EcoR1 Capital, LLC

Registered adviser

CIK

1587114

Location

San Francisco, CA

Portfolio Value

Mid $2,056,733,752

Diversification

Moderately concentrated

Filing Date

Global Rank

#1,566 / 8,825 ▼ 235

Top Industry

Biotechnology 96.1%

Period ended 4 months ago

Filed Aug 14, 2026 · 3mo

26 quarters · since Mar 2020

Regulatory profile

From Form ADV, the SEC filer profile, 13D/13G type codes and N-CEN, never from the name.

Holder type

Registered adviser

Form ADV roster, Nov 1, 2026

Form ADV adviser

CRD 167121

Roster of Nov 1, 2026

Regulatory AUM

$3,424,668,843

Main clients

Pooled investment vehicles (100% of AUM)

Private funds

3 funds · Hedge funds

Focus by fund count, roster of Nov 1, 2026

$3,424,668,843 gross assets

LEI

254900G27UH5KKYMY240

Private funds on Schedule D 7.B.(1)

As filed Oct 18, 2024; SEC's bulk Form ADV archive ends with 2024 filings.

$5,001,741,441 gross assets in 3 funds Hedge funds $4,916,469,779 (2) Venture capital funds $85,271,662 (1)

Form ADV history

Monthly rosters from Dec 2019; each row is a run with the same figures, newest first.

Rosters	Regulatory AUM	Main clients
Apr 2026 to Nov 2026	$3,424,668,843	Pooled investment vehicles (100%)
Apr 2025 to Mar 2026	$3,914,180,012	Pooled investment vehicles (100%)
Apr 2024 to Mar 2025	$5,001,741,440	Pooled investment vehicles (100%)
May 2023 to Mar 2024	$4,711,772,578	Pooled investment vehicles (100%)
Apr 2023	$4,711,772,578	Pooled investment vehicles (100%)
Apr 2022 to Mar 2023	$4,439,985,676	Pooled investment vehicles (100%)

3 earlier changes not shown.

Schedule 13D/13G stakes

Stakes of 5% or more disclosed on Schedule 13D or 13G, each on the filer's latest filing for the security. These are event-dated stakes, not the quarter-end 13F portfolio below.

Company	Schedule	Event date	Filed	Shares	% of class	Change	Status
ANRO Alto Neuroscience, Inc.	13G	Jul 13, 2026	4mo	2,232,000	5.8%	—	Current
FULC Fulcrum Therapeutics, Inc.	13G	Jun 17, 2026	4mo	6,000,000	9%	—	Current
ELOX Eloxx Pharmaceuticals, Inc.	13G	Jun 9, 2026	5mo	403,586	9.9%	—	Current
ATRA Atara Biotherapeutics, Inc.	13G/A	May 7, 2026	6mo	1,552,000	17.4%	+836,147 since Sep 30, 2025	Current
TRAX First Tracks Biotherapeutics, Inc.	13G	Apr 20, 2026	7mo	3,174,519	9.1%	—	Current
AKTS Aktis Oncology, Inc.	13D Passive investment	Jan 12, 2026	10mo	4,824,469	9.1%	—	Current
ZYME Zymeworks Inc.	13D/A Passive investment	Nov 16, 2025	12mo	22,970,388	30.7%	0 since Jun 26, 2025	Current
NGNE Neurogene Inc.	13G/A	Sep 30, 2025	12mo	1,442,902	9.9%	+1,122,360 since Dec 18, 2023	Current
ORIC Oric Pharmaceuticals, Inc.	13G	Jul 29, 2025	1y	6,728,116	6.9%	+3,310,048 since Sep 30, 2024	Current
LKFT Lakefront Biotherapeutics NV	13D/A none of the classified purposes	Jul 24, 2025	1y	8,714,522	13.22%	+911,320 since May 15, 2025	Current
ETON Eton Pharmaceuticals, Inc.	13G/A	Dec 31, 2024	1y	1,981,003	7.7%	+583,334 since Dec 2, 2024	Current
ANAB Anaptysbio, Inc	13D/A	Aug 14, 2024	2y	11,692,494	25.8%	—	Unconfirmed since Aug 14, 2024

A 13D or 13G stays in force until its filer amends it and no amendment is due without a material change, so a stake with no filing in 24 months reads unconfirmed, never sold. An amendment reporting under 5% ends the filer's duty to amend, not necessarily the holding. Shares are restated onto today's split basis. Show 37 exited, below-5% or retired stakes

Portfolio style

Measured from the filed 13F common-share book for Jun 30, 2026, never from the firm's own description.

Style

Concentrated

The top 10 positions are 88.0% of the book (60%+)

Turnover

Medium turnover

37.2% over the last four quarters (30% to under 100%)

Horizon

Long horizon

Value-weighted holding period 14.3 quarters (12+), a floor since 26.4% of the book was already held when coverage starts

Closest benchmark: the Russell 2000 as of 2026-06-30, active share 99.0%; sector active share 90.8% against the combined 13F book's sector weights.

