Administration of pentosan polysulfate to patients with human immunodeficiency virus-associated Kaposi's sarcoma

Pentosan Polysulfate Sodium Causes Diminished Function and Subtle Morphological Changes in Retina and RPE of Mice

Purpose

There are numerous reports of a distinctive maculopathy in adults exposed to pentosan polysulfate sodium (PPS), a drug prescribed to treat bladder discomfort associated with interstitial cystitis. We tested whether PPS treatment of mice injures RPE or retina to provide insight into the etiology of the human condition.

Methods

Mice were fed PPS-supplemented chow over 14 months. RPE and retinal function was assessed by electroretinography (ERG) regularly. Following euthanasia, one eye was used for sagittal sectioning and histology, the contralateral for RPE flatmounting. ZO-1 positive RPE cell borders were imaged using confocal microscopy and cell morphology was analyzed using CellProfiler.

Results

After 10 months of PPS treatment, we observed diminution of mean scotopic c-wave amplitudes. By 11 months, we additionally observed diminutions of mean scotopic a- and b-wave amplitudes. Analysis of flatmounts revealed altered RPE cell morphology and morphometrics in PPS-treated mice, including increased mean en face cell area and geometric eccentricity, decreased RPE cell solidity and extent, and cytosolic translocation of alpha-catenin, all markers of RPE cell stress. Sex and regional differences were seen in RPE flatmount measures. Shortened photoreceptor outer segments were also observed.

Conclusions

PPS treatment reduced RPE and later retina function as measured by ERG, consistent with a primary RPE injury. Post-mortem analysis revealed extensive RPE pleomorphism and polymegathism and modest photoreceptor changes. We conclude that PPS treatment of mice causes slowly progressing RPE and photoreceptor damage and thus may provide a useful model for some retinal pathologies.

Pentosan Polysulfate Affords Pleotropic Protection to Multiple Cells and Tissues

Pentosan polysulfate (PPS), a small semi-synthetic highly sulfated heparan sulfate (HS)-like molecule, shares many of the interactive properties of HS. The aim of this review was to outline the potential of PPS as an interventional therapeutic protective agent in physiological processes affecting pathological tissues. PPS is a multifunctional molecule with diverse therapeutic actions against many disease processes. PPS has been used for decades in the treatment of interstitial cystitis and painful bowel disease, it has tissue-protective properties as a protease inhibitor in cartilage, tendon and IVD, and it has been used as a cell-directive component in bioscaffolds in tissue engineering applications. PPS regulates complement activation, coagulation, fibrinolysis and thrombocytopenia, and it promotes the synthesis of hyaluronan. Nerve growth factor production in osteocytes is inhibited by PPS, reducing bone pain in osteoarthritis and rheumatoid arthritis (OA/RA). PPS also removes fatty compounds from lipid-engorged subchondral blood vessels in OA/RA cartilage, reducing joint pain. PPS regulates cytokine and inflammatory mediator production and is also an anti-tumor agent that promotes the proliferation and differentiation of mesenchymal stem cells and the development of progenitor cell lineages that have proven to be useful in strategies designed to effect repair of the degenerate intervertebral disc (IVD) and OA cartilage. PPS stimulates proteoglycan synthesis by chondrocytes in the presence or absence of interleukin (IL)-1, and stimulates hyaluronan production by synoviocytes. PPS is thus a multifunctional tissue-protective molecule of potential therapeutic application for a diverse range of disease processes.

Phase II Study of Pentosan Polysulfate (PPS) in Patients with AIDS-related Kaposi's Sarcoma

Aims and background

To evaluate the response rate, toxicity and survival of patients with AIDS-related Kaposi's sarcoma (AIDS-KS) treated in a phase II clinical trial of pentosan polysulpate (PPS), an inhibitor of basic-fibroblast growth factor (b-FGF) which blocks the growth of Kaposi's sarcoma cells both in culture and in animal models.

Patients and methods

Between March 1992 and March 1994 16 homosexual males with histopathologically confirmed AIDS-KS were accrued for this phase II clinical trial. PPS was administered at the dose of 25 mg/m2 q6 hrs at day 1, followed by 25 mg/m2 q12 hrs daily by a subcutaneous injection. The number of patients to be included in the trial was calculated according to the two-stage Gehan method. Toxicity was graded according to the NCI Common Toxicity Criteria, while responses were evaluated according to the WHO Criteria adapted for KS lesions. Patients were all homosexual males, median age 35 (27-43) years, performance status (WHO) 1 (0-2), NYU stage II-IV and prior therapy included vincristine and etoposide (3 cases), local irradiation (4 cases) and meges-trol acetate (2 cases). Concomitant AZT (zidovudine) was given to 3 patients, while DDI (dideoxyinosine) was administered in one case.

Results

A median of 5 (3-11) weeks of therapy was administered to the patients. Pain at the injection site and low grade fever were the only toxicities observed. Drug-related effects on coagulation parameters or thrombocytopenia were not observed in the trial. One objective response (6%) was documented, which lasted for 9 weeks, while stable disease was observed in three patients, lasting for 11, 9 and 5 weeks, respectively.

Conclusion

This is the first observation of objective antitumor activity with a b-FGF inhibitor in patients with AIDS-KS. Considering its novelty and the lack of significant toxicity, the authors suggest that this experimental approach deserves further evaluation.

