Olaparib (Specialist drug)

How it works

It inhibits poly(ADP-ribose) polymerase enzymes involved in DNA single-strand break repair, causing synthetic lethality in tumour cells deficient in homologous recombination, such as those with BRCA mutations.

Prescribing in practice

• Haematological toxicity including anaemia, neutropenia and thrombocytopenia is the key concern, and rare cases of myelodysplastic syndrome or acute myeloid leukaemia have occurred, so a baseline and ongoing full blood count is essential and persistent cytopenias must be investigated.
• It is a CYP3A substrate, so avoid strong CYP3A inhibitors and inducers where possible and adjust as advised in the SPC.
• It is teratogenic and embryotoxic, requiring effective contraception during and after treatment.

Monitoring

Monitor full blood count monthly, watch for prolonged cytopenias suggestive of secondary malignancy, and assess renal and hepatic function and respiratory symptoms as guided by current prescribing references.

Counselling the patient

• Take the tablets whole and report unusual tiredness, bruising or bleeding.
• Use reliable contraception and tell us if you could be pregnant.
• Mention new or worsening breathlessness or cough.

Evidence & guidelines

Its cancer indications are supported by randomised maintenance and treatment trials showing prolonged progression-free survival in homologous-recombination-deficient tumours.