ChronicleBio and Prolong Test PP-007 for Chronic Fatigue Syndrome

ChronicleBio and Prolong Pharmaceuticals have announced a partnership to evaluate PP-007 as a potential treatment for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). The companies plan to investigate whether the experimental therapy can improve oxygen delivery to tissues and help patients recover faster from post-exertional malaise (PEM), a major symptom of the condition.

Under the agreement announced on November 12, 2026, the companies plan to conduct a multi-site Phase 2a clinical trial involving at least 40 patients with ME/CFS. The first patients are expected to receive treatment in mid-2027.

PP-007, also known as SANGUINATE, is an investigational intravenous therapy developed by Prolong Pharmaceuticals. It is designed to deliver oxygen to tissues that do not receive enough oxygen, support blood flow and reduce inflammation.

The planned study will examine whether administering PP-007 during episodes of post-exertional malaise can reduce symptom severity and shorten recovery time. Researchers will also measure changes in oxygen levels and assess whether improved oxygen delivery leads to better physical function.

Post-exertional malaise is one of the most difficult symptoms of ME/CFS. It occurs when physical or mental activity triggers a worsening of symptoms, including extreme fatigue, pain and cognitive difficulties. These episodes can last for days or even weeks, making everyday activities challenging for patients.

Using AI to Identify Patients Who May Respond

An important part of the partnership is ChronicleBio’s AI-powered precision medicine platform, which will help identify patients who may be more likely to benefit from PP-007.

Unlike traditional clinical trials that mainly select participants based on their symptoms, the platform uses biological data to identify different disease subtypes, also known as endotypes.

ChronicleBio’s technology uses machine learning to analyse nearly 200 terabytes of multi-omic patient data. The platform has identified 14 biological subtypes, including a group of ME/CFS patients showing signs of microvascular dysfunction and impaired oxygen delivery.

The companies believe this approach could help select patients whose underlying disease biology makes them more suitable for treatment with PP-007.

Rohit Gupta, CEO and Co-Founder of ChronicleBio, said that a treatment capable of shortening recovery from post-exertional malaise could make a meaningful difference to people living with ME/CFS. He highlighted the company’s technology as a way to identify patients who may be more likely to benefit from improved oxygen delivery.

Understanding PP-007

PP-007 is a PEGylated carboxyhemoglobin-based oxygen-delivery therapy. It is designed to transport oxygen to areas of the body where oxygen supply is limited.

The therapy also releases low levels of carbon monoxide, which may help support blood flow and control inflammation.

Prolong Pharmaceuticals has previously evaluated PP-007 in more than 300 people across over 12 clinical trials involving conditions such as sickle cell disease, severe anemia, subarachnoid hemorrhage and acute ischemic stroke.

In April 2026, the US Food and Drug Administration (FDA) granted PP-007 Breakthrough Therapy Designation for acute ischemic stroke involving anterior large vessel occlusion. The therapy had previously received Fast Track designation in October 2024.

However, these regulatory designations apply specifically to acute ischemic stroke and do not represent approval for ME/CFS or any other condition.

Ronald Jubin, Vice President of Early Development and Innovation at Prolong Pharmaceuticals, said the partnership provides an opportunity to explore a targeted treatment approach for a condition with significant unmet medical needs.

Addressing an Unmet Need in ME/CFS

ME/CFS is a long-term and often disabling illness that affects an estimated 3.3 million people in the United States. It can cause severe fatigue, sleep problems, pain, difficulty concentrating and worsening symptoms after even minor physical or mental activity.

There are currently no FDA-approved treatments specifically for ME/CFS, creating a significant need for new therapeutic approaches.

The planned Phase 2a study will help researchers understand whether impaired oxygen delivery plays an important role in symptoms among certain patients and whether PP-007 can offer potential benefits.

The partnership between ChronicleBio and Prolong Pharmaceuticals brings together drug development expertise and AI-based patient selection technology. If successful, the research could support a more targeted approach to treating ME/CFS and potentially open new avenues for patients who currently have limited treatment options.