Effects of 1-hydroxyethylidene-1,1 bisphosphonate and (chloro-4 phenyl) thiomethylene bisphosphonic acid (SR 41319) on the mononuclear cell factor-mediated release of neutral proteinases by articular chondrocytes and synovial cells

Effects of low and high dose intraarticular tiludronate on synovial fluid and clinical variables in healthy horses-a preliminary investigation

To determine effects of intraarticularly administered tiludronate on articular cartilage in vivo, eight healthy horses were injected once with tiludronate (low dose tiludronate [LDT] 0.017 mg, n = 4; high dose tiludronate [HDT] 50 mg, n = 4) into one middle carpal joint and with saline into the contralateral joint. Arthrocentesis of both middle carpal joints was performed pre-treatment, and 10 min, 24 h, 48 h, 7 and 14 days after treatment. Synovial nucleated cell counts and total solids, tiludronate, sulfated glycosaminoglycan (sGAG), chondroitin sulfate 846 epitope (CS-846, a measure of aggrecan synthesis), and collagen type II cleavage neoepitope (C2C) concentrations were determined. Histologic analysis of joint tissues and sGAG quantitation in cartilage was performed at 14 days in HDT horses. Data were analyzed by repeated measures non-parametric ANOVA and Wilcoxon signed-rank test. High dose tiludronate administration produced synovial fluid tiludronate concentrations of 2,677,500 ng/mL, exceeding concentrations that were safe for cartilage in vitro, and LDT administration produced synovial fluid concentrations of 1,353 ng/mL, remaining below concentrations considered potentially detrimental to cartilage. With HDT, synovial fluid total solids concentration was higher at 24 h and 7 days and sGAG concentration was higher at 48 h, compared to control joints. Synovial fluid CS-846 concentration was increased over pre-treatment values in HDT control but not in HDT treated joints at 24 and 48 h. All joints (HDT and LDT control and treated) showed a temporary decrease in synovial fluid C2C concentration, compared to pre-treatment values. Histologic features of articular cartilage and synovial membrane did not differ between HDT treated and control joints. High dose tiludronate treatment caused a transient increase in synovial total solids and temporarily increased proteoglycan degradation in cartilage. Although clinical significance of these changes are questionable, as they did not result in articular cartilage damage, further investigation of the safety of intraarticular HDT in a larger number of horses is warranted.

Concentration-dependent effects of tiludronate on equine articular cartilage explants incubated with and without interleukin-1β

OBJECTIVE

To determine concentration-dependent effects of tiludronate on cartilage explants incubated with or without recombinant equine interleukin-1β (rEq IL-1).

SAMPLE

Articular cartilage explants from the femorotibial joints of 3 young adult horses.

PROCEDURES

Cartilage explants were incubated with 1 of 6 concentrations (0, 0.19, 1.9, 19, 190, or 1,900 mg/L) of tiludronate and with or without rEq IL-1 (0.01 ng/mL) for 96 hours. Prostaglandin E(2) (PGE(2)) concentrations in culture medium and explant digests were analyzed via PGE(2) enzyme immunoassay. Sulfated glycosaminoglycan (sGAG) concentrations in culture medium were quantified via 1,9-dimethylmethylene blue assay. Chondrocyte apoptosis in paraffin embedded explant sections was measured via terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay. Relative gene expression of matrix metalloproteinases (MMPs), interleukin (IL)-6, and IL-8 was determined via the comparative cycle threshold method.

RESULTS

rEq IL-1 increased PGE(2) concentration, sGAG release from explants, chondrocyte apoptosis, and MMP gene expression. Lower tiludronate concentrations reduced rEq IL-1-induced sGAG release and chondrocyte apoptosis, whereas the higher tiludronate concentrations increased sGAG release and chondrocyte apoptosis. At the highest tiludronate concentration evaluated, IL-8 gene expression was increased independent of whether rEq IL-1 was present.

