The novel ATM inhibitor (AZ31) enhances antitumor activity in patient derived xenografts that are resistant to irinotecan monotherapy

Irinotecan, a standard of care therapy for CRC, elicits cytotoxic effects by generating double strand breaks resulting in DNA damage. The activation of the ATM pathway plays a fundamental role in regulating the cellular response and repair to DNA damage. The objective of this preclinical study was to determine whether ATM inhibition would enhance sensitivity to irinotecan treatment. Treatment effects of AZ31, irinotecan or AZ31 + irinotecan were investigated in CRC cell lines and CRC patient derived xenografts. Activation of ATM and downstream targets p-RAD50 and p-H2AX were evaluated by immunohistochemistry. Combinational effects were demonstrated in 4 out of 8 CRC explants. Interestingly, each of the combinational sensitive CRC PDX models were shown to be more resistant to irinotecan single agent therapy. Treatment with irinotecan significantly elevated the ATM pathway evident by an increase in the activation of H2AX and RAD50. Combinational therapy reduced the activation of H2AX and RAD50 when compared to irinotecan alone in the combination sensitive CRC098. AZ31 + irinotecan was effective at reducing tumor growth in tumors that exhibited resistance to irinotecan in our CRC PDX model. These findings support further investigation of this combinational therapy for the treatment of CRC patients.

A phase Ib study of selumetinib (AZD6244, ARRY-142886) in combination with sorafenib in advanced hepatocellular carcinoma (HCC)

BACKGROUND

Treatment with sorafenib, although associated with inhibition of tumour growth and angiogenesis in in vivo studies, leads to up-regulation of pERK. The addition of MEK inhibition could potentially abrogate this effect and potentiate anti-tumour activity. This phase I study investigated the maximum tolerated dose (MTD), safety, tolerability, pharmacokinetics (PK) and biomarker correlates of selumetinib combined with sorafenib in patients with advanced hepatocellular carcinoma (HCC).

METHODS

Patients with Child-Pugh (CP) score ≤7 were treated with 400 mg twice daily of sorafenib with escalating doses of selumetinib in a 3 + 3 study design. The dose-limiting toxicity (DLT) evaluation period was 28 days. PK of selumetinib was determined. Angiogenic effect was evaluated with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI).

RESULTS

Twenty-seven patients of Asian ethnicity were enrolled. The MTD was selumetinib 75 mg daily with sorafenib 400 mg twice daily. DLT included grade 3 transaminitis, diarrhoea and fatigue. Most common treatment-related adverse events at MTD (all grades) were diarrhoea (85%), rash (59%), hypertension (44%), fatigue (30%), anorexia (22%) and hand-foot syndrome (22%). Four patients (15%) had PR and 13 (48%) had SD. PR or SD was observed for ≥6 months in seven patients. The median overall survival was 14.4 months. Selumetinib exposures in combination with sorafenib were comparable to other monotherapy studies. A reduction in permeability-surface area product noted in DCE-MRI with treatment correlated with worse survival outcomes.

CONCLUSION

The MTD of selumetinib was 75 mg daily when combined with sorafenib 400 mg twice a day in CP ≤7 HCC. Acceptable adverse events and encouraging anti-tumour activity warrant further evaluation. DCE-MRI findings deserve prospective evaluation.

CLINICALTRIALSGOV IDENTIFIER

NCT01029418.

A NOTCH1 gene copy number gain is a prognostic indicator of worse survival and a predictive biomarker to a Notch1 targeting antibody in colorectal cancer

Dysregulation of the Notch1 receptor has been shown to facilitate the development and progression of colorectal cancer (CRC) and has been identified as an independent predictor of disease progression and worse survival. Although mutations in the NOTCH1 receptor have not been described in CRC, we have previously discovered a NOTCH1 gene copy number gain in a portion of CRC tumor samples. Here, we demonstrated that a NOTCH1 gene copy number gain is significantly associated with worse survival and a high percentage of gene duplication in a cohort of patients with advanced CRC. In our CRC patient-derived tumor xenograft (PDTX) model, tumors harboring a NOTCH1 gain exhibited significant elevation of the Notch1 receptor, JAG1 ligand and cleaved Notch1 activity. In addition, a significant association was identified between a gain in NOTCH1 gene copy number and sensitivity to a Notch1-targeting antibody. These findings suggest that patients with metastatic CRC that harbor a gain in NOTCH1 gene copy number have worse survival and that targeting this patient population with a Notch1 antibody may yield improved outcomes.