Angiopoietin-1 prevents severe bleeding complications induced by heparin-like drugs and fibroblast growth factor-2 in mice

Critically ill children can develop bleeding complications when treated with heparin-like drugs. These events are usually attributed to the anticoagulant activity of these drugs. However, previous studies showed that fibroblast growth factor-2 (FGF-2), a heparin-binding growth factor released in the circulation of these patients, could precipitate intestinal hemorrhages in mice treated with the heparin-like drug pentosan polysulfate (PPS). Yet very little is known about how FGF-2 induces bleeding complications in combination with heparin-like drugs. Here, we examined the mechanisms by which circulating FGF-2 induces intestinal hemorrhages in mice treated with PPS. We used a well-characterized mouse model of intestinal hemorrhages induced by FGF-2 plus PPS. Adult FVB/N mice were infected with adenovirus carrying Lac-Z or a secreted form of recombinant human FGF-2, and injected with PPS, at doses that do not induce bleeding complications per se. Mice treated with FGF-2 in combination with PPS developed an intestinal inflammatory reaction that increased the permeability and disrupted the integrity of submucosal intestinal vessels. These changes, together with the anticoagulant activity of PPS, induced lethal hemorrhages. Moreover, a genetically modified form of the endothelial ligand angiopoietin-1 (Ang-1*), which has powerful antipermeability and anti-inflammatory activity, prevented the lethal bleeding complications without correcting the anticoagulant status of these mice. These findings define new mechanisms through which FGF-2 and Ang-1* modulate the outcome of intestinal bleeding complications induced by PPS in mice and may have wider clinical implications for critically ill children treated with heparin-like drugs.

New approaches to the treatment of human herpesvirus 8-associated disease

Human herpesvirus 8 (HHV-8, also known as Kaposi sarcoma-associated herpesvirus or KSHV) is the etiologic agent of Kaposi sarcoma (KS) and primary effusion lymphoma (PEL), as well as many cases of Castleman disease. Despite significant advances in understanding the biology and natural history of these diseases, current treatment options have important limitations, and strategies to prevent their development in high-risk individuals are lacking. This article reviews the scope of HHV-8-associated disease, as well as the efficacy of current treatment options. Finally, novel approaches to treatment and prevention are described, including antiviral agents, targeted molecular therapy and a combination of these modalities.

A novel role of fibroblast growth factor-2 and pentosan polysulfate in the pathogenesis of intestinal bleeding in mice

Pentosan polysulfate (PPS) is a heparin-like polysaccharide that can affect the binding interactions of fibroblast growth factor (FGF-2) with its high-affinity receptors. Patients with angiogenic tumors frequently show high levels of FGF-2 in the circulation. Since FGF-2 is a heparin-binding angiogenic growth factor, PPS has been used successfully to block its activity in patients with angiogenic tumors. However, because of its heparin-like activity, the major toxic effect of PPS is the development of bleeding disorders. The role that circulating FGF-2 plays in the pathogenesis of bleeding disorders in patients treated with PPS is currently unknown. Here we hypothesized that FGF-2 might play a physiological role in the pathogenesis of intestinal bleeding induced by PPS. This hypothesis is supported by previous studies showing that PPS is accumulated in the intestine and that circulating FGF-2 specifically binds to and modulates the angiogenic activity of intestinal submucosal endothelial cells. We used recombinant adenoviral vectors carrying a secreted form of FGF-2 and LacZ control vectors to determine whether high levels of circulating FGF-2 facilitate the development of intestinal bleeding disorders in FVB/N and C57BL/6J mice treated with PPS. We found that PPS, acting together with FGF-2, induced structural changes in intestinal vessels leading to the development of lethal intestinal hemorrhages. These findings might have wider clinical implications for the systemic use of PPS and other heparinoids in the treatment of patients with angiogenic diseases associated with high levels of circulating FGF-2.

Polysulfated sialic acid derivatives as anti-human immunodeficiency virus

We report the synthesis of a novel alkyl polysulfated sialic acid derivative denoted as NMSO3. NMSO3 exhibited potent inhibition against both laboratory and clinical human immunodeficiency virus type 1 (HIV-1). The anti-viral activity of this compound (1 uM) was compared to dextran sulfate (3 uM), and was found to be more potent against HIV-1IIIb than AZT (10 uM). The anti-coagulation time was more than 15-fold shorter than that of dextran sulfate. An in vivo anti-viral study of NMSO3 in NOD-SCID-PBL mice HIV model showed complete protection of the animals from virus challenge at the concentration of 10 mg/kg. This suggests that NMSO3 can be effective in the treatment of HIV-infected individuals.

Treatments of AIDS-related Kaposi's sarcoma

Although Kaposi's sarcoma (KS) has decreased in countries where the highly active antiretroviral therapy (HAART) regimen is available, however it remains, after non-Hodgkin's lymphomas, the most common malignancy in HIV+ patients. Advances in the treatment of AIDS-KS have been achieved, even though a gold standard therapy has not been yet defined. With the availability of HAART, a dramatic KS clinical response has been documented, making HAART essential in all patients. In case of aggressive and/or life threatening KS, more complex therapeutic schedules have to be taken into account, including chemotherapy and/or immunotherapy. Liposomal anthracyclines and paclitaxel have been approved by FDA as first line and second line mono-therapy, respectively. Interferon-alpha (INF-alpha) is the only immunomodulant agent to have shown a therapeutic effect. Among the new drugs, many antiangiogenetic agents have produced encouraging responses. Finally, the identification of the HHV-8 as a causative agent and new metalloproteinase inhibitors may offer promising targets for the KS treatment.

Anti-angiogenic therapies in cancer clinical trials

Strategies involving vasculature have widely been acknowledged to have therapeutic potential in the management of cancer and other diseases. Based on a large body of evidence from preclinical studies and early clinical trials there is considerable optimism that anti-angiogenesis and vascular targeting will be a major clinical therapy. This review considers some 30 anti-angiogenic and vascular targeting agents that are currently in cancer clinical trials and highlights specific problems relating to the assessment of the activity of these agents in patients, trial design, potential toxicities and resistance mechanisms.