CONCLUSIONS AND CLINICAL RELEVANCE

Tiludronate had biphasic concentration-dependent effects on cartilage explants that were independent of PGE(2) secretion or MMP gene expression. Low tiludronate concentrations had some chondroprotective effects, whereas high tiludronate concentrations were detrimental to equine articular cartilage. Administration of tiludronate intra-articularly to horses may be detrimental, dependent on the dose used. In vivo studies are needed before intra-articular tiludronate administration to horses can be recommended.

Tiludronate infusion in the treatment of bone spavin: a double blind placebo-controlled trial

REASONS FOR PERFORMING STUDY

Tiludronate regulates bone remodelling through a decrease of the resorptive process and should therefore ameliorate the remodelling processes active in osteoarthritis of the distal tarsal joints ('bone spavin') and alleviate pain associated with abnormal bone lysis.

OBJECTIVE

To confirm the efficacy of tiludronate, administered as a single infusion at a dose of 1 mg/kg bwt, in the treatment of bone spavin in the horse.

METHODS

A double blind placebo controlled trial on 108 clinical cases of bone spavin was undertaken. The lameness score of the lamest limb was assessed following distal tarsal analgesia of the contralateral limb and followed-up using the same procedure throughout the study. Bone spavin in the lamest limb was confirmed by distal tarsal analgesia and radiography. Horses were treated at Day 0 and reassessed 60 days later after controlled exercise. A second nonblinded treatment was given to unresponsive horses and all horses were re-examined at Day 120. Exercise levels were recorded at each examination.

RESULTS

Eighty-seven horses completed the trial as per the protocol. The tiludronate horses were significantly less lame than the placebo horses (P = 0.0318). Horses treated at Day 60 with tiludronate showed further improvement in lameness at Day 120 (P = 0.0096 and P = 0.0034 for horses treated with tiludronate and placebo at Day 0, respectively). The only significant difference in radiographic findings between tiludronate and placebo was for presence of periarticular osteophytes (P = 0.006).

CONCLUSIONS

Tiludronate treatment is proven to be effective in bone spavin in horses in association with a controlled exercise programme.

CLINICAL RELEVANCE

Tiludronate in combination with controlled exercise offers an alternate medical treatment for bone spavin.

Extra-skeletal effects of bisphosphonates

Bisphosphonates are pharmacological agents which are currently used both in osteoporosis than in other pathological conditions characterised by an increased bone resorption, such as Paget's disease of bone, malign hypocalcaemia during myeloma, osteolytic bone metastasis and fibrous dysplasia of bone. The most important biological effect of bisphosphonates is the reduction of bone remodelling through the inhibition of osteoclastic activity, but there are many clinical and experimental evidences of extra-skeletal biological effects of bisphosphonates. It has been shown that bisphosphonates exert their effects not only on bone tissue cells, but also on those of the immune system with an "immuno-modulating" effect, influencing the production of pro- and anti-inflammatory cytokines and changing the molecular expression involved in the immune processes and anti-inflammatory response. Although the available data are conflicting, there are several reports concerning the beneficial effects of bisphosphonates in controlling the progression of chronic joint inflammatory diseases, suggesting a wider use for these therapeutic agents in clinical practice.

The effect of bone remodeling inhibition by zoledronic acid in an animal model of cartilage matrix damage

OBJECTIVE

The purpose of this work was to test the effect of inhibition of bone remodeling, through the use of the bisphosphonate, zoledronic acid, on cartilage matrix damage in an animal model of cartilage matrix damage.

DESIGN

New Zealand white rabbits were divided into four groups for treatment purposes: (1) untreated controls; (2) injected into one knee joint with the cartilage matrix degradation enzyme, chymopapain; (3) injected into one knee joint with chymopapain and also given subcutaneous injections of the bisphosphonate, zoledronic acid, three times per week until sacrifice at either day 28 or 56 post-chymopapain-injection; (4) received only the zoledronic acid injections. At sacrifice, the knee joints were examined grossly and histologically, and biochemically for proteoglycan content. Urine samples were analysed, at intervals, for levels of collagen cross-links which are biochemical markers of cartilage and bone.

