Here's food—make that junk food—for thought: What if the Supreme Court blew up patent protection for innovation, while also harming biomedical progress? Nothing less is at stake in Mayo v. Prometheus, which the High Court hears tomorrow. At issue is a diagnostic test that targets therapies for immune-related gastrointestinal disorders like Crohn's disease. One recent advance has been the drugs known as thiopurines, which metabolize in ways that suppress the immune system and mitigate symptoms. The problem is prescribing the appropriate dosage, because every body processes thiopurines differently. If doctors overshoot, the results can be toxic or even fatal—so they typically "start low and go slow" through trial and error.