The stress response resolution assay. II. Quantitative assessment of environmental agent/condition effects on cellular stress resolution outcomes in epithelium

Cellular stress responses consist of a complex network of pathways and linked processes that, when perturbed, are postulated to have roles in the pathogenesis of various human diseases. To assess the impact of environmental insults upon this network, we developed a novel stress response resolution (SRR) assay for investigation of cellular stress resolution outcomes and the effects of environmental agents and conditions thereupon. SRR assay-based criteria identified three distinct groups of surviving cell clones, including those resembling parental cells, those showing Hprt/HPRT mutations, and a third type, "Phenotype-altered" clones, that occurred predominantly in cells pretreated with a chemical mutagen, was heterogeneous in nature, and expressed significant alterations in cell morphology and/or function compared with parental cells. Further evaluation of Phenotype-altered clones found evidence of various alterations that resembled epithelial-to-mesenchymal transition, phenotype switching, checkpoint dysfunction, senescence barrier bypass, and/or epigenetic reprogramming. Phenotype-altered clones were found to occur spontaneously in a cell line with a mutator phenotype, to represent the major surviving clone type in a variation of the SRR assay, and to be tumorigenic in nude mice. Assessment of SRR assay final results showed that pretreatment with a chemical mutagen induced significant changes in cellular stress response prosurvival capacity, in damage avoidance versus damage tolerance stress resolution outcomes, and in the damage burden in the final surviving cell populations. Taken together, these results support the conclusion that use of the SRR assay can provide novel insights into the role of environmental insults in the pathogenesis of cancer and other human diseases.

The stress response resolution assay. I. Quantitative assessment of environmental agent/condition effects on cellular stress resolution outcomes in epithelium

The events or factors that lead from normal cell function to conditions and diseases such as aging or cancer reflect complex interactions between cells and their environment. Cellular stress responses, a group of processes involved in homeostasis and adaptation to environmental change, contribute to cell survival under stress and can be resolved with damage avoidance or damage tolerance outcomes. To investigate the impact of environmental agents/conditions upon cellular stress response outcomes in epithelium, a novel quantitative assay, the "stress response resolution" (SRR) assay, was developed. The SRR assay consists of pretreatment with a test agent or vehicle followed later by a calibrated stress conditions exposure step (here, using 6-thioguanine). Pilot studies conducted with a spontaneously-immortalized murine mammary epithelial cell line pretreated with vehicle or 20 µg N-ethyl-N-nitrososurea/ml medium for 1 hr, or two hTERT-immortalized human bronchial epithelial cell lines pretreated with vehicle or 100 µM zidovudine/lamivudine for 12 days, found minimal alterations in cell morphology, survival, or cell function through 2 weeks post-exposure. However, when these pretreatments were followed 2 weeks later by exposure to calibrated stress conditions of limited duration (for 4 days), significant alterations in stress resolution were observed in pretreated cells compared with vehicle-treated control cells, with decreased damage avoidance survival outcomes in all cell lines and increased damage tolerance outcomes in two of three cell lines. These pilot study results suggest that sub-cytotoxic pretreatments with chemical mutagens have long-term adverse impact upon the ability of cells to resolve subsequent exposure to environmental stressors.

Intracerebral and intrathecal infusion of the TGF-beta 2-specific antisense phosphorothioate oligonucleotide AP 12009 in rabbits and primates: toxicology and safety

Here, we provide first evidence that long-term continuous infusion of highly purified antisense phosphorothioate oligodeoxynucleotides (S-ODN) into brain parenchyma is well tolerated and thus highly suitable for in vivo application. AP 12009 is an S-ODN for the therapy of malignant glioma. It is directed against human transforming growth factor-beta (TGF-beta2) mRNA. In the clinical setting, AP 12009 is administered intratumorally by continuous infusion directly into the brain tumor. In view of this clinical application, the focus of our data is on local toxicology studies in rabbits and monkeys to evaluate the safety of AP 12009. AP 12009 was administered either by intrathecal bolus injection into the subarachnoidal space of the lumbar region of both cynomolgus monkeys and rabbits or by continuous intraparenchymatous infusion directly into the brain tissue of rabbits. Intrathecal bolus administration of 0.1 ml of 500 microM AP 12009 showed neither clinical signs of toxicity nor macroscopically visible or histomorphologic changes. After a 7-day intraparenchymatous continuous infusion of 500 microM AP 12009 at 1 microl/h in rabbits, there was no evidence of toxicity except for local mild to moderate lymphocytic leptomeningoencephalitis. Additionally, AP 12009 showed good tolerability in safety pharmacology as well as in acute toxicity studies and 4-week subchronic toxicity studies in mice, rats, and monkeys. This favorable safety profile proves the suitability of AP 12009 for local administration in brain tumor patients from the point of view of toxicology.

Potent inhibition of HIV-1 entry by (s4dU)35

We have previously reported the potent in vitro HIV-1 anti-reverse transcriptase activity of a 35-mer of 4-thio-deoxyuridylate [(s(4)dU)(35)]. In efforts to define its activity in a more physiological system, studies were carried out to determine the stage of viral infection that this compound mediates its anti-viral effect. Results of the studies reported herein show that (s(4)dU)(35) is nontoxic and is capable of inhibiting both single and multi-drug resistant HIV strains (IC(50): 0.8-25.4 microg/ml) in vitro. Besides its previously reported anti-RT activity, (s(4)dU)(35) mediated its antiviral action by preventing virus attachment (IC(50): 0.002-0.003 microg/ml), and was stable in vitro and slowly degraded by DNAses. Competition studies and fluorescence resonance energy transfer (FRET) experiments indicated that (s(4)dU)(35) preferentially binds to CD4 receptors, but not to CD48. Confocal laser scanning microscopy (CLSM) studies showed that (s(4)dU)(35) did not penetrate into the cells and colocalized with cell surface thioredoxin. Our studies identify (s(4)dU)(35) as a potential novel HIV entry inhibitor that may have utility as either a systemic antiretroviral or as a preventing agent for HIV transmission.

Effects of human and murine antisense oligonucleotide inhibitors of ICAM-1 on reproductive performance, fetal development, and post-natal development in mice

The potential for reproductive toxicity of an antisense oligonucleotide designed to inhibit ICAM-1 was evaluated as part of the safety assessment for this compound. Since antisense compounds are often specific to the species in which they are intended to work, both the human and murine active ICAM-1 inhibitors were tested (ISIS 2302 and ISIS 3082, respectively). Male and female mice were treated prior to cohabitation, through cohabitation, gestation, delivery, and weaning. Mice were treated with 0, 3, 6, and 12 mg/kg ISIS 2302 or ISIS 3082 by daily i.v. injection. Reproductive indices evaluated included estrus cycling, sperm count and motility, fertility, litter parameters, fetal development, delivery, fetal body weight, lactation, and weaning. Behavioral assessment and reproductive capacity of the F1 generation mice was assessed on selected animals. Concentrations of oligonucleotide in selected maternal target organs, placenta, fetal tissues, and expressed milk were also measured. There were no changes in reproductive performance, litter parameters, fetal development, or postnatal development in mice treated with either ISIS 2302 or ISIS 3082. Maternal liver and kidney contained dose-dependent concentrations of oligonucleotide, but there was relatively little or no oligonucleotide measured in placenta, fetal tissues, or expressed milk. Neither the human nor murine-specific antisense inhibitor of ICAM-1 produced any reproductive toxicity in mice, and exposure of fetus or pups was negligible.

Effects of an antisense oligonucleotide inhibitor of human ICAM-1 on fetal development in rabbits

The potential for reproductive toxicity of an antisense oligonucleotide designed to inhibit ICAM-1 was evaluated as part of the safety assessment for this compound. The human active ICAM-1 inhibitor (ISIS 2302) is not pharmacologically active in rabbits. Female rabbits were treated once daily on Day 6 through 18 of gestation. Rabbits were treated with 0, 1, 3, and 9 mg/kg ISIS 2302 by daily i.v. injection. Reproductive indices evaluated included estrus cycling, litter parameters, fetal development, and fetal body weight. Concentrations of oligonucleotide in plasma following the last dose, and in selected maternal target organs, placenta, and fetal tissues at scheduled necropsy were also measured. Maternal toxicity was evident as a decreased maternal body weight gain, decreased food consumption, and scant feces at doses > or =3 mg/kg. Increased spleen to body weight ratio and increased mononuclear cell infiltrates were indicative of a proinflammatory effect of ISIS 2302 at the 9 mg/kg dose level. Despite the maternal toxicity, there were no changes in litter parameters or fetal development in rabbits treated with ISIS 2302. The only change was a decrease in fetal body weight at the 9 mg/kg dose level, which was attributed to the maternal toxicity observed. Maternal liver and kidney contained dose-dependent concentrations of oligonucleotide, but there was relatively little or no oligonucleotide measured in placenta or fetal tissues. Thus, there was no dose-dependent exposure and maternal toxicity to ISIS 2302, but no reproductive toxicity in rabbits, and exposure of fetus or pups is negligible.

