Pre-clinical dose-ranging efficacy, pharmacokinetics, tissue biodistribution, and toxicity of a targeted contrast agent for MRI of amyloid deposition in Alzheimer's disease.

In these preclinical studies, we describe ADx-001, an Aß-targeted liposomal macrocyclic gadolinium (Gd) imaging agent, for MRI of amyloid plaques. The targeting moiety is a novel lipid-PEG conjugated styryl-pyrimidine. An MRI-based contrast agent such as ADx-001 is attractive because of the lack of radioactivity, ease of distribution, long shelf life, and the prevalence of MRI scanners. Dose-ranging efficacy studies were performed on a 1 T MRI scanner using a transgenic APP/PSEN1 mouse model of Alzheimer's disease. ADx-001 was tested at 0.10, 0.15, and 0.20 mmol Gd/kg. Gold standard post-mortem amyloid immunostaining was used for the determination of sensitivity and specificity. ADx-001 toxicity was evaluated in rats and monkeys at doses up to 0.30 mmol Gd/kg. ADx-001 pharmacokinetics were determined in monkeys and its tissue distribution was evaluated in rats. ADx-001-enhanced MRI demonstrated significantly higher (p < 0.05) brain signal enhancement in transgenic mice relative to wild type mice at all dose levels. ADx-001 demonstrated high sensitivity at 0.20 and 0.15 mmol Gd/kg and excellent specificity at all dose levels for in vivo imaging of ß amyloid plaques. ADx-001 was well tolerated in rats and monkeys and exhibited the slow clearance from circulation and tissue biodistribution typical of PEGylated nanoparticles.

Meeting product development challenges in manufacturing clinical grade oncolytic adenoviruses.

Oncolytic adenoviruses have been considered for use as anticancer therapy for decades, and numerous means of conferring tumor selectivity have been developed. As with any new therapy, the trip from the laboratory bench to the clinic has revealed a number of significant development hurdles. Viral therapies are subject to specific regulations and must meet a variety of well-defined criteria for purity, potency, stability, and product characterization prior to their use in the clinic. Published regulatory guidelines, although developed specifically for biotechnology-derived products, are applicable to the production of oncolytic adenoviruses and other cell-based products, and they should be consulted early during development. Most importantly, both the manufacturing process and the development of characterization and release assays should be science-driven, use the best available science and technology, and must consider the unique nature of the product: a living, and mutatable, virus. Potentially significant impacts on product quality and safety stem from the possibility of genetic instability related to over-engineering the viruses (as evidenced by their recombination and/or occasional reversion to wild-type virus during manufacturing). This report provides examples of some of the critical components affecting the development and production of clinical grade material and summarizes the significant progress made in recent years.

Systemic and tumor disposition of platinum after administration of cisplatin or STEALTH liposomal-cisplatin formulations (SPI-077 and SPI-077 B103) in a preclinical tumor model of melanoma.

PURPOSE: SPI-077 and SPI-077 B103 are formulations of cisplatin encapsulated in pegylated STEALTH liposomes that accumulate in tumors. However, the extent to which active platinum (Pt) is released from the liposome is unknown. Thus, we evaluated the disposition of encapsulated and released Pt in plasma and tumors after administration of STEALTH liposomal and nonliposomal cisplatin. METHODS: Cisplatin (10 mg/kg), SPI-077 (10 mg/kg), and SPI-077 B103 (5 mg/kg) were administered i.v. to mice bearing B16 murine melanoma tumors. Microdialysis probes were placed into the right and left sides of each tumor, and serial samples were collected from tumor extracellular fluid (ECF) after administration of each agent. After each microdialysis procedure, tumor samples were obtained at each probe site to measure total Pt and Pt-DNA adducts. In a separate study, serial plasma samples (three mice per time point) were obtained. Unbound Pt in tumor ECF and plasma, and total Pt in tumor homogenates were measured by flameless atomic absorption spectrophotometry. Area under the tumor ECF (AUC(ECF)) concentration versus time curves of unbound Pt were calculated. Intrastrand GG (Pt-GG) and AG (Pt-AG) Pt-DNA adducts were measured via (32)P-postlabeling. RESULTS: Mean+/-SD peak concentrations of total Pt in tumor homogenates after administration of cisplatin, SPI-077, and SPI-077 B-103 were 3.2+/-1.9, 11.9+/-3.0, and 3.5+/-0.3 microg/g, respectively. After cisplatin, mean+/-SD AUC(ECF) of unbound Pt was 0.72+/-0.46 microg/ml.h. There was no detectable unbound Pt in tumor ECF after SPI-077 or SPI-077 B-103 treatment. Mean+/-SD peak concentration of Pt-GG DNA adducts after administration of cisplatin, SPI-077, and SPI-077 B-103 were 13.1+/-3.3, 3.5+/-1.3, and 2.1+/-0.3 fmol Pt/microg DNA, respectively. CONCLUSION: This study suggests that more SPI-077 and SPI-077 B103 distribute into tumors, but release less Pt into tumor ECF, and form fewer Pt-DNA adducts than does cisplatin.

