BLUE bluebird bio Inc

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14D-9

SOLICITATION/RECOMMENDATION STATEMENT

PURSUANT TO SECTION 14(d)(4) OF THE SECURITIES EXCHANGE ACT OF 1934

bluebird bio, Inc.

(Name of Subject Company)

bluebird bio, Inc.

(Name of Person(s) Filing Statement)

Common Stock, $0.01 par value per share

(Title of Class of Securities)

09609G 209

(CUSIP Number of Common Stock)

Andrew Obenshain

President and Chief Executive Officer

bluebird bio, Inc.

455 Grand Union Boulevard

Somerville, Massachusetts 02145

(339) 499-9300

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications

on Behalf of the Person(s) Filing Statement)

With a copy to:

R. Scott Shean

Andrew Clark

Brian R. Umanoff

Latham & Watkins LLP

650 Town Center Drive, 20^th Floor

Boston, Massachusetts 92626

(714) 540-1235

This Schedule 14D-9C consists of the following documents related to the proposed acquisition of bluebird bio, Inc., a Delaware corporation (the “Company” or “bluebird bio”), pursuant to an Agreement and Plan of Merger, dated as of February 21, 2025, by and among Beacon Parent Holdings, L.P., a Delaware limited partnership (“Parent”), and Beacon Merger Sub, Inc., a Delaware corporation and an indirect wholly owned subsidiary of Parent (“Merger Sub”).

ADDITIONAL INFORMATION AND WHERE TO FIND IT

The tender offer for the outstanding shares of bluebird bio referenced in this communication has not yet commenced. This communication is not an offer to buy nor a solicitation of an offer to sell any securities of bluebird bio. The solicitation and the offer to buy shares of bluebird bio common stock will only be made pursuant to a Tender Offer Statement on Schedule TO, including an offer to purchase, a letter of transmittal and other related materials that Parent and Merger Sub intend to file with the Securities and Exchange Commission. In addition, bluebird bio will file with the SEC a Solicitation/Recommendation Statement on Schedule 14D-9 with respect to the tender offer. Once filed, investors will be able to obtain a free copy of these materials and other documents filed by Parent, Merger Sub and bluebird bio with the SEC at the website maintained by the SEC at www.sec.gov. Investors may also obtain, at no charge, any such documents filed with or furnished to the SEC by bluebird bio under the “investors & media” section of bluebird bio’s website at www.bluebirdbio.com.

INVESTORS AND SECURITY HOLDERS ARE ADVISED TO READ THESE DOCUMENTS WHEN THEY BECOME AVAILABLE, INCLUDING THE SOLICITATION/RECOMMENDATION STATEMENT OF BLUEBIRD BIO AND ANY AMENDMENTS THERETO, AS WELL AS ANY OTHER DOCUMENTS RELATING TO THE TENDER OFFER AND THE MERGER THAT ARE FILED WITH THE SEC, CAREFULLY AND IN THEIR ENTIRETY PRIOR TO MAKING ANY DECISIONS WITH RESPECT TO WHETHER TO TENDER THEIR SHARES INTO THE TENDER OFFER BECAUSE THEY CONTAIN IMPORTANT INFORMATION, INCLUDING THE TERMS AND CONDITIONS OF THE TENDER OFFER.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

The statements included above that are not a description of historical facts are forward-looking statements. Words or phrases such as “believe,” “may,” “could,” “will,” “estimate,” “continue,” “anticipate,” “intend,” “seek,” “plan,” “expect,” “should,” “would” or similar expressions are intended to identify forward-looking statements. The forward-looking statements are based on bluebird bio’s current beliefs and expectations and include, but are not limited to: statements regarding beliefs about the potential benefits of the transaction, the planned completion and timing of the transactions contemplated by the Merger Agreement; and the prospective performance and outlook of the surviving company’s business, performance, and opportunities. Risks and uncertainties that could cause results to differ from expectations include: uncertainties as to the timing and completion of the tender offer and the merger; uncertainties as to the percentage of bluebird bio stockholders tendering their shares in the tender offer; the possibility that competing offers will be made; the possibility that various closing conditions for the tender offer or the merger may not be satisfied or waived, including the failure to receive any required regulatory approvals from

any applicable regulatory and/or governmental entities (or any conditions, limitations or restrictions placed on such approvals); risks relating to bluebird bio’s liquidity during the pendency of the tender offer and the merger or in the event of a termination of the Merger Agreement; the risk that the milestone related to the contingent value right is not achieved; the effects of disruption caused by the transaction making it more difficult to maintain relationships with employees, collaborators, vendors and other business partners; risks related to diverting management’s attention from bluebird bio’s ongoing business operations; the risk that stockholder litigation in connection with the transactions contemplated by the Merger Agreement may result in significant costs of defense, indemnification and liability; and other risks and uncertainties pertaining to bluebird bio’s business, including the risks and uncertainties detailed in bluebird bio’s public periodic filings with the SEC, as well as the tender offer materials to be filed by Parent and Merger Sub and the Solicitation/Recommendation Statement to be filed by bluebird bio in connection with the tender offer.

