Citations

Background: Hydrogen peroxide (H2O2)-induced oxidative stress has been demonstrated to induce afterdepolarizations and triggered activities in isolated myocytes, but the underlying mechanisms remain not fully understood. We aimed to explore whether protein kinase C (PKC) activation plays an important role in oxidative stress-induced afterdepolarizations. Methods: Action potentials and ion currents of isolated rabbit cardiomyocytes were recorded using the patch clamp technique. H2O2 (1 mM) was perfused to induce oxidative stress and the specific classical PKC inhibitor, Gö 6983 (1 μM), was applied to test the involvement of PKC. Results: H2O2 perfusion prolonged the action potential duration and induced afterdepolarizations. Pretreatment with Gö 6983 prevented the emergence of H2O2-induced afterdepolarizations. Additional application of Gö 6983 with H2O2 effectively suppressed H2O2-induced afterdepolarizations. H2O2 increased the late sodium current (INa,L) (n = 7, p < 0.01) and the L-type calcium current (ICa,L) (n = 5, p < 0.01), which were significantly reversed by Gö 6983 (p < 0.01). H2O2 also increased the transient outward potassium current (Ito) (n = 6, p < 0.05). However, Gö 6983 showed little effect on H2O2-induced enhancement of Ito. Conclusions: H2O2 induced afterdepolarizations via the activation of PKC and the enhancement of ICa,L and INa,L. These results provide evidence of a link between oxidative stress, PKC activation and afterdepolarizations.

Abstract Rationale The release of eosinophil granule proteins in the lungs of patients with asthma has been dogmatically linked with lung remodeling and airway hyperresponsiveness. However, the demonstrated inability of established mouse models to display the eosinophil degranulation occurring in human subjects has prevented a definitive in vivo test of this hypothesis. Objectives To demonstrate in vivo causative links between induced pulmonary histopathologies/lung dysfunction and eosinophil degranulation. Methods A transgenic mouse model of chronic T-helper cell type 2–driven inflammation overexpressing IL-5 from T cells and human eotaxin 2 in the lung (I5/hE2) was used to test the hypothesis that chronic histopathologies and the development of airway hyperresponsiveness occur as a consequence of extensive eosinophil degranulation in the lung parenchyma. Measurement and Main Results Studies targeting specific inflammatory pathways in I5/hE2 mice surprisingly showed that eosinophil-dependent immunoregulative events and not the release of individual secondary granule proteins are the central contributors to T-helper cell type 2–induced pulmonary remodeling and lung dysfunction. Specifically, our studies highlighted a significant role for eosinophil-dependent IL-13 expression. In contrast, extensive degranulation leading to the release of major basic protein-1 or eosinophil peroxidase was not causatively linked to many of the induced pulmonary histopathologies. However, these studies did define a previously unappreciated link between the release of eosinophil peroxidase (but not major basic protein-1) and observed levels of induced airway mucin. Conclusions These data suggest that improvements observed in patients with asthma responding to therapeutic strategies ablating eosinophils may occur as a consequence of targeting immunoregulatory mechanisms and not by simply eliminating the destructive activities of these purportedly end-stage effector cells.

34 Background: Phase II clinical trials aim to identify promising experimental regimens for further testing in phase III trials. Testing targeted therapies with predictive biomarkers mandates efficient trial designs. Current biomarker-based trial designs, including the enrichment, all-comers, and adaptive designs, randomize patients to receive treatment or not throughout the entire duration of the trial. Recognizing the need for randomization yet acknowledging the possibility of promising but nonconclusive results after a preplanned interim analysis (IA), we propose a two-stage phase II design that allows for the possibility of direct assignment (i.e., stop randomization and assign all patients to the experimental arm in stage II) based on IA results. Methods: Using simulations, we compared properties of the direct assignment option design to a 1:1 randomized phase II design and assessed the impact of the timing of IA (after 33%, 50%, or 67% of accrual) and number of IA (one versus two with option for direct assignment at the first and second) over a range of response rate ratios (between 1.0 and 3.0). Results: Between 12% and 30% of the trials (out of 6,000 simulated trials) adopt direct assignment in stage II, with direct adoption depending on the treatment effect size and specified type I error rate (TIER). The direct assignment option design has minimal loss in power (<1.8%) and minimal increase in T1ER (<2.1%) compared to a 1:1 randomized design. The maximum loss in power across possible timings of IA was <1.2%. For the direct assignment option design, there was a 20%-50% increase in the number of patients treated on the experimental (vs. control) arm for the 1 IA case, and 40%-100% increase for the 2 IA case. Conclusions: Testing predictive biomarkers in clinical trials requires new design strategies. In the spectrum of phase II designs from adaptive to balanced randomized all-comers or enrichment designs, the direct assignment design provides a middle ground with desirable statistical properties that may appeal to both clinicians and patients.

