| 2.68% | % of Shares Held by All Insider |
| 85.20% | % of Shares Held by Institutions |
| 87.55% | % of Float Held by Institutions |
| 61 | Number of Institutions Holding Shares |
| Holder | Shares | Date Reported | % Out | Value |
|---|---|---|---|---|
| Flagship Pioneering Inc. | 18,233,403 | Mar 30, 2019 | 56.90% | 145,867,224 |
| FMR, LLC | 3,325,107 | Mar 30, 2019 | 10.38% | 26,600,856 |
| Harbourvest Partners, LLC | 1,763,505 | Mar 30, 2019 | 5.50% | 14,108,040 |
| Credit Suisse Ag/ | 1,103,763 | Mar 30, 2019 | 3.44% | 8,830,104 |
| Sectoral Asset Management, Inc. | 651,077 | Mar 30, 2019 | 2.03% | 5,208,616 |
| Blackrock Inc. | 646,233 | Mar 30, 2019 | 2.02% | 5,169,864 |
| Vanguard Group, Inc. (The) | 431,650 | Mar 30, 2019 | 1.35% | 3,453,200 |
| Goldman Sachs Group, Inc. | 269,819 | Mar 30, 2019 | 0.84% | 2,158,552 |
| Samsara BioCapital, LLC | 227,529 | Mar 30, 2019 | 0.71% | 1,820,232 |
| State Street Corporation | 204,883 | Mar 30, 2019 | 0.64% | 1,639,064 |
| Holder | Shares | Date Reported | % Out | Value |
|---|---|---|---|---|
| Fidelity Growth Company Fund | 710,182 | Apr 29, 2019 | 2.22% | 5,954,876 |
| Goldman Sachs Tr-Goldman Sachs Small/Mid Cap Growth Fund | 278,971 | Nov 29, 2018 | 0.87% | 2,767,392 |
| iShares Russell 2000 ETF | 278,020 | Apr 29, 2019 | 0.87% | 2,331,197 |
| Vanguard Total Stock Market Index Fund | 211,239 | Dec 30, 2018 | 0.66% | 2,748,219 |
| Fidelity Series Growth Company Fund | 187,100 | Apr 29, 2019 | 0.58% | 1,568,833 |
| iShares Russell 2000 Growth ETF | 116,140 | Apr 29, 2019 | 0.36% | 973,833 |
| Fidelity Select Portfolios - Biotechnology | 81,900 | Apr 29, 2019 | 0.26% | 686,731 |
| Vanguard Extended Market Index Fund | 61,795 | Dec 30, 2018 | 0.19% | 803,952 |
| Fidelity Small Cap Index Fund | 49,146 | Jan 30, 2019 | 0.15% | 441,331 |
| ARK ETF Tr-ARK Genomic Revolution Multi Sector ETF | 44,970 | Oct 30, 2018 | 0.14% | 409,676 |