First-in-human phase 0 study of 111In-CHX-A"-DTPA trastuzumab for HER2 tumor imaging.

INTRODUCTION: Tumors over-expressing the human epithelial receptor 2 (HER2) or exhibiting amplification or mutation of its proto-oncogene have a poorer prognosis. Using trastuzumab and/or other HER2 targeted therapies can increase overall survival in patients with HER2(+) tumors making it critical to accurately identify patients who may benefit. We report on a Phase 0 study of the imaging agent, 111In-CHX-A"-DTPA trastuzumab, in patients with known HER2 status to evaluate its safety and biodistribution and to obtain preliminary data regarding its ability to provide an accurate, whole-body, non-invasive means to determine HER2 status. METHODS: 111In-CHX-A"-DTPA trastuzumab was radiolabeled on-site and slowly infused into 11 patients who underwent single (n=5) or multiple (n=6) ɣ-camera (n=6) and/or SPECT (n=8) imaging sessions. RESULTS: No safety issues were identified. Visual and semi-quantitative imaging data were concordant with tissue HER2 expression profiling in all but 1 patient. The biodistribution showed intense peak liver activity at the initial imaging timepoint (3.3h) and a single-phase clearance fit of the average time-activity curve (TAC) estimated t1/2=46.9h (R2=0.97; 95%CI 41.8 to 53h). This was followed by high gastrointestinal (GI) tract activity peaking by 52h. Linear regression predicted GI clearance by 201.2h (R2 =0.96; 95%CI 188.5 to 216.9h). Blood pool had lower activity with its maximum on the initial images. Non-linear regression fit projected a t1/2=34.2h (R2 =0.96; 95%CI 25.3 to 46.3h). Assuming linear whole-body clearance, linear regression projected complete elimination (x-intercept) at 256.5hr (R2=0.96; 95%CI 186.1 to 489.2h). CONCLUSION: 111In-CHX-A"-DTPA trastuzumab can be safely imaged in humans. The biodistribution allowed for visual and semiquantitative analysis with results concordant with tissue expression profiling in 10 of 11 patients. Advances in Knowledge and Implications for Patient Care Using readily available components and on-site radiolabeling 111In-CHX-A"-DTPA trastuzumab SPECT imaging may provide an economical, non-invasive means to detect HER2 over-expression.

ANG1005 for breast cancer brain metastases: correlation between 18F-FLT-PET after first cycle and MRI in response assessment.

PURPOSE: Improved therapies and imaging modalities are needed for the treatment of breast cancer brain metastases (BCBM). ANG1005 is a drug conjugate consisting of paclitaxel covalently linked to Angiopep-2, designed to cross the blood-brain barrier. We conducted a biomarker substudy to evaluate 18F-FLT-PET for response assessment. METHODS: Ten patients with measurable BCBM received ANG1005 at a dose of 550 mg/m2 IV every 21 days. Before and after cycle 1, patients underwent PET imaging with 18F-FLT, a thymidine analog, retention of which reflects cellular proliferation, for comparison with gadolinium-contrast magnetic resonance imaging (Gd-MRI) in brain metastases detection and response assessment. A 20 % change in uptake after one cycle of ANG1005 was deemed significant. RESULTS: Thirty-two target and twenty non-target metastatic brain lesions were analyzed. The median tumor reduction by MRI after cycle 1 was -17.5 % (n = 10 patients, lower, upper quartiles: -25.5, -4.8 %) in target lesion size compared with baseline. Fifteen of twenty-nine target lesions (52 %) and 12/20 nontarget lesions (60 %) showed a ≥20 % decrease post-therapy in FLT-PET SUV change (odds ratio 0.71, 95 % CI: 0.19, 2.61). The median percentage change in SUVmax was -20.9 % (n = 29 lesions; lower, upper quartiles: -42.4, 2.0 %), and the median percentage change in SUV80 was also -20.9 % (n = 29; lower, upper quartiles: -49.0, 0.0 %). Two patients had confirmed partial responses by PET and MRI lasting 6 and 18 cycles, respectively. Seven patients had stable disease, receiving a median of six cycles. CONCLUSIONS: ANG1005 warrants further study in BCBM. Results demonstrated a moderately strong association between MRI and 18F-FLT-PET imaging.

