The combination of a chemotherapy doublet (gemcitabine and capecitabine) with a biological doublet (bevacizumab and erlotinib) in patients with advanced pancreatic adenocarcinoma. The results of a phase I/II study

BACKGROUND

Preclinical data support the combined inhibition of vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFR) pathways in the treatment of pancreatic cancer. Following a dose finding phase I study the efficacy and toxicity of a four-drug regimen utilising the cytotoxic doublet of gemcitabine and capecitabine (GemCap), with the biological doublet of erlotinib and bevacizumab were further assessed in patients with advanced pancreatic cancer.

PATIENTS AND METHODS

In a phase II expansion cohort, patients with chemonaive locally advanced or metastatic pancreatic cancer received gemcitabine (1000mg/m(2) D1, 8, 15), capecitabine (1400mg/m(2) D1-21), erlotinib (100mg daily) and bevacizumab (5mg/kg D1, 15) every 28days. The primary endpoint was radiological response rate by response evaluation criteria in solid tumours (RECIST). Computed tomography (CT) assessment was performed every 8weeks. Consolidation radiotherapy was considered in locally advanced patients following six cycles of treatment.

RESULTS

In total 44 patients (phases I & II) were recruited. The median cycles delivered were 6 (range 1-16). Confirmed radiological responses were seen in 23% (95% confidence interval (CI): 11-38%) of patients. The median progression-free and overall survival for the entire cohort was 8.4 and 12.6months, respectively. In patients with metastatic disease the median overall survival was 10.1months. Common grade 3/4 toxicities were; neutropenia 52%, lethargy 32%, diarrhoea 18% and hand-foot syndrome 18%.

CONCLUSION

The combination of gemcitabine, capecitabine, erlotinib and bevacizumab was feasible with a manageable toxicity profile and demonstrated encouraging efficacy data in a good performance status population.

A phase II study of the anti-IGFR antibody MK-0646 in combination with cetuximab and irinotecan in the treatment of chemorefractory metastatic colorectal cancer

4127

Background: Evidence of cross-talk between EGFR and IGFR signaling pathways provide a logical rationale for combining anti-EGFR and anti-IGFR strategies in the treatment of cancer. Prior to commencing a blinded randomised phase II study, an opened-labelled safety run-in was undertaken to assess the tolerability of a three-drug combination utilizing irinotecan (Ir), cetuximab (Cx) and two schedules of MK-0646 (Mk). Methods: Eligible patients (pts) had previously failed both Ir and oxaliplatin and had progressed on or within 3 months of their last therapy. Pts were required to have measurable disease and tissue samples available for tumour KRAS testing. Pts were randomised to receive either Mk 10mg/kg weekly (Arm A) or Mk 15mg/kg loading followed by 7.5mg/kg every alternate week (Arm B). All randomised pts also received Cx 400mg/m2 loading followed by 250mg/m2 weekly and Ir according to the same dose and schedule as they had previously received. Patients continued on treatment until disease progression with radiological response assessments undertaken every 6 weeks. Results: 10 pts were recruited to Arm A and 8 to Arm B. Pt characteristics: median age 60.5 years, male 67%, PS 0/1 33%/67%. Median number of prior chemotherapy regimens 3. The median number of cycles of Mk received in Arm A and B is 25 and 8 respectively. Reported grade III/IV toxicities in Arm A and Arm B were: neutropenia 30% and 0%, diarrhoea 30% and 25%, hypomagnesemia 0% and 25%. Hyperglycemia (≥ grade 2) was seen in 10% of Arm A and 25% in Arm B. Acneiform skin toxicity (≥ grade 2) was seen in 30% of Arm A and 62% of Arm B. The radiological response rate was 33% in Arm A and 14% in Arm B. The median time on study drug is 5.8 months in Arm A and 3.9 months in Arm B. 2 pts on Arm A and 1 in Arm B remain on study therapy. Tumour KRAS testing is in progress. Conclusions: The combination of MK-0646, cetuximab and irinotecan is tolerable with no concerning overlapping toxicities highlighted. PFS and KRAS data will be available for presentation. The efficacy of this three drug combination is under evaluation in an ongoing randomised phase II/III study.

[Table: see text]

A prospective study of oxaliplatin and capecitabine (CapOx) in metastatic colorectal cancer (MCRC) with baseline stratification according to resectability status

