Abstract OT2-07-04: A phase 2 study of ONC201 in recurrent/refractory metastatic breast cancer and advanced endometrial carcinoma

Background: Advanced breast cancer (BC) and endometrial cancer (EC) have limited treatment options with no treatments improving survival. ONC201 is the founding member of a novel class of anticancer drugs called impiridones. The drug is orally bioavailable and crosses the blood brain barrier. Preclinical studies have demonstrated that ONC201 selectively kills various cancer cells, including all subtypes of BC and EC, while having little effect on normal cells. An on-going Phase 1 study of ONC201 has demonstrated clinical benefit in some solid tumors, including EC and glioblastomas.

Trial Design: Phase 2 single arm study of ONC201 with 3 cohorts: Cohort 1, female and male hormone receptor positive breast cancer (HR+BC); Cohort 2, female and male triple negative breast cancer (TNBC); and Cohort 3, EC. All patients will receive ONC201 at the recommended Phase 2 dose of 625mg by mouth q7 days (1 cycle = 28 days). Patients will undergo a baseline biopsy as well as a biopsy after 5 doses of ONC201 (C2D2). Patients will be evaluated for response every two cycles (8 weeks) by RECIST 1.1.

Eligibility Criteria: Measurable disease with >1 biopsiable lesion, willing to undergo biopsies. Cohort 1 (HR+BC) requires prior treatment with >2 lines of hormonal treatment. No prior treatment required for the other cohorts. Patients must have ECOG 0-1 and adequate organ function. Patients with asymptomatic or brain metastases treated > 4 weeks from study entry are eligible. Exclusion criteria include: symptomatic CNS metastases, radiotherapy ≤ 4 weeks from study entry, HIV, Hepatitis B or Hepatitis C.

Specific Aims: Primary objectives for this study are progression free survival (PFS) at 8 months for Cohort 1 (HR+BC) and overall response rate (ORR) for Cohorts 2 and 3 (TNBC and EC). Secondary objectives include safety, clinical benefit rate (CBR = partial response + complete response + stable disease), and overall survival.

Statistical Methods: This study has been designed to pause prior to full accrual to allow for evaluation of futility prior to proceeding to full accrual. In Cohort 1, if >1 of 5 patients is progression-free at 8 months, then we will recruit up to 24 patients. In Cohort 2, if >2 of 10 patients has clinical benefit then we will recruit up to 29 patients. For Cohort 3, if 1 of 13 patients has clinical benefit, then we will recruit up to 25 patients. Additional evaluations of tumor or blood samples performed will be done in an exploratory fashion, with results presented without any formal adjustment for multiple comparisons.

Target Accrual: 24 patients with HR+BC, 29 patients with TNBC, and 25 patients with EC.This trial will open Summer 2017 at the National Institutes of Health (Bethesda, MD).

Contact Information: Principal Investigator Alexandra S Zimmer, MD; alexandra.zimmer@nih.gov

Citation Format: Gatti-Mays ME, Greer Y, Steinberg S, Soltani S, Collins J, Olson M, Ojemuyiwa M, Annunziata C, Lee J-M, Nunes A, Lipkowitz S, Zimmer A. A phase 2 study of ONC201 in recurrent/refractory metastatic breast cancer and advanced endometrial carcinoma [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT2-07-04.

Prexasertib, a cell cycle checkpoint kinase 1 and 2 inhibitor, in BRCA wild-type recurrent high-grade serous ovarian cancer: a first-in-class proof-of-concept phase 2 study

Background

High-grade serous ovarian carcinoma (HGSOC) is characterized by TP53 mutations, DNA repair defects, and genomic instability. We hypothesized that prexasertib, a cell cycle checkpoint kinase 1 and 2 inhibitor, would be active in BRCA wild-type HGSOC.

Methods

In this open label, single centre, two-stage proof-of-concept phase 2 study, women aged 18 years or older with measurable, recurrent high-grade serous or high-grade endometrioid ovarian carcinoma were enrolled. All patients must have had either a negative family history of hereditary breast and ovarian cancer or known BRCA wild-type for BRCA wild-type cohort. Other key eligibility criteria were an Eastern Cooperative Oncology Group performance status of 0 or 1 or 2, and adequate haematological, renal, and hepatic function. Patients received intravenous prexasertib 105mg/m² once every 2 weeks until disease progression, unacceptable toxicity or patient withdrawal of consent. The primary endpoint was investigator-assessed tumour response per protocol based on Response Evaluation Criteria in Solid Tumors, version 1·1 in evaluable patients. The final analysis of this cohort is reported here. This ongoing trial is registered with ClinicalTrials.gov (NCT02203513) and enrolling the patients of BRCA mutation cohort.

Findings

Between January 2015 and November 2016, 28 women (median age 64-year-old [IQR 58–69·5], with median 5 prior systemic therapies [IQR 2·5–5]) were enrolled and received at least one dose of prexasertib. Eight of 24 evaluable patients had a partial response (PR; 33%, 95% CI: 16–55) and 50% had a GCIG CA125 response. The RR in the intention-to-treat population was 29% (8/28, 95% CI: 13–49). The common (>10%) grade 3 or 4 treatment-emergent adverse events were neutropenia (26 [93%] patients), thrombocytopenia (seven [25%] patients), and anaemia (three [11%] patients). Grade 4 neutropenia occurred in 22 (79%) patients after the first dose and was transient ≤ 7 days (median 6 days [IQR 4–8]) without growth factor support; the incidence of febrile neutropenia was 7% (2/28).

Interpretation

We demonstrate clinical activity of prexasertib in BRCA wild-type HGSOC, especially patients with platinum-resistant or refractory ovarian cancer. These results warrant further development for this unmet patient need.

Funding

Intramural Research Program of the National Institutes of Health, National Cancer Institute, Center for Cancer Research, USA.

Analysis of breast cancer in young women in the Department of Defense (DOD) database

PURPOSE

Breast tumors from young women under the age of 40 account for approximately 7% of cases and have a poor prognosis independent of established prognostic factors. We evaluated the patient population served by the Military Health System, where a disproportionate number of breast cancer cases in young women are seen and treated in a single universal coverage healthcare system.

METHODS

The Military Health System Repository and the DoD Central Registration databases were used to identify female breast cancer patients diagnosed or treated at military treatment facilities from 1998 to 2007.

