End of Phase 1 Meeting Update August 14, 2019 Exhibit 99.1

Legal Disclaimer This presentation includes forward-looking statements. All statements contained in this presentation other than statements of historical facts, including statements regarding future results of operations and financial position of PhaseBio Pharmaceuticals, Inc. (“we,” “us” or “our”) our business strategy and plans, the preclinical and clinical development of our product candidates and our objectives for future operations, are forward-looking statements. The words “anticipate,” believe,” “continue,” “estimate,” “expect,” “intend,” “may,” “will” and similar expressions are intended to identify forward-looking statements. We have based these forward-looking statements largely on our current expectations and projections about future events and financial trends that we believe may affect our financial condition, results of operations, business strategy, clinical development, short-term and long-term business operations and objectives and financial needs. These forward-looking statements are subject to a number of risks, uncertainties and assumptions. 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 March 31, 2019. Moreover, we operate in a very competitive and rapidly changing environment. New risks emerge from time to time. It is not possible for our management to predict all risks, nor can we assess the impact of all factors on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements we may make. In light of these risks, uncertainties and assumptions, the future events and trends discussed in this presentation may not occur and actual results could differ materially and adversely from those anticipated or implied in the forward-looking statements. Although we believe that the expectations reflected in the forward-looking statements are reasonable, we cannot guarantee future results, levels of activity, performance, achievements or events and circumstances reflected in the forward-looking statements will occur. We are under no duty to update any of these forward-looking statements after the date of this presentation to conform these statements to actual results or revised expectations, except as required by law. You should, therefore, not rely on these forward-looking statements as representing our views as of any date subsequent to the date of this presentation. Moreover, except as required by law, neither we nor any other person assumes responsibility for the accuracy and completeness of the forward-looking statements contained in this presentation.

PB2452, a novel reversal agent for Brilinta® (ticagrelor), provided immediate and sustained reversal of ticagrelor’s antiplatelet effects in a Phase 1 trial PB2452 received Breakthrough Therapy designation from FDA (May 2019) Reversal agent availability would further differentiate ticagrelor from other antiplatelet drugs PB2452 has the potential to transform treatment of ticagrelor patients by mitigating concerns regarding bleeding risks associated with the use of P2Y12 receptor antagonist antiplatelet drugs PB2452 Highlights Bhatt DL, Pollack CV, Weitz JI, et al. Antibody-Based Ticagrelor Reversal Agent in Healthy Volunteers. N Engl J Med 2019;Mar 17:[Epub ahead of print]. Presented by Dr. Deepak L. Bhatt at the American College of Cardiology Annual Scientific Session (ACC 2019), New Orleans, LA, March 17, 2019. Slides available at: https://www.acc.org/~/media/Clinical/PDF-Files/Approved-PDFs/2019/03/15/ACC19_Slides/Mar17_Sun/3pmET_Ticagrelor-Reversal-Agent-acc-2019.pdf

FDA has agreed that Accelerated Approval pathway is the appropriate regulatory pathway for PB2452 Single, non-randomized, open label Phase 3 trial in both surgical and major bleeding populations planned to support a Biologics License Application (BLA) BLA submission for Accelerated Approval to include data from interim analysis of first 100 subjects in the Phase 3 trial, targeting ~50 subjects in each of the major bleeding and surgical populations VerifyNow® PRUTest® biomarker confirmed as the primary efficacy endpoint; has demonstrated high degree of correlation with other platelet function assays in Phase 1 and Phase 2a trials of PB2452 FDA recommended enrollment of 200 total patients in the Phase 3 trial to support full approval for surgical and major bleeding populations Ongoing Phase 2a trial will explore PB2452 reversal of supratherapeutic blood levels of ticagrelor that could result from ticagrelor overdosage or drug-drug interactions; dosing of these subjects to begin this quarter (Q3 2019) Phase 2b trial expected to begin in Q4 2019; will run in parallel with Phase 3 trial and complete in time for BLA filing Phase 3 trial is expected to begin in Q1 2020; based on an 18-month estimated enrollment timeline to reach interim analysis, a potential BLA submission in 2H 2022 FDA recommended post-approval commitments include completion of the Phase 3 trial and the establishment of a patient registry PB2452 End of Phase 1 Meeting Meeting Results and Next Steps

PB2452 - Novel reversal agent for ticagrelor Human monoclonal antibody fragment (Fab), delivered intravenously in the hospital Phase 1 Proof of Concept Trial completed Selected for late-breaking oral presentation American College of Cardiology’s Annual Scientific Session (March 17, 2019) Simultaneously published in the New England Journal of Medicine Immediate and sustained reversal of ticagrelor antiplatelet effects P2Y12 receptor antagonist with demonstrated superior efficacy to clopidogrel Reversal agent availability would differentiate ticagrelor on safety vs. other oral antiplatelet agents Growth in ticagrelor share of P2Y12 market would increase need for reversal agent Significant unmet need for antiplatelet agent reversal All oral antiplatelet agents have the potential to cause major bleeding, which can be severe or even fatal PB2452 immediately and sustainably reverses the antiplatelet effects of ticagrelor Currently oral P2Y12 agents, including ticagrelor, require a ≥5 day washout prior to surgery1,2 Urgent surgery cannot wait 5 days High thrombotic risk during washout In the Phase 1 trial, PB2452 immediately and sustainably reversed ticagrelor inhibition of platelet activation Enables immediate surgery Major Bleeding Urgent Surgery or Intervention Plavix/clopidogrel Prescribing Information: https://packageinserts.bms.com/pi/pi_plavix.pdf, https://www.ema.europa.eu/en/documents/product-information/plavix-epar-product-information_en.pdf Brilinta/Brilique/ticagrelor Prescribing Information: https://www.azpicentral.com/brilinta/brilinta.pdf#page=1, https://www.ema.europa.eu/en/documents/product-information/brilique-epar-product-information_en.pdf

PB2452: Well-Characterized Mechanism of Reversal of Ticagrelor ADP ADP Platelet ADP binds to P2Y12 receptor causing platelet aggregation Ticagrelor binds to P2Y12, inhibiting ADP-induced platelet aggregation This is a reversible process with ticagrelor cycling on/off the P2Y12 receptors PB2452:ticagrelor is eliminated from the bloodstream PB2452:ticagrelor binding is preferential to ticagrelor:P2Y12 binding As free ticagrelor is eliminated, ADP can again activate the P2Y12 receptor, restoring platelet activity PB2452 binds to free ticagrelor with very high affinity PB2452 4. 5. 6. 1. 2. 3. ADP ADP Platelet ADP Ticagrelor P2Y12 Receptor ADP

