Use of a population pharmacokinetic approach for the clinical development of a fixed-dose subcutaneous formulation of trastuzumab

A new subcutaneous (s.c.) trastuzumab formulation provides savings in terms of time and is preferred by patients and health care professionals relative to standard intravenous (i.v.) administration due to simpler and more rapid administration (2-5 minutes). Selection of the s.c. dose was based on a pharmacokinetic bridging approach that aimed to achieve noninferior trastuzumab serum trough concentrations (Ctrough) vs. reference i.v. administration. Using population modeling and simulation, we showed that a fixed 600-mg trastuzumab s.c. dose, administered thrice-weekly (Q3W) without a loading dose, would provide Ctrough (predose Cycle 8) and area under the time-concentration curve (AUC0-21 days, Cycle 7) at least as high as Q3W i.v. administration. The model was retrospectively validated using observed pharmacokinetic data from an independent phase III study of (neo)adjuvant trastuzumab (HannaH). These results provide a strong pharmacokinetic rationale for the trastuzumab s.c. 600-mg fixed dose, supported by the noninferior efficacy of this regimen vs. reference i.v. administration.CPT Pharmacometrics Syst. Pharmacol. (2014) 3, e87; doi:10.1038/psp.2013.63; advance online publication 2 January 2014.

Effect of diabetic retinopathy and panretinal photocoagulation on retinal nerve fiber layer and optic nerve appearance

OBJECTIVE

To determine if panretinal photocoagulation (PRP) alters retinal nerve fiber layer (RNFL) thickness and optic nerve appearance.

METHODS

Patients with diabetes who did and did not undergo PRP and nondiabetic control subjects were enrolled in a prospective study. Participants underwent optical coherence tomography of the peripapillary retina and optic nerve. Stereoscopic optic nerve photographs were graded in a masked fashion.

RESULTS

Ninety-four eyes of 48 healthy individuals, 89 eyes of 55 diabetic patients who did not undergo PRP, and 37 eyes of 24 subjects with diabetes who underwent PRP were included in this study. Eyes that had been treated with PRP had thinner peripapillary RNFL compared with the other groups; this was statistically significantly different in the inferior (P = .004) and nasal (P = .003) regions. Optic nerve cupping did not increase with severity of disease classification, but the proportion of optic nerves graded as suspicious for glaucoma or as having nonglaucomatous optic neuropathy did (P = .008). These grading categories were associated with thinner RNFL measurements.

CONCLUSIONS

Diabetic eyes that have been treated with PRP have thinner RNFL than nondiabetic eyes. Optic nerves in eyes treated with PRP are more likely to be graded as abnormal, but their appearance is not necessarily glaucomatous and may be related to thinning of the RNFL.

Clinical pharmacokinetics of erlotinib (E) in glioblastoma multiforme (GBM) patients and its implication for dosing

2010

Background: E is an orally active, highly potent and selective inhibitor of the epidermal growth factor receptor (EGFR). Preliminary results from both Phase I and Phase II trials of E in GBM patients have been reported (ASCO 2003, Abs#394 and ASCO 2004, Abs#1555). The purpose of this analysis is to characterize E PK in this patient population when administered with or without CYP3A4 enzyme inducing anti-epileptic drugs (EIAEDs) and to identify a dose to provide equivalent exposure during concomitant therapy in GBM patients. Methods: Intensive PK data were collected in the Phase I study and plasma trough concentration data were collected in the Phase II study at steady-state. A total of 775 E concentrations from 107 patients were available for the analysis. A population PK approach (NONMEM) was used to characterize the clinical PK in this patient population and the effect of EIAEDs on the PK of E. Results: Co-administration of EIAEDs was shown to increase the E clearance (CL/F) by 230% in GBM patients. This effect is similar to that seen in a previous drug-drug interaction study with a CYP3A4 enzyme inducer (rifampicin) in healthy volunteers. For patients with no EIAEDs, population estimates and the %CV of inter-individual variance for CL/F and Vc/F of erlotinib were 5.63 L/hr (44%) and 388 L (40%), respectively. Conclusions: Based on the modeling results, for GBM patients with EIAEDs, an estimate of erlotinib dose of 500 mg/d is needed to achieve an equivalent exposure as patients who receive the dose of 150 mg/d with no EIAEDs. The new population PK model provides an operational tool to predict E exposure during treatment, and simulate alternative dosing regimens for GBM patients.