LBA9000^ Background: The humanized monoclonal IgG4 anti-PD-1 antibody MK-3475 has demonstrated durable antitumor activity in MEL and NSCLC. We evaluated MK-3475 efficacy and safety in a pooled analysis of 411 MEL pts. Methods: A nonrandomized cohort of ipilimumab-naive (IPI-N) and IPI-treated (IPI-T) pts treated with MK-3475 10 mg/kg Q2W, 10 mg/kg Q3W, or 2 mg/kg Q3W and randomized cohorts of IPI-N and IPI-T pts treated with 2 Q3W or 10 Q3W were included. Response was assessed every 12 wk by RECIST 1.1 by independent central review and by immune-related response criteria (irRC) by investigator. Results: 162 pts were treated at 2 Q3W, 192 at 10 Q3W, and 57 at 10 Q2W. 190 pts were IPI-N and 221 were IPI-T. As of the 10/18/2013 cutoff, all pts had ≥6 mo follow-up and >75% had ≥9 mo follow-up. Among the 365 pts with measurable disease at baseline, ORR by RECIST was 40% (95% CI 32%-48%) in IPI-N and 28% (95% CI 22%-35%) in IPI-T pts. Responses were durable (88% ongoing at analysis). Median PFS by RECIST was 24 wk in IPI-N and 23 wk in IPI-T pts. Median OS was not reached, with 1-y OS of 71% in all pts. Benefit was observed by both RECIST and irRC at all doses and schedules in IPI-N and IPI-T pts (Table). MK-3475 demonstrated activity in all major subgroups irrespective of ECOG PS, LDH levels, BRAFmutation, M stage, and number and type of prior therapy. Overall, 12% of pts experienced drug-related grade 3/4 AEs and 4% discontinued due to a drug-related AE. There were no drug-related deaths. Conclusions: MK-3475 showed durable responses and a manageable safety profile across dose and schedules in IPI-N and IPI-T MEL pts. The observed efficacy and safety suggest MK-3475 may be an appropriate treatment for all pts with MEL. Clinical trial information: NCT01295827. [Table: see text]

457 Background: Curative therapy for PDAC is currently achievable through resection only, but ≤ 15% of patients are candidates for surgery. FG-3019, a recombinant human mAb to connective tissue growth factor (CTGF), plus gemcitabine (G) significantly reduced tumor growth, increased apoptosis and improved survival vs G alone in the KPC mouse model. Higher FG-3019 exposure and lower baseline (BL) CTGF were independently and significantly associated with improved overall median and 1-year survival (OS) in a Ph2a trial with G and erlotinib in stage 3 or 4 PDAC. Neoadjuvant treatment of LAPC with FG-3019 combined with multidrug therapy may change the fibrotic character of LAPC and thus may make it amenable to surgical resection and potentially improve OS. Methods: Patients with unresectable LAPC (confirmed by laparoscopy) are randomized to G/NP ±FG-3019 for 6-cycle/24-week treatment. Safety, efficacy, PK and changes in CT, PET, & CA19.9 from BL through end of treatment (EOT) are assessed. Up to 4 endoscopic ultrasound (EUS) guided core biopsies are collected at BL. Protein microarrays of pre- and post-treatment biopsies are prepared from tumor and stromal cells isolated by laser capture microdissection. Surgical exploration is performed in subjects who achieved the protocol-defined criteria for possible resection. Results: To date, 11 subjects were enrolled with 5 randomized to +FG-3019 arm. There were no complications from laparoscopy or EUS core biopsies that were clinically significant or delayed dosing. Per investigator assessment, no FG-3019-related SAEs were reported, nor any identified toxicity suspected from combination of FG-3019 with chemotherapy. Overall, CA19.9 mean change from BL was −62.7% at Week 8 (n = 8), and target lesions were reduced by 20.6% (n = 6) at Week 16. Three out of 4 subjects had PET SUVmax reductions of ≥ 30% at EOT. Additional data from protein microarrays will be presented. Conclusions: Based on the limited data collected so far, this trial design is feasible and the G/NP +FG-3019 combination is well-tolerated and appears to be active. Summary results on surgical exploration of subjects will be provided later. Clinical trial information: NCT02210559.

Cardiac development in vertebrates is a finely tuned process regulated by a set of conserved signaling pathways. Perturbations of these processes are often associated with congenital cardiac malformations. Platelet-derived growth factor receptor α (PDGFRα) is a highly conserved tyrosine kinase receptor, which is essential for development and organogenesis. Disruption of Pdgfrα function in murine models are embryonic lethal due to severe cardiovascular defects, suggesting a role in cardiac development, thus necessitating the use of alternative models to explore its precise function. In this study, we generated a zebrafish pdgfra mutant line by gene trapping, in which the Pdgfra protein is truncated and fused with mRFP (Pdgfra-mRFP). Our results demonstrate that pdgfra mutants have defects in cardiac morphology as a result of abnormal fusion of myocardial precursors. Expression analysis of the developing heart at later stages suggested that Pdgfra-mRFP is expressed in the endocardium. Further examination of the endocardium in pdgfra mutants revealed defective endocardial migration to the midline, where cardiac fusion eventually occurs. Together, our data suggests that pdgfra is required for proper medial migration of both endocardial and myocardial precursors, an essential step required for cardiac assembly and development.