Selective inhibition of glutaminase by bis-thiadiazoles

Details Selective inhibition of glutaminase by bis-thiadiazoles Selective inhibition of glutaminase by bis-thiadiazoles

2001-08-10

2002-09-17

Spivack, Phyllis G. (Department: 1614)

Drug, bio-affecting and body treating compositions

Designated organic active ingredient containing

Having -c-, wherein x is chalcogen, bonded directly to...

Reexamination Certificate

active

06451828

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to selective and potent. inhibition of the enzyme glutaminase. Compounds are disclosed which efficiently inhibit glutaminase but which have no effect, at higher levels, on various mechanistically and functionally related enzymes. The compounds are useful for neuroprotection and in treatment of hepatic encephalopathy.
REFERENCES
Ahluwalia, G. S. et al., Metabolism and action of amino acid analog anti-cancer agents.
Pharmac. Ther.
46:243-271 (1990).
Almeida, A. F. et al., Maximal activities of key enzymes of glutaminolysis, glycolysis, krebs cycle and pentose-phosphate pathway of several tissues in mature and aged rats.
Int. J. Biochem.
21:937-940 (1989).
Conjeevaram, H. S. et al., Reversal of behavioral changes in rats subjected to portocaval shunt with oral neomycin therapy.
Hepatology
19:1245-1250 (1993).
Cooper, A. J. L., Ammonia metabolism in mammals: Interorgan relationships, in
Cirrhosis, Hyperammonemia, and Hepatic Encephalopathy,
Eds. Grisola, S., and Felipo, V., Plenum, N.Y. (1994).
Di Pierro, D. et al.,
Analytical Biochemistry
231:407-412 (1995).
Dugan, L. L. et al., Glia modulate the response of murine cortical neurons to excitotoxicity: Glia exacerbate AMPA neurotoxicity.
J. Neurosci.
15:4545-4555 (1995).
Hawkins, R. A. and Mans, A. M, Brain metabolism in hepatic encephalopathy and hyperammonemia, in
Cirrhosis, Hyperammonemia, and Hepatic Encephalopathy,
Grisola, S., and Felipo, V., Eds., Plenum, N.Y., pp. 13-19 (1994).
Kvamme, E. et al., Glutaminase from mammalian tissue.
Meth. Enzymol.
113:241-256 (1985).
Kerouel, R. and Aminot, A.,
Marine Chemistry
57:265-275 (1997).
Lo, E. H., Pierce, A. R., Matsumoto, K., Kano, T., Evans, C., Newcomb, R., Alterations in K+ evoked profiles of neurotransmitter and neuromodulator amino acids after focal ischemia-reperfusion.
Neuroscience
83:449-458 (1998).
Mousseau, D. D. and Butterworth, R. F., Current theories on the pathogenesis of hepatic encephalopathy.
Proc. Soc. Exp. Biol.
206(4):329-344 (1994).
Oppong, K. N. W. et al., Oral glutamine challenge in cirrhotics pre- and post-liver transplantation: A psychometric and analyzed EEG study.
Hepatology
26:870-876 (1997).
Seiler, N. et al., Enhanced endogenous ornithine concentrations protect against tonic seizures and coma in acute ammonia intoxication.
J. Pharmacol. Toxicol.
72:116-123 (1993).
Schousboe, A. et al., Preparation of primary cultures of mouse (rat) cerebellar granule cells, in
A Dissection and Tissue Culture Manual of the Nervous System,
Alan R. Liss, Inc., New York (1989).
Shapiro, R. A. et al., Covalent interaction of L-2-amino-4-oxo-5-chloropentanoic acid with rat renal phosphate-dependent glutaminase.
J. Biol. Chem.
253:7086-7090 (1978).
Shapiro, R. A. et al., Inactivation of rat renal phosphate-dependent glutaminase with 6-diazo-5-oxo-L-norleucine. Evidence for interaction at the glutamine binding site.
J. Biol. Chem.
254(8):2835-8 (1979).
Stauch, S. et al., Oral L-omithine-L-aspartate therapy of chronic hepatic encephalopathy: Results of a placebo-controlled double-blind study.
J. Hepatol.
28:856-864 (1998).
Wood, P., Roles of CNS macrophages in neurodegeneration, in
Neuroinflammation Mechanisms and Management,
Wood, P. L., Ed., Humana, Totowa, N.J., pp 1-59 (1997).
Zea Longa, E. et al., Reversible middle artery occlusion without craniectomy.
Stroke
20: 84-91 (1989).
BACKGROUND OF THE INVENTION
Glutaminase is currently recognized as the most significant glutamine utilizing enzyme present in mammalian central nervous tissue (e.g., the brain and spinal cord). The enzyme catalyzes the conversion of glutamine and water to glutamate, with the production of ammonia.