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Statin-AE: a novel angiostatin-endostatin fusion protein with enhanced antiangiogenic and antitumor activity

The combination of angiostatin and endostatin has been shown to have synergistic antiangiogenic and antitumor effects when the genes for these proteins are delivered to tumor cells by retroviral gene transfer. Here we report the construction of a murine angiostatin-endostatin fusion gene (Statin-AE) which shows enhanced antiangiogenic activity on human umbilical vein endothelial cell (HUVEC) tube formation in vitro compared with angiostatin or endostatin alone. Similarly, the fusion gene demonstrates antiangiogenic effects in vivo and antitumor activity in a B16F10 melanoma model when co-delivered by retroviral packaging cell inoculation in mice. The fusion gene demonstrates significantly greater inhibition of tumor growth compared with angiostatin, endostatin or the combination of genes.

Combination angiostatin and endostatin gene transfer induces synergistic antiangiogenic activity in vitro and antitumor efficacy in leukemia and solid tumors in mice

Angiostatin and endostatin are potent endothelial cell growth inhibitors that have been shown to inhibit angiogenesis in vivo and tumor growth in mice. However, tumor shrinkage requires chronic delivery of large doses of these proteins. Here we report synergistic antitumor activity and survival of animals when these factors are delivered in combination to tumors by retroviral gene transfer. We have demonstrated this efficacy in both murine leukemia and melanoma models. Complete loss of tumorigenicity was seen in 40% of the animals receiving tumors transduced by the combination of angiostatin and endostatin in the leukemia model. The synergy was also demonstrated in vitro on human umbilical vein endothelial cell differentiation and this antiangiogenic activity may suggest a mechanism for the antitumor activity in vivo. These findings imply separate pathways by which angiostatin and endostatin mediate their antiangiogenic effects. Together, these data suggest that a combination of antiangiogenic factors delivered by retroviral gene transfer may produce synergistic antitumor effects in both leukemia and solid tumors, thus avoiding long-term administration of recombinant proteins. The data also suggest that novel combinations of antiangiogenic factors delivered into tumors require further investigation as therapeutic modalities.

Treatment of poor prognosis AML patients using PSC833 (valspodar) plus mitoxantrone, etoposide, and cytarabine (PSC-MEC)

The failure of convenional chemotherapy in relapsed or refractory and other poor risk AML patients has been linked to expression of the multidrug resistance gene (mdr 1) product P-glycoprotein (P-gp). PSC 833 is a non-competitive inhibitor of P-gp and has been shown in vitro and in vivo to restore sensitivity of resistant tumor cells to anticancer drugs (ACDs). Induction chemotherapy consisting of cytarabine (C) in combination with PSC 833 and escalating doses of mitoxantrone (M) and etoposide (E) over 5 or 6 days were tested in two phase I/II studies in poor prognosis AML. Overall, 59 patients were evaluated: their age ranged between 18 and 70 years. Fourteen patients had primary refractory disease, 25 had relapsed within 9 months from first complete remission (CR), 5 were in second relapse, 10 had secondary AML, and 4 had relapsed post-bone marrow transplantation. PSC 833 was given as a constant i.v. infusion at a rate of 10 mg/kg/24 h for 5 or 6 days, depending on the duration of chemotherapy. In both studies a loading dose of 2 mg/kg of PSC 833 was given on day 1. In the 5-day regimen, the final study doses of the cytotoxic agents were C 1 g/m2/d, M 4.0 mg/m2/d, and E 40 mg/m2/d. In the 6-day regimen, the final study doses of the cytotoxic agents were C 1 g/m2/d, M 4.5 mg/m2/d and E 30 mg/m2/d. The combined efficacy results of both studies indicate that PSC-MEC is active in all treatment indications, complete remission being achieved in 2/5 (40%) second relapses, 8/25 (32%) early relapses, 3/10 (30%) secondary AML, 3/15 (20%) refractory patients and 1/4 (25%) post-BMT relapses. Based on historical controls, this observed overall CR rate (29%) is higher than expected in this high risk patient population. Our data indicate that, in refractory/relapsed AML patients, PSC-MEC regimens had encouraging antileukemic effects, is well tolerated, and has led to Phase III trials in this setting.