Therapy of AIDS-associated Kaposi's sarcoma: targeting pathogenetic mechanisms

Only a small number of the many agents with the potential to inhibit factors known to stimulate KS growth have been tested clinically, and many were investigated at a time when treatment options for HIV infection were relatively ineffective. The failure of some of these agents to induce KS regression may not signify failure to achieve a relevant biologic effect in all cases, but may simply mean that in a neoplasm that expresses a broad array of growth factors, inhibition of a single factor may be insufficient to achieve tumor regression. Moreover, agents that inhibit angiogenesis may be expected to stabilize tumors rather then eradicate them, but tumor stabilization is a difficult endpoint to quantify. In fact, given the redundancy of growth factors believed to be involved in KS development, it is perhaps remarkable that members of several classes of agents (eg, a synthetic retinoid, an MMPI, thalidomide, IL-12) have induced KS regression in a substantial minority of patients. It is likely, however, that drug combinations that target several pathogenetic mechanisms will be more effective than will single drugs in suppressing KS growth. A particular need. especially in the early evaluation of therapies aimed at specific pathogenic targets, is the development of assays to measure specific biologic effects (eg, changes in the activity of signal transduction pathways within tumor biopsy specimens) related to the agent's putative mechanism of action. Greater availability and clinical application of these types of markers of biologic efficacy may speed the identification of potentially active agents that could then be "fast tracked" into larger efficacy trials and combination studies.

Optimisation for the separation of the oligosaccharide, sodium Pentosan Polysulfate by reverse polarity capillary zone electrophoresis using a central composite design

The separation by reverse polarity capillary zone electrophoresis of the therapeutically developed sodium salt of Pentosan Polysulfate was optimised through the analysis of response surface methodologies, modeled using a central composite design. The optimisation investigated injection pressure, injection time and voltage and the effect of the conditions on retention times, peak areas, separation efficiency and the method sensitivity. The overall goal was to develop the most sensitive results with no decrease in separation efficiency. The following results were obtained: (1) retention times generally decreased as injection pressure, injection time and voltage increased, injection time having the least effect; (2) as expected peak areas increased as injection pressure and injection time increased but decreased as voltage increased; (3) separation efficiencies generally increased as injection pressure and injection time decreased, with voltage having almost no effect. For the optimum condition, the sample was introduced at the inlet vial at the cathode hydrodynamically, at optimal setting of 44 s at 35 mbar. The optimal voltage was -20 kV. In comparison with other methods, the optimum showed increased sensitivity, resolution and separation efficiency. Repeatability studies were performed on the optimum parameter conditions. Relative standard deviation values obtained were between 0.9 and 5.4%.

A multicenter phase II study of the intravenous administration of liposomal tretinoin in patients with acquired immunodeficiency syndrome-associated Kaposi's sarcoma

BACKGROUND

A multicenter trial was conducted to determine the efficacy and toxicity of escalating dosages of liposomal tretinoin (all-trans-retinoic acid) administered once or three times weekly in patients with acquired immunodeficiency syndrome (AIDS)-associated Kaposi sarcoma.

METHODS

Seventy-six patients with acquired immunodeficiency syndrome (AIDS)-associated Kaposi sarcoma were randomized to receive the study drug either once (n = 30) or 3 times weekly (n = 46). The starting dosage was 60 mg/m(2), which was escalated to 90 mg/m(2) and then 120 mg/m(2) if the drug was well tolerated (<or= Grade 2 toxicities [according to the Southwest Oncology Group toxicity scale]). Four weeks of therapy constituted 1 cycle; patients could receive up to 8 cycles and those who completed 8 cycles were given the option of receiving extended therapy. Clinical response was defined as complete response (CR), partial response (PR), or stable disease (SD).

RESULTS

Efficacy was assessed after the completion of 3 treatment cycles; 28.9% of patients (22 of 76 patients) responded (no CRs, 1 PR, and 21 SDs). Among the patients receiving treatment 3 times weekly, 16 of 49 patients (32.7%) achieved a clinical response at the end of the third treatment cycle (no CRs, 1 PR, and 15 SDs). Concomitant or prior use of protease inhibitors did not appear to affect the patient's response to treatment (P = 0.183).

CONCLUSIONS

Liposomal tretinoin is a new therapeutic agent that has been reported to have some clinical activity in patients with AIDS-associated Kaposi sarcoma. A three-times-per-week dosing schedule was noted to be more effective compared with a once-a-week schedule without any significant difference in toxicity reported.