You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement and bluebird bio undertakes no obligation to revise or update these statements to reflect events or circumstances after the date hereof, except as required by law.

Exhibit 99.1

IR WEBSITE FAQ – for website

What is the timing to complete the transaction and when can shareholders expect to get paid out?

Does bluebird have enough cash runway to make it to close of the transaction?

Where can I find Tender Offer materials?

How many shares need to be tendered for this transaction to be approved?

What happens if bluebird does not receive shareholder support for this transaction?

ADDITIONAL INFORMATION AND WHERE TO FIND IT

The tender offer for the outstanding shares of bluebird bio referenced in this communication has not yet commenced. This communication is not an offer to buy nor a solicitation of an offer to sell any securities of bluebird bio. The solicitation and the offer to buy shares of bluebird bio common stock will only be made pursuant to a Tender Offer Statement on Schedule TO, including an offer to purchase, a letter of transmittal and other related materials that Beacon Parent Holdings, L.P. (“Parent”) and Beacon Merger Sub, Inc. (“Merger Sub”) intend to file with the Securities and

Exchange Commission. In addition, bluebird bio will file with the SEC a Solicitation/Recommendation Statement on Schedule 14D-9 with respect to the tender offer. Once filed, investors will be able to obtain a free copy of these materials and other documents filed by Parent, Merger Sub and bluebird bio with the SEC at the website maintained by the SEC at www.sec.gov. Investors may also obtain, at no charge, any such documents filed with or furnished to the SEC by bluebird bio under the “investors & media” section of bluebird bio’s website at www.bluebirdbio.com.

INVESTORS AND SECURITY HOLDERS ARE ADVISED TO READ THESE DOCUMENTS WHEN THEY BECOME AVAILABLE, INCLUDING THE SOLICITATION/RECOMMENDATION STATEMENT ON SCHEDULE 14D-9 OF BLUEBIRD BIO AND ANY AMENDMENTS THERETO, AS WELL AS ANY OTHER DOCUMENTS RELATING TO THE TENDER OFFER AND THE MERGER THAT ARE FILED WITH THE SEC, CAREFULLY AND IN THEIR ENTIRETY PRIOR TO MAKING ANY DECISIONS WITH RESPECT TO WHETHER TO TENDER THEIR SHARES INTO THE TENDER OFFER BECAUSE THEY CONTAIN IMPORTANT INFORMATION, INCLUDING THE TERMS AND CONDITIONS OF THE TENDER OFFER.

Forward-Looking Statements

The statements included above that are not a description of historical facts are forward-looking statements. Words or phrases such as “believe,” “may,” “could,” “will,” “estimate,” “continue,” “anticipate,” “intend,” “seek,” “plan,” “expect,” “should,” “would” or similar expressions are intended to identify forward-looking statements. The forward-looking statements are based on bluebird bio’s current beliefs and expectations and include, but are not limited to: statements regarding beliefs about the potential benefits of the transaction; the planned completion and timing of the transactions contemplated by the Merger Agreement ; and the prospective performance and outlook of the surviving company’s business, performance, and opportunities. Risks and uncertainties that could cause results to differ from expectations include: uncertainties as to the timing and completion of the tender offer and the merger; uncertainties as to the percentage of bluebird bio stockholders tendering their shares in the tender offer; the possibility that competing offers will be made; the possibility that various closing conditions for the tender offer or the merger may not be satisfied or waived, including the failure to receive any required regulatory approvals from any applicable regulatory and/or governmental entities (or any conditions, limitations or restrictions placed on such approvals); risks relating to bluebird bio’s liquidity during the pendency of the tender offer and the merger or in the event of a termination of the Merger Agreement; the risk that the milestone related to the contingent value right is not achieved; the effects of disruption caused by the transaction making it more difficult to maintain relationships with employees, collaborators, vendors and other business partners; risks related to diverting management’s attention from bluebird bio’s ongoing business operations; the risk that stockholder litigation in connection with the transactions contemplated by the Merger Agreement may result in significant costs of defense, indemnification and liability; and other risks and uncertainties pertaining to bluebird bio’s business, including the risks and uncertainties detailed in bluebird bio’s public periodic filings with the SEC, as well as the tender offer materials to be filed by Parent and Merger Sub and the Solicitation/Recommendation Statement on Schedule 14D-9 to be filed by bluebird bio in connection with the tender offer.

You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement and bluebird bio undertakes no obligation to revise or update these statements to reflect events or circumstances after the date hereof, except as required by law.

Exhibit 99.2

Beacon All Birds Email

Birds,

Since bluebird set out as an independent company in 2021, we have made remarkable strides to advance gene therapy, transform the lives of countless patients and families, and push the boundaries of what is possible in medicine—overcoming countless challenges along the way.

