What Biogen Inc. told the SEC could break it.

Two (unnamed) wholesale distributors each exceeded 10% of total revenue and together were ~43.9% of gross product revenue in 2025 (up from 39.3% and 36.9%), concentrating Biogen's distribution channel.

“Our product sales to two wholesale distributors each accounted for more than 10.0% of our total revenue for the years ended December 31, 2025, 2024 and 2023, and on a combined basis, accounted for approximately 43.9%, 39.3% and 36.9%, respectively, of our gross product revenue.”

The IRA lets CMS negotiate prices for select high-cost Medicare Part D drugs (from 2026) and Part B drugs (from 2028) and imposes inflation-rebate penalties, pressuring Biogen's pricing and manufacturer contributions.

“(i) allowing CMS to negotiate prices for select high-cost Medicare Part D drugs (beginning in 2026) and Part B drugs (beginning in 2028) to reduce out-of-pocket prescription drug costs for beneficiaries, potentially resulting in higher contributions from plans and manufacturers; (ii) drug inflationary rebate requirements to penalize manufacturers from raising the prices of Medicare covered single-source drugs and biologics beyond the inflation-adjusted rate”

Biogen relies on single-source providers for certain raw materials/manufacturing supplies and sources most fill-finish and all final product assembly/storage to a concentrated group of third-party CMOs; FDA approval of alternatives isn't assured.

“We rely on third-party suppliers and manufacturers for many aspects of our manufacturing process for our products and product candidates. In some cases, due to the unique manner in which our products are manufactured, we rely on single source providers of raw materials and manufacturing supplies.”

A large share of Biogen's revenue depends on partner collaborations — ~18.8% from Genentech (anti-CD20/OCREVUS royalties) plus the Eisai LEQEMBI 50/50 share and Roche-distributed products — exposing it to partners' commercialization and biosimilar entry.

“Approximately 18.8 %, 18.1 % and 17.2 % of our total revenue in 2025, 2024 and 2023, respectively, was derived from our collaboration arrangements with Genentech.”

Certain SKYCLARYS starting materials rely on a single China-based supplier; Biogen is working to mitigate tariff exposure across its network (though it doesn't expect a material 2026 impact at current tariff levels).

“Although certain starting materials for SKYCLARYS rely on a single supplier based in China, the manufacturing process, including active pharmaceutical ingredients and drug substance, is primarily conducted in the U.S. We are working to mitigate potential exposure from tariffs across our network.”