Analgesic Effects of Topical Amitriptyline in Patients With Chemotherapy-Induced Peripheral Neuropathy: Mechanistic Insights From Studies in Mice.

Oral amitriptyline hydrochloride (amitriptyline) is ineffective against some forms of chronic pain and is often associated with dose-limiting adverse events. We evaluated the potential effectiveness of high-dose topical amitriptyline in a preliminary case series of chemotherapy-induced peripheral neuropathy patients and investigated whether local or systemic adverse events associated with the use of amitriptyline were present in these patients. We also investigated the mechanism of action of topically administered amitriptyline in mice. Our case series suggested that topical 10% amitriptyline treatment was associated with pain relief in chemotherapy-induced peripheral neuropathy patients, without the side effects associated with systemic absorption. Topical amitriptyline significantly increased mechanical withdrawal thresholds when applied to the hind paw of mice, and inhibited the firing responses of C-, Aß- and Aδ-type peripheral nerve fibers in ex vivo skin-saphenous nerve preparations. Whole-cell patch-clamp recordings on cultured sensory neurons revealed that amitriptyline was a potent inhibitor of the main voltage-gated sodium channels (Nav1.7, Nav1.8, and Nav1.9) found in nociceptors. Calcium imaging showed that amitriptyline activated the transient receptor potential cation channel, TRPA1. Our case series indicated that high-dose 10% topical amitriptyline could alleviate neuropathic pain without adverse local or systemic effects. This analgesic action appeared to be mediated through local inhibition of voltage-gated sodium channels. PERSPECTIVE: Our preliminary case series suggested that topical amitriptyline could provide effective pain relief for chemotherapy-induced peripheral neuropathy patients without any systemic or local adverse events. Investigation of the mechanism of this analgesic action in mice revealed that this activity was mediated through local inhibition of nociceptor Nav channels.

Initial cooling time before freezing affects post-thaw quality and reproductive performance of rabbit semen.

The aim of this study was to investigate the effect of initial cooling time at 5°C during semen cryopreservation on post-thaw quality and reproductive performance of rabbit semen. Pooled semen samples (n = 6) were divided into two subsamples and cooled at 5°C for 45 or 90 min. After cooling, the semen samples were diluted to a ratio of 1:1 (v:v) with a freezing extender composed of Tris-citrate-glucose (TCG) containing 16% of dimethylsulfoxide and 0.1 mol/L sucrose. The semen was subsequently loaded in 0.25 ml straws, equilibrated at 5°C and frozen in liquid nitrogen vapor. After thawing, sperm motility, viability, osmotic resistance, acrosome and DNA integrity were assessed. Our results indicate that the longer cooling time, that is, 90 min before cryopreservation significantly improves sperm post-thaw viability, motility and fertility. In fact, reproductive performances obtained with semen frozen after a 90 min cooling time were similar to those produced by fresh semen insemination. Hence, the present research provides an effective freezing protocol for rabbit semen that will allow for the creation of a sperm cryobank for the conservation of Italian rabbit genetic resources, as well as the use of frozen semen doses in commercial farms.

Population pharmacokinetic/pharmacodynamic modeling of drug-induced adverse effects of a novel homocamptothecin analog, elomotecan (BN80927), in a Phase I dose finding study in patients with advanced solid tumors.

PURPOSE: To characterize the pharmacokinetic profile of elomotecan, a novel homocamptothecin analog, evaluate the dose-limiting toxicities, and establish the relationship between exposure and toxicity in the first Phase I study in patients with advanced malignant solid tumors. Preliminary antitumor efficacy results are also provided. DESIGN: Elomotecan was administered as a 30-min intravenous infusion at doses ranging from 1.5 to 75 mg once every 3 weeks to 56 patients with advanced solid tumors. Plasma concentration data and adverse effects were modeled using the population approach. RESULTS: Elomotecan showed linear pharmacokinetics, and clearance was decreased with age. The model predicts a 47 and 61 % reduction in CL for patients aged 60 and 80 years, respectively, when compared with younger patients (30 years). Neutropenia represented the dose-limiting toxicity. The maximum tolerated dose and the recommended dose (RD) were 75 and 60 mg, respectively. Elomotecan elicited a 20, 5, 2, and 2 % severe (grade 4) neutropenia, asthenia, nausea, and vomiting at the RD, respectively. Of the subjects in the RD cohort, 41.7 % had a stable disease mean duration of 123.6 ± 43.4 days. CONCLUSIONS: The pharmacokinetic parameters and the toxicity pattern of elomotecan suggest that this novel homocamptothecin analog should be further explored in the clinical setting using a dose of 60 mg administered as a 30-min intravenous infusion, once every 3 weeks.

