Nusinersen: antisense oligonucleotide to increase SMN protein production in spinal muscular atrophy.

Patients with spinal muscular atrophy (SMA) have an autosomal recessive disease that limits their ability to produce survival motor neuron (SMN) protein in the CNS resulting in progressive wasting of voluntary muscles. Detailed studies over several years have demonstrated that phosphorothioate and 2'-O-methoxyethyl- modified antisense oligonucleotides (ASOs) targeting the ISS-N1 site increase SMN2 exon 7 inclusion, thus increasing levels of SMN protein in a dose- and time-dependent manner in liver, kidney and skeletal muscle, and CNS tissues only when administered intrathecally. On a dose basis, nusinersen was found to be the most potent ASO for SMN2 splicing correction in the CNS of adult mice. After nusinersen was found to increase levels of SMN protein in the CNS of mice and subhuman primates without causing significant adverse events, it was advanced into clinical studies in patients with SMA. These trials in SMA patients have demonstrated significant improvements in various measures of motor function and in progression to movement developments not normally seen in SMA patients. In addition, there have been significant extensions in life expectancy. These findings led to the U.S. and European approval of nusinersen for use in SMA patients of all ages.

A novel inhibitor of active protein kinase G attenuates chronic inflammatory and osteoarthritic pain.

Activating PKG-1α induces a long-term hyperexcitability (LTH) in nociceptive neurons. Since the LTH correlates directly with chronic pain in many animal models, we tested the hypothesis that inhibiting PKG-1α would attenuate LTH-mediated pain. We first synthesized and characterized compound N46 (N-((3R,4R)-4-(4-(2-fluoro-3-methoxy-6-propoxybenzoyl)benzamido)pyrrolidin-3-yl)-1H-indazole-5-carboxamide). N46 inhibits PKG-1α with an IC50 of 7.5 nmol, was highly selective when tested against a panel of 274 kinases, and tissue distribution studies indicate that it does not enter the CNS. To evaluate its antinociceptive potential, we used 2 animal models in which the pain involves both activated PKG-1α and LTH. Injecting complete Freund's adjuvant (CFA) into the rat hind paw causes a thermal hyperalgesia that was significantly attenuated 24 hours after a single intravenous injection of N46. Next, we used a rat model of osteoarthritic knee joint pain and found that a single intra-articular injection of N46 alleviated the pain 14 days after the pain was established and the relief lasted for 7 days. Thermal hyperalgesia and osteoarthritic pain are also associated with the activation of the capsaicin-activated transient receptor protein vanilloid-1 (TRPV1) channel. We show that capsaicin activates PKG-1α in nerves and that a subcutaneous delivery of N46 attenuated the mechanical and thermal hypersensitivity elicited by exposure to capsaicin. Thus, PKG-1α appears to be downstream of the transient receptor protein vanilloid-1. Our studies provide proof of concept in animal models that a PKG-1α antagonist has a powerful antinociceptive effect on persistent, already existing inflammatory pain. They further suggest that N46 is a valid chemotype for the further development of such antagonists.

Pharmacokinetic evaluation of oblimersen sodium for the treatment of chronic lymphocytic leukemia.

INTRODUCTION: Chronic lymphocytic leukemia (CLL) is the most common form of leukemia in the western hemisphere. Developing new therapies remains a priority as present treatment options do not offer a cure. BCL-2 overexpression in CLL is associated with aggressive disease features and resists chemotherapy. Oblimersen sodium (G3139) is a phosphorothioate oligonucleotide antisense drug targeting the BCL-2 mRNA and is the first antisense to reach advanced clinical testing in oncology. Preclinical evaluation has demonstrated good antineoplastic effect in B-cell cancers; several clinical trials have confirmed its safety and efficacy both alone and in combination with other therapeutics. AREAS COVERED: This review focuses on the chemistry, pharmacodynamics, pharmacokinetics and clinical evaluation of oblimersen in CLL. PubMed and MEDLINE searches assisted in data collection. EXPERT OPINION: Bcl-2 is an important target in CLL. Antisense therapy is a novel approach to target oncoproteins; this can be beneficial in the clinical setting. Oblimersen sodium demonstrates the clinical safety of the antisense therapeutic approach and, with chemotherapy, shows survival advantage in a subset of CLL patients. However, future approval of oblimersen sodium in CLL remains uncertain. Nevertheless, BCL-2 remains a critical target in drug development and is an area of high-priority research.