Chronic hyperalgesic priming in the rat involves a novel interaction between cAMP and PKCepsilon second messenger pathways

Toward the goal of defining new pharmacological targets for the treatment of chronic pain conditions, in previous studies we established a model, termed 'hyperalgesic priming,' in which an acute inflammatory stimulus causes a long-lasting latent susceptibility to hyperalgesia induced by subsequent exposures to the inflammatory mediator, prostaglandin E2 (PGE2). Those investigations suggested the hypothesis that priming induces a novel linkage between the PGE2-activated second messenger cascade and the epsilon isoform of protein kinase C (PKCepsilon). In the present study, comparison of dose-response relations for hyperalgesia produced by PGE2, forskolin, 8-Br-cAMP, or the protein kinase A (PKA) catalytic subunit, in primed versus normal animals, demonstrated that priming-induced enhancement of the PGE2-activated second messenger cascade occurs downstream to adenylate cyclase and upstream to PKA. Therefore, PGE2-induced hyperalgesia in the primed animal is enhanced by the recruitment of a novel cAMP/PKCepsilon signaling pathway in addition to the usual cAMP/PKA pathway. These observations suggest that pharmacological disruption of the novel interaction between cAMP and PKCepsilon might provide a route toward the development of highly specific methods to reverse cellular processes that underlie chronic pain states.

Phase I and phase II safety and efficacy trial of intercellular adhesion molecule-1 antisense oligodeoxynucleotide (ISIS 2302) for the prevention of acute allograft rejection

BACKGROUND

ISIS 2302, an antisense oligonucleotide that inhibits the expression of human intercellular adhesion molecule (ICAM)-1, was evaluated in combination with a cyclosporine (CsA)-prednisone (Pred) regimen first in a phase I safety and pharmacokinetic study and then in a phase II assessment of prophylaxis of acute rejection episodes in deceased donor renal allografts.

METHODS

Both phase I and phase II trials were double-blinded and placebo-controlled, including 17 stable and 39 de novo patients, respectively, in time-lagged, ascending-dose regimens. Each study compared the outcomes of 8 alternate-day intravenous infusions of four ISIS 2302 dose levels (0.05, 0.5, 1.0, or 2.0 mg/kg) versus placebo (3:1 ratio). Patients were followed for 34 days (phase I) or 6 months (phase II). All transplant patients were followed for 3 years.

RESULTS

ISIS 2302 produced no evident toxicity; a significant, dose-related increase in activated partial thromboplastin time was accompanied by a trend toward a decreased platelet count. ISIS 2302 did not alter the pharmacokinetic behavior of CsA. At 6 months, the rates of acute rejection episodes were 38.1% in the ISIS 2302 group versus 20.0% in the placebo group. Three-year graft survivals were similar. The mean creatinine values at 1, 2, and 3 years for all ISIS dose groups combined versus placebo over 3 years showed no significant differences.

CONCLUSIONS

ISIS 2302 did not evoke side-effects and produced slightly improved renal function. However, in this pilot study, it did not further reduce the rate of acute rejection episodes or increase graft survival compared to a concentration-controlled CsA-Pred regimen.

Nonmethylated CG Motifs Packaged into Virus-Like Particles Induce Protective Cytotoxic T Cell Responses in the Absence of Systemic Side Effects

DNA rich in nonmethylated CG motifs (CpGs) greatly facilitates induction of immune responses against coadministered Ags. CpGs are therefore among the most promising adjuvants known to date. Nevertheless, CpGs are characterized by two drawbacks. They have unfavorable pharmacokinetics and may exhibit systemic side effects, including splenomegaly. We show in this study that packaging CpGs into virus-like particles (VLPs) derived from the hepatitis B core Ag or the bacteriophage Qbeta is a simple and attractive method to reduce these two problems. CpGs packaged into VLPs are resistant to DNase I digestion, enhancing their stability. In addition, and in contrast to free CpGs, packaging CpGs prevents splenomegaly in mice, without affecting their immunostimulatory capacity. In fact, vaccination with CpG-loaded VLPs was able to induce high frequencies of peptide-specific CD8(+) T cells (4-14%), protected from infection with recombinant vaccinia viruses, and eradicated established solid fibrosarcoma tumors. Thus, packaging CpGs into VLPs improves both their immunogenicity and pharmacodynamics.

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.

The glutathione-activated thiopurine prodrugs trans-6-(2-acetylvinylthio)guanine and cis-6-(2-acetylvinylthio)purine cause less in vivo toxicity than 6-thioguanine after single- and multiple-dose regimens

trans-6-(2-Acetylvinylthio)guanine (trans-AVTG) and cis-6-(2-acetylvinylthio)purine (cis-AVTP) are glutathione-activated prodrugs of 6-thioguanine (6-TG) and 6-mercaptopurine, respectively. In tumor cell lines, these prodrugs exhibit similar IC50 values that are comparable to or lower than those of 6-TG and 6-mercaptopurine, respectively. In this study, the in vivo toxicity and metabolism of the prodrugs were assessed. Mice given multiple treatments of 6-TG and, to a lesser extent, trans-AVTG exhibited decreased peripheral WBC and RBC counts and increased myeloid:erythroid ratios in bone marrow; no change was observed in mice given cis-AVTP. Similarly, intestinal epithelial crypt cell apoptosis was more extensive in mice treated with 6-TG than in those treated with trans-AVTG, whereas mice given cis-AVTP had little apoptosis. Epithelial crypt cell apoptosis was more extensive in the small intestine than in the large intestine in all treatment groups. Histopathological examination detected no kidney or liver toxicity, whereas mild increases in the activities of hepatocellular leakage enzymes were observed in mice treated with trans-AVTG. Only metabolites of trans-AVTG and cis-AVTP were recovered in urine. A higher fraction of the dose was recovered in urine as the parent thiopurine and the metabolites thiopurine riboside, thioxanthine, and thiouric acid after 6-TG treatment than after trans-AVTG treatment; cis-AVTP recovery was slightly less than that of 6-TG. Thioxanthine and thiouric acid comprised a higher fraction of the recovered dose after cis-AVTP treatment than after trans-AVTG or 6-TG treatment. Overall, the results suggest that the prodrugs exhibit less in vivo toxicity than 6-TG. Thus, investigations into their antitumor efficacy are warranted.

A randomized phase II and pharmacokinetic study of the antisense oligonucleotides ISIS 3521 and ISIS 5132 in patients with hormone-refractory prostate cancer

PURPOSE

Protein kinase C (PKC)-alpha and Raf-1 are important elements of proliferative signal transduction pathways in both normal and malignant cells. Abrogation of either Raf-1 or PKC-alpha function can both inhibit cellular proliferation and induce apoptosis in several experimental cancer models including prostate cancer cell lines. ISIS 3521 and ISIS 5132 are antisense phosphorothioate oligonucleotides that inhibit PKC-alpha and Raf-1 expression, respectively, and induce a broad spectrum of antiproliferative and antitumor effects in several human tumor cell lines. In Phase I evaluation both ISIS 3521 and ISIS 5132 could be safely administered on 21-day i.v. infusion schedules and demonstrated preliminary evidence of antitumor activity. On the basis of these findings, a randomized Phase II study of ISIS 3521 and ISIS 5132 was performed in two comparable cohorts of patients who had chemotherapy-naïve, hormone-refractory prostate cancer (HRPC).

