The cluster is dominated by passive index rebalancing, not active fundamental conviction. Monitor for any active manager 13F filings or insider buying to confirm a genuine thesis.
Executive Summary
Four mega-passive institutional investors (BlackRock, State Street, Fidelity, Morgan Stanley) significantly increased their positions in Amylyx Pharmaceuticals during Q3 2025, with Fidelity and Morgan Stanley more than tripling their holdings. The aggregate buying totaled $300.2M in current value, a net increase of $235.8M, indicating strong passive rebalancing or index-driven accumulation rather than active fundamental conviction. The cluster is dominated entirely by passive/index funds, which weakens the signal as a directional thesis.
Key Financial Metrics
Institutional Positions
Net institutional flow: $235.8M
▲ Buyers (4)
| Institution | Action | Change | Position Value | Value Δ |
|---|---|---|---|---|
| BlackRock | ADD | +29.6% | $97.0M | $61.7M |
| State Street | ADD | +60.7% | $22.0M | $15.6M |
| Fidelity | DOUBLED | +273.3% | $154.6M | $135.1M |
| Morgan Stanley | DOUBLED | +300.6% | $26.5M | $23.4M |
Key Facts
- 4 mega-passive institutions added $235.8M in net new holdings during Q3 2025
- Fidelity doubled its position (+273.3%) to $154.6M, the largest dollar increase
- Morgan Stanley tripled its position (+300.6%) to $26.5M
- Zero institutional sellers in the cluster
- All buyers are mega-passive/index funds — no active managers, hedge funds, or activists involved
Financial Impact
4 institutions accumulated $300.2M in current holdings, net increase of $235.8M from prior quarter. No selling activity.
Risk Factors
- Passive buying provides no fundamental signal — may reverse on next rebalance
- 13F data is 45+ days stale; positions may have already been unwound
Market Snapshot
Investment Themes
Documents Analyzed
This report is based on 1 institutional 13F filing from SEC EDGAR.
| Document | Accession Number |
|---|---|
| INST-CLUSTER Data (Synthetic) | inst-cluster-AMLX-2025-Q3 |
Filters
| Type | Now | ||||
|---|---|---|---|---|---|
Oct 5, 2026 21d ago | 144 | $28.04 | awaiting T+20 | — | — |
Sep 14, 2026 6w ago | Insider Cluster | $33.15 $26.85 | ▼ −19.00% | ▼ −21.73% | — |
Sep 11, 2026 6w ago | 144 | $33.64 $27.48 | ▼ −18.31% | ▼ −20.57% | — |
Aug 18, 2026 10w ago | 8-K | $35.11 $33.05 | ▼ −5.87% | ▼ −4.88% | — |
Aug 15, 2026 10w ago | Institutional Cluster | $21.43 $33.15 | ▲ +54.69% | ▲ +56.67% | — |
Aug 6, 2026 11w ago | 8-K | $24.19 $33.96 | ▲ +40.39% | ▲ +39.79% | — |
Jun 11, 2026 19w ago | Institutional Cluster | $13.91 $18.38 | ▲ +32.14% | ▲ +30.24% | — |
Apr 23, 2026 26w ago | DEFA14A | $17.32 $13.61 | ▼ −21.42% | ▼ −26.05% | — |
Mar 2, 2026 34w ago | Insider Cluster | $15.30 $12.76 | ▼ −16.60% | ▼ −8.66% | — |
Feb 23, 2026 35w ago | Insider Cluster | $13.90 $13.53 | ▲ +2.66% | ▼ −1.28% | — |
US Market Status
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