Modulation of tumor eIF4E by antisense inhibition: A phase I/II translational clinical trial of ISIS 183750-an antisense oligonucleotide against eIF4E-in combination with irinotecan in solid tumors and irinotecan-refractory colorectal cancer.

The eukaryotic translation initiation factor 4E (eIF4E) is a potent oncogene that is found to be dysregulated in 30% of human cancer, including colorectal carcinogenesis (CRC). ISIS 183750 is a second-generation antisense oligonucleotide (ASO) designed to inhibit the production of the eIF4E protein. In preclinical studies we found that EIF4e ASOs reduced expression of EIF4e mRNA and inhibited proliferation of colorectal carcinoma cells. An additive antiproliferative effect was observed in combination with irinotecan. We then performed a clinical trial evaluating this combination in patients with refractory cancer. No dose-limiting toxicities were seen but based on pharmacokinetic data and tolerability the dose of irinotecan was reduced to 160 mg/m(2) biweekly. Efficacy was evaluated in 15 patients with irinotecan-refractory colorectal cancer. The median time of disease control was 22.1 weeks. After ISIS 183750 treatment, peripheral blood levels of eIF4E mRNA were decreased in 13 of 19 patients. Matched pre- and posttreatment tumor biopsies showed decreased eIF4E mRNA levels in five of nine patients. In tumor tissue, the intracellular and stromal presence of ISIS 183750 was detected by IHC in all biopsied patients. Although there were no objective responses stable disease was seen in seven of 15 (47%) patients who were progressing before study entry, six of whom were stable at the time of the week 16 CT scan. We were also able to confirm through mandatory pre- and posttherapy tumor biopsies penetration of the ASO into the site of metastasis.

Targeting the microenvironment of pancreatic cancer: overcoming treatment barriers and improving local immune responses.

Historically, patients diagnosed with metastatic pancreatic cancer have faced a grim prognosis. The survival benefit seen with systemic chemotherapies and even combinations thereof have been disappointing. However, growing data suggest that the microenvironment of pancreatic cancer may be contributing to this poor prognosis. This microenvironment has a dense fibrotic stroma, and is hypoxic and highly immunosuppressive, all of which pose barriers to treatment. Newer strategies looking to disrupt the fibrotic stroma, target hypoxic areas, and improve local immune responses in the tumor microenvironment are currently undergoing clinical evaluation and seem to offer great promise. In addition to these therapies, preclinical work evaluating novel cytotoxic agents including nanoparticles has also been encouraging. While much research still needs to be done, these strategies offer new hope for patients with pancreatic cancer.

A phase II study of TRC105 in patients with hepatocellular carcinoma who have progressed on sorafenib.

BACKGROUND: Endoglin is an endothelial cell membrane receptor essential for angiogenesis and highly expressed on the vasculature of many tumor types, including hepatocellular carcinoma (HCC). TRC105 is a chimeric IgG1 anti-CD105 monoclonal antibody that inhibits angiogenesis and tumor growth by endothelial cell growth inhibition, ADCC and apoptosis, and complements VEGF inhibitors. OBJECTIVE: The aim of this phase II study was to evaluate the efficacy of anti-endoglin therapy with TRC105 in patients with advanced HCC, post-sorafenib. METHODS: Patients with HCC and compensated liver function (Childs-Pugh A/B7), ECOG 0/1, were enrolled to a single-arm, phase II study of TRC105 15 mg/kg IV every two weeks. Patients must have progressed on or been intolerant of prior sorafenib. A Simon optimal two-stage design was employed with a 50% four-month PFS target for progression to the second stage. Correlative biomarkers evaluated included DCE-MRI as well as plasma levels of angiogenic biomarkers and soluble CD105. RESULTS: A total accrual of 27 patients was planned. However, because of lack of efficacy and in accordance with the Simon two-stage design, 11 patients were enrolled. There were no grade 3/4 treatment-related toxicities. Most frequent toxicities were headache (G2; N = 3) and epistaxis (G1; N = 4). One patient had a confirmed partial response by standard RECIST criteria and biologic response on DCE-MRI but the four-month PFS was insufficient to proceed to the second stage of the study. CONCLUSIONS: TRC105 was well tolerated in this HCC population following sorafenib. Although there was evidence of clinical activity, this did not meet prespecified criteria to proceed to the second stage. TRC105 development in HCC continues as combination therapy with sorafenib.

