Analysis of mutant Escherichia coli thymidylate synthases (EC 2.1.1.45) with various amino acids substituted for cysteine at position 146 revealed the cysteine to be involved in the binding of 2'-deoxyuridylate as well as initiating the catalytic process. The substitution of a serine or alanine residue at position 146 did not appreciably alter the binding affinity for 2'-deoxyuridylate but the serine mutant enzyme was less active by a factor of 5000, whereas the alanine mutant enzyme was catalytically inactive. In contrast, the substitution of a glycine or threonine at position 146 created inactive enzymes with higher 2'-deoxyuridylate dissociation constants. The dissociation constant values for 2'-deoxyuridylate were used to estimate the overall contribution of the side chain of the amino acid at position 146 to substrate binding. The results suggested that the side chains of cysteine, alanine, and serine make nonspecific but effective van der Waals contacts with 2'-deoxyuridylate, thereby contributing about 0.82 kcal.mol-1 (1 cal = 4.184 J) to the apparent binding energy of the substrate.

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These findings indicate that vinorelbine is well tolerated in men with hormone-refractory prostate cancer and produces durable clinical benefit as defined by improvement in pain index and performance status.

A dosage of 1 g of valacyclovir 3 times per day (TID) for 7 days has already been shown to be superior to an oral dosage of 800 mg acyclovir 5 times per day for 7 days in immunocompetent individuals. The objective of this study was to assess the safety and efficacy of an oral dosage of valacyclovir, 1 g TID versus 2 g TID, for the treatment of herpes zoster in immunocompromised patients > or =18 years of age. The oral dosage schedule of 2 g of valacyclovir TID reaches acyclovir plasma levels similar to those achieved with intravenous acyclovir therapy given to immunocompromised patients (10 mg/kg every 8 h for 7 days). In this double-blind study, 87 immunocompromised patients with clinical evidence of localized herpes zoster were randomized to receive oral valacyclovir therapy for 7 days, either 1 g TID or 2 g TID, within 72 h after onset of zoster rash. Patients were seen and assessed for cutaneous healing, zoster-associated pain (ZAP), and/or zoster-associated abnormal sensations (ZAAS), up to 24 weeks. Participants in both arms of the study demonstrated similar median times to full crusting of the rash (8 days), and both dosages were safe and effective therapies for reduction of ZAP and ZAAS in the immunocompromised patient population.