Adverse event: Side effects of a drug that range from Class I (mild or no side effects) to Class V (death). 

Alanine transaminase: A protein that normally exists in the liver that is used to measure liver health and drug toxicity. When the liver is damaged alanine transaminase is released into the blood, so high blood levels mean more liver damage and the drug is more toxic.

Compliance: When patients stick to the dosing regimen of a drug (take the medication as prescribed).

Drug cocktail: A mixture of anti-HIV drugs that patients take to decrease the likelihood of HIV resistance to one drug developing.

Efficacy: How well the drug works (how well it lowers the amount of HIV in the body).

HIV: Human Immunodeficiency Virus; a virus that attacks immune cells (CD4 T cells) in humans making them vulnerable to infections. Can lead to AIDS.

Half-life: The amount of time it takes for the level of the drug in the bloodstream to drop by half. Longer drug half-lives mean the patient does not have to take the drug as often.

Negative control: An experimental group that should not show a response.

Metabolize: To break down a substance in the body. Drugs are typically metabolized in the liver. 

Opportunistic infection: Infection not usually seen in healthy individuals because people with HIV are not as good at fighting off disease-causing organisms. 

Phase I trial: The first stage of testing a new drug in people; drugs are tested on a small group of healthy individuals to determine how toxic the drug is. This is the stage at which dosing is determined.

Phase II trial: The second stage of testing a new drug in people; drugs are tested in a small group of sick people to discover side effects and to see if it’s effective. 

Phase III trial: The third stage of testing a new drug in people; drugs are tested on a large group of sick people.

Preclinical trials: Before new drugs are tested in humans, they are tested in cell and animal models to look at efficacy and toxicity.

Remission: When the viral load is so low that there is no evidence of the disease in the body (no symptoms).

Resistance: When a HIV strain (type) no longer responds to a drug because the virus has mutated. 

Standard of care: The most commonly used disease treatment in current use that also best fits the patient’s needs. For HIV, this is often a cocktail of several drugs.

Toxicity: How much damage a drug causes the body (how many side effects and how serious those side effects are).

Viral load: The amount of virus in the blood.

Virologic failure: When the drug treatments stop keeping the HIV virus in check.

Virus: Uses living cells (host cells) to replicate, or make copies of itself, often killing the cell.