Abstract P4-22-15: Sacituzumab govitecan (IMMU-132), an anti-Trop-2-SN-38 antibody-drug conjugate (ADC) for the treatment of relapsed/refractory, metastatic triple-negative breast cancer (mTNBC): Updated results

Background. mTNBC has an aggressive course with limited effective therapy options and a median progression-free survival (PFS) of 2-4 months (mos) with standard therapy. Sacituzumab govitecan (IMMU-132) is an ADC targeting Trop-2, an antigen present in many epithelial cancers, including TNBC, and delivering SN-38, a topoisomerase I inhibitor as its therapeutic moiety. IMMU-132 was awarded Breakthrough Therapy designation by FDA based on its previously reported activity in relapsed/refractory mTNBC patients. Here we present updated results from the mTNBC cohort of an ongoing phase I/II study (ClinicalTrials.gov, NCT01631552).

Methods. mTNBC patients (pts) received IMMU-132 10 mg/kg on days 1 and 8 every 21 days. Trop-2 expression was not required for enrollment, but available tumor specimens underwent immunohistological (IHC) testing. Efficacy was assessed locally by RECIST 1.1; ORR, PFS and overall survival (OS) were determined for all pts. Pharmacokinetic parameters were estimated in select pts with adequate blood sampling. Immunogenicity to IMMU-132 was examined in all pts.

Results. We previously reported preliminary efficacy results in 51 mTNBC patients. Here we present data on 69 patients with data cutoff June 5, 2016. Median age was 56 years (31-81) and a median of 5 prior therapies (range 1-12), with 66 evaluable for response; ORR was 29% (19/66) 2 confirmed complete (CR) and 17 confirmed partial responses (PR). The median intention-to-treat PFS is 5.6 mos (95% CI, 3.6-7.1 mos) and median OS is 14.3 mos (95% CI, 10.5-18.8 mos). PRs included 2 pts whose tumors did not respond to anti-PD-L1 therapy. The duration of response in the 19 confirmed responders (8 continuing therapy) is 11.5 mos (95% CI = 7.6 to 12.7). The clinical benefit rate (CR+PR+SD>6 mos) for the 66 assessable patients is currently 45.5%. The majority (88%) of archival tumor specimens were moderately (2+) to strongly (3+) positive by IHC for Trop-2, precluding using Trop-2 expression as a selection criterion. Among current adverse events, grade >3 drug-related toxicities included neutropenia (35%), leukopenia (16%), anemia (13%), vomiting (9%), diarrhea (10%), and febrile neutropenia (4%). Clearance kinetics in 8 pts showed IMMU-132 and IgG had a terminal half-life of 15.3 ± 2.7 h and 86.5 ± 40.5 h, respectively, with area under the curve for free SN-38 (unbound) only 3% of the total amount of SN-38 (e.g., IgG bound). Thus, most SN-38 remains bound to the conjugate, and is released at a rate predicted from in vitro serum stability studies. No pt developed anti-IMMU-132 antibodies.

Conclusion The Trop-2-targeting ADC, IMMU-132, delivering cytotoxic doses of SN-38, shows high objective and durable tumor responses with manageable toxicity in heavily-pretreated pts with mTNBC in this updated cohort, supporting further development in this population with an unmet medical need.

Citation Format: Bardia A, Diamond JR, Mayer IA, Isakoff SJ, Abramson V, Starodub AN, O'Shaughnessy J, Kalinsky K, Moroose R, Shah N, Juric D, Shapiro GI, Guarino M, Ocean AJ, Messersmith WA, Berlin JD, Wegener WA, Sharkey RM, Goldenberg DM, Vahdat LT. Sacituzumab govitecan (IMMU-132), an anti-Trop-2-SN-38 antibody-drug conjugate (ADC) for the treatment of relapsed/refractory, metastatic triple-negative breast cancer (mTNBC): Updated results [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-22-15.

Palbociclib:CDK4/6 inhibition in the treatment of ER-positive breast cancer

Maintaining cell-cycle control has become a mainstay in treatment for many cancers. Cell-cycle manipulation can be especially valuable in breast cancer tumor cells that will often express hormone receptors that are amenable to anti-hormone receptor-targeted therapies. Despite these treatments, patients often progress, leading to other targeted agents being investigated to help promote progression-free survival. Cyclin-dependent kinases (CDKs) have been identified as contributors in the process of cell division. Combining inhibitors of CDKs with traditional endocrine treatments has shown significant progression-free survival in patients with metastatic breast cancer. One such CDK inhibitor, palbociclib, has shown great promise in the treatment of hormone receptor-positive breast cancer. In this article we review the traditional hormonal treatments of breast cancer, how CDK inhibition is beneficial in the treatment of this disease, and the preclinical and clinical data supporting the use of this medication.

Abstract PD3-06: Safety and efficacy of anti-Trop-2 antibody drug conjugate, sacituzumab govitecan (IMMU-132), in heavily pretreated patients with TNBC

Background: Triple-negative breast cancer (TNBC) comprises about 15% of all breast cancer types, and has a particularly aggressive course. Following first-line therapy, the median PFS is <3 months, and OS is <10 months. Therefore, new treatment strategies are needed. Since Trop-2 is expressed in >90% of TNBC, as measured by IHC, we conducted a trial to evaluate the safety and efficacy of a humanized anti-Trop-2 monoclonal antibody conjugated to a high concentration of SN-38, a camptothecin that is a topoisomerase I inhibitor and the active metabolite of the prodrug irinotecan, with 2-3 logs higher potency than the prodrug.