Those headwinds continue today—for bluebird and the field of gene therapy more broadly—which has made securing additional cash resources a longer process than originally anticipated.

I’m pleased to share that after a months-long strategic review process that involved meeting with more than 70 potential partners, today we announced a definitive agreement to be acquired and taken private by Carlyle and SK Capital—two leading investment organizations.

This is a significant and positive step forward that will enable bluebird to maintain operations, secure long-term access to bluebird therapies for patients, and maximize value for stockholders. It also marks the start of a new chapter for the flock. In addition to providing financial resources, Carlyle and SK Capital have engaged a group of highly experienced biotech executives led by David Meek (former CEO of Mirati Therapeutics, FerGene, and Ipsen and current Chairman of Sobi and uniQure) to support bluebird’s continued growth. It is expected that David will step into the role of bluebird CEO upon closing, which is expected to be in the first half of this year (subject to the tender of a majority of the outstanding shares of bluebird, receipt of applicable regulatory approvals, and other customary closing conditions). Additional details on this agreement are available in our press release here.

I remain incredibly proud of this team and all we have accomplished together.. Onward.

Andrew

# # #

ADDITIONAL INFORMATION AND WHERE TO FIND IT

The tender offer for the outstanding shares of bluebird bio referenced in this communication has not yet commenced. This communication is not an offer to buy nor a solicitation of an offer to sell any securities of bluebird bio. The solicitation and the offer to buy shares of bluebird bio common stock will only be made pursuant to a Tender Offer Statement on Schedule TO, including an offer to purchase, a letter of transmittal and other related materials that Beacon Parent Holdings, L.P. (“Parent”) and Beacon Merger Sub, Inc. (“Merger Sub”) intend to file with the Securities and Exchange Commission. In addition, bluebird bio will file with the SEC a Solicitation/Recommendation Statement on Schedule 14D-9 with respect to the tender offer. Once filed, investors will be able to obtain a free copy of these materials and other documents filed by Parent, Merger Sub and bluebird bio with the SEC at the website maintained by the SEC at www.sec.gov. Investors may also obtain, at no charge, any such documents filed with or furnished to the SEC by bluebird bio under the “investors & media” section of bluebird bio’s website at www.bluebirdbio.com.

INVESTORS AND SECURITY HOLDERS ARE ADVISED TO READ THESE DOCUMENTS WHEN THEY BECOME AVAILABLE, INCLUDING THE SOLICITATION/RECOMMENDATION STATEMENT ON SCHEDULE 14D-9 OF BLUEBIRD BIO AND ANY AMENDMENTS THERETO, AS WELL AS ANY OTHER DOCUMENTS RELATING TO THE TENDER OFFER AND THE MERGER THAT ARE FILED WITH THE SEC, CAREFULLY AND IN THEIR ENTIRETY PRIOR TO MAKING ANY DECISIONS WITH RESPECT TO WHETHER TO TENDER THEIR SHARES INTO THE TENDER OFFER BECAUSE THEY CONTAIN IMPORTANT INFORMATION, INCLUDING THE TERMS AND CONDITIONS OF THE TENDER OFFER.

Forward-Looking Statements

The statements included above that are not a description of historical facts are forward-looking statements. Words or phrases such as “believe,” “may,” “could,” “will,” “estimate,” “continue,” “anticipate,” “intend,” “seek,” “plan,” “expect,” “should,” “would” or similar expressions are intended to identify forward-looking statements. The forward-looking statements are based on bluebird bio’s current beliefs and expectations and include, but are not limited to: statements regarding beliefs about the potential benefits of the transaction; the planned completion and timing of the transactions contemplated by the Merger Agreement; and the prospective performance and outlook of the surviving company’s business, performance, and opportunities. Risks and uncertainties that could cause results to differ from expectations include: uncertainties as to the timing and completion of the tender offer and the merger; uncertainties as to the percentage of bluebird bio stockholders tendering their shares in the tender offer; the possibility that competing offers will be made; the possibility that various closing conditions for the tender offer or the merger may not be satisfied or waived, including the failure to receive any required regulatory approvals from any applicable regulatory and/or governmental entities (or any conditions, limitations or restrictions placed on such approvals); risks relating to bluebird bio’s liquidity during the pendency of the tender offer and the merger or in the event of a termination of the Merger Agreement; the risk that the milestone related to the contingent value right is not achieved; the effects of disruption caused by the transaction making it more difficult to maintain relationships with employees, collaborators, vendors and other business partners; risks related to diverting management’s attention from bluebird bio’s ongoing business operations; the risk that stockholder litigation in connection with the transactions contemplated by the Merger Agreement may result in significant costs of defense, indemnification and liability; and other risks and uncertainties pertaining to bluebird bio’s business, including the risks and uncertainties detailed in bluebird bio’s public periodic filings with the SEC, as well as the tender offer materials to be filed by Parent and Merger Sub and the Solicitation/Recommendation Statement on Schedule 14D-9 to be filed by bluebird bio in connection with the tender offer.

