Since accelerated metabolism produces much higher levels of reactive oxygen species (ROS) in cancer cells compared to ROS levels found in normal cells, human MutT homolog 1 (MTH1), which sanitizes oxidized nucleotide pools, was recently demonstrated to be crucial for the survival of cancer cells, but not required for the proliferation of normal cells. Therefore, dozens of MTH1 inhibitors have been developed with the aim of suppressing cancer growth by accumulating oxidative damage in cancer cells. While several inhibitors were indeed confirmed to be effective, some inhibitors failed to kill cancer cells, complicating MTH1 as a viable target for cancer eradication. In this review, we summarize the current status of developing MTH1 inhibitors as drug candidates, classify the MTH1 inhibitors based on their structures, and offer our perspectives toward the therapeutic potential against cancer through the targeting of MTH1.

Human immunodeficiency virus (HIV) is the primary infectious agent of acquired immunodeficiency syndrome (AIDS), and non-nucleoside reverse transcriptase inhibitors (NNRTIs) are the cornerstone of HIV treatment. In the last 20 years, our medicinal chemistry group has made great strides in developing several distinct novel NNRTIs, including 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT), thio-dihydro-alkoxy-benzyl-oxopyrimidine (-DABO), diaryltriazine (DATA), diarylpyrimidine (DAPY) analogues, and their hybrid derivatives. Application of integrated modern medicinal strategies, including structure-based drug design, fragment-based optimization, scaffold/fragment hopping, molecular/fragment hybridization, and bioisosterism, led to the development of several highly potent analogues for further evaluations. In this paper, we review the development of NNRTIs in the last two decades using the above optimization strategies, including their structure-activity relationships, molecular modeling, and their binding modes with HIV-1 reverse transcriptase (RT). Future directions and perspectives on the design and associated challenges are also discussed.

In order to improve the positional adaptability of our previously reported naphthyl diaryltriazines (NP-DATAs), synthesis of a series of novel biphenyl-substituted diaryltriazines (BP-DATAs) with a flexible side chain attached at the C-6 position is presented. These compounds exhibited excellent potency against wild-type (WT) HIV-1 with EC values ranging from 2.6 to 39 nmol/L and most of them showed low nanomolar anti-viral potency against a panel of HIV-1 mutant strains. Compounds and had the best activity against WT, single and double HIV-1 mutants and reverse transcriptase (RT) enzyme comparable to two reference drugs (EFV and ETR) and our lead compound NP-DATA (). Molecular modeling disclosed that the side chain at the C-6 position of DATAs occupied the entrance channel of the HIV-1 reverse transcriptase non-nucleoside binding pocket (NNIBP) attributing to the improved activity. The preliminary structure-activity relationship and PK profiles were also discussed.

Our recent studies for nonnucleoside reverse transcriptase inhibitors identified a highly potent compound JK-4b against WT HIV-1 (EC₅₀ = 1.0 nmol/L), but the poor metabolic stability in human liver microsomes (t _1/2 = 14.6 min) and insufficient selectivity (SI = 2059) with high cytotoxicity (CC₅₀ = 2.08 μmol/L) remained major issues associated with JK-4b. The present efforts were devoted to the introduction of fluorine into the biphenyl ring of JK-4b, leading to the discovery of a novel series of fluorine-substituted NH₂-biphenyl-diarylpyrimidines with noticeable inhibitory activity toward WT HIV-1 strain (EC₅₀ = 1.8-349 nmol/L). The best compound 5t in this collection (EC₅₀ = 1.8 nmol/L, CC₅₀ = 117 μmol/L) was 32-fold in selectivity (SI = 66,443) compared to JK-4b and showed remarkable potency toward clinically multiple mutant strains, such as L100I, K103N, E138K, and Y181C. The metabolic stability of 5t was also significantly improved (t _1/2 = 74.52 min), approximately 5-fold higher than JK-4b in human liver microsomes (t _1/2 = 14.6 min). Also, 5t possessed good stability in both human and monkey plasma. No significant in vitro inhibition effect toward CYP enzyme and hERG was observed. The single-dose acute toxicity test did not induce mice death or obvious pathological damage. These findings pave the way for further development of 5t as a drug candidate.