Development of a biomarker to monitor target engagement after treatment with dihydroorotate dehydrogenase inhibitors

Dihydroorotate dehydrogenase (DHODH) catalyzes a key step in pyrimidine biosynthesis and has recently been validated as a therapeutic target for malaria through clinical studies on the triazolopyrimidine-based Plasmodium DHODH inhibitor DSM265. Selective toxicity towards Plasmodium species could be achieved because malaria parasites lack pyrimidine salvage pathways, and DSM265 selectively inhibits Plasmodium DHODH over the human enzyme. However, while DSM265 does not inhibit human DHODH, it inhibits DHODH from several preclinical species, including mice, suggesting that toxicity could result from on-target DHODH inhibition in those species. We describe here the use of dihydroorotate (DHO) as a biomarker of DHODH inhibition. Treatment of mammalian cells with DSM265 or the mammalian DHODH inhibitor teriflunomide led to increases in DHO where the extent of biomarker buildup correlated with both dose and inhibitor potency on DHODH. Treatment of mice with leflunomide (teriflunomide prodrug) caused a large dose-dependent buildup of DHO in blood (up to 16-fold) and urine (up to 5,400-fold) that was not observed for mice treated with DSM265. Unbound plasma teriflunomide levels reached 20-85-fold above the mouse DHODH IC50, while free DSM265 levels were only 1.6-4.2-fold above, barely achieving ∼ IC90 concentrations, suggesting that unbound DSM265 plasma levels are not sufficient to block the pathway in vivo. Thus, any toxicity associated with DSM265 treatment in mice is likely caused by off-target mechanisms. The identification of a robust biomarker for mammalian DHODH inhibition represents an important advance to generally monitor for on-target effects in preclinical and clinical applications of DHODH inhibitors used to treat human disease.

Regional amyloid correlates of cognitive performance in ageing and mild cognitive impairment

Beta-amyloid deposition is one of the earliest pathological markers associated with Alzheimer's disease. Mild cognitive impairment in the setting of beta-amyloid deposition is considered to represent a preclinical manifestation of Alzheimer's disease. In vivo imaging studies are unique in their potential to advance our understanding of the role of beta-amyloid deposition in cognitive deficits in Alzheimer's disease and in mild cognitive impairment. Previous work has shown an association between global cortical measures of beta-amyloid deposition ('amyloid positivity') in mild cognitive impairment with greater cognitive deficits and greater risk of progression to Alzheimer's disease. The focus of the present study was to examine the relationship between the regional distribution of beta-amyloid deposition and specific cognitive deficits in people with mild cognitive impairment and cognitively normal elderly individuals. Forty-seven participants with multi-domain, amnestic mild cognitive impairment (43% female, aged 57-82 years) and 37 healthy, cognitively normal comparison subjects (42% female, aged 55-82 years) underwent clinical and neuropsychological assessments and high-resolution positron emission tomography with the radiotracer 11C-labelled Pittsburgh compound B to measure beta-amyloid deposition. Brain-behaviour partial least-squares analysis was conducted to identify spatial patterns of beta-amyloid deposition that correlated with the performance on neuropsychological assessments. Partial least-squares analysis identified a single significant (P < 0.001) latent variable which accounted for 80% of the covariance between demographic and cognitive measures and beta-amyloid deposition. Performance in immediate verbal recall (R = -0.46 ± 0.07, P < 0.001), delayed verbal recall (R = -0.39 ± 0.09, P < 0.001), immediate visual-spatial recall (R = -0.39 ± 0.08, P < 0.001), delayed visual-spatial recall (R = -0.45 ± 0.08, P < 0.001) and semantic fluency (R = -0.33 ± 0.11, P = 0.002) but not phonemic fluency (R = -0.05 ± 0.12, P < 0.705) negatively covaried with beta-amyloid deposition in the identified regions. Partial least-squares analysis of the same cognitive measures with grey matter volumes showed similar associations in overlapping brain regions. These findings suggest that the regional distribution of beta-amyloid deposition and grey matter volumetric decreases is associated with deficits in executive function and memory in mild cognitive impairment. Longitudinal analysis of these relationships may advance our understanding of the role of beta-amyloid deposition in relation to grey matter volumetric decreases in cognitive decline.

