Development of a multiple-drug delivery implant for intraocular management of proliferative vitreoretinopathy

A prototype multiple-drug delivery implant has been developed for the intraocular management of proliferative vitreoretinopathy (PVR). Because of the recurrent nature of the disease, PVR causes blindness in approximately 7% of patients who have undergone retinal re-attachment surgery. The poly(dl-lactide-co-glycolide) 50/50 (PLGA) implant consists of three cylindrical segments, each of which contains one of the following drugs: 5-fluorouridine (5FUrd, an antimetabolite), triamcinolone (Triam, a corticosteroid), and human recombinant tissue plasminogen activator (t-PA, a thrombolytic agent). The device can be inserted through a 20-gauge syringe needle into the vitreous body of the eye. The implant also possesses a PLGA coating over the t-PA-containing terminal segment, which creates a lag-time to deliver t-PA when most needed and to decrease the risk of postoperative bleeding. Two methods of cylinder fabrication were investigated: heat and solvent extrusion. The release behavior of several drugs was examined as a function of the processing variables including: extrusion method, drug loading, polymer molecular weight, and drug particle size. The presence of either the organic solvent (acetone) during processing or a highly water-soluble drug (5FUrd) in the formulation increased the polymer porosity, which in turn, increased the drug release-rate. Drug loading effects were consistent with percolation concepts, and a low-molecular-weight PLGA (e.g., Mw=42000 for inherent viscosity=0.58 dl/g) was desirable to produce controlled release close to one month. Based on pharmacological and pharmacokinetic data of these compounds and our clinical experience with this disease, several design criteria for a combined implant were devised. Optimal cylindrical segments from the formulation studies were selected and combined in series to form a contiguous implant. After successful combination and coating procedures were developed, prototype implants were prepared. From the 3-drug prototype, 5FUrd and Triam were released approximately 1 microgram/day for over 4 weeks and 10-190 microgram/day over 2 weeks, respectively. The solvent-extrusion procedure did not significantly alter the stability of the encapsulated t-PA (>94+/-5% serine protease activity after preparation). After a lag-time of approximately 2 days, t-PA was released active at a rate of approximately 0.2-0.5 microgram/day in approximately 2 weeks. The release characteristics from the combined implant largely met our initial design criteria. Hence, controlled-release implants of this kind may have potential use for intraocular treatment of PVR.     

Longitudinal element size effect on load sharing, internal loads, and fatigue life of tri-level spinal implant constructs

The effects of implant stiffness on load sharing and stress shielding, of vertebral column load sharing on implant fatigue life, and of instrumenting two versus one level adjacent to a comminuted segment on implant internal loads were studied. Finite element models of six screw constructs with 4.76 mm rod; 6.35 mm rod, and VSP plate tri-level instrumentation of two motion segments (healthy vertebra case and comminuted) and an adjacent healthy motion segment with dimensions representative of the human lumbar spine were used. Also a simplified model was developed to predict the percent of axial load passing through the column, which is a function of ki/kv the ratio of implant axial stiffness to instrumented vertebral column axial stiffness. For constructs with dimensions typical of the human lumbar spine, 77 to 80% of the axial load was predicted to pass through one or two healthy motion segments when instrumented with either 6.35 mm rod or VSP plates, compared to 90% when instrumented with 4.76 mm rods. When instrumenting smaller motion segments (in dogs) for comparison, 60% of the axial load was predicted to pass through the column for 4.76 mm rod and 33% for 6.35 mm rod constructs due to increased implant stiffness ki as a result of decreased AP and longitudinal construct dimensions, and lower canine motion segment stiffness kv.(ABSTRACT TRUNCATED AT 250 WORDS)     

A study of oral morphine preference in inbred mouse strains

The generative potential of free perichondrial grafts from rabbit auricular and rib cartilage around a self-reinforced polyglycolic acid (SR-PGA) rod was examined in eight growing rabbits. A 15 x 15 mm perichondrial graft was dissected away from the posterior side of each auricular cartilage. One graft was wrapped around a 1.1 x 10 mm SR-PGA rod and the other served as a control and was shaped into a tube without an implant. Fifth rib cartilages were then resected subperichondrially on both sides. The remaining perichondrium on the other side was wrapped around a 1.1 x 10 mm SR-PGA rod, while the other served as a control and was shaped into a tube without an implant. All the grafts were placed inside pectoralis major muscles. Grafts were biopsied six weeks postoperatively. Neocartilage formation was seen in all grafts with one exception on both the implant and control sides. It formed a tube-like structure around the implant in four cases after grafting of auricular perichondrium and in three cases after grafting of rib perichondrium. New bone formation was also observed. SR-PGA implants did not seem to disturb the generative potential of perichondrium.     