RESULTS

10,066 women were diagnosed with invasive breast cancer at DoD facilities from 1998 to 2007, of which 11.3% (1139), 23.4% (2355) and 65.2% (6572) were < 40, 40-49 and > 50 years old (yo), respectively, at diagnosis. 53% in the < 40 yo cohort were white, 25% were African American (AA) and 8% were Hispanic, with 14% undisclosed. Breast cancer in women diagnosed < 40 yo was more high grade (p < 0.0001), Stage II (p < 0.0001) and ER negative (p < 0.0001). There was a higher rate of bilateral mastectomies among the women < 40 compared to those 40-49 and > 50 (18.4% vs. 9.1% and 5.0%, respectively). Independent of disease stage, chemotherapy was given more frequently to < 40 yo (90.43%) and 40-49 yo (81.44%) than ≥ 50 yo (53.71%). The 10-year overall survival of younger women was similar to the ≥ 50 yo cohort. Outcomes in the African American and Hispanic subpopulations were comparable to the overall cohort.

CONCLUSION

Younger women had a similar overall survival rate to older women despite receiving more aggressive treatment.

Abstract 1487: ONC201 kills breast cancer cells by inhibiting mitochondrial respiration

Background: ONC201 is a small molecule originally identified as a TRAIL inducing compound currently being tested in phase1/2 clinical trials in multiple cancer types. Two recent studies reported that ONC201 also induces an atypical stress response mediated in part by ATF4 and CHOP.

Methods: ONC201 was obtained from Oncoceutics, Inc. Recombinant GST-TRAIL was prepared in the laboratory. Cell viability was tested with MTS assay and CellTiter-Glo luminescent cell viability assay. ATP level was measured with CellTiter-Glo 2.0 assay. RNAseq and western blotting were performed to investigate change of gene expression. Mitochondrial respiration was monitored by Seahorse XF analyzer. Live cell imaging was performed to examine the mode of cell death. Confocal microscopy and electron microscopy analysis were performed to study mitochondrial morphology.

Results: We tested the effects of ONC201 on 18 human breast cancer cell lines that represent ER+, HER2 amplified, TNBC basal A and TNBC basal B breast cancer. ONC201 reduced cell viability in breast cancer cell lines in all subtypes tested with IC50s ranging from 0.8-5 μM, similar to what has been reported for other cancer cell types. Unexpectedly, ONC201 toxicity was not dependent on TRAIL receptors or caspases and live cell imaging revealed ONC201 induces cell membrane ballooning followed by rupture. By contrast, GST-TRAIL induced TRAIL-receptor dependent caspase mediated death and classic apoptosis morphology. These results suggest that ONC201 kills breast cancer cells via a caspase-independent, TRAIL-receptor-independent mechanism distinct from TRAIL-induced apoptosis. Western blots revealed that ONC201 induces the stress pathway proteins ATF4 and CHOP, consistent with the recently published observations. ONC201 also induced phosphorylation of AMP-dependent kinase (AMPK) and depletion of cellular ATP in multiple breast cancer cell lines. Seahorse XF analysis found that ONC201 inhibited mitochondrial oxygen consumption rate but did not inhibit glycolysis as measured by the extracellular acidification rate. Both ONC201-induced toxicity and ATP depletion were enhanced when cells were cultured in non-glucose (galactose) medium. Supplementing glucose to cells grown in galactose medium partially prevented ONC201-dependent ATP depletion, induction of phospho-AMPK, ATF4 and CHOP, and cell death. These data are consistent with an inhibition of oxidative phosphorylation (OxPhos) by ONC201. RNAseq revealed ONC201 inhibits expression of multiple mitochondrial genes involved in OxPhos and other mitochondrial functions, and western blot confirmed those findings. Confocal and electron microscopic evaluation revealed abnormal mitochondrial morphology.

Conclusion: Our data demonstrate that ONC201 can kill breast cancer cells by a novel mechanism involving disruption of mitochondrial morphology and inhibition of mitochondrial respiration.

Citation Format: Yoshimi Greer, Samuel Gilbert, Celia Islam, Yun Ji, Luca Gattinoni, Christina Stuelten, Natalie Porat-Shliom, Roberto Weigert, Xiantao Wang, Markus Hafner, Kunio Nagashima, Donna Voeller, Stanley Lipkowitz. ONC201 kills breast cancer cells by inhibiting mitochondrial respiration [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1487. doi:10.1158/1538-7445.AM2017-1487

Safety and Clinical Activity of the Programmed Death-Ligand 1 Inhibitor Durvalumab in Combination With Poly (ADP-Ribose) Polymerase Inhibitor Olaparib or Vascular Endothelial Growth Factor Receptor 1-3 Inhibitor Cediranib in Women's Cancers: A Dose-Escalation, Phase I Study

Purpose Data suggest that DNA damage by poly (ADP-ribose) polymerase inhibition and/or reduced vascular endothelial growth factor signaling by vascular endothelial growth factor receptor inhibition may complement antitumor activity of immune checkpoint blockade. We hypothesize the programmed death-ligand 1 (PD-L1) inhibitor, durvalumab, olaparib, or cediranib combinations are tolerable and active in recurrent women's cancers. Patients and Methods This phase I study tested durvalumab doublets in parallel 3 + 3 dose escalations. Durvalumab was administered at 10 mg/kg every 2 weeks or 1,500 mg every 4 weeks with either olaparib tablets twice daily or cediranib on two schedules. The primary end point was the recommended phase II dose (RP2D). Response rate and pharmacokinetic analysis were secondary end points. Results Between June 2015 and May 2016, 26 women were enrolled. The RP2D was durvalumab 1,500 mg every 4 weeks with olaparib 300 mg twice a day, or cediranib 20 mg, 5 days on/2 days off. No dose-limiting toxicity was recorded with durvalumab plus olaparib. The cediranib intermittent schedule (n = 6) was examined because of recurrent grade 2 and non-dose-limiting toxicity grade 3 and 4 adverse events (AEs) on the daily schedule (n = 8). Treatment-emergent AEs included hypertension (two of eight), diarrhea (two of eight), pulmonary embolism (two of eight), pulmonary hypertension (one of eight), and lymphopenia (one of eight). Durvalumab plus intermittent cediranib grade 3 and 4 AEs were hypertension (one of six) and fatigue (one of six). Exposure to durvalumab increased cediranib area under the curve and maximum plasma concentration on the daily, but not intermittent, schedules. Two partial responses (≥15 months and ≥ 11 months) and eight stable diseases ≥ 4 months (median, 8 months [4 to 14.5 months]) were seen in patients who received durvalumab plus olaparib, yielding an 83% disease control rate. Six partial responses (≥ 5 to ≥ 8 months) and three stable diseases ≥ 4 months (4 to ≥ 8 months) were seen in 12 evaluable patients who received durvalumab plus cediranib, for a 50% response rate and a 75% disease control rate. Response to therapy was independent of PD-L1 expression. Conclusion To our knowledge, this is the first reported anti-PD-L1 plus olaparib or cediranib combination therapy. The RP2Ds of durvalumab plus olaparib and durvalumab plus intermittent cediranib are tolerable and active. Phase II studies with biomarker evaluation are ongoing.