Potent antitumor activity of cabozantinib, a c-MET and VEGFR2 inhibitor, in a colorectal cancer patient-derived tumor explant model

Antiangiogenic therapy is commonly used for the treatment of colorectal cancer (CRC). Although patients derive some clinical benefit, treatment resistance inevitably occurs. The MET signaling pathway has been proposed to be a major contributor of resistance to antiangiogenic therapy. MET is upregulated in response to vascular endothelial growth factor pathway inhibition and plays an essential role in tumorigenesis and progression of tumors. In this study, we set out to determine the efficacy of cabozantinib in a preclinical CRC patient-derived tumor xenograft model. We demonstrate potent inhibitory effects on tumor growth in 80% of tumors treated. The greatest antitumor effects were observed in tumors that possess a mutation in the PIK3CA gene. The underlying antitumor mechanisms of cabozantinib consisted of inhibition of angiogenesis and Akt activation and significantly decreased expression of genes involved in the PI3K pathway. These findings support further evaluation of cabozantinib in patients with CRC. PIK3CA mutation as a predictive biomarker of sensitivity is intriguing and warrants further elucidation. A clinical trial of cabozantinib in refractory metastatic CRC is being activated.

Abstract B30: KRAS wild type tumors exhibit increased efficacy to the combination of AZ1 (a tankyrase inhibitor) + irinotecan in a patient-derived CRC explant model

Background: Dysregulation of the canonical Wnt signaling pathway has been implicated in colorectal cancer (CRC) development as well as incipient stages of malignant transformation. An important regulator of the Wnt pathway are tankyrases that function in reducing Axin2 levels which is an essential protein in the β-catenin destruction complex. Targeting this pathway with a potent tankyrase inhibitor presents a plausible approach in drug development. In this study, we evaluated the antitumor effects AZ1 (a novel tankyrase 1/2 inhibitor which also carries PARP1 activity) as a single agent and in combination with irinotecan in our patient derived CRC explant xenograft models.

Methods: Twenty patient derived CRC explant xenografts were treated with vehicle, AZ1 (50mg/kg/day), irinotecan (30mg/kg/week) or AZ1 (50mg/kg/day) + irinotecan (30mg/kg/week) for 28 days. Pharmacokinetic effect of AZ1 was determined in plasma and tumor over 24h. Both pharmacodynamic effects (Axin2 levels) and changes in biomarkers relevant to the Wnt pathway were determined by Western blotting. Intra-nuclear β-catenin levels were evaluated by immunohistochemistry. A tumor growth index (TGI) was calculated as the ratio in tumour volumes in the treated animals and the control animals (T/C) on the last day of drug treatment to determine efficacy. TGI≤ 50% was considered sensitive and TGI > 50% was resistant.

Results: Three out of 20 CRC explants showed some tumour growth inhibition with AZ1. In animals bearing CRC40 xenografts, AZ1 showed a Tmax of 1 hour in plasma and 30 minutes in tumor. In addition, Axin2 stabilization post AZ1 started 15 minutes after drug administration, with the maximum stabilization observed at 8 hours. Treatment with AZ1 + irinotecan resulted in a greater anti-tumor effect (achieving stasis or better) than either agent alone in 4 out of 20 CRC xenografts. A significant association (fisher exact test: p= 0.007) was identified between combinational sensitivity and KRAS wild type. Evaluation of tumors after treatment showed marked stabilization of Tankyrase 1/2 and Axin2; however, active β-catenin levels were not changed. Also, there were no changes to intra-nuclear β-catenin (IHC) levels after treatment. Interestingly, NuMa, a protein involved in maintenance of the mitotic spindle and a target of Tankyrase 1/2 increased following irinotecan in 3 models, 2 showing a combination effect and 1 which did not. Numa levels decreased with the combination of AZ1 and irinotecan compared to irinotecan alone in 2 models showing a significant combination effect.

Conclusion: Combination AZ1 and irinotecan achieved greater anti-tumor effect compared to monotherapy in 4 out of 20 CRC xenografts. Activity was limited to CRC xenografts with KRAS WT status. Further studies are warranted to validate these findings in KRAS WT patients and to understanding the specific mechanisms in tumors that responded to combinational therapy.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B30.

Citation Format: WM Tai, Kevin Quackenbush, Alicia Purkey, Stacey Bagby, Wells Messersmith, Eun Kee Song, Todd Pitts, John J. Arcaroli. KRAS wild type tumors exhibit increased efficacy to the combination of AZ1 (a tankyrase inhibitor) + irinotecan in a patient-derived CRC explant model. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B30.

