Abstract P2-13-03: Feasibility of generating an external control comparator using RWD by matching with previously conducted RCTs: CDK4/6 Inhibitors for the treatment of Metastatic Breast Cancer

Objectives: Real-world data (RWD) from the clinical care of patients captured through Electronic Health Records (EHRs) is a valuable resource for research. Understanding the relationship between characteristics and outcomes of patients treated in the real world and in oncology clinical trials by producing evaluable trial-like populations from RWD can advance clinical and regulatory knowledge.

Methods: RWD from the Flatiron Health EHR-derived, de-identified, longitudinal database were compared with pooled patient-level data from the three randomized controlled trials (RCTs) supporting regular approval of CDK4/6 inhibitors for patients with previously untreated hormone receptor-positive, HER- metastatic breast cancer (mBC). The RCT group included patients who received aromatase inhibitor (AI) monotherapy (RCT-control), and an experimental group (RCT-experimental) that received a cyclin dependent kinase 4/6 (CDK4/6) inhibitor + AI. The real-world control group (rwCG) of patients initiating AI monotherapy was selected using the key eligibility criteria across the RCTs. Patients from the rwCG were matched to the RCT-control and the RCT-experimental patients, respectively. Matching (1:1) was performed through the propensity score (PS) method adjusting for baseline covariates of age, race, site of disease, ECOG PS, and metastatic disease (recurrent, De novo). Multiple imputation (MI) was adopted to impute missing ECOG PS in the rwCG due to the high percentage of missingness. Progression-free survival (PFS) and overall survival (OS) were analyzed for the following groups: A) rwCG and RCT- control B) rwCG and RCT-experimental and C) RCT-control and RCT-experimental. To assess the feasibility of RCT control arm replication, we assessed whether the trial replication hazard ratio (HR) estimates from analysis B were within the published trial estimates’ 95% confidence intervals (CIs). HR and their 95% CIs were estimated using Cox proportional hazard model.

Results: A total of 1292 patients were selected from the EHR-derived database to comprise the rwCG and 1827 patients were pooled across the RCTs (1106 for RCT-experimental and 721 patients for RCT-control). With MI, 520 rwCG patients were matched to the RCT-control for analysis A, and 658 rwCG patients were matched to the RCT-experimental for analysis B. The results are summarized in Table 1. The point estimate of the PFS HR comparing the rwCG to the RCT-experimental was within the 95% CIs for three RCTs. For OS, the point estimate of the HR was within the 95% CI for MONALESSA-2 but not for PALOMA-2.

Conclusion: PFS and OS appeared longer in the RCT-control than in the rwCG, and the difference was more pronounced in OS. While it appears that there is greater similarity for PFS than for OS based on the results of the matched analysis of RCT- experimental vs. rwCG, evaluation of PFS results are limited by substantial differences in assessment and outcome definitions for progression between RCT-control (RECIST) and rwCG. Despite PS matching, there are apparent differences between patients treated in RCTs and routine practice, highlighting the importance of clinical setting, trial selection, study design, and use of randomization. There are still outstanding feasibility questions on the evaluation of OS and further research is required to understand factors potentially impacting the outcomes between RCTs and RWD.

Table 1: Estimated Treatment Effects in PFS and OS, rwCG vs RCT-control vs RCT-experimental

Citation Format: Christy Osgood, Jiaxin Fan, Xin Gao, Catherine Keane, Jonathan Bryan, James P. Roose, Erik Bloomquist, Aracelis Torres, Shrujal Baxi, Nathan Nussbaum, Fatima Rizvi, Shenghui Tang, Irene Nunes, Julia Beaver, Donna R. Rivera, Lynn Howie, Prashni Paliwal, Laleh Amiri-Kordestani. Feasibility of generating an external control comparator using RWD by matching with previously conducted RCTs: CDK4/6 Inhibitors for the treatment of Metastatic Breast Cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-13-03.

US Food and Drug Administration Approval Summary: Fam-Trastuzumab Deruxtecan-nxki for Human Epidermal Growth Factor Receptor 2-Low Unresectable or Metastatic Breast Cancer

PURPOSE

The US Food and Drug Administration approved fam-trastuzumab deruxtecan-nxki (DS-8201a, T-DXd) for the treatment of adult patients with unresectable or metastatic human epidermal growth factor receptor 2 (HER2)-low (immunohistochemistry 1 + or immunohistochemistry 2+/in situ hybridization-) breast cancer who have received a prior chemotherapy in the metastatic setting or developed disease recurrence during or within 6 months of completing adjuvant chemotherapy.