Methods: After establishing the optimal repeated dose in a Phase I trial (ClinicalTrials.gov, NCT01631552) involving many different solid cancer types, an expanded Phase II was undertaken in a number of cancers, including TNBC. Patients received 8 or 10 mg/kg IMMU-132 i.v. on days 1 and 8 of 21-day repeated cycles. Assessments of safety and response by RECIST1.1 were made weekly and bimonthly, respectively. Tumor biopsies (archival, at baseline prior to treatment, and at disease progression) were obtained when safe and feasible.

Results: As of May 10, 2015, 58 patients with TNBC, with a median of 4 prior therapies (range, 1-11), were treated with IMMU-132. Grade 3-4 toxicities included neutropenia (26%), febrile neutropenia (2%), diarrhea (2%), anemia (4%), and fatigue (4%). No patient developed antibodies to SN-38 or the antibody, and no patient discontinued therapy due to toxicity. Tumor responses were defined as ORR (CR+PR) in 31% of 49 evaluated patients, including 2 with CR, and a clinical benefit ratio (CR+PR+SD>6 mo) of 49% (63% with SD>4 mo; 23 patients continuing treatment after 1st assessment). The current median progression-free survival is 7.3 months with 44% maturity in 50 patients treated at the 8 or 10 mg/kg dose level. Overall survival data are still not mature 20 months after enrollment of first patient. Clinical efficacy correlated to biomarker studies, including Trop-2 expression (target of antibody), topoisomerase-1 expression (target of SN-38), and homologous recombinant deficiency (HRD) assay (marker of DNA repair), is being studied. Immunohistochemistry results in archival specimens currently show 97% positivity of Trop-2 among 34 specimens evaluated, with 79% having high intensity (2+/3+) staining.

Conclusions: The Trop-2-targeting IMMU-132, delivering cytotoxic doses of the topoisomerase I inhibitor, SN-38, shows manageable toxicity, and encouraging anti-tumor activity in relapsed/refractory patients with TNBC. This ADC appears to have a high therapeutic index in heavily pretreated patients.

Citation Format: Bardia A, Diamond JR, Mayer IA, Starodub AN, Moroose RL, Isakoff SJ, Ocean AJ, Guarino MJ, Berlin JD, Messersmith WA, Thomas SS, O'Shaughnessy JA, Kalinsky K, Maurer M, Chang JC, Forero A, Traina T, Gucalp A, Wilhelm F, Wegener WA, Maliakal P, Sharkey RM, Goldenberg DM, Vahdat LT. Safety and efficacy of anti-Trop-2 antibody drug conjugate, sacituzumab govitecan (IMMU-132), in heavily pretreated patients with TNBC. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr PD3-06.

Phase I Study of DMOT4039A, an Antibody-Drug Conjugate Targeting Mesothelin, in Patients with Unresectable Pancreatic or Platinum-Resistant Ovarian Cancer

DMOT4039A, a humanized anti-mesothelin mAb conjugated to the antimitotic agent monomethyl auristatin E (MMAE), was given to patients with pancreatic and ovarian cancer every 3 weeks (0.2-2.8 mg/kg; q3w) or weekly (0.8-1.2 mg/kg). A 3+3 design was used for dose escalation followed by expansion at the recommended phase II dose (RP2D) to evaluate safety and pharmacokinetics. Antitumor response was evaluated per RECIST 1.1 and serum CA19-9 or CA125 declines. Tumor mesothelin expression was determined by IHC. Seventy-one patients (40 pancreatic cancer; 31 ovarian cancer) were treated with DMOT4039A. For the q3w schedule (n = 54), the MTD and RP2D was 2.4 mg/kg, with dose-limiting toxicities of grade 3 hyperglycemia and grade 3 hypophosphatemia at 2.8 mg/kg. For the weekly schedule (n = 17), the maximum assessed dose was 1.2 mg/kg, with further dose escalations deferred because of toxicities limiting scheduled retreatment in later cycles, and therefore the RP2D level for the weekly regimen was determined to be 1 mg/kg. Across both schedules, the most common toxicities were gastrointestinal and constitutional. Treatment-related serious adverse events occurred in 6 patients; 4 patients continued treatment following dose reductions. Drug exposure as measured by antibody-conjugated MMAE and total antibody was generally dose proportional over all dose levels on both schedules. A total of 6 patients had confirmed partial responses (4 ovarian; 2 pancreatic) with DMOT4039A at 2.4 to 2.8 mg/kg i.v. q3w. DMOT4039A administered at doses up to 2.4 mg/kg q3w and 1.0 mg/kg weekly has a tolerable safety profile and antitumor activity in both pancreatic and ovarian cancer.

An integrated bioinformatics analysis to dissect kinase dependency in triple negative breast cancer

BACKGROUND

Triple-Negative Breast Cancer (TNBC) is an aggressive disease with a poor prognosis. Clinically, TNBC patients have limited treatment options besides chemotherapy. The goal of this study was to determine the kinase dependency in TNBC cell lines and to predict compounds that could inhibit these kinases using integrative bioinformatics analysis.

RESULTS

We integrated publicly available gene expression data, high-throughput pharmacological profiling data, and quantitative in vitro kinase binding data to determine the kinase dependency in 12 TNBC cell lines. We employed Kinase Addiction Ranker (KAR), a novel bioinformatics approach, which integrated these data sources to dissect kinase dependency in TNBC cell lines. We then used the kinase dependency predicted by KAR for each TNBC cell line to query K-Map for compounds targeting these kinases. We validated our predictions using published and new experimental data.

