Can a propensity score matching method be applied to assessing efficacy from single-arm proof-of-concept trials in oncology?

As a result of the escalating number of new cancer treatments being developed and competition among pharmaceutical companies, decisions regarding how to proceed with phase III trials are frequently based on findings from either single-arm phase I expansion cohorts or phase II studies that compare the efficacy of the study drug to a standard-of-care benchmark derived from historical data. However, even when eligibility criteria are matched, differences in the distribution of baseline patient features may influence the outcome of single-arm trials in real-world scenarios. Therefore, novel methods are needed to enhance the accuracy of efficacy prediction from current cohorts relative to historical data. In this study, we demonstrated the feasibility of using the propensity score matching (PSM) method to improve decision making by matching relevant baseline features between current and historical cohorts. According to our findings, utilizing the PSM method may provide a less biased means of comparing outcomes between current and historical cohorts relative to a naïve approach, which relies solely on differences in average outcomes between the cohorts.

Improving the solubility of pseudo-hydrophobic Alzheimer's Disease medicinal chemicals through co-crystal formulation

Natural products are ligands and potential inhibitors of Alzheimer's disease (AD) tau. Dihydromyricetin (DHM) is a CNS active natural product. Despite having signature polyphenolic character, DHM is ostensibly hydrophobic owing to intermolecular hydrogen bonds that shield hydrophilic phenols. Our research shows DHM becomes ionized at near-neutral pH allowing formulation of salts with transformed solubility. The MicroED co-crystal structure with trolamine reveals DHM salts as metastable solids with unlocked hydrogen bonding and a thermodynamic bent to solubilize in water. All salt formulations show better inhibitory activity against AD tau than the non-salt form, with efficacies correlating to enhanced solubilities. These results underscore the role of structural chemistry in guiding selection of solubilizing agents for chemical formulation. We propose DHM salts are appropriate formulations for research as dietary supplements to promote healthy aging by combating protein misfolding. Additionally, DHM is a suitable lead for medicinal chemistry and possible development of CNS pharmaceuticals.

STimulator of INterferon Genes Agonism Accelerates Anti-tumor Activity in Poorly Immunogenic Tumors

The innate immune agonist STING (STimulator of INterferon Genes) binds its natural ligand 2'3'-cGAMP (cyclic guanosine-adenosine monophosphate) and initiates type I interferon production. This promotes systemic antigen-specific CD8+ T-cell priming that eventually provides potent anti-tumor activity. To exploit this mechanism, we synthesized a novel STING agonist, MSA-1, that activates both mouse and human STING with higher in vitro potency than cGAMP. Following intratumoral (IT) administration of MSA-1 to a panel of syngeneic mouse tumors on immune-competent mice, cytokine upregulation and its exposure were detected in plasma, other tissues, injected tumors, and noninjected tumors. This was accompanied by effective anti-tumor activity. Mechanistic studies in immune-deficient mice suggested that anti-tumor activity of IT-dosed STING agonists is in part due to necrosis and/or innate immune responses such as tumor necrosis factor α (TNF-α) activity, but development of a robust adaptive anti-tumor immunity is necessary for complete tumor elimination. Combination with PD-1 blockade in anti-PD-1-resistant murine models demonstrated that MSA-1 may synergize with checkpoint inhibitors but can also provide superior tumor control as a single agent. We show for the first time that potent cyclic dinucleotides can promote a rapid and stronger induction of the same genes eventually regulated by PD-1 blockade. This may have contributed to the relatively early tumor control observed with MSA-1. Taken together, these data strongly support the development of STING agonists as therapy for patients with aggressive tumors that are partially responsive or nonresponsive to single-agent anti-PD-1 treatment by enhancing the anti-PD-1 immune profile.

Oncology phase II proof-of-concept studies with multiple targets: Randomized controlled trial or single arm?

For oncology drug development, phase II proof-of-concept studies have played a key role in determining whether or not to advance to a confirmatory phase III trial. With the increasing number of immunotherapies, efficient design strategies are crucial in moving successful drugs quickly to market. Our research examines drug development decision making under the framework of maximizing resource investment, characterized by benefit cost ratios (BCRs). In general, benefit represents the likelihood that a drug is successful, and cost is characterized by the risk adjusted total sample size of the phases II and III studies. Phase III studies often include a futility interim analysis; this sequential component can also be incorporated into BCRs. Under this framework, multiple scenarios can be considered. For example, for a given drug and cancer indication, BCRs can yield insights into whether to use a randomized control trial or a single-arm study. Importantly, any uncertainty in historical control estimates that are used to benchmark single-arm studies can be explicitly incorporated into BCRs. More complex scenarios, such as restricted resources or multiple potential cancer indications, can also be examined. Overall, BCR analyses indicate that single-arm trials are favored for proof-of-concept trials when there is low uncertainty in historical control data and smaller phase III sample sizes. Otherwise, especially if the most likely to succeed tumor indication can be identified, randomized controlled trials may be a better option. While the findings are consistent with intuition, we provide a more objective approach.

Starting the fight in the tumor: expert recommendations for the development of human intratumoral immunotherapy (HIT-IT)

A European Society for Medical Oncology (ESMO)-sponsored expert meeting was held in Paris on 8 March 2018 which comprised 11 experts from academia, 11 experts from the pharmaceutical industry and 2 clinicians who were representatives of ESMO. The focus of the meeting was exclusively on the intratumoral injection/delivery of immunostimulatory agents with the aim of harmonizing the standard terms and methodologies used in the reporting of human intratumoral immunotherapy (HIT-IT) clinical trials to ensure quality assurance and avoid a blurring of the data reported from different studies. The goal was to provide a reference document, endorsed by the panel members that could provide guidance to clinical investigators, pharmaceutical companies, ethics committees, independent review boards, patient advocates and the regulatory authorities and promote an increase in the number and quality of HIT-IT clinical trials in the future. Particular emphasis was placed not only on the development of precise definitions to facilitate a better understanding between investigators but also on the importance of systematic serial biopsies as a driver for translational research and the need for the recording and reporting of data, to facilitate a better understanding of the key processes involved.

