ACCELERON PHARMA (SYN_00434H108) — Institutional Holders & Hedge Fund Ownership
ACCELERON PHARMA (SYN_00434H108) institutional ownership: 8 hedge funds and institutional investors, holding 7.3M shares ($1.26B), as of Q3 2021, per SEC Form 13F-HR filings.
Held across hedge funds, family offices, and large institutional portfolios, ACCELERON PHARMA (SYN_00434H108)'s reported 13F ownership offers a quarterly read on professional buyer / seller positioning in SYN_00434H108. These filings are aggregated to surface top holders, quarterly buyers and sellers, position changes, and peer-fund overlap.
The top SYN_00434H108 shareholders by portfolio weight are Darwin Global Management (63.36%), Avoro Capital Advisors (10.82%), and Pentwater Capital Management (2.48%). In Q3 2021, Darwin Global Management made the largest position increase (+27.72%).
Top 8 Institutional Holders of ACCELERON PHARMA (SYN_00434H108) — Q3 2021
| # | Fund | Shares | Market Value | Portfolio Weight |
|---|---|---|---|---|
| 1 | Darwin Global Management | 2,000,000 | $344.2M | 63.36% |
| 2 | Avoro Capital Advisors | 4,000,000 | $688.4M | 10.82% |
| 3 | Pentwater Capital Management | 1,050,000 | $180.7M | 2.48% |
| 4 | Mason Capital Management | 10,000 | $1.7M | 0.80% |
| 5 | Melqart | 82,000 | $14.1M | 0.71% |
| 6 | Deerfield | 145,000 | $25.0M | 0.49% |
| 7 | Avidity | 35,000 | $6.0M | 0.15% |
| 8 | Baker Bros. Advisors | 22,430 | $3.9M | 0.02% |
- 8Hedge funds holding
- 7,344,430Shares held (disclosed)
- $1.26B13F market value
- 0.76%Median portfolio weight
Ownership History
Quarter-by-quarter share count, market value, and portfolio conviction weight (up to 5 of the heaviest weight-by-portfolio funds) of SYN_00434H108. Sourced from 13F filings; reflects long equity positions only.
Quarter-over-Quarter ActivityQ3 2021
The biggest weight-increase and weight-decrease changes among funds that hold SYN_00434H108. Deltas compare the selected filing to the previous reporting quarter.
Top buyers
- Darwin Global Management+27.72% · +239,654 shares
- Avoro Capital Advisors+4.27% · +1,000,000 shares
- Pentwater Capital Management+2.48% · +1,050,000 shares
Top sellers
- Avidity-1.06% · -323,500 shares
- Viking Global-0.07% · -196,136 shares
- Deerfield-0.00% · -74,500 shares
Options Activity
- Total calls1,704,200 (+1,704,200)
Ownership Statistics
- Funds holding
- 8
- Median weight
- 0.76%
- Largest holder
- Darwin Global Management · 63.36%
- Smallest holder
- Baker Bros. Advisors · 0.02%
- Shares held
- 7,344,430 (+1,787,518)
All Institutional HoldersSortable · searchable
All institutional investors (Max 50) holding SYN_00434H108 in the selected quarter. Click a fund name to drill into its full 13F portfolio.
| 1 | Darwin Global Management | 2,000,000 | $344.2M | 63.36% |
| 2 | Avoro Capital Advisors | 4,000,000 | $688.4M | 10.82% |
| 3 | Pentwater Capital Management | 1,050,000 | $180.7M | 2.48% |
| 4 | Mason Capital Management | 10,000 | $1.7M | 0.80% |
| 5 | Melqart | 82,000 | $14.1M | 0.71% |
| 6 | Deerfield | 145,000 | $25.0M | 0.49% |
| 7 | Avidity | 35,000 | $6.0M | 0.15% |
| 8 | Baker Bros. Advisors | 22,430 | $3.9M | 0.02% |
Methodology & FAQ
Methodology: How We Track SYN_00434H108 Institutional Holdings
Our data is systematically aggregated directly from quarterly Form 13F-HR disclosures submitted to the U.S. Securities and Exchange Commission (SEC).
- Who Must File (Reporting Threshold): This dataset includes filings from U.S. institutional investment managers, hedge funds, mutual funds, university endowments, and family offices managing at least $100 million in Section 13(f) securities (including equities, options, convertibles, ETFs, and warrants).
- What is Included (Data Scope): We capture long positions in Section 13(f) securities for ACCELERON PHARMA INC (SYN_00434H108). By SEC regulation, 13F filings do not require the disclosure of short positions, non-U.S. holdings, or OTC derivatives. Listed options are excluded from portfolio weight calculations to ensure comparability across filers.
- Portfolio Weight Explained (Metric Definition): “Portfolio Weight” shows how much of a fund's total reported 13F portfolio value (excluding listed options) is allocated to SYN_00434H108 on the specific reporting date.
- How to Use This Data (Interpretation): Quarter-over-quarter changes in shares and portfolio weight reflect a combination of active trading and market price movements. These are descriptive metrics of fund allocation, not explicit buy or sell signals.
How do you measure hedge fund conviction and institutional concentration in SYN_00434H108?
We evaluate fund conviction by looking at portfolio weight rather than just absolute share count. By tracking how the largest holders —such as Darwin Global Management , Avoro Capital Advisors , and Pentwater Capital Management as of Q3 2021— change their position sizing quarter-over-quarter, we help investors distinguish between deliberate position sizing changes and passive mark-to-market drift.
Does the SYN_00434H108 ownership data include short interest or options?
SEC Form 13F mandates the disclosure of long positions in Section 13(f) securities, which includes equities and listed options (put and call contracts), but excludes short interest, swaps, and OTC derivatives by regulatory design. On this platform, listed options are excluded from portfolio weight calculations to ensure comparability across filers.
Are family offices and university endowments included in this SYN_00434H108 data?
Yes. In addition to traditional hedge funds and large asset managers, any institutional entity exercising investment discretion over at least $100 million in Section 13(f) securities must file a Form 13F. This explicitly includes single-family offices and university endowments. If a qualifying family office or endowment holds SYN_00434H108 stock, their allocation is systematically aggregated alongside traditional fund data.
When is the institutional ownership data updated, and is there a reporting lag?
Institutional investment managers are required to file their Form 13F within 45 days after the end of a calendar quarter (the standard “T+45” window). Our platform re-ingests new filings from the SEC EDGAR database on a nightly cycle, typically within 24–48 hours of publication, providing a point-in-time snapshot of reported consensus positioning for SYN_00434H108 as of each filing date.