No effect on QT intervals of mipomersen, a 2'-O-methoxyethyl modified antisense oligonucleotide targeting ApoB-100 mRNA, in a phase I dose escalation placebo-controlled study, and confirmed by a thorough QT (tQT) study, in healthy subjects

PURPOSE

The aim of this study to evaluate the effect of mipomersen on QT intervals in a phase I dose escalation, placebo-controlled study, and a thorough QT (tQT) study in healthy subjects.

METHODS

In the initial phase I study, 29 healthy subjects received either single or multiple (for 4 weeks) ascending doses of mipomersen (50-400 mg) administered subcutaneously (SC) or via a 2-h intravenous (IV) infusion, and 7 subjects received placebo. In the confirmative tQT study, 58 healthy subjects received placebo, 400 mg IV moxifloxacin, 200 mg SC, or 200 mg IV of mipomersen in a double-blind, 4-way crossover design with a minimum 5-day washout between treatments. ECG measurements were performed at baseline and selected time points (including Tmax). The correlation between QTcF intervals corrected for baseline and time-matched placebo when available with PK plasma exposure was evaluated by linear regression analysis.

RESULTS

In the phase I study, no positive correlation between the PK exposure and ∆QTcF or ∆∆QTcF was observed within the wide dose or exposure range tested. Similar results were observed in the tQT study, where the predicted ΔΔQTcF and its upper bound of the 90% CI at Cmax of therapeutic and supratherapeutic dose were approximately -1.7 and 2.9 ms, respectively.

CONCLUSIONS

Mipomersen showed no effect on QT intervals in both the phase I dose escalation study and the tQT study. These results support the proposal that QT assessment can be made in a phase I dose escalation study, and no tQT study may be necessary if the phase I dose escalation study showed a negative QT effect.

Comparison of the RNase H cleavage kinetics and blood serum stability of the north-conformationally constrained and 2'-alkoxy modified oligonucleotides

The RNase H cleavage potential of the RNA strand basepaired with the complementary antisense oligonucleotides (AONs) containing North-East conformationally constrained 1',2'-methylene-bridged (azetidine-T and oxetane-T) nucleosides, North-constrained 2',4'-ethylene-bridged (aza-ENA-T) nucleoside, and 2'-alkoxy modified nucleosides (2'-O-Me-T and 2'-O-MOE-T modifications) have been evaluated and compared under identical conditions. When compared to the native AON, the aza-ENA-T modified AON/RNA hybrid duplexes showed an increase of melting temperature (DeltaTm = 2.5-4 degrees C per modification), depending on the positions of the modified residues. The azetidine-T modified AONs showed a drop of 4-5.5 degrees C per modification with respect to the native AON/RNA hybrid, whereas the isosequential oxetane-T modified counterpart, showed a drop of approximately 5-6 degrees C per modification. The 2'-O-Me-T and 2'-O-MOE-T modifications, on the other hand, showed an increased of Tm by 0.5 C per modification in their AON/RNA hybrids. All of the partially modified AON/RNA hybrid duplexes were found to be good substrates for the RNase H mediated cleavage. The Km and Vmax values obtained from the RNA concentration-dependent kinetics of RNase H promoted cleavage reaction for all AON/RNA duplexes with identical modification site were compared with those of the reference native AON/RNA hybrid duplex. The catalytic activities (Kcat) of RNase H were found to be greater (approximately 1.4-2.6-fold) for all modified AON/RNA hybrids compared to those for the native AON/RNA duplex. However, the RNase H binding affinity (1/Km) showed a decrease (approximately 1.7-8.3-fold) for all modified AON/RNA hybrids. This resulted in less effective (approximately 1.1-3.2-fold) enzyme activity (Kcat/Km) for all modified AON/RNA duplexes with respect to the native counterpart. A stretch of five to seven nucleotides in the RNA strand (from the site of modifications in the complementary modified AON strand) was found to be resistant to RNase H digestion (giving a footprint) in the modified AON/RNA duplex. Thus, (i) the AON modification with azetidine-T created a resistant region of five to six nucleotides, (ii) modification with 2'-O-Me-T created a resistant stretch of six nucleotides, (iii) modification with aza-ENA-T created a resistant region of five to seven nucleotide residues, whereas (iv) modification with 2'-O-MOE-T created a resistant stretch of seven nucleotide residues. This shows the variable effect of the microstructure perturbation in the modified AON/RNA heteroduplex depending upon the chemical nature as well as the site of modifications in the AON strand. On the other hand, the enhanced blood serum as well as the 3'-exonuclease stability (using snake venom phosphodiesterase, SVPDE) showed the effect of the tight conformational constraint in the AON with aza-ENA-T modifications in that the 3'-exonuclease preferentially hydrolyzed the 3'-phosphodiester bond one nucleotide away (n + 1) from the modification site (n) compared to all other modified AONs, which were 3'-exonuclease cleaved at the 3'-phosphodiester of the modification site (n). The aza-ENA-T modification in the AONs made the 5'-residual oligonucleotides (including the n + 1 nucleotide) highly resistant in the blood serum (remaining after 48 h) compared to the native AON (fully degraded in 2 h). On the other hand, the 5'-residual oligonucleotides (including the n nucleotide) in azetidine-T, 2'-O-Me-T, and 2'-O-MOE-T modified AONs were more stable compared to that of the native counterpart but more easily degradable than that of aza-ENA-T containing AONs.