Metabolism, uptake, and excretion of a D-glucaric acid salt and its potential use in cancer prevention

D-Glucaric acid (GA) is a nontoxic, natural compound. One of its derivatives is the potent beta-glucuronidase inhibitor D-glucaro-1,4-lactone (1,4-GL). The goal of this study was to demonstrate the in vivo formation of 1,4-GL from a D-glucarate salt and determine its metabolism, uptake by selected organs, and excretion following oral administration of potassium hydrogen D-[14C]glucarate to male and female Sprague-Dawley rats. 1,4-GL increases detoxification of carcinogens and tumor promoters/progressors by inhibiting beta-glucuronidase and preventing hydrolysis of their glucuronides. 1,4-GL and its precursors, such as potassium hydrogen D-glucarate and calcium D-glucarate, may exert their anticancer action, in part, through alterations in steroidogenesis accompanied by changes in the hormonal environment and the proliferative status of the target organ. Thus, GA derivatives may be useful as new or adjuvant cancer preventive and therapeutic agents. In our study, 1,4-GL was found to be formed from the D-glucarate salt in the stomach of rats. It was apparently absorbed from the gastrointestinal tract, transported with the blood to different internal organs, and excreted in the urine and to a lesser extent in bile. There were no significant differences in the metabolism of PHG between male and female rats. Thus, formation of 1,4-GL from D-glucaric acid derivatives may be prerequisite for their inhibition of chemical carcinogenesis in rodents and prevention of breast, prostate, and colon cancer in humans.

The efficacy of L-tryptophan in the reduction of sleep disturbance and depressive state in alcoholic patients

Alcoholic male inpatients (N = 76) served as subjects in this study which examined the effect of L-tryptophan on depressive state and sleep disturbance. All subjects were residents of a 6-week alcohol treatment program at a Veterans Administration Medical Center. Subjects' degree of depression (Zung's Depression Scale) and sleep satisfaction (Webb's Post-Sleep Inventory) were measured four times during the study, just prior to and following ingestion of a substance that was either 3 gms L-tryptophan or 3 gms of an identical-appearing placebo. Subjects in the L-tryptophan/placebo condition received the active substance for 4 days followed by the placebo with a 4-day washout period in between. A second group of subjects received the same regimen of reverse order and a third received placebos on both occasions. There were two additional control groups that received no substances. All subjects in the study reported decreased levels of depression due to nonspecific treatment effects. The subjects who took L-tryptophan in either sequence reported even lower levels of depression. Sleep disturbance was not affected by L-tryptophan since it was barely present when the study began. A phenomenon referred to as the interval effect is discussed and an alternative explanation for this effect is offered.

Drownings of children and youth in a desert state

Despite the fact that New Mexico is a desert state, the drowning rate (4.3) is 40% higher than that nationally (3.0). More than half of those who drown are younger than 25 years, toddlers and adolescents being at greater risk than other age groups. In an epidemiologic study of a six-year period, male drowning victims outnumbered female and American Indian and Hispanic victims outnumbered whites. Other major risk factors were epilepsy, mental retardation and alcohol abuse. In most drownings in the under-25 age group, the victim was involved in recreation near the water or swimming, although many were partially or fully clothed. Most drownings occurred in lakes, ditches or rivers. Because New Mexico is not a water-oriented state, public awareness of drowning hazards needs to be increased and more intensive preventive efforts instituted.

Aggressive approach to the extremity damaged by electric current

Electrical current injuries involving the extremities occurred in 41 of 75 patients with electrical burns admitted to the Oregon Burn Center over an 11 year period. Based solely on physical findings, the muscle compartments of 27 limbs in 14 patients were promptly explored, decompressed, and debrided of necrotic tissue on admission. This resulted in the salvage of 10 useful extremities. Major amputation of 11 extremities was carried out during initial surgery. No extremity needing exploration was overlooked. After exploration and fasciotomy, exposed tissues were protected with biologic dressings until repeated explorations and debridements demonstrated the absence of necrotic tissues and closure could be accomplished. The use of both local and free flaps was helpful in closing the wounds. No evidence or renal failure and no deaths attributable to retained necrotic tissue occurred.

Essential thrombocythemia and coronary artery disease

An unusual case of essential thrombocythemia in a young man presenting with progressive angina pectoris is presented. Angiography revealed proximal left anterior descending artery stenosis. Successful percutaneous transluminal angioplasty along with antiplatelet therapy and a calcium channel blocking drug have rendered this patient asymptomatic.