Abstract LB-139: Phase I trial of veliparib or mitomycin (MMC) + veliparib in patients with sporadic solid tumors screened for somatic deficiency in the Fanconi Anemia (FA) pathway.
Authors: Miguel A. Villalona-Calero, Wenrui Duan, Weiqiang Zhao, Konstantin Shilo, Jiuping Ji, Jennifer Thurmond, Adam Norris, Jeffrey Rose, Rachel Layman, John Marshall, Tanios Bekaii-Saab, Alice Chen
Journal: Cancer Research (2013)

Abstract BRCA 1/2 dysfunction sensitizes cells to inhibition of PARP enzymatic activity, due to the persistence of DNA breaks normally repaired by homologous recombination (HR), thus cancer pts carriers of germ line BRCA deleterious mutations have been targeted for treatment with PARP inhibitors. An example of HR repair is the FA pathway where BRCA 1/2 collaborate with several other genes resulting in FancI and FancD2 activation and nucleus repair foci formation. We have developed a triple stain immunofluorescence based method to evaluate FA pathway functionality (foci formation) (FancD2/DAPI/Ki67) (FATSI) in paraffin embedded tumor tissues, and hypothesized that among patients with sporadic tumors, a significant proportion with tumoral dysfunctional FA pathway can be identified. A two steps clinical trial (NCT01017640) was designed to 1- screen solid tumor patients for absence of FA tumor foci formation, and 2- evaluate safety and recommended doses in these pts of the PARPi veliparib, either alone or in combination with chemotherapy (MMC). 607 pts were consented, 532 had their tumor tissue screened, 142 (27%) had absent foci. All major solid tumors were represented in FA dysfunction, notably 36 of 105 (34%) colorectal and 40 of 135 (30%) breast cancers. 52 pts received 192 cycles of veliparib, 29 pts as monotherapy in escalating dose cohorts (starting at 50 mg PO BID continuously), and 23 following MMC 10 mg-sqm every 4 weeks (40mg-sqm cumulative cap) at 50 mg BID at increased duration cohorts (1, 2 and 3 wks) every 4 wks (100 and 200 mg BID for 3 wks in subsequent cohorts). Recommended dose levels are: veliparib 300 mg BID as monotherapy (2DLT/3 pts at 400 BID:G3 fatigue) and MMC/veliparib 10mg-sqm/200 mg BID three weeks duration. Analysis for germ line mutations (BRCA1 and 2 sequencing and for the 5 most common BRCA1 large rearrangements) in PBMC among 50 pts showed 7 pts (3 breast, 1 ampullary, 2 ovarian) with BRCA abnormalities: 6 known deleterious mutations and 1 polymorphism. Five RECIST criteria responses occurred (1CR, 4 PR) (1 lung, 2 breast, 1 ovarian, 1 endometrial), all in the combination arm. Two breast cancer pts (39 and 13 cycles) and 1 ovarian (6 cycles) on monotherapy, plus 1 breast (15 cycles), 1 colon (7 cycles) on the combination, had prolonged stability. rH2AX (n=49) and PAR (n=17) analysis in PBMC suggests veliparib dose dependency (blunting of rH2AX induction, lower PAR level and slower recovery for higher doses). The trial was amended to enroll an expanded cohort of 10 FATSI negative colorectal patients who will undergo fresh biopsy for whole exome sequencing (RNAseq) and FA/DNA repair gene panel analysis prior to treatment at the recommended dose in the combination arm, with the goal of identifying the specific genetic defect mediating the FA dysfunction, as well as partner mutations to be targeted in subsequent trials. Supported by R01CA152101 &amp; N01CM62207 Citation Format: Miguel A. Villalona-Calero, Wenrui Duan, Weiqiang Zhao, Konstantin Shilo, Jiuping Ji, Jennifer Thurmond, Adam Norris, Jeffrey Rose, Rachel Layman, John Marshall, Tanios Bekaii-Saab, Alice Chen. Phase I trial of veliparib or mitomycin (MMC) + veliparib in patients with sporadic solid tumors screened for somatic deficiency in the Fanconi Anemia (FA) pathway. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-139. doi:10.1158/1538-7445.AM2013-LB-139