Pharmacological characterization of GLPG1972/S201086, a potent and selective small-molecule inhibitor of ADAMTS5

OBJECTIVE

A disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5) is a key enzyme in degradation of cartilage in osteoarthritis (OA). We report the pharmacological characterization of GLPG1972/S201086, a new, potent and selective small-molecule ADAMTS5 inhibitor.

METHODS

Potency and selectivity of GLPG1972/S201086 for ADAMTS5 were determined using fluorescently labeled peptide substrates. Inhibitory effects of GLPG1972/S201086 on interleukin-1α-stimulated glycosaminoglycan release in mouse femoral head cartilage explants and on interleukin-1β-stimulated release of an ADAMTS5-derived aggrecan neoepitope (quantified with ELISA) in human articular cartilage explants were determined. In the destabilization of the medial meniscus (DMM) mouse and menisectomized (MNX) rat models, effects of oral GLPG1972/S201086 on relevant OA histological and histomorphometric parameters were evaluated.

RESULTS

GLPG1972/S201086 inhibited human and rat ADAMTS5 (IC50 ± SD: 19 ± 2 nM and <23 ± 1 nM, respectively), with 8-fold selectivity over ADAMTS4, and 60->5,000-fold selectivity over other related proteases in humans. GLPG1972/S201086 dose-dependently inhibited cytokine-stimulated aggrenolysis in mouse and human cartilage explants (100% at 20 μM and 10 μM, respectively). In DMM mice, GLPG1972/S201086 (30-120 mg/kg b.i.d) vs vehicle reduced femorotibial cartilage proteoglycan loss (23-37%), cartilage structural damage (23-39%) and subchondral bone sclerosis (21-36%). In MNX rats, GLPG1972/S201086 (10-50 mg/kg b.i.d) vs vehicle reduced cartilage damage (OARSI score reduction, 6-23%), and decreased proteoglycan loss (∼27%) and subchondral bone sclerosis (77-110%).

CONCLUSIONS

GLPG1972/S201086 is a potent, selective and orally available ADAMTS5 inhibitor, demonstrating significant protective efficacy on both cartilage and subchondral bone in two relevant in vivo preclinical OA models.

Phasic production of urinary pyridinium crosslinks in mice: the effect of ovariectomy

Considerable sample to sample variability in deoxypyridinoline crosslink/creatinine (Dpd/CREAT) ratio values was confirmed when twice-weekly sampling for 77 days was performed in C57 mice. Analysis of samples from individual mice indicated that, in the majority of mice in a given group (54-67%), phasic changes occurred with periodic peaks as much as 4-5 times basal values. Alignment of peaks in the individual time courses of mice revealed a clear cyclic crosslink production (periodicity 12-14 days) for the population, although not all mice gave a peak in every case. Ovariectomy (OVX) (compared to sham-operated mice) increased mean values of crosslink production by either C57 or C57 x 129 F1 mice from about 10 days after operation with highest values between 21 and 35 days, and then a decrease in the difference between sham and OVX, particularly in C57 mice. Analysis of both time courses for individual mice and distribution curves of the data from groups of mice indicated that OVX consistently increased basal crosslink values (6-9 ratio units) with phasic peak values superimposed. The peak alignment analysis reinforced this observation. The influence of the background variability was avoided by pooling data over one cycle time and the use of nonparametric statistics, and the effect of OVX was analyzed in several strains of mice. Crosslink levels and phasic production declined with age but were also influenced by manipulation of the mice, suggesting that experimental conditions should be rigorously controlled when this urinary crosslink measure is used as a parameter in mouse models of OVX-induced osteoporosis.

Mechanisms involved in prostaglandin-induced increase in bone resorption in neonatal mouse calvaria

