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PP-007

PP-007 (formerly SANGUINATE®) is PEGylated bovine carboxyhemoglobin, administered by IV infusion, in development for treating acute ischemic stroke.

At a glance

What it is
PEGylated bovine carboxyhemoglobin oxygen carrier
Lead indication
Acute ischemic stroke due to anterior large vessel occlusion (A-LVO), alongside standard of care
Status
Phase 1/2 (HEMERA-1) complete · Pivotal Phase 3 (HEMERA-2) planned
FDA designations
Breakthrough Therapy (Apr 2026, acute ischemic stroke) · Fast Track (Oct 2024, acute ischemic stroke) · Orphan Drug (2015, sickle cell disease)
Human experience
Over 300 people dosed across 12+ clinical studies
Format
500 mL ready-to-use IV bag, stored at room temperature

Reopening the vessel is not the same as saving the brain

Stroke care has two treatments: clot-dissolving drugs (IV thrombolysis, since 1996) and clot removal (mechanical thrombectomy, since 2015). Even when clot removal works, many patients do not recover, due to challenges downstream.

  • Persistent hypoperfusion. Blood flow in the small vessels stays poor, in about 30% of patients.
  • Reperfusion injury. Tissue is damaged when blood returns, in about 47% of patients.

~46.7%reach functional independence at 90 days with standard of care: mRS 0–2, able to look after themselves without help.

  1. Minute 0

    A clot blocks an artery

    Blood stops reaching part of the brain, and cells there start to die within minutes.

  2. The first hours

    A core is lost, but the tissue around it can still be saved

    Around the core is the penumbra: starved of oxygen, but able to recover if oxygen gets back in time.

  3. Within 24 hours

    Clot removal can reopen the artery

    Thrombectomy clears the clot, and blood flows through the large vessel again.

  4. 24 to 72 hours

    The small vessels can stay blocked

    Constricted collaterals hold red blood cells back. In around 30% of patients, poor blood flow persists and the damage can keep spreading.

    Rivet, Stroke 2025

  5. With PP-007

    PP-007 can bypass

    Given its small size and anti-vasoconstrictive properties, it can reach the penumbra and selectively release oxygen.

  6. The aim

    More tissue is preserved

    PP-007 is designed to oxygenate and save more of the penumbra.

Despite advances that allow more patients to qualify for thrombectomy (SOC), outcomes have remained below 50%

ThrombectomyControlLiving independently at 90 days (mRS 0–2)

  1. 2015

    Stent retrievers, CT angiography

    46% vs 27%

    Large vessel stroke within 6 hours

  2. 2018

    Perfusion imaging

    45–49% vs 13–17%

    Window widened from 6 to 24 hours

  3. 2023

    Large-core strokes

    20–30% vs 7–12%

    Patients with a large core added

  4. 2025–26

    Low-profile devices for medium vessels

    5 MeVO RCTs1 positive

    Limited MT Success in MeVOs

    Only 1 of 5 RCTs demonstrated significant improvement in functional outcomes

Goyal, Lancet 2016 (HERMES); Nogueira, NEJM 2018; Albers, NEJM 2018; Sarraj, NEJM 2023; Huo, NEJM 2023; Mocco, NEJM 2025; Jing, NEJM 2026; Saver, ESOC 2026; Clarençon, JAMA 2026; Hu, NEJM 2026.

Get oxygen past the blockage

Red blood cellsClotPP-007gets throughOxygen-starvedtissue

Under 0.01 µm, more than 700 times smaller than a red blood cell, PP-007 can travel through narrowed and partly blocked vessels, including collateral routes.

700×smaller than a red blood cell.

123In the vesselsIn oxygen-rich areasIn starved tissue

  1. In the vessels

    CO comes off first

    The small amount of carbon monoxide it carries is released first. It relaxes vessels and dampens inflammation.

  2. In oxygen-rich areas

    Oxygen binds

    Oxygen takes the place of any CO left on the carrier, and the CO is exhaled.

  3. In starved tissue

    Oxygen comes off where it is low

    It holds oxygen tightly (P50 about 12 mmHg, against 26 for red blood cells), so it releases it primarily where tissue is starved. It keeps circulating for at least 24 hours.

Hemoglobin-Based Oxygen Carrier history

Earlier hemoglobin-based oxygen carriers largely failed because of vessel constriction and cardiac side effects. Those failures trace back to design choices: oxygen affinity, concentration, viscosity, cross-linking and nitric-oxide scavenging.

PP-007 differs on each. It is PEGylated rather than cross-linked or polymerized, it has a lower P50, it comes pre-loaded with CO, and its larger hydrodynamic radius reduces leakage from vessels.

A proprietary PEGylation process

PEGfinity adds polyethylene glycol to shield a bovine protein from the immune system and keep it circulating for at least 24 hours.

Prolong's founders come from the work behind Adagen (1990), the first FDA-approved PEGylated protein. Read the full story.

From animal studies to the FDA

  1. Animal models

    Does it limit brain damage during a stroke?

    >62% less brain tissue lost than predicted, against ~13% with saline, in dogs with a permanently blocked artery. Blood flow to the blocked area recovered by about 24% of normal, against almost none with saline.1

  2. Brain imaging in people

    Can it improve cerebral blood flow to oxygen-starved areas of the brain?

    16% increase in cerebral blood flow to vulnerable brain regions immediately following a single dose of PP-007, as measured by PET imaging in patients with or at risk of delayed cerebral ischemia following subarachnoid hemorrhage.2

  3. Experience in people

    How many people have received it?

    300+ across 12 clinical studies in stroke, sickle cell disease, severe anemia, kidney transplant and more.3

  4. HEMERA-1

    Do more stroke patients recover when it is added to standard of care?

    67.5% of 40 A-LVO patients were living independently at 90 days, against about 46.7% expected with standard of care alone.4

  5. FDA

    Has the FDA given it a faster path?

    2026 Breakthrough Therapy designation in April, after Fast Track designation in 2024. Both bring closer FDA guidance and expedite review timelines.5,6

HEMERA-1 in detail, and HEMERA-2

1Christoforidis, J NeuroInterv Surg 20222Dhar, Neurocrit Care 20173Prolong data on file4Prolong, World Stroke Congress 20255Prolong, Apr 20266Prolong, Oct 2024

The same property could matter wherever tissue lacks oxygen

  • Acute ischemic stroke

    Anterior large vessel occlusion, alongside standard of care

    • HEMERA-1 Phase 1/2 complete
    • HEMERA-2 Phase 3 next
    • Breakthrough Therapy · Fast Track designation

  • Sickle cell disease

    Vaso-occlusive crisis

    • Phase 2a
    • Orphan Drug Designation

  • When blood is not an option

    Severe anemia when transfusion is not possible, emergency use

    • Phase 1 complete
Also studied in people with: delayed cerebral ischemia after subarachnoid hemorrhage, kidney transplant, thalassemia.