You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement and bluebird bio undertakes no obligation to revise or update these statements to reflect events or circumstances after the date hereof, except as required by law.

Exhibit 99.3

Beacon - Proactive email from Tom Klima to QTC accounts

Hi [name],

Today bluebird announced that the company has entered into an agreement to be acquired and taken private by Carlyle and SK Capital. This marks a significant and positive step forward in our collaboration with Qualified Treatment Centers to bring potentially curative gene therapies to patients.

The agreement will enable investment in activities with the potential to expand access and improve the gene therapy treatment experience for both patients and providers.

It is expected that the company will have new leadership upon closing, with David Meek expected to step into the position of CEO. I will remain in place as chief commercial officer to help guide the continued acceleration of our launches. David is the former CEO of Mirati Therapeutics, FerGene, and Ipsen; and the current Chairman of Sobi and uniQure. I am confident that the anticipated incoming management team will be well equipped to navigate the challenges of delivering gene therapy in a commercial setting and will continue to improve and advance our vital work together—potentially allowing significantly more patients the opportunity for life-changing treatment.

We anticipate these changes will be formalized in the first half of this year, when the acquisition is expected to close, and will share additional updates at that time. In the meantime, we are continuing full steam ahead to treat patients and all activities related to therapeutic manufacturing and ongoing patient care will continue as usual. Please do not hesitate to reach out to your QTAL with any questions.

Thank you for your ongoing partnership.

[Signature]

# # #

ADDITIONAL INFORMATION AND WHERE TO FIND IT

The tender offer for the outstanding shares of bluebird bio referenced in this communication has not yet commenced. This communication is not an offer to buy nor a solicitation of an offer to sell any securities of bluebird bio. The solicitation and the offer to buy shares of bluebird bio common stock will only be made pursuant to a Tender Offer Statement on Schedule TO, including an offer to purchase, a letter of transmittal and other related materials that Beacon Parent Holdings, L.P. (“Parent”) and Beacon Merger Sub, Inc. (“Merger Sub”) intend to file with the SEC. In addition, bluebird bio will file with the SEC a Solicitation/Recommendation Statement on Schedule 14D-9 with respect to the tender offer. Once filed, investors will be able to obtain a free copy of these materials and other documents filed by Parent, Merger Sub and bluebird bio with the SEC at the website maintained by the SEC at www.sec.gov. Investors may also obtain, at no charge, any such documents filed with or furnished to the SEC by bluebird bio under the “investors & media” section of bluebird bio’s website at www.bluebirdbio.com.

INVESTORS AND SECURITY HOLDERS ARE ADVISED TO READ THESE DOCUMENTS WHEN THEY BECOME AVAILABLE, INCLUDING THE SOLICITATION/RECOMMENDATION STATEMENT ON SCHEDULE 14D-9 OF BLUEBIRD BIO AND ANY AMENDMENTS THERETO, AS WELL AS ANY OTHER DOCUMENTS RELATING TO THE TENDER OFFER AND THE MERGER THAT ARE FILED WITH THE SEC, CAREFULLY AND IN THEIR ENTIRETY PRIOR TO MAKING ANY DECISIONS WITH RESPECT TO WHETHER TO TENDER THEIR SHARES INTO THE TENDER OFFER BECAUSE THEY CONTAIN IMPORTANT INFORMATION, INCLUDING THE TERMS AND CONDITIONS OF THE TENDER OFFER.

Forward-Looking Statements

The statements included above that are not a description of historical facts are forward-looking statements. Words or phrases such as “believe,” “may,” “could,” “will,” “estimate,” “continue,” “anticipate,” “intend,” “seek,” “plan,” “expect,” “should,” “would” or similar expressions are intended to identify forward-looking statements. The forward-looking statements are based on bluebird bio’s current beliefs and expectations and include, but are not limited to: statements regarding beliefs about the potential benefits of the transaction; the planned completion and timing of the transactions contemplated by the Merger Agreement; and the prospective performance and outlook of the surviving company’s business, performance, and opportunities. Risks and uncertainties that could cause results to differ from expectations include: uncertainties as to the timing and completion of the tender offer and the merger; uncertainties as to the percentage of bluebird bio stockholders tendering their shares in the tender offer; the possibility that competing offers will be made; the possibility that various closing conditions for the tender offer or the merger may not be satisfied or waived, including the failure to receive any required regulatory approvals from any applicable regulatory and/or governmental entities (or any conditions, limitations or restrictions placed on such approvals); risks relating to bluebird bio’s liquidity during the pendency of the tender offer and the merger or in the event of a termination of the Merger Agreement; the risk that the milestone related to the contingent value right is not achieved; the effects of disruption caused by the transaction making it more difficult to maintain relationships with employees, collaborators, vendors and other business partners; risks related to diverting management’s attention from bluebird bio’s ongoing business operations; the risk that stockholder litigation in connection with the transactions contemplated by the Merger Agreement may result in significant costs of defense, indemnification and liability; and other risks and uncertainties pertaining to bluebird bio’s business, including the risks and uncertainties detailed in bluebird bio’s public periodic filings with the SEC, as well as the tender offer materials to be filed by Parent and Merger Sub and the Solicitation/Recommendation Statement on Schedule 14D-9 to be filed by bluebird bio in connection with the tender offer.

