Targeted drugs reduce attrition rates

The results of a new study published in the 14th November online edition of Nature Reviews Drug Discovery (10.1038/nrd2758) suggest that advances in drug development have led to an increase in the number of drugs reaching cancer patients. Scientists from Cancer Research Technology (CRT; Cancer Research UK [CRUK]) obtained data on 974 cancer drugs in clinical development, and calculated that there was a probability that 18 per cent of those entering the clinic would make it to market. Previously it was estimated that in some studies only 5 per cent of cancer drugs in the pipeline become standard treatments for the disease.

The data search was limited to agents which entered Phase I trials after January 1995 and before September 2007, of which 137 are the molecularly-targeted drug class, kinase inhibitors. The research showed that kinase inhibitors were almost three-times more likely to reach patients than other types of anticancer drug. The investigators believe that a better understanding of the basic biology of cancer has enabled the development of this type of new drug, which includes Herceptin (trastuzumab) for breast cancer and Glivec/Gleevec (imatinib) for leukaemia.

The study highlights the fact that understanding more about the basic biology of cancer is making a real difference to the success rate of new anticancer drug development. Additionally, improved drug-discovery processes and advances in medicinal chemistry have also contributed to better success rates of drugs in development. Furthermore, better understanding of a patient's genetic make-up and how they will respond to certain drugs has led to improvements in clinical trial design.As drug development continues to advance, minimising the number of drugs which fail to make it to market will remain key as the cost of discovery and development of those drugs which do not reach market is borne by those that do. The true cost of a drug reaching the market has recently been estimated to be US$0.8 billion to US$1.0 billion.

According to one of the study authors, Professor Herbie Newell, Director of Translational Research at CRUK: "We strongly believe that both industry and academia must improve the availability of data related to failed as well as successful drug development programmes. The sharing of such information can only be beneficial for clinical, scientific and commercial reasons, and will help measure our progress as well as pinpoint areas for improvement."

Historically, the oncology pipeline has been largely made up of small-molecule cytotoxic drugs, which have a low therapeutic index and can fail in clinical trials due to toxicity or efficacy reasons. The recent explosion of information coming from work into understanding the molecular basis of cancer has led to an increase of drugs targeting specific pathways, drugs that are specifically designed to treat cancer, rather than randomly killing proliferating cells. As more information becomes available and newer drugs that are better targeted move into the pipeline, the attrition rate for cancer drugs may reach levels seen with other therapy areas, such as cardiovascular disease where 20 per cent of agents in development reach the market.

Matthew Dennis - Editor, Cancer Drug News