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This section contains information on two novel types of targeted cancer drugs known as DDR (DNA damage response)-targeting agents and PARP (poly-ADP ribose polymerase) inhibitors. We aim to bring you important information on how these drugs work and how you can work with your healthcare professional to manage any changes that may occur during treatment (known as adverse reactions).

Important to Know

PARP inhibitors and agents that target DDR have been shown to be useful for the treatment of a number of tumour types. In some cancers they can be used as an alternative to chemotherapy. In other cancers, these drugs can be used to prolong the time until the disease returns.

PARP inhibitors target PARP molecules found in cells, which helps cells repair themselves from damage to their DNA. PARP inhibitors work by blocking PARP protein, which stops PARP from repairing cells which leads to cell death. 

The BRCA gene in cancer cells can be faulty in some patients - known as a BRCA mutation. This is one of the reasons why you may have been tested for the BRCA mutation (for further information on BRCA testing it is recommended that you speak to your doctor). Patients with a BRCA mutation have an increased risk of developing some cancers.  If you have a BRCA mutation your doctor may suggest that you are given a PARP inhibitor as evidence suggests that PARP inhibitors may be effective in patients with BRCA mutations.

Agents that target DDR are similar to PARP inhibitors except they target other molecules involved with DNA damage or repair, rather than PARP. These drugs are not yet available for clinical use but you may receive them as part of a clinical trial.

Side effects

  • Adverse reactions mentioned usually respond well to treatment and generally disappear when cancer treatment is stopped. In some cases, treatment is not needed and the adverse reactions resolve spontaneously.
  • The earlier an adverse reaction is reported and treated, the better it can be managed.
  • Side effects are usually milder than chemotherapy.
  • You should tell your nurse, doctor or pharmacist if you notice any of the following symptoms during or after treatment. You may be able to have medicines to help control them:
    • Tiredness, being short of breath, pale skin or fast heart beat – these may be signs of a low red blood cell count (anaemia).
    • Feeling sick (nausea)
    • Diarrhoea
    • Any other unusual symptom

For more information about all of the recorded the side effects of your treatment and how to take it, talk to your healthcare provider and also the individual drug web pages.

DOs and DON’Ts


  • Maintain frequent communication with your doctor/nurse during treatment.
  • Contact them as soon as any adverse reactions occur. It is very important that if the adverse reaction occurs, it is treated immediately.
  • Speak to your doctor before you take any herbal supplements, such as St John’s Wort.


  • Worry about contacting your healthcare provider. If you have any concerns, they are more than happy to help you. It is also important that you report any symptoms to them as soon as possible.
  • Consume grapefruit juice/Seville oranges

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