Angiogenesis in spontaneous tumors and implications for comparative tumor biology.

Blood supply is essential for development and growth of tumors and angiogenesis is the fundamental process of new blood vessel formation from preexisting ones. Angiogenesis is a prognostic indicator for a variety of tumors, and it coincides with increased shedding of neoplastic cells into the circulation and metastasis. Several molecules such as cell surface receptors, growth factors, and enzymes are involved in this process. While antiangiogenic therapy for cancer has been proposed over 20 years ago, it has garnered much controversy in recent years within the scientific community. The complex relationships between the angiogenic signaling cascade and antiangiogenic substances have indicated the angiogenic pathway as a valid target for anticancer drug development and VEGF has become the primary antiangiogenic drug target. This review discusses the basic and clinical perspectives of angiogenesis highlighting the importance of comparative biology in understanding tumor angiogenesis and the integration of these model systems for future drug development.

The CYP2C19*17 variant is not independently associated with clopidogrel response.

BACKGROUND: Cytochrome P450 2C19 (CYP2C19) is the principal enzyme responsible for converting clopidogrel into its active metabolite, and common genetic variants have been identified, most notably CYP2C19*2 and CYP2C19*17, that are believed to alter its activity and expression, respectively. OBJECTIVE: We evaluated whether the consequences of the CYP2C19*2 and CYP2C19*17 variants on clopidogrel response were independent of each other or genetically linked through linkage disequilibrium (LD). PATIENTS/METHODS: We genotyped the CYP2C19*2 and CYP2C19*17 variants in 621 members of the Pharmacogenomics of Anti-Platelet Intervention (PAPI) Study and evaluated the effects of these polymorphisms singly and then jointly, taking into account LD, on clopidogrel prodrug level, clopidogrel active metabolite level, and adenosine 5'-diphosphate (ADP)-stimulated platelet aggregation before and after clopidogrel exposure. RESULTS: The CYP2C19*2 and CYP2C19*17 variants were in LD (|D'| = 1.0; r(2)  = 0.07). In association analyses that did and did not account for the effects of CYP2C19*17, CYP2C19*2 was strongly associated with levels of clopidogrel active metabolite (ß = -5.24, P = 3.0 × 10(-9) and ß = -5.36, P = 3.3 × 10(-14) , respectively) and posttreatment ADP-stimulated platelet aggregation (ß = 7.55, P = 2.9 × 10(-16) and ß = 7.51, P = 7.0 × 10(-15) , respectively). In contrast, CYP2C19*17 was marginally associated with clopidogrel active metabolite levels and ADP-stimulated platelet aggregation before (ß = 1.57, P = 0.04 and ß = -1.98, P = 0.01, respectively) but not after (ß = 0.40, P = 0.59 and ß = -0.13, P = 0.69, respectively) adjustment for the CYP2C19*2 variant. Stratified analyses of CYP2C19*2/CYP2C19*17 genotype combinations revealed that CYP2C19*2, and not CYP2C19*17, was the primary determinant in altering clopidogrel response. CONCLUSIONS: Our results suggest that CYP2C19*17 has a small (if any) effect on clopidogrel-related traits and that the observed effect of this variant is due to LD with the CYP2C19*2 loss-of-function variant.

OATP1B1 polymorphism as a determinant of erythromycin disposition.

