SCHEDULE 13D/A Filed 2026-06-09 Event 2026-06-05 SEC 0001104659-26-071942 →

Fairmount Funds Management LLC → Jade Biosciences, Inc. JBIO

Stake: 19.99% Shares: 14,069,494 CUSIP: 008064206 Class: Common Stock, $0.0001 par value per share

Item 4 — Purpose of Transaction

Not extracted from this filing — typically because it's an amendment (13D/A) and Item 4 is unchanged from the parent filing. Read the raw SEC filing →

Cross-References

Insider Activity (last 365d)

1 transaction

1 buys · 0 sales · 0 awards/exercises

Issuer Cluster

6 13D/G filings on this issuer

5 other filings besides this one

Filer Track Record

18 filings by this filer

17 other filings in the data moat

Short Interest · settle 2026-07-15

DTC 7.16

7,528,320 shares short · -7.6% vs prior

Institutional Consensus · 2025-12-31

Held by elite portfolio managers

1 holder · $8.62M

Point72 Asset Mgmt

Post-Filing Returns · since 2026-06-05 on JBIO

+1 day

0.0%

+5 days

0.0%

+30 days

0.0%

+60 days

—

+90 days

—

+180 days

—

Anchor price 22.45 on closest trading day on/after 2026-06-05. Source: Yahoo Finance daily adj_close (split + dividend adjusted).

Form 4 Insider Transactions · last 365d

Date	Insider	Role	Type	Shares	Price	Value
2026-06-25	Eisner Mark	director	Award	47,675	$21.81	$1.04M

Other 13D/G Filings on Jade Biosciences, Inc.

Filed	Form	Filer	Stake	Shares
2025-04-30	SCHEDULE	Atlas Venture Fund XII, L.P.	20.00%	51,406	view →
2025-04-30	SCHEDULE	RA CAPITAL MANAGEMENT, L.P.	4.10%	1,324,954	view →
2024-06-20	SC	RA CAPITAL MANAGEMENT, L.P.	—	—	view →
2024-02-20	SC	Sofinnova Venture Partners X, L.P.	—	—	view →
2022-07-20	SC	Atlas Venture Fund XII, L.P.	—	—	view →

Other Filings by Fairmount Funds Management LLC

Filed	Form	Issuer	Stake	Shares
2026-07-20	SCHEDULE 13D/A	Crescent Biopharma, Inc.	—	6,593,385	view →
2026-07-01	SCHEDULE 13D/A	ORUKA THERAPEUTICS, INC. ORKA	19.50%	14,553,895	view →
2026-06-23	SCHEDULE 13D/A	SPYRE THERAPEUTICS, INC. SYRE	—	8,835,440	view →
2026-06-23	SCHEDULE 13D/A	Apogee Therapeutics, Inc. APGE	9.99%	6,713,519	view →
2026-05-13	SCHEDULE 13D/A	Viridian Therapeutics, Inc.\DE VRDN	—	17,201,800	view →
2026-01-22	SCHEDULE	Apogee Therapeutics, Inc. APGE	9.99%	6,047,027	view →
2026-01-22	SCHEDULE	Cogent Biosciences, Inc. COGT	9.90%	16,261,918	view →
2025-10-14	SCHEDULE	Apogee Therapeutics, Inc. APGE	9.99%	5,776,881	view →
2025-09-15	SCHEDULE	Dianthus Therapeutics, Inc. /DE/ DNTH	9.90%	4,052,052	view →
2025-03-10	SCHEDULE	Oruka Therapeutics, Inc. ORKA	19.99%	8,511,824	view →
2024-04-01	SC	Dianthus Therapeutics, Inc. /DE/ DNTH	—	—	view →
2024-04-01	SC	Viridian Therapeutics, Inc.\DE VRDN	—	—	view →
2024-04-01	SC	Apogee Therapeutics, Inc. APGE	—	—	view →
2024-04-01	SC	Cogent Biosciences, Inc. COGT	—	—	view →
2023-12-11	SC	Spyre Therapeutics, Inc. SYRE	—	—	view →
2023-06-13	SC	Cogent Biosciences, Inc. COGT	—	—	view →
2021-09-23	SC	Viridian Therapeutics, Inc.\DE VRDN	—	—	view →

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