A new playbook for drug repurposing

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How GPT-5 Pro turns a clinical surprise into testable hypotheses for hard-to-treat disease

With GPT-5 Pro, immunologist Dr. Oral Alpan of McLean, Va., is discovering new applications that existing FDA‑approved drugs may have for untreatable diseases. The spark was a single patient under his care for severe eczema, who also had a rare allergy known as Food Protein Induced Enterocolitis Syndrome (FPIES), in which specific foods cause delayed, severe gut inflammation. For two decades, the patient reacted to even trace wheat with vomiting, cramping, or diarrhea. After starting the drug dupilumab for the skin disease, the patient accidentally ingested wheat while traveling … and had no reaction. Back in clinic, Dr. Alpan supervised an oral food challenge approaching 50 grams of wheat protein. Again, no reaction. When insurance cut off access to dupilumab, the patient’s symptoms returned. Restarting the drug fixed things. Dr. Alpan’s team at Amerimmune gathered more cases and wrote a paper showing 7 more patients with favorable food-allergy responses while on dupilumab for conditions it was already approved for. These observations set the stage for a new approach: Could AI connect those dots from a de‑identified clinical vignette before Alpan’s observational study on dupilumab was published? Alpan’s colleague, Dr. Derya Unutmaz, brought up the idea of testing GPT‑5 Pro on a subject where the doctors knew the answer before it was available to AI. So they fed GPT-5 the patient’s case, and it returned a ranked list of possible drugs. At the top, it named dupilumab, linking the on‑label eczema to a hypothesis about mucosal immunity in the gut. GPT-5 also flagged patient profiles at risk of side‑effects. “For me, this was evidence that AI can behave intuitively in the scientific sense,” Dr. Alpan said. The next step is to tackle other untreatable conditions, some of them affecting millions globally. Clinic observations suggest a subtype of irritable bowel syndrome (IBS) may share the same type‑2 inflammatory footprint seen in the FPIES cohort. Guided by GPT‑5, the Amerimmune team found another drug candidate, fevipiprant, which Novartis originally studied for asthma, but discontinued. The same molecule has potential applications to postural orthostatic tachycardia syndrome (POTS), where autonomic symptoms may intersect with immune signaling. There are more than 20,000 FDA‑approved drugs. Many may hold second or third lives treating diseases that today are out of reach. GPT‑5 Pro helps clinicians read a case, map mechanisms across disciplines, and prioritize which repurposing ideas may merit prospective testing. If even a fraction are validated and FDA approved, millions of people could see meaningful relief.

A new playbook for drug repurposing

How GPT-5 Pro turns a clinical surprise into testable hypotheses for hard-to-treat disease

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