You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement and bluebird bio undertakes no obligation to revise or update these statements to reflect events or circumstances after the date hereof, except as required by law.

Exhibit 99.4

Proactive email for CMC vendors

Hello [—]

As a follow up to multiple discussions we’ve had over the last few months, I wanted to make sure that you were aware of an important announcement that bluebird made earlier today. In short, we have entered into an agreement to be acquired and taken private by Carlyle and SK Capital. This marks a significant and positive step in our journey to bring life-changing gene therapies to patients impacted by severe genetic diseases, as Carlyle and SK Capital will provide bluebird primary capital to scale bluebird’s commercial delivery of gene therapies.

We expect that, upon closing, David Meek – the former CEO of Mirati Therapeutics, FerGene, and Ipsen and current Chairman of Sobi and uniQure – will step into the role of CEO. I would value the chance to walk you through some of the implications of this announcement and appreciate if you can offer a few time slots today or tomorrow for a short call.

While this update does not impact ongoing critical delivery activities, it is likely that there will be some meetings cancelled or moved today as we complete internal communications. We might need to ask for a little grace as we ensure that information is shared and processed internally.

Thank you for your continued collaboration and commitment to our shared mission for patients.

# # #

ADDITIONAL INFORMATION AND WHERE TO FIND IT

The tender offer for the outstanding shares of bluebird bio referenced in this communication has not yet commenced. This communication is not an offer to buy nor a solicitation of an offer to sell any securities of bluebird bio. The solicitation and the offer to buy shares of bluebird bio common stock will only be made pursuant to a Tender Offer Statement on Schedule TO, including an offer to purchase, a letter of transmittal and other related materials that Beacon Parent Holdings, L.P. (“Parent”) and Beacon Merger Sub, Inc. (“Merger Sub”) intend to file with the Securities and Exchange Commission. In addition, bluebird bio will file with the SEC a Solicitation/Recommendation Statement on Schedule 14D-9 with respect to the tender offer. Once filed, investors will be able to obtain a free copy of these materials and other documents filed by Parent, Merger Sub and bluebird bio with the SEC at the website maintained by the SEC at www.sec.gov. Investors may also obtain, at no charge, any such documents filed with or furnished to the SEC by bluebird bio under the “investors & media” section of bluebird bio’s website at www.bluebirdbio.com.

INVESTORS AND SECURITY HOLDERS ARE ADVISED TO READ THESE DOCUMENTS WHEN THEY BECOME AVAILABLE, INCLUDING THE SOLICITATION/RECOMMENDATION STATEMENT ON SCHEDULE 14D-9 OF BLUEBIRD BIO AND ANY AMENDMENTS THERETO, AS WELL AS ANY OTHER DOCUMENTS RELATING TO THE TENDER OFFER AND THE MERGER THAT ARE FILED WITH THE SEC, CAREFULLY AND IN THEIR ENTIRETY PRIOR TO MAKING ANY DECISIONS WITH RESPECT TO WHETHER TO TENDER THEIR SHARES INTO THE TENDER OFFER BECAUSE THEY CONTAIN IMPORTANT INFORMATION, INCLUDING THE TERMS AND CONDITIONS OF THE TENDER OFFER.

Forward-Looking Statements

The statements included above that are not a description of historical facts are forward-looking statements. Words or phrases such as “believe,” “may,” “could,” “will,” “estimate,” “continue,” “anticipate,” “intend,” “seek,” “plan,” “expect,” “should,” “would” or similar expressions are intended to identify forward-looking statements. The forward-looking statements are based on bluebird bio’s current beliefs and expectations and include, but are not limited to: statements regarding beliefs about the potential benefits of the transaction; the planned completion and timing of the transactions contemplated by the Merger Agreement; and the prospective performance and outlook of the surviving company’s business, performance, and opportunities. Risks and uncertainties that could cause results to differ from expectations include: uncertainties as to the timing and completion of the tender offer and the merger; uncertainties as to the percentage of bluebird bio stockholders tendering their shares in the tender offer; the possibility that competing offers will be made; the possibility that various closing conditions for the tender offer or the merger may not be satisfied or waived, including the failure to receive any required regulatory approvals from any applicable regulatory and/or governmental entities (or any conditions, limitations or restrictions placed on such approvals); risks relating to bluebird bio’s liquidity during the pendency of the tender offer and the merger or in the event of a termination of the Merger Agreement; the risk that the milestone related to the contingent value right is not achieved; the effects of disruption caused by the transaction making it more difficult to maintain relationships with employees, collaborators, vendors and other business partners; risks related to diverting management’s attention from bluebird bio’s ongoing business operations; the risk that stockholder litigation in connection with the transactions contemplated by the Merger Agreement may result in significant costs of defense, indemnification and liability; and other risks and uncertainties pertaining to bluebird bio’s business, including the risks and uncertainties detailed in bluebird bio’s public periodic filings with the SEC, as well as the tender offer materials to be filed by Parent and Merger Sub and the Solicitation/Recommendation Statement on Schedule 14D-9 to be filed by bluebird bio in connection with the tender offer.

