Onvansertib treatment overcomes olaparib resistance in high-grade ovarian carcinomas

Occurrence of resistance to olaparib, a poly(ADP-ribose) polymerase (PARP) inhibitor (PARPi) approved in ovarian carcinoma, has already been shown in clinical settings. Identifying combination treatments to sensitize tumor cells and/or overcome resistance to olaparib is critical. Polo-like kinase 1 (PLK1), a master regulator of mitosis, is also involved in the DNA damage response promoting homologous recombination (HR)-mediated DNA repair and in the recovery from the G2/M checkpoint. We hypothesized that PLK1 inhibition could sensitize tumor cells to PARP inhibition. Onvansertib, a highly selective PLK1 inhibitor, and olaparib were tested in vitro and in vivo in BRCA1 mutated and wild-type (wt) ovarian cancer models, including patient-derived xenografts (PDXs) resistant to olaparib. The combination of onvansertib and olaparib was additive or synergic in different ovarian cancer cell lines, causing a G2/M block of the cell cycle, DNA damage, and apoptosis, much more pronounced in cells treated with the two drugs as compared to controls and single agents treated cells. The combined treatment was well tolerated in vivo and resulted in tumor growth inhibition and a statistically increased survival in olaparib-resistant-BRCA1 mutated models. The combination was also active, although to a lesser extent, in BRCA1 wt PDXs. Pharmacodynamic analyses showed an increase in mitotic, apoptotic, and DNA damage markers in tumor samples derived from mice treated with the combination versus vehicle. We could demonstrate that in vitro onvansertib inhibited both HR and non-homologous end-joining repair pathways and in vivo induced a decrease in the number of RAD51 foci-positive tumor cells, supporting its ability to induce HR deficiency and favoring the activity of olaparib. Considering that the combination was well tolerated, these data support and foster the clinical evaluation of onvansertib with PARPis in ovarian cancer, particularly in the PARPis-resistant setting.

Olaparib treatment in older patients with ovarian cancer: need for 'real-world' data beyond clinical trials

Background

Ageing is a risk factor for cancer. Worldwide, the number and proportion of adults aged ≥65 will increase, along with the incidence of ovarian cancer. Older adults are under-represented in randomised clinical trials (RCTs), and those who are enrolled have a good performance status and no major health issues. These patients are not representative of older patients seen in everyday clinical practice; therefore, age-specific data on efficacy and toxicity of olaparib in the ‘real-world’ setting are lacking.

Methods

This observational study was conducted in the Central Jutland Region in Denmark. Data in unselected older (≥65) patients with known BRCA mutation receiving olaparib maintenance treatment for platinum-sensitive relapsed ovarian cancer were registered between 2015 and 2019. Toxicity and progression-free survival (PFS) were registered. No geriatric assessment has been performed.

Results

In total, 20 consecutive patients ≥65 years were included with a median age of 75 years (range: 65–85). Most of the patients (18/20) had ECOG PS: 0–1. Treatment interruption and dose reduction occurred in 65% of the patients. Toxicities of any grade occurred in 18 (90%), whereas grade 3/4 toxicities occurred in 6 patients (30%). Treatment was terminated due to disease progression or unacceptable toxicity in 13 (65%) patients. The median PFS was 6 months (range: 2–31), and the median follow-up was 15 months (range: 3–30).

Discussion

Our ‘real-world’ experience shows that unselected older patients represent a significant larger proportion in real life than in RCTs; furthermore, older patients in a real-world setting may experience more side effects possibly affecting the quality of life. The median PFS data suggest that older patients may not derive the same clinical benefit than their fit and younger counterparts.

There is a need to enrol vulnerable/frail older patients into RCTs, ensuring that data will also be applicable in standard clinical settings. Incorporating geriatric assessment into these trials should be encouraged.