Phase I/Ib study of olaparib and carboplatin in women with triple negative breast cancer

PURPOSE

To investigate the safety, activity, and potential biomarkers of response to olaparib and carboplatin combination in sporadic triple negative breast cancer (TNBC). EXPERIMENTAL DESIGN: Metastatic or recurrent TNBC patients with no germline BRCA mutation or with BRCAPro scores <10% and a negative family history were eligible. A 3+3 dose escalation tested olaparib capsules (400mg bid, days1-7) with carboplatin AUC3-5 on day1 or 2 every 21 days, ≤ 8 cycles, with olaparib 400mg bid maintenance. Peripheral blood mononuclear cells were collected for polymorphisms and PAR levels, and paired tumor biopsies (pre-/post-cycle 1) for proteomics and apoptosis endpoints.

RESULTS

28 women were treated (median 5 prior regimens [0-12]). Dose-limiting toxicity was thrombocytopenia, and symptomatic hyponatremia with carboplatin AUC5. The maximum tolerated dose was olaparib 400mg bid+carboplatin AUC4. Grade 3 and 4 adverse events included neutropenia (36%), thrombocytopenia (11%), and anemia (11%). Responses included 1 complete response (CR; 69⁺months) and 5/27 partial responses (19%; median 4months [4-7]), for a response rate of 22%. Biomarker findings did not correlate with response. The long-term CR patient with prior negative BRCA testing was found to have deletion of BRCA1 exons1-2.

CONCLUSIONS

The olaparib/carboplatin combination is tolerable and has modest activity in sporadic TNBC patients. Further evaluation of predictive biomarkers to identify those with BRCA wild type who had response is warranted.

Engineered Multivalency Enhances Affibody-Based HER3 Inhibition and Downregulation in Cancer Cells

The receptor tyrosine kinase HER3 has emerged as a therapeutic target in ovarian, prostate, breast, lung, and other cancers due to its ability to potently activate the PI3K/Akt pathway, especially via dimerization with HER2, as well as for its role in mediating drug resistance. Enhanced efficacy of HER3-targeted therapeutics would therefore benefit a wide range of patients. This study evaluated the potential of multivalent presentation, through protein engineering, to enhance the effectiveness of HER3-targeted affibodies as alternatives to monoclonal antibody therapeutics. Assessment of multivalent affibodies on a variety of cancer cell lines revealed their broad ability to improve inhibition of Neuregulin (NRG)-induced HER3 and Akt phosphorylation compared to monovalent analogues. Engineered multivalency also promoted enhanced cancer cell growth inhibition by affibodies as single agents and as part of combination therapy approaches. Mechanistic investigations revealed that engineered multivalency enhanced affibody-mediated HER3 downregulation in multiple cancer cell types. Overall, these results highlight the promise of engineered multivalency as a general strategy for enhanced efficacy of HER3-targeted therapeutics against a variety of cancers.

Abstract PD6-01: Analysis of breast cancer in young women in the department of defense (DOD) database

Background: Women under the age of 40 account for approximately 7% percent of breast cancer patients. Breast tumors from young women are often ER-negative, occur in African-American patients, and have other indicators of high risk: yet, multivariate analyses demonstrated that young age is an independent predictor of poor outcome. Due to the unique nature of the patient population served by DOD, a disproportionate number of breast cancer cases in young women are seen. We compare the characteristics, treatment, and outcomes of young patients diagnosed with breast cancer with those of older patients.

Methods: The databases of the Military Health System Repository and the DOD Central Registration were used to identify female breast cancer patients treated at DOD facilities between 1998 and 2007. Information on demographics, breast cancer stage at diagnosis, definitive surgical treatments, systemic treatment, recurrence rate and overall survival was analyzed by age groups at the time of diagnosis (less than 40 years old, 40 to 49 years, and 50 years or older) using X2 testing with significance defined as p&lt; 0.05.

Results: We identified 10,066 women who were diagnosed with invasive breast cancer at DOD facilities between 1998 and 2007, of which 11.3% (1139) were less than 40 years old at diagnosis. 53% of this young cohort were white, 25% were African-American and 8% were Hispanic (14% undisclosed). The percentage of breast cancer among African-American women in the young cohort was higher than in the older cohorts (19.3% in 40-49yo and 10.6% in ≥50yo). High-grade tumors were significantly more frequent in the younger cohort when compared to the older group (49.5% vs 34.7% and 25.2%, p&lt;0.001). &lt;40yo most commonly presented with Stage II disease (45.3%) at diagnosis, while older groups were mostly diagnosed with Stage I disease (41.6% and 52.4%). The most common subtype of breast cancer across ages was ER+ disease, however, &lt;40yo group had proportionally less ER+ (49% vs 61% and 67.3%, P&lt;0.001). There was a higher rate of bilateral mastectomies among the young women (18.4% vs 9.1% and 5.0%, p&lt;0.0001). Independently of the stage of disease, chemotherapy was given significantly more frequently to &lt;40y (90.43%) and 40-49yo (81.44%) than ≥50yo (53.71%). The 10-year overall survival of younger women was similar to the ≥50yo cohort, despite intensive treatment.

Discussion: This study is one of the largest retrospective studies of women under 40 years old with breast cancer. Younger women with invasive breast cancer had more aggressive tumors presenting at higher stages. In this group with good access to healthcare, younger women still had a similar overall survival rate to older women despite receiving more aggressive treatment and potentially having fewer comorbidities than the older group.

