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.
Original patent title: “Method of treating IBD/Crohn's disease and related conditions wherein drug metabolite levels in host blood cells determine subsequent dosage”
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. Granted to Centre Hospitalier Universitaire Saint Justine in 2002 with 61 claims and 75 forward citations.
Key facts
Coverage
What does this patent actually cover?
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.
The gap
What does this patent 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.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
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.
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Therapeutic drug monitoring protocols in pediatric gastroenterology clinics
Clinical guidelines for managing IBD patients on azathioprine or 6-mercaptopurine
Why it matters
The bigger picture
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.
Filed
April 8, 1999
Granted
March 12, 2002
Market context
Who's building on this
Companies in this space
Major hospital systems and clinical laboratories continue to utilize these monitoring techniques as standard practice. Pharmaceutical companies and diagnostic firms have expanded on this by developing more sophisticated assays to measure these metabolites more quickly and accurately.
Market impact
This patent helped standardize the practice of therapeutic drug monitoring in gastroenterology. It shifted the clinical standard of care toward personalized medicine, reducing the frequency of adverse drug reactions and improving long-term outcomes for patients with chronic inflammatory conditions.
Claim 1 — Plain English
What this patent covers
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.
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.
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.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
PatentBrief Score
Impact Score
Moderate
Citation count
38/40
Highly cited
Claim breadth
20/20
Very broad protection
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$108K – $346K
Midpoint $216K · expired or expiring · industry ×3.0
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
The original legal language
Original claims
61 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Seidman, E. G., & Théorêt, Y. (2002). Personalized Dosing for Crohn's Disease Drugs Using Blood Tests (U.S. Patent No. 6,355,623). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/6355623/spinraza-nusinersen
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
Embed
Add this patent to your site
Drop this plain-English patent card into any blog post or article — free, no signup. It always links back to the full breakdown here.
<div data-patentlens-widget data-patent-number="US6355623"></div> <script src="https://patentbrief.org/embed.js" async></script>
Stay in the loop
Get a weekly digest of new patents.
One email per week. No spam. Unsubscribe anytime.
Keep exploring
Related patents you should know
US 4683195 · 1987
How to Make Billions of Copies of a DNA Segment
This patent describes the Polymerase Chain Reaction (PCR), a method to rapidly create many copies of a specific piece of DNA or RNA, enabling its detection and analysis.
Cetus Corp
US 8697359 · 2014
How to Edit Genes in Human Cells Using an Engineered CRISPR System
This patent describes an engineered CRISPR-Cas9 system for precisely cutting DNA in eukaryotic cells to change how genes work, opening the door for gene editing in complex organisms.
Massachusetts Institute of Technology
US 7657849 · 2010
How the iPhone's Slide-to-Unlock Gesture Works
Apple's 2010 patent describes unlocking a device by dragging a specific graphical image across the touchscreen along a predefined path, a gesture that became iconic with the original iPhone.
Apple Inc
US 4733665 · 1988
How Doctors Implant a Permanent Stent Using a Balloon
This patent describes the method for placing a permanent, expandable wire mesh tube inside a blood vessel or other body tube using a balloon-tipped catheter to widen it and keep it open.
Expandable Grafts Partnership
US 4965188 · 1990
How to Make Many Copies of a DNA Piece with Heat
This patent describes the Polymerase Chain Reaction (PCR) method, a technique to make millions of copies of a specific DNA segment using a heat-resistant enzyme and repeated temperature changes.
Cetus Corp
US 4235871 · 1980
How to Encapsulate Active Materials in Lipid Bubbles Efficiently
This patent describes a method for trapping biologically active substances inside tiny, multi-layered fat bubbles called liposomes, using a specific water-in-oil emulsion and gel-forming process to improve how much material gets captured.
Individual
More to explore
More in Biotech & Medicine
US 4683195 · 1987 · Cetus Corp
How to Make Billions of Copies of a DNA Segment
US 8697359 · 2014 · Massachusetts Institute of Technology
How to Edit Genes in Human Cells Using an Engineered CRISPR System
US 4733665 · 1988 · Expandable Grafts Partnership
How Doctors Implant a Permanent Stent Using a Balloon
US 4965188 · 1990 · Cetus Corp
How to Make Many Copies of a DNA Piece with Heat
New to patents?
Common Questions
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.
Patent monitoring