A first-in-human phase I study of 4SC-201, an oral histone deacetylase (HDAC) inhibitor, in patients with advanced solid tumors

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Background: 4SC-201 (former code BYK408740) is a specific, potent, pan-HDAC inhibitor with improved ADME properties. Methods: Patients (pts) with advanced refractory solid tumors were dosed once daily (QD) d1–5 in a 14-day cycle in sequential cohorts of 3–6 pts with 50 or 100% dose increments. Primary objectives were to determine safety, tolerability, pharmacokinetics (PK) and maximum tolerated dose (MTD) of 4SC-201. Pharmacodynamic assessment (histone acetylation and HDAC enzyme activity) and anti-tumor efficacy were secondary objectives. Blood samples for PK and PD were taken on days 1, 5 and 47 of treatment. Results: 18 pts (9M/9F) with a median age of 58.5 yrs (range 40–70) were treated at five dose levels: 3 pts each at 100mg, 200mg, 400mg and 600mg and 6 pts at 800mg. All pts were evaluable for toxicity and received at least 2 treatment cycles. Grade 3 DLT of nausea and vomiting occurred in 1 pt dosed at 800mg. Most common adverse events included nausea, vomiting and fatigue. 8 of 9 pts treated in the 600mg and 800mg cohorts had stable disease during the main phase of the study (4 treatment cycles). A patient with liposarcoma and another with thymoma (marginal response) continued treatment beyond 6 months. PK parameters were dose-proportional with a low inter-individual variability and indicated good bioavailability. The apparent t1/2 of oral 4SC-201 ranged from 2.3 to 4.4 hours. The degree of HDAC inhibition measured in a peripheral blood mononuclear cell functional assay was dose- dependent and increased from 50 to 100 %, although histone H4 acetylation accumulation after dosing did not differ significantly between dose levels. Conclusions: Oral 4SC-201 has favorable disposition and can be safely administered; 600mg QD d1–5 in a 14-day cycle is recommended for phase II evaluation. Safely administered doses modulate target with antitumor activity.

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CYP17 blockade by abiraterone: further evidence for frequent continued hormone-dependence in castration-resistant prostate cancer

The limited prognosis of patients with castration-resistant prostate cancer (CRPC) on existing hormonal manipulation therapies calls out for the urgent need for new management strategies. The novel, orally available, small-molecule compound, abiraterone acetate, is undergoing evaluation in early clinical trials and emerging data have shown that the selective, irreversible and continuous inhibition of CYP17 is safe with durable responses in CRPC. Importantly, these efficacy data along with strong preclinical evidence indicate that a significant proportion of CRPC remains dependant on ligand-activated androgen receptor (AR) signalling. Coupled with the use of innovative biological molecular techniques, including the characterisation of circulating tumour cells and ETS gene fusion analyses, we have gained insights into the molecular basis of CRPC. We envision that a better understanding of the mechanisms underlying resistance to abiraterone acetate, as well as the development of validated predictive and intermediate endpoint biomarkers to aid both patient selection and monitor response to treatment, will improve the outcome of CRPC patients.

Circulating tumour cell (CTC) counts as intermediate end points in castration-resistant prostate cancer (CRPC): a single-centre experience

BACKGROUND

The purpose of this study was to evaluate the association of circulating tumour cell (CTC) counts, before and after commencing treatment, with overall survival (OS) in patients with castration-resistant prostate cancer (CRPC).

EXPERIMENTAL DESIGN

A 7.5 ml of blood was collected before and after treatment in 119 patients with CRPC. CTCs were enumerated using the CellSearchSystem.

RESULTS

Higher CTC counts associated with baseline characteristics portending aggressive disease. Multivariate analyses indicated that a CTC >or=5 was an independent prognostic factor at all time points evaluated. Patients with baseline CTC >or=5 had shorter OS than those with <5 [median OS 19.5 versus >30 months, hazard ratio (HR) 3.25, P=0.012]; patients with CTC >50 had a poorer OS than those with CTCs 5-50 (median OS 6.3 versus 21.1 months, HR 4.1, P<0.001). Patients whose CTC counts reduced from >or=5 at baseline to <5 following treatment had a better OS compared with those who did not. CTC counts showed a similar, but earlier and independent, ability to time to disease progression to predict OS.

CONCLUSION

CTC counts predict OS and provide independent prognostic information to time to disease progression; CTC dynamics following therapy need to be evaluated as an intermediate end point of outcome in randomised phase III trials.

Dissecting prostate carcinogenesis through ETS gene rearrangement studies: implications for anticancer drug development

The discovery of ETS gene fusions as common events in prostate cancer represents a paradigmatic shift in the significance attributed to chromosomal translocations as a key mechanistic player in carcinogenesis. However, these chromosomal fusion events are poorly understood, as their functional significance and therapeutic potential remain unclear. Nonetheless, they have generally been used as novel molecular handles to sub-categorise the broad diversity of prostate cancers mainly via the use of fluorescence in-situ hybridisation-based "break-apart assays". Thus, the potential roles of these ETS gene fusion events are being actively explored and are discussed in this review within the context of the existing scientific and clinical climates. Examples include their possible utilities as screening tools, markers for risk stratification and predictors of responses to therapies (in particular hormonal manipulation), biomarkers to guide early phase clinical trials, as well as therapeutic targets. Work is ongoing to address the many questions surrounding these pursuits in a very rapidly evolving area of research, and it is believed that an improved understanding of the biology underpinning these genetic events is vital in order to optimise their use in anticancer drug development.