Prostaglandins (PG) E1, E2 and F2alpha induce bone resorption in isolated neonatal parietal bone cultures, and an associated increase in interleukin-6 (IL-6) production. Indomethacin had little effect on the response to PGE2, or the relatively non-selective EP receptor agonists 11-deoxy PGE1 and misoprostol, but blocked the effects of PGF2alpha and the F receptor agonist fluprostenol, indicating an indirect action via release of other prostaglandins. It is more likely that there is positive autoregulation of prostaglandins production in this preparation mediated via stimulation of F receptors. The effects of selective EP receptor agonists sulprostone (EP1,3) and 17-phenyl trinor PGE2(EP1), indicated the involvement of EP2 and/or EP4 receptors, which signal via cAMP. The relatively weak increase in IL-6 production by misoprostol (with respect to resorption) suggests that these responses are controlled by different combination of EP2 and EP4 receptors. The PKA activator, forskolin, induced small increases in bone resorption at lower concentrations (50-500 ng/ml) but a reversal of this effect, and inhibition of resorption induced by other stimuli (PTH, PGE2), at higher concentrations (0.5-5 microg/ml). IL-6 production was markedly increased only at the higher concentrations. The inhibitory effect of forskolin may be a calcitonin-mimetic effect. PMA induced both resorption and IL-6 production which were both blocked by indomethacin, indicating a role for PKC in the control of prostaglandin production.

Bone-resorbing cytokines from peripheral blood mononuclear cells after hormone replacement therapy: a longitudinal study

Conflicting results have been reported in several cross-sectional studies measuring cytokine production from adherent monocytes in pre- and postmenopausal women. Furthermore, the target cells for the action of estrogen are still debated. We therefore assessed in a longitudinal manner the cytokine production from different fractions of peripheral blood mononuclear cells (PBMC) cultured for 48 h. PBMC were obtained from 30 postmenopausal women before and after 6 months of hormone replacement therapy (HRT). Women were randomly allocated to two groups: an adherent PBMC group (n = 20) and a total PBMC group (n = 9). After 6 months of treatment, urinary pyridinoline levels were markedly decreased in both groups (353+/-24 vs 114+/-13 microg/mmol creatinine and 325+/-35 vs 164+/-31 microg/mmol creatinine respectively, p<0.01). Culture supernatants were assayed for interleukin 1beta (IL-1beta), interleukin 6 (IL-6), soluble IL-6 receptor (IL-6rs) and tumor necrosis factor alpha (TNF-alpha). In the adherent PBMC group, HRT induced a nonsignificant trend toward decreased levels of IL-1beta (35+/-10 vs 13+/-5 pg/ml), TNF-alpha (333+/-58 vs 222+/-30 pg/ml) and IL-6 (115+/-70 vs 17+/-10 pg/ml). In contrast, in the total PBMC group, HRT induced a consistent and dramatic decrease in levels of IL-1beta (104+/-22 vs 25+/-8 pg/ml), IL-6 (5950+/-1041 vs 1011+/-361 pg/ml), IL-6rs (148+/-33 vs 35+/-12 pg/ml) (p<0.01) and TNF-alpha (1468+/-315 vs 585+/-207 pg/ml, p = 0.05). We then evaluated whether HRT had the same effect in vitro. Adherent or total PBMC of 8 postmenopausal women were cultured with or without 10(-8) M 17beta-estradiol or tibolone for 48 h. Production of IL-1beta, TNF-alpha, IL-6 and IL-6rs was not affected by the presence of 17beta-estradiol or tibolone in cultures of these cell fractions. In conclusion, our data indicate that non-adherent PBMC could mediate the response to HRT. HRT may exert its action indirectly via noncirculating cells, as suggested by the absence of an in vitro effect.

The use of TNF family ligands and receptors and agents which modify their interaction as therapeutic agents

The earlier known TNF family cytokines have fairly wide physiological actions, mainly in inflammation and immune responses. It is now considered feasible to develop these large proteins themselves as therapeutic agents, but in addition, modular organisation of structures of biological proteins, and the identification of localised ligand-receptor interaction sites, allow rational design of smaller, preferably nonpeptide molecules which interfere with these protein:protein interactions. Neutralising anti-TNF antibodies and soluble TNF receptor preparations were shown to have striking anti-inflammatory activities in clinical studies, particularly in rheumatoid arthritis. As the TNF beta:TNFR1 co-crystal structure was the first in the family to be solved, rational drug design based on the ligand:receptor interaction sites is more advanced. Ligand mutations and a peptide sequence from TNF-alpha have given useful information regarding ligand-receptor interactions. Small peptide sequences from TNFR I which interact with the ligand have shown some activity in blocking the biological actions of TNF. The physiological activities of several recently-discovered ligands are more limited, giving possibilities for selective treatment of several diseases. For example, TRAIL can induce apoptosis in a wide range of tumour cells with little effects on normal tissues, both in vitro and in vivo. The co-crystal structure of TRAIL with one of its signalling receptors TRAILR 2 has been solved, opening the way to rational small molecule drug design. TRANCE (RANKligand) has modulatory effects on the dendritic cell:T cell interaction in immune responses. However, it plays a more major controlling role in the development of osteoclasts and their bone resorbing activity. In this way, it is a very interesting drug development target for the treatment of bone disorders such as osteoporosis. A recombinant secreted inhibitory receptor, osteoprotegerin (OPG), is in Phase 1 clinical trial for the treatment of hyper-resorptive bone diseases. However, OPG also blocks TRAIL and may not be sufficiently specific in long term therapy, but it is hoped that inhibitors of the interaction of TRANCE and its specific signalling receptor, RANK, can be rationally designed.