Characterization of murine CEACAM1 in vivo reveals low expression on CD8+ T cells and no tumor growth modulating activity by anti-CEACAM1 mAb CC1

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) has been reported to mediate both tumorigenic and anti-tumor effects in vivo. Blockade of the CEACAM1 signaling pathway has recently been implicated as a novel mechanism for cancer immunotherapy. CC1, a mouse anti-CEACAM1 monoclonal antibody (mAb), has been widely used as a pharmacological tool in preclinical studies to inform on CEACAM1 pathway biology although limited data are available on its CEACAM1 blocking characteristics or pharmacodynamic-pharmacokinetic profiles. We sought to investigate CEACAM1 expression on mouse tumor and immune cells, characterize CC1 mAb binding, and evaluate CC1 in syngeneic mouse oncology models as a monotherapy and in combination with an anti-PD-1 mAb. CEACAM1 expression was observed at high levels on neutrophils, NK cells and myeloid-derived suppressor cells (MDSCs), while the expression on tumor-infiltrating CD8+ T cells was low. Unexpectedly, rather than blocking, CC1 facilitated binding of soluble CEACAM1 to CEACAM1 expressing cells. No anti-tumor effects were observed in CT26, MBT2 or A20 models when tested up to 30 mg/kg dose, a dose that was estimated to achieve >90% target engagement in vivo. Taken together, tumor infiltrating CD8+ T cells express low levels of CEACAM1 and CC1 Ab mediates no or minimal anti-tumor effects in vivo, as a monotherapy or in combination with anti-PD-1 treatment.

Abstract A08: Combination with a novel STING agonist significantly improves efficacy of anti-PD1 therapy in mouse syngeneic tumor models

Activated STING (STimulator of INterferon Genes) bound to its natural ligand 2,3-cGAMP (cyclic guanosine-adenosine monophosphate), initiates type I interferon (IFN) and pro-inflammatory cytokine production. IFN upregulation is essential to promote antigen-specific CD8+ T-cell priming and leads to potent anti-tumor activity. To exploit this mechanism we synthesized a new STING agonist, MSA-1, that potently activates both mouse and human STING. Intratumoral (IT) administration of MSA-1 to MC38 syngeneic tumor-bearing mice increased tumor and plasma cytokine levels and was effective at driving complete responses (CRs) in 100% of the animals. Most surviving animals developed tumor-specific adaptive immune memory as demonstrated by robust protection against re-challenge with the same tumor type. Mechanistic studies in immune-deficient mice suggested that the initial antitumor activity is in part due to cytokine-driven cytotoxicity and/or other innate immune mechanisms, which may have contributed to some animals not developing an adaptive immune memory. Importantly, MSA-1 caused long-term tumor regressions or CRs in CT26 and B16-F10 tumor models, both of which are intrinsically resistant to single-agent therapy with a fully murinized anti-mouse PD-1 antibody (muDX400). The antitumor immune response in these models was further enhanced when treating the animals with MSA-1 in combination with muDX400. This combination restored T-cell responses in both blood and tumors of the treated mice and provided long-lived immunologic memory in a majority of the animals. Taken together, these data strongly support the development of STING agonists in combination with Keytruda (humanized anti-PD-1 antibody) for patients with tumors that are partially responsive or nonresponsive to single agent anti-PD-1 therapy.

Citation Format: Samanthi A. Perera, Johnny E. Kopinja, Yanhong Ma, Jason Laskey, Kalyan Chakravarthy, Long Cui, Yiping Chen, Jeremy Presland, Sharad Sharma, Shuxia Zhao, Jennifer Piesvaux, Ellen C. Minnihan, Heidi Ferguson, Hyun Chong Woo, Ian Knemeyer, Ilona Kariv, Archie Tse, Saso Cemerski, Jared Cumming, B. Wesley Trotter, Bo-Sheng Pan, George H. Addona, Brian J. Long. Combination with a novel STING agonist significantly improves efficacy of anti-PD1 therapy in mouse syngeneic tumor models [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr A08.

Abstract 4721: Combining STING agonists with an anti-PD-1 antagonist results in marked antitumor activity in immune-excluded tumors

The innate immune agonist STING (STimulator of INterferon Genes) binds its natural ligand 2'3'-cGAMP (cyclic guanosine-adenosine monophosphate) and initiates type I interferon production. This promotes systemic antigen-specific CD8+ T-cell priming that eventually provides potent anti-tumor activity. To exploit this mechanism we synthesized a novel STING agonist, MSA-1, that activates both mouse and human STING with higher in vitro potency than cGAMP. MSA-1 was administered to immune-competent mice bearing MC38 syngeneic tumors to monitor pharmacodynamics, pharmacokinetics and in vivo efficacy. Intratumoral (IT) dosed MSA-1 demonstrated robust tumor and plasma cytokine upregulation and effective anti-tumor activity. The highest tolerated doses provided complete responses (CRs) in 100% of MC38 tumors. Tumor models such as CT26 and B16-F10 that are intrinsically resistant to single-agent therapy with a fully murinized mouse anti-PD-1 antibody (mDX400) also demonstrated long-term tumor regressions or CRs. Mechanistic studies in immune-deficient mice suggested that anti-tumor activity of IT dosed STING agonists are in part due to cytotoxicity and/or innate immune responses rather than development of robust adaptive anti-tumor immunity. To enhance the adaptive immune response, we combined MSA-1 with mDX400 in mouse syngeneic tumor models previously characterized to be unresponsive to anti-PD-1 blockade. This combination restored T-cell responses in both blood and tumors of the treated mice and provided long-lived immunologic memory in a majority of the animals. Taken together, these data strongly support the development of STING agonists in combination with Keytruda for patients with tumors that are partially responsive or non-responsive to single agent anti-PD-1 therapy.