Clinical Studies BLA enabling data Clinical Trial Timelines Phase 2a testing additional reversal regimen to cover 180 mg BID (2x recommended dose) in healthy older and elderly subjects on DAPT Trial will be completed Q4 2019, not required to finish prior to Phase 2b Phase 2b expected to start Q4 2019, N=200 total, evaluation of dosing regimen and overall safety of PB2452 in healthy older and elderly subjects on DAPT Phase 3 initiation expected Q1 2020, N=200 total, evaluation of efficacy in ticagrelor-treated subjects with major bleeding events or requiring urgent surgery Interim analysis of first 100 patients recommended by FDA for Accelerated Approval submission, with approximately 50 in each of the major bleeding and surgery populations Phase 2b: Healthy older and elderly subjects FDA EOP1 NEJM Planned BLA Submission for Accelerated Approval Phase 3 Interim Analysis for Accelerated Approval Post-approval completion of Phase 3 Breakthrough Therapy 2019 2020 2021 2022 2023 Phase 2a NEJM= New England Journal of Medicine, EOP1=End of Phase 1 Meeting, BID=twice per day, DAPT=Dual antiplatelet therapy (ticagrelor + aspirin), BLA=Biologics License Application N=100, ~50 major bleeding subjects, ~50 urgent surgery subjects N=200, 150 randomized to receive PB2452 N=100, ~50 major bleeding subjects, ~50 urgent surgery subjects Development and Regulatory Timelines

Cohort Ticagrelor Pretreatment PB2452 IV regimen Volunteers Active:Placebo 1 None 0.1 g 30 min 3A:1P 2 None 0.3 g 30 min 3A:1P 3 None 1 g 30 min 3A:1P 4 180 mg PO + 90 mg BID x 2 days 1 g 30 min 6A:2P 5 180 mg PO + 90 mg BID x 2 days 3 g 30 min 6A:2P 6 180 mg PO + 90 mg BID x 2 days 9 g 30 min 6A:2P 7 180 mg PO + 90 mg BID x 2 days 18 g (3 g 5 min + 15 g 7 hr 55 min) 6A:2P 8 180 mg PO + 90 mg BID x 2 days 18 g (6 g 15 min + 6 g 3 hr + 6 g 8hr 45 min) 6A:2P 9 180 mg PO + 90 mg BID x 2 days 18 g (6 g 15 min + 6 g 4 hr + 6 g 12 hr) 3A:1P 10 180 mg PO + 90 mg BID x 2 days 18 g (6 g 10 min + 6 g 3 hr + 6 g 13 hr) 6A:2P Randomized, double-blind, placebo-controlled, single ascending dose trial (n=64) 0.1 – 18 g of PB2452 infused intravenously over 0.5 – 16 hours Platelet function evaluated using three well established and commonly used assays; LTA, VerifyNow PRUTest and VASP Cohorts 9 and 10 achieved trial objectives, forming the basis for dosing in the Phase 2a trial in healthy older and elderly subjects g = grams, min= minutes, A = active, P = placebo, mg=milligrams, hr=hours, PO=orally, BID= twice per day, LTA = light transmittance aggregometry, VASP = vasodilator stimulated phosphoprotein phosphorylation immunoassay Bhatt DL, Pollack CV, Weitz JI, et al. Antibody-Based Ticagrelor Reversal Agent in Healthy Volunteers. N Engl J Med 2019;Mar 17:[Epub ahead of print]. Presented by Dr. Deepak L. Bhatt at the American College of Cardiology Annual Scientific Session (ACC 2019), New Orleans, LA, March 17, 2019. Slides available at: https://www.acc.org/~/media/Clinical/PDF-Files/Approved-PDFs/2019/03/15/ACC19_Slides/Mar17_Sun/3pmET_Ticagrelor-Reversal-Agent-acc-2019.pdf PB2452 Phase 1 Proof-of-Concept Trial in Healthy Subjects

Preferred Term All Placebo (N=16) n (%) All PB2452 (N=48) n (%) Total Number of SAEs 0 2 PB2452-related SAEs 0 0 Unrelated SAEs* 0 2 (4.2) Alcohol intoxication 0 1 (2.1) Acute Respiratory Failure 0 1 (2.1) *Both SAEs occurred in the same individual 4 days after discharge from the clinical site Treatment-Emergent Serious Adverse Events in Phase 1 Trial None were drug-related per blinded investigator Bhatt DL, Pollack CV, Weitz JI, et al. Antibody-Based Ticagrelor Reversal Agent in Healthy Volunteers. N Engl J Med 2019;Mar 17:[Epub ahead of print]. Presented by Dr. Deepak L. Bhatt at the American College of Cardiology Annual Scientific Session (ACC 2019), New Orleans, LA, March 17, 2019. Slides available at: https://www.acc.org/~/media/Clinical/PDF-Files/Approved-PDFs/2019/03/15/ACC19_Slides/Mar17_Sun/3pmET_Ticagrelor-Reversal-Agent-acc-2019.pdf

Treatment-Emergent Adverse Events  Preferred Term All Placebo (N=16) n (%) All PB2452 (N=48) n (%) Total Number of TEAEs 3 27 Number of volunteers with at Least 1 TEAE 2 (12.5) 17 (35.4) Infusion site bruising 0 4 (8.3) Medical device site reaction 0 3 (6.3) Infusion site extravasation 0 2 (4.2) Vessel puncture site bruise 0 2 (4.2) Abdominal pain 0 1 (2.1) Acute respiratory failure 0 1 (2.1) Alcohol poisoning 0 1 (2.1) Blood urine present 0 1 (2.1) Conjunctivitis 0 1 (2.1) Contusion 1 (6.3) 0 Dizziness 0 1 (2.1) Eyelid irritation 1 (6.3) 0 Gastroenteritis 0 1 (2.1) Hematuria 0 1 (2.1) Infusion site reaction 0 1 (2.1) Musculoskeletal chest pain 1 (6.3) 0 Nasopharyngitis 0 1 (2.1) Oropharyngeal pain 0 1 (2.1) Pharyngitis streptococcal 0 1 (2.1) Pneumonia aspiration 0 1 (2.1) Skin abrasion 0 1 (2.1) Upper limb fracture 0 1 (2.1) Treatment-emergent adverse events were limited mostly to mild injection site issues Bhatt DL, Pollack CV, Weitz JI, et al. Antibody-Based Ticagrelor Reversal Agent in Healthy Volunteers. N Engl J Med 2019;Mar 17:[Epub ahead of print]. Presented by Dr. Deepak L. Bhatt at the American College of Cardiology Annual Scientific Session (ACC 2019), New Orleans, LA, March 17, 2019. Slides available at: https://www.acc.org/~/media/Clinical/PDF-Files/Approved-PDFs/2019/03/15/ACC19_Slides/Mar17_Sun/3pmET_Ticagrelor-Reversal-Agent-acc-2019.pdf

