PhaseBio Pharmaceuticals to Host Investor Call to Discuss Interim Results from Pivotal REVERSE-IT Phase 3 Trial Presented at the American Heart Association Annual Meeting

Prespecified interim analysis of pivotal REVERSE-IT Phase 3 trial to be presented during late-breaking science session on November 15th at the American Heart Association's Scientific Sessions 2021

Guest speakers include Deepak L. Bhatt, M.D., MPH; Charles Pollack, M.D.; and Philippe Gabriel Steg, M.D.

Video webcast to be held on November 15, 2021, at 12:30 p.m. ET (9:30 a.m. PT)

PhaseBio Pharmaceuticals, Inc. (NASDAQ:PHAS), a clinical-stage biopharmaceutical company focused on the development and commercialization of novel therapies for cardiopulmonary diseases, today announced that it will host an investor call on November 15, 2021, at 12:30 p.m. ET (9:30 a.m. PT) to discuss the results of a prespecified interim analysis of the pivotal Phase 3 REVERSE-IT trial that will be presented during a late-breaking science session at the American Heart Association Scientific Sessions 2021. REVERSE-IT is the company's ongoing pivotal Phase 3 study evaluating bentracimab for the reversal of the antiplatelet effects of ticagrelor in patients who present with uncontrolled major bleeding or who require surgery or invasive procedure.

Participants Include:

• Deepak L. Bhatt, M.D., MPH, Executive Director of Interventional Cardiovascular Programs, Brigham and Women's Hospital and Professor of Medicine at Harvard Medical School
• Charles Pollack, M.D., MA, FACEP, Clinician-Scientist, Department of Emergency Medicine, University of Mississippi Medical Center in Jackson
• Ph. Gabriel Steg, M.D., FESC, FACC, Interventional Cardiologist and Chief of Cardiology of Hôpital Bichat in Paris, France and Professor of Cardiology at University of Paris
• Jonathan Mow, Chief Executive Officer, PhaseBio
• John Lee, M.D., Ph.D., Chief Medical Officer, PhaseBio

The webcast will follow a presentation of the prespecified interim analysis data, which will be presented for the first time during a late-breaking science presentation at the American Heart Association Scientific Sessions 2021. A question and answer session with the PhaseBio management team and guest speakers will follow the presentation and roundtable discussion.

Investor Call on November 15, 2021, at 12:30 p.m. ET (9:30 a.m. PT)

The video conference call for investors and analysts will be held on November 15, 2021, at 12:30 p.m. ET (9:30 a.m. PT). Interested parties may RSVP to join the virtual event through the following registration link: https://onlinexperiences.com/Launch/QReg/ShowUUID=19CB5A76-2767-43C6-A132-B025301158EB. The webcast can also be accessed by phone by calling 833-942-2359 from the United States and Canada or 470-414-9401 internationally and using the conference ID/passcode 5616009.

A replay of the presentation and discussion will be available for 60 days on the Events & Presentations page of the "Investors" section of the company's website at www.phasebio.com.

About Bentracimab (PB2452)

Bentracimab is a novel, recombinant, human monoclonal antibody antigen-binding fragment designed to reverse the antiplatelet activity of ticagrelor in major bleeding and urgent surgery situations. In a Phase 1 clinical trial, bentracimab demonstrated the potential to bring life-saving therapeutic benefit through immediate and sustained reversal of ticagrelor's antiplatelet activity, mitigating concerns regarding bleeding risks associated with the use of this antiplatelet drug. Data from the Phase 1 clinical trial of bentracimab in healthy volunteers was published in the New England Journal of Medicine in March 2019. In April 2019, bentracimab received Breakthrough Therapy Designation from the FDA. In September 2019, PhaseBio completed a Phase 2a trial in which bentracimab was investigated in healthy, older and elderly subjects on dual antiplatelet therapy of ticagrelor and low-dose aspirin. Additionally, the Phase 2a trial investigated a bentracimab regimen for the reversal of supratherapeutic doses of ticagrelor in healthy younger subjects. In November 2021, PhaseBio completed a Phase 2b trial in which bentracimab was investigated in healthy, older and elderly subjects on dual antiplatelet therapy of ticagrelor and low-dose aspirin. In all active treatment arms in both the Phase 2a and Phase 2b trials, bentracimab achieved immediate and sustained reversal of the antiplatelet effects of ticagrelor and was generally well-tolerated, with only minor adverse events reported. These results are consistent with the results observed in healthy younger subjects treated with ticagrelor in the previously published Phase 1 trial. PhaseBio initiated REVERSE-IT, a pivotal Phase 3 clinical trial of bentracimab, in March 2020 to support a potential Biologics License Application for bentracimab in both major bleeding and urgent surgery indications.

About PhaseBio

PhaseBio Pharmaceuticals, Inc. is a clinical-stage biopharmaceutical company focused on the development and commercialization of novel therapies for cardiovascular and cardiopulmonary diseases. The company's pipeline includes: bentracimab (PB2452), a novel reversal agent for the antiplatelet therapy ticagrelor; pemziviptadil (PB1046), a once-weekly vasoactive intestinal peptide (VIP) receptor agonist for the treatment of pulmonary arterial hypertension; and PB6440, an oral agent for the treatment of resistant hypertension. PhaseBio's proprietary elastin-like polypeptide technology platform enables the development of therapies with potential for less-frequent dosing and improved pharmacokinetics, including pemziviptadil, and drives both internal and partnership drug-development opportunities.

PhaseBio is located in Malvern, PA, and San Diego, CA. For more information, please visit www.phasebio.com, and follow us on Twitter @PhaseBio and LinkedIn.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Words such as "anticipates," "believes," "expects," "intends," "potential," "projects," "target," "will," "would" and "future" or similar expressions are intended to identify forward-looking statements.

Forward-looking statements include statements concerning or implying the conduct or timing of our clinical trials and our research, development and regulatory plans for our product candidates, the timing of availability or disclosure of data from those clinical trials and the timing of planned regulatory submissions, the potential for these product candidates to receive regulatory approval from the FDA or equivalent foreign regulatory agencies, and whether, if approved, these product candidates will be successfully distributed and marketed. Forward-looking statements are based on management's current expectations and are subject to various risks and uncertainties that could cause actual results to differ materially and adversely from those expressed or implied by such forward-looking statements. Accordingly, these forward-looking statements do not constitute guarantees of future performance, and you are cautioned not to place undue reliance on these forward-looking statements.

Risks regarding our business are described in detail in our Securities and Exchange Commission filings, including in our Quarterly Report on Form 10-Q for the quarter ended June 30, 2021. These forward-looking statements speak only as of the date hereof, and PhaseBio Pharmaceuticals, Inc. disclaims any obligation to update these statements except as may be required by law.

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