Chronic hepatitis B virus (HBV) infection is a major health concern worldwide, frequently leading to liver cirrhosis, liver failure and hepatocellular carcinoma. Evidence exists that high viral antigen load may play a role in chronicity. Production of viral proteins is thought to depend on transcription of viral covalently closed circular DNA (cccDNA). In a human clinical trial with ARC-520, a RNA interference (RNAi)-based therapeutic targeting HBV transcripts, HBV S antigen (HBsAg) was strongly reduced in treatment-naïve patients positive for HBV e antigen (HBeAg) but was reduced significantly less in patients that were HBeAg negative or had received long-term therapy with nucleos(t)ide viral replication inhibitors (NUCs). The molecular basis for this unexpected differential response was investigated in chimpanzees chronically infected with HBV. Several independent lines of evidence demonstrated that HBsAg was expressed not only from the episomal cccDNA minichromosome, but also from transcripts arising from HBV DNA integrated into the host genome. The latter was the dominant source in HBeAg negative chimpanzees. Many of the integrants detected in chimpanzees lacked target sites for the siRNAs in ARC-520, explaining the reduced response in HBeAg negative chimpanzees and by extension in HBeAg negative patients. Our results uncover a heretofore under-recognized source of HBsAg that may represent a strategy adopted by HBV to maintain chronicity in the presence of host immune surveillance and could alter trial design and endpoint expectations of new therapies for chronic HBV.

Linear and branched poly(ethylenimines), lPEI and bPEI, respectively, grafted with beta-cyclodextrin are prepared to give CD-lPEI and CD-bPEI, respectively, and are investigated as in vitro and in vivo nonviral gene delivery agents. The in vitro toxicity and transfection efficiency are sensitive to the level of cyclodextrin grafting. The cyclodextrin-containing polycations, when combined with adamantane-poly(ethylene glycol) (AD-PEG) conjugates, form particles that are stable at physiological salt concentrations. PEGylated CD-lPEI-based particles give in vitro gene expression equal to or greater than lPEI as measured by the percentage of EGFP expressing cells. Tail vein injections into mice of 120 microg of plasmid DNA formulated with CD-lPEI and AD-PEG do not reveal observable toxicities, and both nucleic acid accumulation and expression are observed in liver.

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IT-101, a cyclodextrin polymer-based nanoparticle containing camptothecin, is in clinical development for the treatment of cancer. Multiorgan pharmacokinetics and accumulation in tumor tissue of IT-101 is investigated by using PET. IT-101 is modified through the attachment of a 1,4,7,10-tetraazacyclododecane-1,4,7-Tris-acetic acid ligand to bind 64 Cu 2؉ . This modification does not affect the particle size and minimally affects the surface charge of the resulting nanoparticles. PET data from 64 Cu-labeled IT-101 are used to quantify the in vivo biodistribution in mice bearing Neuro2A s.c. tumors. The 64 Cu-labeled IT-101 displays a biphasic plasma elimination. Approximately 8% of the injected dose is rapidly cleared as a low-molecular-weight fraction through the kidneys. The remaining material circulates in plasma with a terminal half-life of 13.3 h. Steadily increasing concentrations, up to 11% injected dose per cm 3 , are observed in the tumor over 24 h, higher than any other tissue at that time. A 3-compartment model is used to determine vascular permeability and nanoparticle retention in tumors, and is able to accurately represent the experimental data. The calculated tumor vascular permeability indicates that the majority of nanoparticles stay intact in circulation and do not disassemble into individual polymer strands. A key assumption to modeling the tumor dynamics is that there is a ''sink'' for the nanoparticles within the tumor. Histological measurements using confocal microscopy show that IT-101 localizes within tumor cells and provides the sink in the tumor for the nanoparticles.cancer ͉ camptothecin ͉ cyclodextrin ͉ polymer ͉ intracellular delivery C hemotherapeutics are the mainstay of cancer treatment for advanced and/or metastatic tumors. However, their effectiveness is typically limited by toxicity in healthy, normal tissues with rapidly dividing cells, such as bone marrow or the gastrointestinal tract. One approach to increase the therapeutic index of chemotherapeutics is site-directed delivery by using various carrier systems. Numerous types of delivery technologies have been developed for this purpose, such as liposomes (1, 2), conjugates with antibodies or small molecules targeted to tumor antigens (3, 4), and macromolecular polymer carriers (5). Carrier-drug composites are nanoscaled therapeutics, and nanoparticle cancer therapeutics that have been used in humans have been reviewed elsewhere (6).The use of nanoscaled therapeutics takes advantage of the unique tumor physiology characterized by a high density of abnormal blood vessels, high vascular permeability, and decreased rate of clearance due to a lack of lymphatic drainage, all of which act together to cause accumulation of macromolecules through the enhanced permeability and retention (EPR) effect (7). The magnitude of this effect is affected by a number of parameters that are either host-related (tumor perfusion, vascularity, vascular permeability) or nanoparticle-related (plasma half-life, clearance, hydrodynamic size, surface char...

