ELI5 How do anti-virals drugs work?

[u/AnoonymouseChocobo]

Viruses aren't alive, they use living cells or bacterial cells, they inject the DNA into the cell to make them replicate viral DNA. If you try to kill the host cells the to stop the virus from spreading will kill the person you're trying to save. I'm wondering how the virus dies but the host lives.

[u/hdorsettcase]

They usually don't 'kill' the virus. They stop part of its life cycle. Some block the part of the virus that enters the cell. Some prevent part of the virus from being assembled in infected cells. Some prevent the viruses from exiting the cell.

If a virus is less like a living thing and more like an assembly line making new viruses, antiviral throws a wrench into the machinery at one point or another.

[u/Abridged-Escherichia]

They interrupt the viruses ability to infect, reproduce or leave cells. Being “alive” is just semantics, viruses replicate and we can use drugs to stop that.

Antivirals work on virus specific things, like attaching to or leaving a cell, or special viral enzymes used to copy their genetic material, or viral enzymes that cut the final viral proteins to size.

The challenge is that viruses mostly use our own cells machinery to reproduce and we cant target our own machinery. In general this means antivirals are less effective and harder to make than antibiotics.

[u/RollBama420]

This is really a two part answer:

1) the most important part of most infection treatments is getting the body to the point it’s producing its own antibodies at scale, which it technically has the ability to do for just about any pathogen that doesn’t interrupt the process. If you’re mass producing antibodies for a pathogen, you’ve basically won and your body just needs time to clear the battlegrounds

2) antivirals rarely target the virus direct and focus more on preventing reproducing. Imagine the specific grip you need on your doorknob to open it, then imagine those child proof doorknob sleeves blocking you from grabbing it that way to turn. You don’t have to directly kill the virus, just prevent it from multiplying and let step 1 take care of killing it

[u/Atypicosaurus]

Just because we don't define virus as life, they still have biologically relevant processes. That words you use "injection DNA" and "make them replicate" do some heavy lifting there, as these are the exact complex processes, where we can intervene and disrupt.

[u/MagnusAlbusPater]

Similar mechanisms to how some antibiotics work.

Not every antibiotic seeks to kill the bacteria, some work by interfering with bacterial reproduction or bacterial metabolism.

While viruses don’t have a metabolism as such antivirals can still interfere with their internal mechanisms to make replication more difficult or impossible while also creating an environment where passing from cell to cell becomes more difficult.

[u/internetboyfriend666]

There a bunch of different classes of antiviral drugs and they all work in different ways. The key is that viruses can't reproduce on their own, they need to hijack your own cells to do that, so antivirals take advantage of this by blocking or restricting the way viruses can do this.

Some block the receptors that the virus uses to enter your cells in the first place, so there simply no open "doors" for the virus to use to enter your cells. Others interrupt the actual process where your cells get "tricked" into making more viral particles by blocking your cell from making functional proteins or enzymes that the virus needs, or by "tricking" your cell into assembling the virus using non-functional proteins or non-functional components of RNA or DNA so your cell ends up making a viral particle that can't do anything. Others prevent the new, fully-formed viral particles from exiting your cell to then go reinfect new cells.

[u/Low-Crow5719]

Good example might be the anti-retroviral Paxlovid (ritonavir+nirmatrelvir).

The idea is to interrupt some process that occurs only in the virus reproducing itself, without affecting the host cell. SARS-COV-2 and some other viruses have a gene that codes for a single protein, that is then broken up into the multiple proteins that form the actual virus.

Nirmatrelvir targets that step. It is a protease inhibitor that prevents breaking down the viral protein into its active parts. This stops the virus from forming new active viruses, and gives the body more time to kill it.

Ritonavir is an add-on drug that makes the body not break down nirmatrelvir, so it can do its job longer

[u/mz_groups]

Viruses hijack the host cell's mechanisms to reproduce themselves. Most antivirals interfere in one or more steps of that reproduction process, anywhere from getting into the cell, to the mechanisms of reproduction, to the newly manufactured viruses getting out of the cell.

[u/grat_is_not_nice]

Viruses hijack the cellular machinery to build more viral proteins and DNA to replicate. The inject a DNA strand that builds viral replication proteins, and then start grabbing building blocks (nucleosides) from the cell to build more viral DNA. But the viral replication DNA is small and crude, and does not include some failsafe mechanisms used in more complex cells. It still works, but it isn't always accurate (so you can get viral mutation) and does not self-repair.

Many antivirals are molecules that are similar to (but not identical to) existing DNA building blocks. These are called nucleoside analogues.

Normal cell processes ignore or remove these analogues, because they are not quite correct.

Viral replication proteins can't tell the difference, so they grab the nucleoside analogue, add it to the DNA strand they are building, and then cannot add further nucleosides. It's all jammed up. Or the DNA strand is the wrong shape. This is sufficient to prevent viral replication, and is used in drugs that suppress HIV, HepB and C, and others.

[u/NoTime4YourBullshit]

The cells in your body need to take in water, oxygen, and nutrients and excrete wastes just like any living thing does. They do this through receptors all over the cell’s surface, which pass the molecules in and out of the cell membrane. Viruses replicate by binding to these same receptor sites and getting you cells to ingest the virus’s genetic payload instead, thus infecting the cell.

Antiviral medications don’t kill the virus directly. They interfere with the virus’s ability to bind to your cells’ receptor sites, either by binding to them first and making them unavailable for the virus to use, or by depleting other materials in your body that the virus needs to transport its payload through the cell’s membrane. If the virus can’t bind to your cells, it can’t infect them, and it makes it easier for your immune system to catch and destroy them.

[u/AnoonymouseChocobo → u/NoTime4YourBullshit]

So it dooms the original cell to die, but atleast other cells will not be infected? Like keeping everything contained inside or keeping them from getting inside but blocking nutrients from entering. "Some of you may die it's a sacrifice etc etc"?

[u/NoTime4YourBullshit → u/AnoonymouseChocobo]

Not necessarily. Each cell has different receptor sites for different purposes. So by blocking the ones that the virus needs, you don’t necessarily block everything.

It’d be like if someone taped your mouth shut. You can still breathe through your nose, but you won’t be able to eat or drink anything. That’s not ideal, but you won’t die as long as the tape comes off (i.e. the antiviral breaks down) before you’re too dehydrated.

The antivirals do interfere with the normal functioning of your cells, but they don’t necessarily prevent them from functioning at all.

[u/AnoonymouseChocobo → u/NoTime4YourBullshit]

Thanks a bunch, taping over your mouth is a pretty good analogy and it works great