FOLFIRI3-aflibercept as second- or later-line therapy in patients with metastatic colorectal cancer

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Background: The efficacy of the standard FOLFIRI-aflibercept second-line therapy may be improved by the chemotherapy regimen in metastatic colorectal cancer (MCRC). FOLFIRI was optimized by splitting the dose of irinotecan on day 1 and day 3 and by removing the bolus of 5-FU in the FOLFIRI3 regimen. Methods: This is a retrospective multicentric cohort, evaluating efficacy and safety of the association of aflibercept with FOLFIRI3, in patients (pts) with previously treated MCRC. The primary endpoint was overall response rate (ORR). Secondary endpoints were disease control rate (DCR), progression-free survival (PFS), overall survival (OS), and safety. Results: From September 2014 to December 2016, 74 pts were treated in four French centers. Nine pts were excluded due to prior use of aflibercept (n = 3), more than one prior line of treatment in irinotecan-naïve pts (n = 3) and inadequate liver function (n = 3). In the cohort of irinotecan-naïve pts (n = 30), ORR and DCR were 43.3% and 76.7%. Median PFS and OS were 11.3 months (95% CI 6.1-29.0) and 17.0 months (95% CI 13.0-17.3). The most common ( > 5%) grade 3-4 adverse events were diarrhea (37.9%), neutropenia (14.3%), stomatitis and anemia (10.4%), hypertension (6.7%). In the cohort of pts previously treated with irinotecan (n = 35), 20 (57.1%) pts received ≥2 prior lines of treatment with various prior irinotecan regimen (FOLFIRINOX, n = 21; FOLFIRI, n = 10; FOLFIRI3, n = 4). ORR and DCR were 34.3% and 60.0%. Median PFS and OS were 5.7 months (95% CI 3.9-10.4) and 14.3 months (95% CI 12.8-19.5). In 4 patients refractory to irinotecan, FOLFIRI3-aflibercept led to one partial response, 2 stabilizations, and one patient not evaluable. Conclusions: A minimal modification of the FOLFIRI regimen led to a dramatically improvement of efficacy with FOLFIRI3-aflibercept, whatever prior use of irinotecan. Further randomized trial is planned.

CRM1 Inhibition Promotes Cytotoxicity in Ewing Sarcoma Cells by Repressing EWS-FLI1-Dependent IGF-1 Signaling

Ewing sarcoma (EWS) is an aggressive bone malignancy that mainly affects children and young adults. The mechanisms by which EWS (EWSR1) fusion genes drive the disease are not fully understood. CRM1 (XPO1) traffics proteins from the nucleus, including tumor suppressors and growth factors, and is overexpressed in many cancers. A small-molecule inhibitor of CRM1, KPT-330, has shown therapeutic promise, but has yet to be investigated in the context of EWS. In this study, we demonstrate that CRM1 is also highly expressed in EWS. shRNA-mediated or pharmacologic inhibition of CRM1 in EWS cells dramatically decreased cell growth while inducing apoptosis, cell-cycle arrest, and protein expression alterations to several cancer-related factors. Interestingly, silencing of CRM1 markedly reduced EWS-FLI1 fusion protein expression at the posttranscriptional level and upregulated the expression of the well-established EWS-FLI1 target gene, insulin-like growth factor binding protein 3 (IGFBP3), which inhibits IGF-1. Accordingly, KPT-330 treatment attenuated IGF-1-induced activation of the IGF-1R/AKT pathway. Furthermore, knockdown of IGFBP3 increased cell growth and rescued the inhibitory effects on IGF-1 signaling triggered by CRM1 inhibition. Finally, treatment of EWS cells with a combination of KPT-330 and the IGF-1R inhibitor, linsitinib, synergistically decreased cell proliferation both in vitro and in vivo Taken together, these findings provide a strong rationale for investigating the efficacy of combinatorial inhibition of CRM1 and IGF-1R for the treatment of EWS. Cancer Res; 76(9); 2687-97. ©2016 AACR.

Abstract LB-255: Selinexor, a selective inhibitor of nuclear export (SINE) compound, shows enhanced antitumor activity in combination with the PARP inhibitor, olaparib, in models of triple-negative breast cancer

Background: Selinexor is a SINE (Selective Inhibitor of Nuclear Export) compound currently in Phase I and II clinical trails for the treatment of hematological and solid malignancies. Selinexor blocks the key nuclear export protein XPO1 to force nuclear retention of tumor suppressor proteins (TSPs), including p53, BRCA1/2, pRB and FOXO3A. Olaparib is an FDA approved therapy for BRCA1/2 mutated ovarian cancer, which inhibits Poly-ADP-Ribose Polymerase (PARP) and prevents DNA damage repair. Furthermore, olaparib is being evaluated for the treatment of Triple Negative Breast Cancer (TNBC). We hypothesized that selinexor would restore genomic surveillance through nuclear accumulation of wild type BRCA1 and therefore combination treatment with olaparib would prevent DNA damage repair to amplify cancer cell death.