Over time 26 measured quarters

How the bands are measured

Style bands measure the filed 13F common-share book each closed quarter, tested in this order. Unknown: under $10,000,000 of valued equity or 5 stocks. Index-like (100+ stocks): active share of 20% or less against the closest benchmark, which is the S&P 500, S&P MidCap 400, S&P SmallCap 600, Russell 1000, Russell 2000, Nasdaq-100 or Dow Jones Industrial Average (weighted by an index-tracking fund's reported holdings or the index's constituents nearest the quarter end, over the names resolved to companies, and only when those are 90%+ of its weight) or every 13F filer's combined book, or index series holding 80%+ of the registered fund assets it advises (N-CEN) and equal to 50%+ of its book. Systematic-like: 500+ stocks, 100%+ annual turnover and a top 10 weight of 25% or less. Concentrated: a top 10 weight of 60%+ or 12 or fewer effective positions. Diversified active: none of these. Turnover is the smaller of buys and sells over average equity value, summed over four quarters: low under 30%, high 100%+. Horizon is the value-weighted number of quarters each position has been held: short under 4, long 12+.

Clone Performance

Build a hypothetical price-return history from this filer's public 13F holdings.

View clone backtest

Portfolio Concentration

31 tracked positions · as of Jun 30, 2026 · Δ vs Mar 31, 2026

Top Position

29.2%

+4.8 pts

Top 5

73.5%

−0.5 pts

Top 10

88.2%

−1.3 pts

HHI

1,699

Moderately concentrated+350

Portfolio Trend

26 quarters · across all stocks

Sector Breakdown

As of Jun 30, 2026

Sector	% Portfolio	Value	Positions
Healthcare	99.9%	$2,054,605,752	30
Financial Services	0.1%	$2,128,000	1

Last Quarter's Activity

Export CSV

Jun 30, 2026 vs Mar 31, 2026

Added To

Positions the filer increased

3 positions

Ticker	Company	Δ Shares	Shares	Value
ATRA	Atara Biotherapeutics, Inc.	+1,452,407	1,552,000	$17,816,960
STOK	Stoke Therapeutics, Inc.	+635,000	735,000	$24,049,200
CGON	CG Oncology, Inc.	+392,300	1,494,300	$106,170,015
No positions match the current search.

Trimmed

Positions the filer reduced

4 positions

Ticker	Company	Δ Shares	Shares	Value
MREO	Mereo BioPharma Group plc	−12,368,855	1,000,000	$318,000
RLAY	Relay Therapeutics, Inc.	−1,206,814	697,948	$13,058,607
ERAS	Erasca, Inc.	−570,000	330,000	$6,045,600
MBX	MBX Biosciences, Inc.	−388,500	388,500	$21,445,200
No positions match the current search.

New Positions

Positions the filer opened this quarter

9 positions

Ticker	Company	Shares	Value
TRAX	First Tracks Biotherapeutics, Inc.	3,174,519	$63,871,322
FULC	Fulcrum Therapeutics, Inc.	6,549,866	$23,972,509
LEGN	Legend Biotech Corp	800,000	$23,104,000
AURA	Aura Biosciences, Inc.	1,666,667	$11,833,335
ODTX	Odyssey Therapeutics, Inc.	555,555	$10,394,434
PHVS	Pharvaris N.V.	235,000	$8,126,300
NRIX	Nurix Therapeutics, Inc.	270,000	$6,550,200
ELOX	Eloxx Pharmaceuticals, Inc.	400,000	$5,552,000
AARD	Aardvark Therapeutics, Inc.	396,194	$2,282,077
No positions match the current search.

Sold Out

Positions the filer fully exited

7 positions

Ticker	Company	Shares	Value
JAZZ	Jazz Pharmaceuticals plc	1,706,469	$322,607,964
CNTA	Centessa Pharmaceuticals plc	6,000,000	$238,320,000
—		4,288,120	$155,744,518
XNCR	Xencor Inc	2,183,000	$26,326,980
REPL	Replimune Group, Inc.	1,000,000	$7,650,000
PRLD	Prelude Therapeutics Inc	947,049	$3,238,907
IBIO	iBio, Inc.	1,583,000	$3,007,700
No positions match the current search.

