Bain Capital Life Sciences Investors, LLC — 13F Holdings & Portfolio
CIK 1703031 · latest 13F-HR filed 2026-08-14
Bain Capital Life Sciences Investors, LLC manages $1.68B in 13F-reported U.S. long-equity assets across 21 reported positions as of its 2026-06-30 13F-HR filing. Its largest disclosed positions are KLRA (29.58%), HTFL (14.74%), NAMS (7.67%). Quarter over quarter (versus its 2026-03-31 filing) the fund opened 2 new positions and exited 1; 11 existing positions rose in reported value and 6 fell.
AUM is the long-equity portion reported on Form 13F-HR. Excludes short positions, cash, foreign holdings, and non-13F assets. For informational purposes only — not investment advice.
Long-equity book
Distinct positions
Filed 2026-08-14
vs 2026-03-31
Portfolio charts
Latest quarter's book, what changed, and how the portfolio has evolved across filings.
Portfolio map
Q2 26Box size = position value; colour = change in share count vs the prior quarter (green added, red trimmed, blue new). Rows split across managers or share classes are combined. Click a box for the stock.
Sector mix
% of 13F valueSectors from each company's SIC code; funds and ETFs grouped separately.
Biggest buys and sells
Q1 26 → Q2 26Estimated from the change in shares held × the quarter-end price, so price moves alone don't count as buying. New and exited positions are included.
13F assets and positions
4 quartersTotal reported 13F value (bars) and number of positions (line) each quarter. Value changes include market moves.
Top positions over time
reported valueThe eight largest current positions, valued at each quarter end.
Concentration
top 10 = 87.9%Cumulative share of the portfolio held in the largest N positions.
| Name | Title / Status | Ownership | Type |
|---|
Quarter-over-quarter changes
Changes in reported position value vs the prior 13F, so price moves count too, not just shares bought or sold.
Top Adds (vs prior quarter)
- ALKERMES PLC$80.0M +370.7%
- CABALETTA BIO INC$27.6M +106.0%
- SOLID BIOSCIENCES INC$27.4M +38.7%
- PHARVARIS N V$16.9M +22.4%
- C4 THERAPEUTICS INC$14.6M +77.6%
Top Trims
- NEWAMSTERDAM PHARMA COMPANY-$104.9M -44.8%
- OLEMA PHARMACEUTICALS INC-$22.8M -20.5%
- RAPID MICRO BIOSYSTEMS INC-$4.6M -23.8%
- UPSTREAM BIO INC-$3.6M -46.7%
- ANNEXON INC-$3.5M -12.3%
Bain Capital Life Sciences Investors, LLC Holdings (2026-06-30)
Rows tagged Call or Put are options positions, not stock. Per SEC Form 13F-HR, Value shows the notional value of the underlying (shares covered × underlying price), not the option premium. Shares is the number of underlying shares covered (divide by 100 for contract count).
| # | Issuer | Symbol | CUSIP | Value | Weight | Shares | Type |
|---|---|---|---|---|---|---|---|
| 1 | KAILERA THERAPEUTICS INC | KLRA | 482931102 | $497.5M | 29.58% | 22,583,268 | SH |
| 2 | HEARTFLOW INC | HTFL | 42238D107 | $247.9M | 14.74% | 8,448,158 | SH |
| 3 | NEWAMSTERDAM PHARMA COMPANY | NAMS | N62509109 | $129.0M | 7.67% | 3,806,566 | SH |
| 4 | SAVARA INC | SVRA | 805111101 | $108.4M | 6.45% | 17,600,621 | SH |
| 5 | ALKERMES PLC | ALKS | G01767105 | $101.5M | 6.04% | 1,937,938 | SH |
| 6 | SOLID BIOSCIENCES INC | SLDB | 83422E204 | $98.0M | 5.83% | 9,808,819 | SH |
| 7 | PHARVARIS N V | PHVS | N69605108 | $92.5M | 5.50% | 2,675,509 | SH |
| 8 | OLEMA PHARMACEUTICALS INC | OLMA | 68062P106 | $88.6M | 5.27% | 7,085,249 | SH |
| 9 | HEMAB THERAPEUTICS HOLDINGS INC | COAG | 423494103 | $60.6M | 3.60% | 1,650,000 | SH |
| 10 | CABALETTA BIO INC | CABA | 12674W109 | $53.6M | 3.19% | 17,241,445 | SH |
| 11 | X4 PHARMACEUTICALS INC | XFOR | 98420X202 | $37.2M | 2.21% | 7,967,454 | SH |
| 12 | DIANTHUS THERAPEUTICS INC | DNTH | 252828108 | $35.3M | 2.10% | 362,470 | SH |
| 13 | C4 THERAPEUTICS INC | CCCC | 12529R107 | $33.5M | 1.99% | 7,171,910 | SH |
| 14 | KYVERNA THERAPEUTICS INC | KYTX | 501976104 | $25.7M | 1.53% | 2,885,000 | SH |
| 15 | ANNEXON INC | ANNX | 03589W102 | $25.3M | 1.51% | 4,437,731 | SH |
| 16 | RAPID MICRO BIOSYSTEMS INC | RPID | 75340L104 | $14.6M | 0.87% | 8,434,560 | SH |
| 17 | DISC MEDICINE INC | IRON | 254604101 | $10.3M | 0.61% | 141,234 | SH |
| 18 | ATEA PHARMACEUTICALS INC | AVIR | 04683R106 | $9.7M | 0.57% | 2,075,639 | SH |
| 19 | XILIO THERAPEUTICS INC | XLO | 98422T209 | $6.4M | 0.38% | 664,021 | SH |
| 20 | UPSTREAM BIO INC | UPB | 91678A107 | $4.2M | 0.25% | 600,949 | SH |
| 21 | NEWAMSTERDAM PHARMA COMPANY | NAMSW | N62509117 | $2.1M | 0.13% | 99,999 | SH |
| Period | Filed | AUM | Holdings | Accession |
|---|---|---|---|---|
| 2026-06-30 | 2026-08-14 | $1.68B | 21 | 0001193125-26-350470 |
| 2026-03-31 | 2026-05-15 | $1.11B | 20 | 0001193125-26-226961 |
| 2025-12-31 | 2026-02-17 | $1.31B | 19 | 0001193125-26-054833 |
| 2025-09-30 | 2025-11-14 | $1.51B | 21 | 0001193125-25-283094 |
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