A small molecule inhibitor of XIAP induces apoptosis and synergises with vinorelbine and cisplatin in NSCLC

Background:

Evasion of apoptosis contributes to the pathogenesis of solid tumours including non-small cell lung cancer (NSCLC). Malignant cells resist apoptosis through over-expression of inhibitor of apoptosis proteins (IAPs), such as X-linked IAP (XIAP).

Methods:

A phenylurea-based small molecule inhibitor of XIAP, XIAP antagonist compound (XAC) 1396-11, was investigated preclincally to determine its ability to sensitise to clinically relevant cytotoxics, potentially allowing dose reduction while maintaining therapeutic efficacy.

Results:

XIAP protein expression was detected in six NSCLC cell lines examined. The cytotoxicity of XAC 1396-11 against cultured NSCLC cell lines in vitro was concentration- and time-dependent in both short-term and clonogenic assays. XAC 1396-11-induced apoptosis was confirmed by PARP cleavage and characteristic nuclear morphology. XAC 1396-11 synergised with vinorelbine±cisplatin in H460 and A549 NSCLC cells. The mechanism of synergy was enhanced apoptosis, shown by increased cleavage of caspase-3 and PARP and by the reversal of synergy by a pan-caspase inhibitor. Synergy between XAC 1396-11 and vinorelbine was augmented by optimising drug scheduling with superior effects when XAC 1396-11 was administered before vinorelbine.

Conclusion:

These preclinical data suggest that XIAP inhibition in combination with vinorelbine holds potential as a therapeutic strategy in NSCLC.

Detection of BRAF mutations in the tumour and serum of patients enrolled in the AZD6244 (ARRY-142886) advanced melanoma phase II study

Background:

This study investigated the potential clinical utility of circulating free DNA (cfDNA) as a source of BRAF mutation detection in patients enrolled into a phase II study of AZD6244, a specific MEK1/2 inhibitor, in patients with advanced melanoma.

Methods:

BRAF mutations were detected using Amplification Refractory Mutation System allele-specific PCR. BRAF mutation status was assessed in serum-derived cfDNA from 126 patients enrolled into the study and from 94 matched tumour samples.

Results:

Of 94 tumour samples, 45 (47.9%) were found to be BRAF mutation positive (BRAF+). Serum-derived cfDNA was BRAF+ in 33 of 126 (26.2%) samples, including in five samples for which tumour data were unavailable. Of BRAF+ tumours, 25 of 45 (55.6%) were BRAF+ in cfDNA. In three cases in which the tumour was negative, cfDNA was BRAF+. Progression-free survival (PFS) of patients with BRAF+ tumour and cfDNA was not significantly different compared with tumour BRAF+ but cfDNA BRAF-negative patients, indicating that cfDNA BRAF detection is not associated with poorer prognosis on PFS in stage III/IV advanced melanoma.

Conclusions:

These data demonstrate the feasibility of BRAF mutation detection in cfDNA of patients with advanced melanoma. Future studies should aim to incorporate BRAF mutation testing in cfDNA to further validate this biomarker for patient selection.

Safety, tolerability, pharmacokinetics and pharmacodynamics of the oral cyclin-dependent kinase inhibitor AZD5438 when administered at intermittent and continuous dosing schedules in patients with advanced solid tumours

BACKGROUND

AZD5438 is an orally bioavailable inhibitor of cyclin E-cdk2, cyclin A-cdk2 and cyclin B-cdk1 complexes. Three phase I studies assessed the clinical safety, tolerability, pharmacokinetics and pharmacodynamics of AZD5438 when administered in different dosing schedules.

PATIENTS AND METHODS

AZD5438 was administered four times daily, once every 7 days (study 1), for 14 consecutive days followed by 7 days of rest (study 2), or continuously (study 3), to patients with advanced solid tumours. Dose escalation proceeded until the emergence of dose-limiting toxic effects.

RESULTS

Sixty-four patients were included across the three studies (19, 17 and 28, respectively). Nausea and vomiting were the most common adverse events. When dosed continuously, 40 mg four times daily was considered intolerable, and due to safety issues, all studies were terminated prematurely. Consequently, no intolerable dose was identified during the weekly schedule. Pharmacokinetics demonstrated dose-proportional exposure, high interpatient variability and accumulation after multiple doses. Skin biopsies indicated reduced retinoblastoma protein phosphorylation at cdk2 phospho-sites; other pharmacodynamic assessments did not reveal consistent trends.