RESULTS

Animals receiving both intraarticular chymopapain injections and subcutaneous zoledronic acid injections displayed a significantly lower degree of grossly and histologically detectable cartilage degeneration on the tibial articular surfaces (the articular surface displaying the greatest degree of degeneration) than did animals only receiving the chymopapain injections. In addition, urinary levels of collagen cross-links for bone and cartilage were significantly higher in those animals only receiving chymopapain injections.

CONCLUSION

The bone resorption observed after chymopapain injection into the rabbit knee joint can be inhibited through the use of the bisphosphonate, zoledronic acid. Furthermore, zoledronic acid does not increase the level of cartilage degeneration and appears to provide some level of chondroprotection in this model.

Tiludronate. A new treatment for an old ailment: Paget's disease of bone

Tiludronate ([[(4-chlorophenyl)thio]-methylene]-bis-phosphonate, ClPsMBP, Skelid, Sanofi) is a powerful inhibitor of bone resorption which has been shown to be a highly effective and safe agent for the treatment of Paget's disease of bone. Preclinical studies in vitro and in vivo have demonstrated a dose-dependent inhibitory effect on bone resorption. Unlike other bisphosphonates, tiludronate does not seem to interfere with the differentiation of osteoclasts or with their access to bone mineral. Bone tolerance studies indicate that tiludronate has an excellent therapeutic window. Thus, at the doses which induce a substantial inhibition of bone resorption it neither causes an appreciable effect on mineralisation, nor impairs biomechanical bone resistance. New formulations of tiludronate (tablets) have a bioavailability of 6% (2-11%) when ingested under optimal conditions. The pharmacokinetic profile of tiludronate is linear. Approximately 50% of the absorbed dose is bound to bone and the rate of release from this site is limited by bone turnover. Several open uncontrolled, open randomised, and double-blind, placebo-controlled studies carried out in patients with active Paget's disease have demonstrated that tiludronate reduces bone pain and produces an intense and sustained biochemical response. 3-6 months after starting tiludronate therapy, serum alkaline phosphatase levels fall far more than 50% from baseline values, reaching normal values in a percentage of the cases ranging from 35-70%. At present, tiludronate, together with pamidronate and alendronate, appear to be the drugs of choice for first-line use in the management of relatively young patients at risk of having long-term complications, when long-lasting control of disease activity is required.

Effects of tiludronate and ibandronate on the secretion of proinflammatory cytokines and nitric oxide from macrophages in vitro

Bisphosphonates inhibit osteoclastic bone resorption and are used for the treatment of bone diseases. Some bisphosphonates, such as clodronate and tiludronate, can be incorporated into non-hydrolysable ATP analogues in cells, whereas the more potent anti-resorptive aminoalkylbisphosphonates are not metabolised. Furthermore, clodronate inhibits proinflammatory cytokine and nitric oxide (NO) secretion from activated macrophages in vitro and has anti-inflammatory properties in vivo, especially when delivered into cells by liposomes. By contrast, aminobisphosphonates can induce an acute phase response and fever in vivo, which appears to involve the induction of cytokine secretion. In this study we examined the effect of liposome-mediated intracellular delivery of one aminobisphosphonate, ibandronate, and one metabolizable bisphosphonate, tiludronate, on the secretion of inflammatory mediators. The intracellular uptake of bisphosphonates by macrophages was enhanced by a factor of 20-200 by using liposomes. Tiludronate dose-dependently inhibited both cytokine and NO secretion from activated macrophages, and liposomal tiludronate was more potent than the free drug. By contrast, ibandronate enhanced LPS-induced secretion of IL-1beta and IL-6 but did not affect TNFalpha or NO secretion at non-cytotoxic concentrations. The present results, together with our previous studies, strongly suggest that bisphosphonates can be grouped into those that are metabolised by cells and that are capable of inhibiting cytokine and NO secretion from macrophages, thus having potential anti-inflammatory properties, and those that are not metabolised but can actually enhance the production of cytokines following macrophage activation.