Excretion of a radiolabelled anticancer biodegradable polymeric implant from the rabbit brain

The elimination of a clinically used anticancer biodegradable polymer implant (Gliadel) in the rabbit brain was studied. The implant is composed of N,N-bis(2-chloroethyl)-N-nitrosourea (BCNU) (1.6 wt%) dispersed in a copolyanhydride matrix of 1,3-bis(p-carboxyphenoxypropane) (CPP) and sebacic acid (SA) in a 20:80 molar ratio. Four groups of rabbits were implanted with wafers loaded with BCNU, one in a 14C-SA-labelled polymer, another in a 14C-CPP-labelled polymer and two groups with 14C-BCNU in a non-labelled polymer, one for BCNU disposition study and one for residual drug study. In the rabbits implanted with the 14C-SA-labelled polymer, approximately 10% of the radioactivity was found in the urine and 2% in the faeces, and about 10% remained in the device 7 d after implantation. In contrast, only 4% of the radioactivity of the 14C-CPP-labelled polymer was found in urine and faeces during this period. However, a drastic increase in the CPP excretion was found after 9 d, and at 21 d, 64% of the implanted 14C-CPP was found in the urine and faeces, and 29% was still in the recovered wafers. Approximately 50% of the BCNU in the wafers was released in 3 d, and over 95% was released after 6 d in the rabbit brain. This study demonstrates that BCNU-loaded polyanhydride is biodegradable and is excreted from the body primarily through the renal system. The water-soluble components SA and BCNU were rapidly excreted, while the insoluble CPP was gradually eliminated after a lag time of 9 d.     

Manufacture of porous biodegradable polymer conduits by an extrusion process for guided tissue regeneration

We have fabricated porous, biodegradable tubular conduits for guided tissue regeneration using a combined solvent casting and extrusion technique. The biodegradable polymers used in this study were poly(DL-lactic-co-glycolic acid) (PLGA) and poly(L-lactic acid) (PLLA). A polymer/salt composite was first prepared by a solvent casting process. After drying, the composite was extruded to form a tubular construct. The salt particles in the construct were then leached out leaving a conduit with an open-pore structure. PLGA was studied as a model polymer to analyze the effects of salt weight fraction, salt particle size, and processing temperature on porosity and pore size of the extruded conduits. The porosity and pore size were found to increase with increasing salt weight fraction. Increasing the salt particle size increased the pore diameter but did not affect the porosity. High extrusion temperatures decreased the pore diameter without altering the porosity. Greater decrease in molecular weight was observed for conduits manufactured at higher temperatures. The mechanical properties of both PLGA and PLLA conduits were tested after degradation in vitro for up to 8 weeks. The modulus and failure strength of PLLA conduits were approximately 10 times higher than those of PLGA conduits. Failure strain was similar for both conduits. After degradation for 8 weeks, the molecular weights of the PLGA and PLLA conduits decreased to 38% and 43% of the initial values, respectively. However, both conduits maintained their shape and did not collapse. The PLGA also remained amorphous throughout the time course, while the crystallinity of PLLA increased from 5.2% to 11.5%. The potential of seeding the conduits with cells for transplantation or with biodegradable polymer microparticles for drug delivery was also tested with dyed microspheres. These porous tubular structures hold great promise for the regeneration of tissues which require tubular scaffolds such as peripheral nerve, long bone, intestine, or blood vessel.     

