Novel N-substituted derivatives of acyclovir (1a) were synthesized and evaluated for their antiviral, antimetabolic, and antitumor cell properties in vitro. Monomethylation of 1a at positions 1, 7, and N-2 gave compounds 2-4, respectively. When positions 1 and N-2 were linked together by an isopropeno group, the tricyclic 9-[(2-hydroxyethoxy)methyl]-1,N-2-isopropenoguanine (5) was obtained. Compound 5 was then further methylated at positions N-2 and 7 to give 6 and 7, respectively. None of the new acyclovir derivatives showed any appreciable antimetabolic or antitumor cell activity. However, compounds 2 and 5 exhibited a marked antiherpetic activity. Their activity spectrum was similar to that of acyclovir, and their selectivity as inhibitors of herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) was at least as great as, if not greater than, that of acyclovir.
In this study, fully dense commercially pure titanium (CP Ti) parts were successfully fabricated by selective laser melting (SLM) using the same optimal laser energy density E p ¯ but with two different laser powers: high laser power E H ~250W and low laser power E L ~50W. It was found that at the same E p ¯ different laser powers led to different phase formation, microstructure, texture and mechanical properties of the selective laser melting fabricated (SLMed) CP Ti. A weak-textured CP Ti with isotropic mechanical properties was achieved using E H while a strong-textured CP Ti with anisotropic mechanical properties was obtained using E L . The underlying mechanism was attributed to the formation of α' phase in the CP Ti as a result of the higher cooling rates at E H . The formation of α' phase also contributed to the observed high ultimate compressive strength ~1.1GPa and high compressive strain ≥50% in the SLMed weak-textured CP Ti at E H . This study provides important insights into the role of laser energy in the SLM fabrication of CP Ti with tailorable crystallographic texture and thus mechanical properties.
Novel neplanocin A analogues modified at the 6'-position, i.e. 6'-deoxy derivatives (2, 3, 5, 6, 14), 6'-O-methylneplanocin A (10) and 6'-C-methylneplanocin A (16a and 16b) were synthesized and evaluated for their antiviral activity in a wide variety of virus systems. Compound 16a (TJ-13025) surpassed neplanocin A both in antiviral potency and selectivity.
<b>Introduction</b>: Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are essential components of highly active antiretroviral therapy against HIV-1 infections. Here, we provide a comprehensive overview of approved and emerging NNRTIs. <b>Areas covered</b>: This review covers the latest trend of NNRTIs regarding their pharmacodynamics, pharmacokinetics, mechanisms of drug action, drug resistance as well as new applications such as two-drug regimens and long-acting formulations. <b>Expert opinion</b>: Since the first NNRTI, nevirapine, was approved in 1996, antiviral drug discovery led to the approval of seven NNRTIs, including nevirapine, delavirdine (discontinued), etravirine, elsulfavirine, efavirenz, rilpivirine, and doravirine. The latter three compounds with favorable pharmacodynamic profiles and minimal adverse effects are often combined with one integrase inhibitor or two NRTIs in once-daily fixed-dose tablets. NNRTI-anchored regimens have been approved as initial therapies in treatment-naïve patients (efficacy: 72% to 86%) or maintaining therapies in virologically-suppressed patients (efficacy: 91% to 95%). Future development of NNRTIs includes: (i) better resistance and cross-resistance profiles; (ii) reduction of drug burden by optimizing two-drug or three-drug combinations; and (iii) improvement of patient adherence by novel long-acting formulations with weekly or monthly administration. Overall, NNRTIs play an important role in the management of HIV-1 infections, especially in resource-limited countries.