Inhibition of growth of Dictyostelium discoideum amoebae by bisphosphonate drugs is dependent on cellular uptake

PURPOSE

The aim of the study was to determine whether bisphosphonates are internalised by Dictyostelium amoebae and whether cellular uptake is required for their growth-inhibitory effects. Bisphosphonates inhibit growth of amoebae of the slime mould Dictyostelium discoideum, by mechanisms that appear to be similar to those that cause inhibition of osteoclastic bone resorption.

METHODS

Cell-free extracts prepared from amoebae that had been incubated with bisphosphonates were analysed by 31P-n.m.r, spectroscopy or ion-exchange f.p.l.c., to identify the presence of bisphosphonates or bisphosphonate metabolites respectively. The growth-inhibitory effect of bisphosphonates towards Dictyostelium amoebae was also examined under conditions in which pinocytosis was inhibited.

RESULTS

All of the bisphosphonates studied were internalised by Dictyostelium amoebae, probably by fluid-phase pinocytosis, and could be detected in cell-free extracts. Amoebae that were prevented from internalising bisphosphonates by pinocytosis were markedly resistant to the growth-inhibitory effects of these compounds. In addition, bisphosphonates encapsulated within liposomes were more potent growth inhibitors of Dictyostelium owing to enhanced intracellular delivery of bisphosphonates.

CONCLUSIONS

All bisphosphonates inhibit Dictyostelium growth by intracellular mechanisms following internalisation of bisphosphonates by fluid-phase pinocytosis. It is therefore likely that bisphosphonates also affect osteoclasts by interacting with intracellular, rather than extracellular, processes.

Analgesic effect of bisphosphonates on bone pain in breast cancer patients: a review article

Bisphosphonates exert their analgesic effect by several mechanisms. The long-term effects are probably due to osteoclast inhibition. The acute pain-relieving effect, which occurs within days or a week, is likely to be associated with the reduction of various potentially pain-producing substances. As regards pamidronate, several open, controlled studies have shown a significant effect on bone pain in 30-70% of breast cancer patients. The effects have been dose-dependent: a mean dose of 15 mg i.v./week is obviously suboptimal, whereas higher doses yield markedly better effects. The dose response is most evident at doses between 15 and 30 mg/week. Furthermore, the total dose per infusion is of interest: 30 mg every 2 weeks is an ineffective treatment, whereas 60 mg every 4 weeks is more effective. Thus, both the dose per week and the total dose per infusion are of importance in order to achieve optimal treatment. Patients with rapid progression of their disease require higher doses than patients with slow progression. Parenteral therapy is more effective than oral treatment. Both oral and parenteral clodronate exert a significant, positive effect on total skeletal morbidity and thus probably also on bone pain. Unfortunately, pain measurements have not been performed and evidence for pain reduction is indirect. Specific pain studies and studies of quality of life, with few exceptions, are, however, still lacking.

Efficacy and safety of drugs for Paget's disease of bone

Paget's disease of bone is characterized by an anarchic bone turnover starting with excessive resorption caused by structural and functional abnormalities involving osteoclasts. Calcitonin and bisphosphonates are now considered as the main therapeutic approaches for this disease. Daily parenteral administration of calcitonin to patients with Paget's disease of bone results in a significant fall in serum alkaline phosphatase and urinary hydroxyproline levels. This treatment has also been reported to be effective in relieving clinical symptoms of the disease, mainly bone pain. The drawbacks of injectable calcitonin have stimulated interest in alternative routes of delivery. Substantial evidence of calcitonin bioavailability and bioefficacy equivalent to those of parenteral administration is currently available for only two alternative routes: nasal spray and rectal suppository. Since many results have been published showing a dramatic effect of several bisphosphonates in Paget's disease of bone, nasal and rectal calcitonin are no longer considered as the treatments of choice in this condition. A major advantage of the use of bisphosphonates over calcitonin in Paget's disease is that biochemical and histologic suppression of disease activity may persist for many years after the cessation of treatment. Oral etidronate and intravenous pamidronate have been extensively used and have provided satisfactory benefits to the patient. Since the risk/benefit ratio of alendronate does not appear to be completely positive, it is likely that the future of treatment of Paget's disease of bone will be based on the oral formulation of the new bisphosphonates, including tiludronate, risedronate or dimethyl-pamidronate.