Recent advances in the treatment of AIDS-related Kaposi's sarcoma

Kaposi's sarcoma (KS) is the most common malignancy associated with HIV infection and is considered an AIDS defining condition by the US Centers of Disease Control Guidelines. Several advances in the treatment of AIDS-related KS have been achieved over the past few years, even though a gold standard therapy for KS has not yet been defined and treatment must be tailored to individual needs. Since the availability of highly active antiretroviral therapy (HAART), a dramatic clinical response has been documented in patients with KS, making HAART an essential approach in the management of KS in most, if not all, patients with AIDS-related KS. However, in case of aggressive, visceral, and/or life-threatening KS, more complex therapeutic schedules have to be taken into account, including chemotherapy, radiotherapy, and/or immunotherapy. In general, systemic treatment for KS is limited to widespread, symptomatic disease, whereas local interventions are indicated for minimal, cosmetically troublesome lesions. Among new cytotoxic agents, liposomal anthracyclines and paclitaxel are highly effective molecules for KS and have been approved by the US Food and Drug Administration (FDA) as first-line and second-line monotherapy, respectively, for advanced KS. Furthermore, a greater understanding of the pathogenesis of KS has lead to the development of an array of new experimental agents. Many antiangiogenic agents such as AGM 1470 (TNP 470), thalidomide, and glufanide disodium (IM 862) have produced encouraging responses in patients with KS and large clinical trials are in progress. Retinoic acids may also block neoangiogenesis as well as proliferation of KS cells in vitro, and they have been used either systemically or topically with a high response rate. Thus, a topical compound 0.1% alitretinoin gel was approved in 1999 by the FDA for the treatment of skin lesions associated with KS. Human chorionic gonadotropin, a hormonal agent, has shown a strong inhibitory activity in KS cells, but its role in the regression of KS lesions is not clear. Finally, the identification of a novel gamma-herpesvirus, human herpesvirus-8, as a causative agent for KS, together with novel antiangiogenic compounds, such as metalloproteinase inhibitors, may offer promising targets for the therapy of KS.

Angiogenesis and antiangiogenic approaches to sarcomas

Established chemotherapy regimens for advanced or metastatic sarcoma generally have low response rates and substantial toxicity, and resistance often arises quickly, making sarcoma an ideal target for alternative treatment approaches. Antiangiogenic therapies have a number of potential advantages including decreased resistance, fewer side effects, and a broad spectrum of activity. This paper reviews the evidence supporting the use of antiangiogenic therapies for adult soft tissue sarcomas. Human sarcomas express a number of proangiogenic factors that may represent therapeutic targets, with vascular endothelial growth factor being the best characterized, and inhibitors of angiogenesis have antitumor activity in animal models of human sarcomas. Clinical trials are in early stages, although promising results have already been seen. In the future, improved drugs, refined molecular profiling of tumors, and new ways of combining antiangiogenic agents with cytotoxic agents may lead to more effective and tolerable therapies for sarcomas.

Activity of thalidomide in AIDS-related Kaposi's sarcoma

PURPOSE

To assess the toxicity and activity of oral thalidomide in Kaposi's sarcoma (KS) in a phase II dose-escalation study.

PATIENTS AND METHODS

Human immunodeficiency virus (HIV)-seropositive patients with biopsy-confirmed KS that progressed over the 2 months before enrollment received an initial dose of 200 mg/d of oral thalidomide in a phase II study. The dose was increased to a maximum of 1,000 mg/d for up to 1 year. Anti-HIV therapy was maintained during the study period. Toxicity, tumor response, immunologic and angiogenic factors, and virologic parameters were assessed.

RESULTS

Twenty patients aged 29 to 49 years with a median CD4 count of 246 cells/mm(3) (range, 14 to 646 cells/mm(3)) were enrolled. All patients were assessable for toxicity, and 17 for response. Drowsiness in nine and depression in seven patients were the most frequent toxicities observed. Eight (47%; 95% confidence interval [CI], 23% to 72%) of the 17 assessable patients achieved a partial response, and an additional two patients had stable disease. Based on all 20 patients treated, the response rate was 40% (95% CI, 19% to 64%). The median thalidomide dose at the time of response was 500 mg/d (range, 400 to 1,000 mg/d). The median duration of drug treatment was 6.3 months, and the median time to progression was 7.3 months.

CONCLUSION

Oral thalidomide was tolerated in this population at doses up to 1,000 mg/d for as long as 12 months and was found to induce clinically meaningful anti-KS responses in a sizable subset of the patients. Additional studies of this agent in KS are warranted.

Anti-HIV activity of extracts and compounds from algae and cyanobacteria

The human immunodeficiency virus (HIV) is the retrovirus that causes the acquired immune deficiency disease syndrome (AIDS). This review discusses the anti-HIV activity of extracts and compounds isolated from freshwater and marine algae, and cyanobacteria (formerly called "blue-green algae"). Compounds and extracts with anti-HIV activity are also active against other retroviruses such as herpes simplex virus (HSV), but the amount of antiviral activity varies with the compound and the virus. Most of the research has focused on sulfated homopolysaccharides and heteropolysaccharides. Sulfoglycolipids, carrageenans, fucoidan, sesquiterpene hydroquinones, and other classes of compounds with anti-HIV activity that have been isolated from algae have received less attention. Most studies have used in vitro test systems, but a few in vivo studies have been carried out using compounds isolated from algae or analogs produced synthetically or isolated from other natural sources. Sulfated homopolysaccharides are more potent than sulfated heteropolysaccharides. The presence of the sulfate group is necessary for anti-HIV activity, and potency increases with the degree of sulfation. Studies using nonsulfated and sulfated homo- and heteropolysaccharides isolated from algae or other natural sources, or synthesized, have revealed the mechanisms of binding of drugs to the virion, and the mechanisms of viral binding to host cells. However, given the few classes of compounds investigated, most of the pharmacopeia of compounds in algae and cyanobacteria with antiretroviral activity is probably not known.

Results of a randomized study of IM862 nasal solution in the treatment of AIDS-related Kaposi's sarcoma

PURPOSE

Although advances have been made in the treatment of AIDS-related Kaposi's sarcoma (AIDS-KS) with systemic chemotherapy, less toxic therapies are needed. IM862 is a naturally occurring peptide with antiangiogenic properties and was thus studied in patients with AIDS-KS.

PATIENTS AND METHODS

IM862 was given as intranasal drops at a dose of 5 mg. Patients were randomized to two dosing schedules given in repeated cycles until disease progression or unacceptable toxicity: 5 days of therapy followed by 5 days off (n = 18) and every other day dosing (n = 26).