PATIENTS AND METHODS

Approval was based on DESTINY-Breast04, a phase III, randomized, open-label, multicenter trial in patients with unresectable or metastatic HER2-low breast cancer, determined at a central laboratory. A total of 557 patients were randomly assigned (2:1) to receive either T-DXd 5.4 mg/kg intravenously once every 3 weeks (n = 373) or physicians' choice of chemotherapy (n = 184).

RESULTS

The study met its primary efficacy end point of progression-free survival (PFS) by blinded independent central review assessment in the hormone receptor-positive (HR+) cohort (N = 494) with an estimated hazard ratio (HR) of 0.51(95% CI, 0.40 to 0.64; P < .0001). Key secondary end points were also met, including PFS in the intent-to-treat population with an HR of 0.50 (95% CI, 0.40 to 0.63; P < .0001), overall survival (OS) in the HR+ cohort with an HR of 0.64 (95% CI, 0.48 to 0.86; P = .0028) and OS in the intent-to-treat with an HR of 0.64 (95% CI, 0.49 to 0.84; P = .0010). The safety profile of T-DXd was consistent with previously approved indications, and no new safety signals were observed in this study population.

CONCLUSION

The approval of T-DXd in HER2-low metastatic breast cancer was based on statistically significant and clinically meaningful PFS and OS improvements observed in the DESTINY-Breast04 trial and represents the first approved therapy specifically for the treatment of HER2-low metastatic breast cancer.

Postmarketing Colitis Cases Associated With Alpelisib Use Reported to the US Food and Drug Administration

This case series investigates reports of 20 patients with colitis temporally associated with alpelisib use.

Updated FDA pooled analysis of pain medication use in trial participants with HR+, HER2-negative metastatic breast cancer treated with endocrine therapy and a CDK 4/6 inhibitor

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Background: Pain medications (PMs) are commonly used to treat pain in patients with advanced or metastatic breast cancer (MBC). We previously reported an initial analysis of PM prescribing patterns in clinical trial participants with breast cancer receiving CDK 4/6 inhibitor (CDKI)-based treatment. We present an updated analysis here. Methods: We pooled data from 7 randomized controlled trials of CDKI + endocrine therapy (ET) in patients with HR+, HER2-negative MBC. All analyzed patients received at least 1 dose of CDKI/placebo+ET and a concomitant PM with a documented start date. Medications administered during hospitalizations were not included. We looked at PM use in all patients, patients who took PM only before or after the trial started, and those who took PM both before and during the trial. PMs were categorized as opioid (includes codeine-containing), NSAIDS, or other (i.e. bone-directed, antiepileptic, topical PMs). Results: 4200 patients enrolled across the 7 trials who received at least one dose of CDKI/placebo+ET (n = 2616 CDKI, n = 1548 placebo). Of these, 2881 took a PM at any time (n = 1774 CDKI, n = 1107 placebo). Of the 1774 patients who received CDKI+ET, 487 (27%) took at least one opioid and one NSAID at any time, 782 (44%) took at least one NSAID at any time but no opioids, 244 (14%) took at least one opioid at any time but no NSAIDs, and 261 (15%) took only PM that were not opioids or NSAIDs. Of the 1107 patients who received placebo+ET, 297 (27%) took at least one opioid and one NSAID at any time, 490 (44%) took at least one NSAID at any time but no opioids, 153 (14%) took at least one opioid at any time but no NSAIDS, and 167 (15%) took only PM that were not opioids or NSAIDs. Of the 2881 patients who took a PM at any time, 2038 patients (n = 1222 CDKI, n = 816 placebo) had documented start for their PM. Of these, 544 took PM only before the trial started (n = 334 CDKI, n = 210 placebo), 915 took a PM only during the trial (n = 551 CDKI, n = 364 placebo), and 579 took a PM both before and during the trial (n = 337 CDKI, n = 242 placebo). Overall, more patients took NSAIDs only compared to opioids only. Patient characteristics at baseline were balanced between the two arms. Conclusions: Overall, PM prescribing patterns were similar between the arms. NSAID use was higher than opiates in all groups. These findings are hypothesis generating and additional research is needed to determine the impact of PM on participants’ pain and physical function. Further research should include an understanding of the duration of PM needed in patients with MBC.

