A Phase 1 Study of Intravenous Plazomicin in Healthy Adults to Assess Potential Effects on the QT/QTc Interval, Safety, and Pharmacokinetics

Plazomicin is an aminoglycoside with in vitro activity against multidrug-resistant Enterobacteriaceae. A phase 1, randomized, double-blind, crossover study assessed the potential effects of plazomicin on cardiac repolarization (NCT01514929). Fifty-six healthy adults (24 men, 32 women) received a single therapeutic dose of plazomicin (15 mg/kg administered by 30-minute intravenous infusion), a single supratherapeutic dose of plazomicin (20 mg/kg administered by 30-minute intravenous infusion), placebo, or oral moxifloxacin (400 mg). The primary end point was the baseline-adjusted, placebo-corrected QTc interval using the Fridericia formula (ΔΔQTcF). Assay sensitivity was concluded if the lower limit of a 1-sided 95%CI (adjusted for multiplicity using the Hochberg procedure) for moxifloxacin ΔΔQTcF was >5 milliseconds at ≥1 prespecified time points. No QT prolongation effect for plazomicin was concluded if the largest mean effect was <5 milliseconds, and the upper limit of a 2-sided 90%CI for plazomicin ΔΔQTcF was <10 milliseconds at all time points. Assay sensitivity was demonstrated based on moxifloxacin ΔΔQTcF. No QT prolongation effect for plazomicin was concluded because the largest mean ΔΔQTcF for plazomicin was 3.5 milliseconds, and the highest upper limit was 5.6 milliseconds. No clinically relevant changes were observed in electrocardiograms. For the 15- and 20-mg/kg dose levels of plazomicin, mean peak plasma concentration values were 76.0 and 96.6 mg/L, and mean values of the area under the concentration-time curve over 24 hours were 263 and 327 mg·h/L, respectively. Model-derived pharmacokinetic parameters and safety findings were generally consistent with previously reported plazomicin studies. In conclusion, therapeutic and supratherapeutic doses of plazomicin had no clinically significant effect on cardiac repolarization and were generally well tolerated.

Population Pharmacokinetics and Exposure-Response Analyses for CPX-351 in Patients With Hematologic Malignancies

CPX-351, a dual-drug liposomal encapsulation of cytarabine and daunorubicin at a synergistic ratio, is approved in the United States for adults with newly diagnosed therapy-related acute myeloid leukemia or acute myeloid leukemia with myelodysplasia-related changes. Population pharmacokinetics analyses were performed using nonlinear mixed-effect modeling on pooled data from 3 clinical studies, and the impact of CPX-351 exposures on efficacy and safety was assessed. The pharmacokinetics of cytarabine and daunorubicin were described using 2-compartment models with linear elimination. None of the evaluated covariates had a clinically significant impact on plasma exposure to total cytarabine or daunorubicin, while bilirubin and formulation showed statistically significant effects on pharmacokinetic parameters of cytarabine and daunorubicin, respectively. In patients with mild/moderate renal impairment or serum bilirubin ≤3 mg/dL, plasma exposures to cytarabine and daunorubicin following CPX-351 were within the variability range for patients with normal kidney function or serum bilirubin levels. Exposure-response analysis demonstrated that better efficacy outcomes were associated with higher CPX-351 exposure quartiles. Early mortality rates in all CPX-351 exposure quartiles were lower vs the 7 + 3 control group, and lower mortality rates were associated with higher exposure quartiles. A trend toward greater frequency of grade 3 treatment-emergent adverse events (but not grade 4/5 events) was observed at higher CPX-351 exposure quartiles. Overall, the population pharmacokinetic analyses indicate no adjustments to the recommended dose and schedule of CPX-351 are warranted for patients with mild/moderate renal impairment or serum bilirubin ≤3 mg/dL. Results from the exposure-response analyses suggest the current CPX-351 regimen provides a favorable risk-benefit profile.

A Phase 1 Study To Assess the Pharmacokinetics of Intravenous Plazomicin in Adult Subjects with Varying Degrees of Renal Function

Plazomicin is an FDA-approved aminoglycoside for the treatment of complicated urinary tract infections. In this open-label study, 24 adults with normal renal function or mild, moderate, or severe renal impairment (n = 6 per group) received a single 7.5-mg/kg of body weight dose of plazomicin as a 30-min intravenous infusion. Total clearance declined with renal impairment, resulting in 1.98-fold and 4.42-fold higher plazomicin exposures, as measured by the area under the concentration-time curve from 0 h to infinity, in subjects with moderate and severe impairment, respectively, than in subjects with normal renal function. (This study has been registered at ClinicalTrials.gov under identifier NCT01462136.).