Preparation and testing of cyclosporine microsphere and solution formulations in the treatment of polyarthritis in rats

We prepared a microencapsulated sustained-release formulation of cyclosporine A (CsA) and compared its efficacy to the solution formulation of cyclosporine A (Sandimmune, Sandoz) in an attempt to improve the treatment of rheumatoid arthritis. Microspheres containing cyclosporine were prepared with poly(lactic co-glycolic acid) (PLGA), a polymer in the submicron particle range of 0.22-0.8 micron. Studies were carried out to determine uptake rates and mechanisms of lymphocyte inhibition mediated by macrophages containing CsA microspheres in vitro. The results of these studies were used to establish whether lower doses of the microencapsulated cyclosporine could be used in in vivo studies in the polyarthritic rat model for rheumatoid arthritis. In vitro dissolution testing revealed that CsA was released extremely slowly from microspheres for up to 48 hr (0.002%). Radiolabeled 3H CsA was incorporated into some PLGA microspheres or the microspheres were labeled using a 99mTc radioligand when needed, and radiolabeling efficiency was consistently above 50%. Uptake studies at various microsphere-to-macrophage ratios (1:1, 1:5, 1:10) were carried out using 99mTc radiolabeled microspheres and macrophages obtained from normal and polyarthritic rats. Normal macrophages behaved significantly differently from arthritic macrophages throughout the study. Arthritic macrophages cause increased amounts of CsA to be released (68% of the dose) into the culture medium past 24 hr compared to normal macrophages (48% of the dose). This factor may account for the significantly increased inhibition (68.2%) of mixed lymphocyte culture proliferation in the presence of arthritic macrophages containing CsA-loaded PLGA microspheres over normal macrophages (48.2%) that were pre-exposed to the same microsphere dose. The equivalent quantity of CsA as that contained in the microspheres when placed in solution or the same quantity of blank PLGA microspheres caused decreased levels of lymphocyte inhibition when compared to the effects of CsA microspheres in macrophages of normal cells, but significantly decreased levels of inhibition in arthritic cells. From the in vivo studies, it is evident that CsA microspheres, even at low dose levels, were highly effective in inhibiting polyarthritis in rats.     

Stabilization of 10-hydroxycamptothecin in poly(lactide-co-glycolide) microsphere delivery vehicles

PURPOSE: The purpose of this study was to investigate the potential of poly(lactide-co-glycolide) (PLGA) microspheres to stabilize and deliver the analogue of camptothecin, 10-hydroxycamptothecin (10-HCPT). METHODS: 10-HCPT was encapsulated in PLGA 50:50 microspheres by using an oil-in-water emulsion-solvent evaporation method. The influence of encapsulation conditions (i.e., polymer molecular weight (Mw), polymer concentration, and carrier solvent composition) on the release of 10-HCPT from microspheres at 37 degrees C under perfect sink conditions was examined. Analysis of the drug stability in the microspheres was performed by two methods: i) by extraction of 10-HCPT from microspheres and ii) by sampling release media before lactone--carboxylate conversion could take place. RESULTS: Microspheres made of low Mw polymer (inherent viscosity 0.15 dl/g) exhibited more continuous drug release than those prepared from polymers of higher Mw (i.v. = 0.58 and 1.07 dl/g). In addition, a high polymer concentration and the presence of cosolvent in the carrier solution to dissolve 10-HCPT were both necessary in the microsphere preparation in order to eliminate a large initial burst of the released 10-HCPT. An optimal microsphere formulation released 10-HCPT slowly and continuously for over two months with a relatively small initial burst of the released drug. Both analytical methods used to assess the stability of 10-HCPT revealed that the unreleased camptothecin analogue in the microspheres remained in its active lactone form (> 95%) over the entire 2-month duration of study. CONCLUSIONS: PLGA carriers such as those described here may be clinically useful to stabilize and deliver camptothecins for the treatment of cancer.     

Characterization of poly(glycolide-co-D,L-lactide)/poly(D,L-lactide) microspheres for controlled release of GM-CSF