RESULTS

Forty-two male patients and two female patients with a median age of 38 years (range, 22 to 53 years) were accrued. Twenty-one patients (47%) had more than 50 mucocutaneous lesions, 14 (32%) had lymphedema, and none had visceral involvement. Thirty-three patients (75%) had received prior systemic chemotherapy. Twenty-four patients (55%) had CD4(+) lymphocyte count </= 200/mm(3). All but five patients were being treated with concurrent protease inhibitor(s), for a median of 10 months (range, 0 to 24 months). Major responses were documented in 36%, with five complete and 11 partial remissions, occurring after a median of 6 weeks (range, 3 to 26 weeks) and lasting a median of 33+ weeks (range, 12+ to 95+ weeks). Twenty-one patients had stable disease for periods of 7 to 72+ weeks. Adverse effects to IM862 were limited to mild and transient headache, fatigue, tingling, and nausea. No hematologic adverse effects attributed to treatment were reported.

CONCLUSION

IM862 given as intranasal drops is well tolerated and has antitumor activity in patients with AIDS-KS. A randomized double-blinded study to define the activity of IM862 in patients with AIDS-KS is in progress.

[Anti-angiogenesis: a new approach to tumor therapy?]

BACKGROUND

The overall mortality due to metastatic cancer has not or only minimally been reduced in spite of intensive research and many innovations in the field of conventional antineoplastic therapy in the past decade. In the last years it has become a fact that tumor growth is angiogenesis-dependent. Therefore, inhibitors of angiogenesis are a new class of antineoplastic substances with a novel mechanism of action that might be a powerful complement to conventional cytostatic therapy. SUBSTANCES AND CLINICAL TRIALS: Inhibitors of tumor-angiogenesis which have entered clinical trials, with their results published until December 1998 are discussed here. Most results originate from phase-I or phase-II clinical trials. They are discussed and compared in respect to toxicity and response. Also some substances with high therapeutic potential which are still in preclinical testing are discussed.

RESULTS

Many of the investigated angiogenesis inhibitors demonstrated anti-tumor effects in phase-I or phase-II clinical trials. The commonest manifestation was stable disease, followed by partial remissions. In a few cases, complete remissions were observed. The toxicities of these substances differ both in type and degree of side effects.

CONCLUSION

Some antiangiogenic drugs appear to be promising candidates for a clinical use in the therapy of solid tumors. Further conclusions can only be drawn after evaluation of the results of ongoing phase-III clinical trials.

Anti-Kaposi's sarcoma and antiangiogenic activities of sulfated dextrins

Delivery of the sulfated polysaccharide dextrin 2-sulfate by the intraperitoneal route to the lymphatic circulation resulted in a clinically significant improvement in Kaposi's sarcoma in three patients. Our in vitro studies show that although sulfated dextrins do not interfere with the growth of isolated human umbilical vein endothelial cells, they do inhibit the morphological differentiation of endothelial cells into tubes as well as reduce new vessel formation in a placental angiogenesis assay. The antiangiogenic effect of dextrin 6-sulfate is greater than that of dextrin 2-sulfate and is independent of their anti-human immunodeficiency virus type 1 activities.

Activation of the high affinity nerve growth factor receptor by two polyanionic chemotherapeutic agents: role in drug induced neurotoxicity

Suramin is a polyanionic chemotherapeutic agent which causes severe peripheral neuropathy. The mechanisms of antineoplastic and neurotoxic activities are still poorly understood. Interference with growth factor receptor function has been suggested for suramin's chemotherapeutic function. Previous studies from our laboratory have demonstrated that suramin interfered with the function of nerve growth factor (NGF) and induced lysosomal storage defects within dorsal root ganglion neurons. Pentosan polysulfate (PPS) was used as another polyanionic agent, to compare these two cellular functions; NGF receptor interaction and disruption in glycolipid metabolism. Like suramin and NGF, PPS induced neurite outgrowth from the PC12 cell line which correlated with tyrosine phosphorylation of the high affinity NGF receptor (TrkA/gpl40) and ERK-1/MAP kinase. Ultrastructural studies of dorsal root ganglion exposed to PPS for various time periods were normal. This contrasted with suramin exposed cultures which consistently developed lamellar inclusion bodies (LIB) within 6 h. LIB formation with suramin treatment was associated with neuronal cell death, while PPS treatment did not cause any neurotoxic effects. These results indicated that PPS mimicked the effect of suramin on NGF receptors but did not cause similar accumulation of LIB. This suggested that the effect of polyanionic compounds on TrkA was not involved in LIB accumulation and subsequent induction of neurotoxicity.

Structure-function relations of heparin-mimetic sulfated xylan oligosaccharides: inhibition of human immunodeficiency virus-1 infectivity in vitro

