A phase I dose-escalation study of enzalutamide in combination with the AKT inhibitor AZD5363 (capivasertib) in patients with metastatic castration-resistant prostate cancer

BACKGROUND

Activation of the PI3K/AKT/mTOR pathway through loss of phosphatase and tensin homolog (PTEN) occurs in approximately 50% of patients with metastatic castration-resistant prostate cancer (mCRPC). Recent evidence suggests that combined inhibition of the androgen receptor (AR) and AKT may be beneficial in mCRPC with PTEN loss.

PATIENTS AND METHODS

mCRPC patients who previously failed abiraterone and/or enzalutamide, received escalating doses of AZD5363 (capivasertib) starting at 320 mg twice daily (b.i.d.) given 4 days on and 3 days off, in combination with enzalutamide 160 mg daily. The co-primary endpoints were safety/tolerability and determining the maximum tolerated dose and recommended phase II dose; pharmacokinetics, antitumour activity, and exploratory biomarker analysis were also evaluated.

RESULTS

Sixteen patients were enrolled, 15 received study treatment and 13 were assessable for dose-limiting toxicities (DLTs). Patients were treated at 320, 400, and 480 mg b.i.d. dose levels of capivasertib. The recommended phase II dose identified for capivasertib was 400 mg b.i.d. with 1/6 patients experiencing a DLT (maculopapular rash) at this level. The most common grade ≥3 adverse events were hyperglycemia (26.7%) and rash (20%). Concomitant administration of enzalutamide significantly decreased plasma exposure of capivasertib, though this did not appear to impact pharmacodynamics. Three patients met the criteria for response (defined as prostate-specific antigen decline ≥50%, circulating tumour cell conversion, and/or radiological response). Responses were seen in patients with PTEN loss or activating mutations in AKT, low or absent AR-V7 expression, as well as those with an increase in phosphorylated extracellular signal-regulated kinase (pERK) in post-exposure samples.

CONCLUSIONS

The combination of capivasertib and enzalutamide is tolerable and has antitumour activity, with all responding patients harbouring aberrations in the PI3K/AKT/mTOR pathway.

CLINICAL TRIAL NUMBER

NCT02525068.

An Unexpected Cause of an Acute Hypersensitivity Reaction during Recovery from Anaesthesia

Acute hypersensitivity reactions to chlorhexidine in the operating room are probably more likely to occur during the early phases of anaesthesia because chlorhexidine is often used for cleaning the surgical field or during placement of indwelling catheters. We report a case of an acute hypersensitivity reaction that occurred in the post anaesthetic care unit. Subsequent skin testing suggested sensitivity to chlorhexidine, which had been applied over the vaginal mucosa at the end of surgery. Relevant issues in the investigation of acute hypersensitivity reactions in the post anaesthetic period are discussed.

Abstract P2-08-01: Analysis of PIK3CA mutation abundance in primary breast cancer with droplet digital PCR identifies frequent sub-clonal PIK3CA mutations in ER negative and / or HER2 positive breast cancer

Background: PIK3CA is the single most commonly mutated gene in breast cancer, with highest incidence reported in ER positive and HER2 negative breast cancer. Substantial data now suggests that breast cancers show intra-tumoural genetic heterogeneity, with apparently clonal tumours composed of multiple populations of tumour cells that, in addition to the founder genetic events common to all cells, harbour private genetic alterations. Tumours with mutations that are sub-clonal may respond less well to therapies targeting these mutations than cancers with clonal mutations. To assess how frequently PIK3CA mutations are clonal founder mutations, or may be subclonal, we assessed the abundance on PIK3CA mutation using digital PCR.

Methods: DNA was extracted from frozen sections of 119 primary breast cancers, following macrodissection to achieve tumour cell content of >70%. PIK3CA mutations c.1624G>A (E542K), c.1633G>A (E545K), c.3140A>T (H1047L) and c.3140A>G (H1047R) were assessed by droplet digital PCR on a BioRad QX100 system. Exon 9 mutation assays were optimised to not amplify the PIK3CA pseudogene. Mutational abundance was calculated from the Poisson distribution, expressed as the portion of PIK3CA DNA in the sample that was mutant, and compared between breast cancer subtypes. A mutational abundance of <20% was predefined to represent low abundance mutation, that may be subclonal.

