BIIB has cut its share count 1.7% over the past five years, spending $1.50B on repurchases. It pays no dividend.
Share counts are split-adjusted; repurchase totals are gross of share issuance. Nothing here is investment advice.
Open-market insider buys at BIIB over the trailing three years: 2024: 1 buy totaling $101k; 2025: 1 buy totaling $152k; 2026: 1 buy totaling $1k. 21 officers and directors are on file.
Code P open-market purchases from SEC Form 4 filings, non-derivative, excluding scheduled 10b5-1 plans. Nothing here is investment advice.
BIIB's recent reports: the day-one move, then what the following quarter actually did.
| report | day one | next quarter |
|---|---|---|
| 2023-02-16 | -6.1% | +6.9% |
| 2023-04-26 | -1.7% | -1.4% |
| 2023-07-26 | -4.2% | -2.9% |
| 2023-11-09 | -8.5% | +10.0% |
Day-one is the close-to-close move around the filing. Nothing here is investment advice.
BIIB's latest 8-K filings: 2026-07-29 (items 2.02, 9.01); 2026-07-01 (items 2.02); 2026-06-10 (items 5.07); 2026-05-14 (items 1.01, 2.01, 2.03, 7.01, 9.01); 2026-04-29 (items 2.02, 9.01).
Item codes are the SEC's own classification of what each report discloses. Dates link to the filing on EDGAR. Nothing here is investment advice.
Model solve date: 2026-Q2
Narrative composed: July 25, 2026
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For informational and research purposes only. Not investment advice. Not a recommendation to buy, sell, or hold any security. boothcheck is not a registered investment adviser. Past performance does not guarantee future results.