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

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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)