Heparins/heparan sulfates modulate the function of proteins and cell membranes in numerous biological systems including normal and disease processes in humans. Heparin has been used for many years as an anticoagulant, and anticoagulant heparin-mimetics were developed several decades ago by chemical sulfation of non-mammalian polysaccharides, e.g., an antithrombotic sulfated xylan. This pharmaceutical, which comprises a mixture of sulfated oligoxylans, also mimics most other biological actions of natural heparins in vitro, including inhibition of the human immunodeficiency virus, but the molecular basis for these actions has been unclear. Here, numerous Components of the sulfated oligoxylan mixture were isolated and when bioassayed in the case of anti-HIV-1 infectivity revealed that a structural specificity underlines the capacity of sulfated xylan to inhibit HIV-1, rather than a non-specific mechanism. Components were isolated by chromatographic fractionation through Bio-Gel P10 in 0.5 M ammonium bicarbonate. This fractionation revealed an elution range associated with apparent molecular weights of approximately 22000 to <1500 relative to standard heparin and heparan sulfates and newly prepared sulfated oligosaccharide standards. Components were characterized by metachromatic absorption spectroscopy, ultracentrifugation, GlcA analysis, and potency against HIV-1 infectivity, both in the tetrazolium cytotoxicity assay and in syncytium-forming assays, in CD4-lymphocytes. Structural specificity was indicated by the differential potencies exhibited by the Components: Highest activity (cytotoxicity) was exhibited by Components in the chromatographic region > or = approximately 5500 in mass (50% effective (inhibitory) concentration = 0.5-0.7 microg ml(-1) in the first fractionation series, and 0.1-0.5 microg ml(-1) in a second series). The potency declined sharply below approximately 5400 in mass, but with an exception; a second structure exhibiting relatively high potency eluted among low-mass oligosaccharides which had an average size of approximately a nonomer. Components displayed differential potencies also against the syncytium-forming infectivity of HIV-1. The high potency against syncytium-formation was retained by Components down to a minimum size of about 4500 in mass, smaller than the > or = approximately 5400 required above. One in ten of the beta1,4-linked xyloses in the native xylan are substituted with a monomeric alpha1,2 DGlcA branch. We have speculated that pharmaceutical actions of sulfated xylan might be related to structures involving the alpha-D linked substituents and this was examined using a space-filling model of a sulfated octaxylan and by analyses of Components for GlcA content. Understanding structure/function relations in the heparin-like actions of these agents would be of general significance for the careful examination of their potential clinical usefulness in many human processes modulated by heparins, including AIDS.

Advances in Kaposi's sarcoma

KS remains a challenge to clinicians and investigators more than a century after its initial description. Debate continues as to the cell of origin, as well as whether or not it is a true cancer. KS appears to be an opportunistic neoplasm, which in its earliest phase retains some features of a benign hyperproliferative process, but in its late stages behaves like an aggressive malignancy. Pathogenesis seems to involve a predisposed individual (genetically susceptible or immunologically compromised) who comes into contact with an infectious agent, most likely a virus. Cytokines appear to play a major role in the growth of the tumor. The exact role of the KSHV in this process will likely be the subject of much investigation in the future.

An overview of clinical trials involving inhibitors of angiogenesis and their mechanism of action

Angiogenesis is a biologic process whereby endothelial cells divide and migrate to form new blood vessels. This process is required in physiological conditions, but is also a necessary requirement for solid tumors to grow and metastasize. Over the last several years, the growth factors that have both a positive and negative influence on tumor angiogenesis have been delineated. Interfering with tumor angiogenesis was considered a potential therapeutic strategy 25 years ago, but only recently have compounds with an ability to interfere with angiogenesis entered clinical trials. This review will discuss the first generation of angiogenesis inhibitors, their mechanism of action and data from clinical trials.

A phase I study of pentosan polysulfate sodium in patients with advanced malignancies

BACKGROUND

Pentosan polysulfate (xylanopolyhydrogensulfate) is a semi-synthetic sulfated heparinoid polysaccharide which has been used as an anticoagulant for nearly thirty years in Europe. It antagonizes the binding of bFGF to cell surface receptors and has thus been evaluated for antitumor activity in several animal models and human tumor cell lines. In two angiogenic models pentosan has been shown to inhibit bFGF stimulation of angiogenesis. Previous clinical studies have determined the coagulation effects of pentosan to be the dose-limiting toxicity.

PATIENTS AND METHODS

We conducted a phase I study designed to define the duration-limiting toxicity associated with progressive prolongation of a continuous intravenous infusion (three, five, and eight weeks). This study was not designed to escalate the dose of pentosan beyond that required to maintain the activated partial thromboplastin time (aPTT) between 1.8 and 2.2 times the baseline value.

RESULTS

Thirteen patients with advanced stage metastatic cancer were enrolled (median age 50 years, range 34 to 61 years). Four patients were treated in cohort #1 (three weeks of infusional therapy), five patients were treated in cohort #2 (five weeks of therapy), and four patients in cohort #3 (eight weeks of therapy). All patients experienced a progressive prolongation of their aPTT and PT. Furthermore, all patients experienced at least grade I thrombocytopenia. Other complications were, in general, mild. One patient developed grade III liver abnormalities while receiving the eight-week infusion and another patient developed grade IV thrombocytopenia while receiving the same regimen. One patient with colon cancer had stable disease for 24 weeks, while the remaining 12 patients had no objective evidence of response.

CONCLUSION

Pentosan was well tolerated when doses were adjusted for aPTT prolongations and a five-week cycle appeared to be the maximum tolerated duration of infusion (initially 4 mg/kg/day). One patient had stable disease, but there was no objective tumor response noted in the remaining 12 patients.

AIDS-related Kaposi's sarcoma. A template for the translation of molecular pathogenesis into targeted therapeutic approaches

AIDS-related Kaposi's sarcoma (KS) represents a complex interaction of host and viral factors. There are a number of fundamental questions surrounding the interplay between the disparate factors that can contribute to the pathogenesis and pathophysiology of this disease. Targets such as the enhancement of immune function, inhibition of angiogenic factors or immunostimulatory cytokines, inhibition of viral proteins such as Tat, or hormonal manipulations are now or will in the future become the focus of research to develop innovative anti-KS therapy and prevention measures. Antiviral approaches aimed at HIV or other viruses may potentially target a number of steps in KS pathogenesis. This article reviews diverse modalities--cytotoxic, antiviral, gene-directed, growth factor-targeted, and antiangiogenesis--that singly, or more likely in combination, stand to make an impact on the cure and prevention of AIDS-related KS.

