Alkermes plc. ALKS → Mural Oncology plc MURA
| Parent | Alkermes plc. ALKS |
|---|---|
| Spinco | Mural Oncology plc MURA |
| 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 Mural Oncology share for every 10 Alkermes shares |
| Checked against EDGAR | 2026-08-22 |
Data trap
An Irish plc separated by distribution rather than by scheme, and the timing follows the same awkward pattern as 2seventy bio: effective at 12:01 a.m. on November 15, before the open, but regular-way trading only from November 16. The first earnings release is also later than it looks — the first periodic report carried no results release, and the first Item 2.02 filing came four months after separation.
The restated filings have landed; this is kept as history.
Catalyst clock
- 2022-11-02Separation announced
- 2023-10-10Form 10 filed
- 2023-10-26Form 10 last amended
- 2023-10-31Form 10 effective
- 2023-11-06Record date
- —When-issued trading opens
- 2023-11-15Distribution
- 2024-03-26First standalone earnings
- —Index inclusion announced
Performance since separation
| Mural Oncology plc since separation, to delisting 2025-12-05 | -46.32% |
|---|---|
| Alkermes plc. over the same window | +19.95% |
| S&P 500 (SPY) over the same window | +51.89% |
| Russell 2000 (IWM) over the same window | +40.62% |
| Excess over the S&P 500 | -98.21% |
| Excess over the Russell 2000 | -86.94% |
Measured from the first regular-way close on or after the distribution — 2023-11-16 at 3.80 — to 2025-12-09 at 2.04. Window: 2.1 years. Mural Oncology plc stopped trading on 2025-12-05 — 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 | +0.54% |
|---|---|
| Combined (Alkermes plc. + Mural Oncology plc), pre-distribution to now | +18.41% |
| Combined excess over the S&P 500 | -33.81% |
| Combined excess over the Russell 2000 | -22.46% |
Combined treats a pre-spin holding as 1 Mural Oncology share for every 10 Alkermes shares valued at the parent's last close before regular post-spin trading resumed — 2023-11-14 at 24.19 — 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. Run-up measures only the parent's own price, from the announcement date to that same baseline — how far the market had already moved before the separation's mechanics ever happened.
Filings
Every fact on this page comes from one of these.
- 10-12B/Afiled 2023-10-26 · 0001193125-23-264176Final Form 10 amendment; its Ex-99.1 is only a preliminary information statement
- 8-Kfiled 2023-10-31 · 0001193125-23-267334Form 10 declared effective October 31, 2023; sets the November 6 record date and the 1-for-10 ratio
- 8-Kfiled 2023-11-15 · 0001193125-23-277530Completion: distribution of all outstanding shares effective 12:01 a.m. on November 15, 2023, regular-way trading from November 16
- 10-Qfiled 2023-12-14 · 0000950170-23-070413First standalone periodic report
- 25-NSEfiled 2025-12-05 · 0001354457-25-001216Removal from listing following the XOMA Royalty scheme of arrangement at 2.035 dollars cash per share
Notes
Alkermes' separation of its oncology business into an Irish-incorporated public company. Mural was acquired by XOMA Royalty in December 2025 at 2.035 dollars a share under an Irish scheme of arrangement, so its return runs to that delisting. Classified non-focus-increasing: parent and spinco share a four-digit SIC and both remained pharmaceutical developers, separating therapeutic areas rather than industries.