Determination of the Bioavailability of [14C]-Hexaminolevulinate Using Accelerator Mass Spectrometry After Intravesical Administration to Human Volunteers

Hexaminolevulinate (HAL) is a diagnostic agent that allows the visualization of tumor tissue in the bladder by fluorescence cystoscopy. It is administered intravesically via a catheter for 1 hour, followed by blue light bladder inspection to induce selective red tumor fluorescence. Hexaminolevulinate should ideally be confined to the bladder only, but it is likely that some absorption occurs during administration, and therefore the systemic bioavailability is of interest. The bioavailability of HAL was determined by intravesical and intravenous administration of [14C]-HAL hydrochloride to 8 human volunteers. To reduce the radiation dose as low as possible, the ultrasensitive analytical technique of accelerator mass spectrometry was used to measure [14C]-HAL. The bioavailability of [14C]-HAL after intravesical and intravenous administration was determined from the respective area under the curve based on total radioactivity and was determined to be 7% (range, 5%-10%; 90% confidence interval). The systemic absorption of [14C]-HAL after intravesical administration is low and supports previous clinical experience with HAL showing no systemic side effects.

Preliminary results of intraoperative photodynamic therapy with 5-aminolevulinic acid in dogs with prostate carcinoma

Six client-owned dogs with prostate carcinoma were treated with a combination of (1) partial subcapsular prostatectomy using an Nd:YAG laser, (2) intraoperative photodynamic therapy using a halogen broad band lamp after local administration of a photosensitiser, and (3) systemic treatment with meloxicam. Median survival time was 41days (range 10-68days), which compared negatively with previous reports of subtotal laser prostatectomy combined with topical interleukin-2 administration, and photodynamic therapy alone. Despite treatment, the disease progressed locally, causing signs of stranguria to recur, and in the form of distant metastases. The recurrence of clinical signs due to the primary tumour despite photodynamic therapy is probably largely explained by insufficient penetration of light into the tissue. Better results may be obtained using other light sources (e.g. laser) and alternative techniques of light delivery, such as fibres or catheters allowing interstitial diffusion of light.

Zilascorb(2H), a new reversible protein synthesis inhibitor: clinical study of an oral preparation

The new anti-cancer drug zilascorb(2H) has shown promising activity in preclinical models. Its putative mechanism of action is reversible protein synthesis inhibition and long-term treatment is required. As a clinical treatment modality, long-term daily zilascorb(2H) infusions, as used in previous studies, are not regarded feasible. Therefore, an oral formulation of the drug was developed, and pharmacokinetic profile, toxicity and antitumor activity of zilascorb(2H) tablets were studied. Thirteen patients with advanced solid cancer not amenable to established therapy, but with adequate performance status and organ functions, were included. The treatment was given as a daily i.v. zilascorb(2H) infusion for 5 days, followed by zilascorb(2H) tablets twice daily for 3 months. Blood and urine sampling was performed when estimated plasma steady-state level was reached for each formulation, respectively. Analyses of drug concentrations in plasma and urine were performed by high performance liquid chromatography. Zilascorb(2H) in tablet formulation had a bioavailability of 32%, was quickly absorbed and slowly eliminated. Concomitant use of the H2-blocker ranitidine possibly enhanced bioavailability. Zilascorb(2H) was well tolerated. Two patients experienced drug-related fever, disturbing the treatment schedule for one of them. Moderate nausea was reported. One objective response was obtained. The bioavailability of zilascorb(2H) tablets was satisfactory. The principle of oral administration of zilascorb(2H) is feasible for long-term treatment and the side effects are acceptable. The mechanisms of action and the very low toxicity of the drug makes it a candidate for combination with other anticancer agents.

Lysosomal sialidase deficiency: increased ganglioside content in autopsy tissues of a sialidosis patient

Organs obtained at autopsy from a patient with sialidosis were analyzed for 'bound' sialic acid and their ganglioside and neutral glycolipid patterns determined. The water-soluble bound sialic acid was increased between 10- and 17-fold in visceral organs, but only about 2-fold in the brain, when compared to normal controls. Lipid-bound sialic acid was increased up to 8-fold in visceral organs due to elevated amounts of gangliosides GM3, GD3 and probably GM4 and LM1, whereas the brain showed no deviation from controls. An alteration of the neutral glycolipid pattern was also observed. The results indicate an impaired catabolism of gangliosides in sialidosis in addition to that of sialyloligosaccharides and sialoglycoproteins.