Bioavailability and therapeutic activity of alicaforsen (ISIS 2302) administered as a rectal retention enema to subjects with active ulcerative colitis

BACKGROUND

Alicaforsen is a phosphorothioate-modified antisense oligodeoxynucleotide designed to sequence-specifically reduce intercellular adhesion molecule 1 messenger RNA levels.

AIMS

To determine the systemic and local bioavailability of alicaforsen, and its activity when administered as a once daily enema in subjects with active ulcerative colitis. METHODS An open-label study was conducted to assess the relative absorption (local and systemic pharmacokinetics) and pharmacologic activity of alicaforsen enema in subjects with active ulcerative colitis. Fifteen subjects received nightly enemas of alicaforsen (240 mg) for a treatment period of 6 weeks. Alicaforsen concentrations in plasma and colonic tissue biopsies were determined. Disease activity index and multiple measurements including endoscopy were used to assess alicaforsen activity in these subjects.

RESULTS

Plasma concentrations of parent alicaforsen represented < 0.6% mean bioavailability when compared with historical intravenous area under the plasma concentration-time curves. Concentrations of the intact oligonucleotide in mucosal colonic tissue biopsies were orders of magnitude higher than those observed in plasma. A 46% reduction in mean Disease Activity Index and 33% rate of remission as defined by complete mucosal healing were observed at the end of treatment. Conclusion These data confirm that alicaforsen enema provides local treatment for a local disease with little meaningful systemic exposure.

Quantification of raf antisense oligonucleotide (rafAON) in biological matrices by LC-MS/MS to support pharmacokinetics of a liposome-entrapped rafAON formulation

An LC-MS/MS method was developed to quantify an antisense oligonucleotide against Raf-1 expression (rafAON) in monkey and mouse plasma and in mouse tissue homogenates from animals dosed with a liposome-entrapped rafAON easy-to-use formulation (LErafAON-ETU) intended for use as an antineoplastic agent. RafAON was extracted from mouse and monkey plasma using solid-phase extraction. Tissues were homogenized and sample cleanup was achieved by protein precipitation. RafAON and the internal standard (IS) were separated on a Hamilton PRP-1 column and quantified by tandem mass spectrometry using an electrospray source in negative ion mode. The total run time was 4.0 min. The peak areas of two rafAON transitions were summed and plotted against the peak area of an IS transition to generate the standard curve. In monkey plasma the linear range was 50-10,000 ng/mL, and in mouse plasma it was 25-5000 ng/mL. The lower limit of quantification was 500 ng/mL (10 microg/g tissue) in heart, kidney, liver, lung and spleen homogenates, and the standard curve was linear up to 10,000 ng/mL. Accuracy, precision and stability were evaluated and found to be acceptable in all three matrices. The assay was used to support pharmacokinetics and tissue distribution studies of LErafAON-ETU in mice and monkeys.