Methods: The effects of selinexor alone or in combination with olaparib were tested on a panel of 7 TNBC cell lines using MTT and soft-agar colony formation assays in parallel with FACS analysis. In vivo efficacy of single-agent or combination therapy was evaluated using an MDA-MB-468 (BRCA1 wild type, TNBC) xenograft model. Combination index (CI) values were determined using the CompuSyn software and treatment was considered synergistic when CI<1.

Results: The median IC50 values for selinexor and olaparib were 1.88 μM (range: 0.27 μM to >10 μM) and 92.6 μM (range: 17.5 μM to >300 μM), respectively. Combination treatment led to synergistic inhibition of proliferation in the 7 TNBC cell lines evaluated. The median CI tested on the panel of cell lines was 0.68 (ranging from 0.4 to 0.96). FACS analysis revealed an additive effect of the selinexor and olaparib combination on S-phase inhibition and G2 arrest in BRCA1 mutated and wild type cells. Furthermore, AnnexinV/PI staining showed an additive effect on TNBC cell apoptosis regardless of BRCA1 mutational status. In the MDA-MB-468 xenograft model, 75% tumor growth inhibition (TGI) was observed in the combination group by day 22 compared to 55% and 35% TGI for single-agent selinexor and olaparib, respectively.

Conclusion: Selinexor and olaparib in combination act synergistically to induce apoptosis in TNBC cells and amplify anti-tumor effects in a TNBC xenograft model. These data provide a rationale supporting the study of selinexor/olaparib combination in clinical trials.

Citation Format: Helene Marijon, Sigal Gery, Sivan Elloul, Sharon Y. Friedlander, TJ Unger, Robert Carlson, Sharon Shacham, Michael Kauffman, Harold P. Koeffler. Selinexor, a selective inhibitor of nuclear export (SINE) compound, shows enhanced antitumor activity in combination with the PARP inhibitor, olaparib, in models of triple-negative breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-255. doi:10.1158/1538-7445.AM2015-LB-255

Abstract 5542: Synergistic inhibition of growth of triple-negative breast cancer cells by co-targeting PARP and HDAC

Triple-negative breast cancers (TNBC) have a poor prognosis after it has spread beyond the breast. Existing therapies remain inadequate. Despite similarities with BRCA-mutated breast cancers (such as high sensitivity to cisplatin reflecting defects in DNA repair pathways), Poly ADP Ribose Polymerase (PARP) inhibitors failed to improve prognosis of non-BRCA-mutated TNBC. Histone DeACetylase (HDAC) inhibitors are targeted therapies that can modulate expression of genes by affecting chromatin conformation, including down-regulation of genes encoding proteins involved in Homologous Recombination (HR). A previous study noted that the HDAC inhibitor, vorinostat, can induce DNA damage which normal but not cancer cells can repair. Thus, our goal was to determine if HDAC inhibitors could sensitize TNBC cells to PARP inhibitors.

We studied the effect of olaparib in combination with vorinostat in 8 TNBC cell lines. Median IC50 for olaparib and for vorinostat were 146µM and 6.4µM, respectively. Remarkedly, the combination of 2µM of vorinostat decreased the median IC50 for olaparib by 3.47-fold (from 146µM to 45µM, p=.033). Further studies showed the drug combination was synergistic for seven of eight cell lines with an average Combination Index (CI) of 0.62 (± 0.20), using CompuSyn software. Synergism was also observed with belinostat (another HDAC inhibitor) when combined with olaparib. Furthermore, co-treatment with vorinostat and olaparib drastically inhibited clonogenic growth of TNBC cells in soft-agar. Also, olaparib (10µM) and vorinostat (2µM) markedly increased G2 arrest (46%±0.8 after 48 hours, p=.033) and significantly increased the percentage of apoptotic cells (17%±1.91 cells positive as measured by Annexin V - Propidium Iodine staining after 48 hours, p=.022), compared to either drug alone using MDA-MB-157 TNBC cells. Similar trends were observed in two other TNBC lines (MDA-MB-231 and HCC1937). Regarding mechanisms involved in this observed synergism of the two drugs: #1 expression of several proteins involved in HR (RAD51, Chk2 and BRCA1) were decreased; #2 P-H2AX expression markedly increased with combination treatment suggesting the two drugs caused greater DNA breaks. As a result, the P-H2AX/RAD51 ratio increased when the two drugs were used together (occurring in both BRCA1-wt and -mutant TNBC lines).

Our results provide evidence that treatment with a HDAC inhibitor can sensitize TNBC cell lines to olaparib in BRCA-mutated as well as in BRCA-wt cells, irrespectively of their initial sensitivities to olaparib alone. Both drugs are at an advanced-stage in clinical development and are well tolerated in humans, offering the opportunity to test the association in a clinical trial.

Citation Format: Helene Marijon, Haibo Sun, Aimery de Gramont, Sigal Gery, H Phillip Koeffler. Synergistic inhibition of growth of triple-negative breast cancer cells by co-targeting PARP and HDAC. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5542. doi:10.1158/1538-7445.AM2014-5542