CONCLUSIONS

In summary, we implemented an integrative bioinformatics analysis that determines kinase dependency in TNBC. Our analysis revealed candidate kinases as potential targets in TNBC for further pharmacological and biological studies.

Abstract C34: Senescence as a mechanism of resistance to the Aurora kinase and angiokinase inhibitor, ENMD-2076, in p53 mutated triple-negative breast cancer (TNBC) models

Background: Despite advances in targeted therapies for cancer, TNBC remains an aggressive breast cancer subtype with limited treatment options. Mutations in p53 are common in TNBC, however, the exact contribution of individual p53 mutations to response to therapy and mechanisms of acquired resistance are unknown. The purpose of this study was to characterize the activity of ENMD-2076, a multi-target Aurora kinase A and angiokinase inhibitor, against p53 mutated TNBC patient-derived tumor xenografts (PDX) and to identify differences in molecular pathways determining cellular fate in sensitive and resistant models.

Methods: TNBC PDX models harboring different p53 mutations were used for ENMD-2076 treatment studies. Athymic nude mice were injected with tumor tissue and tumor volumes were measured twice a week. When the mean tumor volumes reached 150 mm3, mice were randomized and treated with vehicle control or ENMD-2076 200 mg/kg by oral gavage daily. A subset of animals were sacrificed at Day 4, 30, and at the time of acquired resistance for correlative tissue testing which included: immunofluorescence (IF) for p53, p73, BCL2, BAX, p16, phospho Aurora A (pAA) and phospho histone H3 (pHH3); immunohistochemistry (IHC) for cleaved caspase 3 (CC3) and Ki67; H&E and staining for senescence associated beta-galactosidase (SA -βgal) activity. Tumor growth inhibition (TGI) was calculated at Day 30 and sensitive models were treated until resistance when additional correlative tissue samples were obtained.

Results: ENMD-2076 had significant anti-tumor activity against the CU_002 and CU_005 TNBC PDX models (TGI 71.3%, p value <0.0001; TGI 66.1% p value < 0.0002, respectfully). The CU_004 TNBC PDX model was intrinsically resistant to ENMD-2076 treatment (TGI 37%, p value 0.07). In the two sensitive PDX models, we observed an increase in p53, p73, BAX and the apoptotic marker CC3. This was accompanied by a decrease in the anti-apoptotic protein BCL2 and the proliferation marker Ki67 following treatment at Day 30. Consistent with Aurora kinase A inhibition, we detected an increase in pAA and a decrease in pHH3 expression in both sensitive and resistant PDTX models following treatment at Day 4 and Day 30. At the time of acquired resistance, defined by at least doubling of tumor volumes from the maximal response, we observed loss of p73, p53, and BAX expression and an increase in p16 staining and SA β-gal activity consistent with senescence. These findings were also observed following treatment with ENMD-2076 in the intrinsically resistant CU_004 model.

Conclusions: ENMD-2076 has pro-apoptotic anti-cancer activity in a subset of p53 mutated TNBC PDX models. Sensitivity was associated with the induction of p73, which may mediate the response in the absence of functional p53. Intrinsic and acquired resistance to ENMD-2076 in TNBC PTX models was associated with loss of p73 expression and an increase in markers associated with senescence, including p16 expression and SA β-gal activity. These data support the role of senescence as a potential mechanism of resistance to Aurora kinase inhibitors in p53 mutated TNBC and support the continued development of combination therapies including with inhibitors of pathways that mediate senescence.

Citation Format: Anastasia A. Ionkina, S. Gail Eckhardt, Todd M. Pitts, Carol Sartorius, Peter Kabos, Jiyhe Kim, Aik Choon Tan, John J. Tentler, Jennifer R. Diamond. Senescence as a mechanism of resistance to the Aurora kinase and angiokinase inhibitor, ENMD-2076, in p53 mutated triple-negative breast cancer (TNBC) models. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C34.

Trastuzumab emtansine and stereotactic radiosurgery: an unexpected increase in clinically significant brain edema

BACKGROUND

In the last 10 years, multiple new targeted agents have been developed for patients with human epidermal growth factor receptor 2-positive (HER2+) breast cancer. Up to 55% of patients with HER2+ breast cancer will develop brain metastases requiring some form of radiation therapy. The interaction between radiation and these targeted agents is unknown and previously unreported.

METHODS

In this series, we describe 4 patients who developed clinically significant brain edema at sites of treated brain metastases. These patients were treated with stereotactic radiosurgery and trastuzumab emtansine, the newest FDA-approved agent for metastatic HER2+ breast cancer. Additionally, we present rates of clinically significant radiation necrosis among all breast cancer patients treated during this same time period.

RESULTS

Using previously published clinical and preclinical data, we then hypothesize possible mechanisms for this striking interaction.

CONCLUSION

Increased awareness of potential interactions between targeted agents and radiation to the brain is crucial.

A Phase I First-in-Human Study of Enoticumab (REGN421), a Fully Human Delta-like Ligand 4 (Dll4) Monoclonal Antibody in Patients with Advanced Solid Tumors

PURPOSE

Enoticumab (REGN421) is a fully human IgG1 monoclonal antibody that binds human Dll4 and disrupts Notch-mediated signaling. The main objectives of this trial were to determine the safety, dose-limiting toxicities (DLT), pharmacokinetics (PK), and recommended phase II dose (RP2D) of enoticumab.

EXPERIMENTAL DESIGN

Enoticumab was administered intravenously, with dose escalations from 0.25 to 4 mg/kg every 3 weeks (Q3W) and 0.75 to 3 mg/kg every 2 weeks (Q2W).