Chiral capillary electrophoretic determination of the enantiomeric purity of homocamptothecin derivatives, promising antitumor topoisomerase I inhibitors, using highly sulfated CDs and fluorescence detection.

EKC methods for the enantiomeric resolution of homocamptothecin derivatives, potent anticancer agents targeting DNA topoisomerase I selected for clinical trials, were developed using highly sulfated beta-CD as chiral selectors at acidic pH. Optimal electrophoretic conditions, with migration times under 15 min, were as follows: for the neutral homocamptothecin analog 1, a BGE of 75 mM phosphate buffer pH 2.5 (H(3)PO(4) + triethanolamine)/ACN - 95/5 v/v, with 7.5% w/v highly S-beta-CD, an applied field of 0.2 kV/cm and a fused capillary temperature control of 30 +/- 0.1 degrees C (typical current approximately 175 microA); for the cationic homocamptothecin 2, a BGE of 25 mM phosphate buffer pH 2.5 (H(3)PO(4) + TEA)/ACN - 90/10 v/v, with 2.5% w/v highly S-beta-CD, an applied field of 0.15 kV/cm and a fused capillary temperature control of 25 +/- 0.1 degrees C (typical current approximately 45 muA), and both are validated. The best results in terms of LOQ were obtained by EC with fluorescence detection: 10 ng/mL and 20 ng/mL for 1 and 2, respectively (LOQ divided by 150 for 1 and 5 for 2 with respect to UV), thus making this method particularly convenient for enantiomeric purity determination of galenic forms. UV detection appears to be an alternative to fluorescence for the analysis of the main component either for the control of galenic forms or for therapeutic adaptation. Moreover, this method exhibits better performances than HPLC.

Phase I dose-finding study and a pharmacokinetic/pharmacodynamic analysis of the neutropenic response of intravenous diflomotecan in patients with advanced malignant tumours.

PURPOSE: To determine the maximum tolerated dose (MTD) of intravenous (iv) diflomotecan administered once every 3 weeks, and to characterize the relationship between pharmacokinetics and neutropenic effect, using a semi-mechanistic pharmacokinetic/pharmacodynamic (PK/PD) model. EXPERIMENTAL DESIGN: Twenty-four patients received a total of 75 cycles of iv diflomotecan that was administered as 20-min infusion, once every 3 weeks at escalating doses of 2, 4, 5, and 6 mg/m2. Haematological and non-haematological toxicities were evaluated. Plasma concentrations of diflomotecan were measured after the first drug administration. RESULTS: Dose limiting toxicity (DLT) following the first cycle occurred in 12 patients and a total of 16 patients experienced DLT at some point in the trial. During the first cycle of treatment the number of patients in the 5 and 6 mg/m2 dose groups that experienced DLT was 3 of 4, and 3 of 3, respectively. Therefore, the dose of 5 mg/m2 was considered the MTD and the dose of 4 mg/m2 the recommended dose (RD). During the first cycle, 12 patients experienced DLT, six had either infection of haematological toxicity and eight complained of fatigue. The best response was a partial response in one patient treated at the 6 mg/m2 dose level. Disease stabilization was observed in seven patients (four patients treated at 4 mg/m2 and one patient at each dose level of 2, 5, and 6 mg/m2). The remaining patients had all progressive disease. The median time to progression for all patients was 5.9 weeks. Pharmacokinetics of diflomotecan was described with a three-compartmental model. Mean population parameter estimates of the apparent volume of distribution of the central compartment (V c) increased linearly with body surface area (BSA) as: V c (L) = 41.5 x (BSA/1.85), and the mean population estimate of the apparent volume of distribution of the shallow compartment was lower in females (29.5 vs 48.8 L). Computer simulations showed the lack of clinical significance of these covariates. The time course of the neutropenic response was adequately described by a semi-mechanistic model that includes cellular processes and drug effects. CONCLUSIONS: The MTD and RD after a 20-min iv infusion of diflomotecan every 3 weeks are 4 and 5 mg/m2, respectively. Diflomotecan showed linear pharmacokinetic behaviour and the selected PK/PD model described adequately the time course of neutropenia. The mean model predicted values of nadir and time to nadir after a 20-min iv infusion of 4 mg/m2 of diflomotecan was 0.86 x 10(9) /L neutrophil cell counts and 11 days, respectively.