Factors influencing the effect of the soluble IL-6 receptor on IL-6 responses in HepG2 hepatocytes

The soluble IL-6 receptor (sIL-6R) can increase IL-6-induced signalling by forming a complex with IL-6 and membrane-bound gp130 (the receptor beta chain which transduces signals). The conditions affecting this response to sIL-6R were studied using fibrinogen release from HepG2 hepatocytes. Exogenous sIL-6R had no effect alone or in the presence of a submaximal concentration of IL-6, but increased responses to supramaximal IL-6 concentrations in a concentration-related manner. Dexamethasone increased the expression of the membrane IL-6R and endogenous sIL6R release, and increased responses to supramaximal but not submaximal IL-6 concentrations. The amount of endogenous sIL-6R released is relatively small and is unlikely to influence the effects of the exogenous sIL-6R. The observed concentration-related decrease in sIL-6R production in the presence of IL-6 may indicate internalization of ligand/receptor complexes. This would significantly decrease the amount of IL-6R (soluble or membrane) available for signalling and limit continued functional response later in the cultures. These data indicate that the major factor influencing responses to exogenous sIL-6R is an excess of IL-6 which is necessary to form complexes with the sIL-6R, which can then interact with gp130 to increase signalling.

Dual mechanisms of action of interferon-gamma in potentiating responses to LPS in mice: IL1, TNFalpha and IL6 production in serum and hypothermia

IFNgamma potentiates the production of serum cytokines and mortality induced by LPS, but these responses do not change in parallel, and the underlying mechanisms are not clear. Pretreatment of mice with 15 microg rrIFNgamma intraperitoneally (IP) resulted in potentiation of LPS-induced serum cytokine production and hypothermia, but these changes depended on the pretreatment time and did not occur in parallel. TNFalpha and IL1beta levels showed peak potentiation after 8-h-IFNgamma pretreatment which may result from a process of sensitization of mechanisms involved in LPS responses. IL6 levels were most markedly potentiated after 3- and 6-h-IFNgamma-pretreatment and hypothermia was markedly potentiated after 0-8 h pretreatments. These effects may result from an additional synergistic action of IFNgamma with other mediators when it is present at significant levels earlier after its injection, given that IFNgamma had little (hypothermia) or no effect (cytokines) alone. The degree of potentiation induced by 18-h-IFNgamma pretreatment was related to the dose of LPS, the maximum response having been increased. Two injections of IFNgamma at 42 and 18 h prior to LPS induced greater increases in TNFalpha and IL1beta production than 18-h pretreatment alone, but not in IL6 production or hypothermia. There may be a maximum level of IL6 production which was surpassed under these conditions. These findings suggest that a balance of sensitizing and synergistic actions of IFNgamma with other mediators such as IL1 and TNFalpha, are the major mechanisms underlying its potentiation of LPS responses in mice.