Clinical implications of tumor-associated neovascularization and current antiangiogenic strategies for the treatment of malignancies of pancreas

There is now a substantial body of evidence that tumor growth is angiogenesis-dependent, and that neovascularization is also necessary for tumor invasion and metastasis. In addition, the assessment of microvessel count or density in a primary tumor may ultimately prove to be significant and independent prognostic parameter for clinical outcome with respect to tumor recurrence, metastasis, and ultimately, overall patient survival. As our knowledge of the pathways, steps, and factors involved in the underlying pathogenesis of tumor-associate angiogenesis increases, therapeutic agents and modalities aimed at inhibiting angiogenesis by blocking one or more of these steps or factors may be devised and evaluated for their potential to inhibit cancer growth and spread. Ultimately, the inhibition of tumor-associated angiogenesis and associated processes could conceivably form the foundation upon which the treatment of aggressive malignancies is based.

A phase I clinical and pharmacokinetic study of the angiogenesis inhibitor, tecogalan sodium

BACKGROUND

Tecogalan sodium is an angiogenesis inhibitor isolated from a sulfated polysaccharide produced by the bacterium Arthrobacter. The antiangiogenic effect of tecogalan sodium is thought to be mediated by the inhibition of binding of basic fibroblast growth factor to cellular receptors.

PATIENTS AND METHODS

A phase I study was conducted in thirty-three patients with refractory malignancies, including AIDS-associated Kaposi's sarcoma. Patients received a single i.v. infusion every three weeks with the infusion duration ranging from one to twenty-four hours. Seven different dosage levels were studied (125, 185, 240, 300, 390, 445, and 500 mg/m2).

RESULTS

The primary dose-limiting toxicity was prolongation of the activated partial thromboplastin time with peak times being between 1.0-4.0 times the upper limit of normal. This toxicity was ameliorated at a given dose level by prolonging the infusion time. Other common toxicities included fever (40%) and rigors (31%) which were well controlled with acetominophen and meperidine. The serum half-life of tecogalan sodium was between 1-1.5 hours and < 25% of unchanged drug was excreted in the urine.

CONCLUSIONS

The recommended phase II dose of tecogalan sodium on this schedule is 390 mg/m2 over 24 hours. Other schedules including continuous administration should be investigated to maximize the efficacy of this novel angiogenesis inhibitor.

Inhibition of angiogenesis and murine tumour growth by laminarin sulphate

LAM S5 is a polysulphated derivative of the glucan laminarian that inhibits basic fibroblast growth factor (bFGF) binding and the bFGF-stimulated proliferation of fetal bovine heart endothelial (FBHE) cells. This report demonstrates that LAM S5 has anti-angiogenic activity, as shown by inhibition of tubule formation by endothelial cells cultured on Matrigel and inhibition of vascularisation of the chick chorioallantoic membrane. In addition, LAM S5 caused a tumour growth delay of the murine RIF-1 tumour of 2.6 days (P = 0.01).

Kaposi's sarcoma: advances and perspectives

Kaposi's sarcoma (KS) is an unusual neoplasm that has proved to be an enigma in many ways since its original description by Kaposi in 1872. Its epidemiology has stimulated tremendous interest, amplified markedly in 1981 when it became known as an original defining part of the complex of immune disorders now known as AIDS. The cell of origin, etiology, and therapy for both AIDS-associated and AIDS-unassociated KS continue as matters of intense investigation. In fact, whether it is a reactive hyperplasia or a true malignancy is still a matter of debate, as is the concept of multicentricity versus metastases. Epidemiologic studies suggest that a separate agent apart from HIV-1 may cause KS. A newly postulated KS-associated herpes virus may be linked. The role of the HIV-1 tat gene product, basic fibroblast growth factor, scatter factor, oncostatin M, and other factors that regulate the growth of KS cells are discussed, as well as therapeutic options.

Characterisation of a laminarin sulphate which inhibits basic fibroblast growth factor binding and endothelial cell proliferation

We have evaluated a series of laminarin sulphates with different degrees of sulphation (0.3-2.3) as antagonists of basic fibroblast growth factor (bFGF) and as inhibitors of the bFGF-dependent endothelial cell line FBHE. Inhibition of binding of bFGF by the laminarin sulphates increased with increasing degree of sulphation. Binding of bFGF to low affinity sites on BHK cells was inhibited more strongly than binding to high affinity sites. IC50 values for inhibition of binding to low and high affinity sites by the most highly sulphated laminarin sulphate (LAM S5; degree of sulphation 2.31) were 12 +/- 8 micrograms/ml and 69 +/- 66 micrograms/ml, respectively. LAM S5 dissociated bFGF from low affinity sites on BHK cells but not from high affinity sites. LAM S5 increased the electrophoretic mobility of bFGF indicating that LAM S5 binds directly to bFGF. LAM S5 reduced uptake of bFGF by FBHE cells by 67%. Increasing the degree of sulphation of laminarin sulphates increased the inhibition of bFGF-stimulated DNA synthesis of the endothelial cell line FBHE (IC50 for LAM S5 approx. 1 microgram/ml). There was no inhibition of DNA synthesis of FBHE cells by LAM S5 in the presence of 1 microgram/ml bFGF indicating that bFGF antagonism is involved in the anti-proliferative activity of this compound. LAM S5 may be of value against diseases associated with bFGF-dependent cell proliferation.