Previous studies have demonstrated that the pharmacokinetic profile of erythromycin, a probe for CYP3A4 activity, is affected by inhibitors or inducers of hepatic solute carriers. We hypothesized that these interactions are mediated by OATP1B1 (gene symbol, SLCO1B1), a polypeptide expressed on the basolateral surface of hepatocytes. Using stably transfected Flp-In T-Rex293 cells, erythromycin was found to be a substrate for OATP1B1*1A (wild type) with a Michaelis-Menten constant of ~13 µmol/l, and that its transport was reduced by ~50% in cells expressing OATP1B1*5 (V174A). Deficiency of the ortholog transporter Oatp1b2 in mice was associated with a 52% decrease in the metabolic rate of erythromycin (P = 0.000043). In line with these observations, in humans the c.521T>C variant in SLCO1B1 (rs4149056), encoding OATP1B1*5, was associated with a decline in erythromycin metabolism (P = 0.0072). These results suggest that impairment of OATP1B1 function can alter erythromycin metabolism, independent of changes in CYP3A4 activity.

Effect of ABCC2 (MRP2) transport function on erythromycin metabolism.

The macrolide antiobiotic erythromycin undergoes extensive hepatic metabolism and is commonly used as a probe for cytochrome P450 (CYP) 3A4 activity. By means of a transporter screen, erythromycin was identified as a substrate for the transporter ABCC2 (MRP2) and its murine ortholog, Abcc2. Because these proteins are highly expressed on the biliary surface of hepatocytes, we hypothesized that impaired Abcc2 function may influence the rate of hepatobiliary excretion and thereby enhance erythromycin metabolism. Using Abcc2 knockout mice, we found that Abcc2 deficiency was associated with a significant increase in erythromycin metabolism, whereas murine Cyp3a protein expression and microsomal Cyp3a activity were not affected. Next, in a cohort of 108 human subjects, we observed that homozygosity for a common reduced-function variant in ABCC2 (rs717620) was also linked to an increase in erythromycin metabolism but was not correlated with the clearance of midazolam. These results suggest that impaired ABCC2 function can alter erythromycin metabolism, independent of changes in CYP3A4 activity.

A pharmacogenetic study of docetaxel and thalidomide in patients with castration-resistant prostate cancer using the DMET genotyping platform.

The anticancer agent docetaxel shows significant inter-individual variation in its pharmacokinetic and toxicity profile. Thalidomide is an active anticancer agent and also shows wide pharmacological variation. Past pharmacogenetic research has not explained this variation. Patients with prostate cancer enrolled in a randomized phase II trial using docetaxel and thalidomide versus docetaxel alone were genotyped using the Affymetrix DMET 1.0 platform, which tests for 1256 genetic variations in 170 drug disposition genes. Genetic polymorphisms were analyzed for associations with clinical response and toxicity. In all, 10 single-nucleotide polymorphisms (SNPs) in three genes were potentially associated with response to therapy: peroxisome proliferator-activated receptor-delta (PPAR-delta), sulfotransferase family, cytosolic, 1C, member 2 (SULT1C2) and carbohydrate (chondroitin 6) sulfotransferase 3 (CHST3). In addition, 11 SNPs in eight genes were associated with toxicities to treatment: spastic paraplegia 7 (pure and complicated autosomal recessive) (SPG7), CHST3, cytochrome P450, family 2, subfamily D, polypeptide 6 (CYP2D6), N-acetyltransferase 2 (arylamine N-acetyltransferase) (NAT2), ATP-binding cassette, sub-family C (CFTR/MRP), member 6 (ABCC6), ATPase, Cu++ transporting, alpha polypeptide (ATP7A), cytochrome P450, family 4, subfamily B, polypeptide 1 (CYP4B1) and solute carrier family 10 (sodium/bile acid cotransporter family), member 2 (SLC10A2). Genotyping results between drug metabolizing enzymes and transporters (DMET) and direct sequencing showed >96% of concordance. These findings highlight the role that non-CYP450 metabolizing enzymes and transporters may have in the pharmacology of docetaxel and thalidomide.

