Validation and development of MTH1 inhibitors for treatment of cancer.

BACKGROUND: Previously, we showed cancer cells rely on the MTH1 protein to prevent incorporation of otherwise deadly oxidised nucleotides into DNA and we developed MTH1 inhibitors which selectively kill cancer cells. Recently, several new and potent inhibitors of MTH1 were demonstrated to be non-toxic to cancer cells, challenging the utility of MTH1 inhibition as a target for cancer treatment. MATERIAL AND METHODS: Human cancer cell lines were exposed in vitro to MTH1 inhibitors or depleted of MTH1 by siRNA or shRNA. 8-oxodG was measured by immunostaining and modified comet assay. Thermal Proteome profiling, proteomics, cellular thermal shift assays, kinase and CEREP panel were used for target engagement, mode of action and selectivity investigations of MTH1 inhibitors. Effect of MTH1 inhibition on tumour growth was explored in BRAF V600E-mutated malignant melanoma patient derived xenograft and human colon cancer SW480 and HCT116 xenograft models. RESULTS: Here, we demonstrate that recently described MTH1 inhibitors, which fail to kill cancer cells, also fail to introduce the toxic oxidized nucleotides into DNA. We also describe a new MTH1 inhibitor TH1579, (Karonudib), an analogue of TH588, which is a potent, selective MTH1 inhibitor with good oral availability and demonstrates excellent pharmacokinetic and anti-cancer properties in vivo. CONCLUSION: We demonstrate that in order to kill cancer cells MTH1 inhibitors must also introduce oxidized nucleotides into DNA. Furthermore, we describe TH1579 as a best-in-class MTH1 inhibitor, which we expect to be useful in order to further validate the MTH1 inhibitor concept.

DNA binding, solubility, and partitioning characteristics of extended lexitropsins.

Four new ligands that bind to the minor groove of DNA have been designed, synthesized, and evaluated by DNA footprinting. Two of the ligands are polyamides containing central regions with five or six N-methylpyrrole units, conferring hydrophobicity and good binding affinity but without retaining the correct spacing for hydrogen bonding in the base of the minor groove. The two remaining ligands have central regions which are head-to-head-linked polyamides, in which the linker is designed to improve the phasing of hydrogen bonding of the ligand with the floor of the minor groove. The highest affinity was obtained with the two polypyrroles without headgroup spacers, indicating that H-bond phasing is secondary in determining affinity compared to the major hydrophobic driving force. With a dimethylaminoalkyl group, representing a moiety with modest base strength, at both ends, water solubility is good and pH-partition theory predicts that penetration through lipid membranes will be enhanced, compared to strongly basic amidine analogues of the alkaloid precursors. All four compounds bind to DNA, with strong selectivity for AT sequences but some tolerance of GC base pairs and subtle individual preferences. The data show that very high affinities can be anticipated for future compounds in this series, but drug design must take account of overall physicochemical properties as well as the details of hydrogen bonding between ligands and the floor of the minor groove.

Multiple solid-phase synthesis of hydantoins and thiohydantoins.

A novel general protocol for the construction of hydantoins and thiohydantoins on a solid support has been developed. Using this novel methodology, the synthesis of a diverse 96-compound library has been achieved. Resin-bound dipeptides are cyclised via the formation of an intermediate isocyanate or isothiocyanate on resin as the key step in the strategy.

Uptake and retention of nitroimidazole-carboranes designed for boron neutron capture therapy in experimental murine tumours: detection by 11B magnetic resonance spectroscopy.

Two novel nitroimidazole-carboranes were examined for their uptake and retention in two experimental murine solid tumours and in some normal tissues, using in vivo 11B magnetic resonance spectroscopy. The compounds were injected i.p. at 0.8mmol/kg into mice bearing either the SCCVII/Ha squamous cell carcinoma or KHT sarcoma implanted intradermally on the mouse back. Boron from a polyether-isoxazole linked nitroimidazole-carborane (compound 1) was detectable in both SCCVII/Ha and KHT tumours at 3 and 7 h after injection. The signal from the liver at these times was greater than that from the tumour but only a weak signal was obtained from the brain. At 24 h after injection the tumour signal was still present, as was that from the liver, which appeared to have increased over that for the earlier times. Signal from the brain had disappeared by 24 h. Boron from a polyether-carbamate linked nitroimidazole-carborane (compound 2) was also detectable in both tumours at all times tested, and again was present in the liver. In addition, the 11B signal was detectable from the mouse brain, at early times, but was undetectable at 24 h. These preliminary data indicate that nitroimidazole-carboranes are taken up and retained in experimental murine tumours in sufficient amounts to be detectable by in vivo 11B MRS and further that at 24 h after treatment there is differential retention between tumours and the brain.

Double--blind clinical trial of adenine arabinoside and idoxuridine in herpetic corneal ulcers.

The results are reported of a fully controlled randomized double-blind clincial trial of adenine arabinoside and idoxuridine ointment in sixty patients with herpetic ulceration of the cornea. Although both antivirals showed a trend towards superiority over placebo, the therapeutic effect did not reach statistical significance in spite of the known efficacy in laboratory animals. Further studies in rabbits are reported; these indicate that systemic immunity may play a role in combating virus proliferation in recurrent disease, and it is considered this disguises the efficacy of topical antiviral therapy in clinical trials, thus necessitating an estimated requirement for approximately fifty patients per treatment group to obtain significant effects. It is concluded that an antiviral is valuable in the treatment of ulcerative herpetic keratitis, particularly in primary disease and in the presence of systemic and local immunosuppression after the use of topical adrenocorticosteroid. In recurrent disease, where a trigger factor is known, experience has shown that therapy can be profitably administered before the onset of clinical disease.