PATIENTS AND METHODS

Patients with documented evidence of metastatic HRPC and a prostate-specific antigen (PSA) value > or =20 ng/ml were randomized to receive treatment with either ISIS 3521 or ISIS 5132 as a continuous i.v. infusion for 21 days repeated every 4 weeks. Patients were stratified according to the presence or absence of bidimensionally measurable disease at the time of randomization. The principal endpoints included PSA response, objective response in patients with bidimensionally measurable disease, and treatment failure defined as new or worsening symptoms; a fall in performance status of 2 levels; new or objective progression of disease; or a rise in PSA for 12 weeks without symptom improvement. Plasma samples were collected to assess individual steady-state concentrations and to relate this pharmacokinetic parameter to observed toxicities and responses.

RESULTS

Thirty-one patients were randomized in this study; 15 patients received 43 courses of ISIS 3521 and 16 patients received 48 courses of ISIS 5132. The most common toxicities observed were mild to moderate (grade 1 or 2) fatigue and lethargy in 21% and 56% of patients treated with ISIS 3521 and ISIS 5132, respectively. Although no objective or PSA responses were observed in any patient treated with ISIS 3521 or ISIS 5132, persistent stable disease was observed in 3 patients for 5 or more months, and in 5 patients the PSA values did not rise >25% for 120 days or longer.

CONCLUSIONS

The antisense oligonucleotides ISIS 3521 and ISIS 5132, at these doses and on this schedule, do not possess clinically significant single-agent antitumor activity in HRPC. Protracted stable disease in some patients may indicate a cytostatic effect. Additional work is required to define the optimal role of PKC-alpha or Raf-1 inhibition in the treatment of HRPC.

Influence of polymer architecture on the structure of complexes formed by PEG-tertiary amine methacrylate copolymers and phosphorothioate oligonucleotide

The influence of polymer structure on the characteristics of complexes of a phosphorothioate antisense oligonucleotide (ISIS 5132) was studied, using well-defined cationic copolymers based on 2-(dimethylamino) ethyl methacrylate (DMAEMA) and poly(ethylene glycol) (PEG). The three related copolymer structures were: DMAEMA-PEG (a diblock copolymer) DMAEMA-OEGMA 7 (a brush-type copolymer), DMAEMA-stat-PEGMA (a comb-type copolymer); each of these were examined together with DMAEMA homopolymer, which served as a control. The results revealed that all the polymers exhibited good binding ability with the oligonucleotide (ON). Interestingly, the comb-type polymer DMAEMA-stat-PEGMA demonstrated the highest binding ability and DMAEMA homopolymer the lowest, as judged by a dye displacement assay. DMAEMA homopolymer produced large agglomerates of smaller individual complexes as observed by optical density, photon correlation spectroscopy and transmission electron microscopy studies. In contrast, two PEG-block copolymers, DMAEMA-PEG and DMAEMA-OEGMA 7, formed compact complexes of 80-150 nm which had good long-term colloidal stability. This is attributed to the steric stabilisation effect of the PEG chains on the ON-copolymer complexes. These two copolymers are believed to form complexes with ON that have a micellar structure. Comb-type DMAEMA-stat-PEGMA copolymer formed highly soluble complexes with the ON that did not phase separate from the buffer solution. This study clearly demonstrates that varying the copolymer architecture allows access to a range of ON complexes. In vitro cytotoxicity experiments on HepG2 cells showed that all of the tertiary amine methacrylate copolymers displayed lower cytotoxicity than the control poly(L-lysine).

Assessment of the genotoxic potential of ISIS 2302: a phosphorothioate oligodeoxynucleotide

ISIS 2302, a phosphorothioate oligodeoxynucleotide with antisense activity against human ICAM-1 mRNA, was evaluated in a battery of tests to assess genotoxic potential. There was no evidence of genotoxicity in three in vitro studies performed: (i) a bacterial reverse mutation test; (ii) a chromosomal aberration test in Chinese hamster ovary cells; (iii) a mammalian cell gene mutation assay in L5187Y cells. Additionally, there was no in vivo evidence of genetic toxicity in a bone marrow micronucleus study in male and female mice. For all tests, top concentrations or doses assessed met harmonized regulatory guidelines. The cellular uptake of ISIS 2302 into target cells was confirmed using capillary gel electrophoresis and immunohistochemistry. Intracellular uptake into CHO cells, L5187Y cells, Salmonella typhimurium TA98 and bone marrow was concentration- and time-dependent. Consistent with what is known about the physical and chemical properties of phosphorothioate oligodeoxynucleotides, there was no evidence of genotoxicity in any of the assessed end-points. Furthermore, the absence of genotoxicity could not be ascribed to test system insensitivity or to an absence of exposure of the test system to ISIS 2302.

ISIS-3521. Isis Pharmaceuticals

ISIS-3521 is a 20-mer antisense phosphorothioate oligonucleotide PKCa expression inhibitor, under development by Isis (formerly in collaboration with Novartis) for the potential treatment of solid tumors that are refractory to, or recurrent with, standard treatment regimens [175741]. In November 1999, Novartis announced that it would end its codevelopment of ISIS-3521 [348221], [348222]. In August 2001, Eli Lilly in-licensed ISIS-3521 [420062]. In October 2000, phase III trials of ISIS-3521, in combination with carboplatin and paclitaxel, were initiated for the treatment of non-small cell lung cancer (NSCLC) [386128]. The FDA granted ISIS-3521 Fast Track review status for NSCLC in November 2000 [388930]. In April 2001, Bear Sterns & Co predicted US approval of ISIS-3521 in 2002 [411081]. In August 2001, Eli Lilly and Isis entered into a four-year strategic alliance that includes ISIS-3521. For the license of ISIS-3521, Isis will receive $25 million in upfront fees and will be reimbursed for remaining phase III development and registration costs [420062].

Alicaforsen. Isis Pharmaceuticals

Alicaforsen (ISIS-2302) is an RNase H-dependent antisense inhibitor of the intercellular adhesion molecule ICAM-1 under development by Isis Pharmaceuticals, for the potential treatment of a variety of inflammatory disorders [175741]. As of April 1997 it was in phase III trials for Crohn's disease (CD); however, the trial failed and, in December 1999, the company suspended development for this indication [352801]. In October 2000, the company re-initiated development in CD [384820] and new phase III trials had begin by May 2001 [409704]. In August 2000, phase II studies of alicaforsen in an enema formulation for ulcerative colitis and a topical formulation for psoriasis were ongoing [378715]. Development of the compound for the potential treatment of rheumatoid arthritis (RA) was discontinued in 1999 [347579]. By the end of 1998, alicaforsen was in phase II trials for kidney transplant rejection. At this time, these trials were expected to finish in mid-1999 [343460]. However, they were ongoing in September 1999, although no further development has been reported for this indication since that time [338672]. In February 1995, Isis Pharmaceuticals and Boehringer Ingelheim (BI) signed a collaborative agreement on cell adhesion inhibitors, including alicaforsen [174111]. By early 1999, Isis and BI were to decide on the next developmental step for alicaforsen following further analyses of its performance against CD [292915], [315439]. Their joint development agreement was terminated in 1999; Isis regained rights to the product and by September 1999 was in talks to license alicaforsen to another partner for CD [338672]. In June 2000, Cytogenix entered into a sponsored research agreement with Baylor College of Medicine at the Texas Medical Center Houston for the use of its ssDNA expression system for the development of antisense strategies directed against intercellular adhesion molecules for the purpose of reducing lung inflammation and injury in disease states and conditions [369677]. US-05514788, and other patents, cover antisense cell adhesion molecule inhibitors [212289], [234792].

Uptake dynamics and retinal tolerance of phosphorothioate oligonucleotide and its direct delivery into the site of choroidal neovascularization through subretinal administration in the rat

This study aimed to investigate uptake dynamics and retinal tolerance of phosphorothioate oligonucleotides (PS-oligos) following subretinal injection. A fluorescent-labeled PS-oligo (FL-oligo) with random sequence was administered into the subretinal space of rat by transsclera-choroid-retinal pigment epithelium (RPE) injection at doses of 0.129, 1.29, and 12.9 microg in 2.0 microl solution. The uptake dynamics were evaluated by fundus fluorescent photography in real time and by fluorescence microscopy using flat mounts and cryosections. Immunophenotyping for CD4+, CD8+ cytotoxic lymphocytes, and CD68+ macrophages was performed to assess cellular infiltration in the retina. In addition, the FL-oligo was injected subretinally in a rat model of choroidal neovascularization (CNV) for direct delivery into the site of CNV. Subretinal administration of FL-oligo resulted in both dose-dependent and time-dependent distribution in the retina, where it accessed the RPE and all layers of the neuroretina. CD4+, CD8+ cytotoxic lymphocytes, and CD68+ macrophages were observed at the site of needle penetration. However, in areas far from the injection site where the FL-oligo appeared strongly, cellular infiltration was absent, and the retinal morphology was preserved very well. The FL-oligo was successfully delivered into the site of intense laser photocoagulation. It was predominantly localized to the RPE, macrophages, and some choroid cells and remained detectable for at least 56 days after injection. Our results demonstrate for the first time that subretinal injection efficiently introduced PS-oligo into the RPE and neuroretina with an acceptable level of safety. Subretinal administration of antiangiogenic oligonucleotides may hold great potential for the treatment of CNV.