Citation Format: Samanthi A. Perera, Johnny E. Kopinja, Yanhong Ma, Jason Laskey, Kalyan Chakravarthy, Yiping Chen, Long Cui, Jeremy Presland, Shuxia Zhao, Ellen Minnihan, Heidi Ferguson, Jennifer Piesvaux, Bo-Sheng Pan, Hyun Chong Woo, Ian Knemeyer, Saso Cemerski, Jared Cumming, Wesley Trotter, Archie Tse, George H. Addona, Brian J. Long. Combining STING agonists with an anti-PD-1 antagonist results in marked antitumor activity in immune-excluded tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4721.

Abstract 4759: Designing clinical trials in tumor indications with a positive signal in phase 1

Increasingly, the conventional proof-of-concept randomized Phase 2 study is skipped in favor of directly going to Phase 3 after an experimental oncology drug has demonstrated promising anti-tumor activity in Phase 1 with a small sample size. This shift in the balance between certainty and speed is especially evident in the immune-oncology space where the tremendous success of immune checkpoint inhibitors has brought unprecedented competition in the field. The aggressive approach can be very risky no matter how promising an experimental drug appears in Phase 1. In this presentation, we introduce a novel adaptive design that mitigates the risk of late-stage programs. The proposed approach starts with a Phase 2 trial and adds an option in the design that allows the expansion of the Phase 2 trial into Phase 3 if the interim result based on the Phase 2 endpoint is promising. If the decision is to not expand, the study is kept as a Phase 2 trial and the primary analysis is conducted at the end of Phase 2. Otherwise, the study is expanded into a Phase 3 trial and the primary analysis of the study is conducted at the end of Phase 3, utilizing data from all enrolled patients including those already used for the decision making in the ongoing trial. The proposed approach is more efficient than the conventional approach that conducts and analyzes Phase 2 and Phase 3 trials sequentially, and is less risky than the contemporary approach of skipping Phase 2. Importantly, we will show that this design controls overall Type I error regardless of the expansion criterion. As a result, the study can still be considered positive even without expansion to Phase 3.

Citation Format: Cong Chen, Keaven Anderson, Devan V. Mehrotra, Eric H. Rubin, Archie Tse. Designing clinical trials in tumor indications with a positive signal in phase 1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4759.

Predictive Gene Signatures Determine Tumor Sensitivity to MDM2 Inhibition

Early clinical trials using murine double minute 2 (MDM2) inhibitors demonstrated proof-of-concept of p53-induced apoptosis by MDM2 inhibition in cancer cells; however, not all wild-type TP53 tumors are sensitive to MDM2 inhibition. Therefore, more potent inhibitors and biomarkers predictive of tumor sensitivity are needed. The novel MDM2 inhibitor DS-3032b is 10-fold more potent than the first-generation inhibitor nutlin-3a. TP53 mutations were predictive of resistance to DS-3032b, and allele frequencies of TP53 mutations were negatively correlated with sensitivity to DS-3032b. However, sensitivity to DS-3032b of TP53 wild-type tumors varied greatly. We thus used two methods to create predictive gene signatures. First, by comparing sensitivity to MDM2 inhibition with basal mRNA expression profiles in 240 cancer cell lines, a 175-gene signature was defined and validated in patient-derived tumor xenograft models and ex vivo human acute myeloid leukemia (AML) cells. Second, an AML-specific 1,532-gene signature was defined by performing random forest analysis with cross-validation using gene expression profiles of 41 primary AML samples. The combination of TP53 mutation status with the two gene signatures provided the best positive predictive values (81% and 82%, compared with 62% for TP53 mutation status alone). In addition, the top-ranked 50 genes selected from the AML-specific 1,532-gene signature conserved high predictive performance, suggesting that a more feasible size of gene signature can be generated through this method for clinical implementation. Our model is being tested in ongoing clinical trials of MDM2 inhibitors.Significance: This study demonstrates that gene expression profiling combined with TP53 mutational status predicts antitumor effects of MDM2 inhibitors in vitro and in vivoCancer Res; 78(10); 2721-31. ©2018 AACR.

A 2-in-1 adaptive phase 2/3 design for expedited oncology drug development

We propose an adaptive design that allows us to expand an ongoing Phase 2 trial into a Phase 3 trial to expedite a drug development program with fewer patients. Rather than the usual practice of increasing sample size with a less positive interim outcome, here we propose maintaining sample size with such a result and wait for fully mature data. The final Phase 2 data may be negative, may warrant a larger Phase 3 trial, or, in the extreme, could provide a definitively positive outcome. If the interim outcome is more positive, the trial continues to an originally planned larger sample size for a definitive Phase 3 evaluation. All patients from the study are used for inference regardless of the interim expansion decision. We show that no penalty needs to be paid in order to control the overall Type I error of the study, under a mild assumption that is expected to generally hold in practice. The proposed design may be considered an alternative approach to sample size adjustment for ongoing trials. As such, the use of an intermediate endpoint for adaptive decision is a unique feature of the design. A hypothetical example is provided for illustration purpose.

Abstract B1: Gene expression and TP53 mutation analysis predict sensitivity of leukemia cells to MDM2 inhibition by DS-3032b

Background: MDM2 overexpression, by preventing p53 activation, contributes to the growth and development of a variety of solid tumors and hematologic malignancies; hence, MDM2 inhibition could be a promising novel therapeutic strategy. Several MDM2 inhibitors have shown promise in early clinical trials. While preclinical studies generally reveal a requirement of wild-type (wt) TP53 for activity, tumor response to MDM2 inhibitors varies widely in the clinic and may not be strictly linked to TP53 mutational status. Identification of predictive biomarkers is therefore needed to enrich for patients with high likelihood of response. We here propose two gene signature-based models to predict the sensitivity of AML cells to MDM2 inhibition using two different methods.

Methods: Leukemia samples isolated from peripheral blood or bone marrow of patients with newly diagnosed or relapsed/refractory AML were treated using DS-3032b (Daiichi-Sankyo), a dispiropyrrolidine-based, highly potent MDM2 inhibitor currently undergoing clinical trials in solid and hematological malignancies. Forty-one primary AML samples were treated ex vivo for 48 hours with DS-3032b (0, 25, 50, 100, 250, 500, and 1000 nM), and live cell numbers were determined. To define drug sensitivity/resistance, area under the curve (AUC) values, based on%live cell number measured at each concentration, were calculated. Baseline whole-genome RNA expression profile (Affymetrix Human Genome U133 Plus 2.0 Array) and TP53 mutation status (next generation sequencing) were determined. In the first model, we validated a predictive 175-gene signature that was established in a wide range of cancer cells by Daiichi Sankyo. In the second model, we used the random forest method with cross validation to establish a new predictive gene signature.