Trabedersen, a TGFbeta2-specific antisense oligonucleotide for the treatment of malignant gliomas and other tumors overexpressing TGFbeta2.

Trabedersen (AP-12009), which is being developed by Antisense Pharma GmbH, is a synthetic antisense oligodeoxynucleotide designed to block the production of TGFbeta2, a secreted protein that can exert protumor effects. Trabedersen is indicated for the treatment of malignant brain tumors and other solid tumors overexpressing TGFbeta2, such as those of the skin, pancreas and colon. Preclinical studies demonstrated that trabedersen reduced the secretion of TGFbeta2 in cultured tumor cells and exhibited antitumor activity ex vivo. It was also demonstrated that chronic intracerebral or intravascular administration of trabedersen did not cause life-threatening side effects in animals. This observation was confirmed in early clinical trials in patients with advanced cancer. In a phase IIb trial, improved survival was observed in patients with brain tumors who were intratumorally administered trabedersen, compared with patients receiving standard chemotherapy. However, this observation requires validation by an ongoing large-scale, phase III, randomized, controlled trial. Meanwhile, continued research on trabedersen should help to determine the roles of TGFbeta2 in cancer and also further the development of antisense technology.

[AIDS: ethics and scientific investigation on human beings]. / Sida: éthique et investigation scientifique sur l'être humain.

The experimentation on human beings of one or several therapeutic molecules discovered in laboratory is necessary and important because it helps to find new treatments or new diagnostic methods. But, it presents serious ethical problems. In this article we are analysing the example of the HIV infection. We are succinctly describing the research methods in laboratory for therapeutic molecules, first the experimentation on animals and then on human being in clinical trials. We will then try to show, with several examples, how during these last 25 years of HIV infection, the research of new molecules has not always respected the ethical rules set out in Helsinki declaration, "Code de la santé publique" or "Guide de bonnes pratiques cliniques-ICH" etc. We are discussing here the way to avoid these irregularities.

[Promising new treatment options for metastatic androgen-independent prostate cancer]. / Novedades en el tratamiento del cáncer de próstata metastático hormono-independiente.

OBJECTIVE: Review the recent advances in the treatment of androgen independent prostate cancer (AIPC). METHODS: Review recent abstracts and literature utilizing Medline/PubMed using key words: androgen independent/hormone refractory prostate cancer, novel treatment options, Phase II, III trials and meeting abstracts/presentations. CONCLUSION: Two pivotal trials SWOG (Southwest Oncology Group) study 9916 and Taxotere 327 have shown that survival can be improved in this population by administration of chemotherapy with docetaxel every three weeks intravenously. An overall survival of 19 months could be achieved with docetaxel/prednisone compared to 16 months with mitoxantrone/prednisone. Despite this, there is a need to improve on this survival benefit because the relapse free survival among responders is often short (6 months) and patients often would have progression of their cancer leading to death. Satraplatin, a novel platinum analogue had been found to provide an additional 1.5 week progression free survival benefit in this population in the second line setting. There is however, a need to develop less toxic drugs that would improve survival significantly.

Safety of biologic therapy.

Several biologic agents have been assessed in patients with inflammatory bowel disease (IBD; Crohn's disease [CD] and ulcerative colitis [UC]). Until recently, only infliximab (humanized monoclonal anti-TNF-alpha antibody) had been approved by the Food and Drug Administration (FDA) to induce and maintain remission in patients with active mild to moderate and/or fistulizing Crohn's disease who are refractory to conventional therapy. Two recent trials, ACT 1 and ACT2, observed high efficacy of infliximab in inducing and maintaining clinical remission, mucosal healing, and corticosteroid-sparing effects in patients with moderate to severe UC. This agent also was recently approved by the FDA for the treatment of ulcerative colitis to reduce signs and symptoms, to induce clinical remission and healing of the intestinal mucosa, and to eliminate the use of corticosteroids in patients with moderately to severely active UC who have had an inadequate response to conventional therapy. There have been many randomized, double-blind, controlled and open-label uncontrolled studies of large and small numbers of patients assessing the efficacy and safety of various biologic agents considered potentially useful in the treatment of IBD. Among all the biologic agents, infliximab has the most robust data on safety. This is because it has been evaluated in many more trials than has any other biologic agent. In addition, postmarketing experience provides very valuable information about adverse events occurring during treatment with this agent.