Modulation of erlotinib pharmacokinetics in mice by a novel cytochrome P450 3A4 inhibitor, BAS 100.

Administration of BAS 100, a novel mechanism-based CYP3A4 inhibitor isolated from grapefruit juice, resulted in a 2.1-fold increase in erlotinib exposure following oral administration to wild-type and humanized CYP3A4 transgenic mice. This study illustrates the potential of BAS 100 to increase the low and variable oral bioavailability of erlotinib in cancer patients.

The Pharm.D. investigator in clinical pharmacology: supply and demand.

The field of clinical pharmacology is the discipline engaged in optimal drug discovery, development, and use, based on an in-depth knowledge of human pharmacology and therapeutics. Although many think clinical pharmacology is simply the study of pharmacokinetics, pharmacodynamics, and pharmacogenetics, the role of the clinical pharmacologists covers all avenues of drug discovery, development, therapeutics, optimal drug therapy, and education. This expanded understanding is important as we start to address the overwhelming mandate and the unfortunate shortage of qualified investigators in the field (both physicians and non-physicians).

Variants in the SLCO1B3 gene: interethnic distribution and association with paclitaxel pharmacokinetics.

To explore retrospectively the relationships between paclitaxel pharmacokinetics and three known, non-synonymous single-nucleotide polymorphisms (SNPs) in SLCO1B3, the gene encoding organic anion transporting polypeptide (OATP)1B3. Accumulation of [(3)H]paclitaxel was studied in Xenopus laevis oocytes injected with cRNA of Oatp1b2, OATP1A2, OATP1B1, OATP1B3, OAT1, OAT3, OCT1, and NTCP. The 334T>G (Ser112Ala), 699G>A (Met233Ile), and 1564G>T (Gly522Cys) loci of SLCO1B3 were screened in 475 individuals from five ethnic groups and 90 European Caucasian cancer patients treated with paclitaxel. Only OATP1B3 was capable of transporting paclitaxel to a significant extent (P=0.003). The 334T>G and 699G>A SNPs were less common in the African-American and Ghanaian populations (P<0.000001). Paclitaxel pharmacokinetics were not associated with the studied SNPs or haplotypes (P>0.3). The studied SNPs in SLCO1B3 appear to play a limited role in the disposition of paclitaxel, although their clinical significance in other ethnic populations remains to be investigated.

Antimyeloma activity of two novel N-substituted and tetraflourinated thalidomide analogs.

Thalidomide alone or in combination with steroids has significant activity in multiple myeloma (MM). However, given its teratogenic potential, analogs have been synthesized, retaining the anti-MM activity without these side effects. We examined the anti-MM activity of two thalidomide analogs, CPS11 and CPS49. Direct cytotoxicity of the drugs on myeloma cell lines and patient myeloma cells was examined using thymidine uptake. Tumor cell apoptosis was evaluated by flow cytometry as well as Western blotting for caspase and PARP cleavage. Cellular signaling events were examined by immunoblotting for phosphorylated proteins. Both drugs inhibit proliferation of several MM cell lines sensitive and resistant to conventional therapies. They decrease secretion of IL-6, IGF, and VEGF by marrow stromal cells. Importantly, they inhibit proliferation of MM cells adherent to stromal cells. These drugs induce caspase-mediated apoptosis in MM cell lines, as well as patient MM cells. They inhibit the PI3K/Akt and JAK/STAT (signal transducers and activators of transcription) pathways in MM cells and are antiangiogenic in matrigel-based assays. CPS11 and CPS49 have potent antimyeloma activity and can overcome protective effects of the tumor microenvironment. They have potent antiangiogenic activity and direct effect on bone marrow stroma. These encouraging preclinical data provide the basis for further evaluation in the clinic.

Microarray gene expression profiling of angiogenesis inhibitors using the rat aortic ring assay.