Results: PIK3CA mutations were detected with abundance ranging from 80.4% to 0.0063%, with 26 cancers with an abundance >20% and 19 cancers with low abundance <20% (5 cancers with abundance 1-20%, and 14 cancer with abundance <1%). There was highly correlation between repeat experiments r2 = 0.98, p<0.0001, with 100% concordance for low abundance mutations in repeat analysis. High abundance mutations were numerically more common in ER positive HER2 negative cancers (18/65, 28%) than HER2 positive or triple negative (TN) cancers (7/54, 14% p = 0.07 Fishers exact test). Conversely, low abundance mutations were less common in ER positive HER2 negative cancers (4/65, 6%) than in HER2 positive or TN cancers (10/54, 19% p = 0.047). In cancers with a detectable PIK3CA mutation, mutational abundance was higher in ER positive cancer than ER negative cancers (p = 0.023 Mann-Whitney U test), and higher in ER positive HER2 negative cancers compared to HER2 positive or TN cancers (p = 0.0024). In ER positive HER2 negative cancers 82% (18/22) mutations were of high abundance, and likely clonal, whereas in TN or HER2 positive cancers 39% (7/18, p = 0.009) were of high abundance.

Conclusion: Our data suggests that hotspot PIK3CA mutations are frequently of low abundance in HER2 positive or TN breast cancer, and may be subclonal. However, we cannot exclude the possibility that these findings represent contamination. If confirmed on an independent data set, our data suggest that identification of mutational abundance may be an important component of PIK3CA mutation assessment and the potential targeting of these mutations with PI3 kinase inhibitors.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-08-01.

Integrative molecular and functional profiling of ERBB2-amplified breast cancers identifies new genetic dependencies

Overexpression of the receptor tyrosine kinase ERBB2 (also known as HER2) occurs in around 15% of breast cancers and is driven by amplification of the ERBB2 gene. ERBB2 amplification is a marker of poor prognosis, and although anti-ERBB2-targeted therapies have shown significant clinical benefit, de novo and acquired resistance remains an important problem. Genomic profiling has demonstrated that ERBB2+ve breast cancers are distinguished from ER+ve and 'triple-negative' breast cancers by harbouring not only the ERBB2 amplification on 17q12, but also a number of co-amplified genes on 17q12 and amplification events on other chromosomes. Some of these genes may have important roles in influencing clinical outcome, and could represent genetic dependencies in ERBB2+ve cancers and therefore potential therapeutic targets. Here, we describe an integrated genomic, gene expression and functional analysis to determine whether the genes present within amplicons are critical for the survival of ERBB2+ve breast tumour cells. We show that only a fraction of the ERBB2-amplified breast tumour lines are truly addicted to the ERBB2 oncogene at the mRNA level and display a heterogeneous set of additional genetic dependencies. These include an addiction to the transcription factor gene TFAP2C when it is amplified and overexpressed, suggesting that TFAP2C represents a genetic dependency in some ERBB2+ve breast cancer cells.

An Investigation into a Panel of Isogenic Taxane Resistant Breast Cancer Cell Lines Using Transcriptomic and Genomic Methods

Background: Taxanes are a powerful chemotherapeutics used to treat breast cancer. Taxane resistance has become increasingly more prevalent in the clinic; This problem is exacerbated by a lack of understanding of mechanisms underlying taxane resistance.Materials and Methods: 3 isogenic breast cancer cell-line panels: paclitaxel resistant (PACR) MDA-MB-231s/ZR75-1s and docetaxel resistant (DOCR) ZR75-1s were derived by culturing cells in incrementally escalating doses of taxanes over time. MDA-MB-231: native, 5nM, 25nM and 100nM PACR cells, ZR75-1: native, and 5nM, 25nM, and 50nM PACR and ZR75-1: native, and 5nM, 25nM and 50nM DOCR cells were analysed. RNA from native and PACR MDA-MB-231 cell lines was analysed on the Illumina® human ref.8V2 chip. Data were analysed using IlluminaGui. For aCGH, DNA was extracted from MDA-MB-231 PACR, ZR75-1 PACR and DOCR and respective parental lines, labelled and hybridised to a tiling path BAC microarray (resolution ∼50kb). Each cell-line was tested against reference samples of DNA from pooled female blood. Taxane resistant cells were tested against their parental cell line.Results: Illumina data demonstrated that resistance to increasing doses of paclitaxel is associated with sequential increases in mRNA dysregulation in MDA-MB-231 cells.A number of comparisons between the illumina data of native and the PACR cells were made using a p value of P≤0.001. The first comparison made using the illumina data, was between the 5nM PACR cells and the native cell lines: 25 significantly up or downregulated genes were identified. When the 25nM PACR cells were compared to the native cell lines, 225 genes were found to be significantly up or downregulated. Finally, when 100nM PACR cells were compared to native cells, 425 genes were found to be significantly up or downregulated. A group of genes identified that were common to multiple paclitaxel resistant groups included candidates such as YY1, AURKA and CCND2. aCGH has identified significant differences in patterns of copy number loss, gain and amplification in the taxane resistant cell lines, including chromosome loss of 6p and gain of 2p. Illumina and aCGH data were overlaid using specially designed algorithms.Discussion: Both aCGH and expression arrays highlight a progressive acquisition of molecular and transcriptomic alterations in isogenic breast cancer cell lines resistant to increasing doses of taxanes. Further mapping of transcriptomic and genomic profiles will enable identification of key molecular targets for restoration of taxane sensitivity. Genes upregulated in taxane resistant clones identified in the illumina experiment, in particular those whose upregulation is underpinned by DNA copy number gains in resistant cells, may represent genes which may be targeted with inhibitors to test potential candidates for reversing taxane resistance.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 1134.