You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement and bluebird bio undertakes no obligation to revise or update these statements to reflect events or circumstances after the date hereof, except as required by law.

Exhibit 99.5

Proactive Email to National PAO Leaders

Hi [name]

I’m reaching out to share an update from our team at bluebird: the company has entered into an agreement to be acquired and taken private by a team of highly experienced biotechnology investors and executives. This is significant and positive step forward in bluebird’s mission to bring potentially transformative therapies to patients impacted by severe genetic diseases.

This new chapter is expected to bring financial stability and additional investments to expand access and improve the gene therapy experience for patients and families. While this will mean changes for bluebird, including a new leadership team expected to be headed by David Meek as CEO, our commitment to patient access and partnering with the [CALD/beta-thalassemia/sickle cell disease community] remains as strong as ever and all activities related to treatment manufacturing and patient care will continue as usual.

David has offered to join an upcoming monthly call to discuss their vision for expanding access to gene therapies and their commitment to the [CALD/beta-thalassemia/sickle cell disease community] and answer questions you may have—please let me know if you would like me to coordinate that discussion. Feel free to call me directly if you have any questions or concerns.

Thank you,

Tonya

ADDITIONAL INFORMATION AND WHERE TO FIND IT

The tender offer for the outstanding shares of bluebird bio referenced in this communication has not yet commenced. This communication is not an offer to buy nor a solicitation of an offer to sell any securities of bluebird bio. The solicitation and the offer to buy shares of bluebird bio common stock will only be made pursuant to a Tender Offer Statement on Schedule TO, including an offer to purchase, a letter of transmittal and other related materials that Beacon Parent Holdings, L.P. (“Parent”) and Beacon Merger Sub, Inc. (“Merger Sub”) intend to file with the Securities and Exchange Commission. In addition, bluebird bio will file with the SEC a Solicitation/Recommendation Statement on Schedule 14D-9 with respect to the tender offer. Once filed, investors will be able to obtain a free copy of these materials and other documents filed by Parent, Merger Sub and bluebird bio with the SEC at the website maintained by the SEC at www.sec.gov. Investors may also obtain, at no charge, any such documents filed with or furnished to the SEC by bluebird bio under the “investors & media” section of bluebird bio’s website at www.bluebirdbio.com.

INVESTORS AND SECURITY HOLDERS ARE ADVISED TO READ THESE DOCUMENTS WHEN THEY BECOME AVAILABLE, INCLUDING THE SOLICITATION/RECOMMENDATION STATEMENT ON SCHEDULE 14D-9 OF BLUEBIRD BIO AND ANY AMENDMENTS THERETO, AS WELL AS ANY OTHER DOCUMENTS RELATING TO THE TENDER OFFER AND THE MERGER THAT ARE FILED WITH THE SEC, CAREFULLY AND IN THEIR ENTIRETY PRIOR TO MAKING ANY DECISIONS WITH RESPECT TO WHETHER TO TENDER THEIR SHARES INTO THE TENDER OFFER BECAUSE THEY CONTAIN IMPORTANT INFORMATION, INCLUDING THE TERMS AND CONDITIONS OF THE TENDER OFFER.

Forward-Looking Statements

The statements included above that are not a description of historical facts are forward-looking statements. Words or phrases such as “believe,” “may,” “could,” “will,” “estimate,” “continue,” “anticipate,” “intend,” “seek,” “plan,” “expect,” “should,” “would” or similar expressions are intended to identify forward-looking statements. The forward-looking statements are based on bluebird bio’s current beliefs and expectations and include, but are not limited to: statements regarding beliefs about the potential benefits of the transaction; the planned completion and timing of the transactions contemplated by the Merger Agreement; and the prospective performance and outlook of the surviving company’s business, performance, and opportunities. Risks and uncertainties that could cause results to differ from expectations include: uncertainties as to the timing and completion of the tender offer and the merger; uncertainties as to the percentage of bluebird bio stockholders tendering their shares in the tender offer; the possibility that competing offers will be made; the possibility that various closing conditions for the tender offer or the merger may not be satisfied or waived, including the failure to receive any required regulatory approvals from any applicable regulatory and/or governmental entities (or any conditions, limitations or restrictions placed on such approvals); risks relating to bluebird bio’s liquidity during the pendency of the tender offer and the merger or in the event of a termination of the Merger Agreement; the risk that the milestone related to the contingent value right is not achieved; the effects of disruption caused by the transaction making it more difficult to maintain relationships with employees, collaborators, vendors and other business partners; risks related to diverting management’s attention from bluebird bio’s ongoing business operations; the risk that stockholder litigation in connection with the transactions contemplated by the Merger Agreement may result in significant costs of defense, indemnification and liability; and other risks and uncertainties pertaining to bluebird bio’s business, including the risks and uncertainties detailed in bluebird bio’s public periodic filings with the SEC, as well as the tender offer materials to be filed by Parent and Merger Sub and the Solicitation/Recommendation Statement on Schedule 14D-9 to be filed by bluebird bio in connection with the tender offer.