Abstract P2-11-05: Generating real-world external comparators for randomized clinical trials (RCTs) in metastatic breast cancer (mBC) using electronic health records (EHRs)

Objectives: Real-world data (RWD) from the routine care of patients with cancer captured through EHRs is a valuable resource for research. Understanding the relationship between characteristics and outcomes of patients treated in the real world and those treated in clinical trials is essential to produce evaluable trial-like populations using RWD in oncology for research and regulatory purposes. Methods: This study used: a) RWD from the Flatiron Health EHR-derived, de-identified, longitudinal database (comprising patient-level structured and unstructured data, curated via technology-enabled abstraction selected from approximately 280 US cancer clinics [~800 sites of care]) and b) patient-level data from three completed RCTs (PALOMA-2, MONALEESA-2, and MONARCH-3) including patients with previously untreated hormone receptor positive (HR+), HER2/neu negative (HER2-) mBC, then separately pooled across the trials into two treatment groups, patients who received aromatase inhibitor monotherapy (AI) or a CDK4/6 inhibitor + AI. Key eligibility criteria were similar across the RCTs and were used to select a real world external cohort (rwEC) initiating AI monotherapy on or prior to 11 Nov 2015 (end of MONARCH-3 enrollment period). Patients from the rwEC were matched separately to the control arm and experimental arm patients from the pooled RCT using propensity score method (PSM). The propensity score was estimated by a logistic regression using baseline covariates of age, race, site of disease (visceral, non-visceral), Eastern Cooperative Oncology Group Performance Status (ECOG PS) (0, 1), and metastatic disease (recurrent, new). The matching ratio was 1:1 without replacement with calipers. Covariate balance was measured by the absolute standardized mean difference (ASMD). Due to the high percentage of missing ECOG PS data, matching was repeated 100 times with imputed ECOG PS. The impact of including additional key covariates for propensity matching such as number of disease sites, bone-only disease, and prior endocrine therapy was assessed. Results: There were 1326 patients with HR+, HER2- mBC selected from the EHR-derived database who received first-line AI therapy and 1827 patients randomized in the RCTs (1106 and 721 patients for experimental and control arms, respectively). With 100 matching iterations, 563 rwEC patients on average (range, 547-572) were matched to the RCTs control arm, and 753 rwEC patients on average (range: 741-761) were matched to the RCTs experimental arm. Prior to matching, the ASMD varied widely across all prespecified baseline covariates (4.3 for the rwEC vs. RCTs control arm, 2.6 for the rwEC vs. RCTs experimental arm). After matching was performed, across all baseline covariates used in the PSM, the ASMD was reduced to be under 0.12 for the rwEC vs. RCTs control arm, and under 0.2 for the rwEC vs. RCTs experimental arm in more than 90% of the matching iterations. Analyses looking at the additional baseline covariates to the propensity matching resulted in similar ASMDs. Conclusions: EHR-derived RWD can be used to generate a cohort of patients with similar baseline characteristics to those treated on RCT. The next step in our trial emulation framework is to analyze the comparability of outcomes between these two matched cohorts.

Citation Format: Laleh Amiri-Kordestani, Xin Gao, Shrujal Baxi, Erik Bloomquist, Jonathan Bryan, Lynn Howie, Catherine Keane, Paul G. Kluetz, Christy Osgood, Prashni Paliwal, Donna R. Rivera, James Roose, Julie Schneider, Harpreet Singh, Shenghui Tang, Lijun Zhang, Julia A. Beaver. Generating real-world external comparators for randomized clinical trials (RCTs) in metastatic breast cancer (mBC) using electronic health records (EHRs) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-11-05.

FDA Approval Summary: Abemaciclib With Endocrine Therapy for High-Risk Early Breast Cancer

PURPOSE

The US Food and Drug Administration approved abemaciclib in combination with endocrine therapy (ET) for the adjuvant treatment of adult patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative, node-positive, early breast cancer (EBC) at high risk of recurrence and a Ki-67 score ≥ 20%.

PATIENTS AND METHODS

The approval was based on monarchE, a phase III, open-label, 2-cohort, multicenter trial of patients with EBC randomly assigned to receive abemaciclib plus ET (n = 2,808) or ET alone (n = 2,829). Abemaciclib was given at 150 mg orally twice daily for 2 years.