PURPOSE: This study describes the preparation and characterization of a controlled release formulation of granulocyte-macrophage colony-stimulating factor (GM-CSF) encapsulated in poly(glycolide-co-D,L-lactide) (PLGA) and poly(D,L-lactide) (PLA) microspheres. METHODS: GM-CSF was encapsulated in PLGA/PLA microspheres by a novel silicone oil based phase separation process. Several different blends of PLGA and low molecular weight PLA were used to prepare the microspheres. The microspheres and the encapsulated GM-CSF were extensively characterized both in vitro and in vivo. RESULTS: Steady release of GM-CSF was achieved over a period of about one week without significant "burst" of protein from the microspheres. Analysis of microsphere degradation kinetics by gel permeation chromatography (GPC) indicated that low molecular weight PLA enhanced the degradation of the PLGA and thereby affected release kinetics. GM-CSF released from the microspheres was found to be biologically active and physically intact by bioassay and chromatographic analysis. Analysis of serum from mice receiving huGM-CSF indicated that the GM-CSF was biologically active and that a concentration of greater than 10 ng/mL was maintained for a period lasting at least nine days. MuGM-CSF was not detected following in vivo administration of muGM-CSF microspheres. The tissues of mice receiving muGM-CSF microspheres were characterized by infiltration of neutrophils, and macrophages which were in significant excess of those found in mice administered with placebo controls (i.e. microspheres without GM-CSF). CONCLUSIONS: This study demonstrates the influence of formulation parameters on the encapsulation of GM-CSF in PLGA/PLA microspheres and its controlled release in biologically active form. The intense local tissue reaction in mice to muGM-CSF microspheres demonstrates the importance of the mode of delivery on the pharmacologic activity of GM-CSF.     

Treatment of relapsed adult acute lymphoblastic leukemia with fludarabine and cytosine arabinoside followed by granulocyte colony-stimulating factor (FLAG-GCSF)

The aim of the present study was to evaluate the efficacy of the combination of fludarabine 30/mg/m2 + cytarabine 2g/m2 followed by the administration of G-CSF to achieve a complete remission (CR) in patients with relapsed acute lymphoblastic leukemia (ALL). We treated twelve patients in first relapse, overall 10 patients achieved a second CR, one patient showed resistant disease and one patient died during remission induction. The regimen was well tolerated and we observed a short period of neutropenia with a low incidence of myelosuppression-associated problems. Eight patients in second CR received the same chemotherapeutic regimen as consolidation used for the reinduction. In six patients the chemotherapeutic regimen was well tolerated, two patients died, (cerebral hemorrhage in one patient and sepsis in the other). In conclusion the combination of fludarabine, cytarabine and G-CSF has significant antileukemic activity and non hematological toxicities were acceptable. The addition of G-CSF reduced the period of neutropenia obtaining a low incidence of myelosuppression-associated problems.     

A novel surgical glue composed of gelatin and N-hydroxysuccinimide activated poly(L-glutamic acid): Part 1. Synthesis of activated poly(L-glutamic acid) and its gelation with gelatin

Although fibrin glue has been widely used as a surgical adhesive, its components, fibrinogen and thrombin, obtained from human blood are not completely free from the risk of virus infection due to acquired immune deficiency and hepatitis. Recently, we have reported that a polymer pair composed of gelatin and poly(L-glutamic acid) (PLGA) promptly forms a gel and can firmly bond to soft tissues when crosslinked with the aid of water-soluble carbodiimide (WSC). The present study was undertaken to design a new PLGA-gelatin glue without using WSC. Two kinds of PLGA with molecular weights of 71 and 22 kDa were employed to prepare N-hydroxysuccinimide (NHS) activated derivatives. The NHS-activated PLGA could be synthesized at high yields and was found to be stable for an extended time without losing the ability to crosslink with gelatin when stored under a dry-cold condition. This NHS-activated PLGA could spontaneously form a gel with gelatin in an aqueous solution within a short time, comparable to a commercial fibrin glue, when gelation was allowed to proceed at pH 8.3. The NHS-activated PLGA prepared from PLGA with the molecular weight of 22 kDa could be readily dissolved at high concentrations and its ability to form a gel was maintained for more than 10 min when an acidic 8% NHS-activated PLGA solution was used. The bonding strength of PLGA gelatin glues with natural tissue was higher than that of fibrin glue. These findings strongly suggest that this combination of gelatin and NHS-PLGA is very promising as a surgical adhesive and may possibly replace fibrin glues prepared from human blood components.     