RESULTS

Of 53 enrolled patients, 31 patients were treated Q3W and 22 patients were treated Q2W. Two DLTs occurred: grade 3 nausea (0.5 mg/kg Q3W) and grade 3 abdominal pain (1 mg/kg Q2W). An MTD was not reached on either schedule. The most frequent adverse events (AE) were fatigue, nausea, vomiting, hypertension, headache, and anorexia. Six treatment-related serious AEs were reported in 4 patients: brain natriuretic peptide (BNP) increase (0.25 mg/kg Q3W, Gr1), troponin I increase (4 mg/kg Q3W, Gr3), right ventricular dysfunction and pulmonary hypertension (1.5 mg/kg Q2W, both Gr3), and left ventricular dysfunction and pulmonary hypertension (3 mg/kg Q2W, both Gr3). Enoticumab was characterized by nonlinear, target-mediated PK, and had a terminal half-life of 8 to 9 days. With multiple Q2W or Q3W dosing, accumulation was not observed. Antitumor activity included two partial responses (non-small cell lung cancer bronchoalveolar-type with a β-catenin mutation, and ovarian cancer) and 16 patients with stable disease (3> 6 months).

CONCLUSIONS

Enoticumab was tolerated, with RP2D of 4 mg/kg Q3W and 3 mg/kg Q2W based on PK profile and clinical activity. Responses and SD were noted in ovarian cancer and other solid tumors. Clin Cancer Res; 21(12); 2695-703. ©2015 AACR.

Pharmacokinetic drug-drug interaction study of the angiopoietin-1/angiopoietin-2-inhibiting peptibody trebananib (AMG 386) and paclitaxel in patients with advanced solid tumors

BACKGROUND

Trebananib is an anti-angiogenic peptibody under investigation in patients with advanced cancer. This study evaluated the pharmacokinetic (PK) drug-drug interaction of paclitaxel and trebananib.

PATIENTS AND METHODS

Patients with advanced solid tumors received weekly 80 mg/m(2) intravenous (IV) paclitaxel (3 weeks on/1 week off) with weekly 15 mg/kg IV trebananib starting at Week 2. Blood samples for PK analysis were collected at Week 1 (paclitaxel alone), Week 6 (paclitaxel and trebananib), and Week 8 (trebananib alone). An absence of interaction was to be concluded if the 90 % confidence intervals (CI) for the differences in paclitaxel exposure fell within the 0.80-1.25 interval.

RESULTS

The primary study was conducted between 7/2012 and 10/2013. Thirty-five patients were enrolled and 34 received both treatments. Most patients were white (91 %) and female (59 %); mean age was 61 years. The most common tumor types were ovarian (32 %) and bladder (27 %), 71 % of patients had stage IV disease, and all had Eastern Cooperative Oncology Group (ECOG) scores of 0 or 1. PK parameter analysis was done on patients with evaluable PK data at both assessments (with and without concomitant therapy; n = 28). The geometric least squares mean (GLSM) ratio (90 % CI) of paclitaxel AUCinf with and without trebananib was 1.17 (1.10, 1.25). The GLSM ratio (90 % CI) of trebananib AUCtau,ss with and without paclitaxel was 0.92 (0.87, 0.97). The most common adverse events were fatigue, local edema, peripheral edema, and nausea.

CONCLUSIONS

This study showed no evidence of clinically meaningful PK interaction between paclitaxel and trebananib.

p53 Family Members Regulate Phenotypic Response to Aurora Kinase A Inhibition in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is an aggressive disease with a poor prognosis. Advances in the treatment of TNBC have been hampered by the lack of novel effective targeted therapies. The primary goal of this study was to evaluate the efficacy of targeting Aurora kinase A (AurA), a key regulator of mitosis, in TNBC models. A secondary objective was to determine the role of the p53 family of transcriptional regulators, commonly mutated in TNBC, in determining the phenotypic response to the AurA inhibitor alisertib (MLN8237). Alisertib exhibited potent antiproliferative and proapoptotic activity in a subset of TNBC models. The induction of apoptosis in response to alisertib exposure was dependent on p53 and p73 activity. In the absence of functional p53 or p73, there was a shift in the phenotypic response following alisertib exposure from apoptosis to cellular senescence. In addition, senescence was observed in patient-derived tumor xenografts with acquired resistance to alisertib treatment. AurA inhibitors are a promising class of novel therapeutics in TNBC. The role of p53 and p73 in mediating the phenotypic response to antimitotic agents in TNBC may be harnessed to develop an effective biomarker selection strategy in this difficult to target disease.

Triple-negative breast cancer: bridging the gap from cancer genomics to predictive biomarkers

Triple-negative breast cancer (TNBC) represents a challenge clinically due to a lack of response to hormonal and HER2-targeted agents coupled with an aggressive disease course. As the biology of this breast cancer subtype is better understood, it is clear that TNBC is a heterogeneous disease and one targeted therapy is unlikely to be active in all patients. Biomarkers predictive of response to treatment are thus of great importance in TNBC. This review outlines studies evaluating biomarkers predictive of response to neoadjuvant chemotherapy and to targeted therapies in the advanced setting. The development of validated biomarkers in conjunction with novel targeted therapies represents an opportunity to improve patient outcomes in TNBC.

Phase I study of oral rigosertib (ON 01910.Na), a dual inhibitor of the PI3K and Plk1 pathways, in adult patients with advanced solid malignancies

PURPOSE

To determine the pharmacokinetics (PK), maximum tolerated dose (MTD), safety, and antitumor activity of an oral formulation of rigosertib, a dual phosphoinositide 3-kinase (PI3K) and polo-like kinase 1 (Plk1) pathway inhibitor, in patients with advanced solid malignancies.