RESULTS

Invasive disease-free survival (IDFS) in the intent-to-treat population was statistically significant at the second IDFS interim analysis (IA; March 2020; hazard ratio [HR; 95% CI], 0.747 [0.598 to 0.932]; P = .0096); however, only 12.5% of patients had completed adjuvant therapy, and the HR for overall survival (OS) was > 1. A prespecified, controlled analysis of IDFS in patients with Ki-67 ≥ 20% in cohort 1 was statistically significant at the final IDFS analysis (July 2020; HR [95% CI], 0.643 [0.475 to 0.872]; P = .0042). At the first OS IA (April 2021), the majority of patients had completed adjuvant therapy, IDFS remained consistent, and potential detriment in OS was not observed for this subgroup (HR [95% CI], 0.767 [0.511 to 1.152]). The HR for OS in the intent-to-treat population at OS IA remained > 1 (HR [95% CI], 1.091 [0.818 to 1.455]). More patients in the abemaciclib plus ET arm experienced treatment emergent adverse events (all grades 98.4% v 88.8%, grade 3 ≥ 49.7% v 16.3%).

CONCLUSION

The approval of abemaciclib in adjuvant EBC was limited to patients with high risk of recurrence and Ki-67 ≥ 20%, given their favorable benefit:risk with a statistically significant IDFS advantage and no observed detriment on survival.

Overall survival in patients with breast cancer treated with a CDK 4/6 inhibitor plus fulvestrant: A U.S. Food and Drug Administration pooled analysis

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JJG, JC, TMP contributed equally. JAB, LAK contributed equally. Background: Cyclin dependent kinase 4/6 inhibitors (CDKIs) are oral targeted agents approved for use in combination with endocrine therapy as first or secondline treatment of hormone-receptor positive (HR+), human epidermal growth factor receptor 2 (HER2)-negative advanced or metastatic breast cancer. We previously reported the pooled analyses of progression-free survival of patients in certain clinicopathologic subgroups, and results showed a consistent benefit from the addition of a CDKI to endocrine therapy. Here, we report the pooled overall survival (OS) results in patients treated with a CDKI plus fulvestrant. Methods: We pooled individual patient data (n=1948) from three phase III randomized breast cancer trials of a CDKI plus fulvestrant submitted to the FDA in support of marketing applications. All analyzed patients received at least one dose of a CDKI or placebo, plus fulvestrant. The median OS was estimated using Kaplan-Meier (KM) methods, and hazard ratios (HR) with corresponding 95% confidence intervals (CIs) were estimated using Cox regression models. Results: Results of OS analyses, including all pooled patients, patients treated in the first-line setting, and patients treated in the second line and later settings, are summarized in the table below. Additional subgroup analyses of OS by progesterone receptor status, site of metastases, breast cancer histology, ECOG performance status, race, and de novo metastatic presentation all favored adding a CDKI to fulvestrant. In patients age < 40, the estimated OS HR favored fulvestrant alone, but this subgroup had a small sample size (n=89), so this result must be interpreted with caution. All results are considered exploratory and hypothesis-generating. Conclusions: Addition of CDKIs to fulvestrant appears to confer a consistent survival benefit across all pooled patients and within most clinicopathological subgroups of interest.[Table: see text]

Pain medication use in patients with HR+, HER2-neg advanced breast cancer treated with endocrine therapy and a CDK 4/6 inhibitor: A U.S. FDA pooled analysis

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Background: Pain medications (PMs) are commonly used to treat pain in patients (pts) with advanced/metastatic breast cancer (MBC). We examined PM usage patterns in pts receiving CDK 4/6 inhibitor (CDKI) based treatment. Methods: We pooled data from seven phase 3 randomized, controlled trials of CDKI + endocrine therapy in pts with hormone receptor positive, human epidermal growth factor receptor-2 negative MBC. PM were categorized as opioid (includes codeine-containing), NSAID, or other (i.e. bone-directed, antiepileptic, topical PMs). All analyzed pts received at least 1 dose of CDKI/placebo and had concomitant PM with a documented start date. Medications prescribed during hospitalizations were not included. We evaluated percent PM by demographic factors and pts with bone mets, and liver/lung mets. Results: 2416 pts met the inclusion criteria, of which 928 pts started a PM before the study and 1488 pts did not start PM before the study. Of the 1488 pts not on a PM before the study, 739 started a PM after study started, and 749 did not receive any PM at any time. Of the 739 pts who started a PM only after study start, overall, 59% were prescribed only an NSAID, 10% were prescribed only opioid, 17% were prescribed both an NSAID and opioid, and 14% were prescribed other PMs. The PM use by percent in demographic subgroups in the 1488 pts who took none or more PMs only after study start are presented in the table. Conclusions: To our knowledge, this is the first analysis of PM usage patterns in pts with MBC receiving CDKI or placebo with hormonal therapy on clinical trials. NSAID use was higher than opiates in all prespecified subgroups. Future analyses will examine the benefit of different classes of pain medications in treating symptoms of pain and whether there are differences between study treatment arms Percent PM Use by Class (Patients Who Took None or More PM Only After Study Start). [Table: see text]