Selection of thioaptamers for diagnostics and therapeutics.

Thioaptamers offer advantages over normal phosphate ester backbone aptamers due to their enhanced affinity, specificity, and higher stability, largely due to the properties of the sulfur backbone modifications. Over the past several years, in vitro thioaptamer selection and bead-based thioaptamer selection techniques have been developed in our laboratory. Furthermore, several thioaptamers targeting specific proteins such as transcription factor NF-kappaB and AP-1 proteins have been identified. Selected thioaptamers have been shown diagnostic promise in proteome screens. Moreover, some promising thioaptamers have been shown in preliminary animal therapeutic dosing to increase survival in animal models of infection with West Nile virus.

Emerging drugs for chronic lymphocytic leukaemia.

Although the philosophy of management of patients with chronic lymphocytic leukaemia (CLL) has been altered with the advent of fludarabine-based therapies, impact on long-term survival is unclear and a significant proportion of patients will develop resistance to fludarabine. Similar to other haematological malignancies, a potential for 'cure' is likely to be achieved only if 'high-quality' complete remissions (CRs) are achieved. Treatment options for patients who develop resistance to fludarabine continue to be limited, with only a proportion obtaining a response (usually not CRs) with salvage therapies. This review summarises novel therapies that are being evaluated in patients with CLL, specifically those targeting the antiapoptotic Bcl-2 family of proteins and receptors (e.g., CD40, CD80, HLA-DR) involved in mediating survival signals from the microenvironment.

Innovations in antineoplastic therapy.

Cancer is a complex group of diseases. Many of the current treatment modalities available provide limited effectiveness and significant side effects. This circumstance creates a challenge for health care providers. There is great need for the development of innovative therapies that increase efficacy and decrease morbidity. In general, chemotherapeutic agents are unable to distinguish cancer cells from normal cells. As a result of therapy, patients may develop significant myelosuppression. Patients who are undergoing chemotherapy need to be observed for signs of hematologic and nonhematologic toxicities. Patients should be advised that periodic blood tests are indicated to monitor for anemia, neutropenia, and thrombocytopenia. If myelosuppression develops, measures to prevent complications such as bleeding and infection are indicated. Strategies to combat fatigue should also be discussed. Understanding of the biology of cancer has increased significantly in recent years. As knowledge of the science grows, new therapies are developed and clinical trials are initiated to investigate feasibility and efficacy of agents. Many of these trials involve agents that target specific biologic processes of cancer. While the complexities of cancer treatment are prolonging the life expectancy of patients who have the disease, patients are presenting with increasing numbers and types of morbidities. Nurses need to be aware of the rationale for treatment, mechanism of action of the agents administered, and expected toxicities of therapies. With this knowledge, symptoms can be identified earlier, life-threatening sequela can possibly be averted, and patients and families can be educated about what to expect and how to make knowledgeable decisions about treatment options. Enhancing patients' knowledge base may also increase their adherence to challenging therapies.

Antitumor effects of radioiodinated antisense oligonuclide mediated by VIP receptor.

