Abstract OT2-07-07: ATR inhibitor M6620 (formerly VX-970) with cisplatin in metastatic triple-negative breast cancer: Preliminary results from a phase 1 dose expansion cohort (NCT02157792)

Background: ATR is a critical regulator of the cellular response to replication stress; it signals DNA damage repair, mediated through homologous recombination. Many cancers depend on ATR to survive DNA damage. M6620 is a potent, selective inhibitor of ATR that augments the anticancer activity of cisplatin in preclinical triple-negative breast cancer (TNBC) models. Given the high prevalence of TP53 mutations in TNBC and limited platinum responsiveness in patients lacking a BRCA1/2 mutation, this study was designed to evaluate the safety and efficacy of M6620 in combination with cisplatin in an expansion cohort of patients with BRCA1/2 wild-type advanced/metastatic TNBC.

Methods: Eligible patients had advanced/metastatic ER-, PR-, and HER2- breast cancer with 0-2 prior non–platinum-based therapies and measurable disease per RECIST 1.1. First line patients were eligible if relapse occurred ≥3 months after prior (neo)adjuvant chemotherapy. Of a maximum 50 patients planned for enrollment, ≥30 were required to have BRCA1/2 germline wild-type status and basaloid molecular subtype tumors on central testing. Patients received intravenous cisplatin 75 mg/m2 on day 1 with intravenous M6620 140 mg/m2 on days 2 and 9 of each 21-day cycle. In patients intolerant of cisplatin or at investigator's discretion, cisplatin could be switched to carboplatin AUC 5 with M6620 90 mg/m2.

Results: At the time of abstract submission, 35 female patients were enrolled in this study; 18 patients with confirmed BRCA1/2 wild-type and basaloid metastatic TNBC who received ≥1 cycle of study drug and had ≥1 baseline scan and ≥1 on-treatment scan at the time of the data cut were included in the primary efficacy analysis. Median progression-free survival (PFS) was 4.1 months (90% CI, 1.6-6.9 months). PFS was ≥ 6 months in 2 patients and ≥ 3 months in 8 patients. Preliminary unconfirmed objective response [complete response or partial response (PR)] was observed in 38.9% (90% CI, 19.9%-60.8%) of patients. All 7 patients with preliminary objective response had PR as best overall response; the longest duration of response was 183 days. Response was ongoing in 4 patients with PR at the time of data cutoff. Grade ≥3 related treatment-emergent adverse events occurred in 16 of 35 patients: neutropenia (n=8), anemia (n=5), vomiting (n=4), nausea (n=3), and, in 1 patient each, thrombocytopenia, neutrophil count decreased, platelet count decreased, hypokalemia, generalized weakness, rigors, and acute kidney injury.

Conclusions: Combination of M6620 and cisplatin shows encouraging antitumor activity and tolerability in patients with advanced/metastatic TNBC. The study is ongoing; updated safety and efficacy results will be presented.

Citation Format: Telli ML, Lord S, Dean E, Abramson V, Arkenau H-T, Murias C, Becerra C, Tang R, Penney MS, Pollard J, Conboy G, Fields SZ, Shapiro G, Tolaney SM. ATR inhibitor M6620 (formerly VX-970) with cisplatin in metastatic triple-negative breast cancer: Preliminary results from a phase 1 dose expansion cohort (NCT02157792) [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT2-07-07.

Efficacy of Milbemax (milbemycin oxime + praziquantel) in the treatment of dogs experimentally infected with Crenosoma vulpis