Effects of tiludronate on bone loss in paraplegic patients

Immobilization secondary to spinal cord injury is associated with a marked and rapid atrophy of trabecular bone (disuse osteoporosis). This is due to an early increase of osteoclastic bone resorption associated with a pronounced decreased osteoblastic bone formation. Bisphosphonates are antiosteoclastic compounds and they have been effective in preventing disuse osteoporosis. However, some of them also depress osteoblastic activity and may impair the mineralization process. Tiludronate was shown effective in reducing bone resorption in several metabolic bone diseases without inducing mineralization defects. Twenty paraplegic patients (6 females and 14 males) were randomly assigned to three groups: 6 patients entered the placebo group; 7 patients received tiludronate 200 mg/day; and 7 received 400 mg/day. Histomorphometric analysis was performed on transiliac bone biopsies before and after 3 months treatment. An insignificant decrease of bone volume was observed in the placebo group and the 200 mg group. In patients receiving 400 mg/day, a slight increase was noted. Osteoid parameters changed nonsignificantly in three groups although the 400 mg group exhibited a slight tendency to decrease osteoid volume and thickness. Eroded surfaces increased in all groups. The number of osteoclasts (identified histochemically by TRAP staining) increased in the placebo group but decreased in groups receiving tiludronate. Tiludronate appears effective in reducing bone resorption without impairing bone formation in a manner that preserved bone mass and bone cell coupling.

Effect of etodolac on prostaglandin E2 biosynthesis, active oxygen generation and bradykinin formation

The inhibitory actions of etodolac on prostaglandin (PG) E2 biosynthesis, active oxygen generation and bradykinin formation were compared with those of indomethacin, diclofenac Na, piroxicam, naproxen, ketoprofen and aspirin. The inhibitory action (IC50 5.35 x 10(-8) M) of etodolac on PGE2 biosynthesis in rabbit articular chondrocytes stimulated by interleukin-1 (IL-1) beta was about 1/5 that of indomethacin. The inhibitory action of etodolac on spontaneous PGE2 biosynthesis in rabbit gastric epithelial cells (RGEs) (IC50 2.27 x 10(-5) M) and Madin-Darby canine kidney cells (MDCKs) (IC50 4.54 x 10(-7) M) was much less than that in rabbit articular chondrocytes stimulated by IL-1 beta and about 1/19 and 1/9 that of indomethacin in rabbit gastric epithelial cells (RGEs) and Madin-Darby canine kidney cells (MDCKs), respectively. The inhibitory action of etodolac on active oxygen generation was similar to that of indomethacin and piroxicam, and more potent than that of naproxen, ketoprofen and aspirin. The inhibitory action of etodolac on bradykinin formation was the most potent among the seven anti-inflammatory drugs tested. Both etodolac and bromelain inhibited the inflammatory pain in concanavalin A-treated paws of rats in a dose-dependent manner, but indomethacin did not. These results indicate that etodolac is an anti-inflammatory drug which suppress IL-1 beta-stimulated PGE2 biosynthesis in rabbit articular chondrocytes, active oxygen generation and bradykinin formation. It has less suppressive action against spontaneous PGE2 biosynthesis in RGEs and MDCKs. Thus, etodolac is considered to be a safe anti-inflammatory drug for clinical use.