A Phase I/Ib Study of Enzalutamide Alone and in Combination with Endocrine Therapies in Women with Advanced Breast Cancer

Purpose: Several lines of evidence support targeting the androgen signaling pathway in breast cancer. Enzalutamide is a potent inhibitor of androgen receptor signaling. Preclinical data in estrogen-expressing breast cancer models demonstrated activity of enzalutamide monotherapy and enhanced activity when combined with various endocrine therapies (ET). Enzalutamide is a strong cytochrome P450 3A4 (CYP3A4) inducer, and ETs are commonly metabolized by CYP3A4. The pharmacokinetic (PK) interactions, safety, and tolerability of enzalutamide monotherapy and in combination with ETs were assessed in this phase I/Ib study.Experimental Design: Enzalutamide monotherapy was assessed in dose-escalation and dose-expansion cohorts of patients with advanced breast cancer. Additional cohorts examined effects of enzalutamide on anastrozole, exemestane, and fulvestrant PK in patients with estrogen receptor-positive/progesterone receptor-positive (ER⁺/PgR⁺) breast cancer.Results: Enzalutamide monotherapy (n = 29) or in combination with ETs (n = 70) was generally well tolerated. Enzalutamide PK in women was similar to prior data on PK in men with prostate cancer. Enzalutamide decreased plasma exposure to anastrozole by approximately 90% and exemestane by approximately 50%. Enzalutamide did not significantly affect fulvestrant PK. Exposure of exemestane 50 mg/day given with enzalutamide was similar to exemestane 25 mg/day alone.Conclusions: These results support a 160 mg/day enzalutamide dose in women with breast cancer. Enzalutamide can be given in combination with fulvestrant without dose modifications. Exemestane should be doubled from 25 mg/day to 50 mg/day when given in combination with enzalutamide; this combination is being investigated in a randomized phase II study in patients with ER⁺/PgR⁺ breast cancer. Clin Cancer Res; 23(15); 4046-54. ©2017 AACR.

Pharmacokinetic Drug Interaction Studies with Enzalutamide

Background and Objectives

Two phase I drug interaction studies were performed with oral enzalutamide, which is approved for the treatment of metastatic castration-resistant prostate cancer (mCRPC).

Methods

A parallel-treatment design (n = 41) was used to evaluate the effects of a strong cytochrome P450 (CYP) 2C8 inhibitor (oral gemfibrozil 600 mg twice daily) or strong CYP3A4 inhibitor (oral itraconazole 200 mg once daily) on the pharmacokinetics of enzalutamide and its active metabolite N-desmethyl enzalutamide after a single dose of enzalutamide (160 mg). A single-sequence crossover design (n = 14) was used to determine the effects of enzalutamide 160 mg/day on the pharmacokinetics of a single oral dose of sensitive substrates for CYP2C8 (pioglitazone 30 mg), CYP2C9 (warfarin 10 mg), CYP2C19 (omeprazole 20 mg), or CYP3A4 (midazolam 2 mg).

Results

Coadministration of gemfibrozil increased the composite area under the plasma concentration–time curve from time zero to infinity (AUC_∞) of enzalutamide plus active metabolite by 2.2-fold, and coadministration of itraconazole increased the composite AUC_∞ by 1.3-fold. Enzalutamide did not affect exposure to oral pioglitazone. Enzalutamide reduced the AUC_∞ of oral S-warfarin, omeprazole, and midazolam by 56, 70, and 86 %, respectively; therefore, enzalutamide is a moderate inducer of CYP2C9 and CYP2C19 and a strong inducer of CYP3A4.

Conclusions

If a patient requires coadministration of a strong CYP2C8 inhibitor with enzalutamide, then the enzalutamide dose should be reduced to 80 mg/day. It is recommended to avoid concomitant use of enzalutamide with narrow therapeutic index drugs metabolized by CYP2C9, CYP2C19, or CYP3A4, as enzalutamide may decrease their exposure.

Electronic supplementary material

The online version of this article (doi:10.1007/s40262-015-0283-1) contains supplementary material, which is available to authorized users.

Phase Ib Study of Enzalutamide in Combination with Docetaxel in Men with Metastatic Castration-Resistant Prostate Cancer

PURPOSE

Preclinical evidence suggests that both docetaxel and enzalutamide target androgen receptor translocation and signaling. This phase Ib study assessed the safety, tolerability, and pharmacokinetics of docetaxel when administered with enzalutamide as first-line systemic chemotherapy in men with metastatic castration-resistant prostate cancer (mCRPC).

EXPERIMENTAL METHODS

Docetaxel-naïve patients received 21-day cycles of docetaxel (75 mg/m(2)). Enzalutamide (160 mg/day) was administered daily starting on day 2 of cycle 1. Patients were allowed to stop and restart docetaxel at any time following cycle 2. Treatment continued indefinitely until unacceptable toxicity or discontinuation due to investigator or patient preference.