CONCLUSIONS

AZD5438 was generally well tolerated in a weekly dosing schedule, but not in continuous schedules. The clinical development programme for AZD5438 was discontinued owing to tolerability and exposure data from these studies.

Microdosing imaging pharmacokinetic (PK) study of the antisense oligonucleotide (ASO) to survivin (LY2181308) using positron emission tomography (PET): A novel paradigm in clinical drug development

3578

Background: Survivin, an inhibitor of an apoptosis protein, widely overexpressed in cancer is associated with poor clinical outcome. We performed the first worldwide human microdosing imaging PK study of an ASO with LY2181308, a specific, second generation antisense inhibitor of Survivin using carbon-11 radiolabelled LY2181308 ([11C]LY2181308). Methods: LY2181308 was administered at the recommended phase II dose (750 mg over 3 hours IV daily x 3, then once weekly). [11C]LY2181308 was manufactured to GMP standard by random [11C]methylation with [11C]methyl iodide of LY2181308 using a GE Tracerlab FXc molecule. [11C]LY2181308-PET scans were performed at baseline and during treatment infusion. [11C]LY2181308 uptake in normal tissue and tumour was quantified. Results: Three pts (2 female Caucasian/1 male Asian) were scanned after administering [11C]LY2181308 which delivered (135–376 μg) of LY2181308. Despite its large size (6778 amu), [11C]LY2181308 rapidly distributed to tissues, with maximal uptake in kidney followed by liver, spleen, vertebral body, tumour, spinal cord, lung, and muscle at baseline. Although renal uptake was high, urinary elimination (bladder activity) was low suggesting renal trapping of [11C]LY2181308 at baseline. For a normalised injected dose of 1 mg, mean (range) tumour concentrations of 31 (4–41) ng/ml were observed at baseline, consistent with that predicted from the preclinical PK/PD model. In a pt with mesothelioma who also had a second [11C]LY2181308-PET scan during LY2181308 treatment infusion, there was about 2-fold increase in [11C]LY2181308 tumour uptake, in contrast to markedly reduced uptake in kidneys, liver, and spleen and similar aortic (circulatory) [11C]LY2181308 levels. In this patient, tumour [18F]FDG- PET uptake at 28 days was reduced by up to 40% after treatment, suggesting drug activity. Conclusions: [11C]LY2181308 pharmacokinetics suggest biologically active human tumour drug concentrations can be attained. LY2181308 therapy saturated normal tissue kinetics and increased tumour uptake of [11C]LY2181308. Data uniquely obtained from fully regulated microdosing studies may rationalise and hasten drug development.

[Table: see text]

Pharmacodynamic (PD) evaluation of LY2181308 in patients with metastatic malignancies

3507

Background: Survivin is an inhibitor of apoptosis and its overexpression in cancer has been associated with poor survival. LY2181308 (LY), a novel modified antisense oligonucleotide is a specific inhibitor of survivin. The safety and PK profile of LY from this first-in-human study was presented at ASCO 2008. We now present the PD data from this trial. Methods: Patients with advanced or metastatic malignancies who had failed previous anti-tumor treatments were enrolled. Three consecutive IV loading doses given over 3 hours were followed by weekly maintenance doses. Pre- and post-dosing biopsies were mandated to test for evidence of modification of the target at doses where a PD effect was expected. Biopsies were taken 48 hours after the last loading dose by CT-guided fine needle biopsy. Tumor tissue was paraffin-embedded for immunohistochemistry (IHC) and survivin gene expression. Given the finite amount of biopsy material, the quantification of survivin protein was prioritized. In addition, at one site, pre- and post-dosing endobronchial sampling was conducted in NSCLC patients, with the aim of quantifying levels of native survivin protein, and assessing changes in cell cycle profile in freshly isolated tumor cells using FACS analysis. Results: Out of the 34 patients enrolled, 22 patients had a pre- and posttreatment biopsy. Results from IHC indicated that survivin expression was reduced in the nucleus and cytoplasm in 11/17 and 5/14 evaluable pairs, respectively. LY was detected in neoplastic and non-neoplastic tumor cells in 5/16 and 15/16 evaluable pairs respectively. Gene expression analysis indicated a reduction in survivin expression by 20% to 50% in 11/15 evaluable pairs. Analysis of the fresh tumor material from endobronchial sampling revealed that 2 out of 3 patients with NSCLC had a near-complete elimination of survivin-positive cells accompanied by an increase in the fraction of cells with a sub-G1 DNA content, consistent with cell death. Conclusions: In this study, we were able to demonstrate the presence of the ASO in tumor tissue and confirm a reduction in survivin protein and gene expression. These findings demonstrate the proof of principle of antitumor activity of LY and provide the rationale for phase II studies.