P<0.001 across all timepoints, Bonferroni adjusted Immediate and sustained reversal with bolus + prolonged infusion of 18 g PB2452 Complete reversal was observed 5 min after initiation of infusion Duration was infusion-time dependent, lasting 20-24 hours with a 16-hour infusion Onset and Duration of Ticagrelor Reversal – VerifyNow PRUTest Platelet aggregation as observed in the PB2452 and placebo groups (Cohorts 7-10) Bhatt DL, Pollack CV, Weitz JI, et al. Antibody-Based Ticagrelor Reversal Agent in Healthy Volunteers. N Engl J Med 2019;Mar 17:[Epub ahead of print]. *Data presented by Dr. Deepak L. Bhatt at the American College of Cardiology Annual Scientific Session (ACC 2019), New Orleans, LA, March 17, 2019. Slides available at: https://www.acc.org/~/media/Clinical/PDF-Files/Approved-PDFs/2019/03/15/ACC19_Slides/Mar17_Sun/3pmET_Ticagrelor-Reversal-Agent-acc-2019.pdf No platelet rebound effect observed Absence of platelet hyper-reactivity, or rebound effect with arachidonic acid and thrombin receptor activating peptide between 5 minutes and 48 hours* Platelet rebound between 5 minutes and 48 hours was also ruled out by the response to low-dose ADP versus high-dose ADP* PRU= Platelet Reactivity Units Key Trial Results

PRU= Platelet Reactivity Units Bhatt DL, Pollack CV, Weitz JI, et al. Antibody-Based Ticagrelor Reversal Agent in Healthy Volunteers. N Engl J Med 2019;Mar 17:[Epub ahead of print]. Presented by Dr. Deepak L. Bhatt at the American College of Cardiology Annual Scientific Session (ACC 2019), New Orleans, LA, March 17, 2019. Slides available at: https://www.acc.org/~/media/Clinical/PDF-Files/Approved-PDFs/2019/03/15/ACC19_Slides/Mar17_Sun/3pmET_Ticagrelor-Reversal-Agent-acc-2019.pdf Return to Normal Platelet Function: Post-PB2452 Dosing Inhibited Platelet Function: Post-Ticagrelor Dosing Normal Platelet Function: Pre-Ticagrelor Dosing Normal Platelet Function Inhibited Platelet Function Normalized Platelet Function After Ticagrelor Reversal VerifyNow PRUTest Cohorts 9 and 10 achieved study objectives and will be the basis for dosing in the Phase 2a study in generally healthy older volunteers Dose-dependent response across all cohorts tested Immediate reversal within 5 minutes of start of infusion Sustained duration of reversal extended to 20+ hours Rapid resumption of ticagrelor dosing post infusion Well tolerated across all cohorts No drug-related SAEs

Phase 2a Trial Preliminary Results (First 2 Cohorts) PB2452 exhibited immediate and sustained reversal in healthy older (50-64) and elderly (65-80) subjects on DAPT Statistically significant reversal at 5 minutes, sustained for over 20 hours, in total population and subgroups by age Complete reversal achieved by 15 minutes Results from all 3 platelet function tests highly correlated PB2452 generally well-tolerated, with only minor AEs and no drug-related SAEs Cohort 1: no PB2452-related AEs, no SAEs, no infusion-related reactions, no dose-limiting toxicity Cohort 2: one “possibly related” AE of light headedness in 72-year-old female in response to multiple blood draws One unrelated SAE, no infusion-related reactions, no dose limiting toxicity Consistent with Phase 1 trial https://investors.phasebio.com/news-releases/news-release-details/phasebio-announces-positive-preliminary-results-phase-2a

PB2452 Program Summary and Next Steps Product profile: Immediate and sustained reversal of ticagrelor antiplatelet effects Major bleeding and urgent surgical scenarios require immediate and sustained reversal Duration of reversal dependent on infusion length Clinically important immediate and sustained reversal of ticagrelor observed in Phase 1 and Phase 2a trials Well tolerated and no PB2452-related SAEs Announced receipt of meeting minutes from PB2452 End of Phase 1 meeting with FDA FDA agreement on development plan and Accelerated Approval regulatory path Single, non-randomized, open label Phase 3 trial in both surgical and major bleeding populations planned to support a Biologics License Application Next steps for program Preliminary results from Phase 2a trial demonstrated immediate and sustained reversal in healthy older and elderly subjects on DAPT Phase 2a trial to confirm regimen for reversal of supratherapeutic blood levels of ticagrelor Initiation of large Phase 2b trial in healthy older and elderly subjects: Q4 2019 Non-randomized Phase 3 trial to start in Q1 2020 SAEs=Serious adverse events, DAPT=Dual antiplatelet therapy (ticagrelor + aspirin)

Corporate Overview August 2019 Exhibit 99.2

Legal Disclaimer This presentation includes forward-looking statements. All statements contained in this presentation other than statements of historical facts, including statements regarding future results of operations and financial position of PhaseBio Pharmaceuticals, Inc. (“we,” “us” or “our”) our business strategy and plans, the preclinical and clinical development of our product candidates and our objectives for future operations, are forward-looking statements. The words “anticipate,” believe,” “continue,” “estimate,” “expect,” “intend,” “may,” “will” and similar expressions are intended to identify forward-looking statements. We have based these forward-looking statements largely on our current expectations and projections about future events and financial trends that we believe may affect our financial condition, results of operations, business strategy, clinical development, short-term and long-term business operations and objectives and financial needs. These forward-looking statements are subject to a number of risks, uncertainties and assumptions. 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, 2019. Moreover, we operate in a very competitive and rapidly changing environment. New risks emerge from time to time. It is not possible for our management to predict all risks, nor can we assess the impact of all factors on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements we may make. In light of these risks, uncertainties and assumptions, the future events and trends discussed in this presentation may not occur and actual results could differ materially and adversely from those anticipated or implied in the forward-looking statements. Although we believe that the expectations reflected in the forward-looking statements are reasonable, we cannot guarantee future results, levels of activity, performance, achievements or events and circumstances reflected in the forward-looking statements will occur. We are under no duty to update any of these forward-looking statements after the date of this presentation to conform these statements to actual results or revised expectations, except as required by law. You should, therefore, not rely on these forward-looking statements as representing our views as of any date subsequent to the date of this presentation. Moreover, except as required by law, neither we nor any other person assumes responsibility for the accuracy and completeness of the forward-looking statements contained in this presentation.

Company Overview Therapeutic Focus Clinical-stage biopharma company focused on the development and commercialization of novel therapies to treat orphan diseases, with an initial focus on cardiopulmonary indications Product Candidates PB2452 – Novel agent for immediate and sustained reversal of ticagrelor, the preferred antiplatelet therapy of the American College of Cardiology, the American Heart Association and European Society of Cardiology PB1046 – Once-weekly novel treatment for pulmonary arterial hypertension (PAH), based on elastin-like polypeptide (ELP) technology, that is vasodilatory, potentially disease-modifying and complementary to current standard-of-care therapies Platform Technology ELP Technology Extends circulating half-life of proteins and peptides and provides a sustained-release mechanism Enhances solubility, stability and bioavailability, provides extended drug exposure Creates product candidates that are straightforward to manufacture and administer Milestones & Catalysts 2019 PB2452 March 17, 2019 Late-breaking oral presentation of full Phase 1 results at the American College of Cardiology’s Annual Scientific Session/ Simultaneous publication in New England Journal of Medicine PB2452 April 8, 2019 Granted Breakthrough Therapy designation by FDA PB2452 1H 2019 Dosed first patient in Phase 2a trial in healthy older and elderly adults PB2452 June 17, 2019 Reported preliminary results from Phase 2a trial in healthy older and elderly adults PB2452 Q4 2019 Initiate large Phase 2b trial in healthy older adults to support BLA safety database 2020 PB1046 2020 Report Phase 2b data PB2452 Q1 2020 Initiate Phase 3 trial based on plan to pursue accelerated approval pathway

