# Using Synthetic DNA Fragments to Block HIV Replication

> A 1987 patent describing a specific synthetic DNA molecule designed to stop the HIV virus from replicating by blocking a key part of its genetic code.

- **Patent:** US 5110802
- **Original title:** Oligonucleotide phosphonates and method of inhibiting a human immunodeficiency virus in vitro utilizing said oligonucleotide phosphonates
- **Owner:** City of Hope
- **Granted:** 1992
- **Status:** Public domain (expired)
- **Times cited:** 26
- **Field:** biotech, pharmaceutical, gene_editing

## What it does

The patent describes an oligodeoxyribonucleoside methylphosphonate, a synthetic molecule that mimics DNA but is chemically modified to be more stable. This molecule is designed to bind specifically to the first splice acceptor site of the HIV tat III gene. By binding to this site, the molecule prevents the virus from producing the proteins it needs to replicate and form syncytial giant cells, which are clusters of infected cells. The patent claims both the specific sequence 3' TCTTAACC 5' and the method of using such sequences to inhibit HIV in laboratory cell cultures.

## What it does NOT cover

- Does not cover naturally occurring DNA or RNA sequences.
- Does not cover therapeutic methods for treating human patients, as the claims are limited to in vitro applications.
- Does not cover other chemical modifications to DNA backbones beyond methylphosphonates.
- Does not cover sequences that do not target the specific tat III splice acceptor site.

## The clever bit

The inventors used a methylphosphonate backbone to replace the standard phosphate backbone of DNA, making the molecule resistant to degradation by cellular enzymes that would otherwise destroy it before it could reach its target.

## Real-world examples

1. Antisense oligonucleotide research
2. Experimental HIV gene therapy models

## Why it matters

This patent represents an early attempt to use antisense technology to treat viral infections. By targeting the genetic instructions of the virus rather than the proteins it produces, the inventors sought a more precise way to halt the HIV life cycle. It is a foundational example of using synthetic nucleic acids for therapeutic intervention.

## Frequently asked questions

### What does Using Synthetic DNA Fragments to Block HIV Replication cover?

A 1987 patent describing a specific synthetic DNA molecule designed to stop the HIV virus from replicating by blocking a key part of its genetic code.

### Who owns patent US 5110802?

City of Hope owns this patent, granted in 1992.

### 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 5110802 cited by?

This patent has been cited by 26 later patents that build on its ideas.

### What problem does this patent solve?

This patent represents an early attempt to use antisense technology to treat viral infections. By targeting the genetic instructions of the virus rather than the proteins it produces, the inventors sought a more precise way to halt the HIV life cycle. It is a foundational example of using synthetic nucleic acids for therapeutic intervention.

### What does this patent NOT cover?

Does not cover naturally occurring DNA or RNA sequences.

**Full plain-English explainer:** https://patentbrief.org/patent/us/5110802/crixivan-indinavir

**Original patent:** https://patents.google.com/patent/US5110802

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