Results: Eight samples (20%) had TP53 mutations. 6/8 (75%) p53 mutant and 8/33 (24%) of p53 wt samples were resistant (p = 0.01).

In the first model, 11 each p53 wt samples were selected as sensitive or resistant to DS-3032 based on AUC values, and the 175-gene signature was applied. The prediction accuracy was 72%. In the genotype mixed samples, 14 each sensitive and resistant samples were selected, and the prediction accuracy was 79%.

In the second model, we focused on 33 p53 wt samples and trichotomize the samples in the same way as in the first model, and investigated the accuracy of gene expression-derived prediction model with (A) 1500 gene set with the highest variance in mRNA expression (unbiased approach), (B) 32 gene set derived from previous studies (referenced approach), (C) combined (A+B) gene set. The sensitivities to predict cases with high drug sensitivity were 72%, 73% and 82% in scenarios (A), (B) and (C), respectively. The analysis was then extended to all 41 samples and the sensitivity to predict cases with high drug sensitivity remained high (64%, 64% and 72%). The results indicate that an unbiased approach can create a prediction model as accurate as the referenced approach, and moreover, that the combining approach can provide the highest prediction of sensitivity to the MDM2 inhibitor.

Conclusion: The two models reported here could provide a novel strategy to identify the optimal gene signatures for predicting the cases most sensitive to MDM2 inhibitors prior to therapy. These models will be tested in an ongoing AML phase 1 clinical study of DS-3032b.

Citation Format: Jo Ishizawa, Kenji Nakamaru, Takahiko Seki, Koichi Tazaki, Kensuke Kojima, Dhruv Chachad, Archie Tse, Arvind Rao, Michael Andreeff. Gene expression and TP53 mutation analysis predict sensitivity of leukemia cells to MDM2 inhibition by DS-3032b. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B1.

Small-world networks of residue interactions in the Abl kinase complexes with cancer drugs: topology of allosteric communication pathways can determine drug resistance effects

Computational modelling of efficiency and robustness of the residue interaction networks and allosteric pathways in kinase structures can characterize protein kinase sensitivity to drug binding and drug resistance effects.

Abstract 4300: Receptor occupancy and tumor penetration by antibodies, peptides, and antibody fragments: Molecular simulation of imaging assessment

Background: Non-uniform tumor penetration by antibodies may contribute to therapeutic failure. Competition experiments by radiolabeled antibody imaging can guide selection of the antibody dose that fully blocks target binding and thus corresponds to complete therapeutic coverage. However, because antibodies penetrate tumors slowly and non-uniformly, such a competition experiment may reflect only the most accessible sites. A novel approach, termed enhanced competition, has been proposed in which the radiolabeled moiety is smaller and more readily diffusible. In this study, simulations were conducted in order to examine the enhanced competition experiment.

Materials and Methods: The Krogh cylinder distributed model was implemented to simulate the distribution of antibody, antibody fragment, affibody, or peptide in the tumor as a function of time and distance from the capillary wall. Simulations explored traditional and enhanced competition experiments, varying parameters including the nature of the small construct, time between administration of unlabeled and radiolabeled compounds, mass dose, affinity, antigen density, and internalization rate. Results were plotted as nanomolar concentration versus time and distance from the capillary wall. In addition, total tumor %ID/g is presented as a function of time and as a function of unlabeled antibody dose.

Results: Simulation results showed that small constructs access sites in tumors at distances far from capillaries that are not readily accessible to intact antibodies. Under conditions of high affinity (1-10 nM), high antigen density (150,000 sites/cell), and compound internalization (t1/2 = 13 h), a mass of > 40 μg/kg of peptide or affibody construct required a higher dose of antibody to displace the radioactive signal compared to traditional competition with radiolabeled antibody. However, the difference in imaging signal between sub-saturating and fully displacing antibody doses is expected to be difficult to detect.

Conclusions: The phenomenon predicted by the enhanced competition paradigm using small constructs is validated by modeling. Simulated imaging competition experiments indicate that affinity and mass dose levels are critical factors in this approach. High affinity small constructs and enhanced precision of imaging techniques will be required to fully evaluate target occupancy and saturation in vivo.

Citation Format: Kelly D. Orcutt, Gregory P. Adams, Anna M. Wu, Matthew Silva, Jack Hoppin, Catey Harwell, Manabu Matsumura, Masakatsu Kotsuma, Daniel Freeman, Archie Tse, Jonathan Greenberg, Andrew Scott, Robert A. Beckman. Receptor occupancy and tumor penetration by antibodies, peptides, and antibody fragments: Molecular simulation of imaging assessment. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4300. doi:10.1158/1538-7445.AM2014-4300

Chk1 inhibition after replicative stress activates a double strand break response mediated by ATM and DNA-dependent protein kinase

Checkpoint kinase 1 (Chk1) regulates cell cycle checkpoints and DNA damage repair in response to genotoxic stress. Inhibition of Chk1 is an emerging strategy for potentiating the cytotoxicity of chemotherapeutic drugs. Here, we demonstrate that AZD7762, an ATP -competitive Chk1/2 inhibitor induces gammaH2AX in gemcitabine-treated cells by altering both dynamics and stability of replication forks, allowing the firing of suppressed replication origins as measured by DNA fiber combing and causing a dramatic increase in DNA breaks as measured by comet assay. Furthermore, we identify ATM and DNA-PK, rather than ATR, as the kinases mediating gammaH2AX induction, suggesting AZD7762 converts stalled forks into double strand breaks (DSBs). Consistent with DSB formation upon fork collapse, cells deficient in DSB repair by lack of BRCA2, XRCC3 or DNA-PK were selectively more sensitive to combined AZD7762 and gemcitabine. Checkpoint abrogation by AZD7762 also caused premature mitosis in gemcitabine-treated cells arrested in G(1)/early S-phase. Prevention of premature mitotic entry via Cdk1 siRNA knockdown suppressed apoptosis. These results demonstrate that chemosensitization of gemcitabine by Chk1 inhibition results from at least three cellular events, namely, activation of origin firing, destabilization of stalled replication forks and entry of cells with damaged DNA into lethal mitosis. Additionally, the current study indicates that the combination of Chk1 inhibitor and gemcitabine may be particularly effective in targeting tumors with specific DNA repair defects.

