Adenoviral vector-mediated expression of a gene encoding secreted, EpCAM-targeted carboxylesterase-2 sensitises colon cancer spheroids to CPT-11

CPT-11 (irinotecan or 7-ethyl-10[4-(1-piperidino)-1-piperidino] carbonyloxycamptothecin) is an anticancer agent in use for the treatment of colon cancer. In order to be fully active, CPT-11 needs to be converted into SN-38 (7-ethyl-10-hydroxycamptothecin) by the enzyme carboxylesterase (CE). In humans, only a minority of CPT-11 is converted to SN-38. To increase the antitumour effect of CPT-11 by gene-directed enzyme prodrug therapy, we constructed a replication-deficient adenoviral vector Ad.C28-sCE2 containing a fusion gene encoding a secreted form of human liver CE2 targeted to the surface antigen epithelial cell adhesion molecule (EpCAM) that is highly expressed on most colon carcinoma cells. By targeting CE2 to EpCAM, the enzyme should accumulate specifically in tumours and leakage into the circulation should be minimised. Ad.C28-sCE2-transduced colon carcinoma cells expressed and secreted active CE that bound specifically to EpCAM-expressing cells. In sections of three-dimensional colon carcinoma spheroids transduced with Ad.C28-sCE2, it was shown that C28-sCE2 was capable of binding untransduced cells. Most importantly, treatment of these spheroids with nontoxic concentrations of CPT-11 resulted in growth inhibition comparable to treatment with SN-38. Therefore, Ad.C28-sCE2 holds promise in gene therapy approaches for the treatment of colon carcinoma

Phase I safety, pharmacokinetic, and pharmacodynamic study of the thrombospondin-1-mimetic angiogenesis inhibitor ABT-510 in patients with advanced cancer

Purpose ABT-510 is an angiogenesis inhibitor derived from thrombospondin-1, a naturally occurring inhibitor of angiogenesis. We investigated ABT-510, which was administered subcutaneously in patients with advanced solid malignancies, to assess safety, pharmacokinetics, and serum markers of angiogenesis. Patients and Methods ABT-510 was administered subcutaneously as a continuous infusion (100 mg/24 h) and bolus injections (100, 200, and 260 mg once daily; 50 and 100 mg twice daily) in 28-day cycles. Results Thirty-nine patients received a total of 144 treatment cycles. Administration by continuous infusion was hampered by the onset of painful skin infiltrates at the injection site. In the bolus injection regimens, the most common toxicities observed were mild injection-site reactions and fatigue. Maximum-tolerated dose was not defined, but 260 mg was defined as the maximum clinically practical dose. ABT-510 pharmacokinetics were linear across the dosage ranges tested, and the potential therapeutic threshold (plasma concentrations >100 ng/mL >3 h/d) was achieved with all dose regimens. Median serum basic fibroblast growth factor (bFGF) levels decreased from 14.1 pg/mL (range, 0.5 to 77.7 pg/mL) at baseline to 3.2 pg/mL (range, 0.2 to 29.4 pg/mL) after 56 days of treatment (P = .003). No correlations with time on study or ABT-510 dose or exposure were observed for individual changes in bFGF. Stable disease lasting for six cycles or more was seen in six patients. Conclusion ABT-510 demonstrated a favorable toxicity profile and linear and time-independent pharmacokinetics with biologically relevant plasma concentrations. The significant number of patients with prolonged stable disease and the convenient method of dosing merit further studies with this angiogenesis inhibitor

Phase I study of the thrombospondin-1-mimetic angiogenesis inhibitor ABT-510 with 5-fluorouracil and leucovorin: A safe combination

We performed a phase I study with the thrombospondin-l-mimetic angiogenesis inhibitor ABT-510 combined with 5-fluorouracil and leucovorin (5-FU/LV) to determine safety profile and assess pharmacokinetic interactions. Patients with advanced solid malignancies received LV 20 mg/m(2) followed by 5-FU 425 mg/m(2) both administered intravenously in 15 min daily for 5 days every 4 weeks. ABT-510 was administered subcutaneously twice daily continuously from day 2 onwards. Blood and urine samples for pharmacokinetic analyses were collected at days 1, 5 and 22. Twelve patients received a total of 45 cycles of 5-FU/ LV combined with ABT-510. ABT-510 dose levels studied were 50 and 100 mg. The combination was well tolerated, with a toxicity profile comparable to that of 5-FU/LV alone. At the dose levels studied no significant pharmacokinetic interactions were observed. These data indicate that ABT-510 administered twice daily subcutaneously can be safely combined with 5-FU/LV administered daily for 5 days, every 4 weeks. (c) 2005 Elsevier Ltd. All rights reserved

Chloroform extract of hog barn dust modulates skeletal muscle ryanodine receptor calcium-release channel (RyR1)

Skeletal muscle weakness is a reported ailment in individuals working in commercial hog confinement facilities. To date, specific mechanisms responsible for this symptom remain undefined. The purpose of this study was to assess whether hog barn dust (HBD) contains components that are capable of binding to and modulating the activity of type 1 ryanodine receptor Ca2+-release channel (RyR1), a key regulator of skeletal muscle function. HBD collected from confinement facilities in Nebraska were extracted with chloroform, filtered, and rotary evaporated to dryness. Residues were resuspended in hexane-chloroform (20:1) and precipitates, referred to as HBDorg, were air-dried and studied further. In competition assays, HBDorg dose-dependently displaced [3H]ryanodine from binding sites on RyR1 with an IC50 of 1.5 ± 0.1 μg/ml (Ki = 0.4 ± 0.0 μg/ml). In single-channel assays using RyR1 reconstituted into a lipid bilayer, HBDorg exhibited three distinct dose-dependent effects: first it increased the open probability of RyR1 by increasing its gating frequency and dwell time in the open state, then it induced a state of reduced conductance (55% of maximum) that was more likely to occur and persist at positive holding potentials, and finally it irreversibly closed RyR1. In differentiated C2C12 myotubes, addition of HBD triggered a rise in intracellular Ca2+ that was blocked by pretreatment with ryanodine. Since persistent activation and/or closure of RyR1 results in skeletal muscle weakness, these new data suggest that HBD is responsible, at least in part, for the muscle ailment reported by hog confinement workers