Distribution and excretion of a phosphorothioate oligonucleotide in rats with experimentally induced renal injury

The effects of renal injury on the urinary excretion and tissue distribution of a 20-mer phosphorothioate oligonucleotide were investigated in male Sprague-Dawley rats. Renal injury was produced by treating the rats with either 5.0 mg/kg cisplatin or 2.5 mg/kg of a monoclonal antibody (mAb) directed toward Thy1.1. Controls received saline. Three days after cisplatin treatment or 2 days after anti- Thy1.1 treatment, the rats received 10 mg/kg ISIS 3521. Blood was collected at various times to assess the plasma concentrations of ISIS 3521, and rats were killed at various times from 6 to 48 hours after intravenous (i.v.) infusion of oligonucleotide to assess tissue concentrations by capillary gel electrophoresis (CGE). Cisplatin and anti-Thy1.1 antibody produced histologic and biochemical changes consistent with proximal tubular damage and glomerular damage, respectively. Urinary excretion of oligonucleotides was increased 2- to 4-fold of control; however, this amount accounted for only 1% to 2% of dose compared to 0.5% in controls. Proximal tubular damage reduced renal accumulations of ISIS 3521 and other oligonucleotide metabolites, but there were no obvious compensatory increases in concentrations in other organs except for a slight increase in spleen levels of total oligonucleotide. Glomerular damage was not associated with any change in oligonucleotide disposition. Immunohistochemical studies showed no evidence of alterations in the pattern of distribution within the injured kidney. The data suggest that acute renal dysfunction, either renal tubular or glomerular, does not markedly alter the urinary elimination and tissue deposition of a phosphorothioate oligonucleotide.

Potential of atelocollagen-mediated systemic antisense therapeutics for inflammatory disease

To study the possibility of using atelocollagen as an oligonucleotide (ODN) delivery carrier in vivo, the activity of formulated antisense ODN targeted against the intercellular adhesion molecule-1 (ICAM-1) mRNA was investigated in an allergic dermatitis model in mice. The allergic dermatitis was elicited in one ear of animals sensitized by treatment with 2,4-dinitrofluorobenzene. Antisense ODN was given to the animals as a single intravenous injection of formulation containing atelocollagen. Antisense activity was determined by measurement of ear thickness, histopathology, and immunohistochemistry 24 hr after the initiation of the dermatitis. Antisense activity was found to increase according to the concentration of atelocollagen in the formulation. The effect mediated by the ODN formulated with 0.05% atelocollagen was more than 50 times greater than that provided by ODN infusion, although the levels of ODN formulated with atelocollagen dropped below that of the 24-hr infusion group within 30 min. The formulated ODN could suppress inflammatory progression by treatment at 8 hr after the ear challenge when inflammation had already commenced at the challenged site. Moreover, antisense activity was noted even when the formulated ODN was injected 3 days before the initiation of inflammation. These data demonstrate that atelocollagen can enhance antisense activity remarkably and that the sustainable antisense activity mediated by the formulation of ODN with atelocollagen could completely change the strategy of antisense therapeutics.

Complement activation is responsible for acute toxicities in rhesus monkeys treated with a phosphorothioate oligodeoxynucleotide

The objective of this study was to define the role of complement activation in the acute and transient toxicities associated with administration of phosphorothioate oligonucleotides in monkeys. In the absence of complement inhibitor, complement activation blocker-2 (CAB-2), i.v. infusion of 20 mg/kg ISIS 2302 produced increases in the concentrations of the complement split products Bb and C5a (100- and 7-fold, respectively). Monkeys also experienced marked changes in bloodpressure (hypertension and hypotension), clinical signs of toxicity (lethargy and periorbital edema), fluctuations in circulating neutrophil counts, and elevations in serum cytokine levels (45-, 12-, and 4-fold increases in IL-6, MCP-1, and IL-12, respectively). Changes occurred at or near the end of infusion and returned to normal over time. One of the three animals died approximately 4 h following infusion of 20 mg/kg ISIS 2302 alone. In contrast, prior treatment with CAB-2 effectively blocked complement activation, as well as the ISIS 2302-induced hemodynamic and clinical responses. Importantly, plasma concentration of ISIS 2302 were unaffected by CAB-2 pretreatment. Thus, the protection afforded by CAB-2 was due to its inhibition of complement activation rather than to any impact on the disposition of ISIS 2302. These results clearly demonstrate the causal relationship between activation of the alternative complement pathway and the hemodynamic and clinical responses associated with rapid infusion of phosphorothioate oligonucleotides. Demonstration of this relationship underscores the importance of avoiding complement activation in patients to ensure the continued safe use of phosphorothioate oligodeoxynucleotides.

