bluebird bio, Inc.
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Common Stock, $0.01 par value per share
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09609G100
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December 31, 2014
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CUSIP No. 09609G100
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13G
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Page 2 of 5
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Item 3.
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If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
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CUSIP No. 09609G100
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13G
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Page 3 of 5
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By:
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THIRD ROCK VENTURES GP, L.P.
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General Partner
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By:
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TRV GP, LLC
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By:
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TRV GP, LLC
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*
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CUSIP No. 09609G100
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13G
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Page 4 of 5
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By:
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THIRD ROCK VENTURES GP, L.P.
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General Partner
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By:
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TRV GP, LLC
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By:
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TRV GP, LLC
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*
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CUSIP No. 09609G100
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13G
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Page 5 of 5
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