You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement and bluebird bio undertakes no obligation to revise or update these statements to reflect events or circumstances after the date hereof, except as required by law.

Exhibit 99.6

Proactive Email to Payers [For use at NAE discretion]

Hi [name] –

Today bluebird announced it has entered into an agreement to be acquired and taken private by Carlyle and SK Capital, in collaboration with a team of highly experienced biotechnology executives. This is significant and positive step forward in bluebird’s mission to bring potentially transformative therapies to patients impacted by severe genetic diseases.

While this agreement marks a new chapter for the company, I wanted to reach out personally to let you know that our commitment to patient access and to our partnership with [company name] remains unchanged. We do not anticipate any immediate changes to our day-to-day processes related to patient access and all activities related to manufacturing and patient care will continue as usual.

Please don’t hesitate to reach out if you have any questions.

Best,

[insert signature]

ADDITIONAL INFORMATION AND WHERE TO FIND IT

The tender offer for the outstanding shares of bluebird bio referenced in this communication has not yet commenced. This communication is not an offer to buy nor a solicitation of an offer to sell any securities of bluebird bio. The solicitation and the offer to buy shares of bluebird bio common stock will only be made pursuant to a Tender Offer Statement on Schedule TO, including an offer to purchase, a letter of transmittal and other related materials that Beacon Parent Holdings, L.P. (“Parent”) and Beacon Merger Sub, Inc. (“Merger Sub”) intend to file with the Securities and Exchange Commission. In addition, bluebird bio will file with the SEC a Solicitation/Recommendation Statement on Schedule 14D-9 with respect to the tender offer. Once filed, investors will be able to obtain a free copy of these materials and other documents filed by Parent, Merger Sub and bluebird bio with the SEC at the website maintained by the SEC at www.sec.gov. Investors may also obtain, at no charge, any such documents filed with or furnished to the SEC by bluebird bio under the “investors & media” section of bluebird bio’s website at www.bluebirdbio.com.

INVESTORS AND SECURITY HOLDERS ARE ADVISED TO READ THESE DOCUMENTS WHEN THEY BECOME AVAILABLE, INCLUDING THE SOLICITATION/RECOMMENDATION STATEMENT ON SCHEDULE 14D-9 OF BLUEBIRD BIO AND ANY AMENDMENTS THERETO, AS WELL AS ANY OTHER DOCUMENTS RELATING TO THE TENDER OFFER AND THE MERGER THAT ARE FILED WITH THE SEC, CAREFULLY AND IN THEIR ENTIRETY PRIOR TO MAKING ANY DECISIONS WITH RESPECT TO WHETHER TO TENDER THEIR SHARES INTO THE TENDER OFFER BECAUSE THEY CONTAIN IMPORTANT INFORMATION, INCLUDING THE TERMS AND CONDITIONS OF THE TENDER OFFER.

Forward-Looking Statements

The statements included above that are not a description of historical facts are forward-looking statements. Words or phrases such as “believe,” “may,” “could,” “will,” “estimate,” “continue,” “anticipate,” “intend,” “seek,” “plan,” “expect,” “should,” “would” or similar expressions are intended to identify forward-looking statements. The forward-looking statements are based on bluebird bio’s current beliefs and expectations and include, but are not limited to: statements regarding beliefs about the potential benefits of the transaction; the planned

completion and timing of the transactions contemplated by the Merger Agreement; and the prospective performance and outlook of the surviving company’s business, performance, and opportunities. Risks and uncertainties that could cause results to differ from expectations include: uncertainties as to the timing and completion of the tender offer and the merger; uncertainties as to the percentage of bluebird bio stockholders tendering their shares in the tender offer; the possibility that competing offers will be made; the possibility that various closing conditions for the tender offer or the merger may not be satisfied or waived, including the failure to receive any required regulatory approvals from any applicable regulatory and/or governmental entities (or any conditions, limitations or restrictions placed on such approvals); risks relating to bluebird bio’s liquidity during the pendency of the tender offer and the merger or in the event of a termination of the Merger Agreement; the risk that the milestone related to the contingent value right is not achieved; the effects of disruption caused by the transaction making it more difficult to maintain relationships with employees, collaborators, vendors and other business partners; risks related to diverting management’s attention from bluebird bio’s ongoing business operations; the risk that stockholder litigation in connection with the transactions contemplated by the Merger Agreement may result in significant costs of defense, indemnification and liability; and other risks and uncertainties pertaining to bluebird bio’s business, including the risks and uncertainties detailed in bluebird bio’s public periodic filings with the SEC, as well as the tender offer materials to be filed by Parent and Merger Sub and the Solicitation/Recommendation Statement on Schedule 14D-9 to be filed by bluebird bio in connection with the tender offer.

