Tumor Tissue Penetration Research Articles

First-in-human phase I trial of a novel epothilone, KOS-1584

2003 Background: KOS-1584 (9,10-didehydroepothilone D) was discovered as part of a screening program to develop a new generation of epothilones with higher potency and an improved pharmacologic/pharmacokinetic (PK) profile. Epothilones stabilize microtubule polymerization, inducing rapid G2/M arrest and apoptosis. Antitumor activity of KOS-1584 (Chou et al 2003) is approximately 3–12 fold more potent when compared to the structurally related Epothilone D. KOS-1584 demonstrates enhanced tumor tissue penetration and reduced exposure to selected tissues (including CNS). We report the results of the initial dose-escalation trial in which KOS-1584 was administered to pts with advanced solid malignancies. Methods: Define the MTD, toxicity profile and PK of KOS-1584 when administered via 3-hour infusion every 3 weeks. PK was determined after the 1st and 2nd infusion. Pharmacodynamics were assessed by serial sampling of PBMCs for microtubule bundle formation. Results: 27 pts (17 F; median age 60; median ECOG PS 1; median prior regimens 3, range 0–7) enrolled in 8 dose levels (between 0.8 - 11.3 mg/m2). To date, no Cycle 1 DLT has been seen. Toxicities (n=24) did not show obvious dose dependency; common toxicity (Grade 1–2) included gastrointestinal (diarrhea, constipation, nausea), fatigue, and ↑AST. Drug-related Grade 3 toxicity: constipation, fatigue and ↑AST (1 each). Drug-related neurotoxicity was not notable. PK/parent (n=25): t½ 17.7 ± 4.6h, Vz 741±330 L and CL 30.2± 16.5 L/h. At 8.5 mg/m2 Cmax 78 ± 29 ng/mL; AUCtot 631 ± 337 ng*h/mL. Cmax and AUCtot increased linearly with dose over the range tested. Vz is ∼5-fold and t½ 2-fold higher than that of Epothilone D. Dose dependent increases in microtubule bundle formation were observed (8.5 mg/m2: 40–50% at end of infusion, compared to 60–65% for ixabepilone and 50–60% for Epothilone D using the same assay at their phase 2 dose). A sigmoidal Emax model described the relationship between plasma concentration and microtubule bundle formation. Activity consisted of 4 pts with extended stable disease (6 cycles leiomyosarcoma and ovarian cancer; 5 cycles colon cancer; a 2nd patient with ovarian cancer is active at 5 cycles). Of these, 3 had document progressive disease prior to study. Conclusions: Accrual is continuing in order to define the optimal dose on the 3-week regimen. [Table: see text]

Salmonella typhimurium specifically chemotax and proliferate in heterogeneous tumor tissue in vitro

Multi-drug resistance greatly limits the efficacy of conventional blood-born chemotherapeutics, which have limited ability to penetrate tumor tissue and are ineffective at killing quiescent cells far from tumor vasculature. Nonpathogenic, motile bacteria can overcome both of theses limitations. We hypothesize that the accumulation of S. typhimurium in tumors is controlled by two mechanisms: (1) chemotaxis towards compounds produced by quiescent cancer cells and (2) preferential growth within tumor tissue. We tested this hypothesis by quantifying the relative contributions of these mechanisms using the tumor cylindroid model, which mimics the microenvironments of in vivo tumors. Time-lapse fluorescence microscopy was used to measure the accumulation of GFP-labeled S. typhimurium into cylindroids of different size. Cylindroids larger than 500 microm in diameter contain quiescent cells, whereas cylindroids smaller than 500 microm do not. Spatio-temporal profiles of bacterial concentration were fit to a mathematical model to calculate two parameters that describe bacterial interaction with tumors: intratumoral bacterial growth, M, and intratumoral bacterial chemoattraction, K. It was observed that S. typhimurium is attracted to cylindroids and accumulate at long time points in the central region of large cylindroids. Both intratumoral bacterial growth and chemotaxis were significantly greater in large cylindroids, suggesting that quiescent cells secrete bacterial chemoattractants and the presence of necrotic and quiescent cells enable S. typhimurium to replicate in tumor tissue. In this study, several mechanisms of S. typhimurium accumulation in solid tumors have been quantified, which we believe is an important step in the development of bacterial-based therapeutics to target tumor quiescence.