Breast cancer screening, diagnosis, and treatment

The incidence of breast cancer in US women remains disturbingly high, and unfortunately primary care physicians still frequently encounter patients in whom the disease is suspected or, even worse, confirmed. Fortunately, however, the body of knowledge surrounding the disease has grown dramatically during the past decade, and major advances have been made in the understanding of breast cancer risk, prevention, diagnosis, and treatment. Controversies persist, particularly those concerning the screening of younger women, but consensus now exists regarding many clinical issues relevant to primary care practice. Although multidisciplinary subspecialty expertise must be made available to all women with known or suspected breast cancer, the primary care physician has an important role to play when dealing with patients with this condition. The following article focuses on what primary care practitioners need to know to expertly contribute to the diagnosis, counseling, and initial treatment of women with this disease.

Treatment of refractory and relapsed acute myelogenous leukemia with combination chemotherapy plus the multidrug resistance modulator PSC 833 (Valspodar)

A potential mechanism of chemotherapy resistance in acute myeloid leukemia (AML) is the multidrug resistance (MDR-1) gene product P-glycoprotein (P-gp), which is often overexpressed in myeloblasts from refractory or relapsed AML. In a multicenter phase II clinical trial, 37 patients with these poor risk forms of AML were treated with PSC 833 (Valspodar; Novartis Pharmaceutical Corporation, East Hanover, NJ), a potent inhibitor of the MDR-1 efflux pump, plus mitoxantrone, etoposide, and cytarabine (PSC-MEC). Pharmacokinetic (PK) interactions of etoposide and mitoxantrone with PSC were anticipated, measured in comparison with historical controls without PSC, and showed a 57% decrease in etoposide clearance (P =.001) and a 1.8-fold longer beta half-life for mitoxantrone in plasma (P <.05). The doses of mitoxantrone and etoposide were substantially reduced to compensate for these interactions and clinical toxicity and in Cohort II were well tolerated at dose levels of 4 mg/m2 mitoxantrone, 40 mg/m2 etoposide, and 1 g/m2 C daily for 5 days. Overall, postchemotherapy marrow hypoplasia was achieved in 33 patients. Twelve patients (32%) achieved complete remission, four achieved partial remission, and 21 failed therapy. The PK observations correlated with enhanced toxicity. The probability of an infectious early death was 36% (4 of 11) in patients with high PK parameters for either drug versus 5% (1 of 20) in those with lower PK parameters (P =.04). P-gp function was assessed in 19 patients using rhodamine-123 efflux and its inhibition by PSC. The median percentage of blasts expressing P-gp was increased (49%) for leukemic cells with PSC-inhibitable rhodamine efflux compared with 17% in cases lacking PSC-inhibitable efflux (P =.004). PSC-MEC was relatively well tolerated in these patients with poor-risk AML, and had encouraging antileukemic effects. The Eastern Cooperative Oncology Group is currently testing this regimen versus standard MEC chemotherapy in a phase III trial, E2995, in a similar patient population.

The use of cardiac biopsy to demonstrate reduced cardiotoxicity in AIDS Kaposi's sarcoma patients treated with pegylated liposomal doxorubicin

BACKGROUND

Pegylated liposomal doxorubicin (PL-DOX) has been shown in preclinical models to induce less cardiotoxicity than non-liposomal doxorubicin. Endomyocardial biopsy is a highly sensitive and specific method for detecting anthracycline-induced cardiac damage.

PATIENTS AND METHODS

Myocardial tissue from ten KS patients who had received cumulative PL-DOX (20 mg/m2/biweekly) of 440-840 mg/m2 was evaluated for evidence of anthracycline-induced cardiac damage. Controls were assembled from patients who had received cumulative doxorubicin doses of 174-671 mg/m2 in two earlier cardiac biopsy protocols. Two control groups were selected on the basis of both cumulative (+/- 10 mg/m2) and peak doxorubicin dose (60 or 20 mg/m2, control group 1), or peak dose alone (20 mg/m2, control group 2).

RESULTS

PL-DOX patients had significantly lower biopsy scores compared with those of doxorubicin controls despite higher cumulative doses of anthracycline. The median biopsy scores for the PL-DOX and doxorubicin groups, respectively, were 0.3 vs. 3.0 (P = 0.002, Cochran-Mantel-Haenszel row mean difference test) for group 1 and 1.25 for group 2 (P < 0.001, Wilcoxon rank-sum test).