Crenosoma vulpis, the fox lungworm, infects wild and domestic canids and is a cause of chronic respiratory disease in dogs in North America and Europe. The objective of this study was to determine the efficacy of milbemycin oxime (0.5mg/kg)/praziquantel (5mg/kg) (Milbemax; Novartis Animal Health, Inc.) against C. vulpis infection in a randomized, blinded, placebo-controlled study using experimentally infected dogs. Sixteen beagles (8 males, 8 females) were each given 100 infective third-stage larvae of C. vulpis. Fecal samples were examined for first-stage larvae by quantitative Baermann examination pre-exposure and at days 21, 28, 35, 42 and 49 post-infection (PI). All of the dogs were shedding larvae in the feces at 21 days PI. The dogs were randomly assigned to one of two groups. At 28 days PI, Group 1 (4 males, 4 females) received placebo only while Group 2 (4 males, 4 females) received a single treatment of milbemycin oxime (0.5mg/kg) and praziquantel (5mg/kg). The 16 dogs were euthanized and necropsied at 49 days PI. Lungs were removed, assessed for gross lesions (graded on a subjective scale 0-3 with 0 being normal) and C. vulpis were collected by lung-flush and counted. Samples of lung tissue were preserved for evaluation of histopathology and the lesions graded on a subjective scale (0-3 with 0 being normal). Gross and histopathology lesions were detected in all 8 untreated Group 1 dogs with mean subjective lesion scores of 1.8 ± 0.7 (range 1-3) and 3.0 ± 0.0 (range 3), respectively. Gross lesions were observed in 3/8 and histopathology lesions in all 8 of the treated Group 2 dogs with mean subjective lesion scores of 0.4 ± 0.5 (range 0-1) and 1.3 ± 0.4 (range 1-2), respectively. The mean (geometric) number for adult C. vulpis recovered in untreated dogs was 48.3 (range 25-70) compared with 0.65 (range 0-2) in animals treated with Milbemax. The resulting efficacy against C. vulpis was 98.7%. The number of C. vulpis was significantly lower for treated dogs than the burden in the untreated group (p=0.0002). A single dose of Milbemax (milbemycin oxime 0.5mg/kg+praziquantel 5mg/kg) was highly effective for the treatment of patent C. vulpis infection in dogs. A dosing interval for the prevention of clinical disease in dogs exposed to natural infections has not been established.

Natural infections of Crenosoma vulpis and Angiostrongylus vasorum in dogs in Atlantic Canada and their treatment with milbemycin oxime

Milbemycin oxime was used to treat dogs with natural infections of the fox lungworm, Crenosoma vulpis and the French heartworm, Angiostrongylus vasorum. Crenosomosis was identified in 42 of 202 dogs with clinical signs of coughing, dyspnoea or exercise intolerance by a Baermann analysis of faecal samples taken between October 2000 and October 2001. It occurred throughout Atlantic Canada (New Brunswick, Newfoundland, Nova Scotia and Prince Edward Island). The clinical signs resolved and shedding of larvae in faeces ceased in all 32 Crenosoma-infected dogs given a single oral dose of 0.5 mg/kg milbemycin oxime for which the results of faecal examinations were available. Angiostrongylosis was identified in 16 of the 202 dogs and was restricted to the Avalon peninsula of Newfoundland, where 67 dogs were tested. The clinical signs resolved and shedding of larvae ceased in 14 of the 16 dogs treated with four, weekly oral doses of 0.5 mg/kg milbemycin oxime. One dog with severe clinical signs died during the course of treatment and one owner failed to provide a faecal sample from their dog but reported that the clinical signs had resolved.

Evaluation of the repeatability of a crude adult indirect Ostertagia ostertagi ELISA and methods of expressing test results

An indirect enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies against Ostertagia ostertagi using a crude adult worm antigen was evaluated using serum and milk samples from adult cows, as well as from bulk tank milk. Within and between plate repeatabilities were determined. In addition, the effects of factors such as antigen batch, freezing, preserving of the samples and somatic cell counts (SCCs) of the samples were evaluated. Raw optical densities (ODs) and normalized values were compared using the concordance correlation coefficient (CCC), the coefficient of variation (CV), Bland-Altman plots (BA). Based on raw OD values, there was a high repeatability within a plate (CCC approximately 0.96 and CV<10%). Repeatability between plates was evaluated following normalization of OD values by four methods. Computing normalized values as (OD-Nt)/(Pst-Nt), gave the most repeatable results, with the CCC being approximately 0.95 and the CV approximately 11%. When the OD values were higher than 1.2 and 0.3 for the positive and the negative controls, respectively, none of the normalization methods evaluated provided highly repeatable results and it was necessary to repeat the test. Two batches of the crude antigen preparation were evaluated for repeatability, and no difference was found (CCC=0.96). The use of preservative (bronopol) did not affect test results, nor did freezing the samples for up to 8 months. A significant positive relationship between ELISA OD for milk samples and SCC score was found. Therefore, the use of composite milk samples, which have less variable SCC than samples taken from each quarter, would be more suitable when the udder health status is unknown. The analytical methods used to evaluate repeatability provided a practical way to select among normalization procedures.