Toxicity and toxicokinetics of a phosphorothioate oligonucleotide against the c-myc oncogene in cynomolgus monkeys

A 2-week toxicity and toxicokinetic study of a 15-mer phosphorothioate oligonucleotide, INX-3280, against the c-myc oncogene was performed in cynomolgus monkeys. As this oligonucleotide readily adopts an aggregate structure, a quadruplex, which may be associated with adverse physiologic effects, this study was performed using INX-3280 that had been converted to its monomeric form. Animals received intravenous (i.v.) infusions of monomeric INX-3280 three times per week for 2 weeks at doses of 3 or 15 mg/kg per administration. The monkeys were examined for clinical signs: changes in hematology, serum chemistry, coagulation, and urinalysis parameters; complement activation; macroscopic findings at necropsy; and histopathologic alterations. In addition, the toxicokinetics of INX-3280 were evaluated, using a validated HPLC assay, after the first and last (sixth) doses. No treatment-related clinical signs of any adverse effects were observed, and there were no test article-related changes in hematology, serum chemistry, or complement activation parameters. The only alteration in clinical pathology parameters was a minor (30%) prolongation of the activated partial thromboplastin time (aPTT), reflecting slight inhibition of the intrinsic coagulation pathway, which was less than that reported with other oligonucleotides given at similar doses. Treatment-related histopathologic alterations consisted of characteristic accumulation of basophilic material in the cytoplasm of tubular epithelial cells in the kidney, resident macrophages in the lymph nodes, and Kupffer cells in the liver. These changes were graded as minimal in all cases. The basophilic material is believed to reflect accumulation of the oligonucleotide or metabolites or both. The pharmacokinetic parameters of INX-3280 were identical on the first and sixth administrations and were similar to those reported for other phosphorothioate oligonucleotides. Maximum concentration (Cmax) values for INX-3280 (101-119 microg/ml) were in excess of the threshold plasma concentrations reported to trigger complement activation by phosphorothioate oligonucleotides. It is concluded that the safety profile of monomeric INX-3280 in cynomolgus monkeys is quite favorable relative to the known effects of other phosphorothioate oligonucleotides, particularly with respect to the blood level-related toxicities of this class of compounds, including complement activation and inhibition of coagulation. This study found no toxicities that were expected to be clinically significant.

[The toxic effects of high-dose Bcl-2 antisense phosphorothioate oligodeoxynucleotides incubation on cell line]

OBJECTIVE

To investigate the toxic effects of high-dose Bcl-2 antisense phosphorothioate oligodeoxynucleotides (AS-PS-ODN, ASPO) incubation on HL60 cells and to understand the relationship between the dose of ASPO and the toxicity.

METHODS

Cellular viability and toxicity were detected by trypan blue exclusion, colony-forming unit HL60 cells and MTT assay. The expression of Bcl-2 protein was determined by immunocytochemistry and flow cytometry analysis. The proportion of apoptosis cells was tested by acridine orange (AO) standing. The sense (PS-ODN, SPO) was chosen for the toxic control of independent sequence. The curves of dose-effect and dose-toxicity were transfered into straight line and the reguession analysis was done by computer with the SPSS soften-ware.

RESULTS

When the dose of Bcl-2 PS-ODN was higher than 20 micromol/L, the non-specific effect of suppressing cell proliferation could occur. When the dose of Bcl-2 PS-ODN was more than 160 micromol/L, the non-specific effect (toxic effect) increased significantly. When the dose of Bcl-2 ASPO was higher than 80 micromol/L, the specific effect of inhibitting the expression of Bcl-2 proteion increased slowly. When the dose of PS-ODN reached 262 micromol/L, the toxic effect had no significant differences between Bcl-2 ASPO and Bcl-2 SPO. In the presence of ASPO or SPO at 160 micromol/L, the expression of Bcl-2 protein in the two groups of HL60 was decreased to 28% and 78% respectively, after 72 hours of incubation. The expression of Bcl-2 protein in the groups of HL60 which were passaged after incubation with ASPO or SPO was reinereased to 99.6% and 97.8%, respectively.

CONCLUSION

Although ASPO is a kind of low-toxic drug, the toxic effects of Bcl-2 ASPO seem to be dependent on the dose increasing to a certain extent. It is clear that it can be used over a wide range of doses, however. Our results may also provide some referring concentrations of Bcl-2 ASPO for the pharmacodynamic and toxicological study in vivo in future.

Raf-1 kinase activity predicts for paclitaxel resistance in TP53mut, but not TP53wt human ovarian cancer cells

We have recently reported that there is a significant Raf-1 kinase dependency of paclitaxel resistance in human cervical tumor cell lines. In light of the possibility that Raf-1 kinase inhibitors could be used to enhance paclitaxel responsiveness in ovarian cancer, we have characterized the Raf-1 kinase dependency of paclitaxel resistance in ovarian cancer cells. The relationship between Raf-1 kinase activity and the sensitivity to clinically relevant paclitaxel concentrations was determined in four ovarian cancer cell lines (CA-OV3, SK-OV3, 2780/WT and OAW42/WT). Furthermore, in recognition that such a drug combination would initially be used in patients whose tumors have recurred following cisplatin/paclitaxel treatment, we also determined the Raf-1 kinase dependency of paclitaxel cytotoxicity in cisplatin resistant variants of two of the ovarian cell lines (2780/CP and OAW42/CP). In the two cell lines (2780/WT and OAW42/WT) that possess a wild-type TP53 (TP53wt), the relationship between Raf-1 kinase activity and paclitaxel resistance was different from that observed in the cervical tumor cell lines. In these cell lines, paclitaxel-induced far more cell killing than would have been predicted from their Raf-1 kinase activity. However, in the ovarian cancer cell lines (CA-OV3, SK-OV3, 2780/CP and OAW42/CP) that have a mutant TP53 (TP53mut), the cytotoxicity induced by 60 nM paclitaxel exhibited the same relationship to Raf-1 kinase activity as previously observed in cervical tumor cell lines. These data suggest that the therapeutic efficacy of paclitaxel in ovarian cancer patient whose tumors have TP53mut might be increased if it is administered in combination with Raf-1 kinase inhibitors, e.g., ISIS 5132.

Molecular and pharmacokinetic properties associated with the therapeutics of bcl-2 antisense oligonucleotide G3139 combined with free and liposomal doxorubicin

Bcl-2 is a key apoptosis-regulating protein that has been implicated in mechanisms of chemoresistance for a variety of malignancies by blocking programmed cell death. This study investigated the activity of the Bcl-2 antisense oligodeoxynucleotide (AS ODN) G3139 combined with free doxorubicin (F-DOX) or sterically stabilized liposomal doxorubicin (SL-DOX) to determine the role that drug pharmacodistribution properties may have on antitumor activity using a Bcl-2-expressing human breast solid tumor xenograft model. Administration of G3139 was able to delay the growth of MDA435/LCC6 cells compared with control ODN-treated animals; however, in all of the cases, tumors reestablished after AS ODN treatment. Western blot analyses of Bcl-2 levels of solid tumors showed a sequence-specific down-regulation of the Bcl-2 protein after four daily doses of G3139, which correlated with histological evidence of tumor cell death. Interestingly, the expression of Bcl-2 returned to pretreatment levels during the course of subsequent ODN administration, which suggested the development of resistance to continued Bcl-2 ODN treatment. The antitumor activity of ODN given in conjunction with either F-DOX or SL-DOX was also examined. The combination of G3139 and F-DOX was able to suppress the growth of MDA435/LCC6 cells beyond that obtained with either of the treatments given alone, indicative of synergistic action. Examination of the pharmacokinetics of F-DOX with systemic G3139 administration revealed that elevated tumor drug DOX levels were obtained compared with DOX treatment in the absence of G3139. This effect was sequence-specific and plasma DOX levels were unaffected by G3139 treatment, which indicated possible positive ODN-drug interactions at the tumor site. Combining G3139 with SL-DOX further increased the degree of antitumor activity. The improved efficacy of this combination was attributed to increased tumor drug levels that arise from the ability of SL-DOX to passively accumulate in solid tumors. These results suggest that additional benefits of Bcl-2 antisense ODN may be obtained when it is combined with liposomal formulations of anticancer drugs such as DOX.

