Deciphering Medical Research, Part 2: Preclinical vs. Clinical Research

by Gwen on February 10, 2011

© 2012 Carl H. Stritter All rights reserved.

(See Part 1 in this series of articles, Deciphering Medical Research, here)

To rapidly determine the likely effectiveness of the research drug or nutriceutical du jour, it is important to know the difference between pre-clinical and clinical research. Pre-clinical studies are either in vitro or in vivo.

In vitro research is done on breast cancer cells in a laboratory. Unfortunately, what works in the test tube, often does not work in a human being.

A case in point: if I poured bleach on cancer cells in a test tube, the cancer cells would surely die. Does this mean that those with cancer should be drinking bleach? Of course not. So we see a big weakness in test tube research – it does not give you information on drug safety.

Also, you can’t assume what works in the test tube will automatically work in a living organism. That’s like trying on a pair of sunglasses in a dark room. Sure they will work well there, but does that mean they will work in a different environment, like outside on a sunny day?

So when a drug or herb or supplement is shown to kill cancer cells in vitro, I no longer get very excited. It still has to jump over many other hurdles before it being proven to be safe and effective.

The next step in the drug development process is in vivo research, which is done on living animals. Rats are commonly used. They are genetically engineered so that researchers can give them human breast cancer (as opposed to rat breast cancer). Then they give research drugs to the rats to see if the breast cancer stopped growing or dies.

Lots of people don’t realize that we have been able to cure breast cancer in rats for years. Unfortunately, that has not translated into a breast cancer cure for humans.

Here’s an example. In 1994, researchers found that when they gave rats with human breast cancer a new immunotoxin (called BR96 sFv-PE40), they were 100% cured. [1] Unfortunately, when they tested the drug in humans in 2002, they found serious side effects and 0% cure.[2]

So when a drug cures cancer in rats, mice or any other laboratory animal, I don’t get very excited about it any more. There are still other hurdles!

Having pointed out the deficiencies of preclinical research, let’s talk about clinical research (trials done on human beings). It turns out that research done on those who actually have breast cancer is the most useful. If a drug improves survival and has few adverse effects in this setting, it will likely apply to others with the same type of breast cancer. Unfortunately, this is the most expensive research to conduct. That is why herb and supplement manufacturers typically don’t fund clinical trials – they cost millions and there aren’t any patent profits to pay for them. That is also why typical physicians, especially those in academic institutions are against using herbs and supplements – there is very little of the gold-standard research, which forms the basis for breast cancer treatment guidelines, to support their use.

In conclusion, it’s important to understand the differences between in vitro research, in vivo research, and clinical trials. If it wasn’t a clinical trial then the chances that the researched drug will work in humans are very small. While I have heard many in the drug development industry cite a very low figure (<5%) for successful navigation from preclinical drug to FDA-approval, I have not been able to find a scholarly article on this subject. I would love to hear from any of my readers that could refer me to such information!

Addendum 3/1/12:  I found two sources.  One says that < 1% of preclinical research eventually passes phase 3 clinical trials [3].  The other quotes a slightly higher number, 10% [4]

Want to know how to spot biased research reports? Check out the 3rd installment in this series, Deciphering Medical Research, Part 3: Why Bias Matters


[1] Siegall CB et al; J Immunol. 1994 Mar 1;152(5):2377-84

[2]Posey JA et al; Clin Cancer Res. 2002 Oct;8(10):3092-9

[3]The Pharmaceutical Research and Manufacturers of America; Drug Discovery and Development: Understanding the R&D Process  (Navigate to the “Drug Discovery and Development” link; page 23)

[4]Gassmann O et al; Leading Pharmaceutical Innovation: Trends and Drivers for Growth in the Pharmaceutical Industry; 2nd ed, 2008  (figure 8, page 11)

© 2011 Gwendolyn M Stritter, MD. All rights reserved.

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*Information on the Breast Equity blog is provided on an “as is” basis for general information only. It is not intended as medical advice and should not be relied upon as a substitute for consultation with a qualified health professional.*

© 2011 – 2012, Gwen. All rights reserved.

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