Deuterium-substituted L-DOPA displays increased behavioral potency and dopamine output in an animal model of Parkinson's disease: comparison with the effects produced by L-DOPA and an MAO-B inhibitor.

The most effective treatment of Parkinson's disease (PD) L-DOPA is associated with major side effects, in particular L-DOPA-induced dyskinesia, which motivates development of new treatment strategies. We have previously shown that chronic treatment with a substantially lower dose of deuterium-substituted L-DOPA (D3-L-DOPA), compared with L-DOPA, produced equal anti-parkinsonian effect and reduced dyskinesia in 6-OHDA-lesioned rats. The advantageous effects of D3-L-DOPA are in all probability related to a reduced metabolism of deuterium dopamine by the enzyme monoamine oxidase (MAO). Therefore, a comparative neurochemical analysis was here performed studying the effects of D3-L-DOPA and L-DOPA on dopamine output and metabolism in 6-OHDA-lesioned animals using in vivo microdialysis. The effects produced by D3-L-DOPA and L-DOPA alone were additionally compared with those elicited when the drugs were combined with the MAO-B inhibitor selegiline, used in PD treatment. The different treatment combinations were first evaluated for motor activation; here the increased potency of D3-L-DOPA, as compared to that of L-DOPA, was confirmed and shown to be of equal magnitude as the effect produced by the combination of selegiline/L-DOPA. The extracellular levels of dopamine were also increased following both D3-L-DOPA and selegiline/L-DOPA administration compared with L-DOPA administration. The enhanced behavioral and neurochemical effects produced by D3-L-DOPA and the combination of selegiline/L-DOPA are attributed to decreased metabolism of released dopamine by MAO-B. The similar effect produced by D3-L-DOPA and selegiline/L-DOPA, respectively, is of considerable clinical interest since D3-L-DOPA, previously shown to exhibit a wider therapeutic window, in addition may reduce the need for adjuvant MAO-B inhibitor treatment.

Deuterium substitutions in the L-DOPA molecule improve its anti-akinetic potency without increasing dyskinesias.

Treatment of Parkinson's disease is complicated by a high incidence of L-DOPA-induced dyskinesias (LID). Strategies to prevent the development of LID aim at providing more stable dopaminergic stimulation. We have previously shown that deuterium substitutions in the L-DOPA molecule (D3-L-DOPA) yield dopamine that appears more resistant to enzymatic breakdown. We here investigated the effects of D3-L-DOPA on motor performance and development of dyskinesias in a rodent model of Parkinson's disease. Through acute experiments, monitoring rotational behavior, dose-effect curves were established for D3-L-DOPA and L-DOPA. The equipotent dose of D3-L-DOPA was estimated to be 60% of L-DOPA. Subsequently, animals were treated with either the equipotent dose of D3-L-DOPA (5 mg/kg), the equivalent dose of D3-L-DOPA (8 mg/kg), L-DOPA (8 mg/kg) or vehicle. The equivalent dose of D3-L-DOPA produced superior anti-akinetic effects compared to L-DOPA in the cylinder test (p<0.05), whereas the equipotent dose of D3-L-DOPA produced an anti-akinetic effect similar to L-DOPA. Dyskinesias developed to the same degree in the groups treated with equivalent doses of D3-L-DOPA and L-DOPA. The equipotent dose of D3-L-DOPA induced fewer dyskinesias than L-DOPA (p<0.05). In conclusion, our study provides evidence for improved potency and reduced side-effects of L-DOPA by deuterium substitutions in the molecule. These results are of clinical interest since the occurrence of LID is related to the total L-DOPA dose administered. D3-L-DOPA may thus represent a novel strategy to reduce the total dose requirement and yet achieve an effective control of parkinsonian symptoms.

Synergistic effects of deuterium oxide and gemcitabine in human pancreatic cancer cell lines.

PURPOSE: Pancreatic cancer still remains a treatment-refractory cancer. Standard therapy for metastatic cancer is gemcitabine (dFdC) chemotherapy. Since heavy water (deuterium oxide, D2O) was shown to be active in pancreatic cancer in vitro, we examined the simultaneous or sequential cytotoxic effects of D2O and dFdC in pancreatic cancer cell lines (AsPC-1, BxPC-3, and PANC-1). Moreover, we investigated the effect of D2O treatment on the colony formation of peripheral blood mononuclear cells (PBMNC) as well as the apoptosis inducing activity of D2O and dFdC and the regulation of tumor suppressor gene p21. RESULTS: Simultaneous incubation of human pancreatic carcinoma cells with D2O and dFdC led to a decrease of IC50 values of dFdC alone in all cell lines examined. Sequential application of D2O and dFdC caused synergistic effects. Treatment with 10-30% D2O did not show any significant inhibition effects on the colony formation of peripheral blood mononuclear cells (PBMNC), indicating limited adverse effects of D2O on bone marrow cells. Treatment with D2O in combination with dFdC significantly (p<0.05) increased the induction of apoptosis in PANC-1 and AsPC-1 cells and led to an overexpression of p21 tumor suppressor gene compared to incubation with dFdC alone. As the combination of D2O and dFdC might offer an additional option for the control of pancreatic cancer, this treatment should be investigated in a pancreas carcinoma animal model in order to scrutinize the in vitro data.