Portfolio Positions

Compact Export CSV View 13F filing

31 tracked positions · $2,056,733,752 total · filing declares 33 positions · $2,056,733,459 · as of Jun 30, 2026

All sectors Financial Services Healthcare

Ticker	Company	Type	Shares	Δ Shares	Value (USD)	% Δ Value	Held (qtrs)	Est. cost/share	% of Portfolio
ZYME	Zymeworks Inc. Healthcare	Held	22,970,388	0	$600,445,942	+4.4%	15	$9.83	29.19%
ANAB	Anaptysbio, Inc Healthcare	Held	7,880,094	0	$531,906,345	+21.7%	26+	before history	25.86%
AKTS	Aktis Oncology, Inc. Healthcare	Held	4,824,469	0	$155,492,635	+80.2%	2	$19.42	7.56%
CGON	CG Oncology, Inc. CALL + SHARES Healthcare	Added	2,055,800	+953,800	$146,064,590	+95.8%	3	$51.05	7.10%
ETON	Eton Pharmaceuticals, Inc. Healthcare	Held	2,171,938	0	$78,624,155	+46.7%	8	$9.57	3.82%
CRSP	CRISPR Therapeutics AG Healthcare	Held	1,389,276	0	$75,771,113	+14.7%	10	$71.59	3.68%
ORIC	Oric Pharmaceuticals, Inc. Healthcare	Held	6,728,116	0	$72,865,496	−14.5%	25	$15.26	3.54%
TRAX	First Tracks Biotherapeutics, Inc. Healthcare	NEW	3,174,519	NEW	$63,871,322	NEW	1	$18.70	3.11%
LKFT	Lakefront Biotherapeutics NV Healthcare	Held	1,667,119	0	$49,980,227	−0.1%	20	$30.99	2.43%
NGNE	Neurogene Inc. Healthcare	Held	1,271,342	0	$39,983,705	+56.0%	11	unpriced	1.94%
STOK	Stoke Therapeutics, Inc. Healthcare	Added	735,000	+635,000	$24,049,200	+638.6%	2	$32.19	1.17%
FULC	Fulcrum Therapeutics, Inc. Healthcare	NEW	6,549,866	NEW	$23,972,509	NEW	1	$6.08	1.17%
LEGN	Legend Biotech Corp Healthcare	NEW	800,000	NEW	$23,104,000	NEW	1	$26.97	1.12%
BBOT	BridgeBio Oncology Therapeutics, Inc. Healthcare	Held	2,823,126	0	$21,512,220	−14.9%	4	$10.42	1.05%
MBX	MBX Biosciences, Inc. Healthcare	Reduced	388,500	-388,500	$21,445,200	−7.5%	8	unpriced	1.04%
ZBIO	Zenas BioPharma, Inc. Healthcare	Held	789,500	0	$20,037,510	+29.8%	3	$32.89	0.97%
ATRA	Atara Biotherapeutics, Inc. Healthcare	Added	1,552,000	+1,452,407	$17,816,960	+3682.2%	11	$8.70	0.87%
RLAY	Relay Therapeutics, Inc. Healthcare	Reduced	697,948	-1,206,814	$13,058,607	−31.1%	2	$8.95	0.63%
AURA	Aura Biosciences, Inc. Healthcare	NEW	1,666,667	NEW	$11,833,335	NEW	1	$7.15	0.58%
ODTX	Odyssey Therapeutics, Inc. Healthcare	NEW	555,555	NEW	$10,394,434	NEW	1	$17.54	0.51%
EIKN	Eikon Therapeutics, Inc. Healthcare	Held	732,606	0	$9,560,508	+23.3%	2	$13.37	0.46%
PHVS	Pharvaris N.V. Healthcare	NEW	235,000	NEW	$8,126,300	NEW	1	$30.25	0.40%
ZURA	Zura Bio Ltd Healthcare	Held	1,179,715	0	$6,960,318	−0.8%	2	$6.04	0.34%
PHAT	Phathom Pharmaceuticals, Inc. Healthcare	Held	625,000	0	$6,781,250	−2.3%	2	$12.63	0.33%
NRIX	Nurix Therapeutics, Inc. Healthcare	NEW	270,000	NEW	$6,550,200	NEW	1	$17.03	0.32%
ERAS	Erasca, Inc. Healthcare	Reduced	330,000	-570,000	$6,045,600	−58.5%	2	$11.82	0.29%
ELOX	Eloxx Pharmaceuticals, Inc. Healthcare	NEW	400,000	NEW	$5,552,000	NEW	1	unpriced	0.27%
AARD	Aardvark Therapeutics, Inc. CALL + SHARES Healthcare	NEW	410,894	NEW	$2,366,749	NEW	1	$4.67	0.12%
HLXC	Helix Acquisition Corp. III Financial Services	Held	200,000	0	$2,128,000	+4.7%	2	$10.24	0.10%
MREO	Mereo BioPharma Group plc Healthcare	Reduced	1,000,000	-12,368,855	$318,000	−92.8%	3	$1.30	0.02%
SRZNW	Surrozen, Inc. Healthcare	Held	4,444	0	$115,322	−10.9%	20	unpriced	0.01%

Covers the securities this platform tracks: U.S.-listed common stock and the put/call positions reported on it. A 13F can also report security types outside that coverage — preferred shares, bonds, warrants, untracked share classes — so the filing's own declared total can exceed the figures above. The source filing is linked at the top of this table.