Dose ranging pharmacokinetic trial of high-dose alicaforsen (intercellular adhesion molecule-1 antisense oligodeoxynucleotide) (ISIS 2302) in active Crohn's disease

BACKGROUND AND AIMS

To evaluate the safety, pharmacokinetics and clinical efficacy of the intercellular adhesion molecule-1 antisense phosphorothioate oligonucleotide alicaforsen (ISIS 2302) at 250-350 mg in Crohn's disease.

METHODS

: Patients (> 50 kg) with active Crohn's disease (Crohn's disease activity index > or = 220) were assigned by gender, randomly, to two alicaforsen treatment groups: 300 or 350 mg, infused intravenously three times a week for 4 weeks. All patients weighing 36-50 kg received 250 mg of alicaforsen. Background aminosalicylates, antibiotics, immunosuppressives and corticosteroids were permitted, but tumour necrosis factor-alphainhibitors were prohibited. The primary end-point was clinical remission (Crohn's disease activity index < or = 150).

RESULTS

Twenty-two patients were enrolled with a mean baseline Crohn's disease activity index of 304. Steroids were used by 27%, 5-aminosalicylic acid by 68% and immunosuppressives by 27%; 23% had previously received infliximab. Five subjects withdrew after one to three infusions for infusion-related symptoms. Nine patients (41%) experienced clinical remission. Fifty-three per cent of the evaluable subjects receiving more than three infusions experienced remission (18% at week 8; 29% at week 12). The overall response, using a minimum decrease of 70 in the Crohn's disease activity index, was 41-47% for the evaluable group, at weeks 8 and 12. The median duration of remission was 14 weeks. Plasma pharmacokinetic results showed overlapping levels (Cmax, AUC) for the three doses. The infusion-related reaction profile consisted of fever, chills, headache, nausea, emesis or arthralgias, typically occurring 2-4 h after completion of the first infusion. Reactions were less frequent in patients receiving background corticosteroids. The 2-4-h transient post-infusion partial thromboplastin time prolongation values, a class effect of phosphorothioate oligonucleotides, were 18, 21 and 23 s for 250, 300 and 350 mg, respectively.

CONCLUSIONS

Alicaforsen (ISIS 2302), at fixed doses of 300 and 350 mg, achieved the desired drug exposure and may be an effective therapy for Crohn's disease. Infusion-related reactions were observed less frequently in patients on corticosteroids, and with decreasing frequency with continued treatment.

bis-Cholesteryl-conjugated phosphorothioate oligodeoxynucleotides are highly selectively taken up by the liver

We previously modulated, by conjugating a single cholesterol, plasma protein binding and liver cell uptake of a phosphorothioate oligodeoxynucleotide (PS-ODN). In this study, we investigated the biological fate of a PS-ODN, denoted ISIS-9389 (3',5'-bis-cholesteryl-conjugated ISIS 3082), provided with two cholesteryl moieties. After intravenous injection of into rats, [(3)H]ISIS-9389 was cleared from plasma with a half-life of 23.6 +/- 0.3 min. After 90 min (approximately 95% cleared), the liver contained 83.0 +/- 0.8% of the dose. Spleen and bone (marrow), which constitute with the liver the reticuloendothelial system, contained 3.1 +/- 0.3 and 4.3 +/- 0.2%, respectively. All other tissues accumulated together <5% of the dose. The hepatic uptake of [(3)H]ISIS-9389 occurred mainly by endothelial cells (51.9 +/- 6.4% of the liver uptake). Parenchymal and Kupffer cells were responsible for 24.9 +/- 7.7 and 23.3 +/- 2.5%, respectively. Preinjected polyinosinic acid and polyadenylic acid reduced hepatic uptake, albeit the latter was less effective. This finding suggests implication of (multiple) scavenger receptors in liver uptake of ISIS-9389. The interaction of ISIS-9389 with plasma proteins, analyzed by size exclusion chromatography, differs from that of unconjugated PS-ODN and PS-ODN with a single cholesterol. Plasma-incubated ISIS-9389 was mainly recovered as a high molecular weight complex. In conclusion, conjugation of PS-ODNs with two cholesteryl moieties results in almost quantitative uptake by the liver. The liver targeting exceeds the already impressive gain in liver uptake achieved by conjugation of a single cholesterol, and is expected to increase the therapeutic activity against liver-associated targets and reduce side effects in nonhepatic tissues.