RESULTS

A total of 22 patients received docetaxel, of whom 21 also received enzalutamide. Docetaxel was administered for a median of 5.0 cycles and enzalutamide for a median of 12.0 months. With concomitant treatment, geometric mean docetaxel exposure decreased by 11.8%, whereas peak concentrations decreased by 3.7% relative to docetaxel alone. The most common toxicities observed during the period of concomitant therapy were neutropenia (86.4%) and fatigue (77.3%). Common toxicities observed with post-docetaxel enzalutamide were constipation (23.8%), decreased appetite (19.0%), fatigue (19.0%), and musculoskeletal pain (19.0%). Treatment with enzalutamide and docetaxel resulted in prostate-specific antigen decreases in almost all patients based on exploratory analysis of available baseline and on-study prostate-specific antigen data.

CONCLUSIONS

The combination of docetaxel and enzalutamide is feasible, although higher rates of neutropenia and neutropenic fever than anticipated were observed. Reductions in docetaxel exposure with enzalutamide coadministration were not considered clinically meaningful. This combination warrants further study in a larger mCRPC population. Clin Cancer Res; 22(15); 3774-81. ©2016 AACR.

Enhanced cell-associated plasminogen activator pathway but not coagulation pathway activity contributes to motility in metastatic breast cancer cells

BACKGROUND

Activation of tumor cell-associated coagulation and plasminogen activator pathways occurs in malignant disease processes, including breast cancer, and may promote metastatic activity.

OBJECTIVES/METHODS

To compare the coagulation and plasminogen activator pathways of normal and metastatic cells, we examined two cell lines from the MCF-10 family of breast cells: near-normal immortalized MCF-10A cells, and metastatic MCF-10CA1 cells.

RESULTS

MCF-10CA1 cell motility was significantly increased as compared with that of MCF-10A cells. The two cell types supported similar rates of factor Xa generation, plasma thrombin generation, and fibrin formation. MCF-10A cells produced a stable fibrin network, whereas MCF-10CA1 cells lysed the surrounding fibrin network within 24 h of network formation. Importantly, fibrin located proximal to (within 10 microm) the MCF-10CA1 cell surface lysed substantially faster than fibrin located 100 microm from the surface. MCF-10CA1 cells supported significantly increased plasmin generation rates as compared with MCF-10A cells, providing a mechanism for the increased fibrinolytic activity of these cells towards the fibrin network. Metastatic MCF-10CA1 cells had increased expression (mRNA and protein) levels of urokinase plasminogen activator (u-PA) and decreased levels of plasminogen activator inhibitor-1 as compared with MCF-10A cells. Blocking u-PA activity with the active site-directed protease inhibitor amiloride substantially decreased MCF-10CA1 cell motility. Phosphorylated Akt levels were elevated in MCF-10CA1 cells, which partially explains the increased u-PA expression.

CONCLUSIONS

These results suggest that the tumor-associated plasminogen activator pathway, not the coagulation pathway, is a key distinguishing feature between metastatic MCF10-CA1 cells and normal MCF-10A cells.

Cross-species comparisons of the pharmacokinetics of ibudilast

To enable clinical development of ibudilast for new indications, its pharmacokinetics were characterized in mice, rats, rabbits, dogs, cynomolgus monkeys, and minipigs. Animal pharmacokinetics were compared with a separate study in healthy volunteers. Following oral dosing, the dose-normalized area under the curve (AUC) (DN-AUC(24h)) in humans is 896 ((ng*h ml(-1))/(mg kg(-1))), and in animals ranges from 0.3 to 87. The variability among species cannot be explained by intrinsic clearance, which in intravenous dosing experiments shows only moderate interspecies variation (13-41 l h(-1) m(-2)). A portal vein rat pharmacokinetics model suggested that differences in first-pass gut clearance may explain some of the interspecies variation in oral bioavailability. Ibudilast shows auto-induction of metabolism in some animals, but not in humans. Plasma protein binding in humans and some animals is greater than or equal to 95%. The primary metabolite 6,7-dihyrdodiol-ibudilast is measurable and has been quantitated in plasma from animals and humans. Finally, biodistribution studies show that ibudilast distributes rapidly, extensively, and reversibly to the central nervous system.