A 15-mer phosphorothioate antisense oligonuclide (ASON) complementary to the translation start region of the C-myc oncogene mRNA was radioiodinated to enhance its antitumor activity, and vasoactive intestinal peptide bound covalently polylysine (VIP-polylysine) was used as a carrier to deliver the oligonucleotide into VIP receptor-positive tumor cells. The antitumor activity of radioiodinated ASON conjugated to VIP-polylysine(VIP-131I-ASON) was investigated in athymic mice bearing HT29 tumor xenografts in comparison with unconjugated radioiodinated ASON(131I-ASON), unlabelled ASON (VIP-ASON) and scrambled oligonucleotide (VIP-131I-MON) conjugated to VIP-polylysine. Conjugation 125I-ASON to VIP-polylysine resulted in a 5.6-fold decrease in the plasma clearance and a 3.4-fold increase in tumor uptake of the radiopharmaceutical. Athymic mice bearing HT29 tumor xenografts were treated with 4 weekly doses of VIP-131I-ASON and the antitumor effects were assessed by use of the slope of the tumor growth curve. VIP-131I-ASON exhibited strong antitumor effects against HT29 xenografts, decreasing tumor growth rate 9.67-, 7.90-fold more effectively than 131I-ASON and VIP-ASON at equivalent doses of ASON. Conversely, 131I-ASON, VIP-ASON or VIP-131I-MON caused no significant effect compared with the normal saline. These data indicated that use of a VIP-polylysine carrier greatly increased HT29 tumor uptake of ASON and treatment with the VIP-131I-ASON complexes resulted in tumor growth delay in human colon cancer xenograft.

A randomised, controlled, double blind, escalating dose study of alicaforsen enema in active ulcerative colitis.

OBJECTIVE: To evaluate the safety and efficacy of an enema formulation of alicaforsen, an antisense inhibitor of intercellular adhesion molecule, after 1, 3, and 6 months. METHODS: This was a randomised, placebo controlled, double blind, escalating dose multicentre study in 40 patients with mild to moderately active distal ulcerative colitis (disease activity index (DAI) 4-10). Patients were assigned to four dosing cohorts of 10 patients each (eight active, two placebo). Each patient received 60 ml of alicaforsen enema (0.1, 0.5, 2, or 4 mg/ml or placebo) once daily for 28 consecutive days. Safety and efficacy (DAI and clinical activity index) scores were evaluated up to six months after initiation of dosing. RESULTS: At day 29, alicaforsen enema resulted in dose dependent improvement in DAI (overall p = 0.003). Alicaforsen 4 mg/ml improved DAI by 70% compared with the placebo response of 28% (p = 0.004). Alicaforsen 2 and 4 mg/ml improved DAI status by 72% and 68% compared with a placebo response of 11.5% at month 3 (p = 0.016 and 0.021, respectively). Specifically, DAI improved from 5.6 to 1.6 and from 6.3 to 2.5 in the 2 and 4 mg/ml groups compared with placebo (7.5 to 6.1). None of the patients in the 4 mg/ml group compared with 4/8 placebo patients required additional medical or surgical intervention over baseline during the six month period after starting the enema treatment. The safety profile was favourable. CONCLUSIONS: Alicaforsen enema showed promising acute and long term benefit in patients with mild to moderate descending ulcerative colitis. Alicaforsen enemas had a favourable safety profile. These findings require verification in larger randomised controlled clinical trials.

Unraveling biologic therapy for Bcl-2-expressing malignancies.

Cancer cells that express excessive levels of Bcl-2 pose a major problem in the delivery of curative therapy. Most treatments for such cancer involve chemotherapy to induce the apoptotic process. While these therapies often result in disease control for periods of time, failure to initiate apoptosis as a result of acquired resistance limits the effectiveness of treatment for many common hematopoietic and solid malignancies, and ultimately death from the malignancy still occurs. Various anti-apoptotic proteins of the Bcl-2 family that localize to the mitochondria appear to be involved in this resistance mechanism. However, recent advances in the understanding of malignant cell biology, achieved through both genomics and proteomics, have made it possible to explore novel approaches directed at re-establishing sensitivity to chemotherapy, presenting an attractive strategy for cancer treatment. In this article we discuss how this may be achieved by lowering Bcl-2 anti-apoptotic protein expression using antisense oligonucleotides or, alternatively, by functionally antagonizing Bcl-2 using ligands of the mitochondrial benzodiazepine receptor.

[Proapoptotic therapy with oblimersen (bcl-2 antisense oligonucleotide)--review of preclinical and clinical results]. / Proapoptotische Therapie mit Oblimersen (bcl-2-Antisense-Oligonukleotid)--Ubersicht über präklinische und klinische Daten.