Program Indication/Therapeutic Area Pre-Clinical Phase 1 Phase 2 Phase 3 WW Commercial Rights Milestones PB2452 Reversal of Ticagrelor Antiplatelet Activity Q4 2019: Initiate Phase 2b trial Q1 2020: Initiate Phase 3 trial based on plan to pursue accelerated regulatory pathway PB1046 Pulmonary Arterial Hypertension (PAH) 2020: Report Phase 2b trial results GLP2-ELP Short Bowel Syndrome CNP-ELP Achondroplasia Early Programs A Clinical Stage, Orphan Disease-Focused Biopharmaceutical Company Phase 2 ongoing Breakthrough Therapy designation granted in April 2019 Late research PROPRIETARY LONG ACTING INJECTABLE RECOMBINANT BIOPOLYMERS (Elastin-like Polypeptides – ELPs) ELP TECHNOLOGY PLATFORM DRIVES INTERNAL DISCOVERY IND-enabling activities Phase 2 ongoing

Corporate

Recent Corporate Highlights Announced receipt of meeting minutes from PB2452 End-of-Phase 1 meeting with FDA: August 2019 FDA agreement on development plan and Accelerated Approval regulatory path Single, non-randomized, open label Phase 3 trial in both surgical and major bleeding populations planned to support a Biologics License Application Reported positive preliminary PB2452 Phase 2a results: June 2019 Observed efficacy, safety and tolerability profile consistent with previously published Phase 1 trial Completed underwritten public offering of common stock: April 2019 PhaseBio received $46.3M in net proceeds, after deducting underwriting discounts and commissions and offering expenses PB2452 granted Breakthrough Therapy designation by FDA: April 2019 Breakthrough Therapy designation is designed to expedite the development and review of promising new drugs Reported PB2452 Phase 1 results: March 2019 Presented as a late breaking oral presentation at the American College of Cardiology’s Annual Scientific Session on March 17, 2019 Simultaneously published in the New England Journal of Medicine Executed PB1023 licensing deal with ImmunoForge: April 2019 PhaseBio granted ImmunoForge an exclusive, worldwide license, with rights to sublicense, to PB1023 for the development and commercialization of treatments for all diseases except diabetes, obesity and non-alcoholic steatohepatitis Secured up to $15 million term loan facility from Silicon Valley Bank and WestRiver Innovation Lending Fund: March 2019 Funds used to repay existing $7.5M term loan in full and support advancement of PB2452 Cash balance as of June 30, 2019: $90.3M Well capitalized and focused on executing development plan

Second-Quarter 2019 Financial Highlights Operating expense: $10.2M R&D: $7.8M SG&A: $2.4M Loss from Operations: ($9.5M) Net Loss of ($9.2M) or ($0.33) per share 27.9M shares used for computing Q2 2019 net loss per share Cash and cash equivalents as of 06/30/2019: $90.3M All values in USD millions except share counts and net loss per share Numbers may not sum to totals due to rounding

Experienced Management Team JONATHAN MOW Chief Executive Officer Amylin Pharmaceuticals, Corus Pharma, PathoGenesis, BMS JOHN SHARP Chief Financial Officer Ligand Pharmaceuticals, HUYA Bioscience, Sequenom, Diversa JOHN LEE, MD, PhD, FACC Chief Medical Officer Merck, BMS, Quintiles SUSAN ARNOLD, PhD VP of Preclinical & CMC Targeted Genetics, Viromed Biosafety Labs, BioRexis, NuPathe JIM BALLANCE, PhD VP Research & Scientific Affairs Delta Biotechnology, Aventis Behring, BioRexis MICHAEL YORK VP Corp Development & Commercial Strategy Orexigen, Amylin Pharmaceuticals, Santarus, Amgen, AstraZeneca GLEN BURKHARDT VP Human Resources Hologic, Onyx Pharmaceuticals, Eli Lilly

PB2452 – Reversal Agent for Ticagrelor

PB2452 - Novel reversal agent for Brilinta (ticagrelor) Human monoclonal antibody fragment (Fab), delivered intravenously in the hospital Phase 1 Proof of Concept Study completed Selected for late-breaking oral presentation American College of Cardiology’s Annual Scientific Session (March 17, 2019) Simultaneously published in the New England Journal of Medicine Immediate and sustained reversal of ticagrelor antiplatelet effects P2Y12 receptor antagonist with demonstrated superior efficacy to clopidogrel Reversal agent availability would differentiate ticagrelor on safety vs. other oral antiplatelet agents Growth in ticagrelor share of P2Y12 market would increase need for reversal agent Significant unmet need for antiplatelet agent reversal All oral antiplatelet agents have the potential to cause major bleeding, which can be severe or even fatal PB2452 immediately and sustainably reverses the antiplatelet effects of ticagrelor Currently oral P2Y12 agents, including ticagrelor, require a ≥5 day washout prior to surgery1,2 Urgent surgery cannot wait 5 days High thrombotic risk during washout In the Phase 1 study, PB2452 immediately and sustainably reversed ticagrelor inhibition of platelet activation Enables immediate surgery Major Bleeding Urgent Surgery or Intervention Plavix/clopidogrel Prescribing Information: https://packageinserts.bms.com/pi/pi_plavix.pdf, https://www.ema.europa.eu/en/documents/product-information/plavix-epar-product-information_en.pdf Brilinta/Brilique/ticagrelor Prescribing Information: https://www.azpicentral.com/brilinta/brilinta.pdf#page=1, https://www.ema.europa.eu/en/documents/product-information/brilique-epar-product-information_en.pdf

PB2452: Well-Characterized Mechanism of Reversal of Ticagrelor ADP ADP Platelet ADP binds to P2Y12 receptor causing platelet aggregation Ticagrelor binds to P2Y12, inhibiting ADP-induced platelet aggregation This is a reversible process with ticagrelor cycling on/off the P2Y12 receptors PB2452:ticagrelor is eliminated from the bloodstream PB2452:ticagrelor binding is preferential to ticagrelor:P2Y12 binding As free ticagrelor is eliminated, ADP can again activate the P2Y12 receptor, restoring platelet activity PB2452 binds to free ticagrelor with very high affinity PB2452 4. 5. 6. 1. 2. 3. ADP ADP Platelet ADP Ticagrelor P2Y12 Receptor ADP