Cognition-enhancing properties of Dimebon in a rat novel object recognition task are unlikely to be associated with acetylcholinesterase inhibition or N-methyl-D-aspartate receptor antagonism

Dimebon (dimebolin) treatment enhances cognition in patients with Alzheimer's disease (AD) or Huntington's disease. Although Dimebon was originally thought to improve cognition and memory through inhibition of acetylcholinesterase (AChE) and the N-methyl-d-aspartate (NMDA) receptor, the low in vitro affinity for these targets suggests that these mechanisms may not contribute to its clinical effects. To test this hypothesis, we assessed whether Dimebon enhances cognition in rats and if such an action is related to either mechanism or additional candidate mechanisms. Acute oral administration of Dimebon to rats (0.05, 0.5, and 5 mg/kg) enhanced cognition in a novel object recognition task and produced Dimebon brain concentrations of 1.7 +/- 0.43, 14 +/- 5.1, and 172 +/- 94 nM, respectively. At these concentrations, Dimebon did not alter the activity of recombinant human or rat brain AChE. Unlike the AChE inhibitors donepezil and galantamine, Dimebon did not change acetylcholine levels in the hippocampus or prefrontal cortex of freely moving rats. Dimebon displays affinity for the NMDA receptor (K(i) = 105 +/- 18 microM) that is considerably higher than brain concentrations associated with cognition enhancement in the novel object recognition task and 200-fold weaker than that of memantine (K(i) = 0.54 +/- 0.05 microM). Dimebon did not block NMDA-induced calcium influx in primary neuronal cells (IC(50) > 50 microM), consistent with a lack of significant effect on this pathway. The cognition-enhancing effects of Dimebon are unlikely to be mediated by AChE inhibition or NMDA receptor antagonism, and its mechanism of action appears to be distinct from currently approved medications for AD.

Ibudilast in healthy volunteers: safety, tolerability and pharmacokinetics with single and multiple doses

AIMS

To investigate the safety, tolerability and pharmacokinetics (PK) of ibudilast after a single-dose and a multiple-dose regimen.

METHODS

Healthy adult male (n = 9) and female (n = 9) volunteers were evaluated over a 17-day stay in a Phase 1 unit. Subjects were randomized 1 : 3 to either oral placebo or ibudilast at 30-mg single administration followed by 14 days of 30 mg b.i.d. Complete safety analyses were performed and, for PK, plasma and urine samples were analysed for ibudilast and its major metabolite.

RESULTS

Ibudilast was generally well tolerated. No serious adverse events occurred. Treatment-related adverse events included hyperhidrosis, headache and nausea. Two subjects discontinued after a few days at 30 mg b.i.d. because of vomiting. Although samples sizes were too small to rule out a sex difference, PK were similar in men and women. The mean half-life for ibudilast was 19 h and median T(max) was 4-6 h. Mean (SD) steady-state plasma C(max) and AUC(0-24) were 60 (25) ng ml(-1) and 1004 (303) ng h ml(-1), respectively. Plasma levels of 6,7- dihydrodiol-ibudilast were approximately 30% of the parent.

CONCLUSIONS

Ibudilast is generally well tolerated in healthy adults when given as a single oral dose of 30 mg followed by 30 mg b.i.d. (60 mg day(-1)) for 14 days. Plasma PK reached steady state within 2 days of starting the b.i.d. regimen. Exposure to ibudilast was achieved of a magnitude comparable to that associated with efficacy in rat chronic pain models.

A T-cell-selective interleukin 2 mutein exhibits potent antitumor activity and is well tolerated in vivo

Human interleukin 2 (IL-2; Proleukin) is an approved therapeutic for advanced-stage metastatic cancer; however, its use is restricted because of severe systemic toxicity. Its function as a central mediator of T-cell activation may contribute to its efficacy for cancer therapy. However, activation of natural killer (NK) cells by therapeutically administered IL-2 may mediate toxicity. Here we have used targeted mutagenesis of human IL-2 to generate a mutein with approximately 3,000-fold in vitro selectivity for T cells over NK cells relative to wild-type IL-2. We compared the variant, termed BAY 50-4798, with human IL-2 (Proleukin) in a therapeutic dosing regimen in chimpanzees, and found that although the T-cell mobilization and activation properties of BAY 50-4798 were comparable to human IL-2, BAY 50-4798 was better tolerated in the chimpanzee. BAY 50-4798 was also shown to inhibit metastasis in a mouse tumor model. These results indicate that BAY 50-4798 may exhibit a greater therapeutic index than IL-2 in humans in the treatment of cancer and AIDS.

Intestinal absorption screening of mixtures from combinatorial libraries in the Caco-2 model

PURPOSE

Understanding how chemical structures influence transport across the intestinal mucosa will greatly enhance the discovery of orally available drugs. In an attempt to accelerate defining such relationships between structure and transport, six arbitrary mixtures of N-substituted glycine (NSG) peptoids containing 24 physicochemically diverse compounds were evaluated in the Caco-2 model of intestinal absorption.

METHODS

Samples were analyzed by HPLC and the areas of the peaks representing the components of each mixture were summed to measure "aggregate" apparent permeability coefficients (Papp), a score of the influence of the common structural element within each mixture towards absorption. Mass spectrometry was used to identify the chemical structure of Caco-2 permeable compounds.