Development of an ultrasensitive noncompetitive hybridization-ligation enzyme-linked immunosorbent assay for the determination of phosphorothioate oligodeoxynucleotide in plasma

An ultrasensitive noncompetitive hybridization-ligation heterogeneous enzyme-linked immunosorbent assay was developed for the quantitation of antisense phosphorothioate oligodeoxynucleotides in plasma using a 96-well plate format. The principle of the assay is based on heterogeneous noncompetitive binding of the analyte to a template probe, followed by addition of signal probe via ligation and detection using a fluorescence microtiter plate reader. The result showed no significant interference noted from untreated human plasma. In addition, the method is selective for the specific sequence tested (ISIS 2302) and cross-reactivity toward the 3'-metabolites is minimal (< 0.22%). A linear range of 0.05 to 2 nM (r > 0.99) was obtained in human plasma for ISIS 2302. Intraday and interday accuracy for the method was found to be within 80-120% of actual value. Intraday and interday precision has a percentage coefficient of variation less than 20%. The lower limit of quantitation of the method was 0.05 nM (0.05 pmol/ml) with 100 microL plasma or an absolute amount of 5 fmol. In summary, the assay was demonstrated to be specific, accurate, precise, and sensitive for the quantitation of ISIS 2302 in human plasma and was applied to the analysis of plasma samples in pharmacokinetic studies.

EWS fli-1 antisense nanocapsules inhibits ewing sarcoma-related tumor in mice

EWS Fli-1, a fusion gene resulting from a t(11;22) translocation is found in 90% of both Ewing's sarcoma and primitive neuroectodermal tumor (PNET). In the present study, we show that recently developed polyisobutylcyanoacrylate nanocapsules with an aqueous core were able to encapsulate efficiently high amounts of phosphorothioate oligonucleotides (ODN) directed against EWS Fli-1 chimeric RNA. Release of these ODN in serum medium was shown to be biphasic which was explained by the presence of two types of nanocapsules able to release ODN with different kinetics. In addition, nanocapsules were found to provide protection of these oligonucleotides from the degradation in serum. These ODN nanocapsules permitted to obtain inhibition of Ewing sarcoma-related tumor in mice after intratumoral injection of a cumulative dose as low as 14.4 nanomoles. This new type of non viral vector shows great potential for in vivo administration of oligonucleotides.

Comparison of the pharmacokinetics of subcutaneous and intravenous administration of a phosphorothioate oligodeoxynucleotide in cynomolgus monkeys

The pharmacokinetics of subcutaneous (s.c.) administration of a phosphorothioate oligodeoxynucleotide (PS-ODN) was evaluated in cynomolgus monkeys. In a single dose study, monkeys were injected s.c. or intravenously (i.v.) with doses of either 1 or 5 mg/kg ISIS 2302. The bioavailability of s.c. injection ranged from 26% to 55% and appeared to be dependent on the concentration of the dosing solution rather than the dose. The bioavailability of a subcutaneously administered 5 mg/kg dose of ISIS 2302 was 55% using a 50 mg/ml dosing solution and only 26% using a 10 mg/ml dosing solution. Slow absorption from the s.c. injection site significantly blunted the maximal concentration (Cmax) compared with i.v. administration. The time to peak plasma concentration (Tmax) increased slightly with increasing dose, from 0.5 to 1 hour for the 1 mg/kg dose to 1 to 2.5 hours for the 5 mg/kg dose. Plasma half-lives were prolonged after s.c. administration, indicating more dependence on absorption than elimination. The half-lives after s.c. administration averaged 3 hours, whereas after i.v. administration, the half-lives were <1 hour. Metabolism of the ISIS 2302 after s.c. injection was consistent with exonucleolytic cleavage, as previously observed after i.v. administration. In summary, s.c. administration of PS-ODN resulted in prolonged and extensive absorption of the ODN.

Biodistribution and metabolism of a mixed backbone oligonucleotide (GEM 231) following single and multiple dose administration in mice

Biodistribution and metabolism of a mixed backbone oligonucleotide (MBO), GEM 231, targeted to the RIalpha subunit of protein kinase A has been studied in normal and tumor xenografted mice. The study has been carried out using [35S]-labeled MBO following single and multiple administrations of doses varying from 2 to 50 mg/kg. MBO showed wide tissue distribution following intravenous and subcutaneous administration. The highest concentration of MBO was in the kidney and liver. The general disposition of MBO was followed by digitized autoradiographic pictures of tumored mice and further confirmed wide tissue disposition and also showed defined intratumor uptake of MBO. Multiple dose administration showed increased disposition in the majority of the tissues/organs, with the exception of the kidneys. Analysis of the extracted MBO by polyacrylamide gel electrophoresis (PAGE) showed the presence of primarily intact MBO along with its degraded forms. Based on our radioactivity levels, the primary route of excretion was in urine, analysis of which showed mainly degraded forms of MBO.