Influence of immunosuppression on the action of antimycobacterial drugs in experimental tuberculosis. I. Effects of isoniazid, rifampicin and streptomycin on the survival of tuberculous mice immunosuppressed by azathioprine (Imuran)

The influence of the host immunosuppression on antimycobacterial effects of isoniazid, rifampicin or streptomycin was studied on animal models. Differences in survival rates of mice influenced or uninfluenced by azathioprine (Imuran) and exposed to six applications of antituberculous drugs (given once a day in the monotherapy) were statistically evaluated. The dose-dependent antimycobacterial effects of rifampicin or isoniazid were not significantly altered by the immunosuppression of the host. In contrary to that definite dose-dependent effect of streptomycin, observed in azathioprine-uninfluenced mice, cannot be confirmed in immunosuppressed mice in which no effect of streptomycin on the survival of tuberculous mice could be estimated.     

HLA-A towards a high-resolution DNA typing

PURPOSE: This study assessed the soft tissue changes produced by the placement of hard tissue replacement (HTR) polymer chin implants for augmentation genioplasty and evaluated the dimensional stability as well as any bony changes associated with the implants. PATIENTS AND METHODS: The study group consisted of 18 patients (3 males, 15 females) with an average follow-up of 21.5 months (range, 12 to 44 months). All implants were placed through an intraoral incision and stabilized to the symphysis with a single 2.0-mm diameter titanium screw. Preoperative, postoperative, and long-term cephalometric radiographs were analyzed for changes in soft tissue thickness in the chin region, implant stability, and the presence of bone resorption. RESULTS: The net hard tissue chin augmentation achieved averaged 6.0 mm (range, 4.5 to 9 mm). Average preoperative soft tissue thickness was 12.1 mm (range, 11 to 14.5 mm) and postoperatively it was 10.6 mm (range, 10 to 13.5 mm). The average increase in soft tissue projection was 77.6% (range, 71.4% to 83.3%) of the implant thickness. There was no radiographic evidence of implant migration or bony resorption beneath the implant. CONCLUSIONS: HTR implants appear to be a predictable means of augmenting the chin, providing the desired aesthetic change, without causing resorption of underlying bone.     

Thalamo-cortical interactions modeled by weakly connected oscillators: could the brain use FM radio principles?

Effects of drug content and medium pH on the release of papaverine (PAP) from biodegradable poly(l-lactic acid) [P(L)LA] matrix were investigated to reveal the predominant factors affecting the two-stage diffusion-controlled release mechanism. A drug-dissolved cylindrical matrix (rod; 10 mmx1 mm diameter) was prepared by heat compression method. In the case of a PAP content below 10%, pH was found to have a strong effect on the release rate, and drug content was found to have no effect on the release profile. The release profile consisted of two sequential diffusion stages due to P(L)LA transformation from amorphous to the semicrystalline state prior to release. In the first release stage PAP diffused through the swollen matrix. The release accelerated with increasing medium pH due to an increase in water content in the acidic P(L)LA rod. In the second release stage PAP diffused through the water-filled micropores developed as a result of the polymer crystallization. On the assumption that the drug partition between the polymer and the medium in the micropores affects the diffusion and the partition is controlled by pH, we derived a modified diffusion kinetic equation. The observation that the release decelerated with increasing medium pH can be explained by the derived equation as resulting from the increase in the drug partition to the polymer. In the case where the rods contained more than 15% of PAP, the drug precipitated out as crystals during release. Accordingly, these rods showed a slower release.     

Survivorship analysis of DKS instrumentation in the treatment of spondylolisthesis

This retrospective study analyzed the survivorship of DKS instrumentation and the clinical outcomes in 185 patients with spondylolisthesis. These patients were treated with Zielke DKS instrumentation for a mean followup period of 3.5 years. Eight (4.3%) patients had late removal of implants, 25 (14%) had rod breakage, three (1.7%) had screw breakage, and 16 (8.7%) had nut loosening. The survivor rate of DKS instrumentation was 96% within 3 months after operation, 80% at 2 years, and 61% at 5 years after surgery. One hundred sixty-three (88%) patients had solid posterolateral fusion, and 167 (90%) patients had good to excellent results. Adjacent instability developed in 18 (9.7%) patients. Although Zielke DKS instrumentation has a smaller rod and relatively insecure locking system between the rod and screw, it is an effective implant for the treatment of spondylolisthesis.     

