bluebird bio, Inc. BLUE → 2seventy bio, Inc. TSVT
| Parent | bluebird bio, Inc. BLUE |
|---|---|
| Spinco | 2seventy bio, Inc. TSVT |
| Status | Completed |
| Structure | Spin-off A filing states a pro-rata distribution: holders receive shares automatically. |
| Focus | Not focus-increasing Parent and spinco remain in the same industry; the separation divides scale rather than business. |
| Ratio | 1 2seventy bio share for every 3 bluebird bio shares |
| Checked against EDGAR | 2026-08-22 |
Data trap
The distribution took effect at 12:01 a.m. on November 4, before the open, and yet regular-way trading did not begin until November 5 — the opposite of Enhabit, which had the same stated effective time and opened the same day. The gap is expensive here: the November 4 close was 26.65 against 33.62 the next session, so a return anchored on the distribution date is wrong by a quarter. Separately, the filings disagree about which Nasdaq tier the shares listed on, so the exchange is recorded only as Nasdaq.
Still live.
Catalyst clock
- 2021-01-11Separation announced
- 2021-09-09Form 10 filed
- 2021-10-08Form 10 last amended
- 2021-10-18Form 10 effective
- 2021-10-19Record date
- —When-issued trading opens
- 2021-11-04Distribution
- 2021-12-01First standalone earnings
- —Index inclusion announced
Performance since separation
| 2seventy bio, Inc. since separation, to delisting 2025-05-13 | -85.13% |
|---|---|
| bluebird bio, Inc. over the same window | -98.99% |
| S&P 500 (SPY) over the same window | +24.86% |
| Russell 2000 (IWM) over the same window | -12.86% |
| Excess over the S&P 500 | -109.99% |
| Excess over the Russell 2000 | -72.27% |
Measured from the first regular-way close on or after the distribution — 2021-11-05 at 33.62 — to 2025-05-12 at 5.00. Window: 3.5 years. The 2021-11-04 session was skipped: it traded on when-issued volume, not regular-way, and pricing from it would measure the return against a market that no longer existed the next day. 2seventy bio, Inc. stopped trading on 2025-05-13 — acquired, taken private or wound up — so this return runs to that date, not to today. It is kept here deliberately: dropping deals that ended in an acquisition would flatter every base rate on this site, because being bought is often the best outcome a spin-off has. Two benchmarks, because one is misleading: spin-offs are usually small companies, and across this period small caps lagged the S&P by several points a year on their own. Measured against the S&P alone, roughly a third of any shortfall is company size rather than the separation. Returns are arithmetic over end-of-day closing prices. Unlike every other figure on this page, they do not come from a filing.
Pre-distribution investor return
| Parent, announcement to separation | price history starts after the separation |
|---|---|
| Combined (bluebird bio, Inc. + 2seventy bio, Inc.), pre-distribution to now | -98.46% |
| Combined excess over the S&P 500 | -123.91% |
| Combined excess over the Russell 2000 | -85.57% |
Combined treats a pre-spin holding as 1 2seventy bio share for every 3 bluebird bio shares valued at the parent's last close before regular post-spin trading resumed — 2021-11-03 at 321.47 — against that same basket today. That baseline is a practical proxy, not an attempt to isolate exactly how much value the separation transferred: for a large parent and a small spinco, ordinary day-to-day price noise can be bigger than the transfer itself.
Filings
Every fact on this page comes from one of these.
- 8-Kfiled 2021-01-11 · 0001293971-21-000002Item 8.01 announcement of the intent to separate the oncology business
- 10-12B/Afiled 2021-10-08 · 0001628280-21-019906Final Form 10 amendment
- 8-Kfiled 2021-10-18 · 0001628280-21-020151Form 10 declared effective October 18, 2021
- 8-Kfiled 2021-11-04 · 0001628280-21-021610Completion: distribution effective 12:01 a.m. on November 4, 2021, regular-way trading from November 5; attaches the definitive information statement
- 10-Qfiled 2021-12-01 · 0001860782-21-000006First standalone periodic report
- 25-NSEfiled 2025-05-13 · 0001354457-25-000408Removal from listing following the Bristol-Myers Squibb tender offer and merger at 5.00 dollars cash per share
Notes
bluebird bio's separation of its oncology business. bluebird itself was acquired in 2025 and no longer trades, so the parent leg of this comparison has no price for the later part of the window. 2seventy was acquired by Bristol-Myers Squibb in May 2025 at 5.00 dollars a share. Classified non-focus-increasing: both sides remained clinical-stage biotechnology companies.