FDA has agreed that Accelerated Approval pathway is the appropriate regulatory pathway for PB2452 Single, non-randomized, open label Phase 3 trial in both surgical and major bleeding populations planned to support a Biologics License Application (BLA) BLA submission for Accelerated Approval to include data from interim analysis of first 100 subjects in the Phase 3 trial, targeting ~50 subjects in each of the major bleeding and surgical populations VerifyNow® PRUTest® biomarker confirmed as the primary efficacy endpoint; has demonstrated high degree of correlation with other platelet function assays in Phase 1 and Phase 2a trials of PB2452 FDA recommended enrollment of 200 total patients in the Phase 3 trial to support full approval for surgical and major bleeding populations Ongoing Phase 2a trial will explore PB2452 reversal of supratherapeutic blood levels of ticagrelor that could result from ticagrelor overdosage or drug-drug interactions; dosing of these subjects to begin this quarter (Q3 2019) Phase 2b trial expected to begin in Q4 2019; will run in parallel with Phase 3 trial and complete in time for BLA filing Phase 3 trial is expected to begin in Q1 2020; based on an 18-month estimated enrollment timeline to reach interim analysis, a potential BLA submission in 2H 2022 FDA recommended post-approval commitments include completion of the Phase 3 trial and the establishment of a patient registry PB2452 End of Phase 1 Meeting Meeting Results and Next Steps

Positive Preliminary PB2452 Phase 2a Results In June 2019, positive preliminary results from the PB2452 Phase 2a trial were disclosed via press release1 This is the first trial of PB2452 to include older (ages 50-64) and elderly (ages 65-80) subjects on dual antiplatelet therapy of ticagrelor and low-dose aspirin Subjects in the trial resemble the patient population most likely to be treated with ticagrelor and potentially benefit from PB2452, if approved Statistically significant reversal of ticagrelor was achieved within 5 minutes of initiation of PB2452 infusion and sustained for over 20 hours Platelet function was normalized by 15 minutes following initiation of PB2452 infusion and remained normal for over 20 hours In these subjects PB2452 was generally well tolerated, with only minor adverse events reported Efficacy of PB2452 in the Phase 2a trial is measured using the same three assays that were utilized in the Phase 1 trial2, with results from all three assays showing a high degree of correlation in both trials Preliminary results consistent with Phase 1 trial https://investors.phasebio.com/news-releases/news-release-details/phasebio-announces-positive-preliminary-results-phase-2a Bhatt, D. L. et al. Antibody-based ticagrelor reversal agent in healthy volunteers. N. Engl. J. Med. https://doi.org/10.1056/NEJMoa1901778 (2019)

PB2452 Granted Breakthrough Therapy Designation In April 2019, PB2452 was granted Breakthrough Therapy designation by FDA Designation supported by Phase 1 trial results, which were recently published in the New England Journal of Medicine1 Breakthrough Therapy designation may be granted by FDA when preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over existing therapies Breakthrough Therapy designation offers companies the following benefits designed to expedite the review process2: Intensive guidance on an efficient drug development program, beginning as early as Phase 1 Organizational commitment involving senior managers All Fast Track designation features including more frequent meetings with FDA and more frequent written communication from FDA Companies may also be eligible for Accelerated Approval and Priority Review, if relevant criteria are met Bhatt, D. L. et al. Antibody-based ticagrelor reversal agent in healthy volunteers. N. Engl. J. Med. https://doi.org/10.1056/NEJMoa1901778 (2019) The U.S. Food and Drug Administration. “Expedited Programs for Serious Conditions – Drugs and Biologics.” Available at: https://www.fda.gov/downloads/Drugs/Guidances/UCM358301.pdf. Accessed April 2019

PB2452 Phase 1 Proof-of-Concept Study in Healthy Subjects Selected as late-breaking oral presentation during featured clinical research session at the American College of Cardiology’s Annual Scientific Session – March 17, 20191 Simultaneously published in the New England Journal of Medicine2 https://www.acc.org/latest-in-cardiology/clinical-trials/2019/03/15/21/37/ticagrelor-reversal-agent Bhatt DL, Pollack CV, Weitz JI, et al. Antibody-Based Ticagrelor Reversal Agent in Healthy Volunteers. N Engl J Med 2019;Mar 17:[Epub ahead of print].

PB2452 Phase 1 Proof-of-Concept Study in Healthy Subjects Randomized, double-blind, placebo-controlled, single ascending dose (SAD), sequential group study (n=64) 3:1 randomization, PB2452-Placebo Higher-dose cohorts pre-treated with ticagrelor After 48 hours of ticagrelor, platelet aggregation was suppressed by ~80%, as expected based on approved package insert Platelet function evaluated using three well established and commonly used assays: LTA, VerifyNow PRUTest® and VASP Results from all three assays were highly correlated Onset of reversal occurred within 5 minutes and was sustained for over 20 hours P<0.001 across all timepoints, Bonferroni adjusted Well tolerated with no drug-related serious adverse events No evidence of rebound in platelet activity after drug cessation LTA = light transmittance aggregometry, VASP = vasodilator stimulated phosphoprotein phosphorylation immunoassay Bhatt DL, Pollack CV, Weitz JI, et al. Antibody-Based Ticagrelor Reversal Agent in Healthy Volunteers. N Engl J Med 2019;Mar 17:[Epub ahead of print].

Cohort Ticagrelor Pretreatment PB2452 IV regimen Volunteers Active:Placebo 1 None 0.1 g 30 min 3A:1P 2 None 0.3 g 30 min 3A:1P 3 None 1 g 30 min 3A:1P 4 180 mg PO + 90 mg BID x 2 days 1 g 30 min 6A:2P 5 180 mg PO + 90 mg BID x 2 days 3 g 30 min 6A:2P 6 180 mg PO + 90 mg BID x 2 days 9 g 30 min 6A:2P 7 180 mg PO + 90 mg BID x 2 days 18 g (3 g 5 min + 15 g 7 hr 55 min) 6A:2P 8 180 mg PO + 90 mg BID x 2 days 18 g (6 g 15 min + 6 g 3 hr + 6 g 8hr 45 min) 6A:2P 9 180 mg PO + 90 mg BID x 2 days 18 g (6 g 15 min + 6 g 4 hr + 6 g 12 hr) 3A:1P 10 180 mg PO + 90 mg BID x 2 days 18 g (6 g 10 min + 6 g 3 hr + 6 g 13 hr) 6A:2P Randomized, double-blind, placebo-controlled, single ascending dose trial (n=64) 0.1 – 18 g of PB2452 infused intravenously over 0.5 – 16 hours Platelet function evaluated using three well established and commonly used assays; LTA, VerifyNow PRUTest® and VASP Cohorts 9 and 10 achieved trial objectives, forming the basis for dosing in the Phase 2a trial in healthy older and elderly subjects g = grams, min= minutes, A = active, P = placebo, mg=milligrams, hr=hours, PO=orally, BID= twice per day, LTA = light transmittance aggregometry, VASP = vasodilator stimulated phosphoprotein phosphorylation immunoassay Bhatt DL, Pollack CV, Weitz JI, et al. Antibody-Based Ticagrelor Reversal Agent in Healthy Volunteers. N Engl J Med 2019;Mar 17:[Epub ahead of print]. Presented by Dr. Deepak L. Bhatt at the American College of Cardiology Annual Scientific Session (ACC 2019), New Orleans, LA, March 17, 2019. Slides available at: https://www.acc.org/~/media/Clinical/PDF-Files/Approved-PDFs/2019/03/15/ACC19_Slides/Mar17_Sun/3pmET_Ticagrelor-Reversal-Agent-acc-2019.pdf PB2452 Phase 1 Proof-of-Concept Trial in Healthy Subjects