4024

Background: Consideration of metastasectomy is now standard practice in the management of selected patients (pts) with stage IV MCRC. As a result, modification to the current staging system has been suggested to more clearly define subgroups of stage IV pts. As yet, there are no prospective data comparing the outcomes of pts according to resectability status. This phase II study evaluates the outcomes of pts according to baseline resectability status, and examines the utility of CapOx chemotherapy as a neoadjuvant treatment strategy. Methods: Eligible pts had received no prior chemotherapy for MCRC. At study entry imaging review was undertaken and pts stratified into 3 groups according to resectability status; non-resectable (group 1), potentially resectable liver disease (group 2), resectable liver disease (group 3). All pts received identical chemotherapy; capecitabine 2,000mg/m2 d1–14 and oxaliplatin 130mg/m2 d 1 repeated every 3 weeks. Repeat imaging was undertaken every 4 cycles. For pts in groups 2 & 3, all imaging was reviewed by a specialist hepatic MDT, where feasible metastasectomy was undertaken following 4 or 8 cycles of chemotherapy. Planned enrolment was 130 pts, with study endpoints including; response rate, PFS & OS. Results: 129 pts are enrolled. Median age 62 (range 29–78). Median number of cycles delivered 8 (range 1–12). Grade III/IV toxicities; diarrhoea 14%, neutropenia 7.8%, peripheral neuropathy 2%. 60 day all cause mortality 3.1%. There have been no post operative deaths following liver resection. Median follow up is 19.3 months. Outcome data for each group is summarised below. Conclusion: CapOx chemotherapy is safe and well tolerated when used as a neoadjuvant treatment strategy. This prospective study clearly demonstrates the wide variation in outcomes according to baseline resectability status, and highlights the need for modification to the staging system to account for these patient subgroups in future studies.

[Table: see text]

[Table: see text]

A novel, rapid, computerized method for quantitation of neuronal damage in a rat model of stroke

Determination of extent of infarction in animal models of cerebral ischemia is most commonly achieved by either classical histology (thionin staining) and light microscopy or staining with 2,3, 5-triphenyltetrazolium chloride (TTC). These techniques have limitations and we now describe a novel technique and its validation for assessment of the neuroprotective activity of AM-36, a novel arylalkypiperazine compound with combined antioxidant and sodium channel blocking activity. AM-36 (1.8 mg/kg i.p.) or vehicle, was administered 30 min, 24 and 48 h after endothelin-1-induced middle cerebral artery occlusion in conscious rats. Rats were killed at 72 h, brains removed and frozen in liquid nitrogen prior to coronal sectioning. Using a simple apparatus relying on basic principles of light propagation and a computerised image analysis system, ischemic damage in unstained slide-mounted sections was clearly visualised and measured. AM-36 significantly reduced the area of infarct in both cortex and striatum. The method was verified by thionin staining, and light microscopy. Linear regression analysis showed a highly significant correlation between methods at 72 h for infarct area in the cortex and striatum. Highly significant correlations between methods were found at 3 and 24 h after ischemia. Our method quickly and clearly delineates areas of damage in a manner superior to conventional staining methods.

Delayed treatment with AM-36, a novel neuroprotective agent, reduces neuronal damage after endothelin-1-induced middle cerebral artery occlusion in conscious rats

BACKGROUND AND PURPOSE

AM-36 is a novel arylalkylpiperazine with combined antioxidant and Na(+) channel blocking actions. Individually, these properties have been shown to confer neuroprotection in a variety of in vitro and in vivo animal models of stroke. Preliminary studies have shown that AM-36 is neuroprotective in vivo. The purpose of the present study was to assess the neuroprotective and behavioral outcome after delayed administration of AM-36 in an endothelin-1-induced, middle cerebral artery model of cerebral ischemia in conscious rats.

METHODS

Conscious male hooded Wistar rats were subjected to middle cerebral artery occlusion by perivascular microinjection of endothelin-1 via a previously implanted cannula. AM-36 (6 mg/kg IP) or vehicle was administered intraperitoneally 30, 60, or 180 minutes after middle cerebral artery occlusion. Functional outcome was determined 24, 48, and 72 hours after stroke by neurological deficit score, motor performance, and sensory hemineglect tests. Rats were killed at 72 hours, and infarct area and volume were determined by histology and computerized image analysis.

RESULTS

Endothelin-1-induced middle cerebral artery occlusion resulted in marked functional deficits and neuronal damage. AM-36 significantly reduced cortical damage when administration was delayed until 30, 60, or 180 minutes after stroke. Interestingly, neuronal damage was time-dependently reduced, with the greatest protection found when AM-36 was administered 180 minutes after stroke. Striatal damage was significantly reduced after treatment with AM-36 at 180 minutes after stroke. Functional outcome paralleled histopathology. Rota-rod performance, sensory hemineglect, and neurological deficit scores returned to preischemia levels in AM-36-treated rats by 72 hours after stroke when administration was delayed by 180 minutes after stroke.

CONCLUSIONS

AM-36 potently protects against both neuronal damage and functional deficits even when administered up to 180 minutes after induction of stroke. In fact, the greatest protection was found when administration was delayed by 180 minutes after stroke. The possible mechanisms of action of AM-36 are discussed. The present findings suggest that AM-36 may have great promise in the acute treatment of human stroke.