Patient-reported pain and pain medication impact in patients with HR+ Her2-neg advanced breast cancer: A U.S. FDA pooled analysis

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Background: Despite the ubiquitous prescribing of pain medications (PMs) in cancer clinical trials, the impact of such prescribing patterns and reporting on the experience of pain is not often investigated. We examined patient-reported pain before initiation of PM reporting and at the next available pain assessment. Our aim was to understand change in patient-reported pain. Methods: We pooled data from 7 phase 3 randomized, controlled, registration trials of CDKI with endocrine therapy in patients with hormone receptor positive, human epidermal growth factor receptor-2 negative MBC. We restricted our analyses to patients who started therapy with no PM reported and looked at patients who had NSAID or opioid medication documented. We calculated change between 2 assessments in patient-reported pain before and after PM using the pain occurrence item (Q9) on the EORTC Quality of Life questionnaire (QLQ-C30). Results: Of the 4200 patients who received at least 1 dose of CDKI/placebo, 1488 started with no documented PM, with 48% reporting none at all when asked about pain at baseline. Subsequently, 185 patients had documented NSAID and 43 an opioid and had a pain PRO assessment before and after. NSAIDs documentation occurred on average 11 weeks into trial and opioids 5. Before documentation of NSAIDs, 45% of patients reported no pain compared to 23% of patients with an opioid. Patients who had documented NSAIDs, 29% experienced an improvement in their self-reported pain, whereas 32% of patients with documented opioids improved. On average the time between the 2 pain assessments was around 58 days for both PMs. Conclusions: In this analysis in patients who had a pain assessment before and after documentation of a PM, there is a small group whose pain improved. It is important to note that patients’ response to the pain item was not provided to the clinical care team, which may explain why there may have been suboptimal pain control. Further study is needed to examine how pain management can be achieved in patients with advanced breast cancer. Future analysis should be performed with patients whose PRO pain results are communicated with the clinical care team in real-time. [Table: see text]

FDA analysis of depth of response (DpR) and survival across 10 randomized controlled trials in patients with previously untreated unresectable or metastatic melanoma (UMM) by therapy type

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Background: Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 may not capture the full spectrum of benefit that patients with melanoma derive from targeted kinase inhibitors (TKI) or immunotherapies. We explored the relationship between DpR and overall survival (OS) in patients treated with TKI (BRAF, MEK inhibitors), immunotherapy (antibodies targeting PD-1 or CTLA-4), or chemotherapy (dacarbazine or paclitaxel). Methods: Ten randomized controlled trials of patients with previously untreated UMM were pooled and evaluated by type of therapy. DpR was grouped by maximal tumor shrinkage (G0 = no shrinkage or increase, G1 = ≤25%, G2 = 26-50%, G3 = 51-75%, G4 = 76- < 100%, and G5 = 100%). We performed an exploratory analysis evaluating the association between DpR and OS using hazard ratios (HR) generated from a Cox proportional hazards model where maximal tumor shrinkage category was included as a time varying covariate. Results: There were 3778 patients evaluable for tumor response. The table displays the HR for OS by DpR group and therapy type. Estimated OS at 24m in patients with deep response ( > 75%; G4+G5) treated with TKI and immunotherapy was 69% and 92%, respectively, although many patients were censored. Conclusions: For patients with previously untreated UMM a larger DpR correlates with a longer OS, regardless of therapy type. Deep response ( > 75%) is associated with a high rate of estimated OS at 24 months in patients treated with immunotherapy. Analysis of DpR provides additional granularity of response data and may provide a more nuanced prediction of clinical outcome. [Table: see text]

Model-informed drug development approach supporting approval of the 4-week (Q4W) dosing schedule for nivolumab (Opdivo) across multiple indications: a regulatory perspective

BACKGROUND

A nivolumab dosage regimen of 480 mg intravenously (i.v.) every 4 weeks (Q4W) was approved by FDA for the majority of the approved indications for nivolumab.

