A new class of drug that has the potential to help cancer patients, especially those suffering from breast cancer and who no longer respond to existing therapies has been discovered.

Breast cancer patients frequently become resistant to existing treatments, leading to the disease becoming fatal. Early lab-based tests of a drug named ICEC0942 were successful in targeting resistant breast cancers and indicated minimal side effects. "Treatment-resistant tumours represent a significant threat for patients, as once a cancer stops responding to treatments there is increasingly little clinicians can do," said Charles Coombes, Professor at Britain's Imperial College of London.

"Drugs such as these could help to shift the balance back in favour of the patients, potentially providing a new option to patients for who existing treatments no longer work," Coombes added. The findings, published in the journal Molecular Cancer Therapeutics, noted that the drug targets an enzyme called CDK7 -- involved in directing cells through their lifecycle, which consists of growth, DNA replication and cell division. CDK7 is also involved in the process of transcription -- a vital step in gene expression -- the creation of proteins to carry out cell functions.

Particular cancers, such as treatment-resistant breast cancers, have a unique dependence on transcription, meaning targeting CDK7 may be particularly effective. By inhibiting transcription, ICEC0942 shuts down the ability of the cancer to spread. In addition, cancers such as acute myeloid leukaemia and small-cell lung cancer are particularly transcription-dependent. Therefore, ICEC0942 drug may also work well for these too, especially where they have become resistant to other treatments, the researchers suggested.