Loss of [125I]-pindolol binding to beta-adrenoceptors on rat nodose ganglion after chronic isoprenaline treatment

The nodose ganglion contains the cell bodies of afferent nerves which convey predominantly sensory information from the viscera to the central nervous system (CNS). Autoradiographic studies show binding sites for beta-adrenoceptor ligands are present on sections of the rat nodose ganglion and also on the corresponding inferior vagal ganglion in humans, indicating the presence of beta-adrenoceptors in these ganglia. Since prolonged stimulation of beta-adrenoceptors in rats with the nonselective beta-adrenoceptor agonist isoprenaline (400 micrograms kg-1 day-1 s.c.) for 14 days results in desensitisation and/or down-regulation of receptors in peripheral tissues, such as heart, kidney and blood vessels, the effects of this treatment on the beta-adrenoceptor population on the nodose ganglion have been examined. Using [125I]-pindolol as a radioligand, autoradiographic studies revealed that specific binding was reduced by 74% in ganglia from isoprenaline-pretreated rats compared to that in ganglia from vehicle-pretreated rats, demonstrating down-regulation of receptors by isoprenaline. [125I]-Pindolol binding was sensitive to inhibition by ICI 118.551 (selective beta 2-adrenoceptor antagonist) but not to atenolol (selective beta 1-adrenoceptor antagonist), indicating receptors are predominantly of the beta 2-adrenoceptor subtype. No change in binding was apparent over the vagus nerve. The nodose ganglion appears to be an additional site at which beta 2-adrenoceptors may be down-regulated in vivo, possibly interfering with normal baro-, chemo- and sensory reflexes.

Autoradiographic localization of calcitonin gene-related peptide receptors in guinea pig respiratory tract: effect of capsaicin pretreatment

Calcitonin gene-related peptide (CGRP) is a potent vasodilator peptide present in capsaicin-sensitive neurons innervating the respiratory tract. In this study, the autoradiographic distribution of [125I]CGRP binding sites was investigated in guinea pig airways. Extremely dense specific binding occurred over parenchymal tissue, with moderate specific binding over tracheal glands, the endothelium of pulmonary veins and arteries, and small blood vessels in the bronchial wall. The localization of binding sites for [125I]CGRP over blood vessels but not bronchial smooth muscle correlates well with the physiological actions of this peptide, although the function of the parenchymal sites is unknown. No significant difference in binding was seen in vehicle- or capsaicin-pretreated animals, suggesting that sites are not reliant on factors from capsaicin-sensitive neurons.

Autoradiographic localization of substance P binding sites in rat footpad skin

The autoradiographic distribution of binding sites for 60 pM [125I]Bolton-Hunter substance P (BHSP) was investigated in slide-mounted sections of rat footpad skin. BHSP binding sites were found over dermal papillae, postcapillary venules, sweat glands and arterioles. No binding was seen over mast cells, sebaceous glands or pacinian corpuscles. Specific BHSP binding was inhibited by substance P greater than neurokinin A greater than neurokinin B, indicating binding to an NK1 (substance P-preferring) site. The NK1 binding sites over postcapillary venules and arterioles probably represent receptors mediating plasma extravasation and vasodilatation, respectively. There was no apparent change in distribution or number of BHSP binding sites after neonatal capsaicin pretreatment, indicating a probable absence of NK1 receptors on sensory terminals. No binding sites were observed for 100 pM [125I]iodohistidyl neurokinin A (INKA).

Cellular factors influencing GABA response in hippocampal pyramidal cells

1. The action of gamma-aminobutyric acid (GABA) on the hippocampal pyramidal cells was studied by intracellular recordings using an in vitro slice preparation. 2. Orthodromic tetanic stimulation induced dramatic modifications of the GABA response. Initial hyperpolarizing GABA responses were observed to invert to depolarizations following the tetanic shock. 3. The hyperpolarizing and depolarizing GABA responses exhibited differential sensitivity to GABA and bicuculline. Application of low concentrations of GABA predominantly activated the hyperpolarizing response. Activation of depolarizing response in both the dendrites and somata required a larger quantity of GABA. Bicuculline antagonized both the hyperpolarizing and depolarizing responses; however, the agent appeared to exert a stronger influence on the depolarizing response. At the concentration of 10(-5) M, bicuculline completely blocked the depolarizing response while the hyperpolarizing response was only suppressed by 50%. 4. During prolonged periods of GABA application (10 s or more), the GABA-induced conductance increase was not maintained, suggesting that the GABA response underwent desensitization. The results also suggest that the desensitization process affected both the hyperpolarizing and depolarizing responses. 5. The depolarizing response elicited by GABA was facilitated by increasing the extracellular potassium concentration. 6. It is possible that the modification of the GABA response following tetanic stimulation is in part caused by the desensitization of the GABA response and an accumulation of extracellular K+ and GABA.

Simultaneous versus successive discrimination of weights: a neuroanatomical interpretation

Using the Method of Constant Stimuli, difference limens were obtained for lifted weights of 50 to 200 gm. 184 college students were assigned to one of four experimental conditions resulting from the combination of two modes of stimulus presentation with whether the preferred or non-preferred hand was used to judge the standard weight. Simultaneous interhand judgments produced significantly larger Weber Ratios and more variable Constant Errors than were produced by Successive intrahand presentation. This was contrary to earlier work in the visual modality indicating that simultaneous stimulus presentation produced more sensitive discrimination than did successive. The results are interpreted in terms of the neural organization of tactile input.