METHODS

The proposed new dosage regimen was supported by pharmacokinetic modeling and simulation, dose/exposure-response relationships for efficacy and safety in the indicated patient populations, and the clinical safety data with the 480 mg Q4W dosage regimen. Pharmacokinetic exposures achieved with 480 mg Q4W were predicted for 4166 patients in 21 clinical studies with various types of solid and hematological tumors. Exposure-response analyses were conducted to predict 480 mg Q4W safety and efficacy across all FDA-approved indications for nivolumab.

RESULTS

For the overall population, the geometric mean exposure achieved with 480 mg i.v. Q4W was 5.2% higher for steady state Cavg and 15.6% lower for Ctrough than those with 3 mg/kg i.v. Q2W, the approved dosage regimen. The simulated concentration-time course achieved with 480 mg Q4W regimen was below the median concentration achieved with 10 mg/kg i.v. Q2W that was also studied in clinical trials. The predicted probability of adverse events was similar between 480 mg Q4W and that observed with the 3 mg/kg Q2W regimen. Efficacy results were found to be similar between Q2W and Q3W dosage regimens in patients with renal cell carcinoma. The predicted efficacy for each indication suggested that the efficacy with 480 mg Q4W is unlikely to be compromised compared with that observed with 3 mg/kg Q2W.

CONCLUSIONS

The model-informed analyses of predicted exposure, efficacy and safety based on data from extensive clinical experience with nivolumab suggest that the benefit-risk profile of 480 mg Q4W regimen is comparable to the approved 3 mg/kg Q2W regimen, thus providing the regulatory basis for the approval of 480 mg Q4W regimen in the absence of clinical efficacy data with this new dosage regimen.

Abstract 1612: Identification of mithramycin analogs with improved targeting of the EWS/FLI1 transcription factor

Background: Ewing sarcoma is a bone a soft tissue sarcoma with a poor overall survival. This tumor absolutely depends on the continued expression of the EWS-FLI1 transcription factor for cell survival. We are therefore focused on developing small molecules that inhibit EWS-FLI1. We have previously completed a high throughput screen that identified mithramycin as an inhibitor of EWS-FLI1 and translated this compound to the clinic in a phase I-II trial. The success of this compound in the clinic has been challenged by drug associated liver toxicity that has necessitated dose reductions. Therefore the goal of this study is to identify less toxic and-or more potent mithramycin analogs.

Methods: The less toxic analog, EC8042, was identified by evaluating animal toxicity data and serum pharmacokinetics in mice and rats. In order to identify a more potent compound, a panel of more than 20 mithramycin analogs was screened using an EWS-FLI1 reporter NR0B1 luciferase construct to identify EC8105. EWS-FLI1 suppression was confirmed using quantitative PCR and western blot analysis in vitro. The ability of the drug to block EWS-FLI1 binding to chromatin was evaluated by performing chromatin immunoprecipitation in the presence and absence of drug. The relative hepatotoxicity of the analogs was modeled in vitro by comparing doses that achieve suppression of EWS-FLI1 to toxic doses of the drug in HepG2 cells and confirmed in vivo in xenograft experiments. Finally, we tested the ability of both analogs to suppress tumor growth in xenograft models of Ewing sarcoma and confirmed suppression of EWS-FLI1 using immunofluorescence of formalin fixed tissue from these experiments.

Results: EC8042 shows equivalent suppression of EWS-FLI1 activity but is substantially less toxic than the parent compound, allowing higher serum levels of drug in vivo in animal models. In contrast, EC8105 is approximately 8 times more potent than the parent compound and demonstrates improved suppression of the EWS-FLI1 gene signature. Both compounds work to block EWS-FLI1 binding to chromatin. More importantly, in contrast to mithramycin, both analogs suppress EWS-FLI1 activity at concentrations that are non-toxic to HepG2 cells. These effects translate into improved suppression of Ewing sarcoma xenograft growth with a corresponding increase in mouse survival and regression of several tumors in both cohorts.

Conclusions: We have identified the mithramycin analogs EC8042 and EC8105 as EWS-FLI1 inhibitors. These compounds are less toxic and more potent than the parent compound and suppress EWS-FLI1 at concentrations that do not appear to cause liver toxicity. Together these results suggest that the clinical development of these analogs is warranted.