Comparing the efficacy of sunitinib with sorafenib in xenograft models of human hepatocellular carcinoma: mechanistic explanation

Hepatocellular carcinoma (HCC) is the fifth most common and third deadliest malignancy. Sorafenib has demonstrated 44% survival advantage over placebo and has emerged as a standard of care in advanced HCC. The therapeutic effects of sorafenib are however transient and hence additional treatment options are warranted. In this study, we aimed to compare the efficacy of sunitinib relative to sorafenib, two potent inhibitors of protein tyrosine kinases involved in tumor growth, metastasis, or angiogenesis. We reported that sorafenib and sunitinib suppressed tumor growth, angiogenesis, cell proliferation, and induced apoptosis in both orthotopic and ectopic models of HCC. However, the antitumor effect of 50 mg/kg sorafenib was greater than that of 40 mg/kg sunitinib. Sorafenib inhibited p-eIF4E Ser209, p-p38 Thr180/Tyr182 and reduced survivin expression. This was not seen with sunitinib. In addition, the antitumor and apoptotic effects of sorafenib, which are associated with upregulation of fast migrating Bim and ASK1 and downregulation of survivin, were greater than that of sunitinib. These observations explained in part the apparent superior anti-tumor activity of sorafenib compared to sunitinib. In conclusion, sunitinib demonstrated an inferior anti-tumor activity compared to sorafenib in ectopic and orthotopic models of human HCC. It remains to be seen whether such observations would be recapitulated in humans.

A phase II study evaluating the safety and efficacy of an adenovirus-ΔLMP1-LMP2 transduced dendritic cell vaccine in patients with advanced metastatic nasopharyngeal carcinoma

BACKGROUND

Individuals with metastatic Epstein-Barr virus (EBV)-positive nasopharyngeal carcinoma (NPC) continue to have poor outcomes. To evaluate the ability of a dendritic cell (DC) vaccine to target subdominant EBV antigens LMP1 and LMP2 expressed by NPC cells, we vaccinated patients using autologous DCs transduced with an adenovirus encoding a truncated LMP1 (ΔLMP1) and full-length LMP2 (Ad-ΔLMP1-LMP2).

MATERIALS AND METHODS

Sixteen subjects with metastatic NPC received Ad-ΔLMP1-LMP2 DC vaccines i.d. biweekly for up to five doses. Toxicity, immune responses and clinical responses were determined.

RESULTS

Most patients had extensive disease, with a median of three visceral sites of involvement (range 1-7). No significant toxicity was observed. Ad-ΔLMP1-LMP2 DCs induced delayed type hypersensitivity responses in 9 out of 12 patients, but although these DCs activated LMP1/2-specific T cells in vitro, no such increase in the frequency of peripheral LMP1/2-specific T cells was detected. Three patients had clinical responses including one with partial response (for 7½ months) and two with stable disease (for 6½ and 7½ months).

CONCLUSIONS

Ad-ΔLMP1-LMP2 transduced DCs can be successfully generated and safely administered to patients with advanced NPC. Since efficacy was limited, future studies should focus on DC vaccines with greater potency administered to subjects with less tumor burden.

Do We Have the Right Prognostic Index for Diffuse Large B Cell Lymphoma (DLBCL) in the Era of Rituximab?

Introduction:

Whilst the addition of rituximab, a humanized monoclonal antibody to standard CHOP chemotherapy (R-CHOP) has improved the outcomes of DLBCL, the validity of the previously identified prognostic index based on clinical parameters is questioned. It is conceivable that prognostic model may alter with introduction of new therapeutics with differing efficacy and mechanisms of action.

Methods:

We conducted a retrospective analysis comparing the relevance of International Prognostic Index (IPI), Age-adjusted IPI and Revised International Prognostic Index (R-IPI) in 320 consecutive patients with DLBCL from 2003–2008 treated with R-CHOP chemotherapy with curative intent. We evaluated the prognostic factors determinant of survival in our group of patients.

Results:

Patients were followed up for a median of 2.70 years. IPI was only able to stratify patients into 3 main risk groups instead of 4. In addition, among patients <60, aa-IPI no longer seem a robust prognostic model. We showed that R-IPI was able to separate patients into 3 different prognostic groups and perhaps most relevant in the era of chemo-immunotherapy. Significant prognostic factors identified in multivariate analysis were performance status (P=0.004) and bone marrow involvement (P=0.026).

Conclusion:

The most robust prognostic index for patients with DLBCL in the era of rituximab remains uncertain. Incorporation of molecular markers into clinical parameters should be evaluated, a study we are embarking on.

