ChronicleBio, an AI-driven precision therapeutics company focused on chronic neuroimmune diseases, and Prolong Pharmaceuticals, a clinical-stage biopharmaceutical company, today announced a development agreement to evaluate PP-007 (PEGylated carboxyhemoglobin, bovine; also known as SANGUINATE®) as a potential treatment for post-exertional malaise (PEM) in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).

PP-007 is an investigational intravenous therapy designed to deliver oxygen to oxygen-deprived tissues, support blood flow, and reduce inflammation. The companies plan to evaluate whether administering PP-007 during episodes of PEM can accelerate recovery and reduce symptom severity.

The planned multi-site Phase 2a trial will evaluate PP-007 in at least 40 patients with ME/CFS, with first patient dosing anticipated mid-2027. Investigators will assess changes in oxygen status following treatment and examine whether improved oxygen delivery correlates with shorter recovery times and improved patient function.

Unlike traditional ME/CFS trials that enroll patients primarily based on symptoms, the study will leverage ChronicleBio’s proprietary endotype intelligence platform to identify patients whose disease biology suggests they may be more likely to respond to PP-007.

“A PEM crash can take days or weeks out of someone’s life. A treatment that could shorten that recovery would represent a meaningful advance for patients with ME/CFS,” said Rohit Gupta, Chief Executive Officer and Co-Founder, ChronicleBio. “Our platform enables us to identify patients whose disease biology suggests impaired oxygen delivery, allowing us to evaluate PP-007 in a population most likely to benefit.”

ME/CFS is a debilitating chronic illness affecting an estimated 3.3 million Americans. Its defining symptom, PEM, can cause profound physical and cognitive deterioration following even minimal exertion, with episodes lasting days or weeks. Approximately one in four patients is confined to bed at some point during their illness. There are currently no FDA-approved treatments for ME/CFS.

Targeting a Potential Biological Driver of ME/CFS

Emerging research suggests that impaired blood flow and abnormal oxygen extraction may contribute to symptoms in some patients with ME/CFS. A study involving 429 adults found that approximately 90% experienced abnormal reductions in cerebral blood flow during tilt testing, while separate research has identified impaired oxygen extraction during exercise in subsets of patients.

PP-007 is designed to address tissue hypoxia by delivering oxygen to oxygen-deprived tissues while releasing low levels of carbon monoxide, which may support blood flow and modulate inflammation. These properties provide a scientific rationale for investigating PP-007 in patients with ME/CFS, although its safety and efficacy in this population have not been established.

Prolong has evaluated PP-007 in more than 300 individuals across over 12 clinical trials spanning conditions including sickle cell disease, subarachnoid hemorrhage, severe anemia, and acute ischemic stroke. The FDA granted PP-007 Breakthrough Therapy Designation in April 2026 for acute ischemic stroke with anterior large vessel occlusion, following Fast Track Designation in October 2024. These designations do not constitute FDA approval, are specific to acute ischemic stroke, and do not change the standards PP-007 must meet to demonstrate safety and effectiveness.

“We’re excited to partner with ChronicleBio to explore the potential of PP-007 in ME/CFS,” said Ronald Jubin, Ph.D., Vice President, Early Development and Innovation at Prolong Pharmaceuticals. “By combining our investigational oxygen-delivery therapy with ChronicleBio’s AI-powered patient selection platform, we have an opportunity to evaluate a targeted approach to a disease with significant unmet medical need.”

ChronicleBio’s endotype intelligence platform applies machine learning to nearly 200 terabytes of multi-omic data from patients with chronic illnesses, including ME/CFS, to identify biologically distinct patient populations and match them with potential therapies.

The platform has identified 14 biological subtypes, including a subgroup of patients with ME/CFS characterized by markers of microvascular dysfunction and impaired oxygen delivery.

Under the agreement, Prolong will supply PP-007 and provide upfront and milestone-based funding to support the study. ChronicleBio may receive additional payments tied to further development of PP-007 in ME/CFS or related conditions. Financial terms of the deal were not disclosed.

About PP-007

PP-007 (PEGylated carboxyhemoglobin, bovine), also known as SANGUINATE®, is an investigational intravenous therapy designed to deliver oxygen to hypoxic tissues and release low levels of carbon monoxide that may support perfusion and modulate inflammation. PP-007 is intended to be universally compatible across blood types, thermally stable, and supplied ready to administer. It has received FDA Breakthrough Therapy and Fast Track designations for acute ischemic stroke. PP-007 is investigational and has not been approved for any indication by the FDA or any other regulatory authority.

About ChronicleBio

ChronicleBio is an AI-driven precision therapeutics company developing treatments for chronic diseases with significant unmet medical need, including ME/CFS. Its proprietary endotype intelligence platform uses machine learning and deep multi-omic data from its patient biobank to identify biologically distinct patient populations and match them with the clinical-stage and approved therapies from which they may be most likely to benefit. This precision approach aims to accelerate drug development, reduce clinical trial costs, and improve patient outcomes. The company is based in Menlo Park, CA. Learn more at www.chroniclebio.com.

About Prolong Pharmaceuticals

Prolong Pharmaceuticals is an advanced clinical-stage pharmaceutical company headquartered in South Plainfield, New Jersey, and vertically integrated with a proprietary state-of-the-art manufacturing facility. Prolong Pharmaceuticals is developing PP-007 as a potential treatment for ME/CFS, acute ischemic stroke, and other indications related to hypoxia and neuroinflammation. For more information, visit www.prolongpharma.com.

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