EXPERIMENTAL DESIGN

Patients with advanced solid malignancies received rigosertib twice daily continuously in 21-day cycles. Doses were escalated until intolerable grade ≥2 toxicities, at which point the previous dose level was expanded to define the MTD. All patients were assessed for safety, PK, and response. Urinary PK were performed at the MTD. Archival tumors were assessed for potential molecular biomarkers with multiplex mutation testing. A subset of squamous cell carcinomas (SCC) underwent exome sequencing.

RESULTS

Forty-eight patients received a median of 2 cycles of therapy at 5 dose levels. Rigosertib exposure increased with escalating doses. Dose-limiting toxicities were hematuria and dysuria. The most common grade ≥2 drug-related toxicities involved urothelial irritation. The MTD is 560 mg twice daily. Activity was seen in head and neck SCCs (1 complete response, 1 partial response) and stable disease for ≥12 weeks was observed in 8 additional patients. Tumors experiencing ≥partial response had PI3K pathway activation, inactivated p53, and unique variants in ROBO3 and FAT1, two genes interacting with the Wnt/β-catenin pathway.

CONCLUSIONS

The recommended phase II dose of oral rigosertib is 560 mg twice daily given continuously. Urinary toxicity is the dose-limiting and most common toxicity. Alterations in PI3K, p53, and Wnt/β-catenin pathway signaling should be investigated as potential biomarkers of response in future trials.

The integration of locoregional with systemic adjuvant therapy for early-stage breast cancer: the shifting sands of decision-making

SUMMARY Given the generally excellent outcomes for modern breast cancer treatment, the recognition that overtreatment is commonplace is the driving force to reduce the treatment impact of surgery, radiation therapy and chemotherapy. Many recent trials have demonstrated that fewer axillary lymph node dissections, smaller radiation field sizes and less administration of chemotherapy are all feasible without compromising the long-term outcomes. However, each of these trials has studied a single modality while maintaining the intensities of the other modalities. There is a natural tendency, albeit controversial, to reduce more than one modality at a time. We review the literature, and counsel the breast cancer oncologist to work as a multimodality team to decide with the patient which modality can be reduced, and which should be preserved in its intensity.

Retrospective analysis of survival improvement by molecular biomarker-based personalized chemotherapy for recurrent ovarian cancer

Aggressive tumors such as epithelial ovarian cancer (EOC) are highly heterogeneous in their therapeutic response, making it difficult to improve overall response by using drugs in unselected patients. The goal of this study was to retrospectively, but independently, examine whether biomarker-based personalized chemotherapy selection could improve survival of EOC patients. Using in vitro drug sensitivity and patient clinical outcome data, we have developed co-expression extrapolation (COXEN) biomarker models for predicting patient response to three standard chemotherapy drugs used to treat advanced EOC: paclitaxel, cyclophosphamide, and topotecan, for which sufficient patient data were available for our modeling and independent validation. Four different cohorts of 783 EOC patients were used in our study, including two cohorts of 499 patients for independent validation. The COXEN predictors for the three drugs independently showed high prediction both for patient short-term therapeutic response and long-term survival for recurrent EOC. We then examined the potential clinical benefit of the simultaneous use of the three drug predictors for a large diverse EOC cohort in a prospective manner, finding that the median overall survival was 21 months longer for recurrent EOC patients who were treated with the predicted most effective chemotherapies. Survival improvement was greater for platinum-sensitive patients if they were treated with the predicted most beneficial drugs. Following the FDA guidelines for diagnostic prediction analysis, our study has retrospectively, yet independently, showed a potential for biomarker-based personalized chemotherapy selection to significantly improve survival of patients in the heterogeneous EOC population when using standard chemotherapies.

Abstract P2-09-06: The role of p53 family tumor suppressors in mediating response to aurora kinase inhibition in triple-negative breast cancer

Background: Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype defined by the lack of expression of the estrogen and progesterone receptors and lack of HER2 over-expression. TNBC carries an increased risk of developing distant metastatic disease and cancer-related death. TNBC is heterogeneous in its underlying biology, however, mutations in p53 are found in approximately 80% of tumors. The purpose of this study was to utilize TNBC cell line models to investigate the role of p53 and p73 in mediating sensitivity to MLN8237, a selective Aurora kinase A inhibitor, in the setting of mutant or wildtype p53. Additionally, we used p53 and p73 knock-down models to determine the role of p53 and p73 in mediating induction of apoptosis and cellular senescence in response to Aurora kinase inhibition.

Methods: Eighteen TNBC cell lines were exposed to MLN8237 and the effects on proliferation, apoptosis, and cell cycle distribution were evaluated. Proliferation was assessed using an SRB assay, apoptosis was analyzed using a caspase 3/7 assay and cell cycle was measured using flow cytometry. Proliferation was confirmed using a cell counting technique to control for an increase in cell size following MLN8237 exposure. The p53 wildtype TNBC cell line CAL51 was transduced with several clones of shRNA constructs targeting p53 and p73 with > 80% knockdown by RT-PCR. These clones were exposed to escalating doses of MLN8237 and the effect on proliferation was determined using an SRB assay and the effect on cellular senescence was determined using a senescence associated beta-galactosidase (SA b-gal) assay.

