---
title: What are in-vivo models for research?
description: The selection of the correct in vivo model is key during the drug discovery process. Learn all about this in this new article!
---

[Blog](https://blog.biobide.com)

# [What are in-vivo models for research?](https://blog.biobide.com/what-are-in-vivo-models-for-research)

 Written by [Sample HubSpot User](https://blog.biobide.com/author/sample-hubspot-user) | Jun 10, 2022 8:27:02 AM

There are **two forms** of research in pharmaceutical testing: [***in-vivo* and *in-vitro***](https://blog.biobide.com/in-vivo-vs-in-vitro-differences-in-early-drug-discovery) (Latin names). *In-vivo* means **‘within the living’** and occurs on a living organism, while *in-vitro* means **‘in glass’** – the testing often takes place on cultured cells in a glass testing receptacle.

[***In-vivo*** **models**](https://www.roche.com/research_and_development/what_we_are_working_on/research_technologies/translational_technologies/in_vivo_models.htm#:~:text=In%20Vivo%20Models%20are%20a,starting%20clinical%20studies%20in%20humans.) are animals that are live (as opposed to experimentation on dead organisms). They can be rodents, dogs, cats, rabbits, pigs, fish or other animals and are specially bred for this purpose. Mice are the most commonly used model, one reason being their genetic make-up is similar to that of humans.

This article discusses ***in-vivo* research models and their advantages**.

## **How are *in-vivo* models used in drug discovery?**

***In-vivo* models** are used to test the effect a drug has on a **human disease or human organs**. They are a safe way to carry out research prior to a drug going to clinical trials on humans. Before a drug can be approved and marketed it goes through [several stages](https://blog.biobide.com/the-drug-discovery-and-development-process-in-pharma-and-biotech). This process can take 10-12 years and costs on average $1.3 billion.

The research stages are:

- **Drug discovery** – the potential for a new pharmaceutical product.
- **Target identification** – identification of the disease/pathway to be targeted.
- **Hit identification** – the molecules that will act on the target.
- **Lead generation** – analysis of the performance of the drug on the target – this is when *in-vivo* testing takes place using animals or alternative models.
- **Lead optimization** – further study of the behavior of the drug, again using *in-vivo*
- **Clinical trials** – using human volunteers.

*In-vivo* testing is essential for accurate medical research although it may bring ethical problems if carried out on live animals. This makes alternative ***in-vivo* models for research** such as **zebrafish an ideal candidate**.

## **Is *in-vivo* research better than *in-vitro*?**

 Most *in-vivo* tests are believed to be more accurate than *in-vitro* as they **demonstrate the effect and toxicity of a substance on a living subject**. This tends to give more reliable results as an *in-vivo* test can replicate the impact on the living human body.

*In vitro* testing has limitations as it can only be performed on individual cells whereas *in-vivo* allows the study of the interaction between cells.

Genetic engineering allows the manipulation of cells to replicate how a substance can affect them. This is essential for new [drug discovery](https://blog.biobide.com/the-drug-discovery-process) to combat the many diseases that exist in today’s society. Cancer and [Alzheimer’s disease](https://biobide.com/tags/alzheimer), for example, still have no cure. Any research model that can speed up the process to discover drugs that can fight these common human diseases is beneficial.

## **Alternative models for *in-vivo* research**

 **Zebrafish are a unique alternative research model** as they sit between *in-vivo* and *in-vitro* testing. Although they are live when hatched the embryos are not classed as *in-vivo* until 5-6 days after fertilization. However, during these 5-6 days the embryo has totally formed and reacts to testing as if it were a live organism.

The table below shows the **differences between zebrafish and mice** for research purposes.

|  | **Zebrafish** | **Mice** |
| --- | --- | --- |
| Life cycle | 10-12 weeks | 50-60 days |
| Number of offspring | 100-300 eggs per week | 6-12 pups per month |
| Maturation time | 3-4 days | Approx. 20 days |
| Number of neurons | Approx. 10,000,000 | + 70,000,000 |
| Economical husbandry | Yes | Not as much as zebrafish |
| Organ regeneration | Yes | No |

 At Biobide we realize that the **rapid breeding time and**  the **cost-effective** zebrafish model are major advantages in pharmaceutical research, allowing the entry in clinical drug trials at earlier stages than in the past.

The zebrafish has an **added benefit** as it complies with the [EU 3Rs policy](https://blog.biobide.com/the-3rs), which states that research on animals should be humane and ethical. The policy aims to:

- **Reduce** – minimize the number of animals used in experiments.
- **Refine** – protect animal welfare and minimize suffering.
- **Replace** – replace animal testing with alternative models.

Finding a solution to **treat and cure the many global diseases** that exist is essential. The development of models such as zebrafish has expediated and developed research methods dramatically over the past few years. Whilst there are **many forms of *in-vitro* testing** that offer an alternative to animal testing, *in-vivo* continues to play an important role in pharmaceutical research.

[View full post](https://blog.biobide.com/what-are-in-vivo-models-for-research)

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