Toxicological evaluation of oligonucleotide therapeutics

In this brief review, guidance is provided for the safety evaluation of phosphorothioate oligonucleotides. This novel class of compounds has proved to be challenging for the preclinical development scientist, as systemic exposure can evoke sometimes dramatic responses, in terms of general functional parameters, laboratory data (hematology, clinical chemistry) and histopathology of target organs. The polyanionic profile of these compounds is discussed vis-à-vis historical data for related structures. Dose-related responses in various laboratory test species are described. The liver, kidneys and immune system are major target organs, and an experimental perspective is provided for understanding each of these in determining a safe starting dose for clinical trials with novel compounds.

Bolus intravenous injection of phosphorothioate oligonucleotides causes hypotension by acting as alpha(1)-adrenergic receptor antagonists

Bolus intravenous injections of phosphorothioate oligonucleotides (PS-ODN) into primates cause profound hypotension, which has been attributed to complement activation, the biochemical pathway leading to acute inflammatory response. Because the hypotension was not accompanied by peripheral or pulmonary edema and epinephrine was not effective, but administration of 200 ml Ringer's lactate was effective, we examined the possibility that the 15-base PS-ODN interferes with sympathetic tone. We administered doses ranging from 3.3 to 10 mg/kg of a 15-base PS-ODN as a 30-60 s iv bolus into the right atrium of conscious Macaca mulatta. Blood pressure fell to 27 mm Hg following a 5.0 mg/kg dose, but no hypotension was observed after a 3.3 mg/kg dose; 10 mg/kg was lethal. Adrenergic receptor binding was evaluated in radioligand binding assays using rat cerebral cortex membranes with radiolabeled prazosin. The 15-base PS-ODN competes with prazosin for the alpha(1)-adrenergic receptor with an IC50 of 14 microM, which favors binding over serum albumin (K(d) = 37 to 48 microM). Admixing serum albumin with 5.0 mg/kg 15-base PS-ODN prior to injection prevented hypotension, suggesting that unbound PS-ODN interferes with sympathetic tone before binding to plasma proteins. Interactions of the 15-base PS-ODN with the alpha(1)-adrenergic receptor in vivo were confirmed by a decreased response to phenylephrine. Reducing the length from 15 to 9 or 5 bases abolished alpha(1)-adrenergic receptor binding in vitro and bolus infusion of 5.0 mg/kg of 9-base PS-ODN no longer produced hypotension. In conclusion, the 15-base PS-ODN shows cooperative binding to the alpha(1)-adrenergic receptor, which produces cardiovascular effects that are oligomer length, dose, and formulation dependent.

Oligonucleotides as inhibitors of human immunodeficiency virus

Inhibition of human immunodeficiency virus (HIV) replication by oligonucleotides is a complex process and may be implemented by an array of antiviral mechanisms. These include inhibition of virus adsorption to the host cell, inhibition of transcription via antisense or as the result of triple helix formation, and inhibition of viral encoded enzymes such as reverse transcriptase and integrase. Since the particular mechanism of HIV inhibition depends on the oligonucleotide (ON) sequence and the ON chemical modifications, the design and synthesis of potent HIV inhibitors has been an important and rewarding focus of ON research. In this era of great concern that HIV may rapidly display resistance to any antiviral compound with one mechanism of viral inhibition, oligonucleotides are potentially attractive alternatives for therapy. Several ONs have entered clinical evaluation in AIDS patients. At present Zintevir, which inhibits both HIV adsorption and HIV integrase, is in phase I/II clinical trials.

Toward antisense oligonucleotide therapy for cancer: ISIS compounds in clinical development

Antisense oligonucleotides offer the promise of therapeutic effect with few toxic effects, by virtue of their high selectivity. Preclinical studies have provided evidence of antisense effects in vitro and in vivo, and phase I clinical trials have demonstrated safety, feasibility and activity of antisense oligonucleotides for the treatment of cancer. This review summarizes the status of development of three anticancer antisense oligonucleotides from ISIS Pharmaceuticals.

Evaluation of the renal effects of an antisense phosphorothioate oligodeoxynucleotide in monkeys

Antisense phosphorothioate oligodeoxynucleotides are therapeutic agents that provide target specificity resulting from Watson-Crick base pairing. However, there are nonspecific effects that in some instances result in toxicity. These compounds accumulate in the kidney and induce renal proximal tubular degeneration at high doses. The relationship between accumulation of phosphorothioate oligodeoxynucleotides in the kidney, indicators of renal toxicity, and histomorphology were investigated in rhesus monkeys. Monkeys received vehicle or an escalating dose regimen of 3, 10, 40, and 80 mg/kg of ISIS 2105 and were then evaluated for changes in clinical pathology indices, urinalysis parameters, and renal histopathology. Urinalysis revealed an increase in protein levels and a slight increase in blood content following the third 40 mg/kg dose and continuing through the 80 mg/kg doses, whereas other urinary markers of renal toxicity were unchanged. Creatinine clearance was slightly decreased in monkeys during the 80 mg/kg dose cycle. Granulation in the cytoplasm of proximal tubular epithelial cells was evident by microscopic examination of kidney and was present at all doses examined and increased with dose. Immunohistochemical staining localized the oligodeoxynucleotide within these granules. Histopathologic changes consisting of minimal to moderate tubular degeneration were present only at the higher doses of 40 and 80 mg/kg and at high tissue concentrations, and these changes occurred concurrent with functional alterations, whereas lower doses (< or = 10 mg/kg) did not affect a pathologic or functional change.

Synthetic oligonucleotides: the development of antisense therapeutics

Antisense therapeutics using synthetic oligodeoxynucleotides (ODNs) are currently being evaluated in clinical trials for cancer, inflammation, and viral diseases. These macromolecules afford a unique opportunity to treat disease at the molecular level. The specificity of these compounds is derived from the genetic code and Watson-Crick base pairing, utilizing an antisense paradigm for the inhibition of translation and the regulation of protein expression. Currently, most antisense ODNs in development contain a phosphorothioate (P=S) backbone. Additional modifications primarily involve the 2' position on the ribose or modification of the nucleotide linkages of the backbone. To date, no toxicities in animal models appear related to inhibition of the pharmacologic target, rather toxicities induced by P=S ODNs appear similar and are independent of pharmacologic target. In general, toxicities correlate well with pharmacokinetic or tissue distribution parameters. In primates, the primary acute effects are associated with complement activation and the systemic effects associated with accumulation of high concentrations of P=S ODNs in the kidneys. In rodents, the primary effect is an immune stimulation characterized by splenomegaly, lymphoid hyperplasia, and mononuclear cell infiltrates in multiple tissues. At extraordinarily high doses (15-50 times the targeted clinical doses), hepatocellular and renal tubular degeneration are evident in rodents. Second generation antisense compounds, new routes of administration, and new formulations appear to broaden and improve the application of antisense technology.