Results: In vitro exposure to MLN8237 resulted in robust inhibition of proliferation in TNBC cell lines which was associated with dose-dependent G2/M cell cycle arrest and induction of caspase-dependent apoptosis in a subset of sensitive cell lines. Knock-down of p53 and p73 in the CAL51 cell line resulted in an increase in the absolute 50% inhibitory concentration (IC50) calculated from the SRB proliferation assay curves from 0.04 μM to > 2 μM, 1.8 μM, > 2 μM and 1.5 μM in the CAL51scr, CAL51p5310, CAL51p5312, CAL51p7326, CAL51p7355, respectively. The sensitive p53 mutated MDA-MB-468 cell line (IC50 40 nM) and the sensitive p53 wild-type CAL51 cell line (IC50 45 nM) were selected for further experimentation. Exposure to MLN8237 at concentrations of 50 nM and 100 nM for 7 days resulted in induction of cellular senescence as detected by the SA b-gal assay in the CAL51 p53 wild-type cell line, but not in the MDA-MB-468 cell line where induction of apoptosis at 48 hours was observed using the caspase 3/7 assay. In the CAL51 p73 knock-down clones, induction of cellular senescence was not observed following exposure to MLN8237.

Conclusions: MLN8237 exhibited robust anticancer activity towards preclinical models of p53 mutated and p53 wild-type TNBC, supporting future clinical investigation of Aurora kinase inhibitors in TNBC. In p53 wild-type TNBC, both p53 and p73 mediate sensitivity to MLN8237 and p73 is essential for induction of cellular senescence following exposure to MLN8237. Biomarkers predictive of response to MLN8237 in p53 mutated TNBC are being developed.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-09-06.

Abstract A286: The role of p53 family tumor suppressors in mediating response to the Aurora and angiogenic kinase inhibitor ENMD-2076 in triple-negative breast cancer

Background: Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype defined by the lack of expression of ER, PR and HER2 over-expression. TNBC is heterogeneous in its biology, however, mutations in p53 are found in approximately 80% of tumors. The purpose of this study was to utilize TNBC cell line models to investigate the role of p53 and p73 in mediating sensitivity to ENMD-2076, a selective Aurora kinase A inhibitor (AurKi). p53 and p73 knockdown (KD) models were developed to determine their role in mediating induction of apoptosis and senescence in response to AurK inhibition. Additionally, the effects of combining ENMD-2076 with the p53 modulator nutlin-3 were assessed.

Methods: TNBC cell lines, MDA-MB-468 (p53 mut) and CAL51 (p53 WT) were transduced with shRNA constructs targeting p53 and p73 with > 80% knockdown as determined by RT-PCR. These clones were exposed to escalating doses of ENMD-2076 and the effect on proliferation was determined using an SRB assay. Proliferation was assessed using an SRB assay, and confirmed using a direct cell counting to control for increase in cell size following ENMD-2076 exposure. In the CAL51 KD lines, the effects of ENMD-2076 treatment on cellular senescence were determined using a senescence associated beta-galactosidase (SA β-gal) assay. Combination studies with nutlin-3 in MDA-MB-468 and HCC1937 were assessed by SRB and synergy measured using Calcusyn software.

Results: KD of p53 and p73 in the MDA-MB-468p5310, MDA-MB-468p7355 cell lines resulted in an increase in the IC50 from 0.625 μM to 1.5 μM compared to scrambled. KD of CAL51 p53 and p73 increased from 0.16 µM to 0.41 µM, and 1.3 µM, in the CAL51scr, CAL51p5310, CAL51p7326, respectively. The sensitive MDA-MB-468 cell line (IC50 40 nM) and the sensitive CAL51 cell line (IC50 45 nM) were selected for further experimentation. Exposure to ENMD-2076 at concentrations of 0.5 μM and 1 μM for varying time points resulted in induction of senescence in the CAL51 cell line, but not in the MDA-MB-468 cell line, where induction of apoptosis at 48 hours was observed. In CAL51 p53 and p73 KD clones, induction of senescence was observed following exposure to ENMD-2076. Combination treatment with nutlin-3 showed synergistic activity.

Conclusions: ENMD-2076 exhibited robust anticancer activity towards preclinical models of TNBC, in both p53 mutated and p53 WT cell lines, supporting future clinical investigation of AurKi in TNBC. In p53 WT TNBC, both p53 and p73 mediate sensitivity to ENMD-2076 and p73 is essential for induction of senescence following exposure to ENMD-2076. Synergistic anticancer activity of ENMD-2076 and nutlin reinforces the role of p53 in Aurora kinase inhibition of TNBC. Biomarkers predictive of response to ENMD-2076 in p53 mutated TNBC are being developed. These results with p53 KD cell lines are currently being confirmed in vivo.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A286.

Citation Format: Anastasia A. Ionkina, John J. Tentler, Timothy P. Newton, Kelsey L. Brunkow, Jared S. Johnson, Aik Choon Tan, Todd M. Pitts, S. Gail Eckhardt, Jennifer R. Diamond. The role of p53 family tumor suppressors in mediating response to the Aurora and angiogenic kinase inhibitor ENMD-2076 in triple-negative breast cancer. [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 A286.

From bench to bedside: lessons learned in translating preclinical studies in cancer drug development

The development of targeted agents in oncology has rapidly expanded over the past 2 decades and has led to clinically significant improvements in the treatment of numerous cancers. Unfortunately, not all success at the bench in preclinical experiments has translated to success at the bedside. As preclinical studies shift toward defining proof of mechanism, patient selection, and rational drug combinations, it is critical to understand the lessons learned from prior translational studies to gain an understanding of prior drug development successes and failures. By learning from prior drug development, future translational studies will provide more clinically relevant data, and the underlying hope is that the clinical success rate will improve and the treatment of patients with ineffective targeted therapy will be limited.