[Table: see text]

The CD-loop of PAI-2 (SERPINB2) is redundant in the targeting, inhibition and clearance of cell surface uPA activity

BACKGROUND

Plasminogen activator inhibitor type-2 (PAI-2, SERPINB2) is an irreversible, specific inhibitor of the urokinase plasminogen activator (uPA). Since overexpression of uPA at the surface of cancer cells is linked to malignancy, targeting of uPA by exogenous recombinant PAI-2 has been proposed as the basis of potential cancer therapies. To this end, reproducible yields of high purity protein that maintains this targeting ability is required. Herein we validate the use in vitro of recombinant 6 x His-tagged-PAI-2 lacking the intrahelical loop between C and D alpha-helices (PAI-2 Delta CD-loop) for these purposes.

RESULTS

We show that PAI-2 Delta CD-loop expressed and purified from the pQE9 vector system presents an easier purification target than the previously used pET15b system. Additionally, PAI-2 Delta CD-loop gave both higher yield and purity than wild-type PAI-2 expressed and purified under identical conditions. Importantly, absence of the CD-loop had no impact on the inhibition of both solution phase and cell surface uPA or on the clearance of receptor bound uPA from the cell surface. Furthermore, uPA:PAI-2 Delta CD-loop complexes had similar binding kinetics (KD approximately 5 nM) with the endocytosis receptor Very Low Density Lipoprotein Receptor (VLDLR) to that previously published for uPA:PAI-2 complexes.

CONCLUSION

We demonstrate that the CD-loop is redundant for the purposes of cellular uPA inhibition and cell surface clearance (endocytosis) and is thus suitable for the development of anti-uPA targeted cancer therapeutics.

A phase I study of extended dosing with lomeguatrib with temozolomide in patients with advanced melanoma

Lomeguatrib, an O⁶-methylguanine-DNA methyltransferase inactivator, was evaluated in an extended dosing regimen with temozolomide, designed according to pharmacodynamic data from previous studies. Patients with unresectable stage 3 or 4 cutaneous or unknown primary melanoma metastases were treated with lomeguatrib 40 mg, b.i.d. for 10 or 14 days and temozolomide 75–100 mg m⁻² on days 1–5. Drugs were administered orally with cycles repeated every 28 days, for up to six cycles. A total of 32 patients were recruited to the study. Lomeguatrib for 10 days with temozolomide 75 mg m⁻² was established as the optimal extended lomeguatrib dosing schedule, with haematological toxicity being dose limiting. There were two partial responses to treatment giving an overall response rate of 6.25%. Extending lomeguatrib administration beyond that of temozolomide requires a reduced dose of the latter agent. Only limited clinical activity was seen, suggesting no advantage for this regimen over conventional temozolomide administration in the treatment of melanoma.

Plasminogen activator inhibitor type 2 inhibits cell surface associated tissue plasminogen activator in vitro: potential receptor interactions