RESULTS

Three linear trimeric mixtures were examined and, for each mixture, none of the components was detected in receiver chambers. It was concluded that the components of these mixtures each had a Papp value less than 0.8 x 10(-6) cm/sec, a permeability less than mannitol. Three dimeric mixtures were examined and they exhibited aggregate P(app) values of 9.2 x 10(-6), 14 x 10(-6) and 6.9 x 10(-6) cm/sec. These transport rates reflected the transport of most of the components of each mixture. Furthermore, the components of the dimeric mixtures which were transported at a rate greater than mannitol were apparently transported by passive mechanisms.

CONCLUSIONS

This study demonstrated that mixtures can be used to study structure-transport relationships in the Caco-2 model. The information obtained from this type of study will be integrated into the design of future chemical libraries. Other potential uses of chemical mixtures with the Caco-2 model are also discussed.

Immunopharmacology and cytokine production of a low-dose schedule of intraperitoneally administered human recombinant interleukin-2 in patients with advanced epithelial ovarian carcinoma

We determined in the peritoneal cavity (p.c.) of epithelial ovarian carcinoma patients during a 4-day treatment cycle of low-dose recombinant human interleukin-2 (rIL-2): (a) pharmacokinetics of IL-2, (b) endogenous cytokine production, and (c) numbers and percentages of peritoneal exudate lymphocytes. We administered 6 x 10(5) IU/m2 of rIL-2 (0.03 mg/m2 Proleukin rIL-2) intraperitoneally (i.p.) over 30 min on each of 4 days. One and one-half liters of D5 0.25 NS was injected i.p. before each rIL-2 infusion. Multiple peritoneal fluid samples were obtained from each of four patients on day 1 and day 4 for detection of IL-2, endogenous cytokines, and soluble IL-2 receptor (IL-2R-alpha). IL-2 concentrations in the peritoneal fluid were determined by bioassay and interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, IL-10, transforming growth factor (TGF)-beta 2, and sIL-2R-alpha by enzyme-linked immunosorbent assay. Numbers of cells per microliter and lymphocyte subpopulation percentages after staining with a panel of monoclonal antibodies were determined on day 1, day 4, and subsequent off-treatment days. IL-2 disappearance in the p.c. was well described by a pharmacokinetic model having constant-rate infusion and biexponential disposition. About 90% of the IL-2 disappearance occurred during the beta-phase, during which IL-2 concentrations were sustained at approximately 10-30 ng/ml (day 1 and day 4) and the median t1/2 beta was 21.5 and 9.2 h on days 1 and 4, respectively. In four of four patients, p.c. production of IL-10 was observed on day 1 and day 4 (maximum 387 pg/ml). Maximum levels of IFN-gamma and sIL-2R-alpha were observed on day 4. (IFN-gamma 217 pg/ml; sIL2-R-alpha: 3486 U/ml). No increases in TNF-alpha or TGF-beta 2 were observed. Large increases in p.c. CD3+, CD4+, CD8+, CD16+, and CD56+ cells were observed. We conclude that biologically active levels of IL-2 are generated in p.c. fluids after i.p. administration of rIL-2 at 0.03 mg/m2.

Pharmacologic characterization of CHIR 2279, an N-substituted glycine peptoid with high-affinity binding for alpha 1-adrenoceptors

We characterize the in vitro and in vivo pharmacology of CHIR 2279, an N-substituted glycine peptoid previously identified from a combinatorial library as a novel ligand to alpha 1-adrenoceptors. Competitive receptor-binding assays with [3H]prazosin showed that CHIR 2279 was similar to prazosin in binding to alpha 1A (rat submaxillary), alpha 1a, alpha 1b, and alpha 1 d (cDNA expressed in LTK- cells) with high and approximately equipotent affinity. Ki values for CHIR 2279 ranged from 0.7 to 3 nM, and were 10-fold weaker than with prazosin. Functional assays for postsynaptic alpha 1-adrenoceptors showed CHIR 2279 was approximately equipotent in antagonizing agonist-induced contractile responses with rat was deferens (alpha 1A), canine prostate (alpha 1A), rat spleen (alpha 1B) and rat aorta (alpha 1D). The pA2 for CHIR 2279 averaged 7.07 in these assays, indicating a 10- to 100-fold lower in vitro potency than prazosin. In dogs, CHIR 2279 antagonized the epinephrine-induced increase in intraurethal pressure (pseudo pA2, 6.86) and in rats antagonized the phenylephrine-induced increase in mean arterial blood pressure. In rats and guinea pigs, CHIR 2279 induced a dose-dependent decrease in mean arterial blood pressure without eliciting the tachycardia commonly observed with other alpha 1-blockers. Pharmacokinetic/pharmacodynamic modeling showed the i.v. system clearance rate of CHIR 2279 was 60 and 104 ml/min/kg in rats and guinea pigs, respectively, and the in vivo potency for mean arterial blood pressure reduction was twice as great in guinea pigs (EC50, 520 ng/ml) than rats (EC50, 1170 ng/ml).