Citation Format: Christy Osgood, Nichole Maloney, Christopher G. Kidd, Meti Gebregiorgis, Luz E. Nunez, Javier Gonzalez-Sabin, Lee J. Helman, Francisco Moris, Patrick J. Grohar. Identification of mithramycin analogs with improved targeting of the EWS/FLI1 transcription factor. [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 1612. doi:10.1158/1538-7445.AM2015-1612

Dichloroacetonitrile, a by-product of water chlorination, induces aneuploidy in Drosophila

Nitriles have been shown to be potent inducers of aneuploidy in yeast and Drosophila test systems. Haloacetonitriles are by-products of water chlorination that have been shown to be mutagenic and carcinogenic following topical application. In this report we show that dichloroacetonitrile, but not dibromoacetonitrile, is an effective inducer of aneuploidy in oocytes of Drosophila melanogaster. Following inhalation exposure of ZESTE adult females, dichloroacetonitrile (8.6 ppm) induced highly significant increments in the frequencies of sex chromosome loss and gain. Sodium cyanide was also found to be a highly effective inducer of germline aneuploidy, suggesting that cyanide toxicity may contribute to potency of nitriles as inducers of aneuploidy.

Chrysotile and amosite asbestos induce germ-line aneuploidy in Drosophila

Asbestos toxicity is a problem of considerable public concern and debate, however little is known regarding the biological targets of asbestos fibers. Prompted by reports that asbestos induces aneuploidy in cultured mammalian cells, we have investigated whether asbestos induces germ-line aneuploidy in Drosophila melanogaster. Using the ZESTE genetic test system, we have shown that both chrysotile and amosite asbestos induce sex-chromosome aneuploidy in Drosophila oocytes. Chrysotile appeared to be the more effective agent because it induced approximately equal frequencies of chromosome gain and chromosome loss, while amosite induced chromosome loss only. Two other asbestiform minerals, crocidolite and tremolite, were ineffective in this assay system. These results suggest that possible germ-line effects of asbestos should be considered in evaluating its potential impact on human health.

Aneuploidy in Drosophila, II. Further validation of the FIX and ZESTE genetic test systems employing female Drosophila melanogaster

Two sensitive genetic systems for the detection of germline aneuploidy employing Drosophila melanogaster females were described in the first paper of this series (Zimmering et al., submitted to Mutation Research). Designated FIX and ZESTE, these systems permit the rapid and efficient detection of exceptional offspring derived from aneuploid female germ cells. The current report presents test results from a survey of 8 additional chemicals that have been analyzed in both systems. The tested chemicals include: acetonitrile, cadmium chloride, carbendazim, dimethylsulfoxide (DMSO), methylmercury(II) chloride, methoxyethyl acetate, propionitrile and water. Excluding the negative control, water, only the fungicide carbendazim failed to induce aneuploidy in either test system. Of the remaining 6 chemicals one, methylmercury(II) chloride, was positive in the FIX system but not in ZESTE, while MEA was positive in ZESTE and borderline in FIX. The results provide little evidence of germ-cell stage specificity of response to the tested chemicals. Comparison of the induced rates of aneuploidy i indicates that these can exhibit departures from simple additivity to the spontaneous rates: induced rates in the ZESTE system are generally higher and more variable than those from FIX. Possible reasons for the difference in responsiveness between FIX and ZESTE flies are discussed as is the question of the classification of those chemicals which induce chromosome loss events but not chromosome gains.

Aneuploidy in Drosophila, IV. Inhalation studies on the induction of aneuploidy by nitriles

The Drosophila ZESTE system was used to monitor the induction of sex chromosome aneuploidy following inhalation exposure of adult females to four nitriles: acetonitrile, propionitrile, acrylonitrile and fumaronitrile. Acetonitrile and propionitrile were highly effective aneuploidogens, inducing both chromosome loss and chromosome gain following brief exposures to low concentrations of these chemicals, and these nitriles also induced rapid paralysis. Acrylonitrile-induced chromosome loss only but did not induce paralysis. Fumaronitrile, in contrast with the results reported in yeast, was ineffective in inducing chromosome loss or gain. Virtually all exceptional offspring induced by acetonitrile and propionitrile were recovered in the first sampled eggs, corresponding to treated mature oocytes. Additionally, the time interval between treatment and sampling was shown to be important, suggesting rapid loss or detoxification of the nitriles. Genetic analysis demonstrated that most aneuploids resulted from induced segregation errors during the first division of meiosis. Cold treatments were found to be ineffective in enhancing the effects of acetonitrile, suggesting important differences between the Drosophila and yeast aneuploidy detection systems. Possible mechanisms by which nitriles may disrupt chromosome segregation in Drosophila oocytes are considered.

