Rallybio
RLYB
46 hedge funds and large institutions have $20.7M invested in Rallybio in 2025 Q4 according to their latest regulatory filings, with 4 funds opening new positions, 7 increasing their positions, 11 reducing their positions, and 2 closing their positions.
100% more first-time investments, than exits
New positions opened: 4 | Existing positions closed: 2
47% more capital invested
Capital invested by funds: $14.1M → $20.7M (+$6.62M)
2% more funds holding
Funds holding: 45 → 46 (+1)
1.09% less ownership
Funds ownership: 8.46% → 7.38% (-1.1%)
36% less repeat investments, than reductions
Existing positions increased: 7 | Existing positions reduced: 11
40% less funds holding in top 10
Funds holding in top 10: 5 → 3 (-2)
Top Buyers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
Renaissance Technologies
New York
|
+$77.8K |
| 2 |
XT
XTX Topco
George Town,
Cayman Islands
|
+$24.6K |
| 3 |
GCP
GSA Capital Partners
London,
United Kingdom
|
+$12.4K |
| 4 |
Two Sigma Advisers
New York
|
+$12.4K |
| 5 |
Vanguard Group
Malvern,
Pennsylvania
|
+$10.7K |
Top Sellers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
Citadel Advisors
Miami,
Florida
|
-$119K |
| 2 |
RC
Rangeley Capital
New Canaan,
Connecticut
|
-$27.7K |
| 3 |
Susquehanna International Group
Bala Cynwyd,
Pennsylvania
|
-$22.9K |
| 4 |
VF
Virtu Financial
New York
|
-$7.83K |
| 5 |
HF
HRT Financial
New York
|
-$6.97K |
RLYB Hedge Fund Activity: Q4 2025 in Review
46 of the 8,270 institutional investors tracked by Wall St. Rank reported a position in Rallybio (RLYB) for Q4 2025, worth a combined $20.7M — up 47% from $14.1M a quarter earlier.
Buyers outnumbered sellers: 4 funds opened new RLYB positions and 2 closed out — a net gain of 2 holders — while 7 added to existing stakes and 11 trimmed.
The largest buyer was Renaissance Technologies, adding an estimated $77.8K. The largest seller was Citadel Advisors, cutting an estimated $119K.
- 46 institutional investors held Rallybio (RLYB) as of Q4 2025, up from 45 in Q3 2025.
- Funds reported $20.7M of Rallybio stock for Q4 2025, up 47% quarter-over-quarter.
- 4 funds opened new Rallybio positions in Q4 2025 and 2 closed out, a net change of +2 holders.
- The largest Rallybio buyer in Q4 2025 was Renaissance Technologies, an estimated $77.8K added.
- The largest Rallybio seller in Q4 2025 was Citadel Advisors, an estimated $119K sold.
Based on aggregated 13F filings for Q4 2025.