PRU= Platelet Reactivity Units Bhatt DL, Pollack CV, Weitz JI, et al. Antibody-Based Ticagrelor Reversal Agent in Healthy Volunteers. N Engl J Med 2019;Mar 17:[Epub ahead of print]. Presented by Dr. Deepak L. Bhatt at the American College of Cardiology Annual Scientific Session (ACC 2019), New Orleans, LA, March 17, 2019. Slides available at: https://www.acc.org/~/media/Clinical/PDF-Files/Approved-PDFs/2019/03/15/ACC19_Slides/Mar17_Sun/3pmET_Ticagrelor-Reversal-Agent-acc-2019.pdf Return to Normal Platelet Function: Post-PB2452 Dosing Inhibited Platelet Function: Post-Ticagrelor Dosing Normal Platelet Function: Pre-Ticagrelor Dosing Normal Platelet Function Inhibited Platelet Function Normalized Platelet Function After Ticagrelor Reversal VerifyNow PRUTest Cohorts 9 and 10 achieved study objectives and will be the basis for dosing in the Phase 2a study in generally healthy older volunteers Dose-dependent response across all cohorts tested Immediate reversal within 5 minutes of start of infusion Sustained duration of reversal extended to 20+ hours Rapid resumption of ticagrelor dosing post infusion Well tolerated across all cohorts No drug-related SAEs

%Platelet aggregation by AA Nominal Time (h) Platelet Aggregation with AA and TRAP Mean platelet aggregation by LTA using AA (top) or TRAP (bottom) as agonist %Platelet aggregation by TRAP Nominal Time (h) Arachidonic acid (AA) Thrombin receptor activating peptide (TRAP) No platelet rebound effect observed Absence of platelet hyper-reactivity, or rebound effect with arachidonic acid and thrombin receptor activating peptide between 5 minutes and 48 hours Platelet rebound between 5 minutes and 48 hours was also ruled out by the response to low-dose ADP versus high-dose ADP* Bhatt DL, Pollack CV, Weitz JI, et al. Antibody-Based Ticagrelor Reversal Agent in Healthy Volunteers. N Engl J Med 2019;Mar 17:[Epub ahead of print]. *ADP data presented by Dr. Deepak L. Bhatt at the American College of Cardiology Annual Scientific Session (ACC 2019), New Orleans, LA, March 17, 2019. Slides available at: https://www.acc.org/~/media/Clinical/PDF-Files/Approved-PDFs/2019/03/15/ACC19_Slides/Mar17_Sun/3pmET_Ticagrelor-Reversal-Agent-acc-2019.pdf

Treatment-Emergent Adverse Events  Preferred Term All Placebo (N=16) n (%) All PB2452 (N=48) n (%) Total Number of TEAEs 3 27 Number of volunteers with at Least 1 TEAE 2 (12.5) 17 (35.4) Infusion site bruising 0 4 (8.3) Medical device site reaction 0 3 (6.3) Infusion site extravasation 0 2 (4.2) Vessel puncture site bruise 0 2 (4.2) Abdominal pain 0 1 (2.1) Acute respiratory failure 0 1 (2.1) Alcohol poisoning 0 1 (2.1) Blood urine present 0 1 (2.1) Conjunctivitis 0 1 (2.1) Contusion 1 (6.3) 0 Dizziness 0 1 (2.1) Eyelid irritation 1 (6.3) 0 Gastroenteritis 0 1 (2.1) Hematuria 0 1 (2.1) Infusion site reaction 0 1 (2.1) Musculoskeletal chest pain 1 (6.3) 0 Nasopharyngitis 0 1 (2.1) Oropharyngeal pain 0 1 (2.1) Pharyngitis streptococcal 0 1 (2.1) Pneumonia aspiration 0 1 (2.1) Skin abrasion 0 1 (2.1) Upper limb fracture 0 1 (2.1) Treatment-emergent adverse events were limited mostly to mild injection site issues Bhatt DL, Pollack CV, Weitz JI, et al. Antibody-Based Ticagrelor Reversal Agent in Healthy Volunteers. N Engl J Med 2019;Mar 17:[Epub ahead of print].

Clinical Studies BLA enabling data Clinical Trial Timelines Phase 2a testing additional reversal regimen to cover 180 mg BID (2x recommended dose) in healthy older and elderly subjects on DAPT Trial will be completed Q4 2019, not required to finish prior to Phase 2b Phase 2b expected to start Q4 2019, N=200 total, evaluation of dosing regimen and overall safety of PB2452 in healthy older and elderly subjects on DAPT Phase 3 initiation expected Q1 2020, N=200 total, evaluation of efficacy in ticagrelor-treated subjects with major bleeding events or requiring urgent surgery Interim analysis of first 100 patients recommended by FDA for Accelerated Approval submission, with approximately 50 in each of the major bleeding and surgery populations Phase 2b: Healthy older and elderly subjects FDA EOP1 NEJM Planned BLA Submission for Accelerated Approval Phase 3 Interim Analysis for Accelerated Approval Post-approval completion of Phase 3 Breakthrough Therapy 2019 2020 2021 2022 2023 Phase 2a NEJM= New England Journal of Medicine, EOP1=End of Phase 1 Meeting, BID=twice per day, DAPT=Dual antiplatelet therapy (ticagrelor + aspirin), BLA=Biologics License Application N=100, ~50 major bleeding subjects, ~50 urgent surgery subjects N=200, 150 randomized to receive PB2452 N=100, ~50 major bleeding subjects, ~50 urgent surgery subjects Development and Regulatory Timelines

Continued Long Term Unit Growth of Ticagrelor Fueled by PB2452 approval Brilinta/Brilique sales in 2018 were $1.32B and growing (+22% Y/Y) Patient growth drives Y/Y revenue growth in all regions: EU (+18%), US (+16%), Emerging Markets (+46%) In February 2019, Brilinta Phase III THEMIS1 trial met primary endpoint in patients with established coronary artery disease and type-2 diabetes Brilinta Phase III THALES2 trial in stroke expected to readout in 2020 Ticagrelor Differentiation vs. clopidogrel Efficacy ✔ ✔ ✔ Safety -- (no reversal agent) ✔ ✔ Price O (branded vs. generic) O (branded vs. generic) ✔ Now Post PB2452 Launch Post LOE of ticagrelor https://www.astrazeneca.com/media-centre/press-releases/2019/brilintas-phase-iii-themis-trial-met-primary-endpoint-in-patients-with-established-coronary-artery-disease-and-type-2-diabetes-25022019.html https://clinicaltrials.gov/ct2/show/study/NCT03354429 Copyright © 2019 PhaseBio Pharmaceuticals, Inc. All Rights Reserved