Aneuploidy in Drosophila, I. Genetic test systems in the female Drosophila melanogaster for the rapid detection of chemically induced chromosome gain and chromosome loss

An account is provided of two genetic schemes in the Drosophila melanogaster female designed as rapid detectors of chemically induced aneuploidy, including both chromosome gain and chromosome loss. One scheme is referred to as FIX, in which the female carried free (heterozygously) inverted X (chromosomes) and the other, ZESTE, where females do not carry inversions and the X-linked sexually dimorphic zeste mutation plays the key role in the detection of aneuploid offspring. The principle attribute of the FIX system is that all euploid offspring are wild-type for body and eye color whereas aneuploid females have a yellow body and aneuploid males white eyes; int he ZESTE system all euploid individuals are wild-type for eye color, aneuploid females possess zeste-colored eyes and aneuploid males white eyes. In addition induced polyploidies (2X:2A gametes) appear as yellow and zeste male intersexes in the FIX and ZESTE systems, respectively. In this way all aneuploids are recognized immediately. Consequently, detection of compounds with weak effects requiring large sample sizes may be made in a fraction of the time associated with more traditional schemes for aneuploidy detection in Drosophila.

Current status of aneuploidy testing in Drosophila

Based on the literature on file at EMIC, 181 papers contained material on aneuploidy testing. Initial screening rejected papers providing no data, no negative control and/or poorly designed genetic schemes; 67 papers representing tests of 76 compounds were reported on. Statistical classifications were established as follows: (+)=a statistically significant difference at the 5% level between the treated and control frequencies; (-)=no significant difference at the 5% level when the number of offspring tested was sufficient to have identified an increase of 0.2% over the control with a power of 75%; I=inconclusive= (a) no significant difference at the 5% level but the number of offspring tested was below that necessary to detect an increase of 0.2% with a power of 75%; (b) the nature of apparent complete loss is undetermined; or (c) the nature of the germ cells sampled is not determined. Of the 76 compounds analyzed, calls were made on 34 compounds. 17/34 compounds were positive for chromosome gain (11/34 for chromosome gain and chromosome loss, 6/34 for chromosome gain only). 17/34 compounds were negative for chromosome gain (11/34 for chromosome gain and chromosome loss and 6 for chromosome gain only). Are any fo the compounds found to induce aneuploidy specific for aneuploid induction? 7 or the compounds positive for chromosome gain were positive in one or more tests assaying for other genetic endpoints, and no reliable data exists regarding results in other tests for the remaining 10 compounds; accordingly, the answer to the question awaits further work.

Evidence for an increase in X-ray-induced translocation frequency in oocytes of caffeine-treated Drosophila females

0-8 h old Drosophila females carrying a reversed metacentric X chromosome and a suitably marked Y chromosome were treated or not with 0.2% caffeine and irradiated with 2000 R X-rays. In contrast with the reduction found in translocation frequency following 2000 R irradiation of the male mated with 0.2% caffeine-treated females, the frequency of interchanges in oocytes was significantly higher with caffeine as compared with controls.

Effects of caffeine on maternal repair systems in Drosophila melanogaster. Concentration-dependent reversals of the effects of caffeine on chromosome loss and autosome-autosome translocations induced by x-rays in the paternal genome

Drosophila melanogaster females were treated with 1% caffeine, mated with X-rayed males and the frequencies of induced sex-chromosome loss, translocations between the major autosomes and between the Y-chromosome and the major autosomes determined. In a reversal of the results obtained previously with 0.2% caffeine by Mendelson and Sobels, treatment of females with 1% caffeine led to a decrease in sex-chromosome loss, confirming preliminary data of Zimmering and Osgood and an increase in autosome--autosome translocations. It is suggested that the higher concentration of caffeine inhibits replication permitting more time available for chromosome-type restitutions by means of caffeine-insensitive repair mechanisms. In contrast with results for autosome--autosome translocation, the frequency of Y-autosome translocations was depressed below controls suggesting an isolation (by any one of several means) of Y-chromosome breaks from those in the autosomes.

Fracture-dislocation of the cervical spine with ankylosing spondylitis. Report of two cases

✓ Two cases of cervical fracture-dislocation causing neurological deficits in patients with ankylosing spondylitis are presented. Review of the literature shows that these patients have a higher incidence of neurological deficits (70%) than comparable patients without ankylosing spondylitis (44%). Predisposing factors and treatment are discussed.