A phase I clinical trial of FOLFIRI in combination with the pan-cyclin-dependent kinase (CDK) inhibitor flavopiridol

BACKGROUND

The cyclin-dependent kinase inhibitor flavopiridol increases irinotecan- and fluorouracil-induced apoptosis. We conducted a phase I trial of FOLFIRI + flavopiridol in patients with advanced solid tumors.

DESIGN

FOLFIRI + flavopiridol were administered every 2 weeks. Based on sequence-dependent inhibition, flavopiridol was given 3 h after irinotecan but before 5-FU. Two maximum tolerated doses were determined, one with flavopiridol administered over 1 h, and one with flavopiridol split as a 30-min bolus followed by a 4-h infusion.

RESULTS

A total of 74 patients were enrolled and 63 were evaluable. The MTD with FOLFIRI was flavopiridol 80 mg/m(2) over 1 h or 35 mg/m(2) bolus + 35 mg/m(2) over 4 h. Dose-limiting toxicities were diarrhea, fatigue, neutropenia, and neuropathy. Clinical activity included 2 partial responses in small bowel cancer and bladder cancer and 1 complete response in mucosal melanoma. Stable disease was seen in 22 patients. Pharmacokinetic studies showed increasing C(max) with increasing flavopiridol dose. Clinical benefit was correlated with the presence of wild-type p53. Of 25 patients with colorectal cancer, 11 had as best response SD for >3 m (median 6 m, range 4.2-15.4 m), despite failing ≥1 irinotecan-containing regimen.

CONCLUSIONS

Treatment with flavopiridol and FOLFIRI is a safe and effective regimen. Concentrations of flavopiridol that enhance the effects of FOLFIRI can be achieved. Clinical activity is encouraging and includes prolonged stable disease in patients with irinotecan-refractory colorectal cancer.

Regional chemotherapy for unresectable primary liver cancer: results of a phase II clinical trial and assessment of DCE-MRI as a biomarker of survival

BACKGROUND

This study reports the results of hepatic arterial infusion (HAI) with floxuridine (FUDR) and dexamethasone (dex) in patients with unresectable intrahepatic cholangiocarcinoma (ICC) or hepatocellular carcinoma (HCC) and investigates dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) assessment of tumor vascularity as a biomarker of outcome.

PATIENTS AND METHODS

Thirty-four unresectable patients (26 ICC and eight HCC) were treated with HAI FUDR/dex. Radiologic dynamic and pharmacokinetic parameters related to tumor perfusion were analyzed and correlated with response and survival.

RESULTS

Partial responses were seen in 16 patients (47.1%); time to progression and response duration were 7.4 and 11.9 months, respectively. Median follow-up and median survival were 35 and 29.5 months, respectively; 2-year survival was 67%. DCE-MRI data showed that patients with pretreatment integrated area under the concentration curve of gadolinium contrast over 180 s (AUC 180) >34.2 mM.s had a longer median survival than those with AUC 180 <34 mM.s (35.1 versus 19.1 months, P = 0.002). Decreased volume transfer exchange between the vascular space and extracellular extravascular space (-DeltaK(trans)) and the corresponding rate constant (-Deltak(ep)) on the first post-treatment scan both predicted survival.

CONCLUSIONS

In patients with unresectable primary liver cancer, HAI therapy can be effective and safe. Pretreatment and early post-treatment changes in tumor perfusion characteristics may predict treatment outcome.

Analysis of survival with modified docetaxel, cisplatin, fluorouracil (mDCF), and bevacizumab (BEV) in patients with metastatic gastroesophageal (GE) adenocarcinoma: Results of a phase II clinical trial

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Background: Metastatic GE cancer is an aggressive disease with poor patient (pt) outcomes. Despite response rates of 30–60% to combination chemotherapy, response duration is usually 4–6 mo and 24-mo survival is 5–10%. The addition of BEV to chemotherapy has improved survival in several solid tumors, and has demonstrated encouraging activity in GE cancer (Shah et al, JCO 2006). We report mature tolerability and efficacy results of mDCF+BEV in GE cancer, with an emphasis on prolonged pt survival. Methods: Previously untreated metastatic GE pts with adequate end organ function received BEV 10mg/kg, Docetaxel 40mg/m2, FU 400mg/m2, Leucovorin 400mg/m2 on day 1, FU 1000 mg/m2/day x 2 days IVCI, and Cisplatin 40mg/m2 on day 3. Treatment is repeated every 14 days without prophylactic growth factor support. The primary objective is to improve 6-month progression free survival (PFS) from 43% (historical DCF control) to 63% with the addition of BEV. Target accrual is 44 evaluable pts, with 10% type I & II error. Secondary objectives include tolerability, response rates (RECIST), median PFS, 12-mo survival, and overall survival (OS). Results: Pt enrollment has completed: median age 57(range 29–74), median KPS 80% (70–100), M:F 32:12, gastric/GEJ/esophagus 22:17:5. In 39 patients with measurable disease we observed 26 confirmed partial responses (67%, 95% CI 50%- 81%), and 12 (31%) stable disease. Six-month PFS is 79% (95% CI 68%-93%), the median PFS is 12 mo (95% CI: 8.8–16). At median follow up of 12.3 mo, median OS is 16.2 mo (95%CI 11.4-infinitiy). 12- and 18-mo OS is 63% (95%CI 44–77%) and 46% (95%CI 27–63%), respectively. Minimal chemotherapy related grade 3–4 adverse events were observed: fatigue (20%), dehydration (13%), mucositis (9%), nausea/vomiting (7%), febrile neutropenia (4%). BEV related adverse event was perforation (n=1) and bleeding (n=1). 31% developed grade 3–4 venous thromboembolism, of which 93% were asymptomatic. No grade 3–4 hypertension, proteinuria or arterial thrombosis was observed. Conclusions: mDCF+BEV appears tolerable and has notable long term pt outcomes: 6-mo PFS is 79% (surpassing our efficacy endpoint), median OS 16.2 mo, and 18-mo OS 46%.