Medullary thyroid cancer and pseudocirrhosis: case report and literature review

Pseudocirrhosis is a rare form of liver disease that can cause clinical symptoms and radiographic signs of cirrhosis; however, its histologic features suggest a distinct pathologic process. In the setting of cancer, hepatic metastases and systemic chemotherapy are suspected causes of pseudocirrhosis. Here, we present a patient with medullary thyroid carcinoma metastatic to the liver who developed pseudocirrhosis while on maintenance sunitinib after receiving 5-fluorouracil, leucovorin, and oxaliplatin (folfox) in combination with sunitinib. Cirrhotic change in liver morphology was accompanied by diffusely infiltrative carcinomatous disease resembling the primary tumor. We discuss the diagnosis of pseudocirrhosis in this case and review the literature regarding pseudocirrhosis in cancer.

Abstract 1006: A novel class I histone deacetylase (HDAC) inhibitor, paragazole, demonstrates antiproliferative and proapoptotic effects in triple-negative breast cancer models

Introduction: Triple-negative breast cancer (TNBC) is a clinically aggressive breast cancer subtype which lacks estrogen receptor expression. Histone deacetylase (HDAC) inhibitors have previously been shown to induce estrogen receptor expression in TNBC models. Paragazole is a selective class I HDAC inhibitor (HDACs 1, 2, and 3) currently in preclinical development. In this project, we explored the antiproliferative and proapoptotic activity of paragazole and investigated the combination of paragazole and chemotherapy in a panel of breast cancer cell lines.

Methods: Breast cancer cell lines were exposed to varying sub-micromolar concentrations of paragazole alone and in combination with carboplatin, paclitaxel, and gemcitabine. Proliferation was assessed using an SRB assay and analyzed using the Calcusyn program, whereby synergy was defined as a Combination Index of less than 1. Cell cycle analysis was performed using flow cytometry and apoptosis was analyzed using a caspase 3/7 assay. Baseline HDAC expression was measured by RT-PCR and RNA-Seq was used pre- and post-treatment in a subset of 2 sensitive and 2 resistant cell lines.

Results: Exposure to paragazole resulted in a decrease in cell proliferation at submicromolar concentrations with more robust antiproliferative activity observed in the TNBC cell lines compared to the estrogen receptor positive cell lines. An increase in apoptosis that was maximal at 24-48 hours was observed with single agent paragazole in a subset of sensitive TNBC cell lines. The combinations of paragazole with either paclitaxel, gemcitabine, or carboplatin all resulted in additive or synergistic growth inhibition. Expression of HDAC 1 was higher in the sensitive TNBC cell lines than in the resistant lines. Exposure to paragazole led to an increase in CARM1 mediated estrogen receptor expression.

Discussion: These in vitro results demonstrate that paragazole has antiproliferative and proapototic activity against TNBC cell lines and may potentiate the activity of chemotherapy. These data support confirmation of the findings using in vivo models and the investigation of paragazole in combination with anti-estrogen agents such as tamoxifen and fulvestrant.

Citation Format: David P. Astling, John J. Tentler, Benjamin R. Cross, Timothy P. Newton, Todd M. Pitts, Eric Gunther, Xuedong Liu, S. Gail Eckhardt, Jennifer R. Diamond. A novel class I histone deacetylase (HDAC) inhibitor, paragazole, demonstrates antiproliferative and proapoptotic effects in triple-negative breast cancer models. [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 1006. doi:10.1158/1538-7445.AM2013-1006

Abstract P4-04-06: Young women's breast cancer is characterized by increased immune suppression through circulating myeloid derived supressor cells

Background: Women age 20–40 have a higher ten-year risk for developing breast cancer than the five other leading cancers in this gender and age group combined. Women currently in their 30s have a 1/203 chance of developing breast cancer over the next ten years. Moreover, cancers diagnosed in younger women have a signficantly higher risk of death for reasons that are not fully identified. Myeloid derived suppressor cells (MDSC) have a role in suppressing anti-tumor immunity through Jak/Stat pathway activation by generation of reactive oxygen species (ROS) and arginase-1, and correlate preclinically with cancer progression and in human canceres with poorer prognositic features and outcomes. Our Young Women's Breast Cancer Translational Program seeks to identify immunologic differences potentially contributing to the poorer prognosis and potential targets for development of immunomodulatory treatment.

Hypothesis: We hypothesized that newly diagnosed, treatment-naive young breast cancer cases would have higher percentage of circulating MDSC with T cell suppressive function than similar age women without breast cancer.

Methods: We conducted IRB approved, prospective translational studies of women age 40 and under both affected and unaffected by breast cancer. Exclusion criteria included pregnancy, known autoimmunity or immunosuppressive medications, or other cancers. MDSC were isolated from peripheral blood and phenotyped through standard protocols. T cell suppressive abilites were tested in coculture assays for expression of activation markers CD25 and CD69, and production of gamma-interferon. Identification of mechanism of suppression was assayed through secretion of arginase-1and generation of ROS.

Results: No difference in percentage of MDSC was identified between young women with breast cancer (n = 61) and unaffected subjects (n = 18). However, a statistically significant increase in the MDSC ability to suppress T cell activation was identified in the breast cancer cohort with diminished CD25 and CD69 expression and diminished production of gamma-interferon. MDSC from young breast cancer subjects secreted significantly more arginase-1 from MDSC. No significant difference in generation of ROS was found between the two cohorts.

