How Two Special Antibodies Find Substances in Body Fluids
This patent describes a "sandwich" method using two highly specific, man-made antibodies to detect and measure tiny amounts of specific substances, like disease markers, in a fluid sample.
Original patent title: “Immunometric assays using monoclonal antibodies”
This patent describes a "sandwich" method using two highly specific, man-made antibodies to detect and measure tiny amounts of specific substances, like disease markers, in a fluid sample. Granted to Hybritech Inc in 1983 with 32 claims and 1,572 forward citations.
Key facts
Coverage
What does this patent actually cover?
This patent describes a "sandwich" method to find or measure tiny amounts of a specific substance, called an "antigenic substance," in a fluid. First, a sample of the fluid is mixed with a measured amount of a special, man-made "first monoclonal antibody" that has a label, like a radioactive tag (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 1(a), Claim 8). This first antibody attaches to the target substance. Then, this mixture is exposed to a "second monoclonal antibody" that is stuck to a solid surface (Claim 1(b)). This second antibody also attaches to the target substance, creating a "sandwich" where the target substance is held between the two antibodies. The solid surface is then separated and washed (Claim 1(c), Claim 5), and the amount of labeled first antibody stuck to it is measured (Claim 1(d)). By comparing this measurement to known samples, the presence or amount of the target substance can be determined (Claim 1(e)). For example, this could be used to detect hepatitis B proteins in a blood sample.
The gap
What does this patent NOT cover?
- Does not cover assays that use polyclonal antibodies, which are mixtures of different antibodies.
- Does not cover single-antibody detection methods or competitive binding assays.
- Does not cover methods where both antibodies are soluble or both are bound to a solid surface.
- Does not cover antibodies with an affinity lower than 10^8 liters/mole for the target substance.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
The clever bit was combining the newly available, highly specific "monoclonal antibodies" with the "two-site sandwich" assay format. This allowed for much more precise and reliable detection of tiny amounts of specific substances, reducing false positives and improving consistency compared to older methods using less specific antibody mixtures.
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
Home pregnancy tests
Rapid strep throat tests
Tests for specific cancer markers like CEA or alphafetoprotein
Blood tests for hepatitis B
Tests for thyroid stimulating hormone (TSH) levels
Why it matters
The bigger picture
This patent was filed early in the development of monoclonal antibody technology, applying these highly specific tools to the widely used "sandwich" immunoassay format. This combination significantly improved the accuracy and sensitivity of diagnostic tests for various substances in biological fluids. It laid a foundation for more precise detection of disease markers, hormones, and other critical molecules in clinical diagnostics.
Filed
August 4, 1980
Granted
March 8, 1983
Market context
Who's building on this
Companies in this space
Beckman Coulter, which acquired Hybritech, continues to be a major player in diagnostic solutions, building on the fundamental principles of immunometric assays. Other large diagnostic companies like Roche Diagnostics, Abbott Laboratories, and Siemens Healthineers also develop and market diagnostic tests that utilize monoclonal antibody-based sandwich assays for various medical conditions.
Market impact
This patent helped to standardize and improve the reliability of diagnostic testing. By enabling the use of highly specific monoclonal antibodies in a "sandwich" format, it led to the development of more accurate and sensitive tests for diseases, hormones, and other biomarkers. This significantly advanced the field of in vitro diagnostics, allowing for earlier and more precise detection of medical conditions.
Claim 1 — Plain English
What this patent covers
This patent describes a "sandwich" method to find or measure tiny amounts of a specific substance, called an "antigenic substance," in a fluid. First, a sample of the fluid is mixed with a measured amount of a special, man-made "first monoclonal antibody" that has a label, like a radioactive tag (Claim 1(a), Claim 8). This first antibody attaches to the target substance. Then, this mixture is exposed to a "second monoclonal antibody" that is stuck to a solid surface (Claim 1(b)). This second antibody also attaches to the target substance, creating a "sandwich" where the target substance is held between the two antibodies. The solid surface is then separated and washed (Claim 1(c), Claim 5), and the amount of labeled first antibody stuck to it is measured (Claim 1(d)). By comparing this measurement to known samples, the presence or amount of the target substance can be determined (Claim 1(e)). For example, this could be used to detect hepatitis B proteins in a blood sample.
The clever bit
The clever bit was combining the newly available, highly specific "monoclonal antibodies" with the "two-site sandwich" assay format. This allowed for much more precise and reliable detection of tiny amounts of specific substances, reducing false positives and improving consistency compared to older methods using less specific antibody mixtures.
What it does not cover
- Does not cover assays that use polyclonal antibodies, which are mixtures of different antibodies.
- Does not cover single-antibody detection methods or competitive binding assays.
- Does not cover methods where both antibodies are soluble or both are bound to a solid surface.
- Does not cover antibodies with an affinity lower than 10^8 liters/mole for the target substance.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
PatentBrief Score
Impact Score
Strong
Citation count
40/40
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 ×1.5
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
32 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
David, G. S., & Greene, H. E. (1983). How Two Special Antibodies Find Substances in Body Fluids (U.S. Patent No. 4,376,110). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/4376110/psa-test-for-prostate-cancer
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How Two Special Antibodies Find Substances in Body Fluids cover?
This patent describes a "sandwich" method using two highly specific, man-made antibodies to detect and measure tiny amounts of specific substances, like disease markers, in a fluid sample.
Who owns patent US 4376110?
Hybritech Inc owns this patent, granted in 1983.
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 4376110 cited by?
This patent has been cited by 1572 later patents that build on its ideas.
What problem does this patent solve?
This patent was filed early in the development of monoclonal antibody technology, applying these highly specific tools to the widely used "sandwich" immunoassay format. This combination significantly improved the accuracy and sensitivity of diagnostic tests for various substances in biological fluids. It laid a foundation for more precise detection of disease markers, hormones, and other critical molecules in clinical diagnostics.
What does this patent NOT cover?
Does not cover assays that use polyclonal antibodies, which are mixtures of different antibodies.
Patent monitoring