Effects of two novel bisphosphonates on bone cells in vitro

Bisphosphonates are now widely used in the treatment of bone diseases, particularly where there is uncontrolled bone resorption, as they are known to be potent inhibitors of osteoclasis. It is still unclear whether the bisphosphonates act by inhibiting osteoclast maturation or by blocking the mechanism of bone resorption, and little is known of their effects on osteoblasts. Recent studies with 3-amino-1, hydroxypropylidene-1,1-bisphosphonic acid (APD) in the treatment of osteolytic metastases in breast cancer have suggested that APD may affect osteoblasts directly. We have now investigated the effects of two novel bisphosphonates, CGP 47072 and CGP 42446A on osteoclastogenesis in fetal rat calvariae cultured on collagen gels and on human osteoblasts (hOB) cultured as explants from bone taken from patients at surgery. We also compared the action of these new bisphosphonates with that of APD, which at concentrations of 2.5 x 10(-6) M to 2.5 x 10(-10) M inhibited osteoclast recruitment, even when this was stimulated by conditioned medium from MCF7 breast cancer cells. This bisphosphonate was particularly potent if cultured with calvaria taken at 19 days gestation, when more immature osteoclast precursors are present. If calvariae from 20 days gestation were used, which contain more mature cells, it produced less inhibition. In contrast, CGP 42446A (2.5 x 10(-6) M to 2.5 x 10(-8) M) was more effective in inhibiting osteoclast maturation in calvariae from 20 days gestation than in those from 19 days. CGP 47072 had a similar pattern of effects but was less potent than either of the other two compounds. APD or CGP 42446A at 10(-5) M significantly inhibited hOB numbers and DNA synthesis, but lower concentrations had little effect. CGP 47072 did not inhibit human osteoblast replication. It is unlikely that these effects are due to calcium chelation, as none of these compounds mimicked results obtained with EDTA, which was effective only at 2.5 x 10(-6) M in reducing osteoclast size and 10(-4) M in human osteoblast cultures. These results demonstrate that all three bisphosphonates are able to inhibit osteoclast formation at low concentrations. APD may be able to influence less mature osteoclast precursors and CGP 42446A and CGP 47072 may exert their effects on the fusion of more mature precursor cells on the bone surface. At these concentrations, however, there is little or no effect on osteoblasts.

Efficacy and tolerability of a new formulation of oral tiludronate (tablet) in the treatment of Paget's disease of bone

We sought to assess efficacy and safety of a new oral formulation (tablet) of tiludronate in Paget's disease of bone. We studied 128 patients with Paget's disease in an open-label uncontrolled trial. Patients received a daily dose of 400 mg oral tiludronate (two tablets). Treatment was for 6 months. Serum alkaline phosphatase activity (SAP) and fasting urinary excretion of hydroxyproline/creatine (OH/Cr) were measured every 3 months, as were biochemical parameters reflecting renal, hepatic, and hematologic functions. Analgesic efficacy was self-evaluated from a visual analog scale (VAS). Statistical analysis revealed a significant reduction from baseline in SAP and OH/Cr levels, as well as VAS scores. In the whole population with evaluation under treatment, there was a reduction in initial SAP activity after 3 months (47.2 +/- 2.2%, mean +/- SEM) and 6 months (58.3 +/- 2.3%). In the population with SAP levels above twice the upper limit at inclusion and with evaluation at month 3 and month 6 (n = 96), the reduction in SAP levels was 49.3 +/- 2.4% after 3 months and of 59.5 +/- 2.6% after 6 months (ANOVA time effect, p = 0.0001). Aside from mild gastrointestinal disturbances, as experienced with other oral bisphosphonates, clinical tolerance was good. Exhaustive biochemical investigation failed to reveal significant toxicity of tiludronate tablets at the dose of 400 mg/day. The dose of 400 mg daily of this new formulation appears to be a satisfactory tiludronate regimen for the treatment of Paget's disease of bone.