Modulation of plasma protein binding and in vivo liver cell uptake of phosphorothioate oligodeoxynucleotides by cholesterol conjugation

Several studies have shown improved efficacy of cholesteryl-conjugated phosphorothioate antisense oligodeoxynucleotides. To gain insight into the mechanisms of the improved efficacy in vivo, we investigated the disposition of ISIS-9388, the 3'-cholesterol analog of the ICAM-1-specific phosphorothioate oligodeoxynucleotide ISIS-3082, in rats. Intravenously injected [(3)H]ISIS-9388 was cleared from the circulation with a half-life of 49.9 +/- 2.2 min (ISIS-3082, 23.3 +/- 3.8 min). At 3 h after injection, the liver contained 63.7 +/- 3. 3% of the dose. Compared to ISIS-3082, the hepatic uptake of ISIS-9388 is approximately 2-fold higher. Endothelial, Kupffer and parenchymal cells accounted for 45.7 +/- 5.7, 33.0 +/- 5.9 and 21.3 +/- 2.6% of the liver uptake of [(3)H]ISIS-9388, respectively, and intracellular concentrations of approximately 2, 75 and 50 microM, respectively, could be reached in these cells (1 mg/kg dose). Preinjection with polyinosinic acid or poly-adenylic acid reduced the hepatic uptake of [(3)H]ISIS-9388, which suggests the involvement of (multiple) scavenger receptors. Size exclusion chromatography of mixtures of the oligonucleotides and rat plasma indicated that ISIS-9388 binds to a larger extent to high molecular weight proteins than ISIS-3082. Analysis by agarose gel electrophoresis indicated that ISIS-9388 binds more tightly to plasma proteins than ISIS-3082. The different interaction of the oligonucleotides with plasma proteins possibly explains their different dispositions. We conclude that cholesterol conjugation results in high accumulation of phosphorothioate oligodeoxynucleotides in various liver cell types, which is likely to be beneficial for antisense therapy of liver-associated diseases.

Modification of the plasma clearance and liver uptake of steroid ester-conjugated oligodeoxynucleotides by association with (lactosylated) low-density lipoprotein

Low-density lipoprotein (LDL) has been proposed as carrier for the selective delivery of anticancer drugs to tumor cells. We reported earlier the association of several lipidic steroid-conjugated anticancer oligodeoxynucleotides (ODNs) with LDL. In the present study, we determined the stability of these complexes. When the complexes were incubated with a mixture of high-density lipoprotein and albumin, or with rat plasma, the oleoyl steroid-conjugated ODNs appeared to be more stably associated with LDL than the cholesteryl-conjugated ODN. Intravenously injected free lipid-ODNs were very rapidly cleared from the circulation of rats. The area under the curve (AUC) of the lipid-ODNs in plasma was <0.4 microg x min/mL. After complexation with LDL, plasma clearance of the lipid-ODNs was delayed. This was most evident for ODN-5, the ODN conjugated with the oleoyl ester of lithocholic acid (AUC = 6.82 +/- 1.34 microg x min/mL). The AUC of ODN-4, a cholesteryl-conjugated ODN, was 1.49 +/- 0.37 microg x min/mL. In addition, the liver uptake of the LDL-complexed lipid-ODNs was reduced. The lipid-ODNs were also administered as a complex with lactosylated LDL, a modified LDL particle that is selectively taken up by the liver. A high proportion of ODN-5 was transported to the liver along with lactosylated LDL (69.1 +/- 8.1% of the dose at 15 min after injection), whereas much less ODN-4 was transported (36.6 +/- 0.1% of the dose at 15 min after injection). We conclude that the oleoyl ester of lithocholic acid is a more potent lipid anchor than the other steroid lipid anchors. Because of the stable association, the oleoyl ester of lithocholic acid is an interesting candidate for tumor targeting of anticancer ODNs with lipoproteins.

