Effect of regulation reform on clinical trials for registering novel therapeutic agents in Taiwan: a chronological analysis.

The registration process for new drugs is crucial in the clinical application of medicines. Previously, the registration of imported novel therapeutic agents in Taiwan depended considerably on their approvals in developed countries. The Taiwanese government enacted Article 38-1 of the Regulations for Registration of Medicinal Products in September 2009. According to the new submission criteria, approvals may be exempted if the number of Taiwanese participants in the clinical trials fulfills the required threshold. The present study compared the profiles of clinical trials of novel therapeutic agents before and after the enactment of this regulation in terms of over-threshold trials, structural types, and therapeutic areas across phases. The outcome-whether the liberalization of the submission criteria functioned as an incentive to launch clinical trials in Taiwan-was also evaluated. The results revealed that the number of clinical trial applications increased after the reformed regulation was enacted, even after the over-threshold criteria were considered; however, the increase disappeared for phase III trials. Most clinical trials were for chemical products and antineoplastic agents across all phases and study periods before and after the enactment of Article 38-1. Furthermore, the increase in the number of international clinical trials conducted in Taiwan was not directly caused by the regulation reform because the percentage of investigational products fulfilling the exemption criteria did not increase. These paradoxical results were interpreted in several aspects, referring particularly to the well-established infrastructure for launching clinical trials as well as the integral environment of medical services in Taiwan.

Inter-allelic prion propagation reveals conformational relationships among a multitude of [PSI] strains.

Immense diversity of prion strains is observed, but its underlying mechanism is less clear. Three [PSI] prion strains--named VH, VK, and VL--were previously isolated in the wild-type yeast genetic background. Here we report the generation and characterization of eight new [PSI] isolates, obtained by propagating the wild-type strains with Sup35 proteins containing single amino-acid alterations. The VH strain splits into two distinct strains when propagated in each of the three genetic backgrounds, harboring respectively single mutations of N21L, R28P, and Gi47 (i.e. insertion of a glycine residue at position 47) on the Sup35 N-terminal prion-forming segment. The six new strains exhibit complex inter-conversion patterns, and one of them continuously mutates into another. However, when they are introduced back into the wild-type background, all 6 strains revert to the VH strain. We obtain two more [PSI] isolates by propagating VK and VL with the Gi47 and N21L backgrounds, respectively. The two isolates do not transmit to other mutant backgrounds but revert to their parental strains in the wild-type background. Our data indicate that a large number of [PSI] strains can be built on three basic Sup35 amyloid structures. It is proposed that the three basic structures differ by chain folding topologies, and sub-strains with the same topology differ in distinct ways by local structural adjustments. This "large number of variations on a small number of basic themes" may also be operative in generating strain diversities in other prion elements. It thus suggests a possible general scheme to classify a multitude of prion strains.