Regulation of cellular plasminogen activation is necessary for maintenance of tissue homeostasis. Despite increasing evidence for co-expression of tissue type plasminogen activator (tPA) and plasminogen activator inhibitor type-2 (PAI-2; SERPINB2) under patho/physiological conditions, the inhibition of cell-bound tPA mediated plasminogen activation by PAI-2 has not been addressed. Here we show that PAI-2 can inhibit cell-bound tPA activity in vitro and thus prevent plasmin formation. We also examined the potential involvement in this inhibition of the annexin II heterotetramer (AIIt), one of the many well characterized cell-surface co/receptors for tPA and plasminogen that efficiently promotes plasminogen activation. This receptor was of interest because AIIt has also been shown to directly bind PAI-2. Characterization of these potential interactions using purified protein systems revealed that PAI-2 directly bound AIIt via the p11 (S100A10) subunit. However, PAI-2 prevented AIIt/tPA-mediated plasminogen activation by its classic serpin inhibitory activity rather than through competition with tPA/plasminogen for binding. Further analysis showed that PAI-2 inhibited cell bound tPA-induced plasmin activity in both an AIIt-dependent and -independent manner. These data open new possibilities for further investigations regarding the regulation of cellular plasmin generation in vivo, especially in tissues where PAI-2 and tPA may be co-expressed.

Revisiting the biological roles of PAI2 (SERPINB2) in cancer

Tumour expression of the urokinase plasminogen activator correlates with invasive capacity. Consequently, inhibition of this serine protease by physiological inhibitors should decrease invasion and metastasis. However, of the two main urokinase inhibitors, high tumour levels of the type 1 inhibitor actually promote tumour progression, whereas high levels of the type 2 inhibitor decrease tumour growth and metastasis. We propose that the basis of this apparently paradoxical action of two similar serine protease inhibitors lies in key structural differences controlling interactions with components of the extracellular matrix and endocytosis-signalling co-receptors.

A phase II trial of lomeguatrib and temozolomide in metastatic colorectal cancer

To evaluate the tumour response to lomeguatrib and temozolomide (TMZ) administered for 5 consecutive days every 4 weeks in patients with metastatic colorectal carcinoma. Patients with stage IV metastatic colorectal carcinoma received lomeguatrib (40 mg) and TMZ (50–200 mg m⁻²) orally for 5 consecutive days every 4 weeks. Response was determined every two cycles. Pharmacokinetics of lomeguatrib and TMZ as well as their pharmacodynamic effects in peripheral blood mononuclear cells (PBMC) were determined. Nineteen patients received 49 cycles of treatments. Despite consistent depletion of O⁶-methylguanine-DNA methyltransferase in PBMC, none of the patients responded to treatment. Three patients had stable disease, one for the duration of the study, and no fall in carcinoembryonic antigen was observed in any patient. Median time to progression was 50 days. The commonest adverse effects were gastrointestinal and haematological and these were comparable to those of TMZ when given alone. This combination of lomeguatrib and TMZ is not efficacious in metastatic colorectal cancer. If further studies are to be performed, emerging data suggest that higher daily doses of lomeguatrib and a dosing period beyond that of TMZ should be evaluated.

Peptides and small molecules targeting the plasminogen activation system: towards prophylactic anti-metastasis drugs for breast cancer

Breast cancer is the most common malignancy afflicting Western women today and is responsible for many deaths due to metastatic disease. Upregulation of the plasminogen-activation system (PAS) has been shown to correlate with poor prognosis in metastatic breast cancer and targeting this system represents an attractive strategy for the development of anti-metastasis prophylactic drugs. Two promising classes of PAS-targeting agents are inhibitors of the serine protease activity of urokinase plasminogen activator (uPA) and antagonists of the interaction of uPA with its cell surface receptor (uPAR). This review begins with a brief overview of the role of PAS in cancer metastasis before describing in detail a subset of the small molecules and peptides from the patent literature that target either uPA activity or uPA/uPAR interactions for use as anti-metastasis drugs.

Optimisation of circulating biomarkers of cell death for routine clinical use

BACKGROUND

M30 and M65 enzyme-linked immunosorbent assays detect circulating cytokeratin 18 fragments released during caspase-dependent or total cell death, respectively, and have potential as biomarkers in epithelial cancers. While these assays have been validated, their robustness for routine clinical use is unknown.

PATIENTS AND METHODS

M30 and M65 were measured in matched serum and plasma samples from 31 lung cancer patients and 18 controls.