Selective inhibition of cell proliferation and DNA synthesis by the polysulphated carbohydrate l-carrageenan

l-Carrageenan is a polysulphated carbohydrate that antagonises some heparin-binding growth factors. We assessed the effect of l-carrageenan on the proliferation of a panel of cell lines, some of which require heparin-binding growth factors for mitogenesis. The importance of growth factor antagonism for the anti-proliferative activity was also determined. Cell proliferation was determined by cell counts and a tetrazolium dye (MTT) assay, and DNA synthesis was determined by thymidine incorporation. The proliferation of the basic fibroblast growth factor (bFGF)-dependent endothelial cell line FBHE was inhibited by daily administration of l-carrageenan in a dose-dependent manner [concentration inhibiting cell growth by 50% (IC50 value), approx. 0.5 microgram/ml]. However, excess bFGF did not reverse the inhibitory effect. DNA synthesis was completely inhibited by concentrations of l-carrageenan that nonetheless allowed significant protein synthesis to occur. The proliferation of the androgen-dependent prostate-carcinoma cell line LNCaP was also inhibited by l-carrageenan (IC50 value, 5.5 micrograms/ml) and the cells were arrested at the G1/S boundary. l-Carrageenan inhibited DNA synthesis in MCF-7 cells stimulated by bFGF and transforming growth factor alpha (TGF alpha) but not in those stimulated by insulin-like growth factor 1 (IGF-1). Blocking IGF-1-mediated DNA synthesis with anti-IGF-1 receptor antibody alpha IR3 enhanced the inhibitory activity of l-carrageenan against MCF-7 cells grown in serum. A number of other transformed and non-transformed cell lines were either partially inhibited or not inhibited by l-carrageenan. l-Carrageenan had low anti-coagulant activity. l-Carrageenan is a selective anti-proliferative agent and warrants further investigation for anti-angiogenic therapy (in view of its activity against endothelial cells) and for the treatment of androgen-dependent prostate cancer.

Antiviral therapy for human immunodeficiency virus infections

Depending on the stage of their intervention with the viral replicative cycle, human immunodeficiency virus inhibitors could be divided into the following groups: (i) adsorption inhibitors (i.e., CD4 constructs, polysulfates, polysulfonates, polycarboxylates, and polyoxometalates), (ii) fusion inhibitors (i.e., plant lectins, succinylated or aconitylated albumins, and betulinic acid derivatives), (iii) uncoating inhibitors (i.e., bicyclams), (iv) reverse transcription inhibitors acting either competitively with the substrate binding site (i.e., dideoxynucleoside analogs and acyclic nucleoside phosphonates) or allosterically with a nonsubstrate binding site (i.e., non-nucleoside reverse transcriptase inhibitors), (v) integration inhibitors, (vi) DNA replication inhibitors, (vii) transcription inhibitors (i.e., antisense oligodeoxynucleotides and Tat antagonists), (viii) translation inhibitors (i.e., antisense oligodeoxynucleotides and ribozymes), (ix) maturation inhibitors (i.e., protease inhibitors, myristoylation inhibitors, and glycosylation inhibitors), and finally, (x) budding (assembly/release) inhibitors. Current knowledge, including the therapeutic potential, of these various inhibitors is discussed. In view of their potential clinical the utility, the problem of virus-drug resistance and possible strategies to circumvent this problem are also addressed.

Phase I trial of pentosan polysulfate

Pentosan polysulfate is a semisynthetic pentasaccharide heparinoid derived from beechwood shavings. A total of nineteen patients with various adult solid tumors were treated with three dose levels (15, 22.5, and 30 mg/m2/dose) of subcutaneous pentosan polysulfate every 6 hours. The dose limiting toxicities were thrombocytopenia and elevated transaminases at the dose of 30 mg/m2 every 6 hours. The recommended starting dose for phase II trials is 22.5 mg/m2 given every 6 hours. There was an increase in anticoagulant activity as measured by activated partial thromboplastin time (aPTT) at the dose of 22.5 mg/m2 every 6 hours in most patients. There were no objective responses and three patients had stable disease lasting 16, 19 and 76 weeks.

Pentosan-induced thrombocytopenia: support for an immune complex mechanism

Pentosan polysulphate is a low molecular weight heparinoid that is used as an anticoagulant. Because the drug also has antineoplastic properties, it has been used experimentally at the National Institutes of Health to treat metastatic malignancies. We present the case of a patient who developed thrombocytopenia resembling Type II heparin-induced thrombocytopenia (HIT) during the course of pentosan therapy. The patient's plasma demonstrated platelet reactivity both by aggregometry and 14C-serotonin release in the presence of pentosan. Heparin and other polyanions could substitute for pentosan in aggregation studies. The aggregating activity co-purified with the patient's IgG and was inhibited by pre-incubation with monoclonal antibody (MoAb) to the platelet Fc receptor. To elucidate the relationship between the platelet, the polyanion and the antibody, we measured the binding of 3H-heparin to platelets in the presence of the patient's IgG and found that it was increased 6-fold over binding in the presence of control IgG. Heparin binding was not reduced by MoAb against the Fc receptor. Taken together, these data support a model in which polyanion-antibody complexes attach to the platelet surface by the polyanion and secondarily stimulate the platelet via their Fc termini.

HIV-related tumors of the oral cavity

In HIV-infected patients with AIDS the most frequent malignancies are Kaposi's sarcoma and non-Hodgkin's lymphoma. In these patients, the natural history of these tumors is quite different from those of HIV-negative subjects. These tumors may present atypical clinical aspects, may be very aggressive, and the coexistence of immunosuppression and opportunistic infections may render their treatment more difficult. The aim of this article is to provide updated information on the epidemiology, pathogenesis, natural history, and management of tumors that develop in the oral cavity of patients with AIDS.