Preclinical efficacy of i.v. IT-101, a nanoparticulate conjugate of 20(S)-camptothecin and a cyclodextrin-based polymer, was investigated in several mouse xenografts.The effects of different multiple dosing schedules on tumor growth of LS174Tcolon carcinoma xenografts are elucidated. All multiple dosing schedules administered over15 to19 days resulted in enhanced efficacy compared with untreated or single-dose groups. Further improvements in antitumor efficacy were not observed when the dosing frequency was increased from three weekly doses to five doses at 4-day intervals or 5 days of daily dosing followed by 2 days without dosing repeated in three cycles using similar cumulative doses. This observation was attributed to the extended release characteristics of camptothecin from the polymer. Antitumor efficacy was further evaluated in mice bearing six different s.c. xenografts (LS174T and HT29 colorectal cancer, H1299 nonŝ mall-cell lung cancer, H69 small-cell lung cancer, Panc-1pancreatic cancer, and MDA-MB-231 breast cancer) and one disseminated xenograft (TC71-luc Ewing's sarcoma). In all cases, a single treatment cycle of three weekly doses of IT-101resulted in a significant antitumor effect. Complete tumor regression was observed in all animals bearing H1299 tumors and in the majority of animals with disseminated Ewing's sarcoma tumors. Importantly, IT-101is effective in a number of tumors that are resistant to treatment with irinotecan (MDA-MB-231, Panc-1, and HT29), consistent with the hypothesis that polymeric drug conjugates may be able to overcome certain kinds of multidrug resistance. Taken together, these results indicate that IT-101 has good tolerability and antitumor activity against a wide range of tumors.

The studies presented here indicate that intravenous administration of IT-101, a cyclodextrin based polymer-CPT conjugate, gives prolonged plasma half-life and enhanced distribution to tumor tissue when compared to CPT alone. The data also show that active CPT is released from the conjugate within the tumor for an extended period of time. These effects likely play a significant role in the enhanced antitumor activity of IT-101 when compared to CPT alone or irinotecan.

Summary Patients with advanced solid malignancies were enrolled to an open-label, single-arm, dose-escalation study, in which CRLX101 was administered intravenously over 60 min among two dosing schedules, initially weekly at 6, 12, and 18 mg/m2 and later bi-weekly at 12, 15, and 18 mg/m2. The maximum tolerated dose (MTD) was determined at 15 mg/m2 bi-weekly, and an expansion phase 2a study was completed. Patient samples were obtained for pharmacokinetic (PK) and pharmacodynamic (PD) assessments. Response was evaluated per RECIST criteria v1.0 every 8 weeks. Sixty-two patients (31 male; median age 63 years, range 39-79) received treatment. Bi-weekly dosing was generally well tolerated with myelosuppression being the dose-limiting toxicity. Among all phase 1/2a patients receiving the MTD (n=44), most common grade 3/4 adverse events were neutropenia and fatigue. Evidence of systemic plasma exposure to both the polymer-conjugated and unconjugated CPT was observed in all treated patients. Mean elimination unconjugated CPT Tmax values ranged from 17.7 to 24.5 h, and maximum plasma concentrations and areas under the curve were generally proportional to dose for both polymer-conjugated and unconjugated CPT. Best overall response was stable disease in 28 patients (64 %) treated at the MTD and 16 (73 %) of a subset of NSCLC patients. Median progression-free survival (PFS) for patients treated at the MTD was 3.7 months and for the subset of NSCLC patients was 4.4 months. These combined phase 1/2a data demonstrate encouraging safety, pharmacokinetic, and efficacy results. Multinational phase 2 clinical development of CRLX101 across multiple tumor types is ongoing.

Nanoparticles are currently being investigated in a number of human clinical trials. As information on how nanoparticles function in humans is difficult to obtain, animal studies that can be correlative to human behavior are needed to provide guidance for human clinical trials. Here, we report correlative studies on animals and humans for CRLX101, a 20-to 30-nm-diameter, multifunctional, polymeric nanoparticle containing camptothecin (CPT). CRLX101 is currently in phase 2 clinical trials, and human data from several of the clinical investigations are compared with results from multispecies animal studies. The pharmacokinetics of polymer-conjugated CPT (indicative of the CRLX101 nanoparticles) in mice, rats, dogs, and humans reveal that the area under the curve scales linearly with milligrams of CPT per square meter for all species. Plasma concentrations of unconjugated CPT released from CRLX101 in animals and humans are consistent with each other after accounting for differences in serum albumin binding of CPT. Urinary excretion of polymer-conjugated CPT occurs primarily within the initial 24 h after dosing in animals and humans. The urinary excretion dynamics of polymer-conjugated and unconjugated CPT appear similar between animals and humans. CRLX101 accumulates into solid tumors and releases CPT over a period of several days to give inhibition of its target in animal xenograft models of cancer and in the tumors of humans. Taken in total, the evidence provided from animal models on the CRLX101 mechanism of action suggests that the behavior of CRLX101 in animals is translatable to humans.nanomedicine | clinical translation | interspecies scaling | pharmacodynamics | Nanoparticles