The rat aortic ring assay has been previously described as a useful ex vivo model for analyzing the biological activity of various inhibitors of angiogenesis. Rat aortic rings are exposed to antiangiogenic agents for a five-day incubation period. Then, the degree of microvessel outgrowth from the rings is analyzed and quantified. In contrast to most in vitro angiogenesis assays, the rat aortic ring model provides a unique microenvironment to evaluate the interaction of various cell types and biological factors for their influence on angiogenesis. Microarray analysis is an accepted method for the evaluation of gene expression profiles and can be used to better understand changes in gene expression that occur when rat aortic rings are exposed to a particular biological agent. Here we describe a method of using microarray technology to evaluate the modulation of gene expression in angiogenesis using the rat aortic ring assay.

Thalidomide, an antiangiogenic agent with clinical activity in cancer.

Despite the teratogenic past of thalidomide, there is recent evidence indicating the drug's efficacy in the management of various diseases from immune disorders to cancers. The history, pharmacodynamic and pharmacokinetic properties of thalidomide in the clinic are discussed in this review article.

A Phase I study of infusional vinblastine in combination with the P-glycoprotein antagonist PSC 833 (valspodar).

BACKGROUND: PSC 833 is a second-generation P-glycoprotein (Pgp) antagonist developed to reverse multidrug resistance (MDR). The authors conducted a Phase I study of orally administered PSC 833 in combination with vinblastine administered as a 5-day continuous infusion. METHODS: Seventy-nine patients with advanced malignant disease were enrolled in the trial and treated with escalating doses of PSC 833. Pharmacokinetic interactions between PSC 833 and vinblastine were anticipated. Accordingly, when dose limiting toxicities were observed, the dose of vinblastine was reduced as PSC 833 was escalated. Three schedules and two formulations of PSC 833 were used in the study. RESULTS: The maximum tolerated doses of PSC 833 were 12.5 mg/kg orally every 12 hours for 8 days for the liquid formulation in combination with 0.9 mg/m(2) per day vinblastine as a continuous intravenous infusion (CIV) for 5 days; and 4 mg/kg orally every 6 hours for 8 days for the microemulsion formulation in combination with 0.6 mg/m(2) per day vinblastine CIV for 5 days. The principal toxicities for PSC 833 were ataxia and paresthesias and for the combination, constipation, fever. and neutropenia. Increased oral bioavailability and increased peak and trough concentrations were observed with the microemulsion formulation. Significant interpatient variability in pharmacokinetic parameters was observed. Ten patients studied at the MTD for PSC 833 (4 mg/kg orally every 6 hours for 8 days) had inhibition of rhodamine efflux from CD56 positive peripheral lymphocytes as a surrogate for Pgp antagonism. Among 43 evaluable patients with clear cell carcinoma of the kidney, 3 patients had complete responses, and 1 patient had a partial response. CONCLUSIONS: PSC 833 in combination with vinblastine can be administered safely to patients provided the vinblastine dose is adjusted for pharmacokinetic interactions. The high interpatient variability is a significant confounding factor. Surrogate studies with CD56 positive cells suggest that Pgp inhibition in the clinical setting is achievable. Improved methods for predicting pharmacokinetic interactions should improve future studies.

Approaches to preclinical screening of antiangiogenic agents.

Angiogenesis, or new blood vessel growth, is essential for the growth, invasion, and metastasis of solid tumors. The inhibition of this process, or antiangiogenesis, is a promising new therapeutic anticancer strategy. Several antiangiogenic compounds are currently in preclinical or clinical development for the treatment of cancer. However, the challenge for the discovery and characterization of antiangiogenic targets remains in developing efficient in vitro or in vivo preclinical angiogenesis screening assays to assess and compare antiangiogenic activity. Several semiquantitative or quantitative angiogenesis assays exist, including in vitro endothelial cell systems and ex vivo or in vivo neovascularization models utilizing mouse, rat, or human tissues. We describe the more common and cost-effective angiogenesis assays currently in use, summarizing their unique advantages and disadvantages. Since angiogenesis inhibition is a novel therapeutic modality towards controlling solid tumors, antiangiogenic drug development underlines the importance in describing, standardizing, and developing quantitative screening assays for the next generation of antiangiogenic agents.