Paget's disease of bone treated with a five day course of oral tiludronate

Chloro-4-phenyl thiomethylene bisphosphonate (tiludronate) is a new drug which can be used as an inhibitor of bone resorption. As it remains in bone for a long time, and as mineralisation defects have only been seen at doses much higher than those required to decrease osteoclastic activity, it could be given at high doses over a short period of time. Eighteen patients with Paget's disease of bone were randomly allocated to three therapeutic groups receiving respectively 600, 800, and 1200 mg/day tiludronate for five days. Serum alkaline phosphatase activity and the urinary hydroxyproline/creatinine ratio were quickly and drastically reduced in all three groups. A significant reduction of serum alkaline phosphatases and the hydroxyproline/creatinine ratio was still present six months after the five day therapeutic course, reflecting a sustained activity of tiludronate even after stopping treatment. Dose dependent short and long term reductions of bone turnover rate were observed. Biochemical assessment of haematological, renal, or hepatic tolerance did not show any toxicity of tiludronate. Fifty per cent of patients treated by a dose of 1200 mg/day reported gastrointestinal disturbances, however, making this dosage unsuitable for clinical practice.

Evaluation of the efficacy and safety of oral tiludronate in Paget's disease of bone. A double-blind, multiple-dosage, placebo-controlled study

OBJECTIVE

To assess the optimal dosage of oral tiludronate in Paget's disease of bone.

METHODS

We studied 149 patients with Paget's disease, in a double-blind, randomized, placebo-controlled trial. Patients were randomly assigned to 1 of 5 therapeutic groups: a daily dose of 100 mg, 200 mg, 400 mg, or 800 mg of oral tiludronate, or a placebo. Treatment was for 3 months, followed by 3 months of placebo-controlled followup. Serum alkaline phosphatase activity (SAP) and fasting urinary excretion of hydroxyproline/creatinine (OH/Cr) were measured monthly, as were biochemical parameters reflecting renal, hepatic, and hematologic functions. Analgesic efficacy was self-evaluated from a visual analog scale and a global pain index.

RESULTS

Statistical analysis revealed that beginning at a dosage of 200 mg/day, there was a direct dose-dependent effect on the reduction of SAP and OH/Cr levels. Reduction of SAP levels was clinically significant at a dosage of 400 mg (44.9 +/- 4.2% reduction at 90 days and 49.2 +/- 4.5% at 180 days, mean +/- SEM) and at 800 mg (53.4 +/- 5% at 90 days and 59.3 +/- 4.6% at 180 days). There was a significant reduction in pain in all groups, including the group taking placebo. In only those taking 800 mg/day of tiludronate was there a significant frequency of complete resolution of pain (versus placebo). Aside from mild gastrointestinal disturbances, as experienced with other oral bisphosphonates, clinical tolerance of all 5 regimens was good. Exhaustive biochemical investigations failed to reveal significant toxicity of tiludronate up to the 800-mg daily dose investigated.

CONCLUSION

Because of its significantly better antiresorptive effects and greater analgesic properties (compared with lower dosages), combined with the excellent clinical and biochemical tolerance, the 800-mg daily dose of tiludronate appears to be optimal for the treatment of Paget's disease of bone.

Association of collagenase and tissue inhibitor of metalloproteinases (TIMP) with hypertrophic cell enlargement in the growth plate

In the transition from proliferating to hypertrophic cell zones in the growth plate, there is an increased in chondrocyte cell volume and a corresponding decrease in collagen content to allow for cell enlargement. To substantiate our hypothesis that collagenase is responsible for these changes, growth plates from rats treated with bisphosphonate (HEBP) were compared histologically and biochemically with growth plates from normal and vitamin D and phosphate deficient (-VDP) rats. HEBP-treated rats developed an expanded hypertrophic cell zone (HCZ) characterized by the presence of two distinct populations of hypertrophic cells. The proximal hypertrophic cells were only 2-fold enlarged compared to the proliferating cells, whereas 1/6 of the distal hypertrophic cells were enlarged almost 5-fold and appeared morphologically identical with hypertrophic cells from normal and -VDP rats. The HEBP growth plates were divided into cross-sectional thirds and analyzed for active and latent collagenase. The juxta-metaphyseal (lower 1/3) cartilage contained 100% of the fully enlarged hypertrophic cells and appeared identical to those found in normal and -VDP growth plates, along with 81% of the active and 77% of the total collagenase. Collagenase and tissue inhibitor of metalloproteinases (TIMP) were measured in extracts of similarly divided tissues. The presence of true collagenas was confirmed by using [3H]-telopeptide-free collagen. TIMP levels were inversely related to the presence of active collagenase and cellular hypertrophy. Substantial levels of latent collagenase were found in the extracellular fluid at sites of active collagenolysis, but not in the fluid phase surrounding the 2-fold enlarged hypertrophic cells. It is postulated that increased amounts of active collagenase and insufficient levels of TIMP may account for the reduced collagen content seen in the lower HCZ of both -VDP and HEBP rickets. Unlike active collagenase, which remains localized by binding to collagen, latent enzyme is probably restricted in its mobility throughout the extracellular space by diffusion, itself, or the interstices of the extracellular matrix.