Quantitation of the renal clearance of interleukin-2 using nephrectomized and ureter-ligated rats

The objective of this work was to determine the role of the kidneys in the systemic clearance rate (CL) of interleukin-2 (IL-2). Rats received IL-2 by i.v. bolus and the pharmacokinetic data were found to be well described by a two-compartment, first-order elimination model. With administration of 0.2, 0.5 or 1.0 mg/kg of IL-2 (n = 3 per treatment), the median alpha and beta half-lives (T1/2 alpha, 2.3 min; T1/2 beta, 13.2 min, respectively), initial volume of distribution (V1, 93 ml/kg), volume of distribution at steady state (Vss, 198 ml/kg) and CL (16.8 ml min-1 kg-1) did not vary with the dose (P = .05). This demonstration of first-order kinetics suggested that renal CL remains constant over a range of doses. The pharmacokinetic properties of 1.0 mg/kg of IL-2 were examined after either single or double nephrectomy (n = 3 and 4, respectively), sham operation (n = 4) or no renal operation (n = 4; the "controls"). No difference in median T1/2 alpha, T1/2 beta, V1, Vss or CL was detected between control and sham-operated rats nor between single nephrectomy and sham operation. Compared with sham operation, double nephrectomy showed no significant change in V1 or Vss but the T1/2 alpha and T1/2 beta approximately doubled and CL was reduced by 75%. In a separate experiment, ureter-ligated rats were compared with sham-operated rats. With ureter ligation, T1/2 alpha, T1/2 beta, V1 and Vss were unchanged but CL was reduced by 36%.

Venovenous extracorporeal life support in traumatic bronchial disruption and adult respiratory distress syndrome using surface-heparinized equipment: case report

Venovenous extracorporeal membrane oxygenation and carbon dioxide removal was utilized to support a patient with traumatic bronchial disruption and associated injuries. With use of surface-heparinized perfusion equipment, low levels of anticoagulation were maintained allowing surgical repair of the bronchial injury and recovery from acute respiratory failure without significant hemorrhage.

Nonlinear pharmacokinetics of recombinant human macrophage colony-stimulating factor (M-CSF) in rats

The pharmacokinetics and mechanisms of elimination of recombinant human macrophage-colony stimulating factor (M-CSF) were investigated in rats. Intravenous injections of 0.1, 1 or 10 mg/kg M-CSF were administered and plasma samples were measured for M-CSF by bioassay. Systemic clearance decreased and the shape of the concentration-time curve changed with increasing dose, indicating nonlinear pharmacokinetics. At 10 mg/kg, two half-lives were initially observed, but after about 20 hr the plasma M-CSF suddenly declined with a steep slope. The rapidly declining phase suggested a saturable clearance mechanism that was prominent at low plasma concentrations of M-CSF (below 300 ng/ml) and obscured at high plasma concentrations of M-CSF. The rapid decline of plasma M-CSF occurred at earlier times with multiple daily injections of M-CSF, indicating induction of the saturable clearance mechanism. The rapidly declining phase was inhibited by carrageenan, indicating that saturable clearance might be due to metabolism of M-CSF by macrophages. With ligation of either the renal pedicles or ureters, the apparent half-lives of M-CSF increased by a factor of 2- to 3-fold, while the occurrence of the rapidly declining phase was delayed, but not eliminated. Overall, the results are well described by a two-compartment, first-order elimination model with a parallel Michaelis-Menten elimination pathway. First-order elimination is largely performed by the kidneys and the saturable Michaelis-Menten elimination pathway appears to be mediated by cells of the monocyte-macrophage lineage.

Phase I trial of subcutaneous recombinant macrophage colony-stimulating factor: clinical and immunomodulatory effects

PURPOSE

Recombinant human macrophage colony-stimulating factor (rM-CSF) has been demonstrated to control the growth, differentiation, and function of mononuclear phagocytes. Preclinical studies have indicated antitumor effects, and therefore a phase I trial of rM-CSF in patients with malignancy was initiated. The toxicity and hematologic and immunologic effects were investigated.

PATIENTS AND METHODS

rM-CSF was administered as a subcutaneous injection on days 1 through 5 and 8 through 12. Cycles were repeated every 28 days. Cohorts of four to seven patients received rM-CSF at dose levels from 0.1 to 25.6 mg/m2/d. Forty-two patients received 88 cycles of rM-CSF. All patients had metastatic solid tumors refractory to standard therapy.