Citation Format: Zimmer AS, Gatti-Mays M, Soltani S, Lipkowitz S, Steeg PS, Zhu K, Perkins JG, Hu H, Shao S, Brown D, Shriver CD. Analysis of breast cancer in young women in the department of defense (DOD) database [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 PD6-01.

Abstract P3-06-02: ONC201 kills breast cancer cells by inhibiting mitochondrial respiration

Background: ONC201 is a small molecule originally identified as a TRAIL inducing compound (Allen et al., Sci. Trans. Med 2013). Two recent studies reported that ONC201 also induces an atypical stress response mediated in part by ATF4 and CHOP (Klein et al., Sci. Signal 2016 and Ishizawa et al., Sci. Signal 2016). ONC201 is currently being tested in phase1/2 clinical trials in multiple cancer types. In this study, we tested the effects of ONC201 on human breast cancer cells.

Methods: We tested ONC201 in 18 human breast cancer cell lines that represent ER+, HER2 amplified, TNBC basal A and TNBC basal B breast cancer. Cell death was analyzed by MTS assay after 5 days of treatment. Cells were treated with GST-TRAIL in parallel for comparison. Z-VAD-FMK was used as a pan-caspase inhibitor. To verify the mechanism of action of ONC201, siRNA against death receptors (DR) 4 and 5 were transfected to cells and tested in MTS assay and Western blotting. Seahorse XF analyzer and live cell imaging were used to further characterize the effect of ONC201.

Results: ONC201 reduced cell viability in breast cancer cell lines in all subtypes tested with IC50s ranging from 0.8-5 uM, similar to what has been reported for other cancer cell types. Unexpectedly, ONC201 did not induce caspase 3 or PARP cleavage, and its toxicity was not inhibited by Z-VAD-FMK, nor by siRNA knockdown of DR4 or DR5. By contrast GST-TRAIL induced caspase 3 and PARP cleavage and GST-TRAIL-induced cell death was inhibited by Z-VAD-FMK and by siRNA knockdown of DR5. Live cell imaging revealed ONC201 induces cell membrane ballooning followed by rupture, whereas GST-TRAIL induced classic apoptosis morphology. Together these results suggest that ONC201 kills breast cancer cells via a caspase-independent, DR4/5-independent mechanism distinct from TRAIL-induced apoptosis. Western blots revealed that ONC201 induces ATF4 and CHOP, consistent with the recently published observations. ONC201 also induced phosphorylation of AMP-dependent kinase (AMPK) in multiple breast cancer cell lines, suggesting that cellular ATP level is decreased by ONC201. ATP depletion by ONC201 was confirmed by direct measurement of cellular ATP. Seahorse XF analysis found that ONC201 inhibited mitochondrial oxygen consumption rate (OCR) but did not inhibit glycolysis as measured by the extracellular acidification rate. Long exposure to ONC201 significantly attenuated OCR, while acute treatment did not inhibit OCR. These data suggest that ONC201 inhibits mitochondrial oxidative phosphorylation via an indirect mechanism. Western blots demonstrated that ONC201 decreases expression of multiple mitochondrial proteins involved in oxidative phosphorylation. Both ONC201-induced toxicity and ATP depletion were enhanced when cells were cultured in non-glucose (galactose) medium. This is consistent with ONC201-induced inhibition of mitochondrial respiration. Supplementing glucose to cells grown in galactose medium partially rescued ONC201-dependent ATP depletion and cell death, and reversed ONC201-induced phospho-eIF2, ATF4 and CHOP induction.

Conclusion: Together, these data demonstrate that ONC201 can kill breast cancer cells by a novel mechanism involving inhibition of mitochondrial respiration.

Citation Format: Greer YE, Gilbert SF, Islam C, Ji Y, Gattinoni L, Stuelten C, Voeller D, Lipkowitz S. ONC201 kills breast cancer cells by inhibiting mitochondrial respiration [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 P3-06-02.

Abstract 4688: HPV+ cervical cancer cells are selectively killed by the combination of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and the cyclin-dependent kinase-9 inhibitor (CDK9i) dinaciclib

Background: Cervical cancer affects more than 520,000 women worldwide yearly, kills over 250,000 and disproportionately affects younger women. With optimal systemic treatment, the median overall survival of patients with metastatic disease is approximately 1.5 years. Previously, a cyclin dependent kinase-9 inhibitor and TRAIL have shown synergistic efficacy in a variety of cancer cell lines in vitro and in vivo. We investigated whether TRAIL combined with dinaciclib (also a CDK9 inhibitor) was selective for HPV+ tumor cells and also explored the mechanisms by which this combination killed HPV+ killed these cells.

Methods: We used a colorimetric MTS assay to assess viability after 24 h of treatment with CDK9i and TRAIL on 3 HPV+ cervical cancer lines (HeLa, SiHa, CaSki) and one HPV- cervical cancer line. Synergy was assessed by the CompuSyn program. The pan-caspase inhibitor ZVAD-FMK was used to evaluate caspase-dependence. Morphological changes were evaluated by light microscopy.

Results: The combination of TRAIL and dinaciclib resulted in greater growth inhibition than either alone in the HPV+ cell lines HeLa, Caski, and Siha. By contrast, TRAIL + dinaciclib did not inhibit the growth of the HPV - cervical cancer cell line C33a more than dinaciclib alone. The growth inhibition by TRAIL + dinaciclib was synergistic in the HPV+ lines but not the HPV- line as calculated by the Combination Index (CompuSyn). Treatment with the pan-caspase inhibitor ZVAD-FMK completely blocked TRAIL-mediated loss of viability and blocked the increased toxicity when TRAIL was added to dinaciclib, but only partially rescued dinaciclib induced loss of viability. When TRAIL and dinaciclib were combined, microscopic analysis was consistent with the synergistic killing of the HPV+ cell lines, but not the HPV- cell line. Morphologically, most cells showed signs of apoptotic cell death due to TRAIL + dincaciclib. However, in 2 HPV+ cell lines (CaSki and Hela) in addition to evidence of shrinkage of some cells with dense nuclei, seen in apoptosis, there was evidence of other cells with cell swelling with heterogeneous nuclei, which can be seen in necroptosis.