PB2452 Program Summary and Next Steps Product profile: Immediate and sustained reversal of ticagrelor antiplatelet effects Major bleeding and urgent surgical scenarios require immediate and sustained reversal Duration of reversal dependent on infusion length Clinically important immediate and sustained reversal of ticagrelor observed in Phase 1 and Phase 2a trials Well tolerated and no PB2452-related SAEs Announced receipt of meeting minutes from PB2452 End of Phase 1 meeting with FDA FDA agreement on development plan and Accelerated Approval regulatory path Single, non-randomized, open label Phase 3 trial in both surgical and major bleeding populations planned to support a Biologics License Application Next steps for program Preliminary results from Phase 2a trial demonstrated immediate and sustained reversal in healthy older and elderly subjects on DAPT Phase 2a trial to confirm regimen for reversal of supratherapeutic blood levels of ticagrelor Initiation of large Phase 2b trial in healthy older and elderly subjects: Q4 2019 Non-randomized Phase 3 trial to start in Q1 2020 SAEs=Serious adverse events, DAPT=Dual antiplatelet therapy (ticagrelor + aspirin)

Elastin-Like Polypeptide Technology (ELP) – Engine for Growth

PROLONGED CIRCULATING HALF-LIFE Repeating Sequence of Human Elastin Peptides VPGXG Peptide/Protein (VIP, GLP1, etc.) Active Moiety “Biopolymer” n UP TO 200x INCREASE IN ½ LIFE Proprietary Elastin-Like Polypeptide (ELP) Technology Growth Engine for PhaseBio Preclinical Pipeline ↑ Temperature COACERVATION DELIVERS SLOW RELEASE Inside Body Non-Soluble ELP WEEKLY OR MONTHLY DOSING Outside Body Highly Soluble ELP Pharmacokinetics Slower rate of bioavailability Ease of Administration Patient Compliance IMPROVING

ELP: A Highly Flexible Technology for Modulating Pharmacokinetics VERSATILE: MANY ACTIVE MOIETIES POSSIBLE Peptides or proteins can be genetically fused to N- or C-terminus1, or both. Chemical conjugation to small molecules or peptides LOW COST MANUFACTURING Can be produced in E.coli, yeast or mammalian cells FLEXIBLE EXPOSURE ELP engineering enables exposures ranging from weekly or monthly to rapid uptake (e.g. prandial insulin) WELL TOLERATED Well characterized across multiple clinical programs CORE ELP TECHNOLOGY https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3622222/

PB1046 - Once Weekly Vasoactive Intestinal Peptide (VIP) Analog for Pulmonary Arterial Hypertension

High Unmet Need in an Orphan Disease Primary Pulmonary Arterial Hypertension (PAH, WHO Group 1 PH) High unmet need for novel disease-modifying PAH therapies for greater efficacy All 3 approved drug classes in PAH are vasodilators: prostacyclin, endothelin, and nitric oxide pathways Patients inevitably continue to decline and die on standard of care VIP addresses PAH vasoconstriction, progressive vascular remodeling, and right heart failure McGlaughlin et al. (2015) J. Am. Coll. Cardiol., 65:18

PB1046: Harnessing VIP to Create a Stable, Long-Acting Drug PRECLINICAL STUDIES Support Clinical Development for: Pulmonary Arterial Hypertension DMD Cardiomyopathy Heart Failure (Chemotherapy-Induced HF or HFpEF) Cystic Fibrosis MECHANISM OF ACTION VIA VPAC2 RECEPTOR Potent vasodilator Anti-inflammatory and anti-fibrotic Cardiac support through increased inotropy and lusitropy VIP as a THERAPEUTIC AGENT VPAC2 VPAC1 Half-Life ~60 Hours in Humans PB1046 VPAC2 VPAC1 VIP Peptide Half-Life ~ 1 minute in Humans

PHASE 1 Studies Completed PAH PHASE 2 Studies Well tolerated for a week over broad range of exposure; no drug-related SAEs Prolonged PK/PD profile over 1 week VIP activity confirmed (Systolic and Diastolic BP lowering) Well tolerated across dose range; no drug-related SAEs Replicated PK/PD from SAD over 4 weekly SC injections VIP activity reproduced in HFrEF patients on SOC COMPLETED COMPLETED SAD study in HTN patients washed off meds 4-week MAD study in HFrEF patients on SOC PB1046 Clinical Development Activities to Date Have Supported Advancement into a Phase 2b PAH Efficacy Study Open-Label Phase 2a CardioMEMS in PAH study: Safety and Hemodynamics Phase 2b PAH Efficacy 16-Wk Randomized, Controlled Study PHASE 2b STUDY ACTIVELY ENROLLING CardioMEMS Open-Label PAH Study N = 3 patients, dosed weekly for 8 wks, followed by extension No longer enrolling patients Realtime PA pressure and other hemodynamic monitoring Initial data show improved hemodynamics One drug-related SAE reported in extension portion of open-label pilot study Phase 2b PAH 16 wk randomized, controlled study N = ~60 class II/III PAH patients, dosed weekly x 16 weeks Individual dose titration to MTD Efficacy endpoints PVR via RHC, 6MWD Extension study to follow COMPLETED

PB1046 Single Ascending Dose Study PK and PD Support Once-Weekly SC Administration Single subcutaneous injections in hypertensive patients washed off medications Well tolerated, week-long PK, dose-dependent VIP activity observed Supports weekly SC dosing in multi-dose studies Serum Concentration PB1046 (ng/mL) Slow Release Kinetics (Tmax 48 h) PK HALF-LIFE ~60 HOURS VIP EFFECT ON SYSTOLIC BLOOD PRESSURE Restart Background Anti-hypertensive Therapy 14 21 28

PB1046 Multiple Ascending Dose Study Multi-Dose Safety and PK/PD Confirmed in HFrEF Patients MAD in HFrEF completed 4Q2017 Weekly SC injections x 4 weeks in 29 HF patients maintained on SOC meds Well tolerated in a sick patient population on multiple vasoactive medications Prolonged PK profile replicated in heart failure patients Dose-related systolic BP reduction confirms durable VIP activity PB1046 Induced Sustained Reduction in Systolic BP p = 0.043, placebo vs PB1046 1.2 mg/kg

PB1046 Phase 2b PAH Study Actively Recruiting PAH WHO functional class II/III subjects on two drug oral SOC therapy 16 week randomized, double-blinded, controlled study with extension Primary endpoints: Pulmonary vascular resistance (PVR) via RHC, 6MWD, safety Designed to support placebo-controlled Phase 3 registrational study PhaseBio awarded NIH/NHLBI SBIR R44 grant to support PAH program $2.8M award supports CardioMEMS and Phase 2b PAH studies Open-label extension PB1046 individually titrated to Maximum Tolerated Dose Weekly SC injection x 16 weeks PB1046 Minimum Effective Dose with mock dose titration Weekly SC injection x 16 weeks

PhaseBio Announces Receipt of Minutes of End-of-Phase 1 Meeting with the FDA and Alignment on a Single, Non-Randomized Phase 3 Trial to Support BLA Submission for PB2452