Monoclonal antibody therapy for genitourinary oncology: promise for the future.

Metastatic or recurrent cancer continues to be the bane of the urological oncologist. Despite recent improvements in therapeutic strategies and outcomes for clinically localized disease overall survival in patients with the majority of metastatic and recurrent genitourinary malignancies remains relatively unchanged. Modern advances in the field of immunotherapy hold the promise of providing the clinical urologist/oncologist with new tools to fight urological cancer. In this review we discuss the various mAb based strategies currently under investigation for urological oncology as well as the lessons learned from similar approaches in other fields. We reviewed the literature on mAb based immunotherapy with a particular emphasis on target antigens, mAb design and potential applications in the field of urology. Early trials with mAb therapy for solid tumor oncology met with limited success due to difficulty with mAb design and production, the development of host immunological responses against murine monoclonal antibodies (that is human anti-mouse antibodies), suboptimal target antigen selection, and poor monoclonal antibody pharmacokinetics and tumor tissue penetration. Recent advances in the fields of immunology and oncology have sought to circumvent these obstacles. Today several preliminary studies have shown the effectiveness and usefulness of mAb based strategies for urological oncology. The field of mAb based immunotherapy continues to evolve. New discoveries in this burgeoning area of cancer therapy show promise for the future.

Identification of peptides that bind to irradiated pancreatic tumor cells

Peptides targeting tumor vascular cells or tumor cells themselves have the potential to be used as vectors for delivering either DNA in gene therapy or antitumor agents in chemotherapy. We wished to determine if peptides identified by phage display could be used to target irradiated pancreatic cancer cells. Irradiated Capan-2 cells were incubated with 5 x 10(12) plaque-forming units of a phage display library. Internalized phage were recovered and absorbed against unirradiated cells. After five such cycles of enrichment, the recovered phage were subjected to DNA sequencing analysis and synthetic peptides made. The binding of both phage and synthetic peptides was evaluated by fluorescence staining and flow cytometry in vitro and in vivo. We identified one 12-mer peptide (PA1) that binds to irradiated Capan-2 pancreatic adenocarcinoma cells but not to unirradiated cells. The binding of peptide was significant after 48 h incubation with cells. In vivo experiments with Capan-2 xenografts in nude mice demonstrated that these small peptides are able to penetrate tumor tissue after intravenous injections and bind specifically to irradiated tumor cells. These data suggest that peptides can be identified that target tumors with radiation-induced cell markers and may be clinically useful.

Direct assessment of drug penetration into tissue using a novel application of three-dimensional cell culture.

The failure of many anticancer drugs to control growth of solid cancers may stem in part from inadequate delivery to tumor regions distant from vasculature. Although the identification of new anticancer drug targets has led to the development of many new drug candidates, there is a lack of methodology for identifying drugs that adequately penetrate tumor tissue. We have developed a novel multilayered cell culture-based assay, which detects the penetration of anticancer drugs based on their effect within tissue. Drug exposures are made over 1 hour to one side of a disk of tissue approximately 150-microm thick, with the other side temporarily closed off, and penetration is then assessed 1-3 days later via bromodeoxyuridine-based detection of S-phase cells. Using this assay, the tissue distribution of a selection of anthracycline analogues was assessed. At clinically relevant exposures, none of the agents were able to affect cells on the far side of the culture at levels approaching that seen on the near (exposed) side. Doxorubicin and epirubicin exhibited approximately 10-fold decreases in the drug exposure seen by the cells on the far side relative to those on the near side of the cultures, whereas for daunorubicin and mitoxantrone, approximately 30-fold and >30-fold decreases were observed respectively. Results were consistent with the observed gradients in drug-derived fluorescence of doxorubicin, epirubicin, and daunorubicin. This model could be applied as a simple anticancer drug development screen to discover drugs that exhibit desirable penetration properties.