Conclusions: Our results demonstrate synergistic killing in HPV+ cells by the combination of TRAIL and dinaciclib. As one HPV- line did not show any effect of TRAIL nor synergistic killing, this is also suggestive of potential HPV selectivity of killing. Dinaciclib induces both caspase-dependent apoptosis, and a non-caspase dependent mechanism of cell death. Direct examination of the cells by light microscopy suggests dinaciclib being associated with apoptosis and necroptosis. TRAIL alone appears to solely cause apoptosis. Future experiments will investigate the mechanisms of cell death and will test these drugs in mouse xenografts.

Citation Format: David S. Kotlyar, Yoshimi E. Greer, Donna Voeller, Lidia Hernandez, Christina M. Annunziata, Stanley Lipkowitz. HPV+ cervical cancer cells are selectively killed by the combination of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and the cyclin-dependent kinase-9 inhibitor (CDK9i) dinaciclib. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4688.

Abstract 4542: Ube2d family members, Ube2e family members and Ube2w modulate the ubiquitination and degradation of EGFR by Cbl

Ubiquitin ligases (E3s) are critical component of ubiquitination. In collaboration with ubiquitin-conjugating enzymes (E2s), E3s confer specificity to the ubiquitination process and direct the conjugation of ubiquitin to one or more lysines on the target proteins. Cbl proteins are RING finger E3s that play a significant role in regulating activity of many tyrosine kinases (e.g., EGFR, MET) by ubiquitination. In our study, we used enzymatic and yeast two-hybrid assays to characterize the E2s that can interact with Cbl proteins. Using an in vitro E3 assay, we found that only the Ube2d family of E2s mediates autoubiquitination of the Cbl proteins. Subsequently, using the yeast two-hybrid system, we found that the three Ube2e family members and Ube2w interact with the RF domain of Cbl. This suggests that Ube2e and Ube2w are relevant to the ubiquitination and degradation of substrates by Cbl. Knockdown of Ube2w decreases ubiquitination of EGFR in Hela cells. In the in vitro E3 assay we found that Ube2w can monoubiquitinate Cbl and increase autoubiquitination of Cbl mediated by ube2d2. Surprisingly, we found that knockdown of Ube2e increases downregulation and ubiquitination of EGFR in HeLa cells. Mechanistically we found that three Ube2e members inhibit autoubiquitination of Cbl mediated by Ube2d2 in vitro. Further, we showed that Ube2e does not affect ubiquitin charging of Ube2d2 by the ubiquitin-activating enzyme (E1) in vitro. This suggests that Ube2e does not compete with Ube2d2 for the E1 under these conditions. Thus, our data suggest that Ube2e acts as a positive modulator of EGFR signaling by competing for Cbl with Ube2d2 and thus prevents ubiquitination and downregulation of the EGFR by Cbl in combination with Ube2d2. Together these data demonstrate that there is an E2 network which modulates the ubiquitination and downregulation of the EGFR by Cbl.

Citation Format: Ke Ma, Philip Ryan, Rachel Klevit, Stanley Lipkowitz. Ube2d family members, Ube2e family members and Ube2w modulate the ubiquitination and degradation of EGFR by Cbl. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4542.

Abstract 3494: MEDI3039, a novel highly potent tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) receptor agonist, induces apoptotic cell death in breast cancer cells

TRAIL receptor agonists are attractive anti-tumor agents because of their capability to induce apoptosis in cancer cells by activating death receptors 4 and 5 (DR4 and DR5) with little toxicity against normal cells. We previously reported that GST-TRAIL efficiently induced cell death in breast cancer cells, particularly mesenchymal triple negative breast cancer (TNBC) - so called basal B breast cancer cells (Rahman et al., Breast Cancer Res Treat. 2009). Recently, a newly developed multivalent TRAIL receptor agonist designed to activate DR5, has been shown to be a TRAIL super-agonist with significantly enhanced potency in multiple cancer cell lines (Swers et al., Mol Cancer Ther. 2013). We hypothesized that MEDI3039, developed by modification of this TRAIL super-agonist, is a potential new therapeutic agent to be used in human breast cancer treatment.

We used 19 human breast cancer cell lines that can be categorized into 4 groups: ER+, HER2 amplified, TNBC basal A and TNBC basal B. MEDI3039- or GST-TRAIL-induced cell death was analyzed by an MTS assay in a 96 well format after 72h of treatment. MEDI3039- or GST-TRAIL-induced caspase activation was measured by Caspase-glo 3/7 assay. Z-VAD-FMK was used as a pan-caspase inhibitor. To verify that MEDI3039 induced apoptosis via DR5, siRNA against DR4 and DR5 were transfected to cells and tested in MTS assay and Western blotting.

MEDI3039 induced cell death in MDA-MB231 (TNBC basal B), and the IC50 was 4.71pM. By contrast, GST-TRAIL induced cell death in this cell line with an IC50 of 624 pM (a 132 fold difference). MEDI3039-induced cell death was completely inhibited by Z-VAD-FMK, indicating that cell death was the result of caspase-mediated apoptotic pathway. Knockdown of DR5, but not DR4, inhibited MEDI3039-induced cell death, demonstrating that MEDI3039-mediated apoptosis requires DR5. MEDI3039 induced cell death in multiple breast cancer cell lines, but the sensitivity varied between cell lines from the four different subtypes. The TNBC basal B group was the most sensitive (avg IC50 = 1.4 pM), the TNBC basal A group was next most sensitive (avg IC50 = 203 pM), the HER2 amplified group was less sensitive (avg IC50 = 314 pM), and the ER+ group was the least sensitive to MEDI3039 (avg IC50 = 403 pM). This relative sensitivity of the different subtypes of breast cancer was similar to what was observed with GST-TRAIL. Importantly, MEDI3039 was at least 2 orders of magnitude more potent compared with GST-TRAIL in most cell lines tested. Drug combination experiments indicated that MEDI3039 has synergistic effect with multiple drugs, including cisplatin and the Wee1 inhibitor MK1775. Data from ongoing animal experiments will be presented. In conclusion, MEDI3039 is a potent TRAIL receptor agonist in breast cancer cells and has potential as a cancer drug in breast cancer patients, especially those with TNBC basal B.

Citation Format: Yoshimi Greer, Sam Gilbert, David Tice, Stanley Lipkowitz. MEDI3039, a novel highly potent tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) receptor agonist, induces apoptotic cell death in breast cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3494.