RESULTS

The toxicity of rM-CSF was mild. Dose-limiting toxicity included thrombocytopenia (two patients) and iritis (one patient) occurring at a dose of 25.6 mg/m2/d. Hematologic studies demonstrated dose-related monocytosis occurring routinely at doses > or = 3.2 mg/m2/d, and thrombocytopenia. Immunologic studies demonstrated enhanced secretion of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1-beta (IL-1 beta) by monocytes after in vitro stimulation with lipopolysaccharide, and increased expression of TNF-alpha mRNA at higher rM-CSF dose levels. Pharmacokinetic studies demonstrated that the systemic clearance rate of M-CSF increases during week 1 of therapy, resulting in lower blood levels of M-CSF during the second week of therapy.

CONCLUSION

rM-CSF can be safely administered to patients, and has biologic activity on peripheral-blood monocytes.

Benzo[e]pyrene elicits changes in the biochemical activities and chromatographic behavior of murine hepatic cytochromes P-450 that are distinct from those induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin

The objective of this study was to examine the potential for a specific ligand of carcinogen binding protein (CBP) to induce changes in the overall character of hepatic microsomal cytochromes P-450 (P450) and to compare potential changes with those induced by an Ah receptor ligand. Benzo[e]pyrene (BeP) was previously shown to bind CBP with high affinity and Ah receptor with low affinity. In contrast, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) binds Ah receptor avidly and CBP weakly. Hepatic microsomes were prepared from C57BL/6J (B6) and DBA/2J (D2) mice treated with corn oil, BeP or TCDD. Relative to corn oil controls, pretreatment of B6 mice with BeP or TCDD increased the nmol P450/mg microsomal protein content 26 and 28%, respectively. In D2 mice, nmol P450/mg microsomal protein was increased 23% in the BeP pretreatment, while TCDD pretreatment had no effect relative to the corn oil controls. For the O-alkyl ethers of resorufin, rates of metabolism (per nmol P450) were affected differently in B6 and D2 by BeP pretreatment. Pentoxyresorufin O-dealkylase activity was reduced to 44% of control activity in B6 mice and increased 39% relative to controls in D2 mice. BeP pretreatment had no effect on ethoxyresorufin O-dealkylase activity in B6 mice, while this activity was decreased to 58% of controls in D2 mice. Additionally, benzyloxyresorufin O-dealkylase activity was reduced to 65% of control levels in B6 mice and not affected in D2 mice. Methoxyresorufin O-dealkylase activity was reduced in both strains to an average of 55% of control values. As expected, TCDD pretreatment resulted in increases of all O-dealkylations measured in both strains of mouse. For both inbred strains of mouse, anion exchange chromatography revealed a P450 peak associated with BeP pretreatment that was not present in chromatograms generated with corn oil or TCDD pretreatments. Results of enzyme linked immunosorbant assays also indicated that the pattern of P450 isoenzyme expression associated with BeP pretreatment was distinct from that associated with TCDD pretreatment. Overall, these data show that treatment with a specific ligand of CBP induces changes the biochemical activities and chromatographic behavior of P450 isozymes in murine hepatic microsomes. Moreover, they indicate that changes in P450 occurring after treatment with a CBP ligand are distinct from those changes that are associated with treatment with an Ah receptor ligand (TCDD). Differences between B6 and D2 strains suggest that the hepatic P450 changes occurring in response to pretreatment with a CBP ligand may be influenced by the presence of Ah receptor.

Benzo[e]pyrene pretreatment of immature, female C57BL/6J mice results in increased bioactivation of aflatoxin B1 in vitro

Hepatic microsomes were prepared from immature C57BL/6J mice 24 h after receiving intraperitoneal injections of either corn oil, benzo[e]pyrene (BeP, 50 mg/kg) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, 4 x 10(-3) mg/kg). The capacity of these hepatic microsomes to bioactivate aflatoxin B1 (AFB1), 2-aminoanthracene (AA), benzo[a]pyrene (BaP), 3-methylcholanthrene (MC), 7,12-dimethylbenzanthracene (DMBA), BeP and pyrene (PY) was measured using strain TA100 in the Salmonella typhimurium/microsome reversion assay. BeP pretreatment of mice resulted in a 33% increase in mutagenic potency (MP) of AFB1 over the corn oil controls and a 70% increase in MP relative to TCDD-pretreated microsomes. With AA, BaP and DMBA as promutagens, BeP pretreatment reduced MP an average of 24%, while TCDD pretreatment increased MP of these 3 promutagens 263% compared to controls. Since the general effects of BeP and TCDD on murine hepatic cytochrome P-450 (P450)-mediated activities in this study were discordant, it appears that changes in P450 activity by BeP pretreatment are not mediated through the Ah receptor.

