Annexon, Inc.
US ˙ NasdaqGS ˙ US03589W1027

SecurityANNX / Annexon, Inc.
InstitutionPolygon Management Ltd.
Latest Disclosed Ownership1,292,455 shares
Latest Disclosed Value $ 7,160,201
Polygon Management Ltd. reports 36.41% decrease in ownership of ANNX / Annexon, Inc.

On May 15, 2026 - Polygon Management Ltd. filed a 13F-HR form disclosing ownership of 1,292,455 shares of Annexon, Inc. (US:ANNX) valued at $7,160,201 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 17, 2026 disclosing 2,032,455 shares of Annexon, Inc.. This represents a change in shares of -36.41% during the quarter. The current value of the position is $7,043,880 USD.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-05-15 2026-03-31 13F ANNEXON COM 03589W102 1,292,455 -740,000 -36.41 7,160 -29.82 0.8799
2026-02-17 2025-12-31 13F ANNEXON COM 03589W102 2,032,455 -80,000 -3.79 10,203 58.37 2.1513
2025-11-14 2025-09-30 13F ANNEXON COM 03589W102 2,112,455 -697,545 -24.82 6,443 -4.48 0.8618
2025-08-14 2025-06-30 13F ANNEXON COM 03589W102 2,810,000 160,000 6.04 6,744 31.87 1.0864
2025-05-15 2025-03-31 13F ANNEXON COM 03589W102 2,650,000 1,250,000 89.29 5,114 -28.79 1.1672
2025-02-21 2024-12-31 13F/A-1 ANNEXON COM 03589W102 1,400,000 615,645 78.49 7,182 54.68 1.8348
2025-02-14 2024-12-31 13F ANNEXON COM 03589W102 1,400,000 615,645 7,182 1.6203
2024-11-14 2024-09-30 13F ANNEXON COM 03589W102 784,355 -473,630 -37.65 4,643 -24.68 1.3097
2024-08-14 2024-06-30 13F ANNEXON COM 03589W102 1,257,985 1,257,985 6,164 1.5375
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.