Relationships between bulk-tank antibodies to Ostertagia ostertagi and herd-management practices and measures of milk production in Nova Scotia dairy herds

Monthly bulk-tank milk samples were obtained from 415 Nova Scotia dairy herds in each of the months of July-September 1998 and tested using an indirect microtitre ELISA against a crude saline-extract, whole-worm Ostertagia ostertagi antigen. ELISA results (optical densities (ODs)) were consistent across months (r=0.85) but there was considerable variation among herds. A questionnaire was sent by mail to all producers; information on management factors that would potentially influence parasite burdens in the herds was obtained from 239 farms. Data on annual milk production, summer milk production (July-September) and seasonal decline in milk production were obtained from the Animal Productivity and Health Information Network (APHIN) database. Associations between management practices and ODs, and between ODs and milk-production parameters were studied. Some management practices known to be associated with parasite burdens had expected directions of association with the ODs, giving supporting evidence that the ELISA is a reasonable measure of parasite burden. Most notably, ODs were increased with greater exposure of heifers or milking cows to pasture. ODs were not associated with either annual milk production or seasonal decline in milk production. However, there was a substantial relationship between the herd OD value and the level of milk production during the summer. An increase in the OD from 0.58 to 0.83 (the interquartile range of ODs) was associated with a reduction in production of 1.25kg/cow/day.

Interactive mortality factors in common loons from Maritime Canada

Between August 1992 and November 1995, 31 moribund or dead common loons (Gavia immer) found in the three Maritime provinces of Canada (New Brunswick, Nova Scotia, Prince Edward Island) were necropsied. Eight of these birds were in good body condition and died acutely from drowning or trauma. The remaining 23 birds were in poor body condition and had either chronic lead poisoning, respiratory mycosis, or oil contamination of their plumage. Loons in poor body condition had significantly higher numbers of intestinal trematodes and significantly higher levels of total renal mercury than loons in good body condition. Therefore, poor body condition in many loons was associated with two or more concurrent potential disease processes, although we could not establish a cause-effect relationship among these processes in individual birds. These results suggest that mortality in chronically ill wild animals can result from synergism among several potentially debilitating agents present in their environment.

Canine coccidiosis

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Trichinella spiralis in sylvatic hosts from Prince Edward Island

Larvae of Trichinella sp. were found in two of 208 red foxes (Vulpes vulpes) and one of 125 coyotes (Canis latrans) obtained from trappers from Prince Edward Island (Canada) in 1995 and 1996. A polymerase chain reaction based DNA biotyping method revealed the larvae to be isolates of Trichinella spiralis. This is the first verified identification of T. spiralis in sylvatic hosts from Canada.

Giardia

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Systemic nematodosis in farmed coho salmon in British Columbia

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Diagnostic parasitology

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A Drosophila gene expressed in the embryonic CNS shares one conserved domain with the mammalian GAP-43

By cross hybridization with the mammalian growth-related protein, GAP-43, we have isolated several Drosophila cDNAs and genomic sequences. These sequences correspond to a single copy gene that encodes two developmentally regulated transcripts 2.4 and 2.0 kb in length. The predicted protein sequence from the cDNAs contains a stretch of 20 amino acids closely related to the mammalian GAP-43 protein. These residues are also highly conserved in a cDNA isolated from the nematode C. elegans. Prior to dorsal closure, expression of the Drosophila gene is observed in non-neuronal tissues, especially in the mesectoderm and presumptive epidermis, both in a metameric pattern. After dorsal closure, expression becomes restricted to sets of cells that are segmentally reiterated along the periphery of the nervous system. These cells appear to include at least one specific set of glia that may establish scaffolding for the development of the longitudinal neuropile.

Dopaminergic neurotoxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in the mouse: an in vivo electrochemical study

The long-term (i.e., 4-5 months) effects of large doses (3 X 50 mg/kg) of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on striatal dopamine-containing afferents were studied in the NMRI strain of mice. Recently improved in vivo electrochemical methods were first used to examine the magnitude, spatial distribution and temporal dynamics of monoamine release initiated via local application of potassium in various regions of the mouse striatum. Immunohistochemical localization of tyrosine hydroxylase and computer-based image analysis were also used to quantitate regional catecholamine-containing nerve fiber densities in the caudate nucleus. The in vivo electrochemical studies showed a statistically significant decrease in the average potassium-evoked release of electroactive species from the MPTP-treated mouse caudate nucleus vs. control. Greater decreases in release were seen in dorsal than in ventral striatum (55% vs. 33%). The average rise time of potassium-evoked release was also significantly prolonged (greater than 50%) after MPTP pretreatment. Histochemical studies showed an overall reduction in the density of dopamine-containing terminals in the drug-treated mice, with a greater loss observed in the more dorsal regions of the caudate nucleus. The experimental data thus support a long-term selective destruction of dorsal vs. ventral dopamine-containing afferents to the striatum by the neurotoxin MPTP in mice.