CONCLUSIONS

Less severe cardiac changes were seen in patients given PL-DOX relative to historical control patients given comparable cumulative doses of doxorubicin.

Pharmacokinetics of cyclosporine after renal transplant in children

The pharmacokinetics of cyclosporine and the relationship between blood levels and average drug concentration were prospectively evaluated in 18 children 1 month after renal transplantation. All children had normal renal function and no hepatic or gastrointestinal dysfunction. Cyclosporine was administered after an overnight fast, and serial blood samples were drawn over a 24-hour period. Analysis of cyclosporine levels was performed by means of monoclonal radio immunoassay on whole blood. Children were divided into three age groups for comparison: 2-5 years, 5-10 years, and > 10 years. There were no differences between age groups in serum protein, serum lipids, or hemoglobin levels, or in the pharmacokinetic parameters of cyclosporine except as follows: significant differences were noted in cyclosporine dose based on body weight, apparent steady-state volume of distribution, and apparent blood clearance, with the youngest children (2-5) requiring higher doses, a relative greater distribution, and exhibiting more rapid drug clearance than those > 10 years of age. In addition, we observed diurnal variation in trough levels, with morning levels (0 hr) significantly higher than those obtained in the evening (12 hours after administration of cyclosporine). Trough levels demonstrated a fair correlation with area under the concentration-time curve (AUC) and average concentration (Cav), but an abbreviated kinetic profile using cyclosporine levels 1 and 3.5 hours after administration accurately predicted AUC.

Insights into mechanisms of cisplatin resistance and potential for its clinical reversal

Cisplatin in combination with other cytotoxic agents is the backbone for a potential cure of testicular germ cell neoplasms and is a critical factor in the substantial activity observed in the treatment of small cell lung cancer, bladder cancer, and ovarian germ cell tumors. Resistance to cisplatin at the onset of treatment or at relapse limits its curative potential, however. Laboratory studies using both cells selected for cisplatin resistance by exposure to sublethal concentrations and biopsy specimens from patients' tumors provide insights for the potential mechanisms of resistance. The mechanisms identified in vitro include a complex and wide array of related and unrelated pathways such as alterations in cellular drug transport, enhanced DNA repair dependent and independent of signal transduction pathways, and enhanced intracellular detoxification such as glutathione and metallothionein systems. Studies of these mechanisms have identified a number of agents with known potential for administration to humans and that reverse cisplatin resistance in vitro; for example, reversal of cellular accumulation defects by dipyridamole; inhibition of DNA repair by hydroxyurea, pentoxifylline, and novobiocin; inhibition of the glutathione system by ethacrynic acid and buthionine sulfoximine; and inhibition of signal transduction pathways by cyclosporine, tamoxifen, and calcium channel-blocking agents. Current phase I clinical trials are focusing on the most effective doses and schedules to administer these agents in combination with cisplatin. Initial uncontrolled trials in limited numbers of patients suggest that the addition of modulators of cisplatin has the potential to reverse resistance in patients previously failing therapy. Another promising avenue for circumventing cisplatin resistance is the development of noncross-resistant platinum analogs.

The impact of body weight on cyclosporine pharmacokinetics in renal transplant recipients

In order to assess the effect of body weight on cyclosporine disposition, 45 adult uremic candidates for renal transplantation underwent detailed nutritional assessment and pharmacokinetic analysis. There were 10 obese and 35 nonobese patients defined as actual body weight (ABW) greater than 125 Per cent of ideal body weight (IBW), and arm fat area greater than 90th percentile. There was no significant difference in demographic variables such as age, sex, number of diabetics, IBW, serum lipids, or liver function tests between the 2 groups. Although there was a significant difference in ABW, pharmacokinetic analyses failed to demonstrate significant differences in bioavailability, elimination half-life, clearance, or apparent steady state volume of distribution when these calculations were normalized by IBW, body surface area, or as absolute values. Multiple stepwise linear regression failed to demonstrate a significant correlation between serum lipids or body size measurements and these parameters. When dosed according to ABW, obese recipients of renal allografts had a mean serum RIA trough level of 227 ng/ml as compared to 121 ng/ml in nonobese recipients on day 7. Therefore in order to achieve comparable drug concentrations in the early transplant period, CsA should be given to obese patients based on their IBW.