Where have all the promising treatments gone? The challenges of clinical trials.

Identifying the right patients to recruit for clinical trials of a new drug is a key component of a trial's success.
Identifying the right patients to recruit for clinical trials of a new drug is a key component of a trial’s success.

Many of the scientific breakthroughs we read about in the media discuss discoveries in the lab that could be translated to promising therapies, or exciting new drugs that have just entered clinical trials. Months or years pass with no further mention of this amazing treatment. What happened?

It’s tempting to hope that a newly discovered, promising drug could be used by patients within the next year. However before a drug can be used in the clinic, researchers need to evaluate its performance in small cohorts of volunteers and patients. I will briefly discuss the three phases of clinical trials below; you can read more about them here.

Why are cancer treatments so expensive?

In 2009, the estimated average cost of a clinical trial in the US was US$1.3-1.7 billion, and those costs continue to rise. With so many new drugs being developed, and many new advances in cancer treatments, it’s getting harder to prove that a new drug is significantly better than the existing options. In order to detect these incremental improvements, trials are recruiting more patients, for longer periods of time, and are using more advanced (and expensive) monitoring techniques, such as MRI or genome sequencing. All of this contributes directly to high drug costs once a treatment hits the market.

Why do clinical trials fail?

Considering the time and cost that goes into establishing a clinical trial, it is surprising to learn that over 62% of Phase III trials in the US fail – meaning that the investigated drug is not better than the current standard of care. There are many reasons for this, including a trial that may not have been properly designed. For instances, a drug might be effective in a small percentage of patients with specific characteristics, however if a clinical trial is conducted in a broader population, the effectiveness of the drug on the small percentage of “responders” will be lost within the larger population, resulting in failure of the trial.

What does the future of clinical trials look like?

In an effort to design clinical trials that have higher rates of success (and are therefore more beneficial for patients), researchers are moving away from large scale trials with diverse patient populations, and more towards smaller trials of targeted patient groups. For example, by categorizing cancer patients by the genomic profile of their tumours, and recruiting only a defined subset of patients that are likely to benefit from treatment, current clinical trials are starting to improve their success rates.

The high costs and high failure rates of clinical trials are certainly cause for concern, however it’s important to remember that drugs do succeed, and many have dramatically changed the face of cancer treatment. For example, the drug Herceptin is a monoclonal antibody that targets a specific protein called HER2, which is thought to drive tumour growth. This oncogenic protein is over-expressed in the tumours of 25-30% of breast cancer patients. When the Herceptin antibody was evaluated in clinical trials, it was tested on patients whose tumours over-expressed HER2. Because of this effective design of the clinical trial, researchers were able to capture the positive effects of this drug that would have otherwise been lost had it been tested on patients with and without HER2 over-expression. Since its development in 1990 and approval by the FDA in 1998, Herceptin has had a tremendous impact on the treatment of patients with HER2+ breast cancer.

New cancer treatments are being approved every year, some of which have met with great success. The hope is that as more drugs make their way successfully through clinical trials, patient outcomes will continue to improve.

This article was written by Ashley Hickman. Ashley is in the second year of a Masters program at the University of Toronto where she studies how to regulate a very important cancer causing gene called myc. To learn more about Ashley and her research check out her bio on our members page.

References:

Amiri-Kordestani, L. & Fojo, T. Why do phase III clinical trials in oncology fail so often? J. Natl. Cancer Inst. 104, 568–569 (2012).

Collier, R. Rapidly rising clinical trial costs worry researchers. CMAJ 180, 277–278 (2009).

Phases of Clinical Trials. http://www.cancer.ca/en/cancer-information/diagnosis-and-treatment/clinical-trials/phases-of-clinical-trials/?region=on

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