The regulation of apoptosis is an important potential target for anticancer therapy. The mitochondrial Bcl-2 protein inhibits apoptosis and is therefore an important mediator of resistance to treatment with traditional cytotoxic chemotherapy, radiotherapy and monoclonal antibody therapy. Oblimersen (Genasense, Aventis Pharmaceuticals / Genta Inc) is a 18mer antisense-oligonucleotide (ASO), which specifically binds to the first 6 codons of the human bcl-2 mRNA, resulting in degradation and destruction of the mRNA by RNAse H. Subsequently there is a significant decrease of bcl-2 translation. A growing number of preclinical and clinical studies suggests that the combination of cytotoxic therapy with Oblimersen results in synergistic anticancer efficacy in many hematologic and solid tumors. Due to its low toxicity profile, oblimersen is an ideal combination partner with conventional chemotherapy. Three randomized phase-III trials (malignant melanoma, chronic lymphocytic leukemia, multiple myeloma) have recently finished recruitment. The results of these studies will be available by the end of 2003. Based on preclinical data, a lot of nonrandomized phase-II studies on several different tumor types like AML, CML, NHL, prostate cancer and breast cancer are underway. The manipulation of proapoptotic and antiapoptotic factors in favor of proapoptotic factors by inhibition of the bcl-2 protein translation in order to enhance the efficacy of anticancer treatments represents a promising new treatment concept in oncology.

Regulation of c-Raf-1: therapeutic implications.

The mitogen activated protein kinase (MAPK) or Ras/Raf/MAPK kinase (MEK)/ERK signaling cascade is a ubiquitously expressed intracellular signaling pathway that transmits mitogenic stimuli to the nucleus through a series of sequential phosphorylation events and controls such cellular functions as proliferation, differentiation, and apoptosis. Components of this pathway such as ras and raf are oncogenes and as such aberrancy in their encoded proteins results in malignant transformation. The MAPK pathway is dysregulated in approximately 30% of all human tumors and therefore targeting specific components of this pathway that regulate pleiotropic cellular processes using such strategies as isoprenylation inhibitors, antisense oligodeoxyribonucleotides, and inhibitors of the kinase function represent attractive therapeutic options. raf kinase, a downstream effector of ras, has been known to be functionally aberrant in various human tumors. The 3 isoforms of raf have been studied extensively, and agents targeting c-raf are presently undergoing early-phase clinical testing. The outcomes of these trials have wide-ranging clinical implications in the management of cancers. This review addresses the rationale for targeting raf, the diverse cellular functions regulated by c-raf, and the current status of various pharmacological approaches targeting c-raf.

Targeting intracellular signal transduction. A new paradigm for a brave new world of molecularly targeted therapeutics.

Significant advances in the field of molecular biology over the past decade have led to a new era in cancer therapeutics, with an explosion of rationally designed therapeutic strategies directed against selective molecular targets. The complex array of aberrant signal transduction proteins involved in carcinogenesis has been the focus of target-based anticancer agents. Inhibitors of intracellular signal transduction represent a unique approach in that they inhibit critical downstream regulatory proteins, which are vital to the process of cellular communication. Although these agents are in early-phase evaluations, the preliminary data suggest that they are well tolerated and capable of target inhibition in surrogate and tumor tissue. Although the primary therapeutic benefit of these agents is expected to be decreased tumor growth, evidence suggests that objective tumor responses may also be achieved. There are many unresolved questions pertaining to the development of this class of compounds, including selection of optimal dose and schedule, determination of relevant endpoints, methods for target validation, and strategies for combination with cytotoxic agents. However, despite the numerous unresolved issues, the emergence of this class of compounds has resulted in an undeniable impact on the present and future of cancer therapeutics.

In vivo inhibition of cyclooxygenase-2 by a selective phosphorothioated oligonucleotide.

