Although most ovarian cancer patients initially respond to platinum-based chemotherapy, most will eventually experience a return (relapse) of their cancer. Treatment of metastatic breast cancer often includes chemotherapy, but options can become limited when the cancer stops responding to conventional chemotherapy regimens. Outcomes remain poor after treatment of relapsed disease, and researchers continue to explore new approaches to treatment.
Targeted therapies are anticancer drugs that interfere with specific pathways involved in cancer cell growth or survival. Some targeted therapies block growth signals from reaching cancer cells; others reduce the blood supply to cancer cells; and still others stimulate the immune system to recognize and attack the cancer cell. Depending on the specific “target,” targeted therapies may slow cancer cell growth or increase cancer cell death.
Olaparib is an oral investigational drug called a PARP inhibitor. The PARP enzyme plays a role in DNA repair, including the repair of DNA damage from chemotherapy. Drugs that inhibit this enzyme may contribute to cancer cell death and increased sensitivity to chemotherapy.
Cancers that result from BRCA1 or BRCA2 gene mutations may be particularly responsive to PARP inhibitors. The BRCA genes provide another source of DNA repair. BRCA gene mutations result in a loss of this DNA repair capability and may make cells particularly vulnerable to the loss of other DNA repair mechanisms such as those provided by PARP.
The current Phase II studies evaluated low and high doses of olaparib in previously treated breast cancer and ovarian cancer patients with BRCA1 or BRCA2 gene mutations. Patients in both studies were treated with either 100 mg or 400 mg of oral olaparib twice a day. The studies was designed to determine overall response rate in 57 ovarian cancer patients and 54 breast cancer patients in order to validate the concept of targeting treatment for the BRCA1 or BRCA2 gene mutation, regardless of disease.
- Overall response rate in the ovarian cancer study was 33% in the high-dose group and 13% in the low-dose group. Patients in the low-dose group were reported to have prognostic factors somewhat worse than the patients in the high-dose group in this study.
- Overall response rate in the breast cancer study was 41% in the high-dose group and 22% in the low-dose group.
- Side effects were tolerable in both groups.
The researchers concluded that olaparib was active in previously treated ovarian and breast cancer patients and that BRCA1 or BRCA2 mutations may play a role as a predictor for responsiveness to olaparib. Further studies are warranted to confirm these data and determine the role of BRCA mutation as a predictive biomarker that may help individualize treatment strategies for optimal results.
 Audeh MW, Carmichael J, Penson RT, et al. Oral poly(ADP-ribose) polymerase inhibitor olaparib in patients with BRCA1 or BRCA2 mutations and recurrent ovarian cancer: a proof-of-concept trial. The Lancet [early online publication]. July 6, 2010.
 Tutt A, Robson M, Garber JE, et al. Oral poly(ADP-ribose) polymerase inhibitor olaparib in patients with BRCA1 or BRCA2 mutations and advanced breast cancer: a proof-of-concept trial. The Lancet [early online publication]. July 6, 2010.