# 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

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_Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._