“STOP EATING CHOCOLATE. IT IS TOXIC!” would have been a news headline if chocolates were to undergo safety and toxicity testing on dogs before allowing human consumption.  We know that chocolates are toxic and can cause significant illness in dogs, which means that it could have failed the animal tests. We could have never tasted the delicious treat despite it being completely safe for humans.

Fortunately, this was a hypothetical scenario as chocolates weren’t subjected to animal testing and have been around for more than 5000 years now. 

Are you wondering about the intention of posing such a scenario? Because sadly this is what is happening during the development of new drugs for diseases. Before the drugs are tested on humans, they are subjected to tests on animals to assess their safety and toxicity. Mice are the gold standard for animal testing but sometimes non-human primates are also used in exceptional cases. There is no denying that animal testing has helped medicine to evolve to such great heights, but they have some grave limitations. 

Statistically, 9/10 drugs for cancer therapy that pass the animal testing, fail on humans in the clinical trials.

This is worrying for many reasons such as – 

  • High throughput analysis of drug candidates is a tasking challenge. For example, there are 1000 drug candidates that would possibly work against disease. That means, at least 1000 animals should be used for this step. Imagine if the number goes up to a lakh or a million!
  • Animal testing is very expensive and requires huge capital. 
  • Animal testing is a lengthy process and takes up a lot of time.

Considering all the above factors, animal testing actually delays the discovery of important therapeutics.

Other alternatives were of no use – In addition to animal testing, researchers started testing drugs on human cells to overcome the limitations of the former. The cells derived from humans were transferred and grown in a dish in the laboratory. But guess what? Cells do not portray their inherent characteristics in these dishes. Inside the body, cells are in a dynamic environment where they are in contact with neighboring cells and also the complex microenvironment. This lack of complexity in cells in dishes generates inaccurate and unpredictable results. There was an urgent need to develop a suitable ‘home away from home’ model for the cells. 

Organ on a chip : A ray of hope – Researchers across the globe acknowledged this and worked to develop a magnificent tool called organ-on-a-chip (OOC) for efficient testing of drugs. For instance, at the Harvard Wyss Institute, researchers developed a lung-on-a-chip that showcased all the functionalities of a lung. Organ-on-a-chip, thus is a top emerging innovation built through a combination of cell biology, engineering, and biomaterial technology. It is an innovation that can change the future of drug testing and could minimize animal testing. 

OOC is a micro-engineered device that fits in the palm of your hand. As it is based on microfluidic technology, it is operated at a micro-scale which requires less quantity of cells, nutrients, and everything that needs to be tested. Here the cells derived from humans are grown in 3 dimensions which preserves the cell-cell interaction and also the cell-environment interaction. Organ on a chip does not visually represent any human organ, but it mimics the functioning of an organ and also the mechanical forces that act on the cells inside the body. 

Where can it be used? – OOC is a great tool to minimize the burden on animal models, as they are an ideal fit for preclinical drug testing as it mimics the internal state of the human body. It provides better accuracy than 2D cultures and animal models and generates reliable data in relatively lesser time. Through these chips, it is possible to screen thousands of drug candidates and is thus deemed as a sustainable model. It also makes economic sense to transit from animal testing to using organ-on-chips as they are affordable. 

You can read more about organ-on-a-chip here.