Halothane and isoflurane only slightly impair arterial oxygenation during one-lung ventilation in patients undergoing thoracotomy

Controversy exists as to whether the halogenated inhalation (IH) anesthetics impair arterial oxygenation during one-lung ventilation (1-LV). Accordingly, the authors have answered this question in 12 consenting patients who required 1-LV to facilitate the performance of thoracic surgery, by comparing arterial oxygenation during a prolonged period of IH anesthesia with arterial oxygenation during a prolonged period of intravenous (IV) anesthesia during stable 1-LV conditions. The patients were equally divided into halothane and isoflurane groups. Each patient in each IH anesthetic group underwent the following experimental sequence: step 1, two-lung ventilation (2-LV), 1 MAC IH anesthesia; step 2, 1-LV, 1 MAC IH anesthesia; step 3, 1-LV, iv anesthesia; step 4, 2-LV, iv anesthesia. Stable 1-LV conditions were proven by serial arterial blood gas measurement. Conversion from 2-LV to 1-LV during IH anesthesia (step 1 to step 2) caused a very large and significant decrease in PaO2 (from 484 +/- 49 to 116 +/- 61, and from 442 +/- 58 to 232 +/- 97 mmHg in the halothane and isoflurane groups, respectively) and increase in shunt (from 14 +/- 4 to 44 +/- 9, and from 19 +/- 5 to 31 +/- 8% in the halothane and isoflurane groups, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Computerized tomographic diagnosis of paracardiac masses

Paracardiac masses may alter the cardiac contour seen on roentgenograms of the chest so as to mimic configurations associated with cardiac disease. Recently, the use of computerized transmission tomography has proved valuable as a noninvasive method of distinguishing between intrinsic cardiac disease and paracardiac masses. In some cases, the procedure obviates the need for preoperative cardiac catheterization.

A comparison of synthetic absorbable suture with synthetic nonabsorbable suture for construction of tracheal anastomoses

This study compares the use of synthetic absorbable suture (SAS, Vicryl) with that of synthetic nonabsorbable suture (SNS, Ticron) for construction of cervical tracheal anastomoses in the dog. Fourteen mongrel dogs underwent resection of one to four tracheal rings. Paired tracheal anastomoses were constructed, using 10 SAS or 10 SNS. After two months each anastomosis was removed and analyzed. All animals survived with intact anastomoses. There were no visible reactions to the SAS. Twenty-six of 70 SNS developed gross suture granulations. Significant stenosis developed in one of seven SAS and in four of seven SNS anastomoses. Histologic examination revealed no residual inflammatory reaction in the SAS specimens, while the SNS demonstrated a spectrum of inflammatory response that directly correlated in intensity with the gross appearance. These findings support the continued evaluation for the use of SAS in clinical tracheobronchoplastic procedures.

Dressler's syndrome and angina pectoris relieved by surgery

A 49-year-old woman with progressive angina pectoris developed chronic Dressler's syndrome following a second myocardial infarction. Control of the chronic pericarditis required long-term steroid therapy. Because of multiple complications generated by the steroid administration, she underwent coronary angiography followed by pericardiectomy and coronary artery bypass surgery. The patient remains asymptomatic without steroid or antianginal medication five years after surgery.

The recessed chest wall pacemaker pocket

Recurrent pouch problems led to the development of a recessed chest wall pacemaker pocket. Segments of the seventh and eighth ribs were resected in the mid-axillary line resulting in a "tailor-made" space suitable for generator implantation. Follow-up at one year has proven the chest wall to be a satisfactory alternative site for a pacemaker pocket.

An analysis of direct and indirect measurements of left atrial filling pressure

Left ventricular function may be assessed by direct catheter measurements of left atrial pressure or by indirect measurements of pulmonary artery wedge pressure or pulmonary artery end-diastolic pressure. Controversy exists as to how closely the indirect measurements correlate with true left atrial pressure and to which is the most accurate. To clarify this probelm, we studied 43 patients undergoing cardiac surgical procedures with cardiopulmonary bypass. Both left atrial catheters for direct measurement and Swan-Ganz catheters were placed at the time of surgery. All patients were monitored continuously for 48 hours and hourly measurements were recorded. The resultant 1,620 left atrial pressure and pulmonary artery wedge pressure figures and 1,860 left atrial pressure and pulmonary artery end-diastolic wedge pressure measurements were subjected to computer analysis. The following conclusions have been found: (1) Pulmonary artery wedge pressure is a better indirect measure of left atrial pressure than is pulmonary artery end-diastolic wedge pressure (pooled correlation coefficient 0.629); (2) direct left atrial pressure measurement is more reliable and has fewer complications than indirect measurements; (3) there is no consistent correlation between left atrial pressure and central venous pressure (pooled correlation coefficient 0.3). A discussion of our results and the problems associated with left atrial catheters and Swan-Ganz catheters is presented.