Abstract 3031: Bufalin regulates Cbl-b levels in HeLa cells through protein synthesis inhibition

Cbl-b is a member of ubiquitin ligases (E3s) family. The major function of CBL family E3s is to negatively regulate signaling through ubiquitination and degradation of receptor tyrosine kinases and kinase associated receptors. Cbl-b plays a crucial role in the regulation of the immune response, as it negatively regulates the costimulatory pathway of CD8 T cells and also suppresses natural killer cell function. Thus Cbl-b down-regulation or inhibition may lead to increased adaptive and innate antitumor immunity and can be used as a treatment strategy for a wide variety of tumors.

Bufalin is a major component of Chan Su, traditional Chinese medicine derived from the toad venom. Bufalin is a C-24 steroid with the wide variety of biological activities, including cardiotonic, anesthetic and antitumor activities. Bufalin has been shown to inhibit growth and induce cell cycle arrest and apoptosis of various cancer cells. Low doses of bufalin can be safely used for prolonged periods of time without severe side effects, while high doses can cause cardiac arrhythmia, seizure and coma.

The purpose of the current study was to investigate if bufalin regulates the levels of Cbl-b and establish the mechanism of Cbl-b regulation. By Western blotting of HeLa cell lysates we found that bufalin decreases protein levels of Cbl-b in a time- and dose-dependent manner without affecting the levels of Cbl. The greatest decrease was observed with 50 nM bufalin after 24 hours treatment. Doses of bufalin as low as 4 nM were effective in Cbl-b down-regulation. Real-time PCR analysis showed 2.9-fold increase in the amount of Cbl-b mRNA upon 50 nM bufalin treatment for 24 hours, suggesting that Cbl-b regulation by bufalin occurs post-transcriptionally. Proteasomal, but not lysosomal inhibitors treatment attenuated the negative effect of bufalin on Cbl-b levels. Co-treatment of HeLa cells with 50 nM bufalin and 50 μg/ml cycloheximide, protein synthesis inhibitor, did not result in any further decrease in Cbl-b levels compared to cycloheximide treatment alone. By measuring the nascent protein synthesis with Click-It metabolic labeling reagents, bufalin was shown to block protein synthesis of the majority of short-lived proteins. These data taken together indicate that bufalin treatment decreases Cbl-b levels in HeLa cells by blocking protein synthesis. We found that 50 nM bufalin treatment for up to 8 hours increased the phosphorylation of eIF2α, translation initiation factor, at Ser51. Phosphorylation of eIF2α known to block translation might explain the effect of bufalin on Cbl-b levels and other short-lived proteins.

To conclude, we found that bufalin increases the phosphorylation of eIF2α, thus leading to the block of translation and decreasing protein levels of Cbl-b in HeLa cells. Our future goal is to test the hypothesis that bufalin activates antitumor immunity through down-regulation of Cbl-b and can thus be used as an antineoplastic agent.

Citation Format: Mariya S. Liyasova, Stanley Lipkowitz. Bufalin regulates Cbl-b levels in HeLa cells through protein synthesis inhibition. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3031.

Mathematical models of breast and ovarian cancers

Women constitute the majority of the aging United States (US) population, and this has substantial implications on cancer population patterns and management practices. Breast cancer is the most common women's malignancy, while ovarian cancer is the most fatal gynecological malignancy in the US. In this review, we focus on these subsets of women's cancers, seen more commonly in postmenopausal and elderly women. In order to systematically investigate the complexity of cancer progression and response to treatment in breast and ovarian malignancies, we assert that integrated mathematical modeling frameworks viewed from a systems biology perspective are needed. Such integrated frameworks could offer innovative contributions to the clinical women's cancers community, as answers to clinical questions cannot always be reached with contemporary clinical and experimental tools. Here, we recapitulate clinically known data regarding the progression and treatment of the breast and ovarian cancers. We compare and contrast the two malignancies whenever possible in order to emphasize areas where substantial contributions could be made by clinically inspired and validated mathematical modeling. We show how current paradigms in the mathematical oncology community focusing on the two malignancies do not make comprehensive use of, nor substantially reflect existing clinical data, and we highlight the modeling areas in most critical need of clinical data integration. We emphasize that the primary goal of any mathematical study of women's cancers should be to address clinically relevant questions. WIREs Syst Biol Med 2016, 8:337-362. doi: 10.1002/wsbm.1343 For further resources related to this article, please visit the WIREs website.

New insights on PI3K/AKT pathway alterations and clinical outcomes in breast cancer

PI3K/AKT signaling pathway plays an important role in tumorigenesis and regulates critical cellular functions including survival, proliferation and metabolism. PIK3CA mutations and AKT activation by phosphorylation (pAKT) are often detected in many cancers and especially at high frequencies in breast cancer. Mounting data suggest that PIK3CA mutations or pAKT are mostly associated with better or insignificant outcomes in estrogen receptor-positive (ER+) early stage breast cancer and tend to be with worse prognosis in ER- disease. pAKT expression has been identified to predict paclitaxel chemotherapy benefit in node-positive breast cancer. Preclinical and neoadjuvant trial data suggest that PIK3CA alterations confer resistance to HER2-targeted therapy and are associated with lower pathological complete response (pCR) rate in HER2-positive breast cancer. However, recent results from randomized clinical trials of adjuvant and metastatic settings show that patients with mutant and wildtype PIK3CA tumors derived similar benefit from anti-HER2 therapy. This article, with our new insights, aims to decipher the mixed data and discusses the influence of the potential confounding factors in the assessments. We also share our views for validation of PI3K/AKT alterations in relation to clinical outcome in the context of specific breast cancer subtypes and treatment modalities towards further advance of the precision medicine for breast cancer treatment.

ONC201: Stressing tumors to death

The small molecule ONC201 was identified in a screen for compounds that would induce expression of the gene encoding tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in tumors and thus cause an autocrine- or paracrine-induced death in tumor cells. Two Research Articles in this issue of Science Signaling by Ishizawa et al. and Kline et al. describe how ONC201 can also trigger cytotoxicity by inducing a stress response. The mechanisms of the stress response induced differ between hematological malignancies and solid tumors, highlighting the complexity of ONC201-induced toxicity and raising intriguing issues of tissue-specific pathways activated by the drug.