No significant financial relationships to disclose.

A phase II study of flavopiridol (Alvocidib) in combination with docetaxel in refractory, metastatic pancreatic cancer

BACKGROUND/AIMS

Pancreatic adenocarcinoma (PC) harbors frequent alterations in p16, resulting in cell cycle dysregulation. A phase I study of docetaxel and flavopiridol, a pan-cyclin-dependent kinase inhibitor, demonstrated encouraging clinical activity in PC. This phase II study was designed to further define the efficacy and toxicity of this regimen in patients with previously treated PC.

METHODS

Patients with gemcitabine-refractory, metastatic PC were treated with docetaxel 35 mg/m(2) followed by flavopiridol 80 mg/m(2) on days 1, 8, and 15 of a 28-day cycle. Tumor measurements were performed every two cycles. A Simon two-stage design was used to evaluate the primary endpoint of response.

RESULTS

Ten patients were enrolled, and 9 were evaluable for response. No objective responses were observed; however, 3 patients (33%) achieved transient stable disease, with one of these patients achieving a 20% reduction in tumor size. Median survival was 4.2 months, with no patients alive at the time of analysis. Adverse events were significant, with 7 patients (78%) requiring >or=1 dose reduction for transaminitis (11%), grade 4 neutropenia (33%), grade 3 fatigue (44%), and grade 3 diarrhea (22%).

CONCLUSIONS

The combination of flavopiridol and docetaxel has minimal activity and significant toxicity in this patient population. These results reflect the challenges of treating patients with PC in a second-line setting where the risk/benefit equation is tightly balanced.

Pharmacokinetics (PK) of split-dose flavopiridol (F) administered with CPT-11 (CPT) and cisplatin (Cis)

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Background: F, a cyclin-dependent kinase inhibitor, induces tumor lysis in CLL when administered as a 30 mg/m2 loading dose over 0.5h followed by a 30 mg/m2 maintenance dose over 4h (hybrid F; Byrd et al, Blood 2006). F given as a 1h bolus (bolus F) demonstrates promising clinical activity when combined with CPT in solid tumors (Shah et al, CCR 2005). Data suggest that F concentrations of 2–3 μM are required to enhance the effects of CPT in solid tumors (Motwani et al, CCR 2001), but controversy exists over the optimal F schedule for chemotherapy potentiation. Methods: We are conducting a phase I trial of CPT/Cis→F, with F administered on both a bolus F and hybrid F schedule. After identifying the maximum tolerated dose (MTD) of bolus F (CPT/Cis→F 50mg/m2), the hybrid F schedule was examined. The F loading dose was escalated from 20→30mg/m2 and the F maintenance dose escalated from 20→50mg/m2. Plasma samples were obtained from patients (pts) treated with bolus F at the MTD and with hybrid F at all dose levels. To better assess F PK interaction with CPT/Cis, F was given before CPT/Cis on cycle 2 only. Results: Complete PK data are available from 6 pts treated at the bolus F MTD (50 mg/m2) and on 20 pts treated with hybrid F (20→20 mg/m2, 25→25 mg/m2 and 30→30 mg/m2) for cycles 1 and 2. Both bolus F and hybrid F PK are consistent with data previously reported. Although cycle 1 AUCs are similar for bolus F 50 mg/m2 and hybrid F 30→30 mg/m2 (10.47±4.97 vs 10.75±15.14 μM/h, p=NS), the Cmax achieved with bolus F 50 mg/m2 is significantly greater than that achieved with hybrid F 30→30 mg/m2 (2.31±0.65 vs 1.21±0.35 μM, p<0.02). No significant PK differences occurred between cycles 1 and 2. Toxicity was not associated with F Cmax. With CPT/Cis→bolus F, the PR rate was 10/29 (35%) vs 3/33 (9%) with CPT/Cis→hybrid F. Conclusions: The Cmax achieved with bolus F is greater than that achieved with hybrid F, with no increase in toxicity. Additionally, the Cmax achieved with hybrid F does not exceed the 2 μM plasma concentration required for potentiation of chemotherapy-induced apoptosis. The greater number of responses achieved with bolus F suggests that bolus F may be more efficacious than hybrid F when used in combination with CPT for the treatment of solid tumors. (Supported by R01-CA67819)

No significant financial relationships to disclose.

Multicenter phase II study of irinotecan, cisplatin, and bevacizumab in patients with metastatic gastric or gastroesophageal junction adenocarcinoma

PURPOSE

Bevacizumab improves survival in several solid tumor malignancies when combined with chemotherapy. We evaluated the efficacy and safety of the addition of bevacizumab to chemotherapy in the treatment of gastric and gastroesophageal junction (GEJ) adenocarcinoma.

PATIENTS AND METHODS

Forty-seven patients with metastatic or unresectable gastric/GEJ adenocarcinoma were treated with bevacizumab 15 mg/kg on day 1, irinotecan 65 mg/m2, and cisplatin 30 mg/m2 on days 1 and 8, every 21 days. The primary end point was to demonstrate a 50% improvement in time to progression over historical values. Secondary end points included safety, response, and survival.

RESULTS

Patient characteristics were as follows: median age 59 years (range, 25 to 75); Karnofsky performance status 90% (70% to 100%); male:female, 34:13; and gastric/GEJ, 24:23. With a median follow-up of 12.2 months, median time to progression was 8.3 months (95% CI, 5.5 to 9.9 months). In 34 patients with measurable disease, the overall response rate was 65% (95% CI, 46% to 80%). Median survival was 12.3 months (95% CI, 11.3 to 17.2 months). We observed no increase in chemotherapy related toxicity. Possible bevacizumab-related toxicity included a 28% incidence of grade 3 hypertension, two patients with a gastric perforation and one patient with a near perforation (6%), and one patient with a myocardial infarction (2%). Grade 3 to 4 thromboembolic events occurred in 25% of patients. Although the primary tumor was unresected in 40 patients, we observed only one patient with a significant upper gastrointestinal bleed.