Selective enhancement of LPS-induced serum TNF-alpha production by carrageenan pretreatment in mice

1. Bacterial lipopolysaccharide (LPS)-induced increases in serum cytokines (TNF-alpha, IL-1 and IL-6) and hypothermia were studied in mice sensitized by carrageenan pretreatment and compared with mice sensitized with heat-killed P. acnes or IFN-gamma, all given IP at appropriate intervals (24 hr, 7 days and 12-18 hr, respectively) before LPS. 2. In mice with localized peritoneal inflammation induced by carrageenan, peak TNF-alpha levels (1.5-2 h after LPS) were markedly enhanced after both doses of LPS tested (50 and 200 microg/mouse IP). However, IL-1beta levels were not changed and IL-6 levels were decreased only after the higher dose of LPS. Hypothermia showed weak and inconsistent changes in carrageenan-sensitized mice. 3. IL-1beta levels in spleen lysates were higher but paralleled those in the serum, being increased in IFN-gamma-sensitized but not in carrageenan-sensitized mice. The levels of both TNF-alpha and IL-1beta were high in the peritoneum of carrageenan-sensitized mice, suggesting that the increased serum TNF-alpha did not emanate from the peritoneum. 4. In mice sensitized with the other two agents, as expected, the levels of all three cytokines increased, but peak levels were attained at the same times post-LPS (TNF-alpha: 1-1.5 hr; IL-1: 3-4 hr; IL-6: 3-4 hr). In addition, hypothermia was increased with both of these methods of sensitization. 5. The lack of consistent correlation of the levels of cytokines studied, particularly TNF-alpha, with the degree of hypothermia, raises questions as to their causative role in its induction in these models. 6. The mechanisms underlying these models of sensitization are clearly different, and further understanding of these mechanisms would aid in the interpretation of the effects of drugs in the models.

Increases in osteocalcin after ovariectomy are amplified by LPS injection: strain differences in bone remodelling

1. LPS (Escherichia coli serotype 0111:B4, 300 micrograms/mouse IP) increases serum osteocalcin in normal female C57B16 mice from 2 to 6 hr after its injection, with peak levels at 2-4 hr after LPS. 2. Both basal and LPS-stimulated serum osteocalcin were markedly inhibited by dexamethasone (10 mg/kg IP). 3. When observed 3 hr after LPS injection, serum osteocalcin was increased by ovariectomy (OVX) (with respect to sham-operated mice) and this increase was amplified in LPS-treated mice. This increase in osteocalcin was maximal 14 days after OVX, whereas urinary deoxypyridinoline cross-link levels were increased at all observation times (11-28 days). 4. All these changes were also observed in Balb/c mice but their magnitudes were consistently lower than those in C57B16 mice. 5. We propose that, (1) osteocalcin is a useful marker of bone remodelling in mice and the precision of measurement of changes in its levels after OVX is increased by LPS treatment and (2) C57B16 mice give greater magnitude and more consistent changes in both serum osteocalcin and urinary deoxypyridinoline cross-links after OVX, and may be a better strain for development of an in vivo model of post-menopausal osteoporosis.

Hypothermia as an indicator of the acute effects of lipopolysaccharides: comparison with serum levels of IL1 beta, IL6 and TNF alpha

1. Hypothermia was investigated as a parameter indicating the severity of the acute effects of lipopolysaccharides (LPS) in BALB/c mice, and was compared with the induction of serum levels of IL1 beta, TNF alpha and IL6. 2. Hypothermia induced by low doses of LPS (10-50 micrograms/mouse IP LPS E. coli 0111:B4) peaked at 2 hr after LPS and then either plateaued (50 micrograms) or declined. LPS, 100 and 300 mu, induced greater degrees of hypothermia that plateaued or continued to increase with time for 8 hr. Higher doses of LPS induced similar levels of hypothermia until 4 hr but then continued to increase markedly until 8 hr. 3. TNF alpha levels peaked early (1-2 hr) and declined rapidly, IL6 levels peaked at 3 hr and then declined slowly, and IL1 beta levels peaked at 4 hr, declined at lower doses of LPS, plateaued at higher doses and continued to slowly increase at highest doses. 4. The peak levels of the cytokines (IL1 beta up to 4 hr) and hypothermia (4 hr) increased in relation to the dose of LPS and maximum responses were apparently achieved in all cases at 300-1000 micrograms LPS. 5. A similar parallel between hypothermia and induction of cytokines was observed in C57BL6 and OF1 mice, which were good and poor responders to LPS, respectively, and with the more potent Shigella dysenteria LPS in BALB/c mice. 6. In conclusion, hypothermia is a useful parameter for indicating the strength of the acute effects of LPS. Further studies are necessary to determine whether or not the cytokines studied here play a causative role in hypothermia.