ChronicleBio, Prolong Join Forces to Study Investigational Therapy for ME/CFS

ChronicleBio and Prolong Pharmaceuticals have entered into a development agreement to investigate whether an experimental oxygen-delivery therapy could help patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) recover more quickly from post-exertional malaise (PEM), one of the disease’s most debilitating symptoms.

The planned collaboration will focus on PP-007 (PEGylated carboxyhemoglobin, bovine), also known as SANGUINATE®, an investigational intravenous treatment developed by Prolong. The therapy is designed to deliver oxygen to tissues experiencing oxygen deprivation, improve blood flow, and modulate inflammation.

The companies intend to evaluate PP-007 in a multicenter Phase 2a clinical trial involving at least 40 patients with ME/CFS. Initial patient dosing is expected in mid-2027. Researchers will examine changes in oxygen status following administration and assess whether improved oxygen delivery is associated with reduced symptom severity, shorter recovery periods, and better patient function.

A central component of the study will be ChronicleBio’s AI-driven precision medicine platform, which will be used to identify patients whose underlying disease biology may make them more responsive to PP-007. Rather than relying exclusively on symptom-based enrollment criteria, the approach will use biological markers to select participants with characteristics potentially associated with impaired oxygen delivery.

PEM can trigger substantial physical and cognitive symptoms following even relatively minor exertion, with episodes sometimes lasting days or weeks. The condition affects an estimated 3.3 million Americans with ME/CFS, and approximately one-quarter of patients experience periods of illness severe enough to leave them bedridden. No therapies are currently FDA-approved specifically for the disease.

ChronicleBio CEO and Co-Founder Rohit Gupta said the collaboration is intended to explore whether addressing impaired oxygen delivery could help reduce the duration of PEM episodes. The company’s platform is designed to distinguish patient populations based on underlying biological characteristics and identify those most likely to benefit from targeted interventions.

The rationale for studying PP-007 stems from research suggesting that abnormalities in blood circulation and oxygen utilization may contribute to ME/CFS symptoms in certain patient populations. One study involving 429 adults reported abnormal reductions in cerebral blood flow during tilt testing in approximately 90% of participants. Other research has identified impaired oxygen extraction during exercise in subsets of patients.

PP-007 is designed to transport oxygen to hypoxic tissues while releasing small amounts of carbon monoxide. The latter is being investigated for its potential to support tissue perfusion and influence inflammatory processes. Whether these mechanisms translate into clinical benefits for people with ME/CFS remains to be determined.

Prolong Pharmaceuticals has studied PP-007 in more than 300 individuals across more than a dozen clinical trials involving conditions such as sickle cell disease, subarachnoid hemorrhage, severe anemia, and acute ischemic stroke.

In April 2026, the FDA granted the therapy Breakthrough Therapy Designation for acute ischemic stroke involving anterior large vessel occlusion. The agency had previously awarded Fast Track Designation for the same indication in October 2024. Neither designation represents marketing approval, and both apply specifically to the stroke indication.

ChronicleBio’s endotype intelligence platform uses machine learning to analyze nearly 200 terabytes of multi-omic patient data from individuals with chronic illnesses, including ME/CFS. The technology is intended to identify distinct biological subgroups that may respond differently to specific treatments. To date, the company has identified 14 biological subtypes. One subgroup of ME/CFS patients exhibits markers associated with microvascular dysfunction and impaired oxygen delivery, characteristics that could make PP-007 a candidate for further investigation.

Under the agreement, Prolong will provide the investigational drug and financial support through upfront and milestone-based payments. ChronicleBio may also qualify for additional payments tied to subsequent development of PP-007 for ME/CFS or related conditions. The companies did not disclose the financial details of the arrangement. PP-007 remains investigational and has not been approved by the FDA or any other regulatory authority for any indication.

Learn more at www.chroniclebio.com.