CONCLUSION

Bevacizumab can be safely given with chemotherapy even with primary gastric and GEJ tumors in place. The response rate, time to disease progression (TTP), and overall survival are encouraging, with TTP improved over historical controls by 75%. Further development of bevacizumab in gastric and GEJ cancers is warranted.

Aurora Kinases: New Targets for Cancer Therapy

The Aurora kinase family is a collection of highly related serine/threonine kinases that functions as a key regulator of mitosis. In mammalian cells, Aurora has evolved into three related kinases known as Aurora-A, Aurora-B, and Aurora-C. These kinases are overexpressed in a number of human cancers, and transfection studies have established Aurora-A as a bone fide oncogene. Because Aurora overexpression is associated with malignancy, these kinases have been targeted for cancer therapy. This article reviews the multiple functions of Aurora kinase in the regulation of mitosis and the mitotic checkpoint, the role of abnormal Aurora kinase activity in the development of cancer, the putative mechanisms of Aurora kinase inhibition and its antitumor effects, the development of the first generation of Aurora kinase inhibitors, and prospects for the future of Aurora kinase inhibition in the treatment of cancer.

Final results of a multicenter phase II study of irinotecan (CPT), cisplatin (CIS), and bevacizumab (BEV) in patients with metastatic gastric or gastroesophageal (GEJ) adenocarcinoma (NCI #6447)

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Background: BEV improves survival in several solid tumors when combined with chemotherapy. CPT/CIS is active in gastric and GEJ cancers with a median time to progression(TTP) of 4.2 months, response rate(RR) of 30%, and median survival of ∼7 months (Pozzo Ann Onc 2004). Anti-angiogenic therapy for upper GI cancers is of concern due to a potential increased risk of perforation or GI bleed. We evaluated the efficacy and safety of the combination of CPT, CIS, and BEV in the treatment of gastric and GEJ cancers. Methods: 47 patients with previously untreated metastatic gastric or GEJ adenocarcinomas were treated with BEV 15mg/kg day 1, CPT 65mg/m2 and CIS 30mg/m2 days 1 and 8, every 21 days. The primary endpoint was TTP, with 90% power to demonstrate a 50% improvement in TTP (eg. from 5 to 7.5 months) over historical control. Safety, response, and survival were secondary endpoints. Results: Patient characteristics: median age 59 (range 25–75), KPS 90% (70%-100%), Male 34, Gastric/GEJ 27:20. With a median follow up of 9.0 months, median TTP is 9.9 months (95%CI: 6.5–11.8 months). In 33 patients with measurable disease, the RR (partial + complete) is 66.7% (95%CI: 51–83%). Median survival is 12.6 months (95%CI: 10.1–17.1 months). We observed no change in expected CPT/CIS related toxicity: eg. grade 3/4 neutropenia (29%), nausea/vomiting (10%), and diarrhea (13%). Possible BEV related toxicity includes 2 gastric perforations, 1 grade 3 peri-rectal fistula, 2 cardiac events(1 ischemia, 1 reduced ejection fraction), and 10 patients with grade 3/4 hypertension. Although the primary tumor was unresected in 35 patients, we observed only 1 patient with an upper GI bleed. Grade 3/4 thromboembolic events occurred in 25%. Conclusions: The combination of CPT/CIS/BEV is active in gastric and GEJ cancers. The toxicity profile is acceptable. The primary endpoint of improving TTP was exceeded by 100% with median TTP 9.9 months. Despite the majority of patients having their primary tumor unresected, GI bleeding was not significant. The thromboembolic and perforation rates with CPT/CIS are similar with or without BEV (Shah et al JCO 2005). Further development of BEV in gastric and GEJ cancers is clearly warranted.

[Table: see text]

Cetuximab shows activity in colorectal cancer patients with tumors that do not express the epidermal growth factor receptor by immunohistochemistry

PURPOSE

To establish evidence of activity, or lack thereof, of cetuximab-based therapy in patients with refractory colorectal cancer with tumors that do not demonstrate epidermal growth factor receptor (EGFR) expression by immunohistochemistry (IHC).

PATIENTS AND METHODS

Pharmacy computer records were reviewed to identify all patients who received cetuximab at Memorial Sloan-Kettering Cancer Center in a nonstudy setting during the first 3 months of cetuximab's commercial availability. Medical records of these patients were then reviewed to identify colorectal cancer patients who had experienced failure with a prior irinotecan-based regimen and who had a pathology report indicating an EGFR-negative tumor by IHC. Pathology slides from these patients were reviewed by a reference pathologist to confirm EGFR negativity, and computed tomography scans during cetuximab-based therapy were reviewed by a reference radiologist. Response rates were reported using WHO criteria.

RESULTS

Sixteen chemotherapy-refractory, EGFR-negative colorectal cancer patients who received cetuximab in a nonstudy setting were identified. Fourteen of these patients received cetuximab plus irinotecan, and two received cetuximab monotherapy. In the 16 patients, four major objective responses were seen (response rate, 25%; 95% CI, 4% to 46%).

CONCLUSION

Colorectal cancer patients with EGFR-negative tumors have the potential to respond to cetuximab-based therapies. EGFR analysis by current IHC techniques does not seem to have predictive value, and selection or exclusion of patients for cetuximab therapy on the basis of currently available EGFR IHC does not seem warranted.