Inhibition of cyclooxygenase-2 (cox-2) is considered to be anti-inflammatory, whereas inhibition of the constitutive isozyme cox-1 causes renal and gastrointestinal toxicity. Therefore, to achieve an optimal anti-inflammatory effect, an inhibitor should be cox-2 selective without inhibiting cox-1. For this purpose, 10 different cox-2-selective phosphorothioated oligonucleotides (S-oligos) were tested to inhibit the cox-2 enzyme selectively in vivo. An aqueous solution of these S-oligos (3 mg/kg body weight) was injected intraperitoneally (i.p.) into male Sprague-Dawley rats with colitis induced by trinitrobenzene sulfonic acid (TNBS). The colonic levels of cox-2 protein, mRNA, myeloperoxidase (MPO), and prostaglandin E2 (PGE2) were increased significantly on day 1 and remained significantly elevated until day 7 post-TNBS administration, whereas cox-1 remained unaltered. Two S-oligos were found to be effective in reducing the level of cox-2 protein selectively without any effect on the cox-1. The effective S-oligo, but not the mismatched control oligo, reduced the tissue levels of PGE2 and MPO activity significantly. The effective S-oligo reduced the level of cox-2 but not the cox-1 mRNA significantly, whereas a mismatched or a sense control oligo did not affect the levels of these isoforms. M-fold analysis demonstrated extensive secondary structure formation in the cox-2 mRNA. These findings demonstrate that only a few selected sites in the cox-2 target mRNA are accessible in vivo, probably because of the presence of secondary structures. Suppression of cox-2 protein, PGE2, and MPO activity by the S-oligo might prove to be an anti-inflammatory property.

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].

Therapeutic developments in cytomegalovirus retinitis.

The incidence of cytomegalovirus (CMV) retinitis in AIDS has declined significantly due to the use of highly active antiretroviral therapy (HAART). However, patients with HIV, especially those failing HAART, may still suffer with CMV retinitis, which can lead to significant loss of vision and blindness. Ganciclovir has traditionally been considered the recommended treatment for CMV retinitis; however, due to side effects and the possibility of developing viral resistance, other agents may be preferred in certain situations. Foscarnet, which has similar efficacy to ganciclovir but a different side effect profile, is more difficult to administer and is less well-tolerated. Intravenous cidofovir, which may be more effective than either iv. ganciclovir or foscarnet, can also be used as a first line agent; however, it is associated with toxicity (renal and ocular) and thus needs careful use. Local therapy for CMV retinitis has been a significant advance. The intraocular ganciclovir implant has the highest efficacy of the approved agents and is well-tolerated. Fomivirsen, an oligonucleotide injected intravitreally, is a newly approved agent which offers alternative treatment. Intravitreal ganciclovir or foscarnet, although not approved, have been used successfully in some patients especially those with recurrent or refractory disease. The development of new anti-CMV agents has been stalled by the decreased incidence of the disease. Valganciclovir, a prodrug of ganciclovir, offers excellent oral bioavailability and is the closest to approval of all the new anti-CMV drugs. High ganciclovir blood levels are achieved without the complications associated with the requirement for long-term iv. access. The monoclonal antibody (mAb) MSL-109, did not offer a significant advantage when added to traditional anti-CMV therapy. Development plans of other agents such as cyclic HPMPC and lobucavir have been put on hold by their respective manufacturers. Adefovir is a nucleotide analogue that possesses anti-CMV activity, but is currently only being pursued for the treatment of hepatitis B virus. Other compounds possessing significant anti-CMV activity, including BAY 38-4766 and GW1263W94 are still in the early stages of development.

Evidence of enhanced iron excretion during systemic phosphorothioate oligodeoxynucleotide treatment.

BACKGROUND: Phosphorothioate oligonucleotides, in general, possess properties that could be utilized in the development of therapeutic heavy metal chelators. METHODS: Iron excretion was measured in 16 patients participating in studies to test the safety of OL(1)p53, a 20-mer phosphorothioate oligonucleotide complementary to p53 mRNA. Patients were given OL(1)p53 at doses of 0.05 to 0.25 mg/kg/h for 10 days by continuous intravenous infusion. Urine was collected during the study and analyzed for iron, copper, cadmium, and zinc. RESULTS: We found that phosphorothioate oligonucleotides have a high affinity for iron as well as several other clinically relevant toxic metals. Analysis of patient urine following administration of OL(1)p53 reveals a 7.5-fold increase in iron excretion at low doses (0.05 mg/kg/h). CONCLUSIONS: Phosphorothioate oligonucleotides may have therapeutic potential as heavy metal chelators. Low doses of phosphorothioate oligonucleotide facilitated the excretion of iron. Renal clearance of iron-phosphorothioate oligonucleotide complexes most likely involves secretion into proximal tubules.