Clinical Trial Probability of Success? Just How Probable Is A Great Outcome.

The cost and time of well-designed clinical trials is growing rapidly, but just how probable is it that the data will be sufficient to support regulatory approval and market success? Dr Michael Silverman, principal at BioStrategics Consulting Ltd., discusses the probabilities, the time commitment and costs involved in bringing a successful new drug to market?

The cost and time to bring new drugs to market are staggering, and it is not getting any easier, quicker or cheaper, which means longer waits and more expensive treatments for the most part.

The latest figures presented at a recent industry conference in 2011 suggest that the time to bring a new drug through the preclinical, clinical and regulatory approval process is approximately 13-15 years and costs approximately $1.2 billion. If the cost of failure is added in, it is closer to $2 billion.

The statistics are staggering. In 2007, Morgan Stanley estimated that to end up with one drug in the market, it is necessary to screen 5-10,000 molecules which are then whittled away through testing for safety and efficacy towards are particular treatment of a disease, which means you have to be ready to invest in 9,999 other molecules that will fail. Thomas Edison springs to mind. Certainly most molecules are abandoned before testing in man, and only the best, most active and most likely not to cause harm move into the clinical phase of drug development. As a product enters clinical trials the probability that it will eventually gain approval for marketing is quite low. In 2011, the latest probabilities of success relating to the start of a clinical phase in a drug’s development, were reported as follows:

Stage of Development               Probability of Approval

  • Phase 1                                                       9%
  • Phase 2                                                     15%
  • Phase 3                                                    44%
  • Submission                                            80%

The “Success Rates” at different phases of clinical testing was also reported.

Clinical Trial Phase      Probability of Success

  • Phase 1                                    63%
  • Phase 2                                    33%
  • Phase 3                                    55%
  • Approval                                 80%

It is not totally surprising to see that most of the failure occurs in Phase 2 clinical studies. Phase 1 clinical studies are largely focused on safety in man, and have already been broadly tested in a number of animal models before hand. However, at Phase 2 the clinical studies are not only larger so one can discover more regarding toxicities, but it is at this stage that the ability of the drug is usually first tested to see if it is effective in bringing about the required therapeutic effect. This is where many drugs stumble.

In the larger still Phase 3 or pivotal clinical studies it is here where the drug is exposed to a broader array of patients and has to show strong statistical evidence that the drug is effective and safe. Although overall the success rate is 55%, the rate does differ between different therapeutic areas:

Probability of Success at Phase III by therapeutic area:

Therapeutic Area                                 Probability of Success

  • Autoimmune:                                             63%
  • Respiratory:                                               61%
  • Endocrinology:                                          60%
  • Infectious disease:                                     55%
  • Neurology:                                                  55%
  • Cardiovascular:                                         46%
  • Oncology:                                                   34%

The lowest success rate is in the treatment of cancer where we still have a long way to go to truly understand all the mechanisms in play.

Drug development is not for the feint of heart. It is highly risky, expensive, and takes a long time to realize a return, if any. The strategy and tactics behind testing these products in man clearly must be done with considerable planning and thoughtfulness by an experienced team of drug development professionals.

Dr Michael Silverman is the principal clinical consultant at BioStrategics Consulting Ltd., a clinical development consulting company based in Marblehead, MA, with business interests around the globe. Dr Silverman would be delighted to hear your thoughts on today’s blog, your experiences, or anecdotes and of course, your questions. To make comments or ask questions, click on this link.


  1. The Clinical Development Plan Guide
  2. The Prospective Patient Package Insert Guide
  3. The Clinical Trial Protocol Guide

To receive a copy of the guide(s), visit Contact Us page or send an email to with your name and email address.

For more information: go to the BioStrategics Consulting Ltd website or send me an email at

BioStrategics Consulting Ltd provides a range of management-level clinical development consulting services to the pharmaceutical, biotechnology and medical device industries, including: Clinical development strategy and management, conceptualization, implementation, and management of Phase 1, Phase 2, first-in-man, and proof-of principle clinical trials, IND planning and preparation, FDA and other regulatory authority submissions, meetings, and related interactions, Clinical strategic planning for small molecules, biotechnology products, immunotherapeutic agents, novel drug delivery technologies, and medical devices in virtually all therapeutic areas, New technology assessment, due diligence, and program planning, Clinical development advisory services to senior-level management (CEO, COO, CSO, BOD).

Copyright © 2011 BioStrategics Consulting Ltd.


About BioStrategics Consulting Ltd

BioStrategics Consulting Ltd provides a range of management-level clinical development consulting services to the pharmaceutical and biotechnology industries
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