Qualitative and quantitative measurements of oligonucleotides in gene therapy: Part II in vivo models.

Part I of this review has already been presented on methods of processing and purification of crude or raw samples in cell-culture or cell free systems. Part II of the review focuses on the in vivo models of determination of input oligonucleotides in both non-primates and primates. Emphasis has been given to the techniques developed for quantification of oligonucleotides or their metabolites from biological samples including blood, plasma, serum, urine and other tissues.

Qualitative and quantitative measurements of oligonucleotides in gene therapy: Part I. In vitro models.

Part I of this review attempts to bring together all the methods of detection and determination of synthetic oligonucleotides used in in vitro, described in the literature over the past 14 years, in an effort by scientists to use these oligonucleotides as drugs in gene therapy. The in vitro models include cell-free and cell culture systems. Emphasis has been given to the techniques developed for quantification of the input oligonucleotides or their metabolites. The purpose of study, methods of processing, detection and determination techniques such as those based on fluorescence, radiolabeling, high-performance liquid chromatography, gel-electrophoresis and others have been presented.

Continuous infusion of antisense phosphorothioate therapeutics.

Current therapy for acute myelogenous leukemia (AML) includes induction with Ara-C and an anthracycline, such as daunorubicin, idarubicin, or mitoxantrone. Unfortunately, most patients relapse from initial remission. Nearly one-fifth of early relapses experience treatment-related deaths. In addition, patients refractory to Ara-C die within months. Hence, new therapeutic agents must be identified capable of enhanced remission rates, diminished treatment-related mortality, or that can achieve remissions in refractory patients.

Pharmacology and toxicology of phosphorothioate oligonucleotides in the mouse, rat, monkey and man.

Phosphorothioate oligonucleotides (PS-ODN) designed to temporarily modulate selected gene expression have made the journey from bench top to beside in a remarkably short period of time. A PS-ODN with sequence complementary to the p53 mRNA was administered to mice (4 mg/kg subcutaneously), rats (3-300 mg/kg intravenously), monkeys (intravenous infusions for up to 15 days) and humans (up to 0.25 mg/kg/h intravenous infusions for 10 days). These studies demonstrate the PS-ODN provides feasible pharmacokinetic parameters and minimal toxicity.

Characterization of binding sites, extent of binding, and drug interactions of oligonucleotides with albumin.

Phosphorothioate oligonucleotides (S-ODNs) have the ability to modulate gene expression selectively and thus have potential therapeutic capabilities. This potential led us to investigate the protein binding characteristics of selected S-ODNs. We evaluated S-ODN interactions with bovine serum albumin (BSA) and human serum albumin (HSA) in vitro. The equilibrium dissociation constants Km for the binding of a 20 mer S-ODN with BSA and HSA range between 1.1-5.2 x 10(-5) and 2.4-3.1 x 10(-4) M, respectively. The Km for an unrelated 15 mer S-ODN binding with HSA ranges between 3.7 and 4.8 x 10(-5) M. Studies with a fluorescently labeled 27 mer S-ODN suggest cooperative binding (Hill slope = 1.67) and/or the presence of secondary binding sites on the S-ODN. HSA or BSA linked to Sepharose was incubated with a 15, 20, or 24 mer S-ODN followed by the addition of selected drugs known to be highly protein bound (nifedipine, warfarin, midazolam, probenecid, indomethacin, and mitoxantrone). Up to 30% of S-ODN was displaced by warfarin in competition binding assays. Conversely, HSA-bound warfarin was incubated with a variety of oligonucleotides, including RNA and genomic dsDNA. Maximum displacement of warfarin-bound HSA was observed following incubation with 5'-cholesterol-conjugated 20 mer S-ODN. In summary, S-ODNs are likely to interact and displace other therapeutic agents that bind to albumin, particularly those binding at site I.

Systemic administration of a phosphorothioate oligonucleotide with a sequence complementary to p53 for acute myelogenous leukemia and myelodysplastic syndrome: initial results of a phase I trial.

A synthetic phosphorothioate oligonucleotide was administered systemically to five patients with either relapsed or refractory acute myelogenous leukemia (AML), or myelodysplastic syndrome (MDS). Patients received a 10-day continuous intravenous infusion of this compound, which is complementary to p53 mRNA. No major toxicity attributable to a dose of 0.05 mg/kg/hr was observed. A range of approximately 9 to 18% of the administered dose was recovered in the urine as intact oligonucleotide. Evaluation of malignant cells recovered from bone marrow and peripheral blood at intervals before, during, and after treatment reveals no enhanced growth potential following oligonucleotide administration. Hence, a phosphorothioate oligonucleotide complementary to p53 mRNA can be administered at this dose level to humans without major toxicity. Higher doses need to be evaluated for toxicity and potential clinical efficacy.

Peptidolytic monoclonal antibody elicited by a neuropeptide.

We report evidence that a monoclonal antibody raised by immunization with a vasoactive intestinal peptide (VIP)-carrier protein conjugate selectively hydrolyzes VIP and a fluorescence quenched decapeptide (FQ14-22D), representing the region of VIP most susceptible to autoantibody-mediated cleavage (residues 14-22). A high affinity of the antibody for VIP and a lower affinity for FQ14-22D were revealed by kinetic studies and further substantiated by potent inhibition of FQ14-22D cleaving activity by full-length VIP. Sequencing of FQ14-22D hydrolysis products indicated selective cleavage at one peptide bond. These observations suggest that antibodies induced against naturally occurring polypeptide antigens can express peptidolytic activity targeted for specific sequences in the recognition epitope.

Identification of a high-affinity RNA-binding site for the human immunodeficiency virus type 1 Rev protein.

Expression of the structural proteins of human immunodeficiency virus type 1 requires the direct interaction of multiple copies of the viral Rev protein with its highly structured RNA target sequence, the Rev response element (RRE). Nucleotides critical for Rev monomer binding have been mapped by chemical interference to a single site flanking the base of an RNA helix (stem IIB) located within the 234-nucleotide RRE. Binding of additional Rev molecules to an RRE probe did not require any RNA primary sequence information detectable by modification interference beyond that required for binding of a single Rev protein molecule. A synthetic 29-nucleotide RNA molecule designed to incorporate nucleotides identified as critical for Rev binding retained the ability to bind Rev specifically and, therefore, represents a minimal Rev-binding site. We propose that Rev binding to the RRE initiates with the direct interaction of a Rev monomer with a high-affinity binding site located at the base of the IIB stem of the RRE. The subsequent formation of Rev multimers on the RRE appears, in contrast, primarily driven by specific protein-protein interactions.