Correlation of toxicity and pharmacokinetic properties of a phosphorothioate oligonucleotide designed to inhibit ICAM-1

ISIS 2302 is a phosphorothioate oligodeoxynucleotide with a sequence complementary to the mRNA of human intercellular adhesion molecule 1 (ICAM-1). Hybridization of ISIS 2302 to the mRNA inhibits expression of the ICAM-1 protein in response to inflammatory stimuli. A murine active antisense oligonucleotide, ISIS 3082, has been used for in vivo pharmacology studies and has anti-inflammatory activity in models of organ transplant rejection, ulcerative colitis, and collagen-induced arthritis at doses ranging from 0.03 to 5 mg/kg. The safety assessment for ISIS 2302 includes general toxicity studies up to 6 mo in duration in mice and monkeys, genetic toxicity studies, and reproductive/fertility studies. ISIS 3082 was examined in parallel with ISIS 2302 in mouse toxicity and reproductive studies. The toxicities observed following systemic administration of ISIS 2302 and ISIS 3082 were similar and consistent with those observed for other compounds in this chemical class and, therefore, are independent of the suppression of ICAM-1 expression. Toxicokinetic evaluation demonstrated that toxicities occurred in organs containing the highest concentrations of ISIS 2302. Evidence of immune stimulation. including dose-dependent splenomegaly, lymphoid hyperplasia, and multiorgan mixed mononuclear cell infiltrates, was the most common finding in rodent studies. Monkeys were much less sensitive than mice to immune stimulation. Kidney contained the highest concentrations of ISIS 2302. Morphologic changes observed in kidney included atrophic and regenerative changes in proximal tubular epithelium; however, there was no evidence of functional abnormalities. Additional histologic changes noted in proximal tubular epithelium included basophilic granules, which were reflective of oligonucleotide distribution and uptake in these cells. Liver also contained high concentrations of oligonucleotide, which were associated with Kupffer cell hypertrophy in mice. Changes in serum transaminases, cholesterol, and triglycerides were reflective of hepatic alterations. In monkeys, high concentrations of oligonucleotide caused a transient increase in clotting times and activation of the alternative complement pathway. All toxicities associated with ISIS 2302 were reversible and occurred at doses well above those required for pharmacologic activity or currently used in clinical trials. In addition, there has been no evidence of genetic toxicity associated with ISIS 2302, and no changes in reproductive performance, fertility, or fetal development have been noted in animals treated with ISIS 2302 or ISIS 3082.

PAAn-1b and PAAn-E: two phosphorothioate antisense oligodeoxynucleotides inhibit human aromatase gene expression

Estrogen-dependent diseases, especially breast cancers, are frequently treated with aromatase inhibitors. Another more recent strategy is the antisense technology. In this study, after predicting aromatase mRNA secondary structure, we describe the design, the efficiency, and the toxicity of two antisense phosphorothioate oligodeoxynucleotides (PAAn-1b and PAAn-E) directed toward aromatase mRNA. Indeed, 2 microM PAAn-1b and PAAn-E encapsulated with 54 microM polyethylenimine inhibit aromatase activity by 71 and 79%, respectively, in transfected 293 cells, with IC50 values of 0.2 and 0.6 microM. The mechanism of inhibition appears to be specific after using sense and scramble oligodeoxynucleotides as controls and largely decreases aromatase mRNA and protein amounts. Moreover, PAAn-1b and PAAn-E are not cytotoxic for 293 cells. This study finally provides a new strategy for aromatase inhibition. It offers new tools for studying aromatase gene expression and its role in cancer for instance, and this could be of help for the therapy of estrogen-dependent diseases.

Preclinical evaluation of the effects of a novel antisense compound targeting C-raf kinase in mice and monkeys

CGP 69846A (ISIS 5132) is an antisense phosphorothioate oligodeoxynucleotide which targets human C-raf kinase and is currently being developed as an antineoplastic agent. The toxicity of this compound was evaluated in mice and monkeys following repeated i.v. injections or infusions for 4 weeks at doses up to 100 mg/kg. Because CGP 69846A is inactive in the mouse, ISIS 11061, the murine-specific homologue targeting C-raf kinase mRNA was evaluated concurrently with CGP 69846A to assess the potential toxicity associated with reduced C-raf expression. There were no toxicities that differentiated ISIS 11061 from CGP 69846A in mice. Effects in mice included hepatomegaly and hepatocellular degeneration at the high dose of 100 mg/kg CGP 69846A that potentially resulted in lethality. Other effects which were observed at 20 and 100 mg/kg included mononuclear cell infiltrates in multiple organs, extramedullary hematopoiesis in the spleen and liver, an increase in bone marrow cellularity, an increase in white blood cells, a decrease in platelet counts, and Kupffer cell hyperplasia. These alterations were reversible following a recovery period. No adverse effects in mice were observed with doses < or = 10 mg/kg. In monkeys, administration of 10 mg/kg of CGP 69846A was associated with effects observed with other P = S ODNs, namely, prolongation of activated partial thromboplastin time (APTT) and activation of complement. These effects were transient and correlated with plasma concentrations of CGP 69846A. Below a concentration of 35 micrograms/ml of intact CGP 69846A the prolongation of APTT was less than 50% and levels of complement split products were not increased. All monkeys tolerated complement activation with no evidence of treatment-related clinical signs. Complement and coagulation were not affected by the lower doses of 1 and 3 mg/kg. No histopathology or alteration in hematology or serum chemistry was induced by doses up to 10 mg/kg in monkeys. The plasma and tissue deposition of CGP 69846A were characterized in mice and monkeys and toxicity was dependent on dose of CGP 69846A. In the present preclinical evaluation of toxicity in mice and monkeys, CGP 69846A is well tolerated at doses targeted for clinical trials. Toxicities induced by CGP 69846A in monkeys and mice occurred at doses of 10 mg/kg and greater. Effects induced by CGP 69846A were not unique and have been observed previously with other phosphorothioate oligodeoxynucleotides.

Antisense c-myc and immunostimulatory oligonucleotide inhibition of tumorigenesis in a murine B-cell lymphoma transplant model

BACKGROUND

Because the development of drug-resistant cells can lead to relapses in patients with lymphoma treated with chemotherapy, new approaches are needed for effective disease management, such as those targeting the c-MYC proto-oncogene with antisense oligonucleotides. Our goal was to investigate whether antisense c-myc oligonucleotides could prevent tumorigenesis in a B-cell lymphoma model.

METHODS

Immunocompetent mice received subcutaneous injections of tumor cells from a transgenic mouse model of Burkitt's lymphoma. For 7 consecutive days, beginning 1 day after tumor cell transplantation, the mice were given either a DNA phosphorothioate oligonucleotide complementary to c-myc codons 1-5 (myc6) or other c-myc-related oligonucleotides at a dose of 0.76 mg per day subcutaneously. Myc protein expression, normalized to beta-actin expression, was measured by western blotting of tumor and splenic proteins. To determine whether tumor inhibition by myc6 could be a result of B-cell activation, we compared the activity of myc6 with that of an immunostimulatory oligonucleotide, mcg.

RESULTS

In comparison with control treatments (saline vehicle, scrambled-sequence oligonucleotide, or double-mismatch oligonucleotide), treatment with myc6 delayed tumor onset by 3 days, decreased total tumor mass at sacrifice (i.e., 17 days after tumor cell transplantation) by 40% +/- 16% (mean +/- standard error), and decreased the splenic Myc-to-actin ratio. Inhibition of tumors by myc6 and mcg (both of which share a dACGTT motif) was comparable. Administration of an oligonucleotide sequence complementary to c-myc codons 384-388 (myc55) delayed tumor onset by 5-6 days, decreased total tumor mass at sacrifice by 65% +/- 6%, and reduced the splenic Myc-to-actin ratio to below that produced by myc6. A 14-day treatment regimen of myc55 alternating with mcg completely inhibited tumor formation during the therapeutic schedule.

CONCLUSIONS

A combined oligonucleotide regimen, based on antisense c-MYC and immunostimulatory oligonucleotides, should be investigated to increase the number and duration of complete remissions obtained after standard chemotherapy for B-cell lymphoma.

Antisense therapeutics

The field of antisense therapeutics has attracted great interest during the past decade. A large body of literature has recently appeared in which the antisense mechanism is claimed to be involved and a number of human clinical trials are underway. Questions regarding the specificity of action and side effects of antisense phosphorothioate oligonucleotides have arisen simultaneously.