Multidrug-resistant tuberculosis. 3. Epidemiology of drug-resistant tuberculosis in Japan

In Japan, the frequency of drug-resistant tuberculosis has been investigated every 5 years since 1950s and increase of initial and acquired drug resistance has not been observed. However, the mathematical model analyse of time trend of prevalence of drug-resistant tuberculosis and frequency of initial drug resistance in Korea shows that there is little difference of infectivity and/or proportion of clinical breakdown between susceptible bacilli and resistant ones. The prognosis of isoniazid (INH) and rifampicin (RFP) resistant tuberculosis cases in Fukujuji Hospital was investigated. 367 cases including 50 initial drug resistant cases were analyzed with life table analysis. 50% of all cases and 70% of initial drug resistant cases became negative, 13% of all cases and 4% of initial drug resistant cases remained as positive, 37% of all cases and 27% of new cases died. Among cases who did not convert negative within one year, 41% of all cases and 34% of initial drug resistant cases died. The prognosis of INH and RFP resistant tuberculosis cases were still not satisfactory.     

The potentiation of the effect of radiation treatment by intratumoral delivery of cisplatin

PURPOSE: To compare potentiation of the effects of acute or fractionated radiation by cisplatin when the drug was delivered intratumorally by implanted biodegradable polymer, by intraperitoneal injection, or by intraperitoneal osmotic pump. METHODS AND MATERIALS: Radiation was delivered to a mouse tumor (RIF-1) either in a single dose or in a fractionated regime in conjunction with cisplatin delivered either as a bolus injection, with an osmotic pump, or with a biodegradable polymer rod containing cisplatin. The osmotic pump was implanted in the intraperitoneal cavity of the mouse while the polymer implants were placed directly in the tumor. As the polymer degrades, the drug is released at the treatment site leading to high local concentrations. The osmotic pump, in contrast, leads to prolonged systemic exposure to the drug at low concentrations. Tumor growth delay (TGD) was used as an endpoint in these experiments. RESULTS: The most effective treatment protocol, in terms of potentiating the effects of radiation was cisplatin delivered by polymer implanted 2 days before an acute dose of radiation (growth modification factor [DMF] = 2.2). Comparison of single and multifraction regimes where polymer implant was on the same day as the commencement of treatment showed greater potentiation of the effect of fractionated than of acute radiation treatment with the DMF for fractionated treatment remaining relatively constant (1.5-1.9) for 5, 8, and 12 fraction treatments. Cisplatin delivered via the osmotic pump did not deliver a high enough dose of cisplatin to produce therapeutic effect in this mouse tumor model and had little impact on response to treatment. CONCLUSIONS: Our results indicated that cisplatin delivered intratumorally by biodegradable polymer implant was effective in potentiating the effect of both acute and fractionated radiation. For the fractionated treatments the effect was maintained with increasing fraction numbers and treatment time.     

CpG island methylation and promoter usage in the parathyroid hormone-related protein gene of cultured lung cells

Poly-D,L-lactide (PDLLA) and polylactide-co-glycolide (PLGA) microspheres containing thymopentin have been prepared by a water-in-oil-in-water-emulsion/solvent evaporation technique. The goal is to stabilize the active compound thymopentin, and to prolong its therapeutic activity, by embedding the drug in a polymeric matrix. The microspheres obtained have been characterized for their morphology and drug content. In-vitro dissolution tests have been performed on the microspheres. Results show that the type of polymer employed (PDLLA or PLGA) does not seem to affect microsphere morphology, while in-vitro dissolution profiles are greatly influenced by the composition of polymer matrix. Ex-vivo evaluation of PLGA microspheres performed on mouse thymocites shows that biological activity of Thymopentin is maintained after loading into PLGA microspheres.     

Detection of aneurysm in subarachnoid hemorrhage--CT angiography vs. digital subtraction angiography

The purpose of this study was to investigate the feasibility and the efficacy of administering tirapazamine by a slow-releasing polymer disc that was implanted interstitially into a U251 (human glioblastoma multiforme) tumor grown in nude mice. Tumor-bearing animals, with a tumor nodule 0.8 cm3 in size, were distributed to groups receiving combinations of empty or drug-containing polymer implants in the tumor or contralateral leg, intraperitoneal (i.p.) drug, and/or irradiation. The drug (i.p.) alone (14 mg/kg x6) or in combination with tumor drug implant (2 mg) did not significantly increase the tumor volume doubling time compared to that of control animals. Given with 12 Gy of irradiation in twice a day 2-Gy fractions, combined i.p. drug and tumor drug implant significantly delayed tumor growth compared to irradiation alone, which was not achieved with either drug treatment alone added to irradiation. Toxicity, as manifested by transient weight loss, was primarily seen in animals receiving radiation and i.p. tirapazamine. These results indicated that a slow-releasing tirapazamine disc can be produced and the addition of an interstitially implanted tirapazamine disc further increased the effectiveness of i.p. tirapazamine.     