Treatment of Paget's disease of bone with (4-chloro-phenyl) thiomethylene bisphosphonate

Introduction of antiosteoclastic drugs, calcitonin and etidronate, has profoundly changed the treatment of active Paget's disease of bone. Nevertheless, the use of these drugs is limited in some patients by the occurrence of side-effects or by a resistance to therapy. We report the results of an open, nonrandomized study with a new bisphosphonate, (chloro-4 phenyl) thiomethylene bisphosphonate (Cl-TMBP), given orally to 35 patients with active Paget's disease of bone. At two different dosages this new bisphosphonate induced a significant decrease in disease activity. Patients receiving a mean dosage of 5 mg/kg/d (n = 14) showed a significant reduction of serum alkaline phosphatase levels to 43% of pretherapeutic values (from 499 +/- 91 to 214 +/- 41 IU/l) while hydroxyproline/creatinine ratio decreased to 43% of baseline (from 93 +/- 21 to 40 +/- 11). A second group of patients (n = 21) receiving a mean dosage of 11 mg/kg/d exhibited a similar response: serum alkaline phosphatase activity was reduced to 42% of initial values (from 1384 +/- 209 to 584 +/- 111 IU/l) while hydroxyproline/creatinine ratio fell to 48% of baseline (from 144 +/- 27 to 69 +/- 15). This was accompanied by a reduction in radionuclide uptake in pagetic areas. A prolonged beneficial effect was observed in most patients. In patients receiving the highest dosage significant reduction in serum calcium and rise in parathyroid hormone were observed. Otherwise no clinical or biological side-effect occurred throughout the study.

Bisphosphonates: a new class of drugs in diseases of bone and calcium metabolism

The geminal bisphosphonates are characterized by a PCP bond and are therefore analogs of pyrophosphate. They bind strongly to hydroxyapatite crystals and in vitro inhibit both crystal formation and dissolution. In vivo they inhibit soft tissue calcification and when given in large amounts also normal calcification. This effect is due to the inhibition of calcium phosphate crystal growth. Furthermore, the bisphosphonates are very potent inhibitors of bone resorption. The mechanism(s) of action is not yet known but is likely to be at a cellular level. The extent of the biological activity of each compound depends on the specific chemical structure, so that each individual bisphosphonate must be considered as a separate compound. The only common characteristic is the PCP group, which gives the compound its high affinity to bone. The individual effects, however, are determined by the side groups on the carbon atom. This opens interesting possibilities for the development of new compounds. No bisphosphonate analyzed so far can be degraded in vivo; all are either deposited in the skeleton, where they remain for years until the bone is destroyed, or are excreted in the urine. The high affinity for bone explains the specificity of the compounds for bone and the fact that they have relatively few nonosseous effects. Bisphosphonates are used in man to inhibit ectopic calcification, including dental tartar and ectopic ossification. Furthermore, they are used to inhibit bone resorption, especially in diseases such as Paget's disease and tumoral osteolysis. Finally, when linked to 99nTc, bisphosphonates are employed as bone scanning agents.