1. Thymidylate synthase inhibitors as anticancer agents:from bench to bedside
Edward Chu, Marc A. Callender, Michael P. Farrell, John C. Schmitz. Cancer Chemother Pharmacol (2003) 52 (Suppl 1): S80–S89
AG331 and AG337 are lipophilic, antifolate analogs that were designed speciﬁcally on the basis of the crystal structure of human TS. They enter cells via passive diﬀusion and are not dependent on the RFC or other speciﬁc transport systems to cross the cell membrane. Because their cellular half-lives are short, they must be administered via continuous infusion. AG331 was found to result in severe liver toxicity in phase I testing and further evaluation was subsequently terminated. AG337 was well tolerated in the initial phase I studies, and showed promising activity against head and neck, pancreatic, and hepatocellular cancer. A phase II trial of nolatrexed in patients with squamous cell cancer of the head and neck, administered as a continuous infusion over 5 days every 3 weeks with doses initiated at 1000 mg/m2, showed complete responses in 2 and partial responses in 2 of 22 patients to give an overall response rate of 18%. The most common adverse eﬀects included rash, mucositis, neutropenia, and thrombocytopenia; these toxicities are similar to those observed in the initial phase I studies. One drug-related neutropenic sepsis death occurred during the study. A phase II trial also showed activity in hepatocellular cancer, and as a result a large phase III randomized trial is currently ongoing in North America where patients with unresectable hepatocellular carcinoma are randomized to receive either nolatrexed or doxorubicin (the control arm).
2. Serine/threonine protein phosphatase inhibition enhances the effect of thymidylate synthase inhibition
Jennette A. Sakoﬀ, Ian J. Howitt, Stephen P. Ackland , Adam McCluskey. Cancer Chemother Pharmacol (2004) 53: 225–232
TS inhibition plays a pivotal role in anticancer treatment and is the ﬁrst-line treatment of many cancers particularly colorectal tumours. The quinazoline TS inhibitor, nolatrexed, was speciﬁcally chosen in this study over more conventional agents since it is a small molecular noncompetitive direct and speciﬁc inhibitor of TS, with no requirement for active membrane transport or intracellular activation. We have previously shown that nolatrexed induces S-phase cell cycle arrest, biphasic mitochondrial alterations and subsequent apoptotic cell death in various leukaemia cell lines. The lack of intermediate steps in the action of both cantharidin and nolatrexed enables the examination of the combined eﬀects of these drugs without the confounding eﬀect of interfering with the initial drug target interaction.
3. From methotrexate to pemetrexed and beyond.
A review of the pharmacodynamic and clinical properties of antifolates
Jackie Walling. Investigational New Drugs 24: 37–77, 2006.
Nolatrexed (AG337) is a TS inhibitor that was designed fromthe crystal structure of E. coli TS and X-ray analysis of ligands bound to the enzyme. It is a lipophilic, water-soluble molecule that is not a substrate for either the RFC or FPGS. The notion was that prolonged exposure would be required to achieve antitumor effect, since there would be no selective retention of the molecule intracellularly, but that would be compensated by the absence of prolonged toxicity. End product reversal experiments demonstrate that nolatrexed is a speciﬁc inhibitor of TS, with a Ki of 11 nM for binding to TS. As would be expected from knowledge of its structure the compound has rapid inﬂux and efﬂux and prolonged exposure is needed for cytotoxic activity. In vivo, nolatrexed has good activity and is curative in L5178Y TK- lymphoma.
4. Phase II trial of nolatrexed dihydrochloride [ThymitaqTM, AG 337] in patients with advanced hepatocellular carcinoma
Minaxi Jhawer • Lee Rosen • Janet Dancey. Invest New Drugs (2006) 25:85–94
Nolatrexed dihydrochloride (ThymitaqTM, AG337) was synthesized from a computer-assisted protein structure-based design of inhibitors using high-resolution, X-ray crystallography and molecular mechanics to analyze E. Coli TS structure. Nolatrexed is a non-competitive and high-afﬁnity inhibitor (Ki = 11 nM) of TS, and has shown activity against both rodent and human tumor-cell lines in vitro and against selected tumor models in vivo. It was initially developed by Agouron Pharmaceuticals, who in 1999, licensed worldwide rights to Zarix (now Eximias). In a phase I study with 23 evaluable patients, 6 patients with a variety of solid tumors experienced prolonged stable disease (SD) and one patient with colon cancer experienced a partial response (PR). Nolatrexed was fairly well tolerated, and myelosuppression and mucositis were the dose-limiting toxicities. Early phase II efﬁcacy studies, were initiated in a broad category of solid tumors including head and neck cancer, non-small cell lung cancer, hormone refractory prostate cancer, HCC and colorectal cancer.