# Personalized Dosing for Crohn's Disease Drugs Using Blood Tests > A method for adjusting doses of inflammatory bowel disease medication by measuring specific drug metabolites in a patient's red blood cells to maximize effectiveness while avoiding side effects. - **Patent:** US 6355623 - **Original title:** Method of treating IBD/Crohn's disease and related conditions wherein drug metabolite levels in host blood cells determine subsequent dosage - **Owner:** Centre Hospitalier Universitaire Saint Justine - **Granted:** 2002 - **Status:** Public domain (expired) - **Times cited:** 75 - **Field:** biotech, pharmaceutical ## What it does This patent describes a way to personalize the dosage of thiopurine drugs, like 6-mercaptopurine, used to treat conditions like Crohn's disease. Instead of using a standard dose for everyone, doctors measure the concentration of two specific metabolites, 6-thioguanine and 6-methyl-mercaptopurine, within the patient's red blood cells. If 6-thioguanine levels are too low, the drug may not be effective, signaling a need to increase the dose. Conversely, if 6-thioguanine or 6-methyl-mercaptopurine levels are too high, it indicates a risk of toxicity, such as liver damage or blood cell suppression, and the dose should be reduced. ## What it does NOT cover - Does not cover the chemical synthesis or manufacturing of the drugs themselves. - Does not cover diagnostic methods that measure drug levels in tissues other than blood cells. - Does not cover dosing strategies for non-gastrointestinal immune-mediated disorders. - Does not cover the use of genetic testing to predict drug metabolism. ## The clever bit The inventors established specific numerical thresholds for drug metabolites in red blood cells that correlate directly with clinical outcomes, turning a subjective dosing process into a precise, measurable biological feedback loop. ## Real-world examples 1. Therapeutic drug monitoring protocols in pediatric gastroenterology clinics 2. Clinical guidelines for managing IBD patients on azathioprine or 6-mercaptopurine ## Why it matters Before this method, doctors often used a trial-and-error approach to dosing, which could lead to ineffective treatment or dangerous side effects. This patent provided a quantitative, evidence-based framework for therapeutic drug monitoring, which is now a standard practice in gastroenterology for managing IBD patients on thiopurine therapy. ## Frequently asked questions ### What does Personalized Dosing for Crohn's Disease Drugs Using Blood Tests cover? A method for adjusting doses of inflammatory bowel disease medication by measuring specific drug metabolites in a patient's red blood cells to maximize effectiveness while avoiding side effects. ### Who owns patent US 6355623? Centre Hospitalier Universitaire Saint Justine owns this patent, granted in 2002. ### When does this patent expire? This patent has expired and is now in the public domain — anyone can use the invention freely. ### What is patent US 6355623 cited by? This patent has been cited by 75 later patents that build on its ideas. ### What problem does this patent solve? Before this method, doctors often used a trial-and-error approach to dosing, which could lead to ineffective treatment or dangerous side effects. This patent provided a quantitative, evidence-based framework for therapeutic drug monitoring, which is now a standard practice in gastroenterology for managing IBD patients on thiopurine therapy. ### What does this patent NOT cover? Does not cover the chemical synthesis or manufacturing of the drugs themselves. **Full plain-English explainer:** https://patentbrief.org/patent/us/6355623/spinraza-nusinersen **Original patent:** https://patents.google.com/patent/US6355623 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [Using Antibodies to Block IL-26 for Treating Inflammatory Diseases](https://patentbrief.org/patent/us/10751416/tagrisso-osimertinib) — A patent for specific antibodies that block the protein IL-26 to help treat inflammatory conditions like psoriasis and Crohn's disease. - [How Engineered Antibodies Block Inflammation-Causing Proteins](https://patentbrief.org/patent/us/7070775/humira-formulation) — A patent describing lab-made antibodies designed to hunt down and neutralize a specific protein called TNF-alpha that causes chronic inflammation in the body. - [Tiny Lipid Balls for Precise, Better-Absorbed Cannabinoid Medicine](https://patentbrief.org/patent/us/20220304938/lipid-nanoparticle-compositions-and-methods-as-carriers-of-cannabinoids-in-stand) — This patent describes a drug delivery system using tiny lipid nanoparticles to encapsulate cannabinoids, making them easier for the body to absorb and allowing for precise, smaller doses. - [How Synthetic Peptides Block Immune System Overreaction](https://patentbrief.org/patent/us/10106579/orkambi-lumacaftor-ivacaftor) — A patent describing specific synthetic peptides designed to stop the body's immune system from attacking healthy cells by blocking a protein called C5. - [How Ibrutinib-like Molecules Block Cancer-Causing Proteins](https://patentbrief.org/patent/us/8957079/pomalyst-pomalidomide) — A chemical design for molecules that permanently latch onto and disable a specific protein called Btk, which is often responsible for the growth of certain blood cancers.