Diflomotecan pharmacokinetics in relation to ABCG2 421C>A genotype.

OBJECTIVE: The adenosine triphosphate-binding cassette transporter ABCG2 (breast cancer resistance protein [BCRP]) functions as an efflux transporter for many drugs, including the topoisomerase I inhibitor diflomotecan, and is expressed at high levels in the intestine and liver. We performed an exploratory analysis to evaluate the effects of the natural allelic variant ABCG2 421C>A on the pharmacokinetics of diflomotecan. METHODS: The drug was administered to 22 adult white patients with cancer as a 20-minute infusion (dose, 0.10-0.27 mg), followed 2 weeks later by an oral solution (dose, 0.10-0.35 mg). RESULTS: The ABCG2 421C>A genotype significantly affected the pharmacokinetics of diflomotecan; in 5 patients heterozygous for this allele, plasma levels after intravenous drug administration were 299% (P =.015) of those in 15 patients with wild-type alleles, at mean values of 138 ng x h/mL x mg(-1) (95% confidence interval, 11.3-264 ng x h/mL x mg(-1)) versus 46.1 ng x h/mL x mg(-1) (95% confidence interval, 25.6-66.7 ng x h/mL x mg(-1)), respectively. Diflomotecan levels were not significantly influenced by 11 known variants in the ABCB1, ABCC2, cytochrome P450 (CYP) 3A4, and CYP3A5 genes. CONCLUSION: These findings provide the first evidence linking variant ABCG2 alleles to altered drug exposure and suggest that interindividual variability in substrate drug effects might be influenced, in part, by ABCG2 genotype.

Phase I pharmacological and bioavailability study of oral diflomotecan (BN80915), a novel E-ring-modified camptothecin analogue in adults with solid tumors.

PURPOSE: Diflomotecan (BN80915) is an E-ring modified camptothecin analogue that possesses greater lactone stability in plasma compared with other topoisomerase I inhibitors, a potential advantage for antitumor activity. As with other camptothecins, oral administration has pharmacological and clinical advantages. This Phase I study was performed to assess the feasibility of the administration of oral diflomotecan, to determine the maximum-tolerated, dose its bioavailability, and to explore the pharmacokinetics. EXPERIMENTAL DESIGN: An initial i.v. bolus was administered to assess the bioavailability of diflomotecan. Fourteen days later, diflomotecan was administered p.o. once daily for 5 days to adult patients with solid malignant tumors and repeated every 3 weeks. BN80915 and its open lactone form BN80942 were measured. RESULTS: Twenty-two patients entered the study and received a total of 57 cycles of oral diflomotecan at flat dose levels of 0.10, 0.20, 0.27, and 0.35 mg. The main toxicity was hematological, but some patients experienced alopecia, mild gastrointestinal toxicity, and fatigue. At the 0.35-mg dose level, 2 of 4 patients experienced dose-limiting toxicity comprising grade 3 thrombocytopenia with epistaxis and febrile neutropenia in 1 patient and uncomplicated grade 4 neutropenia lasting for >7 days in another. Toxicity was acceptable at the 0.27-mg dose level at which dose-limiting toxicities were observed in 3 of 12 patients (grade 4 neutropenia > 7 days, complicated by fever in 1 patient but without other signs of infection). After two cycles of diflomotecan, 6 patients had disease stabilization, which was maintained in 2 patients for 9 months and >1 year, respectively. Diflomotecan pharmacokinetics were linear over the dose range studied. Systemic exposure correlated with the fall in WBC counts. The mean oral bioavailability (+/-SD) was 72.24 +/- 59.2% across all dose levels. Urinary excretion of BN80915 was very low. CONCLUSIONS: The recommended oral diflomotecan dose for Phase II studies is 0.27 mg/day x 5 every 3 weeks. This regimen is convenient and generally well tolerated with a favorable pharmacokinetic profile and high but variable bioavailability.