| 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 | Jun 29, 2019 | 56.87% | 163,735,958 |
| FMR, LLC | 3,367,653 | Jun 29, 2019 | 10.50% | 30,241,523 |
| Harbourvest Partners, LLC | 1,763,505 | Jun 29, 2019 | 5.50% | 15,836,274 |
| Credit Suisse Ag/ | 1,102,273 | Jun 29, 2019 | 3.44% | 9,898,411 |
| Sectoral Asset Management, Inc. | 669,382 | Jun 29, 2019 | 2.09% | 6,011,050 |
| Blackrock Inc. | 654,753 | Jun 29, 2019 | 2.04% | 5,879,681 |
| Vanguard Group, Inc. (The) | 435,335 | Jun 29, 2019 | 1.36% | 3,909,308 |
| Goldman Sachs Group, Inc. | 269,645 | Jun 29, 2019 | 0.84% | 2,421,412 |
| Samsara BioCapital, LLC | 227,529 | Jun 29, 2019 | 0.71% | 2,043,210 |
| State Street Corporation | 221,192 | Jun 29, 2019 | 0.69% | 1,986,304 |
| Holder | Shares | Date Reported | % Out | Value |
|---|---|---|---|---|
| Fidelity Growth Company Fund | 1,619,468 | Jun 29, 2019 | 5.05% | 14,542,822 |
| Fidelity Series Growth Company Fund | 407,336 | Jun 29, 2019 | 1.27% | 3,657,877 |
| iShares Russell 2000 ETF | 274,603 | Jun 29, 2019 | 0.86% | 2,465,934 |
| Goldman Sachs Tr-Goldman Sachs Small/Mid Cap Growth Fund | 246,893 | Feb 27, 2019 | 0.77% | 2,170,189 |
| Vanguard Total Stock Market Index Fund | 211,239 | Dec 30, 2018 | 0.66% | 2,748,219 |
| iShares Russell 2000 Value ETF | 100,084 | Jun 29, 2019 | 0.31% | 898,754 |
| Vanguard Extended Market Index Fund | 61,795 | Dec 30, 2018 | 0.19% | 803,952 |
| Fidelity Select Portfolios - Biotechnology | 61,300 | Jun 29, 2019 | 0.19% | 550,474 |
| Fidelity Small Cap Index Fund | 54,034 | Apr 29, 2019 | 0.17% | 453,075 |
| Victory Portfolios-Victory RS Science & Technology Fund | 38,470 | Dec 30, 2018 | 0.12% | 500,494 |