Following ischemic insult or other traumatic injury to neuronal cells, a number of biochemical changes occur in neuronal tissue surrounding the injured region, including a rise in the extracellular concentration of the excitatory neurotransmitter glutamate. This high concentration of glutamate is believed to be an important factor in delayed neuronal death, in which the ischemic lesion increases approximately 2-fold over a period of time 2-72 hours following the initial ischemic insult. It is believed that this elevated glutamate level exacerbates the primary insult, possibly by acting at excitatory glutamate receptors, and that at least some of the excess glutamate results from enzymatic conversion of glutamine to glutamate by glutaminase.
The maximal activity of glutaminase in the brain is 5-10 &mgr;mol/min/g (Alameida et al., 1989). This activity corresponds to a capacity for generating glutamate at a concentration of 5-10 mM each minute, a rate far in excess of the 5-10 &mgr;M IC
50
for toxicity of glutamate on isolated neurons (Dugan et al., 1995). Therefore, it is apparent that only a very minor fraction of the glutaminase present in the brain needs to be active in a pathological circumstance in order to cause damage. Accordingly, inhibition of glutaminase has been reported as a neuroprotective treatment following ischemic injury (see e.g. Newcomb, PCT Pubn. No. WO 99/09825).
Inhibition of glutaminase may also be used for treatment of hepatic encephalopathy. This condition can arise from chronic liver damage, such as chronic forms of viral hepatitis. Portal blood from the intestine is shunted around the damaged liver, entering the circulation directly. The resulting exposure of the brain to elevated concentrations of blood ammonia produces neurologic symptoms ranging from intellectual impairment and psychiatric symptoms to coma. Several million people are affected to some degree (Hawkins et al.). Current treatments are based on lowering blood ammonia, either by decreasing ammonia generation in the gut, e.g. by treatment with the antibiotic neomycin (Conjeevaram et al.), or by biochemical manipulation of ammonia excretion. For example, the efficacy of ammonia fixation by the urea cycle can be increased by increasing the concentration of ornithine, which is accomplished by inhibiting ornithine amino transferase with a compound such as 5-fluoromethylornithine (Seiler et al.). The use of L-ornithine-L-aspartate has also been reported (Stauch et al.). These treatments, while useful, suffer from toxicity (neomycin) or only partial effectiveness (ornithine compounds).
The role of glutaminase in regulation of blood ammonia is described in Cooper et al. and Oppong et al., and includes the hydrolysis of glutamine to glutamate and ammonia by glutaminase in the intestine. Thus, hepatic encephalopathy could be treated by selective inhibition of glutaminase in intestinal tissue.
To date, no glutaminase inhibitors have been reported that are both potent and specific for glutaminase. Known inhibitors, such as 6-diazo-5-oxo-L-norleucine (“DON”; Shapiro et al. 1979) and L-2-amino-4-oxo-5-chloropentanoic acid (“chloroketone”; Shapiro et al. 1978; see also Rosenberg, U.S. Pat. No. 5,156,976), also inhibit a variety of glutamine utilizing enzymes, such as amidotransferases (Ahluwahia et aL, 1990).
SUMMARY OF THE INVENTION
The present invention includes, in one aspect, a method of selectively inhibiting glutaminase in a cell or tissue, comprising administering to the cell or tissue an effective amount of a compound of formula I:
where
X is sulfur or oxygen, and R
1
and R
2
are independently selected from the group consisting of lower alkyl, lower alkoxy, aryl, and —(CH
2
)
n
-aryl, where n is 0 or 1, and “aryl” is a monocyclic aromatic or heteroaromatic group, having ring atoms selected from the group consisting of carbon, nitrogen, oxygen, and sulfur, and having at most three non-carbon ring atoms, which group may be unsubstituted or substituted with one or more substituents selected from halogen, lower alkyl, lower alkoxy, amino, lower alkyl amino, amino(lower alkyl), or halo(lower alkyl). R
1
and R
2
may be the same or different; for ease of preparation, R
1
and R
2
are the same.
Preferably, X is sulfur. In one embodiment, each of R
1
and R
2
is —(CH
2
)
n
-aryl as defined above. The aryl group may be carbocyclic,

Affiliated with

Also associated with

Rating

Selective inhibition of glutaminase by bis-thiadiazoles does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Selective inhibition of glutaminase by bis-thiadiazoles, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Selective inhibition of glutaminase by bis-thiadiazoles will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2850520