RESULTS

Time allowable between sample acquisition and processing is critical for assays in clinical use. A 4-h delay in processing at room temperature increased M30 (P < 0.0001), an effect minimised by incubation on ice. M30 and M65 in serum were resistant to processing variations including delays. Serum and plasma measurements correlated well although M30 but not M65 was lower in serum (P < 0.0005). Less variation between duplicate assays was observed in serum. Prolonged storage (-80 degrees C) led to increased M30 (12%, 6 months; 34%, 1 year). Sample dilution in the supplied assay diluent proved non-linear, whereas dilution in donor serum or porcine plasma restored linearity up to a ratio of 1 : 6.

CONCLUSION

We present recommendations that improve the reliability of these assays for clinical use and recommend serum as the preferred matrix with data more resistant to variations in collection.

IAPs as a target for anticancer therapy

The avoidance of apoptosis is one of the hallmarks of cancer cells. In addition, failure to induce apoptosis by anticancer agents, either due to limitations of the drug or the tumour cell evading apoptosis, is a reason for chemotherapeutic failure. Two general pathways for apoptotic cell death have been characterised, the extrinsic and intrinsic pathways which merge in the final common pathway. X-linked inhibitor of apoptosis protein (XIAP) is an anti-apoptotic protein in the final common pathway that inhibits caspases and suppresses apoptosis. XIAP is over-expressed in many cancer cell lines and cancer tissues. High XIAP expression has been correlated with resistance to chemotherapy and radiotherapy and to poor clinical outcome by some investigators. Manipulation of apoptosis is an attractive therapeutic concept. Much effort has been spent on inhibiting the anti-apoptotic protein, B cell lymphoma gene 2 (Bcl-2) which is part of the intrinsic pathway. Now attention is turning to inhibition of XIAP as a cancer drug target. It has been argued that it is more effective to block the final common pathway rather than just the intrinsic arm. Inhibition of XIAP can be with either antisense oligonucleotides (ASO) or small molecule inhibitors. In vitro, XIAP antagonists produce XIAP knockdown and apoptosis which is associated with sensitisation of tumour cells to radiotherapy and cytotoxic drugs. In vivo, XIAP antagonists have antitumour effects and sensitise tumours to the effects of chemotherapy. This review will summarise the preclinical data for both ASO and small molecule inhibition of XIAP and discuss emerging Phase I data. Future strategies for manipulation of XIAP and the clinical development of XIAP inhibitors will be discussed.

N-phenethyl and N-naphthylmethyl isatins and analogues as in vitro cytotoxic agents

A range of N-phenethyl, N-phenacyl, and N-(1- and 2-naphthylmethyl) derivatives of 5,7-dibromoisatin 2 were prepared by N-alkylation reactions. Their activity against human monocyte-like histiocytic lymphoma (U937), leukemia (Jurkat), and breast carcinoma (MDA-MB-231) cell lines was assessed. The results allowed further development of structure-activity relationships. The compound 5,7-dibromo-N-(1-naphthylmethyl)-1H-indole-2,3-dione 5a was the most potent against U937 cells with an IC(50) value of 0.19 microM.

A structural basis for differential cell signalling by PAI-1 and PAI-2 in breast cancer cells

PAI-1 and PAI-2 (plasminogen-activator inibitor types 1 and 2) are inhibitors of cell surface uPA (urokinase plasminogen activator). However, tumour expression of PAI-1 and PAI-2 correlates with poor compared with good patient prognosis in breast cancer respectively. This biological divergence may be related to additional functional roles of PAI-1. For example, the inhibition of uPA by PAI-1 reveals a cryptic high-affinity site within the PAI-1 moiety for the VLDLr (very-low-density-lipoprotein receptor), which sustains cell signalling events initiated by binding of uPA to its receptor. These interactions and subsequent signalling events promote proliferation of breast cancer cells. Biochemical and structural analyses show that, unlike PAI-1, the PAI-2 moiety of uPA-PAI-2 does not contain a high-affinity-binding site for VLDLr, although uPA-PAI-2 is still efficiently endocytosed via this receptor in breast cancer cells. Furthermore, global protein tyrosine phosphorylation events were not sustained by uPA-PAI-2 and cell proliferation was not affected. We thus propose a structurally based mechanism for these differences between PAI-1 and PAI-2 and suggest that PAI-2 is able to inhibit and clear uPA activity without initiating mitogenic signalling events through VLDLr.