Central nervous system (CNS) relapse in diffuse large B cell lymphoma (DLBCL): pre- and post-rituximab

Central nervous system (CNS)-directed prophylactic intrathecal (IT) therapy is indicated in patients with Burkitt and acute lymphoblastic lymphoma. Its role in diffuse large B cell lymphoma (DLBCL), a heterogeneous subtype, is less well defined. While addition of rituximab to standard cyclophosphamide-hydroxydaunorubicin-oncovin-prednisone (CHOP) chemotherapy (R-CHOP) has improved the outcomes of DLBCL patients, its role in reducing CNS relapse is unclear. We aim to (1) evaluate the clinical risk factors predictive of CNS relapse, (2) the role of rituximab in influencing CNS relapse, and (3) role of intrathecal prophylaxis. Four hundred ninety-nine patients with DLBCL from 2000 to 2008 were included (CHOP 179 vs. R-CHOP 320). IT prophylaxis was administered to 82 patients based on our institution's guidelines. Baseline characteristics between CHOP- and R-CHOP-treated patients were similar. Although R-CHOP significantly increased the complete remission rate from 71% to 81% (P < 0.01), CNS relapse rates remained unchanged (R-CHOP 6% vs. CHOP 5.1%). On multivariate analysis, poor performance status (Eastern Cooperative Oncology Group >1; hazard ratio (HR) = 2.01, 95% confidence interval (CI) 1.29-3.14), failure to attain remission (non-complete response (CR) vs. CR: HR = 2.39, 95% CI = 1.03 to 5.51), testicular (HR = 6.67, 95% CI = 1.62 to 27.53), kidney (HR = 20.14, 95% CI = 5.23 to 77.46), and breast involvement (HR = 6.14, 95% CI = 1.61 to 23.37) were each independently predictive of CNS relapse. Use of IT prophylaxis did not appear to decrease CNS relapse. Median survival after CNS relapse was 3.2 months. CNS relapse, a fatal event, remains a challenge in R-CHOP-treated patients. IT prophylaxis may not be sufficient to reduce CNS relapse, and strategies including systemic agents with high CNS penetration should be evaluated in high-risk patients identified in this study.

Central nervous system (CNS) relapse in diffuse large B cell lymphoma (DLBCL): pre- and post-rituximab

Central nervous system (CNS)-directed prophylactic intrathecal (IT) therapy is indicated in patients with Burkitt and acute lymphoblastic lymphoma. Its role in diffuse large B cell lymphoma (DLBCL), a heterogeneous subtype, is less well defined. While addition of rituximab to standard cyclophosphamide-hydroxydaunorubicin-oncovin-prednisone (CHOP) chemotherapy (R-CHOP) has improved the outcomes of DLBCL patients, its role in reducing CNS relapse is unclear. We aim to (1) evaluate the clinical risk factors predictive of CNS relapse, (2) the role of rituximab in influencing CNS relapse, and (3) role of intrathecal prophylaxis. Four hundred ninety-nine patients with DLBCL from 2000 to 2008 were included (CHOP 179 vs. R-CHOP 320). IT prophylaxis was administered to 82 patients based on our institution's guidelines. Baseline characteristics between CHOP- and R-CHOP-treated patients were similar. Although R-CHOP significantly increased the complete remission rate from 71% to 81% (P < 0.01), CNS relapse rates remained unchanged (R-CHOP 6% vs. CHOP 5.1%). On multivariate analysis, poor performance status (Eastern Cooperative Oncology Group >1; hazard ratio (HR) = 2.01, 95% confidence interval (CI) 1.29-3.14), failure to attain remission (non-complete response (CR) vs. CR: HR = 2.39, 95% CI = 1.03 to 5.51), testicular (HR = 6.67, 95% CI = 1.62 to 27.53), kidney (HR = 20.14, 95% CI = 5.23 to 77.46), and breast involvement (HR = 6.14, 95% CI = 1.61 to 23.37) were each independently predictive of CNS relapse. Use of IT prophylaxis did not appear to decrease CNS relapse. Median survival after CNS relapse was 3.2 months. CNS relapse, a fatal event, remains a challenge in R-CHOP-treated patients. IT prophylaxis may not be sufficient to reduce CNS relapse, and strategies including systemic agents with high CNS penetration should be evaluated in high-risk patients identified in this study.

Graft-vs-tumor effect in patients with advanced nasopharyngeal cancer treated with nonmyeloablative allogeneic PBSC transplantation

While nonmyeloablative peripheral blood stem cell transplantation (NST) has shown efficacy against several solid tumors, it is untested in nasopharyngeal cancer (NPC). In a phase II clinical trial, 21 patients with pretreated metastatic NPC underwent NST with sibling PBSC allografts, using CY conditioning, thymic irradiation and in vivo T-cell depletion with thymoglobulin. Stable lymphohematopoietic chimerism was achieved in most patients and prophylactic CYA was tapered at a median of day +30. Seven patients (33%) showed partial response and three (14%) achieved stable disease. Four patients were alive at 2 years and three showed prolonged disease control of 344, 525 and 550 days. With a median follow-up of 209 (4-1147) days, the median PFS was 100 days (95% confidence interval (CI), 66-128 days), and median OS was 209 days (95% CI, 128-236 days). Patients with chronic GVHD had better survival-median OS 426 days (95% CI, 194-NE days) vs 143 days (95% CI, 114-226 days) (P=0.010). Thus, NST may induce meaningful clinical responses in patients with advanced NPC.