Synergistic inhibition of HIV-1 by an antisense oligonucleotide and nucleoside analog reverse transcriptase inhibitors

We have studied the effects of the gag antisense phosphorothioate oligonucleotide GEM 91 and mismatch antisense controls on the antiviral activities of ddC and other nucleoside analogs in HIV-infected MT-4 cells using a cytoprotection based assay. Under standard assay conditions, i.e. simultaneous incubation of drugs, HIV-1 IIIB and MT-4 cells, both GEM 91 and mismatch controls interacted synergistically with ddC resulting in an approximate 40-fold decrease in the IC50 value of ddC; this suggests a potent but sequence non-specific effect of GEM 91. Under post-adsorption assay conditions, i.e. pre-incubation of virus and cells and removal of excess HIV before drug addition, GEM 91 exhibited synergism with ddC, with an approximate 5-fold decrease in ddC IC50 value. This favorable interaction was not seen with any of the mismatch oligonucleotides, suggesting the involvement of a sequence-specific mechanism of action. Similar results were seen with the thymidine analogs AZT and d4T in combination with GEM 91. These data suggest a potential role for GEM 91 and future sequence-specific antisense drugs in combination with nucleoside analogs for the treatment of HIV infection. It is essential that potential interactions between new and existing classes of anti-HIV drugs are studied extensively as antiretroviral drug combinations become increasingly more complex.

Toxicologic effects of an oligodeoxynucleotide phosphorothioate and its analogs following intravenous administration in rats

The aim of the present study is to evaluate the in vivo toxicologic effects of a phosphorothioate oligodeoxynucleotide (PS oligo) and three of its analogs [PS oligo containing four methylphosphonate linkages at the 3' and 5'-ends (MBO 1), PS oligo containing four 2'-O-methylribonucleosides at both the 3'- and 5'-ends (MBO 2), and PS oligo containing an 8 bp loop region at the 3'-end (self-stabilized oligo)]. Oligodeoxynucleotides were administrated intravenously to male and female rats at doses of 3, 10, and 30 mg/kg/day for 14 days. Rats were killed on day 15, blood samples were collected for hematology and clinical chemistry determinations, and tissues, including lymph nodes, spleens, livers, and kidneys, were subjected to pathologic examinations. The toxicity profiles of the four oligodeoxynucleotides were very similar, but differed in magnitude. In terms of the severity of the abnormalities caused by the oligodeoxynucleotides, the order was MBO 2 > PS oligo > self-stabilized oligo > MBO 1. Alterations in hematology parameters included thrombocytopenia, anemia, and neutropenia. Abnormalities in clinical chemistry parameters observed with PS oligo or MBO 2 were dose-dependent elevation of liver transaminases and reduction of the levels of alkaline phosphatase, albumin, and total protein. In addition, MBO 2 caused elevation of the total bilirubin level in male rats at the 30 mg/kg dose. No major alterations in hematology or clinical chemistry were observed in rats receiving MBO 1 or self-stabilized oligo. Dose-dependent enlargements of spleen, liver, and kidney were observed, especially in rats receiving PS oligo and MBO 2. Pathologic studies showed a generalized hyperplasia of the reticuloendothelial (RE) system in the tissues examined. Alterations in the spleen were mainly RE cell hyperplasia and hematopoietic cell proliferation. In addition to RE cell hyperplasia, lymph nodes showed necrosis, hepatocytes showed cytologic alterations and necrosis, and kidneys showed renal tubule regeneration. The severity of pathologic changes observed was oligodeoxynucleotide dependent, in the order of MBO 2 > PS oligo > self-stabilized oligo > MBO 1.

Pharmacokinetics and metabolism in mice of a phosphorothioate oligonucleotide antisense inhibitor of C-raf-1 kinase expression

The plasma and tissue disposition of CGP 69846A (ISIS 5132) was characterized in male CD-1 mice following iv bolus injections administered every other day for 28 days (total of 15 doses). The doses ranged from 0.8 mg/kg to 100 mg/kg. Urinary excretion of oligonucleotide was also monitored over a 24-hr period following single dose administration over the same dose range. Pharmacokinetic plasma profiles were determined following single dose administration (dose 1) and after multiple doses (dose 15) at doses of 4 and 20 mg/kg. Concentrations in kidney, liver, spleen, heart, lung, and lymph nodes were characterized following doses 1, 8, and 15 for all doses. Capillary gel electrophoresis was used to quantitate intact (full-length) oligonucleotide and its metabolites (down to N - 11 base deletions) in both plasma and tissue at all time points. The plasma and tissue disposition of CGP 69846A was characterized by a rapid distribution into all tissues analyzed. Rapid plasma clearance of the parent oligonucleotide (9.3-14.3 ml/min/kg) was predominantly the result of distribution to tissue and, to a lesser extent, metabolism. Appearance and pattern of chain-shortened metabolites seen in plasma and tissue were consistent with predominantly exonuclease-mediated base deletion. No measurable accumulation of oligonucleotide was observed in plasma following multiple-dose administration, but both the liver and the kidney exhibited 2-3-fold accumulations. In general, the tissues exhibited half-lives for the elimination of parent oligonucleotide of 16-60 hr compared with plasma half-lives of 30-45 min. After repeated administrations, significant decreases in plasma clearance and volume of distribution at steady state (Vss) were observed following dose 15 at the dose of 20 mg/kg but not at the dose of 4 mg/kg. Changes in tissue accumulation and evidence for saturation of tissue distribution at the high doses may explain the plasma disposition changes observed in the absence of alteration of metabolism or plasma accumulation. Urinary excretion was a minor pathway for elimination of oligonucleotide over the 24-hr period immediately following iv administration. However, the amount of oligonucleotide excreted in the urine increased as a function of dose from less than 1% to approximately 13% of the administered dose over a dose range of 0.8 mg/kg to 100 mg/kg.

Evaluation of the toxicity of ISIS 2302, a phosphorothioate oligonucleotide, in a 4-week study in CD-1 mice

The subchronic toxicity of ISIS 2302 and ISIS 3082, phosphorothioate oligonucleotides with antisense activity against human and murine ICAM-1 mRNA, respectively, was investigated in CD-1 mice. ISIS 2302 is currently in clinical trials as an anti-inflammatory agent. Because of the differences in mRNA sequence targets between humans and mice, ISIS 2302 has no pharmacologic activity in mice. ISIS 3082 was specifically designed to inhibit murine ICAM-1 and was included in this study to evaluate the effects of prolonged ICAM-1 inhibition. The oligonucleotides were administered by bolus i.v. injection (via tail vein) every other day for 27 days (14 doses) at dose levels of 0, 0.8, 4, 20, and 100 mg/kg per injection ISIS 2302 or 20 mg/kg per injection ISIS 3082. The basic group size consisted of 10 male and 10 female mice, which were sacrificed 2 days after the last dose and an additional 5 mice per sex in vehicle control and 100 mg/kg ISIS 2302 dose groups, which remained on study for a 28-day treatment-free period. No treatment-related deaths occurred during this study, and there were no effects of either oligonucleotide on body weight gain or food consumption. The most common changes observed in this study included a mixed mononuclear cell infiltrate seen in a number of organs or tissues, splenomegaly, and lymphoid hyperplasia at dose levels of > or = 20 mg/kg ISIS 2302. In the group that received the highest dose level of ISIS 2302 (100 mg/kg), there were alterations in serum chemistry parameters that appeared to be related to perturbations in the liver, including 3- to 4-fold increases in aspartate and alanine aminotransferase and smaller changes in bilirubin, alkaline phosphatase, cholesterol, triglycerides, and albumin levels. Treatment-related effects on hematologic parameters were limited to the 100 mg/kg ISIS 2302 dose group and included slight monocytosis and thrombocytopenia. None of the effects observed appeared to be life threatening. Complete or partial reversal of all effects was evident in the remaining high-dose ISIS 2302 animals at the end of the 4-week recovery period. Comparison of the effects produced by the same dose level (20 mg/kg) of ISIS 2302 and ISIS 3082 did not reveal any differences that could be attributed to exaggerated pharmacology. In conclusion, treatment-related alterations were observed primarily at the 100 mg/kg dose level, including immune stimulation and hepatic alterations, which were partially reversed following a 4-week treatment-free period.

