# How Gilead Made a Stable HIV Pill Combining Two Medicines

> This patent describes a stable, single-pill combination of two HIV drugs, tenofovir disoproxil fumarate and emtricitabine, designed to prevent them from breaking down when stored together.

- **Patent:** US 8592397
- **Original title:** Compositions and methods for combination antiviral therapy
- **Owner:** Gilead Sciences Inc
- **Granted:** 2013
- **Status:** Active
- **Times cited:** 19
- **Field:** biotech, pharmaceutical

## What it does

The patent claims a specific pharmaceutical recipe that combines 300 mg of tenofovir disoproxil fumarate and 200 mg of emtricitabine into one oral pill. Because these two chemicals are chemically incompatible and tend to degrade when mixed, the patent specifies a precise blend of binders, disintegrants, and lubricants—such as pregelatinized starch and magnesium stearate—to stabilize the mixture. This ensures the pill remains effective for at least six months, even under high-heat and high-humidity conditions, by preventing the active ingredients from breaking down into inactive or harmful components.

## What it does NOT cover

- Does not cover the individual chemical structures of tenofovir disoproxil fumarate or emtricitabine themselves.
- Does not cover combinations of these drugs with other active ingredients not specified in the claims.
- Does not cover dosage forms that do not meet the specific stability requirement of less than 10% degradation over 6 months at 40 degrees Celsius.
- Does not cover liquid or injectable versions of these drugs.

## The clever bit

The innovation lies in solving the chemical incompatibility between the two drugs, which otherwise react to degrade each other. By selecting specific excipients that act as a buffer, the inventors created a stable solid-state environment that prevents this degradation.

## Real-world examples

1. Truvada

## Why it matters

This patent is the foundation for Truvada, a landmark medication in HIV treatment and prevention. By combining two drugs into one pill, Gilead significantly improved patient compliance, as taking one pill daily is far easier than managing multiple separate medications. This innovation helped transform HIV from a fatal diagnosis into a manageable chronic condition.

## Frequently asked questions

### What does How Gilead Made a Stable HIV Pill Combining Two Medicines cover?

This patent describes a stable, single-pill combination of two HIV drugs, tenofovir disoproxil fumarate and emtricitabine, designed to prevent them from breaking down when stored together.

### Who owns patent US 8592397?

Gilead Sciences Inc owns this patent, granted in 2013.

### When does this patent expire?

This patent is expected to expire on November 26, 2033, when the invention enters the public domain.

### What is patent US 8592397 cited by?

This patent has been cited by 19 later patents that build on its ideas.

### What problem does this patent solve?

This patent is the foundation for Truvada, a landmark medication in HIV treatment and prevention. By combining two drugs into one pill, Gilead significantly improved patient compliance, as taking one pill daily is far easier than managing multiple separate medications. This innovation helped transform HIV from a fatal diagnosis into a manageable chronic condition.

### What does this patent NOT cover?

Does not cover the individual chemical structures of tenofovir disoproxil fumarate or emtricitabine themselves.

**Full plain-English explainer:** https://patentbrief.org/patent/us/8592397/truvada-tdf-ftc-for-prep

**Original patent:** https://patents.google.com/patent/US8592397

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