In vivo anti-tumor activity of the PARP inhibitor niraparib in homologous recombination deficient and proficient ovarian carcinoma.

OBJECTIVE: Poly(ADP-ribose) polymerase (PARP) inhibitors have yielded encouraging responses in high-grade serous ovarian carcinomas (HGSOCs), but the optimal treatment setting remains unknown. We assessed the effect of niraparib on HGSOC patient-derived xenograft (PDX) models as well as the relationship between certain markers of homologous recombination (HR) status, including BRCA1/2 mutations and formation of RAD51 foci after DNA damage, and response of these PDXs to niraparib in vivo. METHODS: Massively parallel sequencing was performed on HGSOCs to identify mutations contributing to HR deficiency. HR pathway integrity was assessed using fluorescence microscopy-based RAD51 focus formation assays. Effects of niraparib (MK-4827) on treatment-naïve PDX tumor growth as monotherapy, in combination with carboplatin/paclitaxel, and as maintenance therapy were assessed by transabdominal ultrasound. Niraparib responses were correlated with changes in levels of poly(ADP-ribose), PARP1, and repair proteins by western blotting. RESULTS: Five PDX models were evaluated in vivo. Tumor regressions were induced by single-agent niraparib in one of two PDX models with deleterious BRCA2 mutations and in a PDX with RAD51C promoter methylation. Diminished formation of RAD51 foci failed to predict response, but Artemis loss was associated with resistance. Niraparib generally failed to enhance responses to carboplatin/paclitaxel chemotherapy, but maintenance niraparib therapy delayed progression in a BRCA2-deficient PDX. CONCLUSIONS: Mutations in HR genes are neither necessary nor sufficient to predict response to niraparib. Assessment of repair status through multiple complementary assays is needed to guide PARP inhibitor therapy, design future clinical trials and identify ovarian cancer patients most likely to benefit from PARP inhibition.

Improving eligibility criteria for first-line trials for patients with DLBCL using a US-based Delphi-method survey.

Recent first-line randomized controlled trials (RCTs) for patients with diffuse large B-cell lymphoma (DLBCL) have shown negative results, which may be due in part to onerous eligibility criteria limiting enrollment of poor-risk patients who require immediate treatment. We conducted a Delphi-method survey with lymphoma experts in the United States to define recommendations for essential and potentially unnecessary enrollment criteria for modern first-line DLBCL RCTs aimed at increasing clinical diversity of ensuing study groups. We first tabulated enrollment criteria from 19 DLBCL RCTs spanning the rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) era to identify common eligibility criteria from prior DLBCL RCTs for inclusion in the Delphi-method survey. We tabulated 451 total eligibility criteria comprising 51 criterion categories across 19 first-line DLBCL RCTs in the R-CHOP era. We then surveyed lymphoma clinical trial experts representing 8 academic medical centers in the United States regarding essential and unnecessary eligibility criteria for modern DLBCL RCTs. Seventeen of 29 invited clinical investigators completed the round-1 questionnaire (response rate, of 58.6%), 15 of 17 round-1 participants (88.2%) completed the round-2 survey, and all round-1 participants reviewed finalized recommendations for eligibility criteria for modern first-line DLBCL RCTs. We defined consensus recommendations for 31 modernized eligibility criteria including threshold values for 10 quantitative eligibility criteria aimed at facilitating enrollment of a clinically diverse study population in first-line DLBCL RCTs designed to improve standard-of-care therapy.