A new liposomal formulation for antisense oligodeoxynucleotides with small size, high incorporation efficiency and good stability

Antisense oligodeoxynucleotides (asODN) are therapeutic agents that are designed to inhibit the expression of disease-related genes. However, their therapeutic use may be hindered due to their rapid clearance from blood and their inefficiency at crossing cell membranes. Cationic liposome complexes have been used to enhance the intracellular delivery of asODN in vitro; however, this type of carrier has unfavorable pharmacokinetics for most in vivo applications. Significant therapeutic activity of cationic liposomal asODN following systemic administration has not been demonstrated. In an effort to develop improved liposomal carriers for asODN for in vivo applications, we have evaluated the physical characteristics of two formulations which represent alternatives to cationic liposome-asODN complexes: asODN passively entrapped within neutral liposomes (PELA) and asODN formulated in a novel coated cationic liposomal formulation (CCL). Our results confirm that PELA can be extruded to small diameters that are suitable for intravenous administration. PELA are stable in human plasma; however, the incorporation efficiency is relatively low ( approximately 20%). The CCL formulation can also be extruded to small diameters (<200 nm), with significantly higher (80-100%) incorporation efficiency and are stable in 50% human plasma at 37 degrees C. A liposomal carrier for asODN with these characteristics may provide a significant therapeutic advantage over free asODN for some therapeutic applications.

Enhanced anti-inflammatory activity of a liposomal intercellular adhesion molecule-1 antisense oligodeoxynucleotide in an acute model of contact hypersensitivity

The anti-inflammatory activity of free and liposome-encapsulated oligonucleotide targeted against intercellular adhesion molecule-1 mRNA was investigated in a delayed type hypersensitivity model of acute inflammation in mice. Contact hypersensitivity reactions to 2, 4-dinitrofluorobenzene were monitored by measuring ear thickness and cellular infiltration, both of which were observed to be maximal 24 h after ear challenge. A murine-specific phosphorothioate oligodeoxynucleotide and various control sequences were each passively encapsulated into 100-nm diameter large unilamellar vesicles composed of egg phosphatidylcholine and cholesterol. All formulations were administered as a single-bolus injection into the tail vein approximately 15 min after initiating ear inflammation. Oligodeoxynucleotide dose was varied from 5 to 50 mg/kg and the extent of inflammation was assessed 24 h later. Mice treated with free oligonucleotide, empty vesicles, or encapsulated control sequences showed no measurable effect on ear swelling or cellular infiltration compared with untreated controls. However, mice that received the active sequence encapsulated in lipid vesicles exhibited near baseline levels of ear thickness and leukocyte infiltration, similar to that observed in mice treated with a topical corticosteroid. These data demonstrate the utility of liposome-encapsulated intercellular adhesion molecule-1 antisense oligonucleotide as a novel anti-inflammatory therapeutic.

Phase I study of an antisense oligonucleotide to protein kinase C-alpha (ISIS 3521/CGP 64128A) in patients with cancer

Protein kinase C (PKC) is an attractive target in cancer therapy. It is overexpressed in a variety of cancers, and nonspecific inhibitors of PKC have demonstrated antitumor activity. Antisense oligonucleotides targeted against PKC-alpha, which have high specificity, can inhibit mRNA and protein expression as well as the growth of tumors in vitro and in vivo. This Phase I study sought to characterize the safety profile and to determine the maximum tolerated dose of antisense to PKC-alpha when administered by continuous infusion in patients. Patients with incurable malignancies received ISIS 3521, a 20-length phosphorothioate oligodeoxynucleotide specific for PKC-alpha. Treatment was delivered over a period of 21 days by continuous i.v. infusion followed by a 7-day rest period. Doses were increased from 0.5 to 3.0 mg/kg/day. Patients continued on the study until evidence of disease progression or unacceptable toxicity was detected. Between August 1996 and September 1997, 21 patients were treated in five patient cohorts. The maximum tolerated dose was 2.0 mg/kg/day. The dose-limiting toxicities were thrombocytopenia and fatigue at a dose of 3.0 mg/kg/day. Pharmacokinetic measurements showed rapid plasma clearance and dose-dependent steady-state concentrations of ISIS 3521. Evidence of tumor response lasting up to 11 months was observed in three of four patients with ovarian cancer. The recommended dose of ISIS 3521 for Phase II studies is 2.0 mg/kg/day when given over a period of 21 days. Side effects are modest and consist of thrombocytopenia and fatigue. Evidence of antitumor activity provides the rationale for Phase II studies in ovarian cancer and other malignancies.

