13F
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Rock Springs Capital Management LP

13F equity value
$1.7B
Positions
100
Top 10 concentration
40.6%
Quarters / total new picks
29 / 118
13F equity value over time
$0M$3B$5B2017201820192020202120222023202420252026

"13F equity value" = market value of this filer's US-listed long equity positions only. It excludes cash, bonds, non-US and short positions, so it understates a fund's true assets under management — often by a lot.

Not significant Verdict

13F holdings are disclosed ~45 days after quarter-end, and they never reveal when within the quarter a fund actually bought. So any 13F-based summary is structurally late and blurred — this applies to every fund, including this one.

We backtested copying it anyway. Buying this fund's new positions the day each filing went public, over 29 quarters, returned +4.3% per quarter — versus +3.5% per quarter from simply owning every 13F stock. It beat that baseline in only 44.8% of quarters (excess t = -0.10, not statistically significant). Its filings tell you what it bought — not what you should buy.

Avg 2Q excess
-0.6%
t-stat
-0.10
Quarterly win rate
45%
Annualized excess
-0.8%
$1 → follow vs universe
$2.32 vs $2.44
Cumulative return: $1 invested in new picks vs universe
1.00 20180331: universe 1.04120180630: universe 0.95920180930: universe 1.00320181231: universe 0.99220190331: universe 0.97520190630: universe 1.04820190930: universe 1.12720191231: universe 0.90920200331: universe 1.09620200630: universe 1.21120200930: universe 1.48520201231: universe 1.55320210331: universe 1.56620210930: universe 1.40620220331: universe 1.51020220630: universe 1.39920220930: universe 1.50220230331: universe 1.58320230630: universe 1.52620230930: universe 1.73220231231: universe 1.81020240331: universe 1.85120240630: universe 2.01920240930: universe 2.00120241231: universe 1.86820250331: universe 2.03620250630: universe 2.10020250930: universe 2.36220251231: universe 2.443 20180331: follow 1.10320180630: follow 1.13220180930: follow 1.10120181231: follow 1.30220190331: follow 1.27220190630: follow 1.61720190930: follow 1.70720191231: follow 1.62820200331: follow 1.71820200630: follow 1.67620200930: follow 1.99120201231: follow 1.47120210331: follow 1.70420210930: follow 1.42220220331: follow 1.67720220630: follow 1.36520220930: follow 1.01920230331: follow 0.98020230630: follow 0.83920230930: follow 1.04720231231: follow 1.06220240331: follow 1.14720240630: follow 1.13020240930: follow 1.05920241231: follow 1.01820250331: follow 1.13120250630: follow 1.85120250930: follow 2.08120251231: follow 2.318 0.77 1.70 2.64 20182019202020212022202320242025 Follow Universe

Quarterly compounding, invested quarters only · entry 47 days after quarter-end (when 13F data becomes public)

Listed as facts. See the verdict above before treating this as signal.

Top 20 holdings of 100 · 2026 Q1

Ticker Value Weight QoQ
RVMD $118M
6.9%
TRIM
LLY $91M
5.3%
TRIM
MDGL $90M
5.3%
ADD
MIRM $75M
4.4%
ADD
ARGX $72M
4.2%
TRIM
RYTM $60M
3.5%
HOLD
INSM $51M
3.0%
HOLD
ASND $44M
2.6%
TRIM
XENE $44M
2.6%
TRIM
TVTX $44M
2.6%
TRIM
KYMR $41M
2.4%
HOLD
PEN $40M
2.3%
HOLD
ISRG $38M
2.2%
HOLD
SRRK $36M
2.1%
HOLD
ELVN $32M
1.9%
ADD
BSX $32M
1.9%
ADD
IRTC $31M
1.8%
ADD
GPCR $31M
1.8%
TRIM
AGIO $27M
1.6%
HOLD
RARE $26M
1.5%
TRIM

QoQ vs previous quarter's share count · NEW = new position · ADD/TRIM = ±2% shares · HOLD = unchanged.

Listed as facts. See the verdict above before treating this as signal.

New positions in 2026 Q1

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Method & Limitations

Method: a "new position" = held this quarter, absent last quarter (options excluded; stocks with <50 prior holders excluded to filter spin-off artifacts). Entry 47 days after quarter-end — the first day the public could act on the filing. Benchmark = equal-weighted universe of all 13F-held stocks. Limitations: quarterly snapshots can't see intra-quarter trades; survivorship bias — funds that shut down are absent, which flatters the sample. Statistics, not advice.