Endocytosis in identified rat corticotrophs

1. We used the patch-clamp technique, in conjunction with membrane capacitance measurement, fluorescence measurement of intracellular calcium concentration ([Ca(2+)](i)), and flash photolysis of caged Ca(2+) to study exo- and endocytosis in identified rat corticotrophs. 2. Exocytosis stimulated by depolarization pulses was typically followed by a 'slow' endocytosis that retrieved the membrane with a time constant of approximately 6 s. The efficiency (the endocytosis/exocytosis amplitude ratio) of 'slow' endocytosis was approximately 1.2 at [Ca(2+)](i) < 3 microM and increased to approximately 1.6 at [Ca(2+)](i) > 3 microM. 3. Whole-cell dialysis through a patch pipette did not affect the kinetics and the efficiency of 'slow' endocytosis, but the amplitude of exocytosis was reduced. 4. 'Slow' endocytosis did not require sustained [Ca(2+)](i) elevation and its kinetics was only weakly [Ca(2+)](i) dependent. Our results suggest that 'slow' endocytosis involves a Ca(2+) sensor with a high Ca(2+) affinity (approximately 500 nM). 5. At high [Ca(2+)](i) (> 10 microM), the 'slow' endocytosis was frequently preceded by a 'fast' endocytosis that comprised multiple steps of rapid decrease in membrane capacitance. 6. Neither calmodulin nor calcineurin appeared to be the Ca(2+) sensor for endocytosis because the two forms of endocytosis were not affected by the calmodulin inhibitor calmidazolium (500 microM) or the calcineurin inhibitors cyclosporin A (1 microM) and calcineurin autoinhibitory peptide (1 mg ml(-1)). Ba(2+), a poor activator of calmodulin, could support both forms of endocytosis but slowed the kinetics of 'slow' endocytosis approximately 2-fold. 7. Non-hydrolysable analogues of GTP (GDP-beta-S) and ATP (ATP-gamma-S) also failed to inhibit either form of endocytosis, indicating that neither GTP nor ATP was essential for endocytosis. 8. We suggest that the high Ca(2+) affinity of 'slow' endocytosis may be important for maintaining continuous cycles of exocytosis-endocytosis during sustained adrenocorticotropin secretion in corticotrophs.

Voltage-gated Ca2+ channels and intracellular Ca2+ release regulate exocytosis in identified rat corticotrophs

1. The patch clamp technique was used in conjunction with a fluorescent Ca2+ indicator (indo-1, or indo-1FF) to measure simultaneously cytosolic Ca2+ concentration ([Ca2+]i) and exocytosis (changes in membrane capacitance) in single, identified rat corticotrophs. 2. Exocytosis could be stimulated by extracellular Ca2+ entry (via voltage-gated Ca2+ channels). A train of depolarizations could exhaust the pool of readily releasable granules and the pool replenished with a time constant of 42 s (at 22-25 C). 3. Recordings from cells with 0.5 mM intracellular cAMP showed that the amplitude of the depolarization-triggered exocytosis, the Ca2+ sensitivity of exocytosis, as well as the rate of replenishment of the readily releasable pool, were similar to the controls. 4. Exocytosis could also be stimulated by intracellular Ca2+ release from the inositol 1,4, 5-trisphosphate (IP3)-sensitive store (via flash photolysis of caged IP3). At comparable [Ca2+]i, extracellular Ca2+ entry and intracellular Ca2+ release had similar efficacy in triggering exocytosis. 5. The rate of exocytosis triggered via depolarization or intracellular Ca2+ release was much faster than that triggered via uniform elevation of [Ca2+]i (Ca2+ dialysis or flash photolysis of caged Ca2+). 6. The above findings suggest that both intracellular Ca2+ release and voltage-gated extracellular Ca2+ entry generate a spatial Ca2+ gradient, such that the local [Ca2+] near the exocytic sites was approximately 3-fold higher than the mean cytosolic [Ca2+]. However, neither cAMP nor the spatial Ca2+ gradient generated during depolarization could account for the high efficacy of corticotropin-releasing hormone (CRH) in stimulating adrenocorticotropic hormone (ACTH) secretion from corticotrophs.

Stimulation of Ca(2+)-independent exocytosis in rat pituitary gonadotrophs by G-protein

We employed the whole-cell recording technique in conjunction with fluorometry to measure cytosolic Ca(2+) concentration ([Ca(2+)](i)) and exocytosis (capacitance measurement) in single, identified rat gonadotrophs. Direct activation of G-protein (via intracellular dialysis of non-hydrolysable analogues of GTP, but not of GDP) triggered a slow rise in capacitance even in the presence of a fast intracellular Ca(2+) chelator. The broad-spectrum kinase inhibitors H7 and staurosporine did not prevent this Ca(2+)-independent exocytosis, ruling out the involvement of the cAMP and PKC pathways. AlF(4)(-), a potent stimulator of heterotrimeric G-proteins, failed to stimulate any exocytosis when the intracellular Ca(2+) store was depleted, implicating the involvement of AlF(4)(-)-insensitive G-protein(s). Maximal stimulation of Ca(2+)-independent exocytosis by GTP analogues did not reduce the number of readily releasable granules that were available subsequently for Ca(2+)-dependent release. The last finding raises the possibility that the G-protein-stimulated Ca(2+)-independent exocytosis may regulate a pool of granules that is distinct from the Ca(2+)-dependent pool.

Tissue-specific expression of functional isoforms of mouse folypoly-gamma-glutamae synthetase: a basis for targeting folate antimetabolites

Folates and folate antimetabolites are metabolically trapped in mammalian cells as polyglutamates, a process catalyzed by folylpoly-gamma-glutamate synthetase (FPGS). Using 5'-rapid amplification of cDNA ends, RNase protection assays, transfection of cDNAs into FPGS-deficient cells, and kinetic analysis of recombinant enzymes expressed in insect cells, it was determined that the species of active FPGS in mouse liver and kidney was different from that in mouse tumor cells, bone marrow, and intestine. The NH2-terminal peptide of hepatic enzyme contained 18 amino acids not found in enzyme from dividing tissues, and the specificity of the two isoforms for antifolates also differed, suggesting different architecture of the active sites. In most tissues, the expression of one isozyme or the other was an all-or-nothing event. The exclusive use of one of two alternative sets of initial coding exons in different tissues underlies this phenomenon, suggesting the design of antifolates specific for activation by individual FPGS isoforms and hence tissue-selective targeting of antifolate therapy for cancer, arthritis, or psoriasis.