Abstract P5-03-06: MEDI3039, a novel highly potent tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL) receptor agonist, induces apoptotic cell death in breast cancer cells

TRAIL receptor agonists are attractive anti-tumor agents because of their capability to induce apoptosis in cancer cells by activating death receptors 4 and 5 (DR4 and DR5) with little toxicity against normal cells. We previously reported that GST-TRAIL efficiently induced cell death in breast cancer cells, particularly mesenchymal triple negative breast cancer (TNBC) – so called basal B breast cancer cells (Rahman et al., Adv. Cancer Res. 2009). Recently, a newly developed multivalent TRAIL receptor agonist designed to activate DR5, has been shown to be a TRAIL super-agonist with significantly enhanced potency in multiple cancer cell lines (Swers et al., Mol Cancer Ther. 2013). We hypothesized that MEDI3039, developed from this TRAIL super-agonist, is a potential new therapeutic agent to be used in human breast cancer treatment.

As model systems, we used 19 breast cancer cell lines that can be categorized into 4 different groups: ER+, HER2 amplified, TNBC basal A and TNBC basal B. MEDI3039- or GST-TRAIL-induced cell death was analyzed by an MTS assay in 96 well format after 72h of treatment. MEDI3039- or GST-TRAIL-induced caspase activation was measured by Caspase-glo 3/7 assay. Z-VAD-FMK was used as a pan-caspase inhibitor. To verify the receptor for MEDI3039, siRNA against DR4 and DR5 were transfected to cells and tested in MTS assay and Western blotting.

MEDI3039 induced cell death in MDA-MB231 (TNBC basal B), and the IC50 was 4.71pM. By contrast, GST-TRAIL induced cell death in this cell line with an IC50 of 624 pM (a 132 fold difference). MEDI3039 and GST-TRAIL induced cell death was completely inhibited by Z-VAD-FMK, indicating that cell death was the result of caspase-mediated apoptotic pathway. Knockdown of DR5, but not DR4, inhibited MEDI3039-induced cell death, demonstrating that MEDI3039-mediated apoptosis requires DR5. MEDI3039 induced cell death in multiple breast cancer cell lines, but the sensitivity varied between cell lines from the four different subtypes. TNBC basal B group was the most sensitive (avg IC50= 1.4 pM), TNBC basal A group was next most sensitive (avg IC50 = 203 pM, HER2 amplified group was less sensitive (avg IC50 = 314 pM), and ER+ group was the least sensitive to MEDI3039 (avg IC50= 403 pM). This was similar to what was observed with GST-TRAIL. Importantly, MEDI3039 was at least 2 orders of magnitude more potent compared with GST-TRAIL in most cell lines tested. Drug combination experiments indicated that MEDI3039 has synergistic effect with multiple drugs, including cisplatin, MK1775. Animal breast cancer xenograft experiments are planned to test the efficacy of MEDI3039 in vivo. Further work to identify biomarker(s) that correlate with MEDI3039 sensitivity, and effective combinations that enhance the toxicity of MEDI3039 especially in the resistant breast cancer subtypes are ongoing. In conclusion, MEDI3039 is a potent TRAIL receptor agonist in breast cancer cells and has potential as a cancer drug in breast cancer patients, especially those with TNBC basal B.

Citation Format: Greer YE, Tice D, Lipkowitz S. MEDI3039, a novel highly potent tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL) receptor agonist, induces apoptotic cell death in breast cancer cells. [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 P5-03-06.

The TRAIL receptor agonist drozitumab targets basal B triple-negative breast cancer cells that express vimentin and Axl

Previously, we found that GST-tagged tumor necrosis factor-related apoptosis inducing ligand preferentially killed triple-negative breast cancer (TNBC) cells with a mesenchymal phenotype by activating death receptor 5 (DR5). The purpose of this study was to explore the sensitivity of breast cancer cell lines to drozitumab, a clinically tested DR5-specific agonist; identify potential biomarkers of drozitumab-sensitive breast cancer cells; and determine if those biomarkers were present in tumors from patients with TNBC. We evaluated viability, caspase activity, and sub-G1 DNA content in drozitumab-treated breast cancer cell lines and we characterized expression of potential biomarkers by immunoblot. Expression levels of vimentin and Axl were then explored in 177 TNBC samples from a publically available cDNA microarray dataset and by immunohistochemistry (IHC) in tumor tissue samples obtained from 53 African-American women with TNBC. Drozitumab-induced apoptosis in mesenchymal TNBC cell lines but not in cell lines from other breast cancer subtypes. The drozitumab-sensitive TNBC cell lines expressed the mesenchymal markers vimentin and Axl. Vimentin and Axl mRNA and protein were expressed in a subset of human TNBC tumors. By IHC, ~15 % of TNBC tumors had vimentin and Axl expression in the top quartile for both. These findings indicate that drozitumab-sensitive mesenchymal TNBC cells express vimentin and Axl, which can be identified in a subset of human TNBC tumors. Thus, vimentin and Axl may be useful to identify TNBC patients who would be most likely to benefit from a DR5 agonist.

Balancing Protein Stability and Activity in Cancer: A New Approach for Identifying Driver Mutations Affecting CBL Ubiquitin Ligase Activation

Oncogenic mutations in the monomeric Casitas B-lineage lymphoma (Cbl) gene have been found in many tumors, but their significance remains largely unknown. Several human c-Cbl (CBL) structures have recently been solved, depicting the protein at different stages of its activation cycle and thus providing mechanistic insight underlying how stability-activity tradeoffs in cancer-related proteins-may influence disease onset and progression. In this study, we computationally modeled the effects of missense cancer mutations on structures representing four stages of the CBL activation cycle to identify driver mutations that affect CBL stability, binding, and activity. We found that recurrent, homozygous, and leukemia-specific mutations had greater destabilizing effects on CBL states than random noncancer mutations. We further tested the ability of these computational models, assessing the changes in CBL stability and its binding to ubiquitin-conjugating enzyme E2, by performing blind CBL-mediated EGFR ubiquitination assays in cells. Experimental CBL ubiquitin ligase activity was in agreement with the predicted changes in CBL stability and, to a lesser extent, with CBL-E2 binding affinity. Two thirds of all experimentally tested mutations affected the ubiquitin ligase activity by either destabilizing CBL or disrupting CBL-E2 binding, whereas about one-third of tested mutations were found to be neutral. Collectively, our findings demonstrate that computational methods incorporating multiple protein conformations and stability and binding affinity evaluations can successfully predict the functional consequences of cancer mutations on protein activity, and provide a proof of concept for mutations in CBL.