Evaluation of the toxicity of ISIS 2302, a phosphorothioate oligonucleotide, in a four-week study in cynomolgus monkeys

The toxicity of ISIS 2302, a phosphorothioate oligonucleotide with antisense activity against human ICAM-1 mRNA, was investigated in cynomolgus monkeys (young adult). The oligonucleotide was administered by slow bolus injection every other day for 28 days (14 doses) at dose levels of 0, 2, 10, and 50 mg/kg/injection. The basic group size consisted of three male and three female monkeys which were sacrificed 2 days after the last dose. An additional 2 monkeys/sex in the vehicle control and 50 mg/kg dose groups remained on study for a 28-day treatment-free period. No treatment-related deaths occurred during this study, however, one monkey in the 10 mg/kg dose group was markedly lethargic after the first dose. Other clinical observations included periocular swelling (> or = 10 mg/kg) on the first day of the study, and bruising in all dose groups throughout the study. Bruising was associated with a dose-dependent prolongation of clotting times, particularly activated partial thromboplastin times (APTT), that was transient in nature. Bruises occurred around site of intravenous dosing or blood collection, and were manifested as subcutaneous hemorrhages upon microscopic evaluation. There were no corresponding alterations in hematology parameters including RBC or platelet counts. Other treatment-related microscopic alterations noted were intracytoplasmic eosinophilic granules and vacuolation in proximal tubular epithelial cells at 10 and 50 mg/kg, with free RBC in renal proximal tubular lumens at 50 mg/kg. Serum chemistry parameters including BUN and creatinine levels were normal in all dose groups and there were no notable alterations in urinalysis parameters. Granules and vacuolations in kidneys were reversed following a 4-week treatment free period. In general, 10 and 50 mg/kg ISIS 2302 produced dose-dependent changes in clotting times and the kidney that were reversible, while 2 mg/kg ISIS 2302 produced no remarkable alterations.

Evaluation of retinal toxicity and efficacy of anti-cytomegalovirus and anti-herpes simplex virus antiviral phosphorothioate oligonucleotides ISIS 2922 and ISIS 4015

Retinal toxicity of ISIS 2922 and ISIS 4015, phosphorothioate oligonucleotides complementary to human cytomegalovirus (CMV) and herpes simplex virus (HSV) RNA, were evaluated. The intravitreal concentration of ISIS 2922 found not to cause permanent toxic changes in the rabbit retina was 10 microM and in the pig retina, 5 microM. The 3 microM concentration was associated with a transient inflammatory response, and 1 microM caused no retinal toxicity or inflammation. ISIS 4015 showed very mild toxicity with no permanent retinal changes and very mild inflammation at doses of 10 microM; this dose was effective in ameliorating or preventing HSV-1 retinitis when injected 1 day and 1 week prior to virus inoculation. These oligonucleotides have a low intraocular therapeutic index. Attempts to improve the therapeutic index of these compounds are indicated. Only a clinical trial can determine the toxicity profile of ISIS 2922 for the treatment of CMV retinitis.

Comparison of the toxicity profiles of ISIS 1082 and ISIS 2105, phosphorothioate oligonucleotides, following subacute intradermal administration in Sprague-Dawley rats

The systemic toxicity of two phosphorothioate oligonucleotides specific for herpes simplex viruses (ISIS 1082) and human papiloma virus (ISIS 2105) were evaluated following repeated intradermal injections of vehicle control, 0.33, 2.17, or 21.7 mg/kg daily to Sprague-Dawley rats (10/sex/group) for 14 days. Animals were sacrificed 1 day after the last dose, except for a portion of the ISIS 1082-treated animals (5/sex/group) which were maintained for an additional 14-day recovery period. The profile of alterations noted for both compounds was very similar. Other than local signs of irritation at the site of injection, there were no clinical signs of toxicity or treatment-related mortality, but there was a slight decrease in body weight gain for the 21.7 mg/kg dose groups. Alterations in hematology parameters included dose-dependent thrombocytopenia and anemia. Alterations in serum chemistry parameters were suggestive of mild alterations in hepatic metabolism, with increases in liver transaminases and bilirubin, along with decreases in albumin and cholesterol. Both spleen and liver weights were significantly elevated in a dose-dependent fashion. Histopathological alterations noted in liver, kidney, lung, injection site skin, and spleen were characterized as perivascular and interstitial infiltrates of macrophages and monocytes. Additional microscopic alterations in the spleen included mild lymphoid hyperplasia (seen in lymph nodes as well), and extramedullary hematopoiesis. Treatment-related cytopenias were likely related to mild, focal hypocellularity in the bone marrow. Alterations in ISIS 1082-treated animals were only partially reversed following the 14-day treatment-free period. In conclusion, repeated intradermal administration of ISIS 1082 and ISIS 2105 produced a similar spectrum of toxicities, with liver, kidney, spleen, and bone marrow being identified as target tissues.

Toxicological properties of several novel oligonucleotide analogs in mice

The toxicological properties of ISIS 3082, a phosphorothioate oligonucleotide, and five structurally related analogs of ISIS 3082, were examined in Balb/c mice. Comparisons were made between the uniform phosphorothioate oligonucleotide (ISIS 3082), and a 2' propoxy modified phosphodiester (ISIS 9044), a 2' propoxy phosphorothioate (ISIS 9045), a chimeric oligonucleotide comprised of 2' propoxy diester wings and phosphorothioate deoxy center (ISIS 9046), a 5' C18 amine phosphorothioate (ISIS 9047), or a 5' cholesterol modified phosphorothioate (ISIS 8005) oligonucleotide. Oligonucleotides were administered at 50 mg/kg by i.v. bolus injection (tail vein) every other day for 14 days. In general, the spectrum of alterations observed for ISIS 3082 and all of the analogs were relatively similar. Balb/c mice treated with ISIS 3082 were observed to have increases in liver transaminases and a decrease in triglycerides consistent with results from previous studies performed in CD-1 mice. Spleen weights were also increased in ISIS 3082-treated mice, but no histopathological alterations were noted. ISIS 9046 resulted in a toxicity profile that was very similar to that described for ISIS 3082 with the exception of a slightly lower cholesterol level. Alterations induced by ISIS 9045, ISIS 9047 and ISIS 8005 were qualitatively similar to ISIS 3082, but in general more pronounced, with greater reductions in cholesterol and platelet counts, or increases in blood urea nitrogen relative to ISIS 3082. Red blood cell (RBC) counts and hematocrit were also reduced in mice treated with ISIS 9046, ISIS 9047 and ISIS 8005 relative to the ISIS 3082 treatment group. Kupffer cell hypertrophy and basophilic inclusions in Kupffer cells were observed in mice treated with ISIS 9045, ISIS 9047 and ISIS 8005, but not in ISIS 3082-treated mice. A unique renal lesions was noted in mice treated with ISIS 9044 only that was characterized as mild atrophy of proximal convoluted tubules associated with interstitial fibrosis. With the exception of the renal lesions observed in ISIS 9044 treated mice, the toxicity profiles of various oligonucleotide analogs examined in this study were similar to that observed for ISIS 3082.

Inhibition of growth of human tumor cell lines in nude mice by an antisense of oligonucleotide inhibitor of protein kinase C-alpha expression

A 20-mer phosphorothioate oligodeoxynucleotide (ISIS 3521) designed to hybridize sequences in the 3'-untranslated region of human protein kinase C-alpha (PKC-alpha) mRNA has been shown to inhibit the expression of PKC-alpha in multiple human cell lines. In human bladder carcinoma (T-24) cells, inhibition of PKC-alpha was both concentration dependent and oligonucleotide sequence specific. ISIS 3521 had a IC50 of 50-100 nM for PKC-alpha mRNA reduction and was without effect on the expression of other members of the PKC family of genes (PKC-eta and zeta). Toxicity studies in mice revealed that the oligodeoxynucleotide was well tolerated at repeat doses of 100 mg/kg i.v. for up to 14 days, with no acute toxicity apparent. The oligodeoxynucleotide was found to also inhibit the growth of three different human tumor cell lines, the T-24 bladder, human lung carcinoma (A549), and Colo 205 colon carcinoma grown in nude mice. The inhibition was dose dependent with ID50 values for the growth inhibition between 0.06 and 0.6 mg/kg daily when given i.v., depending on the cell line examined. Three control phosphorothioate oligodeoxynucleotides not targeting human PKC-alpha were without effect on the growth of the tumors at doses as high as 6 mg/kg. Recovery of ISIS 3521 from tumor tissue and resolution by capillary gel electrophoresis revealed that 24 It after the final dose of oligodeoxynucleotide, intact, full-length 20-mer material was present as well as some apparent exonuclease degradation products (e.g., n-1 and n-2 mers). These studies demonstrate the in vivo antitumor effects of an antisense oligodeoxynucleotide targeting PKC-alpha and suggest that this compound may be of value as a chemotherapeutic agent in the treatment of human cancers.

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.