Pegylated liposomal doxorubicin: proof of principle using preclinical animal models and pharmacokinetic studies.

Encapsulation of doxorubicin in polyethylene glycol-coated liposomes (Doxil/Caelyx [PLD]), was developed to enhance the safety and efficacy of conventional doxorubicin. The liposomes alter pharmacologic and pharmacokinetic parameters of conventional doxorubicin so that drug delivery to the tumor is enhanced while toxicity normally associated with conventional doxorubicin is decreased. In animals and humans, pharmacokinetic advantages of PLD include an increased area under the plasma concentration-time curve, longer distribution half-life, smaller volume of distribution, and reduced clearance. In preclinical models, PLD produced remission and cure against many cancers including tumors of the breast, lung, ovaries, prostate, colon, bladder, and pancreas, as well as lymphoma, sarcoma, and myeloma. It was also found to be effective as adjuvant therapy. In addition, it was found to cross the blood-brain barrier and induce remission in tumors of the central nervous system. Increased potency over conventional doxorubicin was observed and, in contrast to conventional doxorubicin, PLD was equally effective against low- and high-growth fraction tumors. The combination of PLD with vincristine or trastuzumab resulted in additive effects and possible synergy. PLD appeared to overcome multidrug resistance, possibly as the result of increased intracellular concentrations and an interaction between the liposome and P-glycoprotein function. On the basis of pharmacokinetic and preclinical studies, PLD, either alone or as part of combination therapy, has potential applications to treat a variety of cancers.

STEALTH liposome-encapsulated cisplatin (SPI-77) versus carboplatin as adjuvant therapy for spontaneously arising osteosarcoma (OSA) in the dog: a randomized multicenter clinical trial.

PURPOSE: This trial was designed to compare the efficacy of adjuvant STEALH liposome-encapsulated cisplatin (SPI-77) to "standard-of-care" carboplatin therapy in dogs with osteosarcoma (OSA) in the context of a randomized study design. METHODS: The study included 40 pet dogs with spontaneously arising OSA which were randomized to receive SPI-77 (350 mg/m(2) i.v. every 3 weeks for four treatments) or carboplatin (300 mg/m(2) i.v. every 3 weeks for four treatments) along with amputation of the affected limb. Median disease-free (DFS) and overall survival (OS) were compared using standard life-table analysis. RESULTS: The median follow-up was 693 days (range 321-730 days). Of 38 dogs eligible for follow-up, 25 were dead of their disease, 9 were alive and disease-free (8 receiving SPI-77, 1 receiving carboplatin; P=0.02), 2 were free of disease when they were lost to follow-up at 321 and 395 days, and 2 had died of an unrelated disease. The median DFS times for dogs treated with SPI-77 and carboplatin were 156 and 123 days, respectively ( P=0.19). The median OS times for dogs treated with SPI-77 and carboplatin were 333 and 207 days, respectively ( P=0.18). CONCLUSIONS: While STEALTH liposome encapsulation of cisplatin allowed the safe administration of five times the maximally tolerated dose of free cisplatin to dogs without concurrent hydration protocols, this did not translate into significantly prolonged DFS or OS. However, a larger proportion of dogs receiving SPI-77 enjoyed long-term DFS when compared with dogs receiving carboplatin.