Changed phosphodiesterase selectivity and enhanced in vitro efficacy by selective deuteration of sildenafil.

In order to explore whether selective deuteration of sildenafil affects selectivity and efficacy of the drug, the inhibitory activity of sildenafil (1-[4-ethoxy-3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-5-yl)phenyl-sulfonyl] -4-methylpiperazine citrate, CAS 139755-83-2) and three deuterated sildenafil derivatives, D8-piperazine-sildenafil (BDD-10402), D3-methyl-D8-piperazine-sildenafil (BDD-10403) and D5-ethoxy-Sildenafil (BDD-10406) against phosphodiesterases 1-6 was compared. Furthermore, the relaxant effect of sildenafil and its deuterated derivatives in a contractility assay on rabbit corpus cavernosum strips from New Zealand rabbits was investigated. BDD-10406 exhibits a 2-fold higher selectivity for phosphodiesterase 5 versus phosphodiesterase 6 than sildenafil. BDD-10406 and sildenafil inhibited cGMP formation with IC50 values of 6 nmol/L and 9 nmol/L, respectively. The corresponding IC80 values for BDD-10406 and Sildenafil were 33 nmol/L and 40 nmol/L, respectively. Sildenafil, BDD-10402, BDD-10403 and BDD-10406 relaxed the rabbit corpus cavernosum strips in a dose-dependent manner with ED50 values of 245 nmol/L, 91 nmol/L, 121 nmol/L and 85 nmol/L, respectively. Deuteration of sildenafil on the ethoxy group (BDD-10406) leads to enhanced selectivity for phosphodiesterase 5 versus phosphodiesterase 6 and higher efficacy in vitro. This is the first example of a deuteration effect on the inhibitory activity of a reversible enzyme inhibitor.

Enhanced plasma concentration by selective deuteration of rofecoxib in rats.

The plasma concentrations of BDD-11602 (4-[4- (methanesulfonyl)phenyl]-3-(pentadeuterophenyl)-5H-furan-2-one), a rofecoxib derivative in which the positions 2',3;4',5' and 6' of the phenyl ring were deuterated, and rofecoxib (4-(4-methylsulfonylphenyl)-3-phenyl-5H-furan-2-one, CAS 162011-90-7) were compared in order to explore the effects of selective deuteration on the systemic availability. The COX-2 selectivity in vitro was also compared. Following oral gavage administration of 0.1, 1 or 10 mg/kg BDD-11602 to Sprague Dawley rats, AUCo-t, (area under the curve) and Cmax (maximum concentration) values were statistically significant higher than those of rofecoxib at the same doses. The overall increase in AUC0-t and Cmax for BDD-11602 over rofecoxib was 1.53-fold and 1.60-fold, respectively. BDD-11602 and rofecoxib inhibited COX-2-derived PGE(2) synthesis with IC50 values of 173 nmol/l and 169 nmol/l, respectively. IC50 values for inhibition of human platelet COX-1 were estimated to be above 1 micromol/l for both compounds. The substitution of hydrogen by deuterium on the positions 2: 3',4',5' and 6' in BDD-11602 leads to superior oral availability compared to the non-deuterated compound, whereas the COX-2 selectivity is not affected.

Effects of heavy water (D2O) on human pancreatic tumor cells.

BACKGROUND: Pancreatic cancer constitutes an entity which is difficult to treat and, therefore, mostly fatal. Since heavy water (deuterium oxide, D2O) was shown to be active in various cancer cell lines in vitro and in vivo, we now investigated its effects in human pancreatic tumor cells. MATERIALS AND METHODS: The cytotoxic effects of D2O were examined in three pancreatic cancer cell lines (AsPC-1, BxPC-3 and PANC-1). Induction of apoptosis was determined by Hoechst/propidium iodide double staining and cell cycle distribution was investigated by FACS analysis. RESULTS: Employing a clonogenic assay, D2O yielded IC50 values of 15%, 18% and 27% in AsPC-1, PANC-1 and BxPC-3 cells, respectively, and led to the induction of apoptosis when compared to untreated controls. Moreover, D2O caused a cell cycle arrest in the G2-M-phase (BxPC-3, PANC-1) or in the S-phase (AsPC-1). CONCLUSION: It is hoped that D2O might offer an additional option for the treatment of pancreatic carcinomas.