Regeneron Pharmaceuticals, Inc.

The full register, from 13F filings

The Register tab above is hand research: a dozen holders, each traced to the filing it came from. This asks the same question of the whole market for the quarter ended 31-mar-2026, where 1,373 managers reported a position. Broad where the research is deep, and shallow in the ways a 13F always is.

Built from 13F filings, which report US listed, long, US custodied positions only. A register from this source is a floor rather than a level: a holder's true position can be far larger, as BlackRock's ASML stake shows at 1.28m shares in a 13F against 26.3m in its 13G/A. Holdings held through derivatives, outside US custody, or below a manager's reporting obligation do not appear. Where a holder is marked as a family, its total sums several separate filing entities and describes something no single filing describes; the constituent entities and their share counts are listed so the total can be checked. That roll-up can legitimately exceed the family's own Schedule 13G, because a 13G is filed by one legal entity: Vanguard reports Alphabet through ten advisory entities, and The Vanguard Group Inc itself reported zero after its January 2026 disaggregation.

What a reader needs to know to read these numbers

• Regeneron has two classes of stock. Common Stock (par value $0.001, one vote per share): 101,137,842 shares outstanding as of 23 Jul 2026 per the Q2 2026 10-Q cover page; this is the denominator used for every pct_of_company in this file. Class A Stock (par value $0.001, ten votes per share, issued only to pre-IPO holders and non-transferable except to family/estate vehicles): 1,817,146 shares outstanding as of the same date. Class A is reported only in company.share_classes and in insider method_notes, and is never added into the common denominator or into any register row's shares/pct_of_company field, per project convention.
• As of 30 Jun 2026 (per the 10-Q), Class A holders as a group held 15.2% of the combined voting power of Common Stock and Class A Stock combined, even though Class A is under 2% of total share count, because of the 10-votes-per-share weighting. Dr. Leonard Schleifer (CEO, co-founder) alone beneficially owned approximately 31.3% of outstanding Common Stock assuming conversion of his Class A and exercise of in-the-money options; current executive officers and directors as a group beneficially owned 17.7% of combined voting power; and the CEO plus five other significant shareholders together held approximately 39.9% of combined voting power. This voting concentration, not any single register percentage, is the real governance story for Regeneron.
• Sanofi is a long-running strategic collaborator (global antibody collaboration covering Dupixent, Kevzara, and other programs) and was historically a very large equity holder under a 2014 Amended and Restated Investor Agreement, but its stake has been sold down for years. The last SEC ownership filing found, Schedule 13D Amendment No. 16 (filed 17 Jun 2020), put Sanofi's direct holding at only 279,766 shares (0.3%) even then. No Sanofi SC 13D/A or SC 13G/A on Regeneron appears in Regeneron's EDGAR filing feed after that date, and the 2026 DEF 14A's 5%-holder table (record date 14 Apr 2026) does not list Sanofi at all, confirming it remains a sub-5% holder. No current share count is sourceable, so the Sanofi register row carries shares: null rather than a six-year-stale number; see unknowns. The Investor Agreement (as amended) contractually caps Sanofi at 30% of Class A and Common Stock combined, which is a ceiling on the relationship, not evidence of current holding size.
• Regeneron's own equity investments are disclosed only as a combined, unnamed balance-sheet total in both the FY2025 10-K and the Q2 2026 10-Q: 'equity securities of publicly traded companies', part of Marketable Securities, was $34.3 million at 31 Dec 2025 and $177.9 million at 30 Jun 2026 (of which $114.0 million was subject to transfer restrictions expiring Dec 2026). Neither filing's Note 5 (Marketable Securities) or Note 6 (Fair Value Measurements) names a single company inside this balance, so per the brief's rule on combined balances no holding row is recorded for it here; the balance is reported in this note instead of being invented as a sized position.
• Regeneron's collaboration and license agreements with Sanofi (antibodies including Dupixent/Kevzara), Bayer (EYLEA), Intellia Therapeutics (CRISPR/Cas9 in vivo gene editing), Alnylam Pharmaceuticals (RNAi), and Hansoh are commercial partnerships, not equity stakes: none of the FY2025 10-K or Q2 2026 10-Q states that Regeneron purchased or holds shares of any of these companies. Searched terms 'equity method', 'unconsolidated', 'strategic investment', 'equity securities', 'non-marketable', 'joint venture', 'noncontrolling', 'Intellia', 'Alnylam', '2seventy', 'Checkmate' across both filings; only the collaboration-agreement language and the combined equity-securities balance above returned hits.
• Regeneron completed full acquisitions (100% ownership, now wholly-owned subsidiaries) of Checkmate Pharmaceuticals, Inc. (May 2022) and Decibel Therapeutics, Inc. (September 2023, confirmed via Regeneron's own Schedule 13D/A Amendment No. 1 on Decibel showing 100% ownership after a reverse merger). Per the brief, wholly-owned operating subsidiaries are excluded from holdings. In April 2024, Regeneron acquired full development and commercialization rights to 2seventy bio, Inc.'s oncology and autoimmune cell-therapy pipeline; this is described only as an asset/rights acquisition in both filings, with no statement that Regeneron purchased or holds 2seventy bio common stock, so it is not recorded as an equity holding either.
• Register uses each institutional manager's own Q2 2026 Form 13F-HR (period 30 Jun 2026), not the Q1 2026 (31 Mar 2026) REGN.json register snapshot, which was used only as a shopping list of which managers to look up.
• Vanguard Rule: Vanguard Group Inc (CIK 0000102909) filed Form 13F-NT (notice, no holdings) for the quarter ended 30 Jun 2026; its Regeneron position is instead reported by two successor entities, Vanguard Capital Management LLC and Vanguard Portfolio Management LLC, summed into one 'The Vanguard Group' row. This is the notice case.
• Capital Group: all three registrants (Capital World Investors, Capital International Investors, Capital Research Global Investors) were checked in their own Q2 2026 13F-HRs; only Capital World Investors currently holds Regeneron common. T. Rowe Price: both registrants (Associates and Investment Management, Inc.) were checked; only T. Rowe Price Associates currently holds Regeneron common, and its filing reports values in thousands (rescaled x1000 here; see that row's method_note).
• Thousands trap cross-check: implied price per share (value/shares) was computed for every institutional register row. All cluster tightly at approximately $623.55/share as of 30 Jun 2026 once T. Rowe Price Associates' raw filed value is rescaled x1000, confirming the rescale is correct and no other filer in this register uses the thousands convention.
• Self-gate check: summing every register row that is neither an aggregate container nor a rolled-up member with shares: null gives 17 institutional 13F rows (48,008,084 shares) plus 14 individually-named clean-common insiders (878,458 shares) = 48,886,542 shares against 101,137,842 shares outstanding, or 48.34%, within the brief's 15 to 55 percent tolerance band.