Integrative Molecular Profiling of Triple Negative Breast Cancers Identifies Potential Therapeutic Targets Including Amplifications of FGFR2

Triple negative breast cancers (TNBCs) have a relatively poor prognosis emphasising the need to identify new subtype specific target therapies. Based on the concept of oncogene addiction, we searched for potential therapeutic targets by identifying genes consistently over-expressed when amplified in TNBC. Fifty six TNBCs were subjected to high resolution tiling path microarray-based comparative genomic hybridisation (aCGH); out of these cases, 24 were also subjected to genome-wide microarray-based mRNA expression analysis. TNBCs showed a high level of genetic instability, with recurrent regions of amplification (>4 copies) included multiple regions on 1q and 8q, 3q25, 10p14, 10q26, 13q34, 15q26 and 19q12-19q13. Integration of aCGH and expression data revealed 38 genes that were significantly overexpressed when amplified. This list includes known oncogenes and potential therapeutic targets, such as MCL1 (1q21.2), FGFR2 (10q26.3), BUB3 (10q26.3), RAB20 (13q34), PKN1 (19p13.12), and NOTCH3 (19p13.12). To validate FGFR2 as a therapeutic target, we screened a panel of cell lines, by western blotting and aCGH, and identified two TNBC cell lines with FGFR2 amplification. In these cell lines FGFR2 was constitutively active in a ligand independent manner, and RNA interference-mediated silencing of FGFR2 selectively decreased survival of cell lines harbouring FGFR2 amplification. Likewise FGFR2 amplified cell lines were highly sensitive to FGFR tyrosine kinase inhibitor PD173074 (IC50 <20nM). Treatment with PD173074 induced apoptosis in amplified cell lines, as did treatment with PI3 kinase inhibitors LY294002 and BEZ-235 suggesting that apoptosis resulted from inhibition of AKT signalling. Examination of publically available CGH data sets confirmed FGFR2 amplification in 4% (5/124 95%CI 1.3-9.2%) of TNBC, with no cases of FGFR2 amplification in other subtypes (0/150, p=0.02). Our results suggest that FGFR2 amplification is a therapeutic target in a small subset of TNBCs.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3147.

Use of the Internet for patient care: a nationwide survey of Australian anaesthetists

The internet is an increasingly important source of information for anaesthetists. We sought to determine the extent and patterns of internet use among Australian anaesthetists, and to assess its effect on clinical decision-making. A postal survey of all Australian Fellows of the Australian and New Zealand College of Anaesthetists (n = 2344) was performed. The response rate was 48% (n = 1109) and 1066 responses were analysed. Ninety-seven per cent of respondents, much higher than the national average of 72%, had internet access at work or home. The majority used the internet at least once a month for patient care, and over 50% had made clinical decisions influenced by information found on the internet. In contrast, less than 20% had had any training in its use. In terms of access, rural Australia did not appear to be disadvantaged.

The in-vitro effects of sevoflurane and desflurane on the contractility of pregnant human uterine muscle

The effect of desflurane and sevoflurane on the contractility of the uterus was examined in vitro on strips of human myometrium obtained at the time of elective cesarean section. Small strips (1 mm x 2 mm x 10 mm) of muscle were prepared and suspended in an organ bath containing oxygenated physiological saline. Force of contraction was recorded continuously using an isometric tension transducer. Following the onset of regular spontaneous contractions, baseline measurements were obtained and the strips were exposed to varying concentrations of sevoflurane or desflurane corresponding to 0.5, 1.0 and 1.5 minimum alveolar concentration (MAC). Sevoflurane depressed contractility to 72 +/- 18% of control at 0.5 MAC, 37 +/- 15% at 1.0 MAC and 27 +/- 16% at 1.5 MAC compared with 65 +/- 14 of control at 0.5 MAC, 43 +/- 18% at 1.0 MAC and 22 +/- 11% at 1.5 MAC for desflurane. The degree of depression of uterine muscle contractility produced by both these agents was significantly different from control at all concentrations. In conclusion, both sevoflurane and desflurane depress the contractility of isolated pregnant human myometrium at concentrations of 0.5, 1.0 and 1.5 MAC. These agents produce a similar degree of depression of uterine muscle contractility.