Conclusions: The presence of equal rather than higher numbers of circulating MDSCs between the young breast cancer versus unaffected subjects was unexpected in comparison to prior publications on MDSC in cancer. Our results may differ due to our larger sample size or the alignment by gender and age the cohorts being more representative. Also, these are the first data on MDSC in a young female population. Despite equal numbers of MDSCs, the functional analyses demonstrate MDSC isolated from breast cancer have enhanced T cell suppression capabilities compared with normal controls. These data provacatively suggest a functional difference inherent to MDSC in the young breast cancer-bearing host. Moreover, they indicate that normal young women have realtively high levels of MDSC that are available for cancer to ursurp and induce immune suppression. Identification of secretion of arginine-1 as a potential mechanism of immune supporession in young women's breast cancer warrants further investigation.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-04-06.

Predictive biomarkers of sensitivity to the aurora and angiogenic kinase inhibitor ENMD-2076 in preclinical breast cancer models

PURPOSE

The Aurora kinases are a family of conserved serine-threonine kinases with key roles in mitotic cell division. As with other promising anticancer targets, patient selection strategies to identify a responsive subtype will likely be required for successful clinical development of Aurora kinase inhibitors. The purpose of this study was to evaluate the antitumor activity of the Aurora and angiogenic kinase inhibitor ENMD-2076 against preclinical models of breast cancer with identification of candidate predictive biomarkers.

EXPERIMENTAL DESIGN

Twenty-nine breast cancer cell lines were exposed to ENMD-2076 and the effects on proliferation, apoptosis, and cell-cycle distribution were evaluated. In vitro activity was confirmed in MDA-MB-468 and MDA-MB-231 triple-negative breast cancer xenografts. Systematic gene expression analysis was used to identify up- and downregulated pathways in the sensitive and resistant cell lines, including within the triple-negative breast cancer subset.

RESULTS

ENMD-2076 showed antiproliferative activity against breast cancer cell lines, with more robust activity against cell lines lacking estrogen receptor expression and those without increased HER2 expression. Within the triple-negative breast cancer subset, cell lines with a p53 mutation and increased p53 expression were more sensitive to the cytotoxic and proapoptotic effects of ENMD-2076 exposure than cell lines with decreased p53 expression.

CONCLUSIONS

ENMD-2076 exhibited robust anticancer activity against models of triple-negative breast cancer and the candidate predictive biomarkers identified in this study may be useful in selecting patients for Aurora kinase inhibitors in the future.

P3-01-08: In Vitro and In Vivo Antitumor Activity of the Aurora and Angiogenic Kinase Inhibitor ENMD-2076 in Triple-Negative Breast Cancer Models

Background

Triple-negative breast cancer (TNBC) is an aggressive biologic subtype which lacks effective targeted anti-cancer agents and is characterized by a high mitotic index and dependence on angiogenesis. ENMD-2076 is a novel orally bioavailable Aurora and angiogenic kinase inhibitor currently in clinical development with favorable pharmacokinetics and a manageable toxicity profile. The purpose of this study was to use TNBC cell line-based in vitro and in vivo models to demonstrate the antitumor activity of ENMD-2076 towards this breast cancer subtype compared to the luminal and HER2−amplified subtypes. Additionally, we used baseline gene expression profiling and pathway analysis to explore molecular predictors of responsiveness to ENMD-2076 in TNBC.

Methods: Twenty-five breast cancer cell lines were exposed to ENMD-2076 and the effects on proliferation, apoptosis, and cell cycle distribution were evaluated. Proliferation was assessed using an SRB assay, apoptosis was analyzed using a caspase 3/7 assay and cell cycle was measured using flow cytometry. In vitro activity of ENMD-2076 was confirmed in 3-D cell culture and in MDA-MB-231 and MDA-MB-468 triple-negative breast cancer xenograft models and immunohistochemical analysis was performed for phosphor-histone H3 (pHH3). Gene array and gene set enrichment analysis (GSEA) was used to identify pathways differentially regulated in the sensitive and resistance cell lines, including within the triple-negative breast cancer subset.

Results: In vitro exposure to ENMD-2076 resulted in robust inhibition of proliferation in TNBC cell lines which was associated with a G2 cell cycle arrest and induction of caspase-dependent apoptosis. Of the TNBC cell lines screened, 1 of 10 had a mean IC50 value > 5 μmol/L and 7 of 10 had a mean IC50 ≤ 1 μmol/L (Fisher's exact test, p-value = 0.009). In comparison, only 1 luminal (ER+) and one UER2-amplified breast cancer cell line had an IC50 value < 1, whereas 7 and 5 resistant lines were luminal and HER2−amplified, respectively (Fisher's exact test, p-values = 0.02 and 0.11 for ER and HER2 status, respectively). ENMD-2076 exhibited antitumor activity towards MDA-MD-231 and MDA-MB-468 xenograft models of TNBC with statistically significant tumor growth inhibition compared to vehicle control (p< 0.05 and p< 0.01, respectively). A trend towards an increase in pHH3 staining cells in the MDA-MB-231 ENMD-2076 treated group compared to the vehicle control group was observed; however, this was not statistically significant (104.7 ± 36.2 positive cells/mm2 in treated vs. 79.9 ± 34.5 in control). Using significance of analysis of microarrays (SAM) analysis and GSEA, we identified Ran, a member of the mitotic spindle regulation pathway as upregulated in sensitive TNBC cell lines (p = 0.017). Interestingly, AURKA, the main target of ENMD-2076, is a core gene in this pathway.

Conclusions: ENMD-2076 exhibited robust anticancer activity towards preclinical models of TNBC, supporting future clinical investigations of this agent in TNBC with an emphasis on the continued development of biomarkers predictive of response in this breast cancer subset.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-01-08.