A phase II study of niraparib in combination with EGFR inhibitor panitumumab in patients with advanced colorectal cancer.

Abstract

TPS269 Background: Panitumumab (Pmab) is a recombinant monoclonal antibody that binds specifically to the human epidermal growth factor receptor (EGFR), and is indicated for metastatic colorectal carcinoma (mCRC). EGFR inhibition induces synthetic lethality with poly ADP ribose polymerase inhibitors (PARPi) by attenuating DNA repair pathways. This susceptibility to PARPi-induced cell death by EGFR inhibition is associated with deficient Non-homologous end joining (NHEJ), and Homologous recombination (HR) mediated DNA repair and persistence of DNA damage. Furthermore, efficacy of PARPi (such as niraparib) is highly correlated with platinum sensitivity. Cancer cell sensitivity and resistance to both PARPi and platinum have been associated with loss and restoration of HR DNA repair, indicating similar mechanisms of anticancer activity and resistance. Platinum sensitivity in CRC could therefore predict for anticancer properties of PARPi when utilized in the setting of synthetic lethality. Combining PARP and EGFR inhibition has the potential to confer synergistic benefit, while ameliorating resistance mechanism to PARPi. This study aims to evaluate the activity of the combination of niraparib and Pmab in RAS wildtype (WT) mCRC. Methods: Eligible patients for the trial include advanced, RAS WT mCRC who have been intolerant of, progressed on, or failed at least one line of systemic chemotherapy. Those currently on first line oxaliplatin-containing regimen are allowed on the trial if they have remained stable or better (PR or CR) for at least 4 months on that line of treatment, and are being considered for maintenance therapy as standard of care. Patients must also be 18 years old, ECOG PS 0-1 and measurable disease per RECIST 1.1. A safety run-in cohort of 6 eligible patients, and additional 20 patients with the same inclusion criteria will be enrolled. Pmab dose - 6 mg/kg IV on days 1 & 15 of each 28-day cycle; Niraparib - 200mg or 300mg (based on body weight and platelet count) orally continuously. Primary endpoint: clinical benefit rate (CR +PR + SD). Biomarker analysis includes skin biopsies evaluated for p-Caspace-3, PARP, p-MAPK, Ki-67, and p27. The study was activated in Sept. 2019. Clinical trial information: NCT03983993.