Acute promyelocytic leukemia: all-trans retinoic acid (ATRA) along with chemotherapy is superior to ATRA alone

This study was conducted to compare the results of treatment of acute promyelocytic leukemia (APL) with all-trans retinoic acid alone (ATRA) or a combination therapy of ATRA followed by chemotherapy. Forty-three patients treated between February 1992 and February 1996 were included in this study. Eighteen patients were treated with ATRA alone and 25 patients were treated with ATRA followed by chemotherapy. The cytogenetic analysis was done in 41 patients at presentation, following treatment, and at follow-up. A complete response (CR) was achieved in 13 (72%) patients on ATRA and 19 (76%) on ATRA followed by chemotherapy. Eleven of 13 patients with response to ATRA alone relapsed with median survival of eight months (range, 1 to 28). One patient died of hepatitis in CR and one patient is alive 2 years after diagnosis. In the combination therapy arm, 10 patients are in CR with a median follow-up of 22 months (range, 6 to 56 months). After achieving a CR, four patients died due to infections during chemotherapy therapy, and only 5 of 19 patients have relapsed. Major cytogenetic response was seen in 8 of the 10 patients in whom cytogenetic data was available after treatment with ATRA at the time of remission. Similarly, 13 of 15 for whom data was available showed a major cytogenetic response after treatment with ATRA plus chemotherapy. Prior to relapse, 80% of the patients had an increase in the percentage of t(15;17) cells in the marrow. Patients with a complete hematological response but no cytogenetic response relapsed within six months. Ten patients died prior to response evaluation. Two patients who received ATRA died of retinoic acid syndrome, one of pneumonia, and one of intracranial hemorrhage. Of the six patients on ATRA and chemotherapy, four died of retinoic acid syndrome (RAS), one of intracranial hemorrhage, and one of left ventricular failure. Only one patient is alive at 24 months following treatment with ATRA alone. The relapse-free survival is 42% at four years for patients treated with ATRA followed by chemotherapy. This trial is a historical comparison of ATRA alone and ATRA with subsequent combination chemotherapy. Nonetheless, the trial shows a significant improvement in the event free survival of patients receiving chemotherapy as consolidation following ATRA.     

Microencapsulation of hepatitis B core antigen for vaccine preparation

PURPOSE: To prepare poly(lactide-co-glycolide)(PLGA) microspheres containing recombinant hepatitis B core antigen (HBcAg; Mw = 3,600,000) by a w/o/w emulsion/solvent evaporation method and evaluate the possibility of this system as a potent long-acting carrier for hepatitis B core antigen in mice. METHODS: Various additives had been incorporated in the internal aqueous phase during the process of microencapsulating HBcAg, HBcAg antigenicity in the medium extracted from the prepared microspheres were measured by ELISA. Shape confirmation of the HBcAg antigen was performed by a sucrose gradient velocity centrifugal technique. For in vivo study, prepared microspheres were administered subcutaneously to Balb/C mice, and the serum IgG level was determined by ELISA. RESULTS: The inactivation of HBcAg by methylene chloride was dramatically reduced by the addition of gelatin (4-8% (w/v)) to the internal aqueous phase during the preparation. Further improvement of the loading efficiency to almost 61% resulted with cooling (4 degrees C). The prepared microspheres (4.27 microm+/-1.23 microm) containing 0.15% HBcAg displayed burst release (50-60% within 2 days). In subcutaneous inoculation, the adjuvant effect of PLGA microspheres was almost the same as that of the complete Freund's adjuvant. Whereas oral inoculation using the microspheres was not effective. CONCLUSIONS: The pH of the added gelatin seemed to be the key to the stabilization of HBcAg from various stability tests and CD spectrum study. Finally, the possibility of using this system as a potent long-acting hepatitis B vaccine was demonstrated.