You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement and bluebird bio undertakes no obligation to revise or update these statements to reflect events or circumstances after the date hereof, except as required by law.

Exhibit 99.7

To be posted on LinkedIn, Twitter

Today bluebird bio announced a definitive agreement to be acquired by Carlyle and SK Capital. Read more in our press release: [insert link]

ADDITIONAL INFORMATION AND WHERE TO FIND IT

The tender offer for the outstanding shares of bluebird bio referenced in this communication has not yet commenced. This communication is not an offer to buy nor a solicitation of an offer to sell any securities of bluebird bio. The solicitation and the offer to buy shares of bluebird bio common stock will only be made pursuant to a Tender Offer Statement on Schedule TO, including an offer to purchase, a letter of transmittal and other related materials that Beacon Parent Holdings, L.P. (“Parent”) and Beacon Merger Sub, Inc. (“Merger Sub”) intend to file with the Securities and Exchange Commission. In addition, bluebird bio will file with the SEC a Solicitation/Recommendation Statement on Schedule 14D-9 with respect to the tender offer. Once filed, investors will be able to obtain a free copy of these materials and other documents filed by Parent, Merger Sub and bluebird bio with the SEC at the website maintained by the SEC at www.sec.gov. Investors may also obtain, at no charge, any such documents filed with or furnished to the SEC by bluebird bio under the “investors & media” section of bluebird bio’s website at www.bluebirdbio.com.

INVESTORS AND SECURITY HOLDERS ARE ADVISED TO READ THESE DOCUMENTS WHEN THEY BECOME AVAILABLE, INCLUDING THE SOLICITATION/RECOMMENDATION STATEMENT ON SCHEDULE 14D-9 OF BLUEBIRD BIO AND ANY AMENDMENTS THERETO, AS WELL AS ANY OTHER DOCUMENTS RELATING TO THE TENDER OFFER AND THE MERGER THAT ARE FILED WITH THE SEC, CAREFULLY AND IN THEIR ENTIRETY PRIOR TO MAKING ANY DECISIONS WITH RESPECT TO WHETHER TO TENDER THEIR SHARES INTO THE TENDER OFFER BECAUSE THEY CONTAIN IMPORTANT INFORMATION, INCLUDING THE TERMS AND CONDITIONS OF THE TENDER OFFER.

Forward-Looking Statements

The statements included above that are not a description of historical facts are forward-looking statements. Words or phrases such as “believe,” “may,” “could,” “will,” “estimate,” “continue,” “anticipate,” “intend,” “seek,” “plan,” “expect,” “should,” “would” or similar expressions are intended to identify forward-looking statements. The forward-looking statements are based on bluebird bio’s current beliefs and expectations and include, but are not limited to: statements regarding beliefs about the potential benefits of the transaction; the planned completion and timing of the transactions contemplated by the Merger Agreement; and the prospective performance and outlook of the surviving company’s business, performance, and opportunities. Risks and uncertainties that could cause results to differ from expectations include: uncertainties as to the timing and

completion of the tender offer and the merger; uncertainties as to the percentage of bluebird bio stockholders tendering their shares in the tender offer; the possibility that competing offers will be made; the possibility that various closing conditions for the tender offer or the merger may not be satisfied or waived, including the failure to receive any required regulatory approvals from any applicable regulatory and/or governmental entities (or any conditions, limitations or restrictions placed on such approvals); risks relating to bluebird bio’s liquidity during the pendency of the tender offer and the merger or in the event of a termination of the Merger Agreement; the risk that the milestone related to the contingent value right is not achieved; the effects of disruption caused by the transaction making it more difficult to maintain relationships with employees, collaborators, vendors and other business partners; risks related to diverting management’s attention from bluebird bio’s ongoing business operations; the risk that stockholder litigation in connection with the transactions contemplated by the Merger Agreement may result in significant costs of defense, indemnification and liability; and other risks and uncertainties pertaining to bluebird bio’s business, including the risks and uncertainties detailed in bluebird bio’s public periodic filings with the SEC, as well as the tender offer materials to be filed by Parent and Merger Sub and the Solicitation/Recommendation Statement on Schedule 14D-9 to be filed by bluebird bio in connection with the tender offer.

You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement and bluebird bio undertakes no obligation to revise or update these statements to reflect events or circumstances after the date hereof, except as required by law.