Abstract 4965: Multiple ubiquitin-conjugating enzymes modulate the ubiquitination and downregulation of the EGFR by the Cbl RING finger ubiquitin ligase

Receptor tyrosine kinases (RTKs) are known drivers of malignant transformation. Many RTKs (e.g., EGFR, MET) are negatively regulated by ubiquitination and degradation mediated by Cbl proteins, a family of RING finger (RF) ubiquitin ligases (E3s). Loss of Cbl protein function is associated with malignant transformation driven by increased RTK activity. E3s such as the Cbl proteins confer specificity to the ubiquitination process and direct the conjugation of ubiquitin to one or more lysines on the target proteins in collaboration with ubiquitin-conjugating enzymes (E2s). We used enzymatic and yeast two-hybrid assays to characterize the E2s that can interact with Cbl proteins. Using an in vitro E3 assay, we found that only the Ube2d family of E2s mediates autoubiquitination of the Cbl proteins. Subsequently, using the yeast two-hybrid system, we found that Ube2e1, Ube2e2, Ube2e3, Ube2l3, Ube2u, Ube2w and Ube2z can interact with Cbl even though they do not support autoubiquitination of Cbl in the in vitro E3 assay. Among these E2s, three Ube2e family members and Ube2w bind to the RF domain of Cbl as demonstrated by the loss of interaction when the RF domain is disrupted. This suggests that Ube2e and Ube2w are relevant to the ubiquitination and degradation of substrates by Cbl. Knockdown of Ube2w decreases downregulation of EGFR in Hela cells. In the in vitro E3 assay we found that Ube2w can increase autoubiquitination of Cbl mediated by ube2d2. Surprisingly, we found that knockdown of Ube2e increases downregulation and ubiquitination of EGFR in HeLa cells. Mechanistically we found that three Ube2e members inhibit autoubiquitination of Cbl mediated by Ube2d2 in vitro. Further, we showed that Ube2e does not affect ubiquitin charging of Ube2d2 by the ubiquitin-activating enzyme (E1) in vitro. This suggests that Ube2e does not compete with Ube2d2 for the E1 under these conditions. Thus, our data suggest that Ube2e acts as a positive modulator of EGFR signaling by competing for Cbl with Ube2d2 and thus prevents ubiquitination and downregulation of the EGFR by Cbl in combination with Ube2d2. Together these data demonstrate that there is an E2 network which modulates the ubiquitination and downregulation of the EGFR by Cbl.

Citation Format: Ke Ma, Philip Ryan, Rachel Klevit, Stanley Lipkowitz. Multiple ubiquitin-conjugating enzymes modulate the ubiquitination and downregulation of the EGFR by the Cbl RING finger ubiquitin ligase. [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 4965. doi:10.1158/1538-7445.AM2015-4965

Abstract CT326: Pharmacokinetic/pharmacodynamic study of sequence specificity of the PARP inhibitor, olaparib and carboplatin in recurrent women's cancers

Background: Olaparib/carboplatin are active in gBRCA1/2m+ or BRCA-like breast and ovarian cancer (Br/OvCa). Our in vitro data suggest that pretreatment with olaparib before carboplatin attenuates C-induced DNA double stranded breaks (DSBs) and cytotoxicity. We hypothesize olaparib/carboplatin sequence may affect DNA DSBs and toxicity in pts.

Methods: Eligible pts had recurrent women's cancers, normal end-organ function, and evaluable disease. Pts were randomized to arm A or B for intra-pt and inter-cohort analysis of PK/PD endpoints. 21 pts were required per arm for 80% power to determine one SD difference between arms. PBMCs were collected prior to and 24hrs after olaparib or carboplatin on cyc 1&2 for comet DNA damage assay and PAR incorporation ELISA. Toxicity was evaluated q3 wks, and response q2 cyc by RECISTv1.1.

Results: 59 women (age 59 [25-74]; 47 OvCa (26 gBRCAm+)/10 triple negative BrCa [TNBC; 4 gBRCAm+]/1 uterine carcinosarcoma/1 endometrial Ca) were treated. All had prior therapy (median 5[2-14]). Intra-pt comparisons of PD endpoints indicated olaparib/carboplatin yields greater DNA DSBs than olaparib or carboplatin alone (median fold change compared to baseline; 1.21+/- 0.30 SD v. 1.13 or 0.97 [arm A], 1.33 +/- 0.67 SD v. 1.02 or 1.04 [arm B], both p&lt;0.05). Intra-pt and inter-cohort comparisons show no significant differences in DNA DSBs, PAR incorporation and frequencies of Gr3/4 AEs as a function of the order of the schedule. Gr3/4 AEs included neutropenia (22%), anemia (12%), thrombocytopenia (10%), and carboplatin hypersensitivity (3%). Responses (54pts) included 1 CR (2%, 23mo; TNBC) and 23 PR (43%, 9[5-15]mo; 20 OvCa/3 TNBC). gBRCAm+ pts had a higher response rate (RR; 1CR/19 PR) compared to BRCAwt/unknown (4 PR; 65% v. 17%, p&lt;0.001).

Conclusions: Combination O/C induced greater DNA damage than single agents, consistent with the higher than expected RR. However, the O/C sequence did not impact DNA damage, PAR incorporation or toxicity. Olaparib tablets 200mg bid x 7d with carboplatin AUC 4 q 21d is active and tolerable in recurrent women's cancers, especially for gBRCAm+ pts. (NCT01237067)

Treatment schedule armsCycle (cyc) 1Cyc 2Cyc 3-8Cyc 9+Arm AO tablet 200mg bid d1-7⇒C AUC4 d8C AUC4 d1⇒O tablet 200mg bid d2-8O tablet 200mg bid d1-7, C AUC4 d1or2maintenance O tablet 300mg bid

Citation Format: Victoria L. Chiou, Christina Annunziata, Stanley Lipkowitz, Lori Minasian, Nicolas Gordon, Minshu Yu, Seth Steinberg, Nicole Houston, Elise Kohn, Jung-min Lee. Pharmacokinetic/pharmacodynamic study of sequence specificity of the PARP inhibitor, olaparib and carboplatin in recurrent women's cancers. [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 CT326. doi:10.1158/1538-7445.AM2015-CT326