Phase I evaluation of ISIS 3521, an antisense oligodeoxynucleotide to protein kinase C-alpha, in patients with advanced cancer

PURPOSE

To determine the maximum-tolerated dose (MTD) and pharmacologic behavior of ISIS 3521 (ISI 641A), an antisense phosphorothioate oligonucleotide to protein kinase C-alpha.

PATIENTS AND METHODS

Thirty-six patients with advanced cancer received 99 cycles of ISIS 3521 (0.15 to 6.0 mg/kg/d) as a 2-hour intravenous infusion administered three times per week for 3 consecutive weeks and repeated every 4 weeks. Plasma and urine sampling was performed during the first week of treatment and subjected to capillary gel electrophoresis to determine full-length antisense oligonucleotide in addition to chain-shortened metabolites.

RESULTS

Drug-related toxicities included mild to moderate nausea, vomiting, fever, chills, and fatigue. Hematologic toxicity was limited to thrombocytopenia (grade 1, four patients; grade 2, one patient; grade 3, one patient). There was no relationship between dose, maximum concentration of the drug (C(max)), or area under the plasma concentration versus time curve (AUC) and coagulation times or complement levels. Dose escalation was discontinued because of the attainment of peak plasma concentrations, which approached that associated with complement activation in primates. Two patients with non-Hodgkin's lymphoma who completed 17 and nine cycles of therapy achieved complete responses. The pharmacokinetic profile of ISIS 3521 revealed a short elimination half-life (18 to 92 minutes), as well as a dose-dependent decrease in clearance and dose-dependent increases in C(max), AUC, and elimination half-life.

CONCLUSION

No dose-limiting toxicity of ISIS 3521 was identified, and clinical activity was observed. A short elimination half-life was identified, which suggests that alternate schedules with prolonged administration may be necessary for further clinical development.

Targeted delivery of oligodeoxynucleotides to parenchymal liver cells in vivo

Anti-sense oligodeoxynucleotides (ODNs) hold great promise for correcting the biosynthesis of clinically relevant proteins. The potential of ODNs for modulating liver-specific genes might be increased by preventing untimely elimination and by improving the local bioavailability of ODNs in the target tissue. In the present study we have assessed whether the local ODN concentration can be enhanced by the targeted delivery of ODNs through conjugation to a ligand for the parenchymal liver cell-specific asialoglycoprotein receptor. A capped ODN (miscellaneous 20-mer sequence) was derivatized with a ligand with high affinity for this receptor, N2-[N2-(N2,N6-bis{N-[p-(beta-d-galactopyranosyloxy) anilino] thiocarbamyl}-L-lysyl)-N6-(N-{p-[beta-D -galactopyranosyloxy] anilino} thiocarbamyl)-L-lysyl]-N6-[N- (p-{beta-D-galactopyranosyloxy}anilino)thiocarbamyl]-L-lysine (L3G4) (Kd 6.5+/-0.2 nM, mean+/-S.D.). Both the uptake studies in vitro and the confocal laser scan microscopy studies demonstrated that L3G4-ODN was far more efficiently bound to and taken up by parenchymal liver cells than underivatized ODN. Studies in vivo in rats showed that hepatic uptake could be greatly enhanced from 19+/-1% to 77+/-6% of the injected dose after glycoconjugation. Importantly, specific ODN accumulation of ODN into parenchymal liver cells was improved almost 60-fold after derivatization with L3G4, and could be attributed to the asialoglycoprotein receptor. In conclusion, the scavenger receptor-mediated elimination pathway for miscellaneous ODN sequences can be circumvented by direct conjugation to a synthetic tag for the asialoglycoprotein receptor. In this manner a crucial requisite is met towards the application of ODNs in vivo to modulate the biosynthesis of parenchymal liver cell-specific genes such as those for apolipoprotein (a), cholesterol ester transfer protein and viral proteins.

[Pharmacokinetics and stability in the blood in vivo of phosphodiester and modified oligonucleotide derivatives]

In vivo stability and distribution of deoxyribooligonucleotides and 3'-end modified oligodeoxyribooligonucleotides were studied in blood serum and cells. Substitution of two 3'-end internucleotide phosphodiester bonds increased the stability of modified oligonucleotides. Modified oligonucleotides were shown to be stable in blood serum for up to 24 hours. Leukocytes did not bind oligonucleotides significantly, whereas erythrocytes accumulate mono-, di-, three-, tetranucleotides appeared in the blood stream as degradation products of the parent oligonucleotide.