Clinical development plan and Accelerated Approval regulatory path confirmed

Phase 3 trial to initiate in the first quarter of 2020 and intended to support both major bleeding and surgery indications

Conference call and webcast today at 8:30 a.m. EDT

Malvern, PA, and San Diego, CA, August 14, 2019 — PhaseBio Pharmaceuticals, Inc. (Nasdaq: PHAS), a clinical-stage biopharmaceutical company focused on the development and commercialization of novel therapies for orphan diseases, today announced the receipt of written minutes from the End-of-Phase 1 meeting with the U.S. Food and Drug Administration (“FDA”) that was held in July 2019. The End-of-Phase 1 meeting was focused on gaining alignment with the FDA regarding the clinical and regulatory pathway for a potential U.S. approval of PB2452, a novel, recombinant, human monoclonal antibody antigen-binding fragment, or Fab, designed to reverse the antiplatelet activity of ticagrelor in major bleeding and urgent surgery situations. Based on the written minutes from the End-of-Phase 1 meeting, PhaseBio believes that it has reached general agreement with the FDA on the overall design of a single, non-randomized, open label Phase 3 trial of major bleeding and urgent surgical populations to support the submission of a Biologics License Application (“BLA”) for potential accelerated approval of PB2452.

End-of-Phase 1 Meeting Details

During the End-of-Phase 1 meeting, the FDA generally agreed with the proposed clinical development plan and agreed that Accelerated Approval was the appropriate approval pathway for PB2452.

To further support safety assessments, the FDA recommended that PhaseBio include 200 active treatment subjects across its Phase 1 and Phase 2 trials, which includes the planned Phase 2b trial that will begin in the fourth quarter of 2019 and run in parallel to the ongoing Phase 2a and planned Phase 3 trial. To date, approximately 50 subjects have received PB2452 in the completed Phase 1 trial and ongoing Phase 2a trial. The Phase 2b trial is expected to enroll a total of 200 subjects, including 150 subjects who will be randomized to receive PB2452.

The FDA also recommended an assessment of PB2452 reversal in patients who may have supratherapeutic blood levels of ticagrelor as a result of ticagrelor overdosage or drug-drug interactions. Based on the pharmacokinetic and pharmacodynamic modeling conducted in earlier preclinical studies and clinical trials of PB2452, PhaseBio believes it has a clear understanding of the appropriate dosing regimen to reverse the antiplatelet effects of supratherapeutic blood levels of ticagrelor and plans to address this request in its ongoing Phase 2a trial, with dosing of these subjects to begin this quarter. PhaseBio expects to complete the Phase 2a trial in the fourth quarter of 2019.

With respect to the pivotal Phase 3 trial design, the FDA agreed with PhaseBio’s proposed 200 patient, non-randomized, open-label trial design and the proposed pharmacodynamic, clinical and safety endpoints. The FDA also agreed with the proposed use of the VerifyNow PRUTest ^® biomarker as the primary endpoint for the Phase 3 trial. PhaseBio has used VerifyNow PRUTest in its Phase 1 and Phase 2a clinical trials, where it demonstrated a high degree of correlation to other biomarkers used to measure platelet function. To support the BLA submission for Accelerated Approval, the FDA recommended that an interim analysis of the Phase 3 trial include data from the first 100 subjects treated with PB2452, with approximately 50 subjects from each of the major bleeding and surgical populations. To support full approval for patients with major bleeding or requiring urgent surgery, the FDA recommended enrollment of 200 total patients in the Phase 3 trial. PhaseBio expects to initiate the Phase 3 trial in the first quarter of 2020; based on an

estimated 18-month enrollment timeline, a BLA could potentially be submitted in the second half of 2022. For post-approval commitments, the FDA recommended the completion of the remaining portions of the Phase 3 trial and the establishment of a post-approval registry.

“We are pleased with the constructive and collaborative discussion with FDA officials during the End-of-Phase 1 meeting,” said John Lee, M.D., Ph.D., Chief Medical Officer of PhaseBio. “We believe the specific next steps discussed at the meeting, and reflected in the minutes, represent a clear path toward BLA submission. The level of clarity and collaboration we received from the FDA is greatly appreciated. With PB2452 now having a defined development path, coupled with Breakthrough Therapy designation, we believe that we are well positioned to execute our strategy to deliver this potentially life-saving therapy to patients in need as soon as possible.”

Today’s Conference Call Information

PhaseBio will host a conference call and webcast today at 8:30 a.m. EDT to discuss the End-of-Phase 1 meeting. Analysts and investors can participate in the conference call by dialing (866) 221-1776 for domestic callers and (270) 215-9926 for international callers, using the conference ID 5869719. The webcast can be accessed live on the Events and Presentations page in the Investors section of the PhaseBio website, www.phasebio.com. The webcast will be archived on the company’s website for 90 days and will be available for telephonic replay for 14 days following the call by dialing (855) 859-2056 (Domestic) or (404) 537-3406 (International), conference ID 5869719.

About PB2452

PB2452 is a novel, recombinant, human monoclonal antibody Fab fragment designed to reverse the antiplatelet activity of ticagrelor in major bleeding and urgent surgery situations. In a Phase 1 clinical trial, PB2452 demonstrated the potential to bring life-saving therapeutic benefit through immediate and sustained reversal of ticagrelor’s anti-platelet activity, mitigating concerns regarding bleeding risks associated with the use of antiplatelet drugs. The Phase 1 clinical trial of PB2452 in healthy volunteers was published in the New England Journal of Medicine in March 2019. ¹ In April 2019, PB2452 received Breakthrough Therapy designation from FDA. Breakthrough Designation may be granted by FDA when preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over existing therapy. There are currently no approved reversal agents for ticagrelor or any other antiplatelet drugs.

About PhaseBio

PhaseBio Pharmaceuticals, Inc. is a clinical-stage biopharmaceutical company focused on the development and commercialization of novel therapies to treat orphan diseases, with an initial focus on cardiopulmonary disorders. The company’s lead development candidate is PB2452, a novel reversal agent for the antiplatelet therapy ticagrelor. PhaseBio is also leveraging its proprietary elastin-like polypeptide (“ELP”) technology platform to develop therapies with the potential for less-frequent dosing and improved pharmacokinetics. PhaseBio’s second product candidate PB1046, which is based on ELP, is a once-weekly vasoactive intestinal peptide receptor agonist being developed for the treatment of pulmonary arterial hypertension.

PhaseBio is located in Malvern, PA and San Diego, CA. For more information, please visit  www.phasebio.com .

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,” “projects,” and “future” or similar expressions are intended to identify forward-looking statements.

Forward-looking statements include statements concerning or implying the conduct, trial design or timing of our clinical trials, timelines for regulatory submissions, and our research, development and regulatory

plans for PB2452, PB1046 and our ELP research programs . 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 March 31, 2019. 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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Investor Contact:

John Sharp

PhaseBio Pharmaceuticals, Inc.

Chief Financial Officer

(610) 981-6506

john.sharp@phasebio.com

Media Contact:

Gina Cestari

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