A phase 2 study of the PARP inhibitor veliparib plus temozolomide in patients with heavily pretreated metastatic colorectal cancer.

BACKGROUND: Poly(adenosine diphosphate ribose) polymerase (PARP) inhibitors such as veliparib are potent sensitizing agents and have been safely combined with DNA-damaging agents such as temozolomide. The sensitizing effects of PARP inhibitors are magnified when cells harbor DNA repair defects. METHODS: A single-arm, open-label, phase 2 study was performed to investigate the disease control rate (DCR) after 2 cycles of veliparib plus temozolomide in patients with metastatic colorectal cancer (mCRC) refractory to all standard therapies. Fifty patients received temozolomide (150 mg/m2 /d) on days 1 to 5 and veliparib (40 mg twice daily) on days 1 to 7 of each 28-day cycle. Another 5 patients with mismatch repair-deficient (dMMR) tumors were also enrolled. Twenty additional patients were then treated with temozolomide at 200 mg/m2 /d. Archived tumor specimens were used for immunohistochemistry to assess mismatch repair, phosphatase and tensin homolog deleted on chromosome 10 (PTEN), and O(6)-methylguanine-DNA methyltransferase (MGMT) protein expression levels. RESULTS: The combination was well tolerated, although some patients required dose reductions for myelosuppression. The primary endpoint was successfully met with a DCR of 24% and 2 confirmed partial responses. The median progression-free survival was 1.8 months, and the median overall survival was 6.6 months. PTEN protein expression and MGMT protein expression were not predictors of DCR. There was also a suggestion of worse outcomes for patients with dMMR tumors. CONCLUSIONS: In this heavily pretreated mCRC population, a combination of veliparib and temozolomide was well tolerated with temozolomide doses up to 200 mg/m2 /d, and it was clinically active. PARP inhibitor-based therapy merits further exploration in patients with mCRC. Cancer 2018;124:2337-46. © 2018 American Cancer Society.

Phase II study of temozolomide and veliparib combination therapy for sorafenib-refractory advanced hepatocellular carcinoma.

PURPOSE: To determine the antitumor efficacy and tolerability of combination temozolomide (TMZ) and veliparib (ABT-888) in patients with advanced, sorafenib-refractory hepatocellular carcinoma (HCC). METHODS: This single-arm phase II trial enrolled patients with pathologically confirmed, sorafenib-refractory HCC. All patients received 40 mg ABT-888 PO daily on days 1-7 and 150 mg/m(2) TMZ PO daily on days 1-5 of a 28-day cycle. The primary endpoint was objective response rate (ORR) at 2 months. Secondary endpoints included overall survival (OS), progression-free survival (PFS), and toxicity profile. Tumor response was assessed every 2 cycles using RECIST criteria, and toxicities were assessed using CTCAE v4.03. RESULTS: We enrolled 16 patients in the first phase of the trial, but the study was discontinued due to a poor ORR; only four patients (25 %) had SD after 2 cycles. Twelve patients (75 %) were taken off study after 2 months of treatment; 10 of these had disease progression. Two patients (13 %) were taken off study due to severe toxicity, and one patient (6 %) died from non-treatment-related liver failure. One patient had SD for 16 months, receiving 11 cycles of therapy before being taken off study. The most common grade 3 treatment-related toxicities included vomiting (n = 2), thrombocytopenia (n = 2), nausea (n = 1), and anemia (n = 1). The median PFS was 1.9 months, and median OS was 13.1 months. CONCLUSION: The combination of TMZ and ABT-888 is well tolerated in patients with advanced HCC. However, the regimen failed to show survival benefit. CLINICALTRIALS. GOV IDENTIFIER: NCT01205828.